U.S. patent application number 10/779146 was filed with the patent office on 2004-08-19 for method for coating implantable devices.
This patent application is currently assigned to Medtronic, Inc.. Invention is credited to Haller, Markus, Keeney, Kenneth W., Martinez, Gonzalo, Taylor, Catherine E..
Application Number | 20040161528 10/779146 |
Document ID | / |
Family ID | 23333369 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040161528 |
Kind Code |
A1 |
Martinez, Gonzalo ; et
al. |
August 19, 2004 |
Method for coating implantable devices
Abstract
Coating an implantable device, such as micro electromechanical
devices, is highly desirable to protect the implantable device from
corrosion. A coating method includes depositing, preferably by
plasma glow discharge, a reactant monomer on at least one surface
of an implantable device, preferably at ambient temperature. The
method will likely decrease the manufacturing time required for
assembling such devices because completely assembled devices can be
coated.
Inventors: |
Martinez, Gonzalo; (Mendota
Heights, MN) ; Taylor, Catherine E.; (Minneapolis,
MN) ; Keeney, Kenneth W.; (Forest Lake Township,
MN) ; Haller, Markus; (Begnins, CH) |
Correspondence
Address: |
MEDTRONIC, INC.
710 MEDTRONIC PARKWAY NE
MS-LC340
MINNEAPOLIS
MN
55432-5604
US
|
Assignee: |
Medtronic, Inc.
|
Family ID: |
23333369 |
Appl. No.: |
10/779146 |
Filed: |
February 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10779146 |
Feb 13, 2004 |
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09340441 |
Jun 28, 1999 |
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6692834 |
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Current U.S.
Class: |
427/2.24 ;
427/569 |
Current CPC
Class: |
C23C 16/0245 20130101;
B05D 1/62 20130101; C23C 16/30 20130101; B05D 3/142 20130101; A61L
31/08 20130101 |
Class at
Publication: |
427/002.24 ;
427/569 |
International
Class: |
A61L 002/00 |
Claims
What is claimed is:
1. A method for coating a surface of an implantable device
comprising: plasma pretreating at least one surface of the
implantable device with an inert gas; providing the implantable
device to a plasma reaction chamber; and plasma treating the at
least one surface of the implantable device with a reactant monomer
to form a coating thereon.
2. The method of claim 1, wherein plasma treating the at least one
surface comprises a low temperature within the reaction
chamber.
3. The method of claim 1, wherein the reactant monomer is selected
from the group consisting of a substituted or unsubstituted alkene,
arene, silane, siloxane, and a combination thereof.
4. The method of claim 3, wherein the reactant monomer is selected
from the group consisting of ethylene, 2-methyl-1-pentene, xylene,
divinylmethylsilane, hexamethyldisilane, tetramethylsiloxane, and a
combination thereof.
5. The method of claim 1, wherein plasma treating the at least one
surface comprises creating a glow discharge of the reactant monomer
in the presence of an inert gas.
6. The method of claim 5, wherein the inert gas is selected from
the group of argon, helium, nitrogen, neon, and a combination
thereof.
7. The method of claim 5, wherein the reactant monomer is in a
ratio with the inert gas of about 3 parts to about 6 parts reactant
monomer to about 1 part inert gas.
8. The method of claim 1, wherein plasma treating the at least one
surface comprises creating a glow discharge of the reactant monomer
using a power of about 30 Watts to about 100 Watts for a time
period from about 10 minutes or less.
9. The method of claim 1, wherein plasma pretreating the at least
one surface comprises supplying the inert gas to the reaction
chamber at a flow rate of about 2 sccm.
10. The method of claim 1, wherein plasma pretreating the at least
one surface comprises a pressure within the reaction chamber of
about 5 mTorr to about 15 mTorr.
11. The method of claim 1, wherein plasma pretreating the at least
one surface comprises generating a glow discharge of the inert gas
using an R.F. power of about 100 Watts for a time of about 2
minutes or less.
