U.S. patent application number 14/186349 was filed with the patent office on 2015-08-27 for transparent omniphobic thin film articles.
The applicant listed for this patent is UT-BATTELLE, LLC. Invention is credited to Tolga Aytug.
Application Number | 20150239773 14/186349 |
Document ID | / |
Family ID | 53881564 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150239773 |
Kind Code |
A1 |
Aytug; Tolga |
August 27, 2015 |
TRANSPARENT OMNIPHOBIC THIN FILM ARTICLES
Abstract
An article having a nanostructured surface and a method of
making the same are described. The article can include a substrate
and a nanostructured layer bonded to the substrate. The
nanostructured layer can include a plurality of spaced apart
nanostructured features comprising a contiguous, protrusive
material and the nanostructured features can be sufficiently small
that the nanostructured layer is optically transparent. A surface
of the nanostructured features can be coated with a continuous
hydrophobic coating. The method can include providing a substrate;
depositing a film on the substrate; decomposing the film to form a
decomposed film; and etching the decomposed film to form the
nanostructured layer.
Inventors: |
Aytug; Tolga; (Knoxville,
TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UT-BATTELLE, LLC |
Oak Ridge |
TN |
US |
|
|
Family ID: |
53881564 |
Appl. No.: |
14/186349 |
Filed: |
February 21, 2014 |
Current U.S.
Class: |
428/312.6 ;
204/192.12; 216/56 |
Current CPC
Class: |
C03C 2218/33 20130101;
C23C 14/5873 20130101; Y10T 428/249969 20150401; C03C 17/008
20130101; C03C 2217/425 20130101; C03C 2217/452 20130101; C03C
2217/47 20130101; C03C 2218/154 20130101; C23C 14/35 20130101; C03C
11/005 20130101; C23C 14/5806 20130101; C23C 14/10 20130101 |
International
Class: |
C03C 15/00 20060101
C03C015/00; C23C 14/34 20060101 C23C014/34 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0001] This invention was made with government support under
contract No. DE-AC05-000R22725 awarded by the U.S. Department of
Energy. The government has certain rights in this invention.
Claims
1. A method comprising: applying a glass film to a substrate;
heating the glass film to a temperature and for a duration
sufficient to phase-separate the glass; differentially etching the
glass to create a porous interpenetrating structure; modifying a
surface chemistry of the porous interpenetrating structure; and
adding a lubricating fluid to at least one pore of the porous
interpenetrating structure.
2. The method according to claim 1, wherein the glass film is
applied to the substrate by one selected from the group consisting
of radio frequency (RF) sputtering, chemical vapor deposition
(CVD), metallorganic chemical vapor deposition (MOCVD), screen
printing, ink-jet printing, spray painting, plasma spraying, pulsed
laser ablation, sputtering, e-beam co-evaporation, wet solution
chemical deposition (sol-gel, dip-coating) approaches and
combinations thereof.
3. The method according to claim 1, wherein the glass film
comprises one selected from the group consisting of sodium
borosilicate glass, a soda lime glass, and combinations
thereof.
4. The method according to claim 1, wherein the temperature is from
500 to 800 degrees Celsius.
5. The method according to claim 1, wherein the duration is from 1
second to 5 days.
6. The method according to claim 1, wherein the temperature is
about 700 degrees Celsius and the duration is from 1 to 10
minutes.
7. The method according to claim 1, wherein the temperature is
about 500 degrees Celsius and the duration is from 3-5 days.
8. The method according to claim 1, wherein the differential
etching is performed using an etchant comprising one selected from
hydrogen fluoride, ammonium fluoride, and combinations thereof.
9. The method according to claim 1, wherein the porous
interpenetrating structure has a porosity of from 10% to 90% volume
percent.
10. The method according to claim 1, wherein the porous
interpenetrating structure comprises a plurality of pores having an
average pore diameter of from 10-200 nm.
11. The method according to claim 10, wherein the pore diameter
indicates a separation between peaks defining a perimeter of a
pore.
12. The method according to claim 1, wherein the porous
interpenetrating structure comprises a plurality of pores having an
average depth of from 10-200 nm.
13. The method according to claim 1, wherein the porous
interpenetrating structure comprises a continuous phase comprising
the glass film having pores randomly distributed throughout.
14. The method according to claim 1, wherein the porous
interpenetrating structure comprises a reticulated network
comprising glass film, having pores randomly distribute
throughout.
15. The method according to claim 1, wherein the surface chemistry
of the porous interpenetrating structure is one selected from the
group consisting of a degree of hydrophobicity, a degree of
oleophobicity, a degree of lipophobicity, and combinations
thereof.
16. The method according to claim 1, wherein the surface chemistry
of the porous interpenetrating structure is modified by applying a
surface chemistry modifying compound.
17. The method according to claim 16, wherein the surface chemistry
modifying compound is a fluorinated low surface energy material
selected from the group consisting of
1H,1H,2H,2H-perfluorooctyltrichlorosilane,
tridecafluoro-1,1,2,2-tetrahydrooctyl) trichlorosilane,
fluorosilanes, 5-trifluoromethylbenzyltrichlorosilane, and
combinations thereof.
18. The method according to claim 1, wherein the surface chemistry
of the porous interpenetrating structure is modified to correspond
with at least one property of the lubricating fluid.
19. The method according to claim 18, wherein the at least one
property of the lubricating fluid is one selected from the group
consisting of a degree of hydrophobicity, a degree of
oleophobicity, a degree of lipophobicity and combinations
thereof.
20. The method according to claim 18, wherein the property is the
surface energy of the lubricating oil.
21. The method according to claim 20, wherein the surface energy of
the surface chemistry modifying compound is from 10 to 20 mN/m.
22. The method according to claim 20, wherein the surface energy of
the surface chemistry modifying compound about 17 mN/m.
23. The method according to claim 1, wherein the lubricating fluid
is a perfluoropolyether oil.
24. The method according to claim 23, wherein the
perfluoropolyether oil has a number average molecular weight of
from 1000 to 10000 AMU.
25. The method according to claim 23, wherein the surface energy of
the lubricating oil is from 10 to 25 mN/m.
26. The method according to claim 23, wherein the surface energy of
the lubricating oil about 17 mN/m.
27. The method according to claim 1, wherein the lubricating fluid
has a surface energy that is within +/-1 mN/m of a surface energy
of the surface chemistry modifying compound.
28. The method according to claim 1, wherein the lubricating fluid
has a viscosity of from 1 to 2,500 cP.
29. The method according to claim 1, wherein the lubricating fluid
has a refractive index of from 1.2 to 1.4 at 20 degrees
Celsius.
30. The method according to claim 1, wherein the lubricating fluid
has a refractive index of about 1.296 degrees Celsius.
31. The method according to claim 1, wherein the lubricating fluid
has a vapor pressure of from 1.0.times.10.sup.-4 to
2.times.10.sup.-9 torr at 20 degrees Celsius.
32. The method according to claim 1, wherein the lubricating fluid
is applied by one selected from the group consisting of
spin-coating, soaking, dip-coating, spray-coating, injecting,
screen-printing, atomic layer deposition and combinations
thereof.
33. An article comprising a substrate; a glass film disposed on the
substrate, wherein the glass film has an interpenetrating
structure, comprising a plurality of pores; a lubricating fluid
disposed within the plurality of pores, wherein the
interpenetrating structure comprises at least one surface having a
modified surface chemistry that corresponds with at least one
property of the lubricating fluid, selected from the group
consisting of a degree of hydrophobicity, a degree of
oleophobicity, a degree of lipophobicity, and combinations
thereof.
34. The article according to claim 33, wherein the article exhibits
a sliding angle of from 0.1 to 4.5 degrees with respect to a 20
.mu.L drop of a liquid.
35. The article according to claim 34, wherein the liquid is
selected from water, a hydrocarbon and combinations.
36. The article according to claim 34, wherein the hydrocarbon is
hexane, octane, ethylene glycol.
37. The article according to claim 33, wherein the article exhibits
a contact angle hysteresis of from 0.4 to 4 with respect to a 20
.mu.L drop of a liquid, and wherein the contact angle hysteresis is
defined as a droplet advancing angle minus a receding angle.
38. The article according to claim 33, wherein the article has a
transmittance greater than 60% with respect to light having a
wavelength greater than 200 nm.
39. The article according to claim 33, wherein the article is
optically transparent.
Description
FIELD OF THE INVENTION
[0002] The present invention relates to articles with optically
transparent, nanostructured omniphobic surfaces.
BACKGROUND OF THE INVENTION
[0003] There are abundant uses for superhydrophobic materials,
including self-cleaning surfaces, anti-fouling surfaces and
anti-corrosion surfaces. Approaches for producing surfaces
exhibiting these properties include producing micro-nano textured
superhydrophobic surfaces or chemically active antimicrobial
surfaces. Despite the impressive properties achieved by such known
surfaces, the properties are not durable and the surfaces need to
be replaced or otherwise maintained frequently. Thus, research to
identify alternative approaches has continued.
[0004] An artificial surface that is transparent and antireflective
and that repels various liquids can have broad industrial
application potential ranging from self-cleaning architectural
windows and optical components to elimination of bio-adhesion and
icing on surfaces as well as patterned devices (e.g., complex
microfluidic devices) for liquid transportation, drug delivery and
medical diagnostics. Approaches for producing liquid repellent
surfaces exhibiting these properties include producing micro-nano
textured surfaces or chemically active antimicrobial surfaces.
Despite the impressive properties achieved by such surfaces, the
properties are either not durable or transparent, and the surfaces
need to be replaced or otherwise maintained frequently. Some
examples of the current state of the art for omniphobic surface
development is based on periodically ordered arrays of nanoposts
functionalized with low-surface energy polyfluoralkyl silane,
random network of Teflon nanofibres distributed thorough the bulk
substrate, UV-cured and fluorinated polyurethane, surfaces created
by colloidal templating, and randomly deposited polymer based
electro spun fiber mats and ordered arrays of silicon dioxide micro
caps. One way to achieve a durable liquid repellent surface, at the
same time exhibiting optical transparency, is to use certain phase
separating glasses that phase separates into a connected structure
(known as spinodal) when heat treated. These phase separated
structurally connected features scatter light due to the slight
differences in the phase's refractive indexes. This light
scattering is wavelength dependent and is known as Raleigh
scattering. When the spinodal structure features are small
(.about.100 nm) the glass primarily scatters ultraviolet light and
passes all other light, thus appearing transparent.
