U.S. patent application number 14/414668 was filed with the patent office on 2015-07-30 for multifunctional repellent materials.
The applicant listed for this patent is President and Fellows of Harvard College. Invention is credited to Joanna Aizenberg, Michael Aizenberg, Benjamin Hatton, Philseok Kim, Cicely Shillingford, Steffi Sunny, Stefanie Utech, Oktay Uzun, Nicolas Vogel, Tak Sing Wong.
Application Number | 20150210951 14/414668 |
Document ID | / |
Family ID | 48808558 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150210951 |
Kind Code |
A1 |
Aizenberg; Joanna ; et
al. |
July 30, 2015 |
MULTIFUNCTIONAL REPELLENT MATERIALS
Abstract
Methods and compositions disclosed herein relate to liquid
repellant surfaces having selective wetting and transport
properties. An article having a repellant surface includes a
substrate comprising fabric material and a lubricant wetting and
adhering to the fabric material to form a stabilized liquid
overlayer, wherein the stabilized liquid overlayer covers the
fabric material at a thickness sufficient to form a liquid upper
surface above the fabric material, wherein the fabric material is
chemically functionalized to enhance chemical affinity with the
lubricant such that the lubricant is substantially immobilized on
the fabric material to form a repellant surface.
Inventors: |
Aizenberg; Joanna; (Boston,
MA) ; Aizenberg; Michael; (Boston, MA) ; Wong;
Tak Sing; (State College, PA) ; Vogel; Nicolas;
(Cambridge, MA) ; Shillingford; Cicely; (Waterloo,
CA) ; Kim; Philseok; (Arlington, MA) ; Hatton;
Benjamin; (Toronto, CA) ; Utech; Stefanie;
(Cambridge, MA) ; Uzun; Oktay; (Boston, MA)
; Sunny; Steffi; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
President and Fellows of Harvard College |
Cambridge |
MA |
US |
|
|
Family ID: |
48808558 |
Appl. No.: |
14/414668 |
Filed: |
July 12, 2013 |
PCT Filed: |
July 12, 2013 |
PCT NO: |
PCT/US2013/050403 |
371 Date: |
January 13, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61673705 |
Jul 19, 2012 |
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61671442 |
Jul 13, 2012 |
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61671645 |
Jul 13, 2012 |
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Current U.S.
Class: |
508/107 ; 141/1;
206/524.3; 427/301 |
Current CPC
Class: |
Y10T 428/24997 20150401;
C10N 2080/00 20130101; C10M 177/00 20130101; C23C 18/1216 20130101;
C10M 2213/0606 20130101; B05D 5/08 20130101; C23C 18/1254 20130101;
B05D 3/104 20130101; C03C 17/001 20130101; B08B 17/06 20130101;
B65D 25/14 20130101; B05D 5/086 20130101; C03C 2218/31 20130101;
C03C 2217/76 20130101; C23C 18/04 20130101; C09D 5/1693 20130101;
C10M 105/76 20130101; C23C 18/1295 20130101 |
International
Class: |
C10M 105/76 20060101
C10M105/76; B05D 5/08 20060101 B05D005/08; B65D 25/14 20060101
B65D025/14; C03C 17/00 20060101 C03C017/00; B08B 17/06 20060101
B08B017/06 |
Goverment Interests
STATEMENT CONCERNING GOVERNMENT RIGHTS IN FEDERALLY-SPONSORED
RESEARCH
[0006] This invention was made with government support under
FA9550-09-1-0669-DOD35CAP awarded by the U.S. Air Force and under
DE-AR0000326 awarded by the U.S. Department of Energy. The
government has certain rights in the invention.
Claims
1. An article having a repellant surface, the article comprising: a
substrate comprising fabric material having a weave density that is
greater than 100 threads/cm.sup.2; and a lubricant wetting and
adhering to the fabric material to form a stabilized liquid
overlayer, wherein the stabilized liquid overlayer covers the
fabric material at a thickness sufficient to form a liquid upper
surface above the fabric material, wherein the fabric material is
functionalized to enhance chemical affinity with the lubricant such
that the lubricant is substantially immobilized over the fabric
material to form a repellant surface.
2. An article having a repellant inner surface, the article
comprising: a container comprising an inner surface to contain a
complex fluid; a complex fluid having a liquid and one or more
other components within said container; and wherein said liquid
wets and adheres to the inner surface to form a stabilized liquid
overlayer, wherein the stabilized liquid overlayer covers the inner
surface at a thickness sufficient to form a liquid surface on the
inner surface, wherein the inner surface and the liquid have an
affinity such that the liquid is substantially immobilized on the
inner substrate to form a repellant surface, the repellant surface
repelling other components within said complex fluid.
3. An optical article having a repellant surface, the optical
article comprising: a substrate comprising transparent or
translucent material with a surface; a housing that holds the
substrate; and a lubricant wetting and adhering to the surface to
form a stabilized liquid overlayer, wherein the stabilized liquid
overlayer covers the surface at a thickness sufficient to form a
liquid upper surface above the surface, wherein the surface and the
lubricant have an affinity for each other such that the lubricant
is substantially immobilized on the substrate to form a repellant
surface, wherein the housing is infiltrated with the lubricant to
replenish the lubricant onto the substrate.
4. A membrane-like article, the article comprising: a membrane
substrate comprising a top surface, a bottom surface, and a
plurality of through-holes; a low-surface tension fluid wetting and
adhering the top surface, the bottom surface, and inner walls
surrounding the plurality of through-holes, forming a
pre-conditioning layer; and a fluid deposited over the
pre-conditioning layer to form a protective layer, the protective
laying providing a repellant surface to the membrane substrate;
wherein the membrane substrate, the pre-conditioning layer, and the
protective layer have an affinity to each other such that the
protective layer is substantially immobilized on the membrane
substrate to form the repellant surface.
5. An article for carrying fluid flow, the article comprising: a
substrate comprising a roughened surface; and a lubricant wetting
and adhering to the roughened surface to form a stabilized liquid
overlayer, wherein the stabilized liquid overlayer covers the
roughened surface at a thickness sufficient to form a liquid upper
surface on top of the roughened surface, wherein the roughened
surface and the lubricant have an affinity for each other such that
the lubricant is substantially immobilized on the substrate to form
a slippery surface, the slippery surface reducing drag and friction
of the fluid flow.
6. A method for protecting metal or metalized surfaces from
corrosion, the method comprising: providing a metal or metalized
surface; introducing roughness; and chemically functionalizing the
metal or metalized surface to enhance affinity of the metal surface
with a lubricant; and introducing the lubricant to wet and adhere
to the metal or metalized surface to form an overlayer; wherein the
metal or metalized surface and the lubricant have an affinity for
each other such that the lubricant is substantially immobilized on
the substrate to form a repellant surface, providing anti-corrosion
to the metal or metalized surface.
7. A method for protecting surfaces from scaling, the method
comprising: providing a surface; introducing roughness; and
chemically functionalizing the surface to enhance affinity of the
surface with a lubricant; and introducing the lubricant to wet and
adhere to the surface to form an overlayer; wherein the surface and
the lubricant have an affinity for each other such that the
lubricant is substantially immobilized on the substrate to form a
repellant surface, providing anti-scaling to the metal surface.
8. An article having a repellant surface, the article comprising: a
substrate comprising a roughened surface; a lubricant wetting and
adhering to the roughened surface to form a stabilized liquid
overlayer, wherein the liquid covers the roughened surface at a
thickness sufficient to form a liquid upper surface above the
roughened surface; and a fragrance enhancer located within said
substrate and/or said lubricant; wherein the roughened surface and
the lubricating liquid have an affinity for each other such that
the lubricating liquid is substantially immobilized on the
substrate to form a repellant surface.
9. An article having a repellant surface, the article comprising: a
substrate comprising a plurality of nanostructures embedded in a
medium and having a roughened surface; and a lubricant wetting and
adhering to the roughened surface to form a stabilized liquid
overlayer, wherein the liquid covers the roughened surface at a
thickness sufficient to form a liquid upper surface above the
roughened surface, wherein the roughened surface and the
lubricating liquid have an affinity for each other such that the
lubricating liquid is substantially immobilized on the substrate to
form a repellant surface, wherein the roughened surface includes a
microscale or nanoscale structure.
10. A method for protecting plastic, glass, ceramic, and composite
surfaces from graffiti, the method comprising: providing a said
solid surface; introducing roughness, chemically functionalizing
the said surface to enhance affinity of the said surface with a
lubricant; and introducing the lubricant to wet and adhere to the
said surface to form an overlayer, wherein the said surface and the
lubricant have an affinity for each other such that the lubricant
is substantially immobilized on the substrate to form a repellant
surface, providing anti-graffiti properties to the said
surface.
11. A method for fluid collection, the method comprising: providing
a solid surface; introducing roughness; chemically functionalizing
the solid surface to enhance affinity of the surface with a
lubricant; introducing the lubricant to wet and adhere to the solid
surface to form an overlayer, wherein the solid surface and the
lubricant have an affinity for each other such that the lubricant
is substantially immobilized on the substrate to form a repellant
surface; condensing condensate droplets on the repellant surface
for liquid collection; and receiving and recovering fluids
dispensed in excess in a coating or processing equipment.
12. An article having a repellant surface, the article comprising:
a substrate comprising a roughened surface; and a lubricant wetting
and adhering to the roughened surface to form a stabilized liquid
overlayer, wherein the liquid covers the roughened surface at a
thickness sufficient to form a liquid upper surface above the
roughened surface, wherein the roughened surface and the
lubricating liquid have an affinity for each other such that the
lubricating liquid is substantially immobilized on the substrate to
form a repellant surface, wherein the substrate is a component of a
ski, a luge, a surf board, a hovercraft, a winter sports item, or a
water sports item, wherein the repellent surface is capable of
repelling solid materials, fluid materials, or combinations
thereof.
13. A method for protecting plastic, glass, ceramic, and composite
surfaces from scaling, the method comprising: providing a said
solid surface; introducing roughness: chemically functionalizing
the said surface to enhance affinity of the said surface with a
lubricant; and introducing the lubricant to wet and adhere to the
said surface to form an overlayer, wherein the surface and the
lubricant have an affinity for each other such that the lubricant
is substantially immobilized on the substrate to form a repellant
surface, providing anti-scaling to the said surface.
14. A method for forming a repellent surface, the method
comprising: providing a substrate having a surface; depositing a
first material having a charge to said surface; depositing a second
material having a charge that is opposite to the charge of the
first material; sequentially repeating said depositing a first
material and said depositing a second material to provide a
roughened surface; introducing a lubricant to wet and adhere to
said roughened surface to form an overlayer, wherein said roughened
surface and said lubricant have an affinity for each other such
that the lubricant is substantially immobilized on the substrate to
form a repellent surface.
15. The method of claim 14, further comprising removing said first
material or said second material after said sequentially repeating
said depositing a first material and said depositing a second
material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The application claims the benefit of the earlier filing
date of U.S. Patent Application No. 61/671,442, filed on Jul. 13,
2012; U.S. Patent Application No. 61/671,645, filed on Jul. 13,
2012; and U.S. Patent Application No. 61/673,705, filed on Jul. 19,
2012, the contents of which are incorporated by reference herein in
their entireties.
[0002] The present application related to the following co-pending
applications filed on even date herewith:
[0003] International Application entitled SELECTIVE WETTING AND
TRANSPORT SURFACES, filed on even date herewith;
[0004] International Application entitled SLIPS SURFACE BASED ON
METAL-CONTAINING COMPOUND, filed on even date herewith:
[0005] International Application entitled MULTIFUNCTIONAL REPELLENT
MATERIALS, filed on even date herewith;
the contents of which are incorporated by reference herein in their
entireties.
TECHNICAL FIELD
[0007] The field of this application generally relates to slippery
surfaces, methods for forming them, and their uses.
BACKGROUND
[0008] Current development of liquid-repellent surfaces is inspired
by the self-cleaning abilities of many natural surfaces on animals,
insects, and plants. Water droplets on these natural surfaces roll
off or slide off easily, carrying the dirt or insects away with
them. The presence of the micro/nanostructures on many of these
natural surfaces has been attributed to the water-repellency
function. These observations have led to enormous interests in
manufacturing biomimetic water-repellent surfaces in the past
decade, owing to their broad spectrum of potential applications,
ranging from water-repellent fabrics to friction-reduction
surfaces.
SUMMARY
[0009] Liquid repellant surfaces having selective wetting and
transport properties and their applications in a variety of fields
are described. In certain embodiments, such liquid repellant
surfaces have additional functionalities, in addition to the
wetting and transport properties.
[0010] Disclosed subject matter includes, in one aspect, an article
having a repellant surface, which includes a substrate comprising
fabric material having a weave density that is greater than 100
threads/cm.sup.2 and a lubricant wetting and adhering to the fabric
material to form a stabilized liquid overlayer, wherein the
stabilized liquid overlayer covers the fabric material at a
thickness sufficient to form a liquid upper surface above the
fabric material, wherein the fabric material is chemically
functionalized to enhance chemical affinity with the lubricant such
that the lubricant is substantially immobilized over the fabric
material to form a repellant surface.
[0011] Disclosed subject matter includes, in another aspect, an
optical article having a repellant surface, which includes a
substrate comprising transparent or translucent material with a
surface, a housing that holds the substrate, and a lubricant
wetting and adhering to the surface to form a stabilized liquid
overlayer, wherein the stabilized liquid overlayer covers the
surface at a thickness sufficient to form a liquid upper surface
above the surface, wherein the surface and the lubricant have an
affinity for each other such that the lubricant is substantially
immobilized on the substrate to form a repellant surface, wherein
the housing is infiltrated with the lubricant to replenish the
lubricant onto the substrate.
[0012] Disclosed subject matter includes, in another aspect, an
article having a repellant inner surface, which includes a
container comprising an inner surface to contain a complex fluid;
and a complex fluid having a liquid and one or more other
components within said container; wherein the liquid wets and
adheres to the inner surface to form a stabilized liquid overlayer,
wherein the stabilized liquid overlayer covers the inner surface at
a thickness sufficient to form a liquid surface on the inner
surface, wherein the inner surface and the liquid have an affinity
such that the liquid is substantially immobilized on the inner
substrate to form a repellant surface, the repellant surface
repelling other components within said complex fluid.
[0013] Disclosed subject matter includes, in another aspect, a
membrane-like article, which includes a membrane substrate
comprising a top surface, a bottom surface, and a plurality of
through-holes and a low-surface tension fluid wetting and adhering
the top surface, the bottom surface, and inner walls surrounding
the plurality of through-holes, forming a pre-conditioning layer
and a fluid deposited over the pre-conditioning layer to form a
protective layer, the protective laying providing a repellant
surface to the membrane substrate, wherein the membrane substrate,
the pre-conditioning layer, and the protective layer have an
affinity to each other such that the protective layer is
substantially immobilized on the membrane substrate to form the
repellant surface.
[0014] Disclosed subject matter includes, in another aspect, an
article for carrying fluid flow, which includes a substrate
comprising a roughened surface and a lubricant wetting and adhering
to the roughened surface to form a stabilized liquid overlayer,
wherein the stabilized liquid overlayer covers the roughened
surface at a thickness sufficient to form a liquid upper surface on
top of the roughened surface, wherein the roughened surface and the
lubricant have an affinity for each other such that the lubricant
is substantially immobilized on the substrate to form a slippery
surface, the slippery surface reducing drag and friction of the
fluid flow.
[0015] Disclosed subject matter includes, in another aspect, a
method for protecting metal or metalized surfaces from corrosion,
which includes providing a metal or metalized surface, introducing
roughness, and chemically functionalizing the metal or metalized
surface to enhance affinity of the metal surface with a lubricant
and introducing the lubricant to wet and adhere to the metal or
metalized surface to form an overlayer, wherein the metal or
metalized surface and the lubricant have an affinity for each other
such that the lubricant is substantially immobilized on the
substrate to form a repellant surface, providing anti-corrosion to
the metal or metalized surface.
[0016] Disclosed subject matter includes, in another aspect, a
method for protecting surfaces from scaling, which includes
providing a surface, introducing roughness, and chemically
functionalizing the surface to enhance affinity of the surface with
a lubricant, and introducing the lubricant to wet and adhere to the
surface to form an overlayer, wherein the surface and the lubricant
have an affinity for each other such that the lubricant is
substantially immobilized on the substrate to form a repellant
surface, providing anti-scaling to the metal surface.
[0017] Disclosed subject matter includes, in another aspect, an
article having a repellant surface, which includes a substrate
comprising a roughened surface; a lubricant wetting and adhering to
the roughened surface to form a stabilized liquid overlayer,
wherein the liquid covers the roughened surface at a thickness
sufficient to form a liquid upper surface above the roughened
surface; and a fragrance enhancer located within said substrate
and/or said lubricant; wherein the roughened surface and the
lubricating liquid have an affinity for each other such that the
lubricating liquid is substantially immobilized on the substrate to
form a repellant surface.
[0018] In certain embodiments, the roughened surface and/or the
liquid possess more than one chemical state that can be switched to
enhance or diminish the affinity between the surface and the
lubricating liquid.
[0019] Disclosed subject matter includes, in another aspect, an
article having a repellant surface, which includes a substrate
comprising a roughened surface and a lubricant wetting and adhering
to the roughened surface to form a stabilized liquid overlayer,
wherein the liquid covers the roughened surface at a thickness
sufficient to form a liquid upper surface above the roughened
surface, wherein the roughened surface and the lubricating liquid
have an affinity for each other such that the lubricating liquid is
substantially immobilized on the substrate to form a repellant
surface, wherein the roughened surface includes a microscale or
nanoscale structure.
[0020] In certain embodiments, the substrate includes a plurality
of nanofibers or nanotubes embedded in an epoxy medium.
[0021] Disclosed subject matter includes, in another aspect, an
article having a repellant surface, which includes a substrate
comprising an at least partially roughened surface and a lubricant
wetting and adhering to the roughened surface to form a kinetically
stabilized liquid overlayer, wherein the liquid covers the
roughened surface at a thickness sufficient to form a liquid upper
surface above the roughened surface, wherein the roughened surface
or parts of the roughened surface and the lubricating liquid have
an affinity for each other such that the lubricating liquid is
substantially immobilized on the substrate to form a repellant
surface. The meta-stability prevents thermodynamically favorable
displacement of the liquid for at least a certain amount of
time.
[0022] Disclosed subject matter includes, in another aspect, a
method for vapors collection, which includes providing a solid
surface, introducing roughness, chemically functionalizing the
solid surface to enhance affinity of the surface with a lubricant,
introducing the lubricant to wet and adhere to the solid surface to
form an overlayer, wherein the solid surface and the lubricant have
an affinity for each other such that the lubricant is substantially
immobilized on the substrate to form a repellant surface, and
condensing condensate droplets on the repellant surface for liquid
collection.
[0023] Disclosed subject matter includes, in another aspect, an
article having a repellant surface, which includes a substrate
comprising a roughened surface and a lubricant wetting and adhering
to the roughened surface to form a stabilized liquid overlayer,
wherein the liquid covers the roughened surface at a thickness
sufficient to form a liquid upper surface above the roughened
surface, wherein the roughened surface and the lubricating liquid
have an affinity for each other such that the lubricating liquid is
substantially immobilized on the substrate to form a repellant
surface, wherein the substrate is a component of a ski, a luge, a
surf board, a hovercraft, a winter sports item, or a water sports
item.
[0024] Disclosed subject matter includes, in another aspect, a
method for protecting plastic, glass, ceramic, and composite
surfaces from scaling, which includes providing a said solid
surface, introducing roughness, chemically functionalizing the said
surface to enhance affinity of the said surface with a lubricant,
and introducing the lubricant to wet and adhere to the said surface
to form an overlayer, wherein the surface and the lubricant have an
affinity for each other such that the lubricant is substantially
immobilized on the substrate to form a repellant surface, providing
anti-scaling to the said surface.