12. The method of claim 1 further comprising cleaning the at least
one surface prior to plasma treating the at least one surface with
a reactant monomer.
13. The method of claim 1, wherein plasma treating the at least one
surface with the reactant monomer comprises a pressure within the
reaction chamber of about 0.025 Torr to about 0.1 Torr.
14. The method of claim 1 further comprising adding a polymer to
the at least one surface having the coating thereon, wherein the
polymer is selected from the group consisting of a natural
hydrogel, a synthetic hydrogel, silicone, polyurethane,
polysulfone, cellulose, polyethylene, polypropylene, polyamide,
polyimide, polyester, polytetrafluoroethylene, polyvinyl chloride,
epoxy, phenolic, neoprene, polyisoprene, and a combination
thereof.
15. The method of claim 1 further comprising adding a bio-active
compound to the at least one surface having the coating
thereon.
16. The method of claim 15, wherein the bio-active compound is
selected from the group consisting of an antithrombotic agent, an
antiplatelet agent, an antimitotic agent, an antioxidant, an
antimetabolite agent, an anti-inflammatory agent, and a combination
thereof.
17. The method of claim 1, wherein the implantable device is
selected from the group consisting of a pacemaker, a
pacemaker-cardioverter-defibrillat- or, an implantable
neurostimulator, a muscle stimulator, an implantable monitoring
device, an implantable fluid handling device, a defibrillator, a
cardioverter/defibrillator, a gastric stimulator, a drug pump, and
a hemodynamic monitoring device.
18. An implantable device comprising at least one surface coated by
the method according to claim 1.
19. The implantable device of claim 1, wherein the coating has a
thickness of about 200 .DELTA. to about 2000 .DELTA..
20. The implantable device of claim 1, wherein the at least one
surface comprises a metal, a nonmetal, and a combination
thereof.
21. An implantable device comprising at least one surface having a
coating formed thereon from a compound selected from the group
consisting of ethylene, 2-methyl-1-pentene, xylene,
divinylmethylsilane, hexamethyldisilane, and tetramethylsiloxane.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for coating micro
electromechanical devices to provide coatings on such devices that
are relatively corrosion-resistant and suitable for in vivo
implantation, such as within a human body.
BACKGROUND
[0002] In many medical situations, it is desirable and often
necessary to implant relatively small (micro) electromechanical
devices for an extended period of time. For example, it may be
desirable to continually administer fluid medication (either as a
gas or a liquid) to a patient over an extended period of time.
Examples of such treatments included the low dose continual
administration of morphine for pain control, the administration of
FUDR for cancer chemotherapy, the administration of baclofen for
the treatment of intractable spasticity, and the like.
[0003] In such instances, a particularly desirable goal is to
maintain a relatively constant level of medication in the patient's
bloodstream. In order to accomplish this goal, relatively small
fluid handling devices are implanted within a patient's body.
However, both the medication and bodily fluids that may contact the
micro fluid handling devices are typically corrosive. Thus, it is
desirable to provide a corrosion-resistant layer to at least one
surface of the micro fluid handling device to prevent or limit
corrosion. For example, a nominal layer of a corrosion-resistant
substance may be deposited on a substrate by sputtering by using an
e-beam evaporator, where suitable corrosion-resistant substances
may be silicon, gold, platinum, chrome, titanium, zirconium, and
oxides of silicon or these metals. See, U.S. Pat. Nos. 5,660,728;
5,702,618; and 5,705,070 all to Saaski et al. It is described that
the oxides may be formed by thermally oxidizing the
corrosion-resistant substance in air after it has been applied to
the substrate.