SUMMARY OF THE INVENTION
[0005] The invention includes an article having a nanostructured
surface. The article can include a substrate and a nanostructured
layer bonded to the substrate. The nanostructured layer can be
directly bonded to the substrate, i.e., without any adhesive or
intermediary layers. The nanostructured layer can be atomically
bonded to the substrate. The nanostructured layer can include a
plurality of spaced apart nanostructured features comprising a
contiguous, protrusive material. The nanostructured layer can
include an oil pinned in a plurality of nanopores formed by a
plurality of nanostructured features.
[0006] The nanostructured features can be sufficiently small so
that the nanostructured layer is optically transparent. The width,
length and height of each of said plurality of spaced apart
nanostructured features ranges from 1 to 500 nm.
[0007] A continuous hydrophobic coating can be disposed on the
plurality of spaced apart nanostructured features. The continuous
hydrophobic coating can include a self-assembled monolayer.
[0008] The plurality of spaced apart nanostructured features
provide an anti-reflective surface. The plurality of spaced apart
nanostructures features can provide an effective refractive index
gradient such that the effective refractive index increases
monotonically towards the substrate.
[0009] A method of forming the article with a nanostructured
surface layer is also described. The method can include providing a
substrate; depositing a film on the substrate; decomposing the film
to form a decomposed film; and etching the decomposed film to form
the nanostructured layer.
[0010] The decomposition step can be performed under a
non-oxidizing atmosphere. The decomposing step can include heating
the film to a sufficient temperature for a sufficient time to
produce a nanoscale spinodal decomposition.
[0011] The method can also include applying a continuous
hydrophobic coating to the plurality of spaced apart nanostructured
features, pinning an oil within nanopores formed by the plurality
of nanostructured features, or both.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] These and other features, aspects, and advantages of the
present invention will become better understood with reference to
the following description and appended claims, and accompanying
drawings where:
[0013] FIG. 1: is a schematic cross-section of an article with a
nanostructured layer.
[0014] FIGS. 2A-D: are schematic cross-sections of a method of
making an article with a nanostructure layer;
[0015] FIG. 3: is a schematic cross-section of a nanostructured
layer with oil pinned within the nanopores of the nanostructured
layer;
[0016] FIG. 4: is a schematic cross-section showing oil pinned
within a nanopore;
[0017] FIG. 5: is an SEM image of nanostructured features as
described herein (1 micron scale);
[0018] FIG. 6: is an SEM image of nanostructured features as
described herein (2 micron scale);
[0019] FIG. 7: is a schematic illustration of a method for testing
the contact angle hysteresis of a drop of liquid on a
substrate;
[0020] FIG. 8: is a chart plotting contact angle hysteresis
measurements against liquid surface tension for films prepared
according to Example 2, tested with a variety of fluids each having
a different surface tension;
[0021] FIG. 9: is a chart plotting sliding angle against liquid
surface tension for films prepared according to Example 3, tested
with a variety of fluids each having a different surface
tension;
[0022] FIGS. 10a-e: show frames of a video of a drop of
polyethylene glycol sliding across the surface of the glass
film;
[0023] FIGS. 11a-e: show frames of a video of a drop of octane
sliding across the surface of the glass film;
[0024] FIGS. 12a-e: show frames of a video of a drop of water
sliding across the surface of the glass film;
[0025] FIGS. 13a-e: show frames of a video of a side-by-side
comparison of a first drop of water sliding across the surface of a
first glass film and a second drop of water sliding across the
surface of a second glass film; and
[0026] FIG. 14: is a chart plotting transmittance against
wavelength for a variety of glass films.
[0027] It should be understood that the various embodiments are not
limited to the arrangements and instrumentality shown in the
drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The present invention may be understood more readily by
reference to the following detailed description of preferred
embodiments of the invention as well as to the examples included
therein. All numeric values are herein assumed to be modified by
the term "about," whether or not explicitly indicated. The term
"about" generally refers to a range of numbers that one of skill in
the art would consider equivalent to the recited value (i.e.,
having the same function or result). In many instances, the term
"about" may include numbers that are rounded to the nearest
significant figure.
[0029] U.S. patent application Ser. No. 12/915,183, filed Oct. 29,
2010, titled "Superhydrophobic Transparent Glass (STG) Thin Film
Articles," which was a continuation in part of U.S. patent
application Ser. No. 12/901,072, filed Oct. 8, 2010, titled
"Superoleophilic Particles and Coatings and Methods of Making the
Same," which issued as U.S. Pat. No. 8,497,021 on Jul. 30, 2013, is
incorporated herein by reference in its entirety.
[0030] A substrate including a superhydrophobic transparent glass
thin film and method of making the same are described. The glass
thin film is applied in such a manner that it is possible to
deposit thin films on a variety of substrates. The glass thin film
can be superhydrophobic, self-cleaning, anti-reflective across the
visible light spectrum, the IR spectrum, or both, while blocking,
i.e., reflecting or scattering, UV radiation.
[0031] As shown in the Figures, the articles 10 with nanostructures
surfaces described herein can include a substrate 12 and a
nanostructured layer 14 attached to the substrate 12. The
nanostructured layer 14 can include a plurality of spaced apart
nanostructured features 16 comprising a contiguous, protrusive
material 18 and the nanostructured features 16 can be sufficiently
small that the nanostructured layer 14 is optically transparent.
The nanostructured layer 14 can include a plurality of nanopores 20
defined by the contiguous, protrusive material 18, e.g., the
nanostructured features 16.
[0032] As used herein, "optically transparent" refers to a material
or layer that transmits rays of visible light in such a way that
the human eye may see through the glass distinctly. One definition
of optically transparent is a maximum of 50% attenuation at a
wavelength of 550 nm (green light) for a material or layer, e.g., a
layer 1 .mu.m thick. Another definition can be based on the Strehl
Ratio, which ranges from 0 to 1, with 1 being a perfectly
transparent material. Exemplary optically transparent materials can
have a Strehl Ratio.gtoreq.0.5, or a Strehl Ratio.gtoreq.0.6, or a
Strehl Ratio.gtoreq.0.7, or a Strehl Ratio.gtoreq.0.8, or a Strehl
Ratio.gtoreq.0.9, or a Strehl Ratio.gtoreq.0.95, or a Strehl
Ratio.gtoreq.0.975, or a Strehl Ratio.gtoreq.0.99.
[0033] As used herein, the term "nanopores" refers to pores with a
major diameter ranging from 1 to 750 nm. Nanopores can also refer
to pores having a major diameter ranging from 5 to 500 nm, or 10 to
400 nm, or any combination thereof, e.g., 400 to 750 nm. The
nanostructured layer described herein can have a nanopore size
ranging from 10 nm to about 10 .mu.m, or 100 nm to 8 .mu.m, or 500
nm to 6 .mu.m, or 1 to 5 .mu.m, or any combination thereof, e.g.,
500 nm to 5 .mu.m.
[0034] The nanostructures features formed from a contiguous,
protrusive material described herein can be formed by
differentially etching of spinodally decomposed materials as
described in U.S. Pat. No. 7,258,731, "Composite, Nanostructured,
Super-Hydrophobic Material", issued to D'Urso et al., on Aug. 21,
2007; U.S. Patent Application Publication No. 2008/0286556,
"Super-Hydrophobic Water Repellant Powder," published Nov. 20,
2008; and U.S. patent application Ser. No. 12/901,072,
"Superoleophilic Particles and Coatings and Methods of Making the
Same," (hereinafter "Differential Etching References") filed Oct.
8, 2010, the entireties of which are incorporated by reference
herein.
[0035] As used herein, nanostructured feature has its literal
meaning and includes, but is not limited to, nanoscale protrusions
and nanoscale branched networks. As used herein, "nanoscale
branched network" refers to a branched network where the individual
branches are less than 1 .mu.m. In some examples, the branches of
the nanoscale branched networks described herein can be 750 nm or
less in length, or 600 nm or less in length, or 500 nm or less in
length. A branch can be defined by the space (i) between adjacent
junctions 22, (ii) between a junction 22 and a terminal end 24 of
the network, i.e., a nanoscale protrusion, or (iii) both. As shown
in FIG. 3, the length (L) of a branch can be measured as the
distance (i) between adjacent junctions 22, (ii) between a junction
22 and a terminal end 24 of the network, i.e., a nanoscale
protrusion, or (iii) both. Though not a nanoscale branched network,
staghorn coral (A. cervicornis) would be considered an exemplary
branched network. In addition, FIGS. 5 & 6 show an SEM image of
an exemplary nanoscale branched network formed by differential
etching of a specially treated spinodally decomposed glass
substrate.
[0036] The width, length and height of each of the plurality of
spaced apart nanostructured features 16 can independently range
from 1 to 500 nm, or from 2 to 400, or from 3 to 300 nm, or from 4
to 250 nm, or from 5 to 200 nm, or any combination of these ranges,
e.g., 1 to 200 nm. The width, length and height of each of the
plurality of spaced apart nanostructures features can be at least 5
nm, at least 7 nm, at least 10 nm, or at least 20 nm.
[0037] The nanostructured layer 14 can also include an etching
residue disposed on the contiguous, protrusive material. As will be
understood, the etching residue can result from the differential
etching process utilized to remove the boron-rich phase of a
spinodally decomposed borosilicate layer 26, which is an
intermediate product of the spinodal decomposition described in the
Differential Etching References referenced above. Thus, the etching
residue can include remnants of the recessive contiguous material
that was interpenetrating with the protruding material in the
spinodally decomposed film 26 intermediary. The etching residue can
be contiguous or non-contiguous.
