U.S. patent application number 14/579464 was filed with the patent office on 2015-04-16 for surface properties of polymeric materials with nanoscale functional coating.
The applicant listed for this patent is Yaw Samuel Obeng, Edward Maxwell Yokley. Invention is credited to Yaw Samuel Obeng, Edward Maxwell Yokley.
Application Number | 20150103504 14/579464 |
Document ID | / |
Family ID | 50627989 |
Filed Date | 2015-04-16 |
United States Patent
Application |
20150103504 |
Kind Code |
A1 |
Yokley; Edward Maxwell ; et
al. |
April 16, 2015 |
SURFACE PROPERTIES OF POLYMERIC MATERIALS WITH NANOSCALE FUNCTIONAL
COATING
Abstract
An electronic device comprising a substrate having a
component-side surface and a moisture protection film covering the
component-side surface. The moisture protection film includes a
first water layer bonded to component-side surface that is an
activated surface, wherein the activated surface has a lower water
contact angle than the substrate surface before the surface
activation. The film includes a first graphed layer of a
plasma-reacted first set of precursor molecules graphed to the
first water layer, wherein the first water layer forms a first
bonding link between the substrate surface and the reacted first
set precursor molecules. The film includes a second water layer
bonded to the first graphed layer. The film includes a second
graphed layer of a plasma-reacted second set of precursor molecules
graphed to the second water layer, wherein the second water layer
forms a second bonding link between the second water layer and the
reacted second set of precursor molecules.
Inventors: |
Yokley; Edward Maxwell;
(Anderson, SC) ; Obeng; Yaw Samuel; (Frederick,
MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yokley; Edward Maxwell
Obeng; Yaw Samuel |
Anderson
Frederick |
SC
MD |
US
US |
|
|
Family ID: |
50627989 |
Appl. No.: |
14/579464 |
Filed: |
December 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13665314 |
Oct 31, 2012 |
8962097 |
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14579464 |
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12206013 |
Sep 8, 2008 |
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13665314 |
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60970582 |
Sep 7, 2007 |
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Current U.S.
Class: |
361/760 |
Current CPC
Class: |
H05K 1/185 20130101;
H05K 3/284 20130101; H05K 2201/0104 20130101; H05K 2201/0195
20130101; B29C 59/14 20130101; B05D 3/144 20130101; H05K 2203/095
20130101; C03C 23/006 20130101; B05D 1/62 20130101; C03C 2218/31
20130101; B05D 3/142 20130101; H05K 2201/09872 20130101 |
Class at
Publication: |
361/760 |
International
Class: |
H05K 1/18 20060101
H05K001/18 |
Claims
1. A electronic device, comprising: a substrate having a
component-side surface; and a moisture protection film covering the
component-side surface, the moisture protection film including: a
first water layer bonded to component-side surface that is an
activated surface, wherein the activated surface has a lower water
contact angle than the substrate surface before the surface
activation; a first graphed layer of a plasma-reacted first set of
precursor molecules graphed to the first water layer, wherein the
first water layer forms a first bonding link between the substrate
surface and the reacted first set precursor molecules; a second
water layer bonded to the first graphed layer; and a second graphed
layer of a plasma-reacted second set of precursor molecules graphed
to the second water layer, wherein the second water layer forms a
second bonding link between the second water layer and the reacted
second set of precursor molecules.
2. The device of claim 1, wherein: the component-side surface was
exposed a first plasma treatment having plasma reactants in a
plasma chamber to form the activated substrate surface; the first
water layer was formed after removing the plasma reactants from the
plasma chamber and then introducing water vapor into the plasma
chamber to form the first water layer bonded to the activated
surface; and then the plasma-reacted first set of precursor
molecules was formed in a second plasma treatment that includes
introducing the precursor molecules of the first set into the
plasma chamber at a plasma chamber pressure that is in a range from
100 mTorr to 500 mTorr.
3. The device of claim 2, wherein the precursor molecules of the
first set include olefinic hydrocarbon of 4-15 carbon atoms.
4. The device of claim 2, wherein the olefinic precursor molecules
includes paracyclophanes.
5. The device of claim 2, wherein the olefinic precursor molecules
includes parylene.
6. The device of claim 2, wherein the precursor molecules of the
first set include tetraethyloxyorthosilane.
7. The device of claim 2, wherein: the second water layer was
formed after removing the precursor molecules of the first set from
the plasma chamber and then introducing water vapor into the plasma
chamber to form the second water layer bonded to the the
plasma-reacted first set of precursor molecules; and then the
plasma-reacted second set of precursor molecules was formed in a
third plasma treatment that includes introducing the precursor
molecules of the second set into the plasma chamber at a plasma
chamber pressure that is in a range from 100 mTorr to 500
mTorr.
8. The device of claim 7, wherein the precursor molecules of the
first set include olefinic hydrocarbon of 4-15 carbon atoms.
9. The device of claim 7, wherein the olefinic precursor molecules
includes paracyclophanes.
10. The device of claim 7, wherein the olefinic precursor molecules
includes parylene.
11. The device of claim 7, wherein the precursor molecules of the
first set include tetraethyloxyorthosilane.
12. The device of claim 1, wherein the component-side surface
includes a borosilicate glass surface.
13. The device of claim 1, wherein the component-side surface
includes a surface of a thermal vapor coating of parylene.
14. The device of claim 1, wherein the component-side surface
includes a surface of electrically conductive polymer.
15. The device of claim 1, wherein the first graphed layer of the
plasma-reacted first set of precursor molecules is a parylene layer
and the second graphed layer of the plasma-reacted second set of
precursor molecules is a parylene layer.
16. The device of claim 1, wherein the first graphed layer of the
plasma-reacted first set of precursor molecules is a silicon oxide
layer and the second graphed layer of the plasma-reacted second set
of precursor molecules is a silicon oxide layer.
17. The device of claim 1, wherein the first graphed layer of the
plasma-reacted first set of precursor molecules is a silicon oxide
layer and the second graphed layer of the plasma-reacted second set
of precursor molecules is a parylene layer.
18. The device of claim 1, wherein the first graphed layer of the
plasma-reacted first set of precursor molecules is a parylene layer
and the second graphed layer of the plasma-reacted second set of
precursor molecules is a silicon oxide layer.
19. The device of claim 1, wherein the moisture protection film
covering the component-side surface is a conformal coating.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation application of U.S. application Ser.
No. 13/665,314 filed on Oct. 31, 2012, which in turn is a
continuation in part application of U.S. application Ser. No.
12/206,013 filed on Sep. 8, 2008, entitled Surface Properties of
Polymeric Materials with Nanoscale Functional Coating to Yokley and
Obeng, which in turn claims the benefit of U.S. Provisional
Application Ser. No. 60/970,582 filed on Sep. 7, 2007, entitled,
Improving Surface Properties of Polymeric Materials by the Creation
of Nanoscale Functional Coatings, to Yokley and Obeng, and also
claims the benefit of U.S. Provisional Application Ser. No.