[0025] Disclosed subject matter includes, in another aspect, a
method for protecting plastic, glass, ceramic, and composite
surfaces from graffiti, which includes providing a said solid
surface, introducing roughness, chemically functionalizing the said
surface to enhance affinity of the said surface with a lubricant,
and introducing the lubricant to wet and adhere to the said surface
to form an overlayer, wherein the said surface and the lubricant
have an affinity for each other such that the lubricant is
substantially immobilized on the substrate to form a repellant
surface, providing anti-graffiti properties to the said
surface.
[0026] Disclosed subject matter includes, in another aspect, method
for forming a repellent surface, which includes providing a
substrate having a surface, depositing a first material having a
charge to said surface; depositing a second material having a
charge that is opposite to the charge of the first material;
sequentially repeating said depositing a first material and said
depositing a second material to provide a roughened surface; and
introducing a lubricant to wet and adhere to said roughened surface
to form an overlayer, wherein said roughened surface and said
lubricant have an affinity for each other such that the lubricant
is substantially immobilized on the substrate to form a repellent
surface.
[0027] Disclosed subject matter includes, in another aspect, a
method to reduce friction against fluids and solids, which includes
providing a said solid surface, introducing roughness, chemically
functionalizing the said surface to enhance affinity of the said
surface with a lubricant, and introducing the lubricant to wet and
adhere to the said surface to form an overlayer, wherein the said
surface and the lubricant have an affinity for each other such that
the lubricant is substantially immobilized on the substrate to form
a repellant surface, providing anti-graffiti properties to the said
surface.
[0028] Disclosed subject matter includes, in another aspect, a
method to reduce adhesion against fluids and solids, which includes
providing a said solid surface, introducing roughness, chemically
functionalizing the said surface to enhance affinity of the said
surface with a lubricant, and introducing the lubricant to wet and
adhere to the said surface to form an overlayer, wherein the said
surface and the lubricant have an affinity for each other such that
the lubricant is substantially immobilized on the substrate to form
a repellant surface, providing anti-graffiti properties to the said
surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The following figures are provided for the purpose of
illustration only and are not intended to be limiting.
[0030] FIG. 1 shows a schematic of a self-healing slippery
liquid-infused porous surface (SLIPS) in accordance with certain
embodiments of the present disclosure:
[0031] FIG. 2 illustrates a general scheme of creating SLIPS in
accordance with certain embodiments of the present disclosure;
[0032] FIGS. 3A-3B illustrates the comparison between a
thermodynamically stable SLIPS with a kinetically stable
(meta-stable) SLIPS) in accordance with certain embodiments of the
present disclosure;
[0033] FIG. 3C further illustrates an exemplary meta-stable SLIPS
state;
[0034] FIG. 4A-4B shows the wetting behaviors of an exemplary
fluorinated liquid B on (A) a flat surface and (B) nanostructured
surface;
[0035] FIG. 5A shows a schematic of an exemplary columnar porous
material over which the slippery surface is formed;
[0036] FIG. 5B shows a schematic of an exemplary inverse opal
porous material over which the slippery surface is formed;
[0037] FIG. 5C shows an image of an exemplary random network porous
material over which the slippery surface is formed;
[0038] FIG. 5D shows an image of exemplary self-assembled polymeric
microstructures induced by solvent drying in accordance with
certain embodiments of the present disclosure;
[0039] FIG. 5E shows a schematic of an exemplary structured surface
over which the slippery surface is formed;
[0040] FIG. 6 shows a replication process to reproduce the
morphology of the SLIPS surface, where the corresponding surface
characterization indicates ultra-smoothness of the SLIPS, in
accordance with certain embodiments;
[0041] FIG. 7A shows images of SLIPS demonstrating self-healing
properties, where the self-healing time scale is on the order of
100 ms, in accordance with certain embodiments;
[0042] FIG. 7B is a chart showing restoration of liquid repellency
function after critical physical damages (Test liquid=decane,
.gamma..sub.LV=23.6.+-.0.1 mN/m) in accordance with certain
embodiments;
[0043] FIG. 7C shows time-lapse images demonstrating the
restoration of liquid repellency of a SLIPS after physical damage,
as compared to a typical hydrophobic flat surface on which oil
remains pinned at the damage site, in accordance with certain
embodiments;
[0044] FIG. 7D illustrates a self-refilling mechanism in accordance
with certain embodiments;
[0045] FIGS. 8, 9A-9C show some exemplary common natural and
synthetic fabrics systems.
[0046] FIGS. 10A-10C demonstrates SLIPS fabrics for functional
clothing against various complex fluids and high temperature fluids
in accordance with certain embodiments;
[0047] FIG. 11 demonstrates photographs of a fog test on a 60 C
water.
[0048] FIG. 12 shows a schematic illustration of a fog-free optical
viewing cover for microscope.
[0049] FIG. 13 contains a schematic illustration of a circular
optics encased in a lubricant-containing O-ring serving as a
reservoir in accordance with certain embodiments.
[0050] FIG. 14 demonstrates a photograph of camera lens protectors
in accordance with certain embodiments.
[0051] FIG. 15 further demonstrates a photograph of anti-reflective
camera lens protectors in accordance with certain embodiments.
[0052] FIG. 16A shows a regulatory approval chart of various
materials.
[0053] FIGS. 16B and 16C illustrate SLIPS-treated bottles and
containers repelling complex food products, such as ketchup,
mayonnaise, and oatmeal, in accordance with certain
embodiments.
[0054] FIG. 16D illustrates SLIPS-treated ice tray repelling ice,
in accordance with certain embodiments.
[0055] FIG. 17 is a schematic showing different methods to produce
slippery surfaces using fragrance/flavor-enhanced lubricants in
accordance with certain embodiments.
[0056] FIG. 18 illustrates pressure drop on internally coated pipe
as a function of flow in accordance with certain embodiments.
[0057] FIG. 19 illustrates the time lapse of untreated Al (left)
and SLIPS-coated Al (right) immersed in 1 M KOH solution at room
temperature showing rapid degradation of untreated aluminum while
coated Al essentially remains unchanged.
[0058] FIG. 20 shows the steps involved in the nucleation,
coalescence and sliding of water droplets on a conventional
hydrophobic surface and a SLIPS in accordance with certain
embodiments.
[0059] FIGS. 21 and 22 show SLIPS-treated surfaces that can
function as anti-graffiti surfaces in accordance with certain
embodiments.
[0060] FIG. 23A shows a schematic illustration of the
layer-by-layer deposition process to form porous, lubricant-infused
coatings in accordance with certain embodiments.
[0061] FIG. 23B shows SEM images of the silica coating show the
increase in deposited particles with increasing coating cycles in
accordance with certain embodiments.
[0062] FIG. 24A shows a plot demonstrating the increase in
deposited mass for each consecutive layer-by-layer adsorption
cycle, calculated using Sauerbrey's equation from the frequency
drop measured by Quartz Crystal Microbalance in accordance with
certain embodiments.
[0063] FIG. 24B shows a plot of number of silica nanoparticles
deposited onto the substrate during each adsorption cycle (gray)
and as cumulative during the complete process (black line)
calculated from QCM-D data. A near-linear increase in deposited
particles with increasing coating cycles is visible in accordance
with certain embodiments.
[0064] FIG. 24C shows UV-Vis-NIR transmittance spectra of
lubricated samples after calcination and fluorosilanization of the
silica nanoparticle coating. With increasing numbers of deposited
layers, an increase in light transmittance is observed for all
coatings as compared to a normal glass slide in accordance with
certain embodiments.
[0065] FIGS. 25A and 25B show repellency of a 10 .mu.l droplet of
water (a) and octane (b) in dry and lubricated state for coatings
with up to 9 deposited layers. The lubricated samples drastically
outperform both uncoated (0 layers) and dry, coated substrates and
feature extremely small sliding angles for both liquids in
accordance with certain embodiments.
[0066] FIGS. 25C and 25D show time-lapse pictures of a water (c)
and octane (d) droplet sliding under an angle of 2.degree. on a
lubricated substrate with 5 deposited silica nanoparticle layers
without getting pinned to the substrate in accordance with certain
embodiments.
[0067] FIGS. 26A through 26D compares time-lapsed images taken from
for untreated (upper row) and lubricated layer-by-layer assembled
SiO.sub.2 nanoparticle coated surfaces (lower row) using a) honey
in the inside of a glass vial, b) crude oil in a glass tube; c)
octane sliding down a stainless steel surface; d) octane sliding
down a poly methylmethacrylate surface in accordance with certain
embodiments.
[0068] FIGS. 27A through 27D shows contact angle hysteresis and
sliding angles for water and hexadecane for SLIPS formed over PDMS
substrate using a layer-by-layer assembly approach in accordance
with certain embodiments.
[0069] FIG. 28 shows sliding angles as a function of applied strain
in accordance with certain embodiments.
[0070] FIGS. 29A-29D show SEM images of a porous "paper" produced
from boehmite nanofibers in accordance with certain
embodiments.
[0071] FIG. 29E shows a TEM image of individual solvothermal
boehmite nanofibers with some agglomerated particles in accordance
with certain embodiments.
[0072] FIG. 29F shows SEM image of bundled boehmite nanofibers drop
cast on a copper conductive tape in accordance with certain
embodiments.
[0073] FIGS. 30A and 30B show a (A) top view and (B) cross section
HR-SEM images of multi wall carbon nanotubes dispersed in epoxy
resin matrix prior plasma etching in accordance with certain
embodiments.
[0074] FIG. 31A shows an exemplary method to generate surface
functionalized alumina nanoparticles (AlNPs) for use as filler
material in nanocomposites in accordance with certain
embodiments.
[0075] FIG. 31B shows the normalized FTIR absorbance spectra of
O--H stretching mode recorded from AlNPs taken at different
treatment times with Fenton chemistry in accordance with certain
embodiments.
[0076] FIG. 32 shows a schematic design principles of lubricated
nanostructured fabrics (SLIPS-fabrics) in accordance with certain
embodiments.
[0077] FIG. 33 shows SEM images of the weave pattern of different
fabrics in accordance with certain embodiments.
[0078] FIG. 34 shows SEM images of the fabrics after various
different treatments in accordance with certain embodiments.
[0079] FIG. 35A shows static contact angle data for all the
different functionalized fabrics in accordance with certain
embodiments.
[0080] FIG. 35B shows contact angle hysteresis data for all the
different functionalized fabrics in accordance with certain
embodiments.
[0081] FIG. 36 shows twisting test results to determine robustness
for a set of functionalized fabrics in accordance with certain
embodiments.
[0082] FIG. 37 shows drop impact characterization of SLIPS-treated
fabrics in accordance with certain embodiments.
DETAILED DESCRIPTION
[0083] The patent and scientific literature referred to herein
establishes knowledge that is available to those of skill in the
art. The issued U.S. patents, allowed applications, published
foreign applications, and references, that are cited herein are
hereby incorporated by reference to the same extent as if each was
specifically and individually indicated to be incorporated by
reference.
[0084] For convenience, certain terms employed in the
specification, examples and claims are collected here. Unless
defined otherwise, all technical and scientific terms used in this
disclosure have the same meanings as commonly understood by one of
ordinary skill in the art to which this disclosure belongs. The
initial definition provided for a group or term provided in this
disclosure applies to that group or term throughout the present
disclosure individually or as part of another group, unless
otherwise indicated.
[0085] The present disclosure describes slippery surfaces referred
to herein as Slippery Liquid-Infused Porous Surfaces (SLIPS). In
certain embodiments, the slippery surfaces of the present
disclosure exhibit substance-repellent, drag-reducing,
anti-adhesive and anti-fouling properties. The slippery surfaces of
the present disclosure are able to prevent adhesion of a wide range
of materials. Exemplary materials that do not stick onto the
surface include liquids, solids, and gases (or vapors). For
example, liquids such as water, oil-based paints, hydrocarbons and
their mixtures, organic solvents, complex fluids such as crude oil,
fluids containing complex biological molecules (such as proteins,
sugars, lipids, etc) and biological cells and the like can be
repelled. The liquids can be both pure liquids and complex fluids.
In certain embodiments, SLIPS can be designed to be omniphobic,
where SLIPS exhibit both hydrophobic and oleophobic properties. As
another example, solids such as bacteria, insects, fungi and the
like can be repelled or easily cleaned. As another example, solids
such as ice, paper, sticky notes, or inorganic particle-containing
paints, dust particles can be repelled or cleaned. SLIPS surfaces
are discussed in International Patent Application Nos.
PCT/US2012/21928 and PCT/US2012/21929, both filed Jan. 19, 2012,
and U.S. Provisional Patent Applications 61/671,442 and 61/671,645,
both filed Jul. 13, 2012, the contents of which are hereby
incorporated by reference in their entireties.
[0086] Such materials that can be prevented from sticking to the
slippery surfaces disclosed herein are referred to herein as
"Object A." Object A that is in liquid form is referred to as
"Object A in liquid form," or "liquefied Object A," or "Liquid A."
Object A that is in solid form is referred to as "Object A in
solidified form," or "solidified Object A" or "Solid A." Object A
that is in gaseous/vapor form is referred to as "Object A in
gaseous form", or "gaseous Object A". In certain embodiments,
Object A can contain a mixture of both solids and fluids (i.e.,
gas/vapor/liquid mixed with a solid; eg particles in air, or
particles in liquids). In certain embodiments, Object A can contain
a mixture of both gas/vapors and liquids.
[0087] A wide range of materials can be repelled by the slippery
surfaces of the present disclosure. For example, Object A can
include polar and non-polar Liquids A, their mixtures, and their
solidified forms, such as hydrocarbons and their mixtures (e.g.,
from pentane up to hexadecane and mineral oil, paraffinic extra
light crude oil; paraffinic light crude oil; paraffinic
light-medium crude oil; paraffinic-naphthenic medium crude oil;
naphthenic medium-heavy crude oil; aromatic-intermediate
medium-heavy crude oil; aromatic-naphthenic heavy crude oil,
aromatic-asphaltic crude oil, etc.), ketones (e.g., acetone, etc.),
alcohols (e.g., methanol, ethanol, isopropanol, higher alcohols,
propylene glycol, dipropylene glycol, ethylene glycol, and
glycerol, etc.), water (with a broad range of salinity, e.g.,
containing sodium chloride or bromide from 0 to 6.1 M; potassium
chloride or bromide from 0 to 4.6 M, water with high affinity to
scaling, such as having high concentration of Mg and Ca ions,
etc.), acids (e.g., concentrated hydrofluoric acid, hydrochloric
acid, nitric acid, etc) and bases (e.g., potassium hydroxide,
sodium hydroxide, etc), and ice, etc. Object A can include
biological objects, such as insects, small animals, protozoa,
bacteria, viruses, fungi, bodily fluids and fecal matter, tissues,
biological molecules (such as proteins, sugars, lipids, etc.), and
the like. Object A can include gasses, such as natural gas, air or
water vapors. Object A can include solid particles suspended in
liquid. Object A can include solid particles suspended in gas.
Object A can include non-biological objects, such as dust,
colloidal suspensions, spray paints, food items, common household
materials, and the like. Object A can include adhesives and
adhesive films. The list is intended to be exemplary and the
slippery surfaces of the present disclosure are envisioned to
successfully repel numerous other types of materials and materials
combinations.
[0088] In certain embodiments, the slippery surface of the present
disclosure has a coefficient of friction that is lower than that of
polytetrafluoroethylene (PTFE or Teflon.TM.) surface. In certain
embodiments, the coefficient of friction may be less than 0.1, less
than 0.05, or even less than 0.04. In certain embodiments, the
coefficient of friction can be measured by sliding two different
surfaces against each other. The value of the coefficient of
friction should be load-independent. The friction force can depend
on the load applied onto the surface, the sliding velocity, and the
materials of the surfaces. For example, a reference surface, such
as a polished steel, could be used to slide against the target
surfaces, such as Teflon, or the SLIPS of the present disclosure
could be used to slide against itself (e.g., SLIPS/SLIPS) to obtain
the coefficients of friction (both static and dynamic).
[0089] A schematic of the overall design of Slippery Liquid-Infused
Porous Surfaces (SLIPS) is illustrated in FIG. 1. As shown, the
article includes a solid surface 100 having surface features 110
that provide a certain roughness (i.e. roughened surface) with
Liquid B 120 applied thereon. Liquid B wets the roughened surface,
filling the hills, valleys, and/or pores of the roughened surface,
and forming an ultra-smooth surface 130 over the roughened surface.
Due to the ultra-smooth surface resulting from wetting the
roughened surface with Liquid B and forming a flat liquid
overlayer, Object A 140 does not adhere to the surface.
[0090] In certain embodiments, the surface features 110 can be
functionalized with one or more functional moieties 150 that
further promote adhesion of the Liquid B 120 to the surface
features 110. In certain embodiments, the functional moieties 150
can resemble the chemical nature of Liquid B 120. In certain
embodiments, the surface features 110 can be functionalized with
one or more functional moieties 150 that are hydrophobic.
[0091] In some embodiments, the Liquid B follows the topography of
the roughened surface (e.g., instead of forming a smooth layer that
overcoats all the textures). For example, Liquid B may follow the
topography of the roughened surface if the equilibrium thickness of
the overlayer is less than the height of the textures.
[0092] SLIPS can be designed based on the surface energy matching
between a lubricating fluid and a solid (i.e. formation of a stable
lubricating film which is not readily displaced by other,
immiscible fluids). In some embodiments, SLIPS can be designed
based on at least the following three factors: 1) the lubricating
liquid (Liquid B) can infuse into, wet, and stably adhere within
the roughened surface, 2) the roughened surface can be
preferentially wetted by the lubricating liquid (Liquid B) rather
than by the Object A, complex fluids or undesirable solids to be
repelled (Object A), and 3) the lubricating fluid (Liquid B) and
the object or liquid to be repelled (Object A) can be immiscible
and may not chemically interact with each other. These factors can
be designed to be permanent or lasting for time periods sufficient
for a desired life or service time of the SLIPS surface or for the
time till a reapplication of the partially depleted infusing liquid
is performed.
[0093] The first factor (a lubricating liquid (Liquid B) which can
infuse into, wet, and stably adhere within the roughened surface)
can be satisfied by using micro- and/or nanotextured, rough
substrates whose large surface area, combined with chemical
affinity for Liquid B, facilitates complete wetting by, and
adhesion of, the lubricating fluid. More specifically, the
roughness of the roughened surface, R, can be selected such that
R.gtoreq.1/cos .theta..sub.BX, where R is defined as the ratio
between the actual and projected areas of the surface, and
.theta..sub.BX is the equilibrium contact angle of Liquid B on a
flat solid substrate immersed under medium X (X=water/air/other
immiscible fluid medium). R factor can vary between 1 and infinity.
In certain embodiments, R may be any value greater than or equal to
1, such as 1 (flat, smooth surface), 1.5, 2, 5, or even higher.
[0094] The stable adhesion of the liquid B to the underlying solid
is often achieved through chemical functionalization or
applications of a coating that has a very high affinity to both
Liquid B and the solid, thus producing a stable chemical or
physical bonding between the liquid B and the solid.