[0038] The formation of the nanostructured layer 14 can include an
intermediate spinodally decomposed glass film 26 formed from a film
28 selected from the group that includes, but is not limited to, a
sodium borosilicate glass and a soda lime glass. An exemplary
sodium borosilicate glass can include 65.9 wt-% SiO.sub.2, 26.3
wt-% B.sub.2O.sub.3 and 7.8 wt-% Na.sub.2O. The soda lime glass can
be any soda lime glass that can be spinodally decomposed and etched
to form the nanostructured layer described herein. The protrusive
material (e.g., silica-rich phase), the recessive material (e.g.,
alkali and/or borate-rich phase) or both can be glass.
[0039] The contiguous, protrusive material can be directly bonded
to the substrate 12. In some exemplary articles, the contiguous,
protrusive material can be atomically, i.e., covalently, bonded to
the substrate 12. For example, where the substrate 12 is a
silica-rich glass and the nanostructured layer 14 is formed from
differential etching of a spinodally decomposed sodium borosilicate
glass 26, the silica-rich contiguous, protrusive phase of the
nanostructured layer 14 can be covalently bonded to the substrate
12. In fact, in some cases, the composition of the substrate 12 and
the contiguous, protrusive phase of the nanostructured layer 14 can
be the same. This can result in a structure where there is no clear
interfacial delineation between the nanostructured layer 14 and the
substrate 12.
[0040] In some other examples, the contiguous, protrusive material
of the nanostructured layer 14 can be directly bonded to the
surface 30 of the substrate 12 by a means other than covalent
bonding. In other words, the bond between the substrate 12 and the
contiguous, protrusive material 18 can be formed directly without
reliance on an adhesive or interfacial material to join the
contiguous, protrusive material 18 to the surface 30 of the
substrate 12. Such a process could involve interfacial atomic or
molecular interdiffusion due to high impact velocities or
temperature of deposited species. For example, during physical
vapor deposition, target source species arrive at the substrate
with high kinetic energy and with various angles of incidence.
Because of this, highly dense films with exceptional adherence and
coverage can be obtained, even on irregular surfaces. This direct
bonding can result from the method of deposition of the precursor
to the nanostructured layer, e.g., a physical or chemical vapor
deposition technique.
[0041] Again, one embodiment relates to a method including applying
a glass film to a substrate; heating the glass film to a
temperature and for a duration sufficient to phase-separate the
glass; differentially etching the glass to create a porous
interpenetrating structure; modifying a surface chemistry of the
porous interpenetrating structure; and adding a lubricating fluid
to at least one pore of the porous interpenetrating structure. The
glass film can be applied to the substrate by radio frequency (RF)
sputtering, chemical vapor deposition (CVD), metallorganic chemical
vapor deposition (MOCVD), wet chemical solution based approaches
such as sol-gel and dip-coating, screen printing, ink-jet printing,
spray painting, plasma spraying, pulsed laser ablation, sputtering,
e-beam co-evaporation, and combinations thereof.
[0042] Various embodiments relate to a method of producing durable,
transparent, antireflective, and omniphobic (i.e., repels various
liquids) glass thin films. The basic approach to make such films is
to begin with phase separating glass that is capable of spinodally
decomposing when properly processed. In principle, a variety of
different phase separating glasses (e.g. soda lime, borosilicate)
can be applied to various existing surfaces (e.g. eye glasses,
goggles, windows, metals, etc.), in a variety of ways (e.g. RF
sputtering, Chemical Vapor Deposition (CVD), screen printing,
ink-jet printing, spray painting, plasma spray, etc.). Once the
coating has been applied and phased separated (typically by heat
treating) into a spinodal pattern, a certain amount of differential
etching is required in order to remove one phase and partially
remove another phase of the spinodal structure. The resulting
etched surface structure has a very porous and interpenetrating
structure. This reticulated porous surface can be used as a matrix
to effectively lock-in place a lubricating fluid having a low
surface energy (e.g., perfluoropolyether oil, .gamma..about.17
mN/m) with different viscosities. In order to effectively infuse
the lubricant into the porous film matrix, in the final step the
surface chemistry of nanostructured porous surface can be changed
to match the chemical nature of the lubricant. After application of
the lubricant the surface enable omniphobic repellency for liquids
with surface tensions ranging from .gamma.=18.2 mN/m (hexane) to
72.8 mN/m (water). The invented nanostructured omniphobic glass
coating is first treated with
1H,1H,2H,2H-perfluorooctyltrichlorosilane and then the lubricating
liquid, Fomblin 16/6 oil, is applied onto the fluorinated surface
via spin-coating at 1000 rpm for a duration of 30 sec. The
mechanical durability of the porous nanostructure is established
during the deposition of the phase separating glass film onto
various glass platforms and the interpenetrating porous network
along with proper chemical affinity of the surface ensures the
effective wetting and infusion of the lubricant. In addition, the
fluidic nature of the lubricant combined with the nanostructured
surface features enable to heal the physical damage by simply
filling the damaged regions by the lubricant via capillary action.
Moreover, the tunability of the nanostructural features as well as
the porosity can easily be used to tailor the optical properties of
the coatings for specific applications and the patternability of
the film matrix through manipulating the etching protocols will
create complex surface designs of selective liquid repellency in
microfluidic applications.
[0043] The plurality of spaced apart nanostructured features 16 can
cause the nanostructured layer 14 to exhibit anti-reflective
properties. In some examples, the plurality of spaced apart
nanostructures features can produce an effective refractive index
gradient, wherein the effective refractive index gradient increases
monotonically towards the surface of the substrate.
[0044] Optical glass ordinarily reflects about 4% of incident
visible light from each of its surface (i.e., total of 8%
transmittance loss front and back surface combined). The
nanostructured layers 14 described herein can provide
anti-reflective properties in addition to hydrophobic and
transparent properties. As used herein, anti-reflective refers
to<1% reflection, and preferably<0.1% for normally incident
visible light (e.g., wavelengths from approximately 380-750
nm).
[0045] The nanostructured layer 14 described herein in general will
have two "interfaces," i.e., an air-layer interface 32 and a
layer-substrate interface 34, and a thickness (t). If the
nanostructured layer has optically small features (<200 nm
features) that are homogeneously distributed throughout the layer,
then interfaces 32, 34 will reflect a certain amount of light. If
the air-layer reflection 32 returns to the surface 30 such that it
is of equal amplitude and out of phase with the layer-substrate
interface reflection 34, the two reflections completely cancel
(destructive interference) and the nanostructured layer 14 will be
antireflective for that wavelength. The thickness (t) of the
nanostructured layer 14 determines the reflected phase
relationships while the optical indexes of refraction determine the
reflective amplitudes.
[0046] In order to exhibit anti-reflective properties, the length
(L) of the nanostructured features 16 is preferably about 1/4 of
the wavelength (.lamda./4) of the relevant light, such as about 140
nm for green light, which has a wavelength range of approximately
495-570 nm. The nanostructured layer 14 can have an effective
optical index of refraction and its thickness (t) can be adjusted
by the etch duration to obtain the correct thickness to produce an
antireflective surface. For example, for a nanostructured layer 14
formed from sodium borosilicate glass, the refractive index to
provide anti-reflectivity should be on the order of
[(nf.sub.air+nf.sub.glass)/(nf.sub.glsass-nf.sub.air)].sup.1/2=about
1.22 for a nf.sub.glass=1.5.
[0047] Alternately, the use of diffusion limited differential
etching of the spinodally decomposed nanostructured layer can be
used to produce a variable porosity graded index of refraction
layer 14. Finally, an anti-reflective surface can be created by
applying a coating that provides a graded index of refraction. The
nanostructured layer 14 will generally have an effective reflective
index gradient.
[0048] In some examples, with increasing duration of etching there
will be little or no etching of the decomposed layer 26 at the
layer-substrate interface 34, while preferably, the porosity of the
nanostructures layer 14 increases greatly approaching the layer-air
interface 32. In fact, the porosity and resulting layer index of
refraction would approach that of air (.about.1.01) near the
layer-air interface 32. This reflective index gradient can provide
broad spectrum anti-reflective properties. As used herein,
"broad-spectrum antireflective properties" refers to
anti-reflectivity across a wavelength range of at least 150 nm of
the visible and/or infrared light spectrum, at least 200 nm of the
visible and/or infrared light spectrum, at least 250 nm of the
visible and/or infrared light spectrum, at least 300 nm of the
visible and/or infrared light spectrum, or at least 350 nm of the
visible and/or infrared light spectrum. Based on the range
described above, it will be understood that the visible and
infrared light spectrum includes a range of 1120 nm, i.e., from 380
to 1500 nm.
[0049] Relying on the same principles, the nanostructured layer 14
can be tailored to exhibit UV blocking properties. As used herein,
"UV radiation" refers to radiation with a wavelength ranging from
10-400 nm. For example, the nanostructured layer can block or
reflect at least 80% of UV radiation, at least 85% of UV radiation,
at least 90% of UV radiation, at least 95% of UV radiation, at
least 97.5% of UV radiation, at least 99% of UV radiation, or at
least 99.5% of UV radiation.
[0050] The nanostructured layer 14 can have a thickness (t) of 2000
nm or less, 1000 nm or less, or 500 nm or less. The nanostructured
layer can have a thickness of at least 1 nm, at least 5 nm, at
least 10 nm, at least 15 nm, or at least 20 nm.
[0051] The nanostructured layer 14 itself can be superhydrophobic
when the surface 38 of the nanostructured features 16 are
hydrophobic or are made hydrophobic, e.g., through application of a
hydrophobic coating. This can be achieved by applying a fluorinated
silane solution to the nanostructured layer 14 in order to create a
hydrophobic monolayer on the surface 38 of the nanostructured layer
14. Accordingly, one method of making the nanostructured layer 14
superhydrophobic would be to apply a continuous hydrophobic coating
36 on a surface 38 of the plurality of spaced apart nanostructured
features 16. As used herein, "superhydrophobic" refers to materials
that exhibit contact angle with water of greater than 140.degree.,
greater than 150.degree., greater than 160.degree., or even greater
than 170.degree..