SUMMARY OF THE INVENTION
[0004] What is yet needed is a method for coating micro
electromechanical devices that provides a relatively
corrosion-resistant and electrically insulating coating on at least
one surface of the device. Furthermore, it is highly desirable to
coat the device at a relatively low temperature that will likely
increase the fabrication process because substantially all of the
device components and features can be assembled prior to coating
the device. For example, in a typical device fabrication process, a
corrosion-resistant coating is applied to individual components
along the fabrication process but prior to complete assembly of the
device. Because typical coating methods utilize relatively high
temperatures, coating a completely assembled device is generally
not possible because the relatively high coating temperatures tend
to be detrimental to electrical components that, in turn, may
ultimately adversely affect the functioning of the device.
[0005] As used herein, "corrosion" refers to a complex
electrochemical degradation of a conductive material (such as a
metal or a metal alloy) or a semiconductive material (such as
silicon or carbon) due to a reaction between such materials and the
environment, usually an aqueous electrolyte-containing environment
that can be an acidic or basic (alkaline) environment. In general,
a corrosion product of such a material is in the form of an oxide
of the material, such as a metal oxide, silicon dioxide, and the
like. While not wishing to be bound by any particular theory, it is
believed that corrosion occurs when the material (such as copper or
silicon) contacts an electolytic solution and a
mini-electrochemical circuit is formed when a small amount of the
material dissolves in the water and combines with oxygen or other
dissolved species. In forming the mini-electrochemical circuit, an
imbalance of electrons between the solution and the surrounding
material creates a minute flow of electrons, or current. So long as
a current is allowed to flow, the material will continue to
deteriorate, resulting in degradation and even pitting of the
material. An electrically insulating coating is one that prevents
completion of the current in the "minielectrochemical curcuit."
[0006] Accordingly, one aspect of the present invention provides a
method for coating an implantable device. Preferably, coating the
implantable device is accomplished at a low temperature. "Low
temperature," as used herein, means that an input of energy to
increase the temperature during plasma deposition is not required.
In accordance with the present invention, plasma deposition
preferably occurs at about ambient temperature, typically from
about 20EC to about 30EC.
[0007] A method for coating a surface of an implantable device
preferably includes plasma pretreating at least one surface of the
implantable device with an inert gas; providing the implantable
device to a plasma reaction chamber; and plasma treating the at
least one surface of the implantable device with a reactant monomer
to form a coating thereon. "Inert" refers to relative chemical
inactivity of a compound under ambient conditions however, under
some plasma deposition conditions the "inert" compound may become
reactive when a glow discharge of the compound is created.
[0008] Preferably, the reactant monomer is selected from the group
consisting of a substituted or unsubstituted alkene, arene, silane,
siloxane, and a combination thereof. More preferably, the reactant
monomer is selected from the group consisting of ethylene,
2-methyl-1-pentene, xylene, divinylmethylsilane,
hexamethyldisilane, tetramethylsiloxane, and a combination
thereof.
[0009] A method in accordance with the present invention preferably
includes plasma treating the at least one surface by creating a
glow discharge of the reactant monomer in the presence of an inert
gas. The inert gas is preferably selected from the group of argon,
helium, nitrogen, neon, and a combination thereof. The reactant
monomer is preferably in a ratio with the inert gas of about 3
parts to about 6 parts reactant monomer to about 1 part inert
gas.
[0010] A method in accordance with the present invention preferably
includes plasma treating the at least one surface by creating a
glow discharge of the reactant monomer using a power of about 30
Watts to about 100 Watts for a time period from about 10 minutes or
less. Preferably, the method includes a pressure within the
reaction chamber of about 0.025 Torr to about 0.1 Torr.
[0011] In accordance with the present invention, plasma pretreating
the at least one surface includes supplying the inert gas to the
reaction chamber at a flow rate of about 2 sccm. Preferably, plasma
pretreating the at least one surface includes a pressure in the
reaction chamber of about 5 mTorr to about 15 mTorr. Plasma
pretreating the at least one surface preferably includes generating
a glow discharge of the inert gas using radio frequency
(abbreviated herein "R.F.") power of about 100 Watts for a time of
about 2 minutes or less.