[0095] To satisfy the second factor (that the roughened surface can
be preferentially wetted by the lubricating liquid (Liquid B)
rather than by the liquid, complex fluids or undesirable solids to
be repelled (Object A)), a determination of the chemical and
physical properties required for working combinations of substrates
and lubricants can be made. This relationship can be qualitatively
described in terms of affinity; to ensure that the Object A to be
repelled (fluid or solid) remains on top of a stable lubricating
film of the lubricating liquid, the lubricating liquid must have a
higher affinity for the substrate surface than materials to be
repelled, such that the lubricating layer cannot be displaced by
the liquid or solid to be repelled. This relationship can be
described as a "stable" region. As stated above, these
relationships for a "stable" region can be designed to be satisfied
permanently or for a desired period of time, such as lifetime,
service time, or for the time till the replenishment/reapplication
of the partially depleted infusing liquid is performed. In order to
create a stable (or energetically favorable) Liquid B-solid
interface, the following condition has to be satisfied:
.DELTA.E.sub.0=.gamma..sub.AS-.gamma..sub.BS=.gamma..sub.BX cos
.theta..sub.RB-.gamma..sub.AX cos .theta..sub.AX>0 (eq. 0)
where .gamma..sub.AS and .gamma..sub.BS are the interfacial tension
of solid-liquid A and solid-liquid B interfaces respectively;
.gamma..sub.BX and .gamma..sub.AX are the interfacial tension of
lubricating fluid (Liquid B) and other immiscible fluid (Liquid A)
with medium X; .theta..sub.BX and .theta..sub.AX are the contact
angle of Liquid B and Liquid A on the solid under medium X, where X
can be air or other immiscible phases with the solid, Liquid A, and
Liquid B. The condition includes both kinetically stable and
thermodynamically stable SLIPS. Also, see FIGS. 3A and 3B.
[0096] Kinetically-stable SLIPS will form for certain combinations
that do not satisfy eq. 0, where either (i) the Liquid B-solid
interface may be gradually replaced by that of the Liquid A-solid
interface over time, t, if Liquid A has a higher affinity to the
solid surface than Liquid B (in other words, if an additional
energy penalty is required to form Liquid B-Liquid A interface); or
(ii) if Liquid A and B show some reactivity or miscibility over
time degrading the slippery interface quality. These kinetically
stable SLIPS would still show improved performance over existing
surfaces, if the SLIPS need to keep their properties only within a
limited period of time.
[0097] In order to create a stable (or
energetically/thermodynamically favorable) SLIPS materials that are
not degraded over time and where Liquid B is not being replaced by
an Object A, the following criteria must be satisfied. A comparison
of the total interfacial energies between textured solids that are
completely wetted by either an arbitrary immiscible liquid
(E.sub.A), or a lubricating fluid with (E.sub.1) or without
(E.sub.2) a fully wetted immiscible test liquid floating on top of
it can be calculated. This can ensure that Object A remains on top
of a stable lubricating film of Liquid B. In order to ensure that
the solid is wetted preferentially by the lubricating fluid, both
.DELTA.E.sub.1=E.sub.A-E.sub.1>0 and
.DELTA.E.sub.2=E.sub.A-E.sub.2>0 should be true. The equations
can be expressed as:
.DELTA.E.sub.1=R(.gamma..sub.BX cos .theta..sub.BX-.gamma..sub.AX
cos .theta..sub.AX)-.gamma..sub.AB>0 (eq. 1)
.DELTA.E.sub.2=R(.gamma..sub.BX cos .theta..sub.BX-.gamma..sub.AX
cos .theta..sub.AX)+.gamma..sub.AX-.gamma..sub.BX>0 (eq. 2)
where R is the roughness factor (i.e. the ratio between the actual
and projected surface areas of the textured solids).
[0098] This relationship can also be qualitatively described in
terms of affinity; to ensure that Object A remains on top of a
stable lubricating film of Liquid B, Liquid B must have a higher
affinity for the substrate than Object A. For example, a solid
functionalized or coated with hydrophilic molecules and infiltrated
with polar Liquids B, will provide a functional oleophobic SLIPS
for repelling oils; a solid functionalized or coated with
hydrophobic moieties and infiltrated with hydrocarbons as Liquid B
will provide a functional hydrophobic surface for repelling polar,
hydrophilic materials, such as water; a solid functionalized or
coated with fluorinated molecules and infiltrated with fluorinated
oils will work as functional SLIPS that are both hydrophobic and
oleophobic; etc. For patterned SLIPS, this relationship can be
described as a "stable" region. Conversely, where Object A has a
higher affinity for the substrate (for example, an unfunctionalized
region of the substrate) than Liquid B, Object A will displace
Liquid B in that region. This relationship can be described as an
"unstable" region.
[0099] To satisfy the third factor (that the lubricating fluid
(Liquid B) and the object or liquid to be repelled (Object A) can
be immiscible and may not chemically interact with each other), the
enthalpy of mixing between Object A and Liquid B should be
sufficiently high (e.g., water/oil; insect/oil; ice/oil, etc.) that
they phase separate from each other when mixed together, and/or do
not undergo substantial chemical reactions between each other. In
certain embodiments, Object A and Liquid B are substantially
chemically inert with each other so that they physically remain
distinct phases/materials without substantial mixing between the
two. For excellent immiscibility between Liquid A and Liquid B, the
solubility in either phase should be <500 parts per million by
weight (ppmw). For example, the solubility of water (Liquid A) in
perfluorinated fluid (Liquid B, e.g., 3M Fluorinert.TM.) is on the
order of 10 ppmw; the solubility of water (Liquid A) in
polydimethylsiloxane (Liquid B, MW=1200) is on the order of 1 ppm.
In some cases. SLIPS performance could be maintained transiently
with sparingly immiscible Liquid A and Liquid B. In this case, the
solubility of the liquids in either phase is <500 parts per
thousand by weight (ppthw). For solubility of >500 ppthw, the
liquids are said to be miscible. For certain embodiments, an
advantage can be taken of sufficiently slow miscibility or mutual
reactivity between the infusing liquid and the liquids or solids or
objects to be repelled, leading to a satisfactory performance of
the resulting SLIPS over a desired period of time.
[0100] In some embodiments, a spatially heterogeneous pattern on a
liquid-coated surface is created by first functionalizing a solid
surface with spatially defined surface energy. When a given
lubricant is wetted on a solid surface, the surface can be designed
such that part of the region can form a stable lubricant film owing
to the matching in surface energies between the solid and lubricant
(i.e. .DELTA.E.sub.1>0 and .DELTA.E.sub.2>0), where the rest
of the regions remain unstable (i.e. .DELTA.E.sub.1<0 and/or
.DELTA.E.sub.2<0). When a suitable immiscible liquid encounters
the unstable lubricating region, it can displace the lubricant and
remain trapped within the patterned region.
[0101] Potential applications of patterned SLIPS include spatially
defined patterning of cells for tissue engineering,
mechano-biology, and single cell study, patterning of biological
fluids, as well as high sensitivity biological sensors. Other
applications include microfluidics, controlled placement of
molecules or material without cross-contamination, etc.
[0102] Heterogeneous topologies or spatially-defined patterns of
selective wettability can be formed on a liquid-coated or
liquid-infiltrated solid substrate (SLIPS). The regions or holes
that allow selective wetting (e.g., of an aqueous phase) can allow,
by way of non-limiting example, local culture of cells, bacteria
patterning for single cell study. DNA/RNA patterning for genomic
sequencing and identification, protein patterning, fluid
condensation and collection, ice nucleation, or transport of liquid
through a SLIPS layer for sensing or drainage functions. The
combination of these ultra-low adhesion and selective wetting (or
wicking) properties can be used for applications for patterning of
biological and non-biological substances, printing of characters,
creating liquid adhesives, or permeable/non-permeable solid
support, or for the design of bandage or `breathing skin layer`
biomedical materials.
General Scheme of Creating SLIPS
[0103] FIG. 2 illustrates a general scheme of creating SLIPS in
accordance with certain embodiments of the present disclosure. Some
of these steps illustrated in FIG. 2 can be combined and repeated;
but in some cases these steps can be skipped (e.g., porous Teflon
does not require the conditioning step at all, just lubrication; if
the solid is already roughened, only functionalization might be
required before lubrication; etc.). In one example, the scheme can
be Original substrate.fwdarw.Surface conditioning
steps.fwdarw.Lubrication to make SLIPS. In another example, the
scheme can be Original surface.fwdarw.Surface
roughening.fwdarw.Surface functionalization.fwdarw.Lubrication. In
yet another example, the scheme can be Original
surface.fwdarw.Coating with a layer of a different
material.fwdarw.Roughening of the additive layer.fwdarw.Surface
functionalization.fwdarw.Lubrication.
[0104] A list of exemplary surface conditioning methods is provided
below:
[0105] 1. Additive surface conditioning methods [0106] bonding
solid phase material (SLIPS or SLIPS-ready sheet, tape, or
laminate) [0107] application of material using liquid phase coating
(paint or ink, spray, spin, dip, air brush, screen printing, inkjet
printing, electrospinning, rotary jet printing) [0108] deposition
or reaction of gas phase material (CVD, plasma, corona, ALD, PVD,
iCVD, oCVD) [0109] sputtering or evaporation of metal or metal
oxide, sulfides, nitrides, mixed oxides, oxo/hydroxo compounds,
silica [0110] evaporation or gas phase deposition of organic small
molecules (parylene), polymers and other carbon-based materials
(CNT, graphite, amorphous carbon, soot, graphene,
buckminsterfullerene, diamond) [0111] composite phase material
deposition (particle or sacrificial particle+binder) [0112]
electrodeposition or other solution phase growth of material
(conducting polymer, electroplated metal, electroless deposition,
electrophoretic deposition of particles, surface-initiated
polymerization, electrostatic assemblies, surface chemistry
reactions, mineralization) [0113] gas phase growth of material
(nanoparticles, nanofibers, nanowires, nanotubes, microparticles,
microfibers, microwires, microtubes) [0114] multiple layer
deposition (repeated coating, layer-by-layer deposition) [0115]
self-assembly of precursor material (minerals, small molecules,
biomolecules, polymers, nano/microparticles, colloids) [0116]
growth of layers by oxidation [0117] fouling-based deposition
(using fouling as the nanostructure itself, e.g. bacterial biofilm,
scaling, marine fouling) [0118] transfer coating and printing
(contact printing, pattern transfer, LB film) [0119] a polymer foam
deposition onto the substrate, with or without an optional
promoter/adhesive layer by spraying of a polymer/prepolymer
mixture/solution/emulsion/suspension/reagent or comonomer mixture
that forms a porous/contiguous porousiopen cell-type structured
porous surface. The polymer can be chosen from a number of
commercially available polymers and their mixtures, non-exhaustive
examples including polyurethane, polystyrene, latex foams, etc.
[0120] accordingly, the appropriately chosen lubricating liquids
can be spray-coated onto these polymer foams with or without
additional conditioning of the polymer surface.
[0121] 2. Subtractive surface conditioning methods [0122]
mechanical/physical etching (sanding, sand and bead blasting,
machining, sputtering) [0123] chemical etching (acid, base,
solvent, gas, anodization, parkerizing, black oxide formation)
[0124] chemical mechanical etching
[0125] 3. Surface conditioning by shape change (deformation) [0126]
wrinkle, crack, crease, ridge, fold formation by mechanically or
acoustically induced change [0127] swelling by solvent or lubricant
or a solution containing chemical additives (oligomers, polymers,
gels, etc.) [0128] imprinting
[0129] 4. Chemical surface conditioning methods [0130] formation of
covalent bonding [0131] formation of ionic bonding [0132] formation
of complex/dative bonding [0133] formation of self-assembled
monolayers through the formation of sulfide bonds, oxide bonds,
silane, phosphate, phosphonate, carboxylate, sulfonate, amine,
etc.) [0134] formation of non-specific adsorption and van-der-Waals
interactions [0135] change of chemical affinity by physisorbed
material-change of chemical affinity by oxidation or reduction,
electrochemical reactions [0136] growth (grafting from) of material
[0137] attachment (graft to) of material [0138] growth and
attachment (grafting through) of material [0139] homogeneous
chemicals [0140] bi- or multi-functional chemical modifiers
(zwitter ionic, block co-polymer, switchable molecules) and their
solutions [0141] chemical structural transformation,
recrystallization (e.g. Boehmitization)
[0142] 5. Physical surface conditioning methods [0143] thermal
(heating or cooling in air, inert gas, water, steam, solvents,
vapors, supercritical fluids, annealing, sintering, melting,
crystallization, phase transformation, carbonization) [0144]
mechanical (compression, tension, shear, expansion, aeration,
foaming) [0145] optical and energetic particles (laser ablation,
gamma irradiation, electron beam, charged particles beams, UV,
particle bombardment) [0146] electrical (joule heating,
electrochemistry) [0147] acoustic (surface acoustic wave
localization)
[0148] 6. Biological surface conditioning methods [0149] growth or
alteration of surfaces using biomolecules
Kinetically Stable SLIPS
[0150] As described above, SLIPS are a class of materials which
typically meet the following three requirements: [0151] 1) the
lubricating liquid (Liquid B) must imbibe into, wet, and stably
adhere within the substrate (Solid); [0152] 2) the solid must be
preferentially wetted by the lubricating liquid rather than by the
liquid one wants to repel (Liquid A); and [0153] 3) the lubricating
and impinging test liquids must be immiscible.
[0154] SLIPS meeting the above three requirements are generally
considered thermodynamically stable, meaning its SLIPS state does
not tend to change considerably over time.
[0155] These factors can be designed to be permanent or lasting for
time periods sufficient for a desired life or service time of the
SLIPS surface or for the time till a reapplication of the partially
depleted infusing liquid is performed. In some situations,
kinetically stable SLIPS, which are stable for a limited period of
time and/or for limited number of exposures to the liquid(s) being
repelled, can still offer performance substantially better than
that of conventional materials. The kinetic stability can be due to
various factors (e.g., high viscosity, slow mixing of liquids
having limited but still appreciable mutual solubility, timescale
of dewetting of lubricant slower than timescale of wetting and
replacement of lubricant by liquid A etc.), while some relations
described in the rigorous thermodynamics-based equations (i.e.,
equations 1 and 2) are not satisfied. FIGS. 3A and 3B illustrate
the comparison between a thermodynamically stable SLIPS with a
kinetically stable (i.e., meta-stable) SLIPS in accordance with
certain embodiments of the present disclosure. There can be many
liquid/liquid/(functionalized) solid combinations that fall into
this category of kinetically stable (a.k.a., meta-stable) SLIPS.
Many of these meta-stable SLIPS can offer cost-effective solutions
with performance exceeding that of known in the art materials. The
imbibing liquid/solid surface functionalization methods can be
chosen from a range offering not thermodynamically best, but
kinetically adequate combinations that are at the same time
compatible with other requirements of the application in question,
e.g. biocompatible, biodegradable, food-compatible and the
like.
[0156] To maintain high immiscibility between Liquid A and Liquid
B, the solubility in either phase should preferably be <500
parts per million by weight (ppmw). For example, the solubility of
water (Liquid A) in perfluorinated fluid (Liquid B, e.g., 3M
Fluorinert.TM.) is on the order of 10 ppmw; the solubility of water
(Liquid A) in polydimethylsiloxane (Liquid B, MW=1200) is on the
order of 1 ppm. SLIPS performance could be maintained transiently
with sparingly immiscible Liquid A and Liquid B. In this case, the
solubility of the liquids in either phase is <500 parts per
thousand by weight (ppthw). For solubility of >500 ppthw, the
liquids can be considered miscible. The following Table 1 contains
examples of kinetically stable combinations of SLIPS. "Y" indicates
that Liquid B forms a stable lubricating film, and does not get
displaced by Liquid A; whereas "N" indicates that Liquid B is
displaced by Liquid A over time. The equilibrium angles,
.theta..sub.A and .theta..sub.B, are estimated from the respective
averages of the measured advancing and receding angles on flat
substrates from at least three individual measurements. R,
.gamma..sub.A, .gamma..sub.B represent the roughness factor of the
substrate and the surface tensions of Liquid A and B,
respectively.
TABLE-US-00001 TABLE 1 Stable Film? Solid Liquid A Liquid B R
.gamma..sub.A .gamma..sub.B .theta..sub.A .theta..sub.B .DELTA.
E.sub.0 Theory Exp Epoxy H.sub.2O FC-70 2 72.6 17.1 83.7 28.1 7.1 Y
Y Epoxy H.sub.2O FC-70 1 72.6 17.1 83.7 28.1 7.1 Y N Silicon
C.sub.16H.sub.34 H.sub.2O 1 27.2 72.6 9.8 7.2 45.2 Y N Silicon
C.sub.10H.sub.22 H.sub.2O 1 23.6 72.6 4.2 7.2 48.5 Y N Silicon
C.sub.8H.sub.18 H.sub.2O 1 21.4 72.6 0 7.2 50.6 Y N Silicon
C.sub.6H.sub.14 H.sub.2O 1 18.6 72.6 0 7.2 53.4 Y N Silicon
C.sub.5H.sub.12 H.sub.2O 1 17.2 72.6 0 7.2 54.9 Y N
[0157] A meta-stable state is created when the lubricant's low
surface tension wets the surface but a "lock in", that is, the
energetical minimum situation is not supported by the surface
chemistry. As a result, the SLIPS state will eventually break down
upon addition of a second liquid. However, this may take time, so a
meta-stable slips surface can be created even though the conditions
for thermodynamic stability are not satisfied. A meta-stable state
could also be created by damaging the surface to an extend that the
supporting roughness is not high enough to allow for a lock in.
FIG. 3C further illustrates an exemplary meta-stable SLIPS state
that is created by patterning the structured solid in a way that
thermodynamically stable SLIPS surfaces are coexisting with surface
regions that do not favor lubricant lock in. The upper part shows a
scheme; the lower parts show photographs of fluorinated surfaces
(support SLIPS) patterned with hydrophilic patches (do not support
SLIPS) consisting of 100 .mu.m dot arrays (left), 500 .mu.m dot
arrays (middle) and 1 mm dot arrays (right). The latter two clearly
show pinning (i.e. the thermodynamically stable situation as shown
in the scheme is reached in the course of the time the droplet
needs to pass the surface) while the first one shows SLIPS
conditions in a meta-stable case (i.e. the hydrophilic parts are
not wetted by octane in the timescale of the droplet sliding down
even though it would be thermodynamically favorable).
Object A
[0158] As noted previously, a wide range of materials can be
repelled by the slippery surfaces of the present disclosure. For
example, Object A can include polar and non-polar Liquids A, their
mixture, and their solidified forms, such as hydrocarbons and their
mixtures (e.g., from pentane up to hexadecane and mineral oil,
aromatic liquids such as benzene, toluene, xylene, ethylbenezene,
aromatic liquids such as benzene, toluene, xylene, ethylbenezene,
paraffinic extra light crude oil; paraffinic light crude oil;
paraffinic light-medium crude oil; paraffinic-naphthenic medium
crude oil; naphthenic medium-heavy crude oil; aromatic-intermediate
medium-heavy crude oil; aromatic-naphthenic heavy crude oil,
aromatic-asphaltic crude oil, etc. and their oligomers and
polymers), ketones (e.g., acetone, etc.), alcohols (e.g., methanol,
ethanol, isopropanol, higher alcohols, propylene glycol,
dipropylene glycol, ethylene glycol, and glycerol, etc.), water
(with a broad range of salinity, e.g., containing sodium chloride
or bromide from 0 to 6.1 M; potassium chloride or bromide from 0 to
4.6 M, water with high affinity to scaling, such as having high
concentration of Mg and Ca ions, etc), acids (e.g., concentrated
hydrofluoric acid, hydrochloric acid, nitric acid, etc) and bases
(e.g., potassium hydroxide, sodium hydroxide, etc), ionic liquids,
supercritical fluids, solutions of pure or mixed solutes, complex
mixture of fluids and solids such as wine, soy sauce and the like,
ketchup and the like, olive oils and the like, honey and the like,
candle soot and paraffin, grease, soap water, surfactant solutions,
and frost or ice, etc. Object A can include biological objects,
such as insects, blood, small animals, protozoa, bacteria (or
bacterial biofilm), viruses, fungi, bodily fluids and fecal matter,
tissues, biological molecules (such as proteins, sugars, lipids,
etc.), and the like. Object A can include gasses, such as natural
gas, air or water vapors. Object A can include solid particles
(e.g., dust, smog, dirt, etc.) suspended in liquid (e.g., rain,
water, dew, etc.) or gas. Object A can include non-biological
objects, such as dust, colloidal suspensions, spray paints,
fingerprints, food items, common household items, and the like.