[0052] The continuous hydrophobic coating 36 can be a
self-assembled monolayer (SAM). As described in the referenced
patent applications, the nanostructured layer 14 will be
superhydrophobic only after a hydrophobic coating layer 36 is
applied thereto. Prior to application of the hydrophobic coating
36, the uncoated nanostructured layer will generally be
hydrophilic. The hydrophobic coating layer 36 can be a
perfluorinated organic material, a self-assembled monolayer, or
both. Methods and materials for applying the hydrophobic coating,
whether as a self-assembled monolayer or not, are fully described
in the U.S. patent applications referenced hereinabove.
[0053] As shown schematically in FIG. 4, the hydrophobic coating 36
can be continuously coated over the spaced apart nanostructured
features 16. The coating 36 can be formed as a self-assembled
monolayer. Self-assembled monolayers (SAMs) are coatings consisting
of a single layer of molecules on a surface, such as a surface 38
of the nanostructured features 16. In a SAM, the molecules are
arranged in a manner where a head group is directed toward or
adhered to the surface, generally by the formation of at least one
covalent bond, and a tail group is directed to the air interface to
provide desired surface properties, such as hydrophobicity. As the
hydrophobic tail group has the lower surface energy it dominates
the air-surface interface providing a continuous surface of the
tail groups.
[0054] Although SAM methods are described, it will be understood
that alternate surface treatment techniques can be used. Additional
exemplary surface treatment techniques include, but are not limited
to, SAM; physical vapor deposition, e.g., sputtering, pulsed laser
deposition, e-beam co-evaporation, and molecular beam epitaxy;
chemical vapor deposition; and alternate chemical solution
techniques.
[0055] SAMs useful in the instant invention can be prepared by
adding a melt or solution of the desired SAM precursor onto the
nanostructured layer 14 where a sufficient concentration of SAM
precursor is present to produce a continuous conformal monolayer
coating 36. After the hydrophobic SAM is formed and fixed to the
surface 38 of the nanostructured layer 14, any excess precursor can
be removed as a volatile or by washing. In this manner the SAM-air
interface can be primarily or exclusively dominated by the
hydrophobic moiety.
[0056] One example of a SAM precursor that can be useful for the
compositions and methods described herein is
tridecafluoro-1,1,2,2-tetrahydroctyltriclorosilane. In some
instances, this molecule undergoes condensation with the silanol
groups of the nanostructured layer, which releases HCl and
covalently bonds the tridecafluoro-1,1,2,2-tetrahydroctylsilyls
group to the silanols at the surface of the porous particle. The
tridecafluorohexyl moiety of the
tridecafluoro-1,1,2,2-tetrahydroctylsilyl groups attached to the
surface of the nanostructured layer provides a monomolecular layer
that has a hydrophobicity similar to polytetrafluoroethylene. Thus,
such SAMs make it possible to produce a nanostructured layer 14
having hydrophobic surfaces while retaining the desired
nanostructured morphology that produces the desired
superhydrophobic properties.
[0057] A non-exclusive list of exemplary SAM precursors that can be
used for various embodiments of the invention is:
X.sub.y(CH.sub.3).sub.(3-y)SiLR
[0058] where y=1 to 3; X is Cl, Br, I, H, HO, R'HN, R'.sub.2N,
imidizolo, R'C(O)N(H), R'C(O)N(R''), R'O, F.sub.3CC(O)N(H),
F.sub.3CC(O)N(CH.sub.3), or F.sub.3S(O).sub.2O, where R' is a
straight or branched chain hydrocarbon of 1 to 4 carbons and R'' is
methyl or ethyl; L, a linking group, is CH.sub.2CH.sub.2,
CH.sub.2CH.sub.2CH.sub.2, CH.sub.2CH.sub.2O,
CH.sub.2CH.sub.2CH.sub.2O, CH.sub.2CH.sub.2C(O),
CH.sub.2CH.sub.2CH.sub.2C(O), CH.sub.2CH.sub.2OCH.sub.2,
CH.sub.2CH.sub.2CH.sub.2OCH.sub.2; and R is
(CF.sub.2).sub.nCF.sub.3 or
(CF(CF.sub.3)OCF.sub.2).sub.nCF.sub.2CF.sub.3, where n is 0 to 24.
Preferred SAM precursors have y=3 and are commonly referred to as
silane coupling agents. These SAM precursors can attach to multiple
OH groups on the surface and can link together with the consumption
of water, either residual on the surface, formed by condensation
with the surface, or added before, during or after the deposition
of the SAM precursor. All SAM precursors yield a most
thermodynamically stable structure where the hydrophobic moiety of
the molecule is extended from the surface and establish normal
conformational populations which permit the hydrophobic moiety of
the SAM to dominate the air interface. In general, the
hydrophobicity of the SAM surface increases with the value of n for
the hydrophobic moiety, although in most cases sufficiently high
hydrophobic properties are achieved when n is about 4 or greater
where the SAM air interface is dominated by the hydrophobic moiety.
The precursor can be a single molecule or a mixture of molecules
with different values of n for the perfluorinated moiety. When the
precursor is a mixture of molecules it is preferable that the
molecular weight distribution is narrow, typically a Poisson
distribution or a more narrow distribution.
[0059] The SAM precursor can have a non-fluorinated hydrophobic
moiety as long as the SAM precursor readily conforms to the
nanostructured features 16 of the nanostructured layer 14 and
exhibits a sufficiently low surface energy to exhibit the desired
hydrophobic properties. Although fluorinated SAM precursors may be
preferred, in some embodiments of the invention silicones and
hydrocarbon equivalents for the R groups of the fluorinated SAM
precursors above can be used. Additional details regarding SAM
precursors and methodologies can be found in the patent
applications that have been incorporated herein by reference.
[0060] Again, one embodiment relates to a method including applying
a glass film to a substrate; heating the glass film to a
temperature and for a duration sufficient to phase-separate the
glass; differentially etching the glass to create a porous
interpenetrating structure; modifying a surface chemistry of the
porous interpenetrating structure; and adding a lubricating fluid
to at least one pore of the porous interpenetrating structure.
[0061] The surface chemistry of the porous interpenetrating
structure can be modified to correspond with at least one property
of the lubricating fluid. The surface chemistry of the porous
interpenetrating structure can be a degree of hydrophobicity, a
degree of oleophobicity, a degree of lipophobicity, and
combinations thereof.
[0062] The surface chemistry of the porous interpenetrating
structure can be modified by applying a surface chemistry modifying
compound. The surface chemistry modifying compound is
1H,1H,2H,2H-perfluorooctyltrichlorosilane.
[0063] The at least one property of the lubricating fluid can be a
degree of hydrophobicity, a degree of oleophobicity, a degree of
lipophobicity, and combinations thereof. The property can be the
surface energy of the lubricating oil. The surface energy of the
surface chemistry modifying compound can be within a range having a
lower limit and/or an upper limit. The range can include or exclude
the lower limit and/or the upper limit. The lower limit and/or
upper limit can be selected from 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6,
5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7,
7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4,
8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8,
9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11,
11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12, 12.1,
12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13, 13.1, 13.2,
13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14, 14.1, 14.2, 14.3,
14.4, 14.5, 14.6, 14.7, 14.8, 14.9, 15, 15.1, 15.2, 15.3, 15.4,
15.5, 15.6, 15.7, 15.8, 15.9, 16, 16.1, 16.2, 16.3, 16.4, 16.5,
16.6, 16.7, 16.8, 16.9, 17, 17.1, 17.2, 17.3, 17.4, 17.5, 17.6,
17.7, 17.8, 17.9, 18, 18.1, 18.2, 18.3, 18.4, 18.5, 18.6, 18.7,
18.8, 18.9, 19, 19.1, 19.2, 19.3, 19.4, 19.5, 19.6, 19.7, 19.8,
19.9, 20, 20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7, 20.8, 20.9, 21,
21.1, 21.2, 21.3, 21.4, 21.5, 21.6, 21.7, 21.8, 21.9, 22, 22.1,
22.2, 22.3, 22.4, 22.5, 22.6, 22.7, 22.8, 22.9, 23, 23.1, 23.2,
23.3, 23.4, 23.5, 23.6, 23.7, 23.8, 23.9, 24, 24.1, 24.2, 24.3,
24.4, 24.5, 24.6, 24.7, 24.8, 24.9, and 25 mN/m. For example,
according to certain preferred embodiments, the surface energy of
the surface chemistry modifying compound can be from 10 to 20 mN/m.
According to other preferred embodiments, the surface energy of the
surface chemistry modifying compound can be about 17 mN/m.
[0064] That article 10 can also, optionally, include an oil 40
pinned in the plurality of nanopores 20 formed by the plurality of
nanostructured features 16. The oil 40 pinned by and/or within the
nanopores 20 can be a non-nutritional oil. As used herein, the term
"non-nutritional" is used to refer to oils that are not consumed as
a nutrient source by microbes, e.g., bacteria, fungus, etc., or
other living organisms. Exemplary non-nutritional oils include, but
are not limited to polysiloxanes.
[0065] As used herein, "pinned" refers to being held in place by
surface tension forces, van der Waal forces (e.g., suction), or
combinations of both. For example, the interactions that prevent a
liquid from being dispensed from a laboratory pipette until the
plunger is depressed could be referred to as pinning.
[0066] As used herein, "oil" is intended to refer to a non-polar
fluid that is a stable, non-volatile, liquid at room temperature,
e.g., 23-28.degree. C. The oils used herein should be
incompressible and have no solubility or only trace solubility in
water, e.g., a solubility of 0.01 g/l or 0.001 g/l or less.
Exemplary oils include non-volatile linear and branched alkanes,
alkenes and alkynes, esters of linear and branched alkanes, alkenes
and alkynes; polysiloxanes, and combinations thereof.
[0067] The oil 40 can be pinned in all or substantially all of the
nanopores and/or surface nanopores of the nanostructured layer 14.
For example, oil 40 can be pinned in at least 70%, at least 80%, at
least 90%, at least 95%, at least 97.5%, or at least 99% of the
nanopores and/or surface nanopores of the nanostructured layer 14
described herein. The oil 40 pinned within the nanostructured layer
14 can be a contiguous oil phase. Alternately, the superoleophilic
layer 14 described herein can include an inner air phase with an
oil phase at the air-nanostructured layer interface 32.