61/564,415 filed on Nov. 29, 2011 entitled, Surface Properties of
Polymeric Materials with Conformal Dry Nanoscale Functional
Coatings to Yokley and Obeng, all being incorporated herein by
reference.
TECHNICAL FIELD
[0002] This application is directed, in general, to a process for
depositing films, the films formed by the process and, more
specifically, to a process for forming conformal surface film
coatings for protecting electronic and other devices.
BACKGROUND
[0003] There is a growing requirement for conformal barrier
coatings or films having high adhesion for corrosion protection,
water proofing, surface decoration, for medical device passivation,
circuit board moisture protection, consumer electronic devices and
a wide variety of industrial, consumer devices and similar objects.
There is a need to better engineer the air-substrate interface of
such films for specific applications. For example, it is often
desirable for films to modify the substrate surface without
altering the bulk properties of the substrate. It is sometimes
desirable to engineer films to have the potential to enhance the
structural and functional performance of fabricated polymeric
devices. Enhancement of the surface can occur with designed
organic, inorganic or hybrid polymeric coatings. However, many
existing films suffer from poor adhesive bonding to the underlying
surface, since the device materials construction are inherently
non-reactive to reduce the incidence of reactions with the
surrounding tissues.
SUMMARY
[0004] One embodiment of the disclosure provides an electronic
device. The device comprises a substrate having a component-side
surface. The device comprises a moisture protection film covering
the component-side surface. The moisture protection film includes a
first water layer bonded to component-side surface that is an
activated surface, wherein the activated surface has a lower water
contact angle than the substrate surface before the surface
activation. The film includes a first graphed layer of a
plasma-reacted first set of precursor molecules graphed to the
first water layer, wherein the first water layer forms a first
bonding link between the substrate surface and the reacted first
set precursor molecules. The film includes a second water layer
bonded to the first graphed layer. The film includes a second
graphed layer of a plasma-reacted second set of precursor molecules
graphed to the second water layer, wherein the second water layer
forms a second bonding link between the second water layer and the
reacted second set of precursor molecules.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:
[0006] FIG. 1 shows a flow diagram showing steps in an example
process of the present invention;
[0007] FIG. 2 shows a cross-sectional view of an example film
formed on a substrate is accordance with a process of the
disclosure such as any of the embodiment discussed in the context
of FIG. 1;
[0008] FIG. 3 shows a simulated time-of-flight secondary ion mass
spectrometry (TOF-SIMS) trace of an example film formed on a
substrate is accordance with a process of the disclosure such as an
embodiment (e.g., a one-pass embodiment) of the film deposition
process presented in FIG. 1;
[0009] FIG. 4 shows an optical interferometry of an example masked
step edge plasma-assisted silicon oxide (SiOx) deposited film on a
glass substrate, produced in an example embodiment of the process
flow in FIG. 1, where tetraethoxysilane (TEOS) was used as the
precursor in the step following the exposure of the cleaned and
activated surface to water vapor;
[0010] FIG. 5 presents a summary of example air flow rate
deviations measured after an example autoclave cycling tests such
as described in Example 2 of the application; and
[0011] FIG. 6 presents an example optical interferometry image of
an example 60 nm styrene film edge on a de-masked glass sample
substrate in accordance to with a process of the disclosure such as
an embodiment of the process presented in FIG. 1.
DETAILED DESCRIPTION
[0012] As part of the present disclosure, it was discovered that
forming a water layer after a plasma cleaning and activating step
enhances the formation of films, such as conformal films for the
purpose of providing a moisture and environmental barrier to
protect electronic or other devices. This discovery was made by
accident when, between a first plasma treatment to atomically clean
and activate a substrate's surface, and a second plasma treatment
to expose the activated surface to pre-cursors molecules, the
activated surface was inadvertently exposed to air having a high
moisture content.
[0013] For the purposes of the present disclosure, the term
atomically cleaned and activated, or, plasma cleaned and activated,
refers to the treatment of a substrate surface with low molecular
weight molecules or atoms (e.g., Helium, Argon, Nitrogen, Neon,
Silane, Hydrogen and Oxygen) in the presence of a radiofrequency
plasma, to clean the substrate's surface by making the surface free
of contaminants such as organic contaminants and water. Such a
plasma treatment, referred to a first plasma treatment herein, also
actives the substrate's surface by breaking up covalent and/or
other chemical bonds of the substrate molecules at the surface,
thereby making the substrate surface easier to react with plasma
treated pre-cursors molecule.
[0014] It is counter-intuitive to think that it would be beneficial
to first expose such a cleaned and activated surface to water vapor
before exposing the surface to plasma treated pre-cursors
molecules. It is counter-intuitive because one of the goals of such
a plasma treatment is to remove contaminates from a surface, which
typically includes removing water from the surface. While not
limiting the scope of the invention by theoretical considerations,
it is thought that exposure of the cleaned and activated substrate
surface to water vapor results in the adsorption or chemisorption
of a water layer, e.g., one or more monolayers of water, onto the
surface. It is thought that a water layer at the interface between
the substrate and grafted layered of various plasma treated
pre-cursors molecules promotes the formation of strong bonds
between the grafted material and the substrate. A quantitative
indicator of the presences of such an activated surface is that the
surfaces has a lower water contact angle (e.g., at least about 10
percent and in some cases at least about 20 percent lower) than the
substrate surface before the surface activation.
[0015] The term water layer as used herein refers to one or more
self-assembled monolayers of water molecules. For instance, the
water layer can range from a monolayer (e.g., a thickness of about
0.3 nanometers) to several monolayers (e.g., a thickness of about 2
nanometers). One skilled in the art would appreciate how the extent
of adsorption and thickness of the resultant water layer would be
controlled by the thermodynamic conditions present in the plasma
chamber containing the substrate and water vapor.
[0016] FIG. 1 shows a flow diagram showing selected steps in an
example film deposition process 100 of the disclosure. FIG. 2 shows
a cross-sectional view of an example device 200 (e.g., a circuit
board) have film 202 formed on a substrate 205, in accordance with
a process of the disclosure such as any of the embodiment discussed
in the context of FIG. 1.
[0017] With continuing reference to FIGS. 1 and 2 throughout, the
example process 100 comprises a first step 110 of exposing a
surface 210 of a substrate 205 to a first plasma treatment having
plasma reactants in a plasma chamber 215 to form an activated
substrate surface 210. For instance, in any of the embodiments of
the process 100, the substrate 205 can be a circuit board and the
surface 210 is a component-side surface of the circuit board. In
some embodiments the film layer 202 can be a conformal coating
designed to protect an electronic device, such as a circuit board,
from moisture under autoclave sterilization conditions.