Object A can include adhesives and adhesive films. The list is
intended to be exemplary and the slippery surfaces of the present
disclosure are envisioned to successfully repel numerous other
types of materials and materials combinations.
[0159] In certain embodiments, more than one different Object A can
be repelled. In certain embodiments, the combination of two or more
Objects A may together be more readily repelled as compared to just
one Object A.
Liquid B
[0160] Liquid B (alternatively referred to as the "lubricant"
through the specification) can be selected from a number of
different materials, and is chemically inert with respect to the
Object A. Liquid B flows readily into the surface recesses of the
roughened surface and generally possesses the ability to form an
ultra-smooth surface overcoat when provided over the roughened
surface. In certain embodiments, Liquid B possesses the ability to
form a substantially molecularly flat surface when provided over a
roughened surface. The liquid can be either a pure liquid, a
mixture of liquids (solution), or a complex fluid (i.e., a
liquid+solid components such as lipid solutions). For instance,
FIG. 6 shows a replication process to reproduce the morphology of
the SLIPS surface. First, a porous solid was infiltrated with
Liquid B (e.g., perfluorinated fluid). Then polydimethylsiloxane
(PDMS) was cured over the Liquid B layer to obtain a negative
replica of the SLIPS surface. Then, epoxy resin (e.g., UVO 114,
Epotek) was used to obtain a positive replica using the PDMS
negative replica. Then metrology analysis was carried out with an
atomic force microscope. As shown, the average roughness of the
positive replica surface was less than 1 nm, where the roughness
represents an upper bound for the actual roughness of Liquid B as
this reaches the physical roughness limits for flat PDMS and UVO
114 epoxy resin. Nonetheless, it is evident from the roughness
analysis that Liquid B overcoats the surface topographies of the
porous solid, forming a nearly molecularly smooth surface.
[0161] In certain other embodiments, Liquid B possesses the ability
to form a substantially molecularly or even atomically flat surface
when provided over a roughened surface.
[0162] In other embodiments, the lubricant layer follows the
topography of the structured surface and forms a conformal smooth
coating (e.g., instead of forming a smooth layer that overcoats all
the textures). For example, the lubricant may follow the topography
of the structured surface if the thickness of the lubricant layer
is less than the height of the textures. In certain embodiments,
conformal smooth lubricant coating, which follows the topography of
the structured surface and can show significantly better
performance than the underlying substrate that was not infused with
the lubricant.
[0163] Liquid B can be selected from a number of different liquids.
For example, perfluorinated or partially fluorinated hydrocarbons
or organosilicone compound (e.g., silicone elastomer) or long chain
hydrocarbons and their derivatives (e.g., mineral oil, vegetable
oils) and the like can be utilized. In particular, the tertiary
perfluoroalkylamnines (such as perfluorotri-n-pentylamine. FC-70 by
3M, perfluorotri-n-butylamine FC-40, etc), perfluoroalkylsulfides
and perfluoroalkylsulfoxides, perfluoroalkylethers,
perfluorocycloethers (such as FC-77) and perfluoropolyethers (such
as Krytox family of lubricants by DuPont, Fomblin family of
lubricants by Solvay), perfluoroalkylphosphines and
perfluoroalkylphosphineoxides as well as their mixtures can be used
for these applications, as well as their mixtures with
perfluorocarbons and any and all members of the classes mentioned.
In addition, long-chain perfluorinated carboxylic acids (e.g.,
perfluorooctadecanoic acid and other homologues), fluorinated
phosphonic and sulfonic acids, fluorinated silanes, and
combinations thereof can be used as Liquid B. The perfluoroalkyl
group in these compounds could be linear or branched and some or
all linear and branched groups can be only partially fluorinated.
In addition, organosilicone compounds such as linear or branched
polydimethylsiloxane (PDMS) (e.g. Momentive Element family silicone
lubricants, Siltech silicone lubricants), polydiethylsiloxane
(PDES), methyltris(trimethoxysiloxy) silane, phenyl-T-branched
polysilsexyquioxane, and copolymers of side-group functionalized
polysiloxanes (e.g. Pecosil silicone lubricants) and combinations
thereof can be used as Liquid B. In addition, various low molecular
weight (up to C14) hydrocarbons (e.g. smokeless paraffin,
Isopar.TM.), long-chain (C15 or higher) alkyl petroleum oils or
"white oils" (e.g. paraffin oils, linear or branched paraffins,
cyclic paraffins, aromatic hydrocarbons to petroleum jelly and
wax), and raw or modified vegetable oils and glycerides and
combinations thereof can be used as Liquid B.
[0164] In certain embodiments, Liquid B has a high density. For
example, Liquid B has a density that is more than 0.5 g/cm.sup.3,
1.0 g/cm.sup.3, 1.6 g/cm.sup.3, or even 1.9 g/cm.sup.3. In certain
embodiments, the density of Liquid B is greater than that of Object
A to enhance liquid repellency. High density fluids reduce the
tendency of any impacting liquid to `sink` below the surface of
Liquid B and to become entrained therein. For Object A that is
smaller than its capillary length (assume Object A is in liquid
form), it is possible that the Liquid B has a density lower than
that of the Object A, where the SLIPS formed by Liquid B can remain
functional.
[0165] In certain embodiments, Liquid B has a low freezing
temperature, such as less than -5.degree. C., -25.degree. C., or
even less than -80.degree. C. Having a low freezing temperature
will allow Liquid B to maintain its slippery behavior at reduced
temperatures and to repel a variety of liquids or solidified
fluids, such as ice and the like, for applications such as
anti-icing surfaces.
[0166] In certain embodiments, Liquid B can have a low evaporation
rate, such as less than 1 nm/s, less than 0.1 nm/s, or even less
than 0.01 nm/s of the thickness of the lubricant per a given area.
Taking a typical thickness of Liquid B to be about 10 .mu.m and an
evaporation rate of about 0.01 nm/s, the surface can remain highly
liquid-repellant for a long period of time without any refilling
mechanisms.
[0167] FIGS. 7A to 7C demonstrates the self-healing features of
SLIPS. In certain embodiments, the lifetime of the surface can be
further extended by using a self-refilling mechanism as illustrated
in FIG. 7D.
[0168] Experimentally, it is observed that Liquid A can become
highly mobile on the surface of Liquid B when the kinematic
viscosity of Liquid B is less than 1 cm.sup.2/s. Since liquid
viscosity is a function of temperature (i.e., liquid viscosity
reduces with increasing temperature), choosing the appropriate
lubricant that operates at the aforementioned viscosity (i.e. <1
cm.sup.2/s) at specific temperature range is desirable.
Particularly, various different commercially available Liquid B can
be found at the specified viscosity, such as perfluorinated oils
(e.g., 3M.TM. Fluorinert.TM. and DuPont.TM. Krytox.RTM. oils), at
temperatures ranging from less than -80.degree. C. to greater than
260.degree. C. For example, the temperature dependence of liquid
viscosity of DuPont Krytox oils is shown in Table 2 as a specific
example (note: data is provided by the manufacturer of DuPont
Krytox oils).
TABLE-US-00002 TABLE 2 Temperature dependence of liquid viscosity
of DuPont Krytox Oils. Viscosity (cm.sup.2/s) Temperature Krytox
Krytox Krytox Krytox Krytox Krytox Krytox Krytox (.degree. C.) 100
101 102 103 104 105 106 107 20 0.124 0.174 0.38 0.82 1.77 5.22 8.22
15.35 40 0.055 0.078 0.15 0.30 0.60 1.60 2.43 4.50 100 -- 0.02 0.03
0.05 0.084 0.18 0.25 0.42 204 -- -- -- -- -- 0.031 0.041 0.06 260
-- -- -- -- -- -- 0.024 0.033
[0169] Liquid B can be deposited to any desired thickness. A
thickness of Liquid B which is on the order of the surface
roughness peak-to-valley distance of the porous substrate provides
good liquid-solid interaction between the substrate and Liquid B.
When the solid substrate is tilted at a position normal to the
horizontal plane, liquid layer with thickness below a
characteristic length scale can maintain good adherence to the
roughened surface, whereas liquid layers above the characteristic
length can flow, creating flow lines (surface defects) and
disrupting the flatness of the fluid surface. For example,
non-limiting thicknesses for the fluid layer (as measured from the
valleys of the roughened surface are on the order of 5-20 .mu.m
when the peak to valley height is .about.5 .mu.m.
[0170] In certain embodiments, Object A (i.e., the test liquid) and
Liquid B (i.e., the functional liquid layer) may be immiscible. For
example, the enthalpy of mixing between Object A and Liquid B may
be sufficiently high (e.g., water and oil) that they phase separate
from each other when mixed together.
[0171] In certain embodiments, Liquid B can be selected such that
Object A has a small or substantially no contact angle hysteresis.
Liquid B of low viscosity (i.e., <1 cm.sup.2/s) tends to produce
surfaces with low contact angle hysteresis. For example, contact
angle hysteresis less than about 5.degree., 2.5.degree., 2.degree.,
or even less than 1.degree. can be obtained. Low contact angle
hysteresis encourages test Object A sliding at low tilt angles
(e.g., <5.degree.), further enhancing liquid repellant
properties of the surface. The mechanics of SLIPS surfaces are
discussed in International Patent Application Nos. PCT/US2012/21928
and PCT/US2012/21929, both filed Jan. 19, 2012, the contents of
which are hereby incorporated by reference in their entireties.
Roughened Surface
[0172] As used herein, the term "roughened surface" includes both
the surface of a three-dimensionally porous material (such as a
fibrous net) as well as a solid surface having certain
topographies, whether they have regular, quasi-regular, or random
patterns, or largely smooth surfaces with very small surface
features.
[0173] In certain embodiments, the roughened surface may have a
roughness factor, R, greater than or equal to 1, where the
roughness factor is defined as the ratio between the real surface
area and the projected surface area. For complete wetting of Liquid
B to occur, it is desirable to have the roughness factor of the
roughened surface to be greater or equal to that defined by the
Wenzel relationship (i.e. R.gtoreq.1/cos .theta. where .theta. is
the contact angle of Liquid B on a flat solid surface). For
example, if Liquid B has a contact angle of 50.degree. on a flat
surface of a specific material, it is desirable for the
corresponding roughened surface to have a roughness factor greater
than .about.1.5. It is noteworthy that the "slipperiness" of the
surface generally increases with the increase of R for the same
material.
[0174] In certain embodiments, the presence of a roughened surface
can promote wetting and spreading of Liquid B over the roughened
surface, as is demonstrated in FIG. 4. FIG. 4(A) shows a droplet
300 of Liquid B (FC-70, a high boiling point, water-insoluble
perfluorinated trialkylamine) on a flat, unstructured surface 310
prepared from a silanized epoxy resin. The dashed line represents
the location of the upper surface of the substrate. While the
droplet spreads on the surface, it retains its droplet shape and
has a finite contact angle. FIG. 4(B) shows the same Liquid B on an
exemplary roughened surface 320 of the same composition (silanized
epoxy resin). The presence of the roughened surface promotes the
spreading out and filling in of the droplet into the valleys of the
roughened surface. As shown, the nanostructures greatly enhance the
wetting of the Liquid B on the surface, creating a uniformly-coated
slippery functional layer over the topographies.
[0175] In certain embodiments, the roughened surface can be
manufactured from any suitable materials. For example, the
roughened surface can be manufactured from polymers (e.g., epoxy,
polycarbonate, polyester, nylon, Teflon, polysulfone,
polydimethylsiloxane, etc.), metals (e.g., aluminum, steel,
stainless steel, copper, bronze, brass, titanium, metal alloys,
iron, tungsten), plastics (e.g., high density polyethylene (HDPE);
low density polyethylene (LDPE); polypropylene (PP); polystyrene
(PS); polyethylene terephthalate (PET))), sapphire, glass, carbon
in different forms (such as diamond, graphite, carbon black, etc.),
ceramics (e.g., alumina, silica, titania, zirconia, etc), and the
like. For example, fluoropolymers such as polytetrafluoroethylene
(PTFE), polyvinylfluoride, polyvinylidene fluoride, Viton,
fluorinated ethylene propylene, perfluoropolyether, and the like
can be utilized. In addition, roughened surface can be made from
materials that have functional properties such as
conductive/non-conductive, and magnetic/non-magnetic,
elastic/non-elastic, light-sensitive/non-light-sensitive materials.
A broad range of functional materials can make SLIPS.
[0176] In certain embodiments, the roughened surface may be the
porous surface layer of a substrate with arbitrary shapes and
thickness. The porous surface can be any suitable porous network
having a sufficient thickness to stabilize Liquid B, for example a
thickness 50+ nm, or the effective range of intermolecular force
felt by the liquid from the solid material. The substrates can be
considerably thicker, however, such as metal sheets and pipes. The
porous surface can have any suitable pore sizes to stabilize the
Liquid B, such as from about 10 nm to about 2 mm. Such a roughened
surface can also be generated by creating surface patterns on a
solid support of indefinite thickness.
[0177] Many porous materials are commercially available, or can be
made by a number of well-established manufacturing techniques. For
example, PTFE filter materials having a randomly arranged
three-dimensionally interconnected network of holes and PTFE
fibrils are commercially available. FIGS. 5A to 5E illustrate some
non-limiting exemplary embodiments of suitable porous
materials.
[0178] The roughened surface material can be selected to be
chemically inert to Liquid B and to have good wetting properties
with respect to Liquid B. In certain embodiments, Liquid B (and
similarly Object A) may be non-reactive with the roughened surface.
For example, the roughened surface and Liquid B (or Object A) can
be chosen so that the roughened surface does not dissolve upon
contact with Liquid B (or Object A). In particular, perfluorinated
liquids (Liquid B) work exceptionally well to repel a broad range
of Liquids A and their solidified forms, such as polar and
non-polar Liquids A, their mixtures, and their solidified forms,
such as hydrocarbons and their mixtures (e.g., from pentane up to
hexadecane and mineral oil, aromatic liquids such as benzene,
toluene, xylene, ethylbenezene, paraffinic extra light crude oil;
paraffinic light crude oil; paraffinic light-medium crude oil;
paraffinic-naphthenic medium crude oil; naphthenic medium-heavy
crude oil; aromatic-intermediate medium-heavy crude oil;
aromatic-naphthenic heavy crude oil, aromatic-asphaltic crude oil,
etc. and their oligomers and polymers), ketones (e.g., acetone,
etc.), alcohols (e.g., methanol, ethanol, isopropanol, higher
alcohols, propylene glycol, dipropylene glycol, ethylene glycol,
and glycerol, etc.), water (with a broad range of salinity, e.g.,
sodium chloride from 0 to 6.1 M; potassium chloride from 0 to 4.6
M, etc.), acids (e.g., concentrated hydrofluoric acid, hydrochloric
acid, nitric acid, etc) and bases (e.g., potassium hydroxide,
sodium hydroxide, etc), ionic liquids, supercritical fluids,
solutions of pure or mixed solutes, complex mixture of fluids and
solids such as wine, soy sauce and the like, ketchup and the like,
olive oils and the like, honey and the like, grease, soap water,
surfactant solutions, etc. Object A can include biological objects,
such as insects, blood, small animals, protozoa, bacteria (or
bacterial biofilm), viruses, fungi, bodily fluids and tissues,
lipids, proteins and the like. Object A can include solid particles
(e.g., dust, smog, dirt, etc.) suspended in liquid (e.g., rain,
water, dew, etc.). Object A can include non-biological objects,
such as dust, colloidal suspensions, spray paints, fingerprints,
food items, common household items, frost, ice and the like. Object
A can include adhesives and adhesive films. The list is intended to
be exemplary and the slippery surfaces of the present disclosure
are envisioned to successfully repel numerous other types of
materials.
[0179] In addition, the roughened surface topographies can be
varied over a range of geometries and size scale to provide the
desired interaction, e.g., wettability, with Liquid B. In certain
embodiments, the micro/nanoscale topographies underneath the Liquid
B can enhance the liquid-wicking property and the adherence of
Liquid B to the roughened surface. As a result, the Liquid B can
uniformly coat the roughened surface and get entrapped inside at
any tilting angles.
[0180] In addition to the desired topography, the roughened surface
can be conditioned, modified or functionalized to acquire necessary
properties (e.g., affinity, wettability) towards lubricating Liquid
B. For example, the surface can be modified to expose
hydrophilic/polar/charged chemical groups, including but not
limited to hydroxyl, amine, carboxyl, sulfate, sulfonate,
phosphate, phosphonate, carboxylate, ammonium, making it compatible
with wetting by polar liquids, such as water and aqueous solutions
of different pH and ionic strength, ionic liquids and their
mixtures. Imbibing the thus modified roughened surface with polar
liquids will result in oleophobic SLIPS. In another example, the
surface can be modified to expose hydrophobic/non-polar/non-charged
chemical groups or chains, including but not limited to alkyl,
cycloalkyl, aryl, aralkyl, alkene, substituted silyl, that can be
linear, branched or cyclic, making it compatible with wetting by
non-polar liquids, such as hydrocarbons, natural, mineral or
silicone oils, petroleum fractions, molecules containing aromatic,
cycloaliphatic, paraffinic chains of various molecular weight,
length and branching and their mixtures. Imbibing the thus modified
roughened surface with non-polar liquids will result in hydrophobic
SLIPS. In yet another example, the surface can be modified to
expose fluorinated chemical groups or chains, including but not
limited to partially or fully fluorinated hydrocarbon chains,
perfluoropolyethers and other fully or partially fluorinated
liquids described in more detail in the description below. Imbibing
the thus modified roughened surface with fluorinated liquids will
result in omniphobic (both hydrophobic and oleophobic) SLIPS.
General types and principles of surface conditioning, modification,
and functionalization are classified in the description in this
document. Depending on the material of the roughened surface, the
applicable conditioning and functionalization methods can include
physical, chemical treatment as well as a combination of any number
of physical and chemical steps detailed in the following sections.
In addition, a combination of not perfectly matched surface
functionalization and lubricant can also be used. For example, a
robust ice-repellent SLIPS can be made by application of silicone
lubricant on fluorinated surface.
Applications
[0181] Numerous different applications for SLIPS can be envisioned
where surface that repels a wide range of materials is desired.
Some non-limiting exemplary applications are described below.
Example 1
Protective Fabric Materials
[0182] A slippery surface can be applied in functional protective
fabrics/gloves/blankets/towels/laboratory-clothing, roofs, domes
and windows--in architecture, tent, swim-suits, wet suits,
rain-coats, tactical gear, military clothing, firefighter clothing,
and the like. These functional fabric materials can serve as
physical barriers and used to repel a broad range of hazardous
fluids/solids, such as acid, base, oxidizing/reducing agents, toxic
substances, highly flammable liquids, high temperature fluids,
burning oils, fire/flame, low temperature fluids, ice, and
frost.