[0068] In order to maintain the superoleophilic properties for an
extended duration, it can be desirable that the oil 40 pinned in
the nanostructured layer 14 does not evaporate when the article 10
is exposed to the use environment. For example, the oil 40 can be
an oil 40 that does not evaporate at ambient environmental
conditions. An exemplary oil 40 can have a boiling point of at
least 120.degree. C., or at least 135.degree. C., or at least
150.degree. C. or at least 175.degree. C.
[0069] As used herein, "ambient environmental conditions" refer
generally to naturally occurring terrestrial or aquatic conditions
to which superoleophilic materials may be exposed. For example,
submerged in lakes, rivers and oceans around the world, and adhered
to manmade structures around the world. Exemplary ambient
environmental conditions include (i) a temperature range from
-40.degree. C. to 45.degree. C. at a pressure of one atmosphere,
and (ii) standard temperature and pressure.
[0070] Again, one embodiment relates to a method including applying
a glass film to a substrate; heating the glass film to a
temperature and for a duration sufficient to phase-separate the
glass; differentially etching the glass to create a porous
interpenetrating structure; modifying a surface chemistry of the
porous interpenetrating structure; and adding a lubricating fluid
to at least one pore of the porous interpenetrating structure. The
lubricating fluid can be a perfluoropolyether oil. The lubricating
fluid can be any prefluorinated liquids such as perfluoro-octane
(surface tension 14 mN/m at 20 degrees Celsius) or any
fluorocarbon-based fluid such as FLUORINERT.TM. available from 3M
(FC-770, Surface tension 15 mN/m). Both are as vicous as water with
viscosities close to 1 cP. The perfluoropolyether oil can have a
number average molecular weight within a range having a lower limit
and/or an upper limit. The range can include or exclude the lower
limit and/or the upper limit. The lower limit and/or upper limit
can be selected from 1000, 1100, 1200, 1300, 1400, 1500, 1600,
1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700,
2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800,
3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900,
5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, 6000,
6100, 6200, 6300, 6400, 6500, 6600, 6700, 6800, 6900, 7000, 7100,
7200, 7300, 7400, 7500, 7600, 7700, 7800, 7900, 8000, 8100, 8200,
8300, 8400, 8500, 8600, 8700, 8800, 8900, 9000, 9100, 9200, 9300,
9400, 9500, 9600, 9700, 9800, 9900, and 10000 AMU. For example,
according to certain preferred embodiments, the perfluoropolyether
oil can have a number average molecular weight of from 1000 to
10000 AMU.
[0071] The surface energy of the lubricating oil can be within a
range having a lower limit and/or an upper limit. The range can
include or exclude the lower limit and/or the upper limit. The
lower limit and/or upper limit can be selected from 5, 5.1, 5.2,
5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6,
6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8,
8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4,
9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6,
10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7,
11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8,
12.9, 13, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14,
4.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, 15, 5.1, 15.2,
5.3, 5.4, 15.5, 15.6, 15.7, 15.8, 15.9, 16, 16.1, 16.2, 16.3, 16.4,
16.5, 16.6, 16.7, 16.8, 16.9, 17, 7.1, 17.2, 17.3, 17.4, 17.5,
17.6, 17.7, 17.8, 17.9, 18, 8.1, 18.2, 8.3, 8.4, 18.5, 18.6, 18.7,
18.8, 18.9, 19, 19.1, 19.2, 19.3, 19.4, 19.5, 19.6, 19.7, 19.8,
19.9, 20, 20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7, 20.8, 20.9, 21,
21.1, 21.2, 21.3, 21.4, 21.5, 21.6, 21.7, 21.8, 21.9, 22, 22.1,
22.2, 22.3, 22.4, 22.5, 22.6, 22.7, 22.8, 22.9, 23, 23.1, 23.2,
23.3, 23.4, 23.5, 23.6, 23.7, 23.8, 23.9, 24, 24.1, 24.2, 24.3,
24.4, 24.5, 24.6, 24.7, 24.8, 24.9, 25, 25.1, 25.2, 25.3, 25.4,
25.5, 25.6, 25.7, 25.8, 25.9, 26, 26.1, 26.2, 26.3, 26.4, 26.5,
26.6, 26.7, 26.8, 26.9, 27, 27.1, 27.2, 27.3, 27.4, 27.5, 27.6,
27.7, 27.8, 27.9, 28, 28.1, 28.2, 28.3, 28.4, 28.5, 28.6, 28.7,
28.8, 28.9, 29, 29.1, 29.2, 29.3, 29.4, 29.5, 29.6, 29.7, 29.8,
29.9, and 30 mN/m. For example, according to certain preferred
embodiments, the surface energy of the lubricating oil can be from
10 to 25 mN/m. The surface energy of the lubricating oil can be
about 17 mN/m.
[0072] The lubricating fluid can have a surface energy that is
within +/-0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2,
1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6,
2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4,
4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, and 5 mN/m of a
surface energy of the surface chemistry modifying compound. For
example, according to certain preferred embodiments, the
lubricating fluid can have a surface energy that is within +/-1
mN/m of a surface energy of the surface chemistry modifying
compound.
[0073] The lubricating fluid can have a viscosity within a range
having a lower limit and/or an upper limit. The range can include
or exclude the lower limit and/or the upper limit. The lower limit
and/or upper limit can be selected from 1, 5, 10, 100, 200, 300,
400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500,
1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, and 2500 cP.
For example, according to certain preferred embodiments, the
lubricating fluid can have a viscosity of from 1 to 2,500 cP.
[0074] The lubricating fluid can have a refractive index within a
range having a lower limit and/or an upper limit. The range can
include or exclude the lower limit and/or the upper limit. The
lower limit and/or upper limit can be selected from 0.1, 0.2, 0.3,
0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7,
1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1,
3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5,
4.6, 4.7, 4.8, 4.9, and 5 degrees Celsius. For example, according
to certain preferred embodiments, the lubricating fluid can have a
refractive index of from 1.2 to 1.4 at 20 degrees Celsius.
[0075] The lubricating fluid can have a refractive index within a
range having a lower limit and/or an upper limit. The range can
include or exclude the lower limit and/or the upper limit. The
lower limit and/or upper limit can be selected from 1.2, 1.201,
1.202, 1.203, 1.204, 1.205, 1.206, 1.207, 1.208, 1.209, 1.21,
1.211, 1.212, 1.213, 1.214, 1.215, 1.216, 1.217, 1.218, 1.219,
1.22, 1.221, 1.222, 1.223, 1.224, 1.225, 1.226, 1.227, 1.228,
1.229, 1.23, 1.231, 1.232, 1.233, 1.234, 1.235, 1.236, 1.237,
1.238, 1.239, 1.24, 1.241, 1.242, 1.243, 1.244, 1.245, 1.246,
1.247, 1.248, 1.249, 1.25, 1.251, 1.252, 1.253, 1.254, 1.255,
1.256, 1.257, 1.258, 1.259, 1.26, 1.261, 1.262, 1.263, 1.264,
1.265, 1.266, 1.267, 1.268, 1.269, 1.27, 1.271, 1.272, 1.273,
1.274, 1.275, 1.276, 1.277, 1.278, 1.279, 1.28, 1.281, 1.282,
1.283, 1.284, 1.285, 1.286, 1.287, 1.288, 1.289, 1.29, 1.291,
1.292, 1.293, 1.294, 1.295, 1.296, 1.297, 1.298, 1.299, 1.3, 1.301,
1.302, 1.303, 1.304, 1.305, 1.306, 1.307, 1.308, 1.309, 1.31,
1.311, 1.312, 1.313, 1.314, 1.315, 1.316, 1.317, .318, 1.319, 1.32,
1.321, 1.322, 1.323, 1.324, 1.325, 1.326, 1.327, 1.328, 1.329,
1.33, 1.331, 1.332, 1.333, 1.334, 1.335, 1.336, 1.337, 1.338,
1.339, 1.34, 1.341, 1.342, 1.343, 1.344, 1.345, 1.346, 1.347,
1.348, 1.349, 1.35, 1.351, 1.352, 1.353, 1.354, 1.355, 1.356,
1.357, 1.358, 1.359, 1.36, 1.361, 1.362, 1.363, 1.364, 1.365,
1.366, 1.367, 1.368, 1.369, 1.37, 1.371, 1.372, 1.373, 1.374,
1.375, 1.376, 1.377, 1.378, 1.379, 1.38, 1.381, 1.382, 1.383,
1.384, 1.385, 1.386, 1.387, 1.388, 1.389, 1.39, 1.391, 1.392,
1.393, 1.394, 1.395, 1.396, 1.397, 1.398, 1.399, and 1.4 degrees
Celsius. For example, according to certain preferred embodiments,
the lubricating fluid can have a refractive index of about 1.296
degrees Celsius.
[0076] The lubricating fluid can have a vapor pressure within a
range having a lower limit and/or an upper limit. The range can
include or exclude the lower limit and/or the upper limit. The
lower limit and/or upper limit can be selected from
2.times.10.sup.-9, 1.times.10.sup.-8, 1.times.10.sup.-7,
1.times.10.sup.-8, 1.times.10.sup.-5, 1.times.10.sup.-4,
1.times.10.sup.-3, 1.times.10.sup.-2, torr at 20 degrees Celsius.
For example, according to certain preferred embodiments, the
lubricating fluid can have a vapor pressure of from
2.times.10.sup.-9 to 1.0.times.10.sup.-4 torr at 20 degrees
Celsius.
[0077] The lubricating fluid can be applied by one selected from
the group consisting of spin-coating, soaking, dip-coating,
spray-coating, injecting, screen-printing, atomic layer deposition
and combinations thereof.
[0078] As described above, the nanostructured layer 14 can be
covalently or otherwise strongly bonded to the substrate 12. Such
bonds, especially, covalent bonds, are very strong and eliminate
cracks that can act to concentrate stresses. In particular, this is
a significant improvement over conventional adhesive bonding and
allows the flexibility to bond a nanostructured layer to a
compositionally different substrate without the use of an adhesive.
This is yet another manner in which the durability of the
nanostructured layer described herein is enhanced.