[0018] As discussed above, step 110 can serve to atomically clean
and activate the substrate's surface 210. The process 100 also
comprises a step 120 of introducing water vapor into the plasma
chamber to form a water layer 220 on the activated surface 210. The
process 100 also comprises a step 130 of introducing pre-cursors
molecules into the plasma chamber 215 in the presence of a second
plasma treatment to graft a layer 225 of reacted pre-cursor
molecules on the water layer 220.
[0019] In some embodiments of the process 100, the first plasma
reactants in step 110 are formed from one or more of Helium, Argon,
Nitrogen, Neon, Silane, Hydrogen and Oxygen. In some cases
reactants are in the presence of the first plasma treatment that
includes: a radiofrequency power in the range of about 30 to 500
Watts, a temperature in range of about 0.degree. C. to about
100.degree. C. for a time period in a range of about 0.5 to 10
minutes. In some such embodiments, the first plasma reactants are
formed from Argon at pressures between about 50 and 500 mTorr in
the presence of the first plasma treatment that includes a
radiofrequency power in the range of about 50 to 200 Watts, a
temperature in range of about 0.degree. C. to about 100.degree. C.
for a time period in a range of about 0.5 to about 10 minutes.
[0020] In some embodiments of the process 100, following exposure
to water vapor as humid air (in step 120), in step 130, the
substrate surface 210 having the water layer 220 thereon is exposed
a flux of plasma-cracked, reactive organic or ceramic precursor
intermediates. Illustratively, such intermediates can be formed
from monomers introduced into a modified plasma environment, under
conditions that preserve the integrity of the reactive intermediate
species formed. Specifically, the plasma generation conditions
should not result in the total fragmentation or decomposition of
the precursor molecules, nor should the intermediates have very
short residence time in the reactor. Also, the intermediates should
be able to adsorb and react on the water layer on the cleaned and
activated substrate surface 210.
[0021] In some embodiments the water layer 220 formed in step 120,
is desirably not greater in thickness 230 than about 2 nanometers.
When the water layer thickness 230 is greater than 2 nanometers,
the outermost water molecules of the layer 220 are not tenaciously
bound, either chemically or physically, to the substrate surface
210. These outermost water molecules can desorb and react with the
incoming precursor species in step 130 to form new species which
may be undesirable or not beneficial to the film deposition process
100. Furthermore, the desorbed excess water molecules can adsorb on
the plasma chamber walls 240, and later on leach off of the wall
240 to thereby contaminate and impede the film deposition process
100. Experiments performed as part of the present disclosure,
suggest a water layer thickness 230 of 0.1 to 2 nanometers produces
a balanced situation where the benefits of the water layer 220 are
realized while avoiding the undesirable effects of excess
water.
[0022] While not limiting the scope of the invention by theoretical
considerations, it is thought that, in some cases, under the
reduced pressure of the process conditions used in step 130, all or
some of the adsorbed water layer 220 can be lost through
desorption. During step 130, it is also thought that water
molecules of the layer 220 can deprotonate to afford reactive
oxygen-radical rich surfaces with chemically unsatisfied dangling
bonds exposed to the flux of cracked monomer intermediates. The
reactive surface is thought to rapidly react with the reactive
species in the process chamber 215 to form strong chemical bonds
(e.g., covalent bonds), which result in the grafted layer 225 being
bonded to the substrate surface 210.
[0023] In some cases, the deposited film 202 having the grafted
layer 225 of reacted pre-cursor molecules, after step 130, retains
at least part of the water layer 220 in-between the surface 210 of
the substrate 205 and the grafted layer 225. For example, in some
cases, the retained water layer 220 has a thickness 230 in a range
from about 0.1 to 2 nanometers. For example, in some cases, the
retained water layer has a thickness 230 in a range from about 0.3
to 1.8 nanometers (e.g., a stack of about 1 to 6 self-assembled
monolayers of water). In such embodiments, it is thought that the
molecules of the water layer 220 form a bonding link between the
grafted layer 225 of reacted pre-cursor molecules and the substrate
surface 210.
[0024] In some embodiments of the process 100, organic (e.g.,
simple olefins to fluoro-olefins) or pre-ceramic monomers
pre-cursor molecules are applied in step 130 to form graphed layers
225 having a thickness 235 in a range of about 50 to 500
nanometers. In some embodiments the grafted layer 130 (and in some
cases retained water layer 220) provide complete coverage,
conformal to an irregular substrate surface 210 and are tightly
bounded with high durability.
[0025] In some embodiments of the process 100, the precursor
molecules in step 130 include hexafluoropropylene and Argon at
pressures between about 100 and 500 mTorr and the second plasma
treatment includes: a radiofrequency power in the range of about 50
to 250 Watts, a temperature in range of about 10.degree. C. to
about 80.degree. C. for a time period in a range of about 15 to
about 60 minutes.
[0026] As further illustrated in FIG. 2, the process 100 can
further include a step 140 of evacuating the plasma chamber 215 of
the first plasma reactants (e.g., in step 110) after forming the
activated substrate surface 210 and before introducing the water
vapor into the plasma chamber 215 (e.g., in step 120). For
instance, some embodiments of step 140 evacuating the plasma
chamber 215 includes reducing the atmospheric pressure in the
chamber 215 to less than about 100 Torr for at least about 5
minutes. Step 140 can advantageously mitigate the formation of
undesirable or not beneficial species from the reaction between the
water vapor introduced in step 120 and plasma reactants formed in
the chamber 215 in step 110.
[0027] In some embodiments of the process 100, it is desirable to
introduce the water vapor into the chamber 215 in step 120 to form
the water layer 220. For instance, in some cases, the water vapor
is in the chamber 215 when the second plasma treatment (e.g., step
130) is commenced. That is, as part of step 120 the water vapor is
introduced into the plasma chamber to expose the activated surface
to the water vapor before introducing the pre-cursors molecules
into the plasma chamber 215 (e.g., step 130). It is also desirable
to introduce the water vapor for a sufficient period to form the
desired thickness 230 of water layer 220 but as discussed above,
not to form an overly thick layer 220. For instance, in some cases,
the water vapor is in the chamber 215 for at least about 5 minutes
before the second plasma treatment in (e.g., step 130) is
commenced. For instance, in some cases, the water vapor is in the
chamber 215 for at least about 5 minutes and not longer than 10
minutes before the second plasma treatment is (e.g., step 130) is
commenced. It is also desirable to introduce the water vapor in a
sufficient concentration to form the desired thickness 230 of water
layer 220 and not to form an overly-thick layer 220. For instance,
in some cases, as part of step 120, introducing the water vapor
into the plasma chamber 215 includes introducing air into the
chamber, wherein the air has a humidity of least about 45 percent
at about 20.degree. C. for at least about 5 minutes, and in some
cases, not longer than about 10 minutes, before introducing the
pre-cursors molecules into the plasma chamber 215 (e.g., step
130).