[0183] SLIPS can be applied onto common fabric materials, such as
natural cotton, and synthetic fabrics (e.g.,
polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET),
polypropylene, polyester, acrylic, nylon, latex, rayon, acetate,
olefin, spandex, kevlar). In this exemplary application, the
lubricating fluids can be chosen from a broad range of
perfluorinated fluids (including but not limiting to the tertiary
perfluoroalkylamines (such as perfluorotri-npentylamine, FC-70 by
3M, perfluorotri-n-butylamine FC-40, etc), perfluoroalkylsulfides
and perfluoroalkylsulfoxides, perfluoroalkylethers,
perfluorocycloethers (like FC-77) and perfluoropolyethers (such as
KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines
and perfluoroalkylphosphineoxides as well as their mixtures can be
used for these applications); polydimethylsiloxane and their
functional modifications; food compatible liquids (including but
not limiting to olive oil, canola oil, coconut oil, corn oil, rice
bran oil, cottonseed oil, grape seed oil, hemp oil, mustard oil,
palm oil, peanut oil, pumpkin seed oil, safflower oil, sesame oil,
soybean oil, sunflower oil, tea seed oil, walnut oil, and a
mixtures of any of the above oils).
[0184] Depending on the chemical affinity of the solid to the
lubricants with respect to the fluids one want to repel, chemical
functionalization and roughening of the solid can further enhance
the chemical affinity. Most of the natural cottons and synthetic
fibers are woven into highly textured, porous surfaces (e.g., see
FIG. 8), in which the solid support can provide enough surface area
for the adherence of the lubricating fluids. When these materials
are converted into SLIPS, appropriate chemical functionalization
schemes can enhance the chemical affinity with the lubricants. The
following are a few examples of the chemical functionalization
schemes for materials where further chemical treatments can be
applied.
[0185] 1) Fluorosilanization of PET: To fluorosilanize PET to
create a highly fluorinated surface, one could start with amines
(e.g., 3-aminopropyltrialkoxysilanes) which can react readily with
PET to activate the ester linkages on the surface. Amine
functionalized PET can react with tetraethylorthosilicate (TEOS) to
create surface hydroxyl groups which can condense with silanes
(e.g., tridecafluoro-1,1,2,2-tetrahydrooctyl)-trichlorosilane).
Protocols to achieve the aforementioned steps can be referred to A.
Y. Fadeev and T. J. McCathy, Langmuir 14, 5586-5593 (1998).
[0186] 2) Deposition of chemically functionalized silica onto
fabric (both natural and synthetic): Another approach to chemically
functionalize fabrics directly is through in-situ synthesis of
silica particles with amine groups at the surface of the fibers
through Stober method (Stober, W.; Fink, A.; Bonn, E. J. Colloid
Interface Sci. 1968, 26, 62). Through this method, the silica
microparticles could covalently bond to the surface of natural and
synthetic fabrics (See FIGS. 9A-9C). With the creation of the
silica surface, one could further fluorosilanize the surface
through the vapor/liquid phase silanization methods.
[0187] With chemically functionalized fabrics, one can apply the
lubricating fluids by a broad range of deposition methods, such as
dip/spray coatings. With these slippery coatings, it was shown that
they can effectively repel a broad range of aqueous, hydrocarbons,
and complex fluids. For example, FIGS. 10A-10C demonstrate SLIPS
fabrics for functional clothing against various complex fluids and
high temperature fluids in accordance with certain embodiments.
Example 2
Self-Cleaning and Self-Replenishing SLIPS Optical Coating
[0188] Optical parts suffer from contamination by dust particle,
grease, and other complex liquids. SLIPS coating can be applied to
keep optics free from fouling. With combined mechanism of removing
condensed water on SLIPS coating layer, tilt, air flow, or
vibration, condensed water can also be removed effortlessly.
[0189] FIG. 11 demonstrates photographs of a fog test on a
60.degree. C. water. The left half of the glass is uncoated; the
right half of the glass is SLIPS coated. The left photo shows the
result after 10 seconds of fog test. The right photo shows the
result after 3 minutes. FIG. 12 shows a schematic illustration of a
fog-free optical viewing cover for microscope.
[0190] An optical quality SLIPS coating can prevent fouling by
foreign material and condensation while the lubricating liquid can
be replenished from surrounding materials such as the O-rings,
bearings, and housing holding the optics in place. For example, a
silicone lubricant can be infiltrated in an O-ring made of silicone
rubber from which the lubricant can be continuously supplied to
replenish and coated surface automatically or manually by external
control (e.g., by turning a screw to squeeze the lubricant from the
reservoir). FIG. 13 contains a schematic illustration of a circular
optics encased in a lubricant-containing O-ring serving as a
reservoir in accordance with certain embodiments.
[0191] FIG. 14 demonstrates a photograph of camera lens protectors
without coating (left) and with coating (right), in accordance with
certain embodiments. When water is applied on the lens protector,
the water spreads on the coated lens protector but beads up on the
coated lens protector. When the coated lens protector is tilted,
the water droplet slides and cleans dusts off the surface. FIG. 15
further demonstrates a photograph of camera lens protectors without
coating (left) and with coating (right), in accordance with certain
embodiments. After the lens protector is tilted, the water droplet
spreads and mostly remains on the uncoated lens protector; while
the water droplet slids to the bottom of the coated lens protector.
The coating can also provide an anti-reflective feature due to the
nanostructure on the surface of the coated lens.
Example 3
SLIPS Containers
[0192] A SLIPS layer can be coated onto the inner and/or outer
surface of containers, such as bottles, bags, and tubes, that are
made out of common plastics (i.e., high density polyethylene
(HDPE); low density polyethylene (LDPE); polypropylene (PP);
polystyrene (PS); polyethylene terephthalate (PET); polycarbonate
(PC); polylactic aid (PLA); polyvinyl chloride (PVC)) plastic-lined
metal containers, metal containers, glass containers, ceramic
containers, or containers of composite materials. Lubricants can be
chosen from food and cosmetics compatible liquids, including but
not limiting to olive oil, canola oil, coconut oil, corn oil, rice
bran oil, cottonseed oil, grape seed oil, hemp oil, mustard oil,
palm oil, peanut oil, pumpkin seed oil, safflower oil, sesame oil,
soybean oil, sunflower oil, tea seed oil, walnut oil, and a
mixtures of any of the above oils. In another embodiment, the
lubricants can be chosen from biocompatible liquids, including but
not limited to fatty acids, glycerolipids, glycerophospholipids,
sphingolipids, sterol lipids, prenol lipids, saccharolipids,
polyketides, and their solutions. The lubricating oils can be
applied to the interior of the bottles or bags by spray-coating,
dip-coating, and vapor deposition process etc.
[0193] In certain embodiments, for the complex fluid and paste-like
mixtures (ketchup, mayonnaise, paints, shampoos, conditioners,
tooth paste, the inner surface of the container or part thereof
will be designed to have appropriate roughness and chemical
functionalization so as to ensure its high affinity towards one or
more major liquid components of the complex fluid/paste (like
various food grade natural oils (olive, vegetable, sunflower,
canola, etc. and their mixtures) for ketchup and mayonnaise; oil
base (mixture of aliphatic and aromatic hydrocarbons and short
chain ketones) of oil paints; essential fatty acids, fatty
alcohols, silicone polymers and their mixtures for shampoos and
conditioners) and thereby produce the needed overlaying liquid
layer inherently within the container.
[0194] In certain embodiments a range of food and biocompatible,
widely used in food/medical/healthcare applications oligomers,
polymers, copolymers of various molecular weights and chemical
structures and their blends can be used for making a roughened
surface and for its functionalization by chemical and/or deposition
means. The examples include, but are not limited to polylactic
acid, polyglycolic acid, polylactide-co-glycolide,
poly-ethyleneglycol, polyethyleneoxide, polypropyleneoxide and
their copolymers, polysulfone, polytetrafluoroethylene, other fully
and partially fluorinated polymers, copolymers and oligomers, as
well as polyolefins, polyesters, polyacetals,
polyvinylidenefluoride, polyacrylates, polyurethanes, silicones,
polycarbonate. An additional non-exhaustive list of polymers used
in food industry, their trade names and approval status by various
regulatory bodies is given in FIG. 16A (adapted from Food
Processing--Handling Brochure 2011 by Professional Plastics, Inc.
which is incorporated here as a reference in its entirety.
[0195] After the slippery coatings are applied on the plastic
bottles, it is shown that the bottles can be capable of repelling a
broad range of complex food fluids and cosmetics, including but not
limiting to ketchup, mayonnaise, honey mustard dressing, Caesar
dressing, ranch dressing, thousand island dressing, blue cheese
dressing. French dressing, ginger dressing, honey Dijon, Italian
dressing, Louis dressing, vinaigrette, Russian dressing, and a
mixture of the above components. The lubricating oils can be chosen
from an oil component/mixture of the oil components that are
present in the food fluids or cosmetics that one wants to repel
(where the oil component is immiscible with the other contents that
are present in the food fluids or cosmetics). The common oil
component can allow for the self-replenishing and self-lubricating
effects of the slippery coatings within the bottles. FIG. 16B
illustrates SLIPS-treated bottles repelling complex food products,
such as ketchup and mayonnaise. FIG. 16C similarly shows a
SLIPS-treated plastic bag repelling warm oatmeal.
[0196] FIG. 16D shows a SLIPS-treated ice tray repelling ice.
[0197] In yet another example, after the slippery coatings are
applied on the plastic bags, it is shown that the bags can be
capable of repelling a broad range of 1) biological solids/fluids,
including but not urine, blood, feces, whole blood, plasma, serum,
sweat, feces, urine, saliva, tears, vaginal fluid, prostatic fluid,
gingival fluid, amniotic fluid, intraocular fluid, cerebrospinal
fluid, seminal fluid, sputum, ascites fluid, pus, nasopharengal
fluid, wound exudate fluid, aqueous humour, vitreous humour, bile,
cerumen, endolymph, perilymph, gastric juice, mucus, peritoneal
fluid, pleural fluid, sebum, vomit, and combinations thereof; 2)
complex food fluids including but not limited to ketchup,
mayonnaise, honey mustard dressing, Caesar dressing, ranch
dressing, thousand island dressing, blue cheese dressing, French
dressing, ginger dressing, honey Dijon, Italian dressing, Louis
dressing, vinaigrette, Russian dressing, oatmeals, and a mixture of
the above components; 3) cosmetics including but not limited to
body/facial lotions. The lubricating oils can be chosen from an oil
component/mixture of the oil components that are present in the
food fluids or cosmetics that one wants to repel (where the oil
component is immiscible with the other contents that are present in
the food fluids or cosmetics). The common oil component can allow
for the self-replenishing and self-lubricating effects of the
slippery coatings within the containers.
Example 4
Fragrance/Flavor-Enhanced SLIPS
[0198] Slippery surfaces with fragrance or flavor enhancement,
which can be applied onto polymeric, ceramic, metallic or composite
surfaces for different industrial and medical applications where
imparting of a pleasant odor, masking of an unpleasant odor,
imparting or supporting of a particular flavor or taste or any
combination of the above effects are required. The key novelty of
the invention is the incorporation of tailor-made lubricants that
in addition to their ability to be functional elements of the
slippery, liquid/solid/complex fluid-repellant surfaces, possess
the desired odor/taste/flavor characteristics.
[0199] In this embodiment, a slippery, repellant coating is that
includes a chemically or physically
modified/conditioned/functionalized structured solid surface having
a desired degree of roughness that is infused with a lubricating
fluid is described. Various modifications of the concept that are
based on hybrid materials that are pre-swollen with said
lubricating fluid are included and covered by this embodiment, as
well.
[0200] The lubricating fluids can be chosen from a variety of
natural and synthetic oils, a subset of which would include food or
biologically-compatible liquids, including but not limited to olive
oil, canola oil, coconut oil, corn oil, rice bran oil, cottonseed
oil, grape seed oil, hemp oil, mustard oil, palm oil, peanut oil,
pumpkin seed oil, safflower oil, sesame oil, soybean oil, sunflower
oil, tea seed oil, walnut oil, and a mixtures of any of the above
oils.
[0201] Another subset of lubricating liquids includes synthetic
oligomeric and polymeric long-chain hydrocarbon-, silicone-, fully
or partially fluorinated materials with carbon-carbon,
carbon-nitrogen, carbon-oxygen, carbon-sulfur, carbon-phosphorus
and other carbon-heteroatom linkages and combinations thereof, with
varying molecular weights, linear or having varying degrees of
branching and varying relative proportions of the different types
of co-monomers or linkages present within their structures. These
lubricating oils can be further modified by the addition of or
functionalization with odor- or flavor-imparting components or
modifiers to provide the desired multi-sensory functions, such as
imparting of a pleasant odor, masking of an unpleasant odor,
imparting or supporting of a particular flavor or taste or any
combination of the above effects.
[0202] As shown in FIG. 17, these odor- or flavor-imparting
components can be added to the base oil, as such, to be dissolved
(Method 1), emulsified, or otherwise dispersed (Method 3);
alternatively, they can be included together with
specially-engineered carrier matrices that are formulated for slow
release (Method 2); they can also be chemically attached to the
molecules comprising the lubricating liquid. There is a wide
variety of the fragrant and flavor materials to be chosen from
natural, nature-identical and fully synthetic ones, including those
produced by means of biotechnology.
[0203] Those skilled in art will recognize that the list of the
chemicals used in flavor, fragrance, cosmetics and food industries
is extremely broad, so by the way of reference, two following
exemplary sources are included here: [0204] 1. Rowe, D. J. (2005).
Chemistry and Technology of Flavour and Fragrance, John Wiley &
Sons [0205] 2. Berger, R. G. (2007). Flavours and Fragrances:
Chemistry, Bioprocessing and Sustainability, Springer.
[0206] A large proportion of fragrance chemicals are hydrophobic in
nature and therefore compatible/soluble with hydrophobic
lubricating fluids. Common classes of hydrophobic fragrant
chemicals include olefins, esters, ketones, long chain alcohols and
aldehydes and many more. An exemplary, not meant to be limiting
list of the typical molecules that could be combined with the
non-polar lubricants includes, e.g., S-limonene, R-limonene,
dipentene, phenethyl isobutyrate, phenethyl isovalerate, octanol,
nonanol, or their mixtures etc. The fragrance/favor enhanced
lubricating oils can be applied by spray-coating, dip-coating, and
even vapor deposition process etc. For certain embodiments, the
fragrance or flavor enhancers are chosen such that they are
biodegradable/with biological origins, and with smells or flavors
viewed positively and considered pleasant by a big proportion of
the general population; the other important considerations are the
cost and IP: there is a big number of industrially produced,
inexpensive fragrant chemicals that are either not patentable or
are off patents, which can be used as art of the formulation of the
fragrance-enhanced lubricants.
[0207] The fragrance/flavor-enhanced slippery surfaces described
above are capable of repelling a broad variety of aqueous-based
complex fluids including food and human excretes. The slippery
surfaces can be coated onto surfaces that are made out of common
plastics (e.g., high density polyethylene (HDPE); low density
polyethylene (LDPE); polypropylene (PP); polystyrene (PS);
polyethylene terephthalate (PET); polyvinyl chloride (PVC)),
ceramics (e.g., glass), and metals (e.g., aluminum).
[0208] Such fragrance or flavor-enhanced SLIPS structures can be
utilized as odor-neutralizer/fragrance enhancer for ostomy bags,
sanitary and toiletry products, toilet bowls, as well as
fragrance/flavor enhancer for food and cosmetic containers and
other surfaces that come in contact with materials that need to be
repelled or move freely on the surface and where the resulting odor
and/or flavor characteristics, when added to the repellant behavior
of the surfaces, add positively to the overall performance and/or
perception of the performance.
Example 5
SLIPS Gas Pipelines
[0209] According to Energy Information Administration, natural gas
pipelines consume an average of two to three percent of throughput
to overcome frictional losses compared to electric transmission
lines, which lose six to seven percent of the energy they carry due
to electric resistance (Energy Information Administration,
Frequently Asked Questions (national-level losses were 6.5 percent
of total electricity disposition in 2007), available at
http://tonto.eia.doe.gov/ask/electricity_faqs.asp#electric_rates2.)
According to Interstate Natural Gas Association of America
(Interstate Gas Pipe Efficiency, Interstate Natural Gas Association
of America, Washington, D.C, release date Nov. 1, 2010,
http://www.ingaa.orgil1885/Reports/10927.aspx), one way to mitigate
these losses is to use internally coated pipes, that provide some
improvement at a cost of $2-$8 per foot depending on the pipe
diameter and the coating used. In this example, internally coated
pipe required less horsepower than uncoated pipe, reducing fuel
from 1.627 to 1.452 MMcf/d. For example, FIG. 18 illustrates
pressure drop on internally coated pipe as a function of flow in
accordance with certain embodiments.
[0210] Drag and friction reducing SLIPS layers can be formed on a
variety of substrates for the applications involving gas flows. For
example, a slippery coating of tubes and pipes can be formed based
on SLIPS. The gas is understood to include gas phase, liquefied,
and supercritical fluids that are subject to high flow rates and
associated energy losses due to friction and drag. The examples of
gases include but are not limited to air, steam, liquefied natural
gas (methane), liquefied petroleum gas, higher alkanes, ethylene,
acetylene, higher alkenes and mixtures thereof, carbon monoxide,
carbon dioxide, oxygen, hydrogen, inert gases (nitrogen, helium,
and noble gases), reactive gases (halogens, hydrogen halides,
ammonia, hydrazine, phosphine, arsine), pure and mixed halogenated
hydrocarbons, pure and mixed hydrofluorocarbons, halogenated
fluorocarbons, etc. In certain embodiments, mixtures of gases, both
reactive and inert can be used (like synthesis gas--CO/H2) as well
as the gaseous reactant mixtures, product mixtures and Side/waste
streams.
[0211] A non-exhausting list of combinations of roughened material
surfaces and methods of their functionalization for retaining
different lubricating liquids are presented below. The surfaces are
proposed to possess the desired levels of roughness and when
necessary further functionalized to ensure that the lubricating
liquid is immobilized and retained within the roughened surface.
For all the examples below, one can, in principle, design
onmiphobic slippery surfaces (those based on polyfluorinated oils
retained within roughened surfaces functionalized to have a strong
affinity to fluorinated molecules), hydrophobic slippery surfaces
(those based on natural or synthetic/mineral oils retained within
roughened surfaces having hydrophobic (not necessarily fluorine
containing) functionalization), and oleophobic slippery surfaces
(those based on aqueous lubricating liquids retained within the
roughened surfaces having appropriately functionalized hydrophilic
surface). The list below is not assumed to include only the most
relevant materials for gas transporting pipes, but it rather
includes several types of materials that may find application in
the friction/drag-reducing applications involving gas flows. It is
also worth noting that the combinations included in this
non-exhaustive list can be applicable for all other applications,
in addition to gas/fluid drag and friction reduction.
[0212] 1. Stainless steel, other steels can be modified by several
methods: with silica or related oxide materials using atomic layer
deposition or by sol-gel method, or electrochemically with a range
of thiol-terminated molecules, or wet etching with acids catalyzed
with iron that selectively etches some portions with defined domain
sizes present in the alloy. The resulting anchor coatings can be
used as such (as in the case of thiol SAMs) or modified further
using Si--OH (or related) functionalities of silica (or other ALD
or sol-gel coating) or the head groups of thiol SAMs. Fully,
partly, or non-fluorinated functionalities introduced this way can
provide the stainless steel with the surface chemistry suitable for
retention of appropriately chosen lubricating liquid. The
lubricating liquid can then be selected, depending on the target
application, from a variety of fluorinated oils or non-fluorinated
natural (olive oil, vegetable oils and such) or synthetic liquids
(higher hydrocarbons--aliphatic, aromatic, mixed, silicon oils and
mixtures thereof).