[0079] A method of forming an article 10 with a nanostructured
surface 14 is also described. As shown in FIGS. 2A-D, the method
can include providing a substrate 12 (FIG. 2A); depositing a film
28 on the substrate 12 (FIG. 2B); decomposing the film 28 to form a
decomposed film 26 (FIG. 2C); and etching the decomposed film 26 to
form the nanostructured layer 14 (FIG. 2D). The decomposed film 26
can be a spinodally decomposed film.
[0080] In the depositing step, the film 28 can be deposited on the
substrate 12 using an in-situ thin film deposition process selected
from the group that includes, but is not limited to, pulsed laser
ablation, chemical vapor deposition (CVD), metallorganic chemical
vapor deposition (MOCVD), sputtering and e-beam co-evaporation.
[0081] Alternately, the film 28 can be deposited on the substrate
12 using an ex-situ thin film deposition process selected from the
group that includes, but is not limited to chemical solution
processes, and deposition of a halogen compound for an ex situ film
process, followed by a heat treatment. The depositing step can
occur at a temperature between 15 and 800.degree. C.
[0082] In some exemplary methods, the decomposing step can be part
of the depositing step, i.e., the film 28 may be deposited in
decomposed state 26. For example, by depositing the film 28 at a
temperature sufficient to induce decomposition, e.g., spinodal
decomposition, during the depositing step. In other exemplary
methods, the decomposing step can be a separate step, such as a
heating step. The decomposing step can include heating the
deposited film 28 to a sufficient temperature for a sufficient time
to produce a nanoscale spinodal decomposition. As used herein,
"nanoscale spinodal decomposition" refers to spinodal decomposition
where the protrusive and recessive interpenetrating networks are of
dimensions that, upon differential etching, can result in the
nanostructured layers described herein.
[0083] Again, one embodiment relates to a method including applying
a glass film to a substrate; heating the glass film to a
temperature and for a duration sufficient to phase-separate the
glass; differentially etching the glass to create a porous
interpenetrating structure; modifying a surface chemistry of the
porous interpenetrating structure; and adding a lubricating fluid
to at least one pore of the porous interpenetrating structure. The
film can include one selected from the group consisting of sodium
borosilicate glass, a soda lime glass, and combinations
thereof.
[0084] The temperature to which the film is heated for a duration
sufficient to phase-separate the glass can be within a range having
a lower limit and/or an upper limit. The range can include or
exclude the lower limit and/or the upper limit. The lower limit
and/or upper limit can be selected from 400, 405, 410, 415, 420,
425, 430, 435, 440, 445, 450, 455, 460, 465, 470, 475, 480, 485,
490, 495, 500, 505, 510, 515, 520, 525, 530, 535, 540, 545, 550,
555, 560, 565, 570, 575, 580, 585, 590, 595, 600, 605, 610, 615,
620, 625, 630, 635, 640, 645, 650, 655, 660, 665, 670, 675, 680,
685, 690, 695, 700, 705, 710, 715, 720, 725, 730, 735, 740, 745,
750, 755, 760, 765, 770, 775, 780, 785, 790, 795, 800, 805, 810,
815, 820, 825, 830, 835, 840, 845, 850, 855, 860, 865, 870, 875,
880, 885, 890, 895, and 900 degrees Celsius. For example, according
to certain preferred embodiments, the temperature to which the
glass film is heated for a duration sufficient to phase-separate
the glass can be from 500 to 800 degrees Celsius.
[0085] The duration for which the film is heated that is sufficient
to phase-separate the glass can be within a range having a lower
limit and/or an upper limit. The range can include or exclude the
lower limit and/or the upper limit. The lower limit and/or upper
limit can be selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,
98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112, 113, 114, 115, 116, 117, 118, 119, and 120 seconds. For
example, according to certain preferred embodiments, the duration
for which the glass film is heated that is sufficient to
phase-separate the glass can be from 1 second to 60 seconds. The
duration for which the glass film is heated that is sufficient to
phase-separate the glass can be from 1 minute to 60 minutes.
[0086] The duration for which the film is heated that is sufficient
to phase-separate the glass can be within a range having a lower
limit and/or an upper limit. The range can include or exclude the
lower limit and/or the upper limit. The lower limit and/or upper
limit can be selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,
98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124,
125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,
138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150,
151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163,
164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176,
177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189,
190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202,
203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215,
216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228,
229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, and 240
hours. For example, according to certain preferred embodiments, the
duration for which the glass film is heated that is sufficient to
phase-separate the glass can be from 1 hour to 240 hours.
[0087] The duration for which the film is heated that is sufficient
to phase-separate the glass can be within a range having a lower
limit and/or an upper limit. The range can include or exclude the
lower limit and/or the upper limit. The lower limit and/or upper
limit can be selected from 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7,
1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1,
3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5,
4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9,
6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3,
7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7,
8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, and 10
days. For example, according to certain preferred embodiments, the
duration for which the glass film is heated that is sufficient to
phase-separate the glass can be from 1 second to 10 days.
[0088] The temperature can be about 700 degrees Celsius and the
duration can be within a range having a lower limit and/or an upper
limit. The range can include or exclude the lower limit and/or the
upper limit. The lower limit and/or upper limit can be selected
from 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2,
2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6,
3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5,
5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4,
6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8,
7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2,
9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4,
10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, 11.5,
11.6, 11.7, 11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6,
12.7, 12.8, 12.9, 13, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7,
13.8, 13.9, 14, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8,
14.9, and 15 minutes. For example, according to certain preferred
embodiments, the temperature can be about 700 degrees Celsius and
the duration can be from 1 to 10 minutes.
[0089] The temperature can be about 500 degrees Celsius and the
duration can be within a range having a lower limit and/or an upper
limit. The range can include or exclude the lower limit and/or the
upper limit. The lower limit and/or upper limit can be selected
from 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2,
2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6,
3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5,
5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4,
6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8,
7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2,
9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, and 10 days. For example,
according to certain preferred embodiments, the temperature can be
about 500 degrees Celsius and the duration can be from 3-5
days.
[0090] The decomposition step can be performed under a
non-oxidizing or inert atmosphere. Exemplary inert or non-oxidizing
atmospheres include Ar, H.sub.2, N.sub.2, and combinations thereof
(e.g., Ar & H.sub.2).
[0091] Exemplary decomposed films 26 include a contiguous,
protrusive phase and a contiguous, recessive phase that are
differentially etchable (i.e. have different etch rates), when
subjected to one or more etchants and have an interconnected
structure, such as a spinodal structure. The as-deposited film 28
may need to be heat treated in order to phase separate properly.
The decomposed film 26 can then be differentially etched to remove
most or all of the recessive phase (such as borate-rich phase in
the case of borosilicate glass), and to sharpen and thin the
protrusive phase to form the plurality of nanostructured features
16.
[0092] Although etching is generally described herein as being
solution based, etching can also be carried out by vapor etchants.
The remaining surface features 16 after etching are characterized
by general nanosize dimensions (width, length, and spacing) in a
range of about 4 nm to no more than 500 nm, preferably<200 nm,
such as in a range of about 50 nm to no more than about 100 nm.
[0093] Nanostructured feature 16 dimensions may vary as a function
of feature length if a wet etch process is used to form the
nanostructured features 16. In this case, the feature dimensions at
the air-layer interface 32 of the nanostructured layer 14 tends to
be smallest, with the feature size increasing monotonically towards
the layer-substrate interface 34, which is inherently exposed to
the etchant for a shorter period of time. An exemplary etchant is
hydrogen fluoride, such as a 0.05 to 1 mol-% aqueous hydrogen
fluoride solution or a 0.1 to 0.5 mol-% aqueous hydrogen fluoride
solution.
[0094] The dimensions of the nanostructured features 16 are
dependent on a number of factors, such as composition, heat
treating duration and temperature. The nanostructured feature 16
dimensions, including height of the features, are generally
determined by the etch rate and etch time selected. Compared to the
processing described in the Differential Etching References cited
herein, shorter heating and etch times are generally utilized to
form features having dimensions<200 nm.
[0095] Smaller feature sizes (<200 nm) make the nanostructured
layer 14 more optically transparent. The processing parameters are
heavily dependent on the specific phase separating material used.
For example, some glasses will phase separate and be spinodal from
the initial glass deposition (no additional heat treating
required). Other glasses require many days of specific heat
treating to form a phase separated spinodal structure. This
dependence on the processing parameters is applicable for other
parameters as well (e.g., etchant type, etchant concentration and
etch time). The degree of transparency can often be typically less
than optical quality, such as a Strehl ratio<0.5, due to the
imposed surface roughness (or porosity) of the features that make
the surface superhydrophobic.
[0096] The method can also include applying a continuous
hydrophobic coating 36 to a surface 38 of the plurality of spaced
apart nanostructured features 16. The continuous hydrophobic
coating 36 can be a self-assembled monolayer as described
above.
[0097] The etching step can be continued until a width, length and
height of each of the plurality of spaced apart nanostructured
features 16 ranges from 1 to 500 nm, or can be continued until the
nanostructured features 16 are any other size described herein.
[0098] The decomposed film 26 can include a first material and a
second material different from the first material. The first
material can be contiguous and the second material can be
contiguous, and the first and second materials can form an
interpenetrating structure. The first material and the second
material can have differential susceptibility to an etchant, e.g.,
0.5 molar HF. For example, the first material can be a protrusive
phase, i.e., less susceptible to the etchant, and the second
material can be a recessive phase, i.e., more susceptible to the
etchant.
[0099] The first and second materials can be independently selected
from the group consisting of glass, metal, ceramic, polymer, resin,
and combinations thereof. The first material can be a first glass
and the second material can be a second glass different from the
first glass.
[0100] In some exemplary methods, the recessive phase is completely
etched, while in others exemplary methods portions of the recessive
phase remain. Accordingly, the nanostructured layer 14 can include
an etching residue disposed on the contiguous, protrusive material,
where the etching residue is from a recessive contiguous material
that was interpenetrating with the protruding material in the
decomposed film 26.