[0028] In some embodiments of the process 100, a single-pass
through steps 110, 120, 130 (and sometimes optional step 140) is
sufficient to product the desired film layer 202 and therefore in
decision step 150, it is decided the target film has been achieved
and the process 100 is ceased at stop step 160. However in other
cases, if it is decided in step 150 that the film layer should
comprise multiple grafted layers 225, the process 100 can include
repeating in step 170, at least one time, each of the sequence of
steps of exposing the surface (step 110), introducing the water
vapor (step 120) and introducing the pre-cursors molecules (step
130) and sometimes optional step 140. There can be repeated passes,
e.g., a three or more passes, through steps 110, 120, 130 and
sometimes optional step 140. For instance, as further illustrated
in FIG. 2, there can be multiple pairs of retained water and
grafted layers 220, 220', 225, 225' that comprise the film 202
formed by such repeated passes in accordance with step 170.
[0029] For instance, there is no upper limit to the number post
surface activation steps and hence the number of layers of
different materials that can be deposited on the substrate surface
210. As illustrated in the examples to follow, the process 100 is
compatible with a wide range of substrate material composition and
shapes, as well as monomer chemistry types that can be deposited in
step 130. The surface characteristics of the final film 202 can be
adjusted according to the second plasma treatment conditions and
pre-cursor molecules in each pass through steps 110-140.
[0030] Presented below are examples of how the above-described
steps in the process 100 could be monitored and implemented for
particular embodiments of films 202 (sometimes referred to as a
coating herein) on various types of substrate surfaces. Additional
examples of first and second plasma treatments as part of steps 110
and 130, as also presented in U.S. application Ser. No. 12/206,013
and U.S. Provisional Application Ser. No. 60/970,582 which are
incorporated by reference if reproduced in their entirety herein.
Still other examples of first and second plasma treatments as part
of steps 110 and 130 are presented in U.S. Pat. Nos. 6,579,604 and
6,846,225 which are incorporated by reference herein in their
entirety.
[0031] A film layer 202 modification of a substrate surface 210,
such as formed in accordance with the process 100 in FIG. 1 and as
depicted in FIG. 2, can be characterized by time-of-flight
secondary ion mass spectrometry (TOF-SIMS). FIG. 3 shows a
generalized simulated expected TOF-SIMS trace of such a surface. In
this example application, "Oxide Yield" is defined as the detected
relative concentration of oxygen containing species emanating from
the sputtered surface reaching the detector of the TOF-SIMS tool.
In the trace depicted in FIG. 3, the time from T.sub.0 to T.sub.1
represents the time it takes to sputter through the outermost
graphed layer 225 in FIG. 2. The time T.sub.1 to T.sub.2 represents
the time it takes to sputter through the residual water-derived
interfacial water layer 220.
[0032] In this disclosure, atomically clean surfaces can be
characterized by time-of-flight secondary ion mass spectrometry
(TOF-SIMS) traces devoid of any elemental yields other than that of
the substrate. The suitable materials for deposition by some
embodiments of the disclosure offer a very wide range of physical,
chemical and optical properties and some are well known polymers
from bulk polymerization processes. For example, self-cleaning
barrier films or coatings that provide catalytic self-cleaning and
barrier properties (e.g., layers of TiO.sub.2 ZnO.sub.2 and
SnO.sub.2) can be formed. TiO.sub.x structures on a variety of
substrates have been demonstrated using embodiments of the process.
In this disclosure metal oxides of uncertain stoichiometry are
denoted as MO.sub.x where M=Si, Al, Ti, Ta, Zr, Zn, Sn, or Zr, and,
--O.sub.x represents oxide or sub-oxides (e.g., x=1 to 4 in some
cases).
[0033] Using the multi-stage platform for nanoscale plasma enhanced
single and multi-layered organic and ceramic nanoscale films 202
can be established on any substrate 205 of arbitrary composition
and geometry. This flexibility permits the capability to tailor the
surface modification chemistry to many applications. As an
illustrative example, FIG. 4 shows an optical interferometry of a
masked step edge silicon oxide (SiO.sub.x) plasma assisted film on
a glass substrate produced by a two-stage process where
tetraethoxysilane (TEOS) was used as the precursor molecule in the
final stage (step 130). The applied film 202 is dense, smooth and
of about 200 nm in thickness.
[0034] The specific properties of the deposited film 202 are
sensitive to the precise process conditions used in the deposition.
It is well known in the art that in the case of deposition on
thermoplastic substrates, it is important to conduct the deposition
at low temperatures to avoid dimensional distortion of the
substrate. Likewise, the process of the current invention is
designed to circumvent the typical 1-2 day surface reversion to low
energy observed for many thermoplastic substrates treated with
plasma. This invention takes advantage of the surprising beneficial
effect of humid air on the atomically cleaned substrate surface to
provide compact conformal films with excellent conformal barrier
films with excellent adhesion properties. The customized versions
of the multi-stage platform for nanoscale plasma enhanced coatings
can afford a rapid low cost method for applying application
specific coating combinations to industrial parts to improve impact
strength, abrasion resistance and corrosion resistance. Examples of
the demonstrated coatings include, but not limited to titanium
oxide coatings for glass objects, silicon oxide coatings for
corrosion resistant rotor blades and aircraft parts.
[0035] A film 202 can be formed of polymeric materials by a process
100 that includes exposing a polymeric substrate to at least two
plasma treatments (e.g., in steps 110 and 130). A first plasma
treatment creates a modified reactive surface on the substrate. The
subsequent second plasma treatment produces a grafted layer 225
thereon. The initial plasma treatment is done while controlling the
temperature of a radiofrequency electrodes to about 10 to
100.degree. C.
[0036] The specific conditions used during the first plasma
treatment can strongly influence characteristics of the polymeric
substrate's surface. For instance, different initial plasma
treatments followed by the same subsequent plasma treatment can
result in grafted layer surfaces that are either hydrophilic or
hydrophobic. The first plasma treatment can include a plasma
reactant such as Helium, Argon, Nitrogen, Neon, Silane, Hydrogen
and Oxygen and mixtures thereof. In some cases, the initial plasma
treatment reaction is conducted at a radiofrequency power of 30 to
500 Watts.
[0037] The second subsequent plasma treatment can have subsequent
plasma reactants that include vinyl or acrylic monomers. Example
monomers include monomers 1-Vinyl-2-pyrrolidinone,
2-Hydroxyethylmethacrylate, Allyl Alcohol, Allyl Amine, Substituted
Allyl Amines of 4-10 Carbon Atoms, Acrylic Acid, Acrylic Esters of
2-10 Carbon Atoms, Acrylamides of 3-10 Carbon Atoms. In some cases
the resulting surface can be used as a tie layer under a
conventional solvent, spray, dip or powder coating. The
conventional coating can then be used to bind a drug or other
therapeutic material. In other cases, the subsequent plasma
treatment can have subsequent plasma reactants that include metal
alkoxide esters of Silicon, Titanium, Tantalum, Aluminum,
Zirconium, or Zinc.