[0213] 2. Titanium, Tantalum, Niobium and other early and middle
transition metal surfaces (generally covered with oxide layer) can
be functionalized with (polyfluoro)alkane
phosphates/phosphonates/sulfonates/carboxylates that can form
stable SAMs on their surface. The following modification with a
lubricating liquid and its choice are the same as above.
[0214] 3. Aluminum surface modification can be done using a range
of physical, chemical and electrochemical techniques. These can
include controlled conductive polymer deposition and growth, ALD,
sol-gel deposition, Boehmite formation, SAM formation similar to
described above for titanium and other metals, as well as
silanization/fluorosilanization from solution or gas phase. The
following modification with a lubricating liquid and its choice are
the same as above.
[0215] 4. Polymer surfaces, especially those that themselves are
lacking pendant chemical functionalities, can use chemical
(hydrolytic, high-temperature steam, strong acids, bases, oxidants)
and/or plasma etching to provide sufficient number of chemical
functional group (hydroxyls, carboxyls) to allow one to install the
desired surface chemistry. However, in many cases, even the
non-functionalized polymer surfaces are already compatible with a
number of lubricating liquids. In other cases, the combination of
plasma treatment and ALD of silica or related materials can provide
sufficient number of functionalizable reactive groups needed to
modify the polymer surface enough to retain the desired lubrication
liquid. The functionalization can then be carried out using
chlorosilane coupling, amide coupling, glicydyl chemistry, etc.
[0216] 5. Sapphire surface can use high-energy laser treatment to
achieve installation of appreciable numbers of chemical functional
groups.
[0217] 6. Glass and related mixed oxide materials can be etched
with appropriate etchant (e.g., HF, acid piranha) or plasma
treated, if necessary, and then the Si--OH (or other related --OH)
functionalities can be used for further modifications using various
chemical methods. For example, a range of commercially available
fluorinated or non-fluorinated chloro- or alkoxysilanes can be used
to install the desired surface chemistry. Fully, partly, or
non-fluorinated functionalities introduced this way will provide
glass with the surface chemistry suitable for retention of the
appropriately chosen lubricating liquid. The lubricating liquid can
then be selected, depending on the target application, from a
variety of fluorinated oils or non-fluorinated natural or synthetic
liquids and mixtures thereof.
[0218] Other potential applications of SLIPS can include inner
surface of tubes and pipes used in gas transport systems, watch
glasses within the gas transport systems, blades of wind turbines
(the SLIPS-type coating may combine the gas friction reduction and
ice repelling), gas turbines, and gas lines in chemical and
petroleum industries and civilian objects.
Example 6
Anti-Corrosive and Anti-Scaling Coatings
[0219] Many metal surfaces have issues with corrosion that create
pitting, decarburization leading to cracks and mechanical breakdown
of structures caused by contact with acid, base, brine, oxidizing
and reducing chemicals, and acid rain. In addition, metallic,
plastic, ceramic, or composite pipelines and surfaces exposed to
aqueous and non-aqueous systems are subject to the growth of oxide,
hydroxide or oxoacid scale (precipitation fouling) and the
deposition of solid fouling commonly found in boilers and heat
exchangers reducing thermal conduction and in reservoirs and wells
in oil field deteriorating their productivity. Common industrial
fouling deposits include calcium carbonate, calcium sulfate,
calcium oxalate, barium sulfate, magnesium hydroxide, magnesium
oxide, silicates, aluminum oxide hydroxide, aluminosilicate,
copper, phosphates, magnetite, or nickel ferrite. Solid deposits
may also form on the surface of chemical reactors that decreases
thermal conduction, induces undesirable chemical reactions such as
oxidation, polymerization, carbonization, catalyzed by the metallic
walls.
[0220] A SLIPS coating can prevent corrosion, scaling, and unwanted
solid deposition by creating repellent surfaces to various liquids
and solids, in particular, liquids with high acidity or basicity,
sea water, concentrated brine, and hard water. The coatings can be
directly formed on some metals (e.g. aluminum) or by application of
coating materials (e.g. sol-gel alumina based Boehmite) followed by
appropriate chemical functionalization and addition of immiscible
lubricant. In certain embodiments, the lubricating
fluid/appropriately functionalized surface combinations can be used
as anti-corrosive protecting coatings for metal and metalized
surfaces designed to resist the corrosion-inducing environments,
both liquid (fresh, salt and sea water, highly corrosive chemical
and waste streams) and otherwise (exposure to aggressive vapors,
aerosols and mist through evaporation or convection).
[0221] FIG. 19 illustrates the time lapse of untreated Al (left)
and SLIPS-coated Al (right) immersed in 1 M KOH solution at room
temperature showing rapid degradation of untreated aluminum while
coated Al essentially remains unchanged.
Example 7
SLIPS Surfaces for Fluid Collection
[0222] Efficient collection of water condensate can be important
for a number of industrial applications, such as heat transfer and
dew collection. SLIPS surfaces have a very high mobility for even
small water droplets, also cause a very rapid condensation of small
water droplets from the vapor phase. Water droplets on
conventional, hydrophobic surfaces have a contact angle
>60.degree., and are not highly mobile. The edges of the droplet
are pinned such that a reasonably high tilt angle of the substrate
is required to move a droplet of some given size. Conversely, for a
vertically-oriented surface, a droplet must achieve a critical
volume before becoming mobile (Vcrit). FIG. 20 (top) shows the
steps involved in the nucleation, coalescence and sliding of water
droplets on a conventional hydrophobic surface. The Vcrit for SLIP
surfaces is much lower than for conventional hydrophobic surfaces
(FIG. 20B, bottom). Therefore, water droplets coalesce and slide
much more readily than on a conventional surface, and the
efficiency and rate of condensation collection is much higher. In
addition, the condensed droplets on SLIPS tend to suddenly run
quickly due to the large energy gain from coalescence events which
would have been used by friction on other surfaces hence
facilitating the growth of droplets very rapidly by picking up more
droplets. This process promotes the collection of condensed
moisture on SLIPS coated surfaces before they go back to atmosphere
by evaporation.
[0223] The biggest disadvantage of spin coating is the lack of
material efficiency. Only 2-5% of total dispensed materials are
used while the rest goes to the surface of coating bowl and
disposed. Not only the cost of the material itself (e.g.
photoresist used in semiconductor industry) is gradually increasing
but also the cost for properly disposing of these materials are
increasing. The materials used as the body of spin coaters are
generally metals or plastics that can be easily coated with SLIPS,
such as boehmite coating. This specific application does not
require optical clarity nor mechanical durability. A possible
product is in the form of either SLIPS-coated spin coater or
SLIPS-coated liners/sleeves that the users can attach and replace
when needed. The collected materials should be able to be reused
and to reduce the cost of production of semiconductor devices.
Example 8
SLIPS Surfaces for Anti-Graffiti
[0224] A surface was partly treated with SLIPS and adherence of
paint and stickers were tested. As shown in FIG. 21, SLIPS treated
surfaces were highly resistant to spray paint as whereas surfaces
that were not treated with SLIPS were not able to repel the spray
paint. As shown in FIG. 22, SLIPS treated surfaces were highly
resistant to stickers where the stickers were extremely easy to
remove and left no residue. In contrast, the stickers adhered
strongly to surfaces that were not treated with SLIPS and left
residue when removed. Hence, SLIPS surface can be utilized as
anti-graffiti signs.
Example 9
SLIPS Assembled by Layer-by-Layer Deposition Process
[0225] In this example, a layer-by-layer process to alternately
assemble positively charged polyelectrolytes and negatively charged
silica nanoparticles onto a given substrate is utilized. Surface
modification of the particles by silane chemistry and infusion of a
lubricant with matching chemical composition creates a stable
substrate/lubricant interface that repels any immiscible second
liquid. The coating protocol uses adsorption from aqueous solutions
and is thus environmentally benign and can be applied to arbitrary
surfaces, given that they can be brought in contact with water. The
process is completely scalable and can be readily automated.
[0226] FIG. 23A schematically shows the fabrication of the surface
coating. Negative charges are introduced to the substrate (i) and
subsequent layers of positively charged polyelectrolyte (ii) and
negative charged silica nanoparticles (iii) are adsorbed to form a
hybrid thin film (iv) that can but not necessarily has to be
calcined to produce a porous silica coating (v). After
fluorosilanization (vi), a fluorinated lubricant is wicked into the
coating (vii) and will not be displaced by a second, immiscible
liquid that slides off the substrate with ease (viii).
[0227] In certain embodiments, negative charges are created on the
substrate by plasma treatment, UV-ozone or immersion in base
piranha. The substrate is subsequently immersed into a solution of
positively charged polyelectrolyte (poly-diallyldimethyl ammonium
chloride, PDADMAC), rinsed and immersed into a solution of
negatively charged Ludox.TM. silica nanoparticles. Electrostatic
attraction leads to the formation of a fuzzy, disordered film of
polymer and nanoparticles. The assembled hybrid film is calcined or
plasma treated to remove the polymer and leave a disordered, porous
silica nanoparticle assembly on the substrate, the surface of which
is subsequently silanized with
1H,1H,2H,2H-(tridecafluorooctyl)-trichlorosilane to introduce
fluorinated surface functionalities. A fluorinated lubricant oil
(DuPont Krytox.TM. 100), matching the surface chemistry of the
coating, is infiltrated into the porous structure. The matching
surface chemistry between surface structures and lubricant creates
a strong affinity and leads to a minimization of the total surface
energy for a solid/lubricant/liquid system in which a second,
immiscible liquid is not in contact with the solid substrate. If
this criterion is fulfilled, the lubricant layer will not be
displaced by other liquids and thus enable a highly efficient
repellency of various, immiscible liquids by elimination of pinning
points.
[0228] Any other combination of surface chemistry and lubrication
can be used as well; including but not limited to alkyl-silanes
with hydrocarbon oils, olive oil, sunflower oil, etc.; pegylated or
hydrophilic silanes with water or ethylene glycol, and the
like.
[0229] SEM images of the silica nanoparticle coating prepared with
different deposition cycles taken after calcination are shown in
FIG. 23B. An increase in particle number and film density with
increasing deposition cycles is visible. Quartz Crystal
Microbalance (QCM) measurements further show evidence of a constant
addition of silica nanoparticles with each deposition cycle after
the first two cycles (FIGS. 24A and 24B). This allows for a precise
adjustment of the total roughness and thickness of the coating.
UV-Vis-NIR transmittance measurements of the lubricated substrates
show an increase in light transmittance throughout the visible
spectrum compared to a reference glass slide for all coated
substrates (FIG. 24C). A slight increase in transmittance with
increasing number of layers is detected which is attributed to an
increase in surface roughness leading to a more diffuse interface
that reduces the reflection of light.
[0230] The repellent properties of the coatings with varying
numbers of deposited layers were quantified by contact angle and
sliding angle measurements using water and octane as test liquids.
With increasing layer thickness, the static water contact angle
after fluorosilanization steadily increased and leveled at
120.degree. for 4 or more deposition cycles, indicating a complete
coverage of the surface with silica nanoparticles. Thus, the dry
coating does not possess superhydrophobic properties due to the
extremely small size of the silica nanoparticles and the absence of
hierarchical superstructures. As a consequence, a droplet of water
placed on a coated surface experiences strong pinning and slides of
only after tilting to very high substrate angles (FIG. 25A, light
gray columns). Similarly, an octane droplet is pinned but, due to
its lower surface tension it starts moving at approximately 350
(FIG. 25B). However, it leaves a stained surface behind. The
addition of lubricant has strong effects on the repellency
properties. The absence of pinning points for the liquid residing
on top of the lubricant layer leads to highly efficient repellency
with extremely low contact angle hysteresis and sliding angles of
approximately 2.degree. for both water and octane (FIGS. 25A-25B).
FIGS. 25C and 25D exemplarily show the highly efficient removal of
a droplet of water and octane on a lubricated substrate tilted at
an angle of 2.degree. coated with 5 layers of silica nanoparticles.
Effective liquid repellency, characterized by a sliding angle
dropping below 5.degree. is achieved for coatings with at least 3
(octane) or 4 layers (water) (FIGS. 25A-25B). The low sliding
angle, hinting at the absence of pinning points, indicates that the
surface roughness in coatings from 3 or more deposition cycles is
sufficient to enable stable repellency as the lubricant film is not
displaced by the liquid to be repelled.
[0231] The solution-based assembly method allows for the coating of
arbitrarily shaped surfaces. In FIGS. 26A-26D, time-lapsed images
that demonstrate the efficient repellency of honey from the inside
of a coated glass vial (FIG. 26A, lower row) and of crude oil from
the inside of a glass tube (FIG. 26B, lower row) are shown,
visualized by clear sliding of the fluid without getting stuck to
the surface. Honey and crude oil were chosen as examples of
extremely sticky complex fluids that cannot be removed from
uncoated surfaces (FIGS. 26A-26B, upper row). Similarly, other
complex fluids (PMMA solution in dimethylformamide, mustard) are
easily repelled from arbitrarily-shaped glass objects such as
chemical flasks and highly curved test-tube surfaces. The
layer-by-layer deposition process can be applied to a large variety
of substrate materials. The only requirement for the process is the
possibility to create charges on the substrate surface, which can
be achieved by a variety of methods, including treating the
substrates with oxygen plasma, UV-ozone, acid or base piranha or a
corona discharger. The treatment time can be chosen to be short
enough not to degrade the substrate material since a very short
exposure is sufficient to create a charged interface. FIGS. 26C and
26D exemplarily demonstrate the successful assembly of the
omniphobic, highly repellent layer-by-layer silica nanoparticle
coating on a metal (stainless steel) and a polymer substrate (poly
methylmethacrylate) by showing the sliding of a stained octane
droplet under an angle of 15.degree. without leaving traces on the
surface. Untreated substrates were completely stained by the same
treatment (FIGS. 26C and 26D, upper row). Further examples of
successfully coated surfaces, include aluminum, poly propylene and
polysulfone.
[0232] Table 3 quantifies the wetting behavior of all tested
substrates by comparing the sliding angles of water and octane for
uncoated samples, fluorosilanized layer-by-layer silica
nanoparticle coatings and the same coatings after addition of
lubricant. All uncoated samples failed to remove water as the
droplets remained pinned even after tilting the substrate to
90.degree. and were wetted and stained by octane. The introduction
of the surface coating changed the wetting properties consistently
for all samples but showed high contact angle hysteresis and
sliding angles for both liquids. The presence of octane stains on
the surfaces indicated the failure of the dry coating in repelling
the liquid. All coated, lubricated samples showed extremely small
sliding angles, contact angle hysteresis and absence of staining,
thus demonstrating the highly efficient repellency of water and
octane as an example of a low surface tension liquid.
TABLE-US-00003 TABLE 3 Sliding angles of octane and water on
different substrates coated with a layer-by-layer silica
nanoparticles coating (7 deposited layers). Water sliding
angle/.degree. Octane sliding angle/.degree. Lubri- Lubri-
Substrate Un- Dry cated Un- Dry cated Material coated coating
coating coated coating* coating** Glass 56 .+-. 8 66 .+-. 5 2 .+-.
1 16 .+-. 3 31 .+-. 3 2 .+-. 1 Aluminum pinned 63 .+-. 4 2 .+-. 1
wetted 51 .+-. 13 2 .+-. 1 Stainless pinned 85 .+-. 5 1 .+-. 1
wetted 49 .+-. 7 1 .+-. 1 Steel PMMA pinned pinned 2 .+-. 1 wetted
46 .+-. 5 2 .+-. 1 PP pinned pinned 1 .+-. 1 wetted 48 .+-. 6 2
.+-. 1 PSu pinned pinned 2 .+-. 1 wetted 44 .+-. 5 2 .+-. 1 *octane
droplet left stains on the surface after sliding **no contamination
of the surface alter sliding
[0233] In conclusion, a simple coating to introduce efficient
liquid repellency has been demonstrated to a wide variety of
materials with completely arbitrary shapes. The surface structure
is prepared by a layer-by-layer deposition of positively charged
polyelectrolytes and negatively charged silica nanoparticles. After
fluorosilanization of the silica nanoparticles, a fluorinated
lubricant is infiltrated into the porous coating and firmly held in
place by matching surface chemistry. The strong affinity of the
lubricant to the substrate prevents a second liquid from getting
into contact with the substrate and resides on top of the lubricant
layer, whose fluid nature gives rises to an extremely smooth
interface without pinning points. Therefore, the liquid slides off
the substrate with ease. The small size of the silica nanoparticles
applied in the process does not interfere with light of visible
wavelengths and, thus, gives rise to a completely transparent
coating. Successful repellency of water, octane as a low surface
tension liquid and various complex fluids on a variety of
arbitrarily shaped ceramic, metal and polymer surfaces has been
demonstrated. The deposition process is conceptually simple, of low
cost, based on aqueous solvents and thus environmentally benign,
completely scalable and readily automatable. The presented method
thus combines all the remarkable properties of previously reported
liquid infused coatings with an unprecedented degree of simplicity
and versatility with respect to accessible substrate materials,
shapes and sizes.
Example 10
SLIPS Assembled by Layer-by-Layer Deposition Process Over PDMS
Substrate
[0234] PDMS is a material widely used in medical equipment, for
example in catheters. Also, it is the material of choice for
microfluidic technologies. Therefore, repellent coatings on PDMS
are of relevance. A layer-by-layer adsorption process was applied
on PDMS that was oxygen plasma treated for 1 minute to induce
negative surface charges. The layer-by-layer assembly technique
shown in FIG. 23A was utilized to form SLIPS surfaces.
[0235] Contact angle hysteresis and sliding angle (20 .mu.l)
measurements of water and hexadecane confirm the presence of a
repellent coating, as shown in FIGS. 27A-27D.
[0236] In addition, the effect of strain (0% to 20%) on the
retention of the slippery nature of layer-by-layer coated,
lubricant infiltrated PDMS with 0 layers (reference, top) and 9
layers (bottom) are compared in FIG. 28. As shown, the slippery
properties are retained with significant amounts of strain.
Example 11
SLIPS from Sol-Gel Derived Nanoporous Boehmite Nanofiber Paper
[0237] Another potential class of SLIPS substrate is based on
free-standing nanoporous films/membranes using high-aspect-ratio
bohemite nanofibers. High-aspect-ratio boehmite nanofibers can be
prepared using a solvothermal synthesis.
[0238] FIGS. 29A-29D show SEM images of such a porous "paper"
produced from boehmite nanofibers. As shown, the boehmite
nanofibers tend to align.
Example 12
Free Standing Boehmite Films
[0239] In an experiment similar to Example 11, 6.8 g of aluminum
isopropoxide (precursor) is added dropwise to 60 mL of water heated
to 75.degree. C. to maximize the hydrolysis of the precursor. If
precursor is added too fast there is potential for premature
self-condensation of the particles resulting in the formation of
agglomerated chunks rather than fibers. Once the entire precursor
is added, the solution is heated to 90.degree. C. to allow the
vaporization of isopropyl alcohol (byproduct of the reaction). The
hot solution is then transferred to a Teflon-lined stainless steel
pressure vessel and 0.61 g of glacial acetic acid is slowly added
to the solution with stirring to lower the pH to .about.3. The
acetic acid increases the rate of hydrolysis of the precursor in
addition to promoting unidirectional growth of boehmite along one
plane of the particles. The autoclave is heated to 150.degree. C.
for 6-24 h. The time of the reaction directly correlates to the
length of the nanofibers obtained, longer reaction time results in
longer nanofibers. TEM characterization was performed on a drop
cast sample of the resultant solution to determine the aspect ratio
of nanofibers.