[0101] Again, one embodiment relates to a method including applying
a glass film to a substrate; heating the glass film to a
temperature and for a duration sufficient to phase-separate the
glass; differentially etching the glass to create a porous
interpenetrating structure; modifying a surface chemistry of the
porous interpenetrating structure; and adding a lubricating fluid
to at least one pore of the porous interpenetrating structure. The
differential etching can be performed using an etchant comprising
one selected from hydrogen fluoride, ammonium fluoride, and
combinations thereof.
[0102] The porous interpenetrating structure can have a porosity
within a range having a lower limit and/or an upper limit. The
range can include or exclude the lower limit and/or the upper
limit. The lower limit and/or upper limit can be selected from 5,
6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,
58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74,
75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91,
92, 93, 94, and 95 volume percent. For example, according to
certain preferred embodiments, the porous interpenetrating
structure can have a porosity of from 10 to 90 volume percent.
[0103] The porous interpenetrating structure can include a
plurality of pores having an average pore diameter within a range
having a lower limit and/or an upper limit. The range can include
or exclude the lower limit and/or the upper limit. The lower limit
and/or upper limit can be selected from 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,
98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124,
125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137,
138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150,
151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163,
164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176,
177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189,
190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202,
203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215,
216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228,
229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241,
242, 243, 244, 245, 246, 247, 248, 249, and 250 nm. For example,
according to certain preferred embodiments, the porous
interpenetrating structure can include a plurality of pores having
an average pore diameter of from 10-200 nm.
[0104] The porous interpenetrating structure can include a
plurality of pores having an average depth within a range having a
lower limit and/or an upper limit. The range can include or exclude
the lower limit and/or the upper limit. The lower limit and/or
upper limit can be selected from 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65,
66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82,
83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99,
100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112,
113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125,
126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138,
139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151,
152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164,
165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177,
178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190,
191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203,
204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216,
217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229,
230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242,
243, 244, 245, 246, 247, 248, 249, and 250 nm. For example,
according to certain preferred embodiments, the porous
interpenetrating structure can include a plurality of pores having
an average depth of from 10-200 nm.
[0105] The pore diameter can indicate a separation between peaks
defining a perimeter of a pore. The porous interpenetrating
structure can include a continuous phase comprising the glass film
having pores randomly distributed throughout. The porous
interpenetrating structure can include a reticulated network
comprising glass film, having pores randomly distribute
throughout.
[0106] The method can include pinning an oil or perfluorinated
liquid 40 within nanopores 20 formed (or defined) by the plurality
of spaced apart nanostructured features 16. The pinning step can
include contacting an oil pinning solution with the nanopores 20 of
the nanostructured layer 14. The oil pinning solution can include
the oil 40, a surfactant, or both. Exemplary surfactants include
volatile alcohols, e.g., methanol, ethanol, etc.; acetone; volatile
linear and branched alkanes, alkenes and alkynes, e.g., hexane,
heptanes and octane; and combinations thereof. It should be noted
that the surfactant can be the hydrophobic agent that is applied to
the surface, i.e., a fluoropolymer.
[0107] The oil 40 being pinned should be miscible in the surfactant
and the surfactant should have a viscosity that is lower than that
of the oil. Because high viscosity fluids, such as some of the
relevant non-volatile oils, cannot penetrate into nanopores 20, a
critical feature of the surfactants is reduction of the effective
viscosity of the oil pinning solution to a range that can penetrate
the nanopores 20. Once the oil pinning solution penetrates the
nanopores 20, the surfactant can volatize leaving the oil 40 pined
within the nanopores 20.
[0108] In general, the ratio of oil-to-surfactant should be such
that the viscosity of the oil pinning solution is sufficiently low
to penetrate into the nanopores of the nanostructured layer 14. The
oil can be 0.01 to 100 wt-% of the oil pinning solution, 0.01 to 20
wt-% of the oil pinning solution, 0.05 to 10 wt-% of the oil
pinning solution or 0.1-5 wt-% of the oil pinning solution. Where
the surfactant is present, the surfactant can be 99.99 to 80 wt-%
of the oil pinning solution, or 99.95 to 90 wt-% of the oil pinning
solution, or 99.99 to 95 wt-% of the oil pinning solution.
Additional features of the exemplary materials with oil 40 pinned
in the nanopores 20 of nanostructured layer 14 are provided in U.S.
application Ser. No. 12/901,072, "Superoleophilic Particles and
Coatings and Methods of Making the Same," filed Oct. 8, 2010, the
entirety of which is incorporated herein by reference.
[0109] The present invention can be used to make a variety of
articles. For example, articles can include cover plates for
optical systems, windows, labware and optical detectors.
[0110] One embodiment relates to an article including a substrate;
a glass film disposed on the substrate, and a lubricating fluid
disposed within the plurality of pores. The glass film can have an
interpenetrating structure, including a plurality of pores. The
interpenetrating structure can include at least one surface having
a modified surface chemistry that corresponds with at least one
property of the lubricating fluid. The at least one property of the
lubricating fluid can be a degree of hydrophobicity, a degree of
oleophobicity, a degree of lipophobicity, and combinations thereof.
According to various embodiments, the article can be optically
transparent. For purposes of the present invention, the sliding
angle is the angle at which a droplet, having a predefined weight,
begins to slide across a surface that is inclined by the sliding
angle. The predefined weight can be within a range having a lower
limit and/or an upper limit. The range can include or exclude the
lower limit and/or the upper limit. The lower limit and/or upper
limit can be selected from 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1,
5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500,
600, 700, 800, 900, and 1000 grams. For example, according to
certain preferred embodiments, the predefined weight can be greater
than or equal to 0.001 grams.
[0111] The article can exhibit a sliding angle within a range
having a lower limit and/or an upper limit. The range can include
or exclude the lower limit and/or the upper limit. The lower limit
and/or upper limit can be selected from 0.1, 0.2, 0.3, 0.4, 0.5,
0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9,
2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3,
3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7,
4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1,
6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5,
7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9,
9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, and 10 degrees with
respect to a 20 .mu.L drop of a liquid. For example, according to
certain preferred embodiments, the article can exhibit a sliding
angle of from 0.1 to 4.5 degrees with respect to a 20 .mu.L drop of
a liquid. The liquid can be selected from water, a hydrocarbon, and
combinations thereof. The hydrocarbon can be hexane, octane,
ethylene glycol, and combinations thereof.
[0112] The article can exhibit a contact angle hysteresis within a
range having a lower limit and/or an upper limit. The range can
include or exclude the lower limit and/or the upper limit. The
lower limit and/or upper limit can be selected from 0.1, 0.2, 0.3,
0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7,
1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1,
3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5,
4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9,
6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3,
7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7,
8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, and 10
with respect to a 20 .mu.L drop of a liquid. For example, according
to certain preferred embodiments, the article can exhibit a contact
angle hysteresis of from 0.4 to 4 with respect to a 20 .mu.L drop
of a liquid.
[0113] The contact angle hysteresis can be defined as a droplet
advancing angle minus a receding angle. Referring to FIG. 7 a
schematic illustration of a method for testing the contact angle
hysteresis of a drop of liquid 701 on a substrate 702 is shown. The
substrate can be tilted by an angle .THETA. and an advancing angle
.THETA..sub.a and a receding angle .THETA..sub.r can be
measured.
[0114] The article can have a transmittance within a range having a
lower limit and/or an upper limit. The range can include or exclude
the lower limit and/or the upper limit. The lower limit and/or
upper limit can be selected from 40, 41, 42, 43, 44, 45, 46, 47,
48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64,
65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98,
99, and 100%. For example, according to certain preferred
embodiments, the article can have a transmittance greater than 60%
with respect to light having a wavelength. The wavelength can be
within a range having a lower limit and/or an upper limit. The
range can include or exclude the lower limit and/or the upper
limit. The lower limit and/or upper limit can be selected from 150,
175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475,
500, 525, 550, 575, 600, 625, 650, 675, 700, 725, 750, 775, 800,
825, 850, 875, 900, 925, 950, 975, and 1000, 1500, 200, 2500, 3000,
3500, 4000 nm. For example, according to certain preferred
embodiments, the wavelength can be greater than 200 nm. More
specifically, the article can have a transmittance greater than 60%
with respect to light having a wavelength of greater than 200
nm.
EXAMPLES
Example 1
[0115] A sodium borosilicate material was sputtered onto a glass
substrate in Ar--H.sub.2 or Ar--O.sub.2 or Ar. The composition of
the sodium borosilicate material was 65.9 wt-% SiO.sub.2, 26.3 wt-%
B.sub.2O.sub.3, and 7.8 wt-% Na.sub.2O. The sputtering conditions
were as follows:
[0116] Base Pressure (Background pressure of the
system).about.1-3.times.10.sup.-7 Torr.
[0117] Sputter Pressure=5.times.10.sup.-3 Torr
[0118] Sputter Temperature (Substrate Temperature)=Room temperature
(.about.25.degree. C.)
[0119] Sputter Power=100 Watt
[0120] Sputter Gas=Ar
[0121] The sodium borosilicate-glasscomposite was heat treated for
5 minutes at a temperature of .about.700.degree. C. in order to
spinodally decompose the sodium borosilicate layer. The surface was
then etched for 1 minute using 0.5 mol-% hydrogen fluoride. The
resulting material was optically clear and had a layer thickness of
approximately 300 nm, feature sizes of .about.75 nm, and good
superhydrophobicity (contact angle>170 degrees). The surface
showed antireflective behavior.