[0038] The process 100 can adapt the multi-pass plasma grafting
technique described above into a multiple step process specifically
designed for modifying and functionalizing the surfaces of medical
devices. An advantage of the method described in this application
is the ability to apply coatings on a dry-in dry-out basis, and/or
in a sterile anaerobic environments. Using this method, parts can
be placed into a treatment chamber dry and emerge after treatment
both dry and sterile. The thin film coatings produced by the
disclosed techniques are chemically bonded to the surface and are
thus highly resistant to adhesion failures, delamination, flaking
or debonding. The films are also coherent and uniform and are
resistant to decohesion and tearing. Areas of the coated devices
that need to remain non lubricious can be easily masked during the
plasma coating process. The lubricity of the coating is activated
by treatment of the surface with water or body fluids.
[0039] The so-deposited film stack 202 could be comprised of
organic and or inorganic polymers. The organic polymers are made
from monomers can be selected of a group comprising, but not
limited to, common lubricious monomers such as N-vinylpyrrolidinone
and hydroxyethylmethacrylate and their copolymers ethylene and
propylene oxide and their derivatives. The polymers are created
in-situ at the substrate surface from treatment of the substrate in
the plasma/monomer environment.
[0040] These plasma created polymer coatings provide lubricity when
contacted with water or saline solution. The coated device is dry
to the touch prior to water treatment for facile handling by
medical or surgical personnel. The mechanical properties of the
coatings, such as the flexibility of the deposited coating, can be
modified by incorporation during the plasma polymerization of
volatile crosslinking agents such as diallylethers,
polyallylamines, gylcoldiacrylates or glycoldimethacrylates into
the monomer stream. Monomers with reactive functional groups
containing amine, hydroxyl, and carboxylic acid functional groups
can provide sites for the further coupling of surface binding or
other materials and polymers, including designer drugs for targeted
delivery. For example, known lubricious urethane polymers can be
attached to preceding layers containing these reactive surfaces.
Further, direct attachment or binding of gel mixtures of antibiotic
or other drugs can be accomplished using standard solution coating
or gas phase under non-plasma vacuum/reduced pressure techniques.
The coatings of this invention, including common lubricious
monomers such as N-vinylpyrrolidinone, which provides lubricity
when contacted with water or saline solution, have been applied on
a dry-in/dry-out basis. The coated device is dry to the touch prior
to water treatment for facile handling by medical or surgical
personnel. Further, coating of monomers with reactive handles
containing amine, hydroxyl, and carboxylic acid functional groups
can provide sites for the surface binding of antibiotic or other
drugs have been demonstrated.
[0041] Table 1 is a compendium of the conditions in a coating
processes on miscellaneous substrates using the process 100 which
includes two steps: a first plasma treatment in accordance with
step 110 (step P1) and a second plasma treatment in accordance with
step 130 (step P2), and the characterization data of the resultant
articles. The substrates used in these experiments were made from
polymers commonly associated with biomedical devices. In all cases,
the modified surfaces showed permanent improvements in their
hydrophilic (reduced water contact angles relative to the untreated
substrates)
TABLE-US-00001 TABLE 1 A compendium of the processing conditions,
and the characterization data of the resultant articles. The first
plasma treatment (P1 stage) and second plasma treatment (P2 stage)
are interspersed with humid air exposure in accordance with step
120. P1 P2 Sample P1 RF P1 P1 Pres- P2 P2 RF P2 RF P2 Pres- ID
Substrates Power Time Gas sure Monomer Power Time Gas sure 1-10A
Tygon Tubing NA NA NA NA NA NA NA NA NA 1-10B Tygon Tubing 50 4 20%
O2, 350 TYZOR TPT 50 20 Ar 350 80% Ar 1-3B Tygon Tubing 100 15 Ar
250 TEOS 50 20 Ar 250 1-5A Tygon Tubing 100 15 Ar 250
2-Hydroxyethyl 50 20 Ar 250 Methracrylate 1-2B Tygon Tubing 100 15
250 N-Vinylpyrrolidinone 50 20 Ar 250 1-11A Red Rubber 50 3 20% O2,
350 Hexamethyldisilazane 50 20 Ar 350 Bard Urethral 80% Ar Catheter
1-5E Lexan Panel 50 5.5 20% O2, 350 2-Hydroxyethyl 50 20 Ar 350 80%
Ar Methracrylate 1-10C Polycarbonate 50 4 20% O2, 350 TYZOR TPT 50
20 Ar 350 Panels 80% Ar 1-5A Silicone Medical 100 15 Ar 250
2-Hydroxyethyl 50 20 Ar 250 Tubing Methracrylate 1-3C Silicone
Medical 100 15 Ar 250 TEOS 50 20 Ar 250 Tubing 1-3C Silicone
Medical 100 15 Ar 250 TEOS 50 20 Ar 250 Tubing 1-3D Epoxy/Graphite
100 15 Ar 250 TEOS 50 20 Ar 250 Cylinder 1-3B Latex Gloves 100 15
Ar 250 TEOS 50 20 Ar 250 1-10D Latex Gloves 50 4 20% O2, 350 TYZOR
TPT 50 20 Ar 350 80% Ar 1-5A Latex Gloves 100 15 Ar 250
2-Hydroxyethyl 50 20 Ar 250 Methracrylate
[0042] The data in Table 1 shows that the process conditions used
in the atomic cleaning and activation step P1 (step 110 of FIG. 1)
strongly influence the eventual surface characteristics. For
example, starting with same substrate and finishing with identical
monomer and plasma step P2 conditions, sample 1-3F is hydrophilic
while sample 1-5D is hydrophobic. The principal difference is in
the plasma step P1 process condition; the process gas composition,
plasma power and time were different.
TABLE-US-00002 TABLE 2 A compendium of the 2-Step processing
conditions of Miscellaneous Substrates, and the characterization
data of the resultant articles. The P1 and P2 stages are
interspersed with humid air exposure in accordance with step 120.