[0240] The resulting solution from the reaction is diluted to
approximately 2.8 wt. % nanofibers and 1 wt. % polyvinyl alcohol
(3000-4000 MW) is added. The mixture is sonicated for 30 min and
the resulting solution is degassed under vacuum. The solution is
cast in a Teflon-lined dish and slowly dried in an oven at
40.degree. C. for 48-72 h. The resulting free-standing boehmite
nanofiber film can be gently peeled off of the dish. FIG. 29E shows
a TEM image of individual solvothermal boehmite nanofibers with
some agglomerated particles. FIG. 29F shows SEM image of bundled
boehmite nanofibers drop cast on a copper conductive tape.
[0241] The film thickness can be adjusted by modifying the
concentration of bohemite nanofibers and polyvinyl alcohol.
[0242] Modification of the standard SLIPS procedure via alumina
sol-gel route can be successfully altered to produce comparable
surfaces with a greater range of application methods.
Example 13
Carbon Nanofiber--Epoxy Surfaces for SLIPS Applications
[0243] Epoxy EPON 862 and curing agent EPIKURE W were purchased
from Miller-Stephenson, carbon nanofibers, graphitized (iron-free)
were purchased from Sigma-Aldrich, and acetone was purchased from
Sigma-Aldrich.
[0244] The epoxy-based carbon nanotube composites were fabricated
by immersing the MW-CNT fibers into an acetone for 30 min in
ultrasonic bath, then solution of Epon 862 epoxy was added to the
mixture CNT/Acetone. Acetone reduces viscosity of the epoxy making
it possible to better dispersion of CNTs. Solution of
CNT-Acetone/Epon 862 was gradually heated to 70.degree. C. under
vigorous stirring to remove residue of acetone, than Epikure curing
agent W was added in the ratio of 100:25 to the Epon 862 and
stirred for additional 30 min. Degassing is performed under vacuum
to remove the bubbles generated during mixing. Samples were cured
in vacuum oven at 70.degree. C. for 48 h. Plasma etching was used
to etch epoxy matrix.
[0245] FIGS. 30A and 30B show a (A) top view and (B) cross section
HR-SEM images of multi wall carbon nanotubes dispersed in epoxy
resin matrix prior plasma etching. Scale bars are 200 nm. Samples
were spattered with 3 nm Pt/Pd alloy prior to image
acquisition.
Example 14
Superhydrophobic Alumina Nanoparticles and their Nanocomposites
[0246] Nanoporous surfaces for fabricating SLIPS can be prepared
using materials with inherently robust mechanical properties. FIG.
31A shows an exemplary method to generate surface functionalized
alumina nanoparticles (AlNPs) for use as filler material in
nanocomposites, so that hydrophobicity is achieved that is
sufficient for forming robust SLIPS.
[0247] As shown in FIG. 31A, AlNPs naturally have a native oxide
layer which is neutral. However, for surface modification using
compounds such as organophosphonic acids and organophosphate
esters, high density of surface hydroxyl groups is required. As
shown in Step 1 of FIG. 31A, this is achieved by applying Fenton
chemistry (Iron catalyzed mild piranha solution) with stirring in a
4:1 ratio of H.sub.2SO.sub.4 (0.1 M): H.sub.2O.sub.2 (30%) for
extended periods of time.
[0248] FIG. 31B shows the normalized FTIR absorbance spectra of
O--H stretching mode recorded from AlNPs taken at different
treatment times with Fenton chemistry. The `X` indicates no
modification and `XOH` indicates surface modification using O.sub.2
plasma treatment.
[0249] Next, as shown in Step 2 of FIG. 31A, the hydroxylated AlNPs
are charged into FS100 solution with zirconia grinding dispersion
media and rotated on a ball mill. This maximizes de-agglomeration
and surface modification of the particles. Post modification, the
AlNPs are retrieved by centrifugation and are rinsed with ethanol
at least three times to remove any excess surfactant. Excess
solvent is evaporated from the particles at 70.degree. C. and in
the presence of vacuum.
[0250] Surface functionalized AlNPs can now be re-dispersed in
compatible solvents such as hydrofluoroether (HFE) or
2,2,2-trifluoroethanol (TFE). The resulting dispersions can be used
to cast films onto oxygen plasma treated glass substrates and the
solvent is evaporated at elevated temperatures. To permanently bind
particles to substrates, 1) the particle can be modified with mixed
ligands (e.g. fluorinated and acrylate), 2) epoxy, polyurethane or
a similar binding agent is used. To decrease the viscosity of the
epoxy resin, acetone is added in 5:1 w/w ratio and the resulting
solution is sonicated until it forms a homogeneous mixture. The
curing agent is then added in a 4:1 w/w ratio and is sonicated for
30 min. The functionalized AlNPs are then uniformly coated over the
epoxy and placed at 70.degree. C. in an oven for 48 h to fully cure
the epoxy resin. Initial qualitative observations showed resulting
surface to be superhydrophobic to support SLIPS and much more
mechanically robust than compared to conventional alumina sol-gel
coating. On the other hand the AlNPs can be used as a filler
material in a curable nanocomposite with varying volume fractions
and subsequently be applied to surfaces to form nanoporous films to
support SLIPS.
[0251] Functionalized AlNPs in epoxy composite provide an
alternative to alumina sol-gel coated substrates with increased
mechanical properties.
Example 15
Fabrics Coated with Lubricated Nanostructures Displaying Robust
Omniphobicity
[0252] The development of a stain-resistant and pressure-stable
textile is desirable for consumer and industrial applications
alike, yet it remains a challenge that current technologies have
been unable to fully address. Herein the rational design and
optimization of nanostructured lubricant-infused fabrics are
presented. The improved fabrics demonstrate markedly improved
performance over traditional superhydrophobic (TSH) textile
treatments: SLIPS-functionalized cotton and polyester fabrics
exhibit decreased contact angle hysteresis and sliding angles,
omnirepellent properties against various fluids including polar and
nonpolar liquids, pressure tolerance and mechanical robustness, all
of which are not readily achievable with the state-of-the-art
superhydrophobic coatings.
[0253] As shown in FIG. 32, two methods were developed to create
nanoscale surface roughness: I) coating the textile fibers with
silica micro-particles (SiM), and II) boehmite nanostructure
formation on the textile fibers from sol-gel alumina treatment
(SgB). As shown, a single, bare fiber being functionalized with
SLIPS is depicted in a schematic (A-D). A bare fiber (A) is
roughened with the silica micro-particle (SiM) or sol-gel boehmite
(SgB) approach (B) and fluorinated to achieve chemical similarity
to (perfluoroether) polymer Krytox (C) before the lubricating film
is applied (D). This confers pressure-tolerant, self-healing
repellency against a broad range of fluids. The flow chart (E)
contains more specific information regarding the SiM and SgB
functionalization protocols applied to cotton and polyester
fabrics. Upon fluorination and subsequent infiltration with the
lubricant, SLIPS-fabric can be produced from either approach.
[0254] The two surface modification methods were applied to seven
different types of fabric samples--two cotton and five polyester
(PE)--and the nonwetting performance was evaluated by quantifying
static contact angle, contact angle hysteresis, liquid repellency
after mechanical stress, pressure tolerance, and breathability. The
characterization herein provides strong evidence that SLIPS-fabrics
exhibit unique combination of liquid repellency, durability, and
pressure-tolerance that are difficult to achieve based on
state-of-the-art traditional superhydrophobic materials.
[0255] The Dense polyester was purchased from Sew-Lew Fabrics,
Cambridge, Mass., the microfiber polyester was purchased from
MicroFibres, Inc. and the Nike polyester was cut from Nike Dri-Fit
100% polyester running shorts purchased from City Sports,
Cambridge, Mass. The rest of the fabrics were purchased from nearby
fabric stores, including Sew-Lew in Cambridge, Mass. and Winmill
Fabrics in Boston, Mass. With regard to terminology, "fibers" are
twisted together to makes "threads", which are in turn woven to
make the fabric. The polyester fabrics were treated before silica
micro-bead deposition. Amines readily react with polyester by
nucleophillic acyl cleavage of the ester linkages for surface
activation. Five to eight 2.times.2 cm squares of polyester were
first cleaned with DI water, ethanol, and then hexane. Fabrics were
dried for at least 1 h at 70.degree. C. and further dried with a
heat gun before adding to a 1% solution of
aminopropyltriethoxysilane (APTES, Sigma Aldrich) in anhydrous
toluene (Sigma Aldrich) and stirring for 24 h at 65.degree. C.
under dry nitrogen. Samples were then removed, rinsed with toluene
several times, and dried under vacuum. Dried samples were submerged
in deionized water overnight, removed, rinsed with water, and dried
for at least 3 h under vacuum before immersing in a 1% tetraethyl
orthosilicate (TEOS) solution in water for 4-8 h. Samples were
rinsed with water and dried overnight before silica particle
deposition.
[0256] In-situ polymerization of silica-microparticles onto cotton
or activated polyester was performed to obtain a roughened
substrate for SLIPS. Jersey cotton and Muslin were cleaned with
water, ethanol, and isopropyl alcohol prior to reaction. The
prepared samples were submerged into a 1:3 mixture of methanol and
isopropanol, 20 mL ammonium hydroxide (Sigma Aldrich, St. Louis
Mo.), and 12 mL TEOS (Sigma Aldrich, St. Louis Mo.). All solvents
and chemicals were used without further modification. The mixture
was stirred for 6 h at room temperature, and the samples were
isolated and rinsed extensively with toluene several times. Dried
fabrics were blown with compressed air to remove any residual
detached particles that were not firmly attached to the fabric
fibers. Subsequent fluorosilanization renders the fabric surface
superhydrophobic.
[0257] The roughened silica-bead surface was fluorosilanized either
with 1H,1H,2H,2Hperfluorooctyltriethoxysilane (Sigma-Aldrich) or
perfluorododecyl-1H,1H,2H,2H-triethoxysilane (Gelest). A solution
of 4.8% silane stock and >99.7% acetic acid were mixed in equal
parts in 200 proof ethanol (i.e., in a 1:1:19 ratio of the above
ingredients). After this, mixture was stirred for 60 min (to allow
sufficient oligomerization), the fabrics were dipped into the
mixture for 2-4 min and allowed to hang dry. The silane chains
attach to the surface of the silica coating of the fabric and
render the rough surface superhydrophobic. Silica-microparticle
(SiM) deposition is an effective method used to confer microscale
surface roughness on cotton fabrics. FIG. 33 summarizes the steps
for this scalable process. Fewer steps may be needed to achieve the
desired surface treatment for chemically reactive, hydroxyl-rich
cotton fabrics. To induce covalent adherence of silica particles to
more inert polyesters, a two-step surface activation process was
utilized whereby polyester cleavage using
(3-aminopropyl)triethoxysilane (APTES) and subsequent reaction with
TEOS created silica-like surface functionalities. Chemical
composition of each fabric surface was confirmed using FTIR. Once
silica-like surface chemistry was achieved, uniform particles were
synthesized within all fabric samples to ultimately form a rough,
nanostructured surface. Lastly, fabrics were dipped into an
perfluoroalkyl-silane/ethanol solution to render the rough surface
superhydrophobic, thus completing the SiM functionalization.
[0258] All cotton and polyester samples were oxygen plasma cleaned
for 300 s (250 watts, oxygen flow of 15 cm3/min). Cleaned samples
were dipped in alumina sol-gel pre-cursor. After 10 min, the fabric
was removed and dried overnight at 70.degree. C. Dried samples were
immersed in a 95.degree. C. water bath for 15 min to create
boehmite nanostructures, removed, dried, and then submerged in a 1%
solution of FS-100, a perfluoroalkyl phosphate surfactant (Mason
Chemical Company), in ethanol (Chemguard Inc., Mansfield, Tex.,
USA) for 1 h at 70.degree. C. Samples were rinsed with ethanol and
dried overnight before performing the contact angle and SEM
analyses. Boehmite, formed in a reaction between aluminum and
80-100.degree. C. water, is a dense network of nano-scale AlO(OH)
crossed leaflets that can be fluorinated to become an effective
superhydrophobic surface. The sol-gel approach schematically shown
in FIG. 33 was utilized to coat fabrics with boehmite
nanostructures.
[0259] The surface of SgB or SiM functionalized samples has a
strong affinity to fluorinated oils. To avoid excessive
lubrication, perfluoropolyether lubricant Krytox.TM. (Dupont Inc.)
was applied to wick through the sample and the excess was removed
by contacting the surface of the sample with a Kimwipe. About
30-100 .mu.L of oil infused 4 cm2 of the material, depending on the
fabric thickness.
[0260] SEM characterization was performed with a Zeiss Supra field
emission microscope. Samples were coated by Pt--Pd sputtering for
60-150 s prior to SEM characterization.
[0261] Contact angles were recoded using a contact angle goniometer
(CAM 101, KSV Instruments, resolution=0.01 o) at room temperature.
10 .mu.L droplets of DI water were used for all static contact
angle measurements. Contact angle hysteresis (CAH) values were
obtained by slowly increasing and decreasing droplet volume using a
syringe needle while imaging the droplet movement, measuring
advancing and receding contact angles, respectively, from these
images, and subtracting the averages of these values. At least
seven independent measurements were taken for static, advancing,
and receding contact angles.
[0262] For a twisting test, a 2.times.3 cm SiM or SgB fabric sample
was secured between two medium sized clamp-type paper clips, and
the assembly was hung by affixing one of the clips to a hook. By
rotating the unbound lower clip, the fabrics were twisted
.+-.360.degree.; the first twist was defined as a 360.degree.
rotation clockwise followed by a return to rest position, the
second twist was 360.degree. counterclockwise followed by a return
to rest position, and so on. After the specified number of twists
(0, 5, or 50), the sliding angle of a 20 .mu.L droplet of DI water
was measured at least 3 times. The sliding angle is the tilting
angle at which the droplet begins to slide along the surface
without pinning. The sliding angle data and the SEM
characterization provide a complete picture of the performance
deterioration resulting from the twisting test.
[0263] A SgB or SiM fabric sample was secured to a surface with
tape and vigorously rubbed with a rolled up Kimwipe for
approximately 10 s. This is a preliminary abrasion test that
simulates a contact with other fabrics or the surrounding
environment. Damage was qualitatively observed by testing the
repellency of water before and after rubbing, and SEM
characterization showed the physical damage occurring to the
nanostructure.
[0264] The American Association of Textile Chemists and Colorists
(AATCC) test #193 was used to analyze the repellency of
non-lubricated (TSH) and lubricated (SLIPS) fabric samples to low
surface-tension aqueous test liquids. Eight test liquids, composed
of different volume fractions of IPA in de-ionized water, were
prepared. Beginning with the highest surface tension liquid, a test
droplet was applied to the surface of the fabric sample and allowed
to sit for 30 s. The droplet was then observed to assess the
wetting of the fabric: if the fabric is not wetted, then the
process is repeated for the next test liquid, and if the surface is
wetted then the fabric receives a score corresponding to the
previously applied test liquid (i.e., the lowest surface tension
liquid repelled by the fabric). If the test liquid only slightly
wets the surface, the fabric is assigned a non-integer score
halfway between the previous and current test liquid. A maximum
score of 8 may be achieved, if the sample is not wetted by any of
the test liquids.
[0265] The AATCC test #188 was used to test repellency against
alkanes of decreasing surface tension to characterize the
repellency of oils and other nonpolar liquids. This test is very
similar to the aqueous liquid repellency test: the droplets were
placed on TSH and SLIPS samples for 10 s before the wetting
behavior was observed. Again, the lowest surface tension liquid
that does not wet the surface of the liquid determines the score.
Non-integer scores may be assigned, if only partial wetting occurs,
and a maximum score of 8 is achieved when even test liquid 8, the
lowest surface tension liquid in the test, does not wet the surface
of the fabric.
[0266] The tolerance of fabric samples to pressurized liquids of
high and low surface tension was measured with the droplet impact
test. A pipette was fixed 20.3.+-.0.5 cm above a fabric sample
immobilized on a tilting stage with double-sided tape. A 10 .mu.L
test droplet was carefully ejected from the pipette and impacted
the surface of the fabric at a controlled velocity, and the sliding
angle of the droplet was measured immediately after impact. The
dynamic pressure was estimated by P.sub.dynamic=1/2.rho.V.sup.2,
where .rho. is the density of the liquid and V is the impacting
velocity. The impact velocity was estimated using kinematic
equations, and thus the tetradecane droplet exerts a dynamic
pressure of .about.1520 Pa and the water droplet exerts a dynamic
pressure of .about.1990 Pa. Irreversible pinning occurs for the
superhydrophobic samples and cannot be recorded; the most important
information comes from whether the droplet slides or does not
slide.
[0267] The breathability test was adapted from the standard ASTM
E96-E upright cup water vapor transmission test. Each fabric sample
was tested by a single 3D printed capsule; the inside of the
capsule was dried by 20 g of Drierite desiccant (Drierite, Inc.,
Xenia Ohio) and separated from the moist air outside of the capsule
by the fabric sample that was sealed onto the capsule by a
ring-shaped cap clamped in place. In between repeated experiments,
the desiccant was regenerated by placing into a vacuum oven at
.about.150.degree. C. overnight. The external environment of the
chambers was carefully controlled in a custom made environmental
chamber maintained at 50% relative humidity and 23.+-.1.degree. C.
Minimal airflow in the chamber prevented temperature gradients and
inconsistencies. The water vapor was pulled into the chamber
through the sample by the humidity gradient. After initial
weighing, the test capsules were removed from the environmental
chamber and weighed after 1, 2, 3, 4, 5, 6, 8, 22, 24 h, and the
mass increase of each chamber was plotted (FIGS. 6 and 7). To
confirm the omniphobicity, sliding angles of hexadecane and/or
de-ionized water droplets on lubricated samples were recorded. The
mass of the lubricated membranes (and thus the mass of the
lubricant) before and after 24 h was also recorded. A typical
experiment included up to 9 capsules running simultaneously. In
each experiment, two controls were always present to ensure
consistency in conditions between experiments: an open chamber
without a membrane and a chamber sealed by Parafilm, which is
impermeable to water vapor (Pechiney Plastic Company, Chicago,
Ill.). Lubricated and untreated samples were tested against each
other to observe the effect of SLIPS on the breathability of the
fabric. Each sample was tested a minimum of three times, either
with three separate samples in a single experiment or with one
sample across three separate experiments.
[0268] Fabrics introduce unique physical features (hierarchical
feature sizes coming from fiber-thread-weave length scales),
logistical considerations (cost, complexity of procedure), and
demanding applications (requiring durability, breathability, etc.)
into the design space of the final material. Cotton and polyester
(PE) are inexpensive, readily available, widely used, and
environmentally friendly. The weave of the fabric is an important
parameter since it inherently has a much more complex topography
than a simple, flat surface. There are textiles available of myriad
thread sizes, weave densities, and weave patterns; the effect of
these parameters on the quality of the SLIPS coating is unknown and
needs to be investigated.
[0269] A very common weave pattern is a basic, square-type weave.