Examples 2-6
[0122] A sodium borosilicate material was sputtered onto a glass
substrate in Ar--H.sub.2 or Ar--O.sub.2 or Ar. Processing details
as follows:
Fabrication of Nanostructured Silica Films:
[0123] Radio-frequency magnetron sputtering was used to deposit
thin film glass coatings (thickness=0.5 .mu.m-1 .mu.m) onto fused
silica substrates at room temperature using a two inch diameter
target that is made from a borosilicate glass composition
comprising 66 mole % SiO.sub.2, 26 mole % B.sub.2O.sub.3, and 8
mole % Na.sub.2O. This composition ensures metastable phase
separation after post-deposition thermal processing. Typical
sputtering conditions consisted of a gas mixture of argon and
oxygen (oxygen/argon=1/3) at a total pressure in the range of 3-5
mTorr. Before the growth, glass substrates were ultrasonically
cleaned with isopropanol for 15 min. Following deposition, the
coated fused silica samples were heat treated in air at 700 degrees
Celsius for 5-15 min. in order to produce adequate spinodal
decomposition. A heating rate of 5 degrees Celsius/min is employed
and samples were furnace cooled to room temperature. A phase
separated spinodal structure is not, by itself, sufficient to
create the required structure. Therefore, the surface coating is
differentially etched with a 1:5 dilute mixture of 10:1 buffered
oxide etchant (i.e., a mixture of ammonium fluoride and
hydrofluoric acid) and deionized water. The etchant creates a
nanoscale branched network by eradicating all the sodium borate
phase, leaving the silica-rich phase protruding from the surface.
The final thickness of the film's etched-out portion is adjusted
through a combination of deposition time and variable etch
parameters. To create a superhydrophobic surface, the etched
surface is treated by immersing the samples in a mixture of hexane
and 0.5 vol. % 1H,1H,2H,2H-perfluorooctyltrichlorosilane (Gelest,
Inc., 95%) for 30 min., followed by annealing in air in an oven at
115 degrees Celsius for 15 min.
Water Droplet Contact Angle Measurements:
[0124] Static, advancing and receding contact angle measurements
were performed using an Attension Theta model T301 optical
tensiometer (Biolin Scientific, Finland). Static contact angles
were determined by taking the average of at least ten 6 .mu.l
liquid droplets dispensed at different positions on the film.
Sliding angles were established by using an automated tilting stage
at a rate of 1 degree per second.
Lubrication of the Nanotextured Surface:
[0125] The lubricating fluid, perfluorinated polyether (PFPE) oil,
was applied to the porous nanostructure surface by using spin
coating technique at a spin rate of 1000 rpm for 30 seconds. With
matching surface chemistry paired with porous microstructure, the
lubricating fluid wicks into the pores by capillary forces, locking
the fluid into the structure. Here the mechanically robust nature
of the reticulated silica scaffold coupled with interconnected
nanopore network creates a robust and optically clear omniphobic
state with highly effective repellency toward a variety of
liquids.
Example 2
[0126] The purpose of this example is to compare the contact angle
hysteresis of glass films prepared with and without a lubricating
fluid, specifically a perfluoropolyether oil, incorporated into the
film's nanostructured features for a variety of liquids, each
having a different surface tension. A first nanostructured silica
film was fabricated as described above without lubrication of the
nanostructured surface. A second nanostructured silica film was
fabricated as described above with lubrication of the
nanostructured surface. The liquids tested included Hexane, Octane,
Ethylene Glycol, and water.
[0127] FIG. 8 is a chart plotting contact angle hysteresis
measurements against liquid surface tension for films prepared
according to Example 2, tested with a variety of fluids each having
a different surface tension. The data illustrated in FIG. 8 is also
summarized in Table 1.
TABLE-US-00001 TABLE 1 Surface Tension of Hysteresis Liquid with
PFPE Hysteresis without Liquid (mN/m) oil (degrees) PFPE oil
(degrees) Hexane 18.43 1.12 90 Octane 21.62 1.31 90 Ethylene glycol
48.4 3.93 90 Water 72.8 0.43 13.89
[0128] As shown from the data, with a trapped lubricant, the
nanostructured matrix enabled significantly decreased contact angle
hysteresis.
Example 3
[0129] The purpose of this example is to compare the sliding angle
of glass films prepared with and without a lubricating fluid,
specifically a perfluoropolyether oil, incorporated into the film's
nanostructured features for a variety of liquids, each having a
different surface tension. The liquids tested included Hexane,
Octane, Ethylene Glycol, and water.
[0130] A first nanostructured silica film was fabricated as
described above without lubrication of the nanostructured surface.
A second nanostructured silica film was fabricated as described
above with lubrication of the nanostructured surface.
[0131] Sliding angles were measured by using an automated tilting
stage at a rate of 1 degree per second. The sliding angle is
determined by recording pictures of the liquid droplets, via an
integrated camera at a rate of 4 frames per second, during tilting
of the stage. The value of the critical angle is assigned when the
first sliding action of the liquid droplet is observed.
[0132] FIG. 9 is a chart plotting sliding angle against liquid
surface tension for films prepared according to Example 3, tested
with a variety of fluids each having a different surface tension.
The data is also summarized in Table 2.
TABLE-US-00002 TABLE 2 Sliding Angle with Sliding Angle with
Surface Tension surface modifier surface modifier and (mN/m) (SAM)
(degrees) PFPE oil (degrees) Hexane 18.43 90 -- Octane 21.62 90 2.7
Ethylene 48.4 90 4.42 glycol Water 72.8 8 0.5
[0133] The data shows the sliding angle performance of the two
nanostructured film coated quartz samples. The processing details
of the films have been described in the above examples. One sample
is infused with oil and the other one is not. The sample denoted as
"with surface modifier" is in the superhydrophobic state and has
only fluorinated surface chemistry. The other one denoted as "with
surface modifier and PFPE oil" has both underlying fluorinated
chemistry and also coated (or infused) with oil. The sample with
lubricating oil trapped in its structure shows significantly lower
sliding angles, and hence super-repellency for a wide variety of
liquids having very different surface tensions (see videos 11 for
water, 12 for ethylene glycohol, and 14 for octane). Video
presented in 13 compares the sliding behavior of water droplets on
a smooth glass slide to the one coated with a nanostructured film.
Both samples are lubricated with PFPE oil (FOMBLIN.TM. 16/6 oil,
available from Solvay Plastics). The video clearly shows that the
nanostructured surface enables enhanced mobility and continuous
sliding of the water droplet without any pinning, while a
smooth-untextured-surface shows significant pinning of the droplet
to substrate surface.
Example 4
[0134] The purpose of this example is to compare the sliding
behavior of various liquids across a nanostructured silica film
that was fabricated as described above with lubrication of the
nanostructured surface. The lubricating fluid was a
perfluoropolyether oil (P=3.times.10.sup.-5 Torr@20 degrees
Celsius). The liquids tested included octane, polyethylene glycol,
and water. A drop of each liquid was placed on the glass film,
which was held at an inclination angle of 5 degrees. Videos of each
drop sliding across the surface of the glass film were recorded.
FIGS. 10a-e show frames of a video of a drop of polyethylene glycol
sliding across the surface of the glass film. FIGS. 11a-e show
frames of a video of a drop of octane sliding across the surface of
the glass film. FIGS. 12a-e show frames of a video of a drop of
water sliding across the surface of the glass film. The frames are
taken at approximately every two seconds.
Example 5
[0135] The purpose of this example is to compare the sliding rate
of water across glass films prepared with and without a lubricating
fluid, specifically a perfluoropolyether oil, incorporated into the
film's nanostructured features. A first nanostructured silica film
was fabricated as described above without lubrication of the
nanostructured surface. A second nanostructured silica film was
fabricated as described above with lubrication of the
nanostructured surface.
[0136] FIGS. 13a-e show frames of a video of a side-by-side
comparison of a first drop of water sliding across the surface the
first glass film (left) without lubrication of the nanostructured
surface and a second drop of water sliding across the surface of
the second glass film (right) with lubrication of the
nanostructured surface. A drop of each liquid was placed on the
glass film, which was held at an inclination angle of 5 degrees.
The frames are taken at approximately every two seconds.
Example 6
[0137] The purpose of this example is to compare the transmittance
of light at various wavelengths through glass films prepared with
and without a lubricating fluid, specifically a perfluoropolyether
oil, incorporated into the film's nanostructured features. It was
discovered that the transparency is not compromised when a
perfluoropolyether oil is pinned within the nanostructured
features. The perfluoropolyether oil had a index of refraction of
n20/D 1.299). A first nanostructured silica film was fabricated as
described above without lubrication of the nanostructured surface.
A second nanostructured silica film was fabricated as described
above with lubrication of the nanostructured surface. A third
sample of plain, uncoated fused silica was tested.
[0138] FIG. 14 is a chart plotting transmittance of the three films
against wavelength. FIG. 14 compares UV-Vis transmission spectra of
the two nanostructured films, one with and the other without
lubricant modification, to the plain untreated reference quartz
sample. Whether it is lubricated state or not, the coated quartz
sample enables higher transmittance that the uncoated counterpart
because the effective index of refraction is significantly reduced
(Note: we could not determine how much due to the complicated
nature of the film microstructure) by the fact that the coating is
not dense and has a porous submicron structure, and consequently
acts as a broadband antireflective coating. On the other hand, the
measurements also showed a substantial decrease in transmittance at
shorter wavelengths for the film without oil modification due to
increased scattering by surface features (.ltoreq.100 nm),
signifying UV-blocking functionality. Infusion of a lower index of
refraction lubricant [refractive index lower than quartz
(approximately n=1.47) and higher than air n=1] to the structure
fills in the pores and hence reduces the Rayleigh scattering effect
thereby increasing the transmittance at lower wavelengths (i.e.,
<400 nm).
[0139] Although the present invention has been described in
considerable detail with reference to certain preferred versions
thereof, other versions are possible. Therefore, the spirit and
scope of the appended claims should not be limited to the
description of the preferred versions contained herein.
[0140] The reader's attention is directed to all papers and
documents which are filed concurrently with this specification and
which are open to public inspection with this specification, and
the contents of all such papers and documents are incorporated
herein by reference.
[0141] All the features disclosed in this specification (including
any accompanying claims, abstract, and drawings) may be replaced by
alternative features serving the same, equivalent or similar
purpose, unless expressly stated otherwise. Thus, unless expressly
stated otherwise, each feature disclosed is one example only of a
generic series of equivalent or similar features.
[0142] Any element in a claim that does not explicitly state "means
for" performing a specified function, or "step for" performing a
specific function, is not to be interpreted as a "means" or "step"
clause as specified in 35 U.S.C .sctn.112, sixth paragraph. In
particular, the use of "step of" in the claims herein is not
intended to invoke the provisions of 35 U.S.C .sctn.112, sixth
paragraph.
* * * * *