P1 RF P1 P1 P2 RF P2 P2 Contact Substrates Power Time P1 Gas
Pressure P2 Monomer Power Time P2 Gas Pressure Angle Tygon Tubing
NA NA NA NA NA NA NA NA NA 102 Tygon Tubing 50 4 20% O2, 350 TYZOR
TPT 50 20 Ar 350 82 80% Ar Tygon Tubing 100 15 Ar 250 TEOS 50 20 Ar
250 TygonTubing 100 15 Ar 250 2-Hydroxyethyl 50 20 Ar 250
Methracrylate Tygon Tubing 100 15 250 N-Vinylpyrrolidinone 50 20 Ar
250 69 Red Rubber Bard 50 3 20% O2, 350 Hexamethyldisilazane 50 20
Ar 350 70 Urethral Catheter 80% Ar Lexan Panel 50 5.5 20% O2, 350
2-Hydroxyethyl 50 20 Ar 350 80% Ar Methracrylate Polycarbonate
Panels 50 4 20% O2, 350 TYZOR TPT 50 20 Ar 350 80% Ar Silicone
Medical 100 15 Ar 250 2-Hydroxyethyl 50 20 Ar 250 Tubing
Methracrylate Silicone Medical 100 15 Ar 250 TEOS 50 20 Ar 250
Tubing Silicone Medical 100 15 Ar 250 TEOS 50 20 Ar 250 Tubing
Epoxy/Graphite 100 15 Ar 250 TEOS 50 20 Ar 250 Cylinder Latex
Gloves 100 15 Ar 250 TEOS 50 20 Ar 250 Latex Gloves 50 4 20% O2,
350 TYZOR TPT 50 20 Ar 350 80% Ar
[0043] In some embodiments, substrates 205 comprising feeding tube
connectors and balloon catheters are surface modified by of the
process 100 resulting in a graphed layer 225 of an elastomeric
conformal coating. In such an embodiments of the precursor molecule
of step 130 can include polymerize 2-methyl-1,3-butadiene
(isoprene) onto a variety of substrates using a single pass through
of the process 100 (steps 110-130, and in in some cases step 140).
This is a special case of the general olefin polymerization
process, since a coating is produced which can be further
cross-linked by plasma post treatment or by other means
[0044] In some embodiments, device substrates 205 benefit from a
dry low friction, biologically inert grafted layer 225 surface with
low adhesion to the biological tissues. These surfaces can be
described as "dry lubricious". Such surfaces are useful in
particular for invasive medical devices such as catheters,
arthroscopic tubes and implements. Implements of this type are
advantageous during surgical insertion since no additional surface
treatment water or external fluids are required during insertion.
Some such embodiments of the disclosure use commercially available
fluoro-monomers in producing low energy, hydrophobic, low
coefficient of friction coatings via our two stage plasma coating
process.
[0045] In some cases, the process 100 comprises a first grafted
layer 225 of a conformal organic coating and subsequent grafted
layers 225' (one or more repeated passes in accordance with step
170) of a plasma-assisted deposited, ceramic metal oxide coating.
The forming of a plurality of subsequent grafted layers 225' (and
in some cases water subsequent layers 220') where there exists one
or more subsequent grafted layer 225 and (in some cases subsequent
water layer 220) can in some cases include in step 110 exposing the
upper-most preceding grafted layer 225 to a short burst of inert
gas plasma designed to clean at the atomic level and to activate
the surface of the preceding grafted layer 225, and then exposure
to humid air in step 120, followed by plasma assisted deposition of
a thin film comprised of ceramic metal oxide of ceramic-polymer
hybrid conformal surface in step 130. In some cases, the ceramic
metal oxide is in step 130 chosen from the group of Si, Al, Ti, Ta,
Zr, Zn, Sn, Zr. The ceramic metal sub-oxide is chosen from the
group of Si, Al, Ti, Zr, Zn, Sn, Zr.
[0046] In other cases, the subsequent graphed layer 225' can be
another conformal organic coating such as an olefinic deposited
conformal surface. In some cases, one or both the preceding graphed
layer 225 and subsequent graphed layer 225' includes an olefinic
precursor molecules chosen from the group of tyrene, 1-Hexene, or
isoprene. In some cases, one or both the preceding graphed layer
225 and subsequent graphed layer 225' includes an olefinic
precursor molecules that are paracyclophanes, such as parylene. In
some cases, the organic coating is an olefinic hydrocarbon of 4-15
carbon atoms. In some cases, the organic coating is styrene. In
some cases, one or both the preceding graphed layer 225 and
subsequent graphed layer 225' includes an olefinic precursor
molecules that are olefinic hydrocarbon of 4-15 carbon atoms.
[0047] In some embodiments, the precursor molecule used in step 130
is a monomer selected for subsequent direct chemical reaction
binding of the grafted layer 225 to the substrate surface 110 are
taken from the group of: acrylic acid, primary and acrylamides of
up to 10 carbon atoms, allyl alcohol, primary and secondary
allylamines up to 15 carbon atoms, allylglycidylether,
hydroxyethylacrylate and methacrylate, hydroxypropylacrylate and
methacrylate. In some embodiments the precursor molecules used in
step 130 is 4-diallylaminopyridine. In some cases the subsequent
grafted layer 225' can be fromed from precursor molecules of
acrylic and methacrylic acids, tertiary allylamines in some cases
4-diallylaminopyridine.
[0048] In some embodiments, the film layer 202 produced is active
in destroying chemical warfare agents. In some cases, the film
produced is active in destroying toxic industrial fluids. In some
cases, the film produced by the current invention is active in
destroying organic molecules under electromagnetic wave
irradiation. In some cases, the film 202 produced is active in
destroying metal-organic complex molecules under electromagnetic
wave irradiation.
[0049] In some embodiments the precursor molecule used in step 130
provides a conformal inert hydrogenated amorphous carbon film
coating 202, in some cases containing sp3 and sp2 hybridized
carbon, as well as C--H bonds, e.g., formed from precursor
molecules that include volatile carbon-rich fluids such as one or
more of carbon tetrachloride, chloroform, benzene, and xylene In
some cases, the subsequent or second grafted layer 225 is a
conformal inert hydrogenated amorphous carbon film coatings, formed
in a repeated pass in accordance with step 170.
[0050] In some embodiments, the precursor molecule used in step 130
provides a conformal electrically and or thermally conducting film
202, e.g., formed from precursor molecules that include pyrrole,
thiophene and aniline.
[0051] Some further illustrative examples of films 202 formed in
accordance with the process 100 as presented below:
Example 1
[0052] Polypropylene tubes, polyethylene test tubes, aluminum
sheet, and masked glass microscope slides, were placed in a plasma
deposition chamber held between 0.degree. C. and 100.degree. C. and
activated with Argon plasma at pressures between 50 and 500 mTorr
at power between 50 and 200 Watts. Following activation, humid air
or water saturated air was allowed to bleed into the deposition
chamber until the chamber pressure reached 1 atmosphere, and then
the system was evacuated to base pressure. The plasma assisted
deposition stage was then initiated. Hexafluoropropylene was
introduced into the plasma chamber under Argon plasma at pressures
from 100 to 500 mTorr and power between 50 and 250 Watts and
treatment was continued for between 15 to 60 minutes.
[0053] The process produced a yellow conformal coating. The
thickness of the coating increased monotonically with increasing
stage-two treatment time, reaching a thickness of about 100 nm in
60 minutes on all of the test surfaces. This suggests that the film
deposition rate depended on the reactive precursor species reaching
the activated surface, where it is readily incorporated into the
growing film.