Since this is a relatively simple system, a number of different
square-weave fabrics were selected--Dense PE, Nike PE, Crepe PE,
and Muslin Cotton (M. Cotton)--with weave densities ranging from
very high (tightly woven) to very low (loosely woven with larger
spaces present) to investigate the role of this parameter in
developing effective omniphobic SLIPS-fabrics. Three fabrics of
different weave patterns were also tested, including the randomly
oriented microfiber (.mu.fiber) threads, the V-shaped weave of
Gavadeen PE (Gay), and the column-based weave of the Jersey Cotton
(J. Cotton) (see FIG. 33). As shown in FIG. 33, the square-weave
fabrics are arranged along the top row (A-D) in order of decreasing
weave density, and the fabrics of other weaves are arranged along
the bottom row (E-G). The two cotton fabrics are on the right edge
of the figure (D, G). Dense Polyester (PE) (A) showcases a tight,
squaretype weave with threads .about.150 .mu.m across, resulting in
a virtually flat surface free of loose fibers. Nike PE (B) exhibits
a looser square-type weave and is comprised of threads .about.200
.mu.m across. Crepe PE (C) is the most loosely woven square-type PE
fabric, with fibers .about.300 .mu.m across. Muslin Cotton (D) is
the least densely woven square-type fabric, with vertically
oriented threads .about.350 .mu.m in diameter, horizontally
oriented threads .about.250 .mu.m in diameter, and large gaps in
between thread intersections. Note the presence of loose threads on
this sample. Gavadeen PE (E) displays a V-type weave comprised of
threads .about.300 .mu.m across; the vertically aligned fibers in
the image are comprised of smaller fibers while the horizontally
aligned threads are comprised of larger fibers, resulting in a
diagonally ridged structure. .mu.fiber (F) has small fibers
.about.5 .mu.m in diameter that create a disordered, "hairy"
structure. Jersey Cotton (G) consists of an entangled weave of
spaciously woven threads .about.200 .mu.m across; many loose
threads are present.
[0270] SiM and SgB treatment and surface fluorination according to
the procedure outlined in FIG. 32, resulted in fabrics uniformly
covered with silica micro-particles (.about.150-500 nm in diameter)
or boehmite nanoflakes, respectively. As shown in FIG. 34, a
scanning electron microscope was used to evaluate the surface
roughness and durability of the sol-gel boehmite (SgB) (A-D) and
silica microparticle (SiM) (E-H) treatments on Nike polyester
fabric. All scale bars are 2 .mu.m. Freshly treated SgB fibers (A)
show full coverage of the fiber with SgB; dramatic microbead
coverage is apparent on freshly treated SiM fibers (E). High
magnification of the microstructures (B, F) reveals the surface
roughness that facilitates good SLIPS performance. When twisted 50
times, smoother boehmite is still present (C) in crevices between
fibers, while the outside of the fibers have become smooth. Also
after 50 twists, the SiM threads (G) exhibit some cracking while
maintaining good microparticle coverage. After vigorous rubbing
with a Kimwipe, SgB fabric (D) exhibits cracking and smoothness on
the outer fibers, while under the same conditions the SiM coating
remains intact (H).
[0271] Droplets bounce off the surface of these fabrics and static
contact angles characteristic of superhydrophobic surfaces
(>150.degree.) were observed (see FIG. 35A). SiM- and
SgB-treated fabrics were then infused with a perfluoropolyether
lubricant (Krytox.TM.. DuPont) that remains stably anchored in the
textured substrate. These SLIPS-fabrics show an unprecedented
ability to repel a wide range of fluids and to be resistant to
staining. To determine the optimal SLIPS fabric parameters, the
static contact angle, contact angle hysteresis, pressure
resistance, durability, and breathability were investigated. Three
phases of testing on a successively smaller set of samples were
investigated as shown in the Table 4 below.
TABLE-US-00004 TABLE 4 Abbre- Phase I Phase II Phase III Fabric
Name viation SgB SiM SgB SiM SgB SiM Muslin Cotton M. Cotton * * *
* * Jersey Cotton J. Cotton * * * Dense Polyester Dense PE * * * *
Nike Polyester Nike PE * * * * * Microfiber .mu.fiber * * * *
Polyester Gavadeen Gav. * * * Polyester Crepe Polyester Crepe * *
*
[0272] To begin Phase I characterization, the static contact angle
were measured on all fabrics to quantify the hydrophobicity of
non-lubricated (TSH) and lubricated (SLIPS) samples. Fabric
samples, both un-lubricated and lubricated with Krytox 102 (K102),
were functionalized with either silica microbeads (SiM) or sol-gel
boehmite (SgB). Contact angles were measured using a contact angle
goniometer. As shown in FIG. 35A, a 10 .mu.L water droplet was
placed onto the surface of the fabric sample for measurement. FIG.
35B shows the advancing and receding contact angles that were
recorded and these values were subtracted to determine the
hysteresis. N=7; error bars are +/-SD. Asterisks denote
statistically significant results (Student's two-tailed t-test,
P<0.05); comparisons are only made between SiM+K102 and SgB+K102
for each fabric sample. As shown, each non-lubricated sample has a
static contact angle in the range of 150-160.degree., and when the
Krytox lubricating film is applied this angle decreases to
approximately 110-120.degree.. To quantify the repellency of the
fabrics, the contact angle hysteresis (CAH), which is the
difference between advancing and receding contact angles as a
droplet slides on a surface and directly relates to droplet
mobility on a surface, was measured. Low CAH was observed on almost
all SLIPSfabric samples. FIG. 35B shows all CAH data for the 14
fabric samples. In the case of non-lubricated fabrics, there are
multiple sources of pinning, including fibrillar protrusions,
structural defects, and perhaps incomplete fluorination leaving
hydrophilic areas on the surface. CAH values increase with
increasing density of defects, or pinning points, on the surface of
the material. Application of a lubricant dramatically reduces
hysteresis for every fabric sample except for J. Cotton and Crepe
PE--droplets easily slide over the smooth surface created by the
lubricating film. In the case of Gavadeen PE treated with
SiM-SLIPS, which has a static contact angle of 156.6.degree..+-.3.1
and a hysteresis value of 5.35.degree..+-.0 3.1, a combination of
superhydrophobic and SLIPS-type performance was observed. It
appears that the lubricant entrapped within and around each
nanostructured thread prevents pinning even if the test liquid is
partially exposed to the non-lubricated, superhydrophobic surface,
a scenario suggested by a relatively high static contact angle and
a relatively low hysteresis value. Thus, fabrics that combine
slippery performance with both SLIPS and TSH attributes have been
produced for excellent overall water repellency.
[0273] Reducing the sample pool with the selection criteria
discussed earlier (Table 5), tests were carried to determine which
treatment method--SgB or SiM--is more robust when subjected to
rubbing and twisting, as observed by the effect of twisting on
sliding angle and coating integrity as studied by SEM. These
experiments simulate the expected wear that fabrics may experience
in most functional applications.
[0274] The twist testing data are shown in FIG. 36. The fabric
samples were twisted +/-360.degree. with a custom-made setup, and
the sliding angle of water (20 .mu.L droplet volume) on a fabric
sample lubricated with Krytox 102 was measured after 0, 5, and 50
twists. Sliding angles that exceeded 35.degree. are indicated on
FIG. 36 as being 35.degree. with arrows ( ) because of experimental
constraints and the large variability associated with strong
pinning behaviors. Notably, the test water droplet did not wet any
of the fabric samples after twisting 50 times. Remarkably, even
when pinning was observed, the colored test water droplets could be
rinsed away without leaving a stain.
[0275] SgB Gav. and SgB M. Cotton were the worst performers in the
twisting test: both fabrics failed to slide at 35.degree. even
before twisting, and it was qualitatively observed that droplet
pinning worsens with further twisting. For those samples whose
sliding angles remain less than 35.degree., a clear difference
emerged between the SgB samples and the SiM samples: for the
SgB-treated samples, there is a significant increase in the sliding
angle for 0, 5, and 50 twists, while on the SiM treated samples
there is either no significant increase, or an initial increase
that stabilizes with additional twisting. The most telling result
comes from comparing SgB Nike PE with the SiM variant: the SgB
sample shows a clear, almost linear increase in the sliding angle
with increased number of twists, while the SiM sample shows no
significant change.
[0276] An increase in sliding angle indicates that damaged
nanostructures give rise to a decreased affinity of the lubricant
to the fiber surface either due to the loss of nanostructure or due
to cracks exposing surfaces that are not fluorinated. SiM fabrics
exhibit more durable nanostructures than SgB fabrics. SEM images of
the Nike PE fabric treated with both SgB and SiM, before and after
twisting, confirm this (see FIG. 34). The SiM layer on the Nike PE
fabric showed only minimal damage after 50 twists, whereas the
boehmite shows smoothening and flattening of its nanostructures.
Self-healing behavior arises in SLIPS from a redistribution of the
lubricant to cover moderate damage and to continue to provide
omniphobicity. In this way, the liquid-repellent performance of
SLIPS-fabrics is less susceptible to damage than that of TSH
fabrics. The extensive damage of the SgB fabrics diminishes
capillarity and therefore the lubricant's ability to redistribute.
This effect is not seen on the more durable SiM treatment. SiM Nike
PE maintained the same sliding angle throughout twisting and SgB
Nike PE experienced a continuous increase in sliding angle as the
nanostructures became critically damaged. Therefore, with respect
to robustness, lubricated SiM-treated fabrics show best
performance.
[0277] For additional durability characterization, non-lubricated
fabric samples were vigorously rubbed with a Kimwipe, qualitatively
observed the repellency, and characterized the surface with SEM
(see FIG. 34). Though the ability to repel water appears to remain
unaffected, SEM characterization reveals cracking damage on the
SgB-treated fabrics and no damage to the SiM-treated fabric (see
FIG. 34). Specifically, rubbing causes the alumina shell to crack
and detach from the fiber surface, in a fashion similar to the
twisting test. The adhesion of the sol-gel alumina to the fibers
was not fully optimized yet to provide sufficiently strong damage
tolerance against rubbing. In contrast, the silica microparticles
that are covalently attached to the fabric surface show strong
adherence between the silica shell and the fiber. Therefore
SiM-treated SLIPS-fabrics maintain omniphobic performance even when
subjected to abrasion. It was also observed that washing machine
cycles have little effect on the integrity of the nanostructures.
This further demonstrates that damage to the nanostructures can
lead to premature loss of the lubricant and creation of new pinning
points, reducing the functional lifetime of the fabric.
[0278] Given the results of the twisting and rubbing tests
described above, SiM-treated fabrics were selected for Phase III
testing. Specifically, M. Cotton, Dense PE, Nike PE, and .mu.fiber
were selected to complete the characterization of the SLIPS fabrics
and show the best overall performance. Water and hydrocarbon
resistance testing was performed to observe the repellency of
low-surface-tension fluids, and drop impact testing was performed
to determine the pressure tolerance of the fabrics, and water vapor
transmission testing was performed to characterize the fabric's
breathability.
[0279] For each of the Phase III fabrics, a SLIPS (lubricated)
sample was tested against a nonlubricated sample that serves as a
representative TSH control. Liquid droplets of progressively lower
surface tension (ranging from 72 mN/m for pure water to 24.0 mN/m
for 60% isopropyl alcohol) were applied to fabric samples until the
test droplet wets the surface. The scores for the four samples are
shown in Table 5.
TABLE-US-00005 TABLE 5 AATCC 193 Aqueous Liquid Repellency Score*
SiM Treatment - Sample SiM Treatment - dry lubricated M. Cotton 5
5.5 Dense PE 5.5 8 Nike PE 4 6.5 .mu.fiber 5 7
[0280] Clearly, the lubricated, SLIPS-fabric samples exhibit a
higher score than their non-lubricated, superhydrophobic
counterparts. In other words, the presence of the thin lubricating
film around the threads prevents penetration of low-surface-tension
liquids that would have otherwise wet the non-lubricated fabric.
The Dense PE achieved the maximum score of 8: 60% IPA in water did
not wet the sample and could slide off without pinning. M. cotton,
Nike PE, and .mu.fiber PE were capable of repelling aqueous liquids
down to surface tensions of 26.5, 25.0, and 24.5 mN/m,
respectively. A particularly interesting trend emerges from these
results: the scores for the SLIPS-fabric samples correlate with
increasingly tight weaves. M. Cotton has the loosest weave and
experiences the most pinning; Dense PE has the tightest weave and
thus performs the best. This trend may be attributable to the
overall smoothness of the SLIPS-fabric surface where even
sub-millimeter scale roughness can still slightly compromise the
ultrasmooth nature of lubricant-infused interface.
[0281] To extend the testing to organic liquids, the repellency of
the Phase III fabrics Were tested against mineral oils and alkanes
of progressively shorter chain length and lower surface tension.
Table 6 summarizes the hydrocarbon repellency scores for the Phase
III fabric samples.
TABLE-US-00006 TABLE 6 AATCC 118 Hydrocarbon Resistance Score* SiM
Treatment - Sample SiM Treatment - dry lubricated M. Cotton 2 5.5
Dense PE 3.5 8 Nike PE 5 7 .mu.fiber 4.5 6
[0282] All test organic droplets pinned to the TSH fabrics and
easily slid off of the lubricated, SLIPS-fabric samples. The TSH
samples, particularly the M. Cotton and Dense PE, generally
received lower scores than in the aqueous repellency test,
indicating that organic liquids with even lower surface tensions
are more prone to infiltrating the spaces within a fabric. Despite
this, the scores of the lubricated samples in both the hydrocarbon
and aqueous tests were within .+-.1 from each other and follow the
same trend of larger weave patterns causing reduced repellency of
low-surface-tension liquids. Again, the dense polyester sample
showed repellency to all of the test liquids and achieved the
highest possible score of 8. SLIPS-fabric of a sufficiently dense
weave can support a lubricating film that repels liquid compounds
of broad compositions, polarities and surface tensions, which is a
remarkable advancement to stain-resistant, fabric-based
materials.
[0283] In certain embodiments, fabrics having a weave density that
exceeds 100, 200, 300 and 400 threads/cm.sup.3 can be utilized. As
used herein, the weave density can be calculated by obtaining an
SEM image of a fabric, counting the number of threads horizontally
across the fabric, within an imaged area.
[0284] Another important advantage of a lubricated fabric is that
it maintains its slippery, omniphobic performance under pressure.
To assess the pressure stability of the Phase III fabric samples,
the drop impact test was carried out using water (surface
tension=72.4 mN/m) and tetradecane (surface tension=26.55 mN/m)
dropped from a height of 20.4 cm to achieve a dynamic pressure
shown by the circle markers shown in FIG. 38. The results for the
drop impact test are shown in FIG. 38: for a liquid of a given
surface tension, the sliding angle is determined immediately after
the droplet impacts the surface with the shown dynamic pressure.
The SiM-SLIPS Nike PE and Dense PE fabrics retain their liquid
repellency at high pressures (>1500 Pa) while typical lotus-type
TSH surfaces fail at 400 Pa. The sliding angle of the test liquids
on SiM-SLIPS treated .mu.fiber fabric increases after high impact,
however sliding is still observed. This indicates that there is a
SLIPS layer penetrated by the many protruding fibers on its
disordered surface. Sliding angles for non-lubricated samples are
not included because this pressure is above the threshold at which
the Cassie-to-Wenzel transition occurs; water droplets are strongly
pinned to the surface and will not slide even from the vertical
surfaces, while tetradecane droplets simply wet the fabric as
expected. SiM-SLIPS Nike PE shows sliding angles below 10.degree.
(10 .mu.L droplet) after a collisional pressure applied by the
falling test liquid, while un-lubricated SiM Nike PE shows
irreversible pinning in the same conditions. FIG. 38 shows that
liquids of different surface tensions and dynamic impact pressures
do not cause prominent increases in sliding angle of the SLIPS
fabrics. As could be expected based on tightness of fabric weave
and surface flatness, the Dense PE and Nike PE both show the best
performance in this test with post-impact sliding angles of
8.8.+-.1.0.degree. and 20.9.+-.2.0.degree.. The fiber showed an
increase of .about.10.degree. in sliding angle after impact
pressure due to the presence of loose fibers oriented approximately
normal to the surface of the fabric. It is worth noting that
despite droplet pinning the lubricated fabric was neither wet nor
stained by the test liquid and the pinned droplets could be easily
washed off the surface leaving no residue.
[0285] Breathability, or more specifically, water vapor
transmission rate (WVTR), is an important factor in determining
suitable applications for SLIPS fabrics. For each experiment, a
non-lubricated and a lubricated sample were tested alongside two
controls: a capsule sealed by (impermeable) Parafilm and an open
capsule. In all cases, the lubricated fabric showed a large
decrease in breathability relative to the non-lubricated samples.
Table 7 summarizes the WVTR mass change after 24 h for the fabrics
and PTFE controls.
TABLE-US-00007 TABLE 7 WVTR Material Lubrication (g/24
h/m{circumflex over ( )}2 Fold Change No Membrane* Control 947.5
.+-. 38.7 25.5 Parafilm* Control 37.2 .+-. 18.4 .mu.fiber* None
497.5 .+-. 61.4 11.1 .mu.fiber* K102 44.6 .+-. 6.8 Nike PE* None
507.5 .+-. 70.9 11.5 Nike PE* K102 44.2 .+-. 15.6 Dense PE* None
270.5 .+-. 36.6 6.1 Dense PE* K102 44.0 .+-. 22.4 M. Cotton* None
493.3 .+-. 17.1 3.5 M. Cotton* K102 139.4 .+-. 17.9 200 nm PTFE*
None 473.9 .+-. 35.8 11.3 200 nm PTFE* K102 42.0 .+-. 8.0 1 .mu.m
PTFE* None 470.9 .+-. 41.1 14.9 1 .mu.m PTFE* K102 31.6 .+-. 18.7
20 .mu.m PTFE* None 483.4 .+-. 49.0 14.1 20 .mu.m PTFE* K102 34.2
.+-. 19.6 Punc. 200 nm PTFE* None 460.5 .+-. 39.6 3.7 Punc. 200 nm
PTFE* K102 131.1 .+-. 76.0
[0286] All of the SLIPS samples (lubricated with Krytox 102) except
for M. Cotton did not show a statistically significant difference
in breathability from that of the Parafilm control. Non-lubricated
.mu.fiber, Nike PE, and Cotton samples exhibit similar
breathability despite large differences in their relative weave
pattern and weave density. Also, the .mu.fiber, Nike PE, and Dense
PE all show no breathability (i.e., no difference from the Parafilm
control) while Cotton, the least densely woven fabric, shows
significant (but still low) breathability. This intimates the
presence of a certain macro-scale pore size threshold above which
the Krytox does not wick across, leaving a space through which air
and water vapor can flow.
[0287] While lotus-effect superhydrophobic surfaces have been
thoroughly investigated for years and continue to show improvement,
their design has some fundamental shortcomings that will always
limit omniphobicity, stain resistance, durability and pressure
tolerance. SLIPS overcome these problems, and nanostructured
coatings that achieve the promising benefits using readily
available fabrics as a substrate have been engineered. The
lubricated structured surfaces display superior pressure-stable and
damage-tolerant repellency to polar and non-polar liquids as
compared to TSH surfaces. These lubricated nanostructure-coated
fabrics can repel water, oil, dirt and mud; therefore, tents,
boots, and other outerwear would be significantly improved. In
demanding applications in extreme, contaminated environments, where
breathability is not the most critical factor, SLIPS fabrics may
already provide a unique solution as a stable, anti-fouling
material for tactical suits for military, medical gowns and lab
coats, specialty garments for construction and manufacturing.
SLIPS-fabric confers pressure-tolerant and damage-tolerant
omniphobicity on fabric-based substrates.
[0288] Those skilled in the art would readily appreciate that all
parameters and configurations described herein are meant to be
exemplary and that actual parameters and configurations will depend
upon the specific application for which the systems and methods of
the present invention are used. Those skilled in the art will
recognize, or be able to ascertain using no more than routine
experimentation, many equivalents to the specific embodiments of
the invention described herein. It is, therefore, to be understood
that the foregoing embodiments are presented by way of example only
and that the invention may be practiced otherwise than as
specifically described. Accordingly, those skilled in the art would
recognize that the examples should not be limited as such. The
present invention is directed to each individual feature, system,
or method described herein. In addition, any combination of two or
more such features, systems or methods, if such features, systems
or methods are not mutually inconsistent, is included within the
scope of the present invention.
* * * * *
References