[0054] The films produced on all the test surfaces were smooth and
hydrophobic, with static water contact angles of between
120.degree.-125.degree. C. and no contact hysteresis. The films
were also highly adherent to the substrates, based on the results
from a modified qualitative "Scotch tape peel" tests. In these
tests, a piece of Scotch.TM. brand tape was firmly pressed onto the
coated substrate for 5 minutes and then quickly removed at
90-degrees. If little or none of the yellowish coating was peeled
substrate surface, then the adhesion of the film to the substrate
is considered good. All the tested samples, produced in this
example passed this test.
Example 2
[0055] Experiments were conducted to evaluate the efficacy of
various barrier coatings in protecting electronic circuitry. In
this example, the ability to reduce the shifts caused by
autoclaving in the air flow characteristic of arthroscopic
flow-meters was evaluated. The device was built as normal,
calibrated for air flow and verified in normal ambient tests. The
devices were then disassembled, and the control electronics coated
by the methods of this invention, as described below. The devices
were then reassembled with coated electronics boards then retested
for air flow at pre-determined set points.
[0056] In one embodiment, an electronic board previously coated
with Parylene-C was subjected to a two stage plasma activation and
deposition process. The first stage was carried out in argon plasma
at 250 mTorr at 100 W power for up to 5 minutes. Following
activation, humid air or water saturated air was allowed to bleed
into the deposition chamber, which was partially pre-filled with an
inert gas, until the chamber pressure reached 1 atmosphere, and
then the system was evacuated to base pressure, backfilled with the
inert gas and pumped down to base pressure twice before the plasma
assisted deposition stage was then initiated. In the plasma
assisted deposition stage, subsequent, tetraethyloxyorthosilane
[TEOS] was introduced and plasma conditions of 250 mTorr and 100 W
maintained for 25 minutes to yield a conformal SiO.sub.x
overcoating.
[0057] In another embodiment, a circuit board controller was first
subjected to a two stage plasma activation and deposition process.
The first stage was carried out in argon plasma at 250 mTorr at 100
W power for up to 5 minutes. In the plasma assisted deposition
stage, Tetraethyloxyorthosilane [TEOS] was introduced and plasma
conditions of 250 mTorr and 100 W maintained for 25 minutes to
yield a conformal SiO.sub.x coating. This was followed by thermal
vapor coating with Parylene-C, and then finally coated again with
the two stage plasma process, interspersed with humid-air breaks of
Example 1 to create a three layer conformal barrier coating.
[0058] The electronic control boards were evaluated using a
modified unbiased autoclave test (JEDEC Standard JESD22-A102,
http:www.jedec.org, incorporated by reference herein in its
entirety). The JEDEC Standard JESD22-A102 test is a highly
accelerated test which employs conditions of pressure, humidity and
temperature under condensing conditions to accelerate moisture
penetration through the external coating materials and along the
interface between the external protective film material and the
underlying metallic components. The autoclave test used to simulate
device survivability in harsh conditions and/or long-term
reliability testing. The circuit boards were subjected to multiple
heat and cool cycles.
[0059] Large air flow deviations at low flow set points are
characteristics of the flow meters tested in this example, and such
deviations were used as index of flow meter performance. In these
tests. The failure criterion is a flow deviation at 20%; any device
showing flow deviation of greater than 20% at any gas flow set
point is considered to have failed.
[0060] FIG. 5 and Table 4 summarize the results from these tests.
The results clearly show that the under- and over-coat of parlyene
with SiO.sub.x from the current invention significantly improved
the performance and the long-term reliability of the control
electronics evaluated.
TABLE-US-00003 TABLE 3 Summary of the results from Autoclave
Cycling tests in Example 2 Max Number of Coating Type Cycles Before
Fail None 0 40 nm Parylene Only 10 40 nm Parlyene + 100 nm SiO2
Overcoat >20 100 nm SiO2 undercoat/40 nm Parlyene/100 nm >20
SiO2 overcoat
Example 3
[0061] Polyethylene blow-molded fuel tanks for small engines were
sealed to mitigate permeation of hydrocarbon fluids. The untreated
tanks have inherent permeability of hydrocarbon fluids and the
current state of the art mitigation treatments, such as gaseous
fluorination of the tank surfaces in large chambers and multilayer
polymer co-extrusion are environmentally less preferred and capital
intensive respectively.
[0062] A commercial polyethylene blow molded small engine fuel tank
(e.g., obtained from Mergon Corporation, Anderson, SC) was coated
with SiO.sub.x using the process of this invention. The blow molded
fuel tanks were coated in the two stage plasma process consisting
of a plasma activation stage from 2-10 minutes at 50-100 W Argon
plasma at 100-500 MTorr, preferably at 250 mTorr, followed by a
plasma grafting stage, where Tetraethyloxyorthosilane [TEOS] was
introduced. The plasma conditions of the grafing stage were 100-250
MTorr and 100 W maintained for 25 minutes. The resultant thickness
of the conformal SiO.sub.x over-coating was about 150 nm.
[0063] To evaluate the effectiveness of the coatings in suppressing
fuel loss, the coated tanks were filled with commercial 87 octane
gasoline, closed with a commercial small engine fuel tank cap,
placed in a covered, 10 gallon polyethylene buckets, and stored at
room temperature for 26 months. Identical, but uncoated control
tanks were likewise filled and similarly stored. After 26 months,
the mean net weight of the fuel remaining in the coated tanks was
397 g, as compared to 372 g remaining in the uncoated tanks. This
demonstrates that the conformal coatings from this invention
deposited on the fuel tanks were effective in mitigating
hydrocarbon fuel loss due to permeation polyethylene blow molded
fuel tank.
Example 4
[0064] In a series of demonstration experiments, multi stage plasma
based coatings were produced with a variety of olefinic monomers
(Styrene, 1-Hexene, Isoprene) in the subsequent grafting stage to
produce nanoscale conformal barrier coatings. The substrates were
coated in the two stage plasma process consisting of a plasma
activation stage from 1-10 minutes at 50-100 W argon plasma at
100-500 mTorr, preferably at 250 mTorr, followed by a plasma
grafting stage, where olefinic monomers were introduced. The plasma
conditions of the grafting stage were 100-250 mTorr, and preferably
100 W maintained for up to 30 minutes. Coatings were applied to
polypropylene and polyethylene tubes, polycarbonate and acrylic
sheets, aluminum sheets, and borosilicate glass slide substrates.
The coatings were uniform, smooth and adherent between 60 and 200
nm in thickness deepening on specific process conditions. FIG. 6
shows an optical interferometry example image of an example 60 nm
styrene coating edge on a de-masked borosilicate glass sample.
[0065] Other functional olefinic monomers can likewise be employed
by the methods of this invention to produce reactive grafted
surface polymers.
Example 5
[0066] The reactive surfaces demonstrated in example 4 can be
employed as tie and/or priming coats and sub-coats to bind other
materials to the surface or to catalyze chemical reactions at the
surface. In example 1, the grafting of allyl alcohol and allylamine
to a variety of substrates were demonstrated. In this example,
other suitable monomers such as allylglycidylether, were used to
graft a reactive epoxy coating onto the substrate, and then used to
couple 4-diallylaminopyridine, to produce a grafted
dialkylaminopyridine catalytic surface. Polymeric
dialkylaminopyridines have been shown to be useful in catalyzing
the destruction of chemical warfare agents and toxic industrial
materials. (See e.g., Yokley and Nielsen, US Patent Application,
US20110028774, Hypernucleophilic Catalysts for Detoxification of
Chemical Threat Agents, incorporated by reference herein in its
entirety).
Example 6
[0067] Electrically conducting coatings were applied to
polypropylene and polyethylene tubes, polycarbonate and acrylic
sheets, aluminum sheets, borosilicate glass slides and on
inter-digitated conductive test structures; the substrates were
treated in a two phase plasma coating process. The activation phase
was conducted at 75 W power at 300 mTorr pressure using a 67% argon
and 33% air plasma for 2 minutes. The subsequent phase admitted
pyrrole into the plasma chamber at a pressure ranging from 300-400
mTorr for 75 W for 30 minutes. The chamber temperature rose from
12.degree. C. to 18.degree. C.
[0068] A thin colorless conformal coating of about 12 nm in
thickness was deposited as characterized with an optical
interferometry. The coatings were uniform, smooth and adherent. The
electrical conductivity of the prepared conducting polymer films
(comprised of mostly polypyrrole) was measured at room temperature
by four-point probe technique, taking the average value of several
readings at various points of the films. The electrical data varied
significantly from site to site over the samples, and from sample
to sample. The best conductivity of the as-deposited undoped films
measured was about 1.times.10.sup.-2 S/cm.
Example 7
[0069] Inert hydrogenated amorphous carbon film coatings (possibly
containing sp3 and sp2 hybridized carbon, as well as C--H bonds)
were applied to polypropylene and polyethylene tubes, polycarbonate
and acrylic sheets, aluminum sheets, and glass slides; the
substrates were treated in a two phase plasma coating process. The
activation phase was conducted for 2 minutes at 175-300 mTorr and
75 W power, with argon as the background gas. In one embodiment,
Carbon Tetrachloride (CCl.sub.4) was introduced into the plasma
chamber with argon as the carrier and background gas in the
subsequent phase, at 75 W power and 175-300 mTorr for 30 minutes.
In another embodiment, xylene (C.sub.7H.sub.8) was introduced into
the plasma chamber with argon as the carrier and background gas in
the subsequent phase, also at 75 W power and 175-300 mTorr for 30
minutes.
[0070] In both embodiments, the process produced a colorless
conformal and hydrophobic coating. The thickness of the coating
increased monotonically with increasing stage-two treatment time,
reaching a thickness of about 150 nm in 30 minutes on all of the
test surfaces. This suggests that the film deposition rate was
independent of the carbon source, but depended only on the reactive
precursor species reaching the activated surface, where it is
readily incorporated into the growing film.
Example 8
[0071] Specialty filtration membranes and related devices are
becoming an integral part of bioprocessing, semiconductor and other
high value industrial processes. Likewise, micro-reactor technology
where the configurations take advantage of high reactor surface to
volume ratios to achieve specific surface binding of catalysts or
other reaction modifiers are becoming items of intense study. In
most cases the filter media are made from chemically inert and low
surface energy materials such as polyethylene, polypropylene, other
polyolefins or polysulfone. The coatings of this invention have the
ability to directly and selectively modify the chemical properties
of channels, micro-pinholes and tortuous paths of specific filters.
The coatings of this invention are uniquely able to perform these
operations since the activation is driven by the plasma which
accesses all surfaces within the plasma reaction chamber, and the
volatile monomers are delivered to the activated surface sites in
the gas phase. The advantages of a rapid, general, and chemically
flexible system that can be used on finished configurations on a
dry-in/dry-out basis are clearly evident to those skilled in the
art.
[0072] In this example, an embodiment of the process 100 of the
disclosure was used to modify a variety of filter membranes
materials, to create surfaces capable of binding metal ions through
dative bonding. For example, by functionalizing the membrane with
soft ligands (e.g., aliphatic-, thiols, amines, etc.) one can
selectively bind coinage metal ions (Ag, Au, etc. . . . ).
Specifically, the allyamine surfaces created in example 1, bind
copper ions, and were used to reduce the concentration of Cu.sup.2+
in aqueous solutions placed in contact with such surfaces.
Example 9
[0073] The performance of polyvinylalcohol (PVA) objects (e.g. PVA
brushes) in aqueous environments are constrained by, but not
limited to, the difficulties in hydration (requiring brushes to
shipped in wet envelopes), bio-fouling (bacteria growth in the
brushes leading to high particle count) and lack of application
specificity ('one-size fits all' approach, use the same brush for
all substrate)
[0074] Current efforts to address these concerns utilize
modifications to the composition of the aqueous environments (e.g.,
cleaning solutions, etc.). Such modifications are not always
successful. We propose to mitigate these limitations, without
negatively impacting performance, with appropriate choice of
secondary coatings on the brush bristles.
[0075] Specifically, using the inventions in this disclosure the
inventors successfully modified commercial PVA brushes with
secondary coatings that bind detrimental metallic species, such as
Cu- and other metallic ions, to proactively address yield and
reliability limiting dielectric contamination in semiconductor
manufacturing. By appropriate choice of such coatings, it is
possible to also prevent bio-fouling (bacteria growth in the
brushes leading to high particle count) and lack of application
specificity.
Example 10
[0076] The effects of sand erosion and/or ablation on helicopter
rotors blades is a perennial problem in sandy environments and
rotor blade replacement represents a significant cost over a
helicopter's operational life. Most helicopter rotor blades include
erosion protection in the form of leading edge strips made from
metals such as nickel, titanium and stainless steel.
Polyurethane-based coatings, tapes and boots have also been used
for erosion protection. However, neither strategy gives optimal
erosion resistance from both rain and sand. Metal leading edges
have excellent rain resistance but poor sand erosion performance.
Conversely, polyurethane-based coatings have good sand erosion
protection, but poor rain resistance.
[0077] Increased durability of ceramic modified thermoplastics in
corrosive aqueous abrasive environments have been demonstrated. In
particular, two stage plasma based coatings of this invention of
SiO.sub.x and TiO.sub.x to both thermoplastic and thermoset
materials are used to improve durability. The coatings of this
invention, in particular the inorganic oxides as applied to the
previously described polyurethane rotor protection boots can
provide effective aqueous surface protection in a high abrasive
environment.
[0078] Those skilled in the art to which the invention relates will
appreciate that other and further additions, deletions,
substitutions and modifications may be made to the described
embodiments without departing from the scope of the invention.
* * * * *