[0012] Additionally, a method in accordance with the present
invention may further include cleaning the at least one surface
prior to plasma treating the at least one surface with a reactant
monomer. Preferably, cleaning the at least one surface is
accomplished prior to plasma pretreating the at least one
surface.
[0013] Also in accordance with the present invention, the method
may further include adding a polymer to the at least one surface
having a coating thereon, wherein the polymer is selected from the
group consisting of a natural hydrogel, a synthetic hydrogel,
silicone, polyurethane, polysulfone, cellulose, polyethylene,
polypropylene, polyamide, polyimide, polyester,
polytetrafluoroethylene, polyvinyl chloride, epoxy, phenolic,
neoprene, polyisoprene, and a combination thereof. The method may
also include adding a bio-active compound to the at least one
surface having a coating thereon. Preferably, the bio-active
compound is selected from the group consisting of an antithrombotic
agent, an antiplatelet agent, an antimitotic agent, an antioxidant,
an antimetabolite agent, an anti-inflammatory agent, and a
combination thereof.
[0014] An implantable device coated in accordance with the present
invention can be selected from the group consisting of a pacemaker,
a pacemaker-cardioverter-defibrillator, an implantable
neurostimulator, a muscle stimulator, an implantable monitoring
device, an implantable fluid handling device, a defibrillator, a
cardioverter/defibrillator, a gastric stimulator, a drug pump, and
a hemodynamic monitoring device.
[0015] Another aspect of the present invention provides an
implantable device including at least one surface coating formed by
the method described above. Preferably, the coating has a thickness
of about 200 .DELTA. to about 2000 .DELTA.. In accordance with the
present invention, the at least one surface can include a metal, a
nonmetal, and a combination thereof.
[0016] Yet another aspect of the present invention provides an
implantable device including at least one surface having a coating
formed thereon from a compound selected from the group consisting
of ethylene, 2-methyl-1-pentene, xylene, divinylemthylsilane,
hexamethyldisilane, and tetramethylsiloxane.
[0017] As used herein, "reactant" monomer refers to a branched or
unbranched hydrocarbon that can be plasma deposited on a substrate,
preferably at a relatively low temperature. The hydrocarbon can be
classified as an aliphatic monomer, a cyclic monomer, or it can
include a combination of aliphatic and cyclic groups (e.g., alkaryl
and aralkyl groups), wherein the hydrocarbon may include one or
more heteroatoms, such as nitrogen, oxygen, sulfur, silicon, etc.
In the context of the present invention, the term "aliphatic" means
a saturated or unsaturated linear or branched hydrocarbon. This
term is used to encompass alkyl, alkenyl, and alkynyl compounds,
for example. The term "alkyl" means a saturated linear or branched
hydrocarbon; including, for example, methane, ethane, isopropane,
t-butane, heptane, dodecane, and the like. The term "alkenyl" means
an unsaturated linear or branched hydrocarbon with one or more
carbon-carbon double bonds, such as a vinyl-containing compound.
The term "alkynyl" means an unsaturated linear or branched
hydrocarbon with one or more triple bonds. The term "cyclic" means
a closed ring hydrocarbon that is classified as an alicyclic,
aromatic, or heterocyclic compound. The term "alicyclic" means a
cyclic hydrocarbon having properties resembling those of aliphatic
hydrocarbons. The term "aromatic" or "arene" compound means a mono-
or polynuclear aromatic hydrocarbon.
[0018] A method in accordance with the present invention is
suitable for any implantable device but is particularly well suited
for micro eletromechanical devices, such as implantable pumps,
filters, valves, cardiac pacesetters, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic of an apparatus for use in a coating
method in accordance with the present invention.
DETAILED DESCRIPTION
[0020] Coating at least one surface of an implantable device that
provides a relatively corrosion-resistant coating on at least one
surface of the device preferably includes plasma deposition of a
reactant monomer, preferably a reactant monomer selected from the
group consisting a substituted or unsubstituted alkene, arene,
silane, siloxane, and a combination thereof. More preferably, the
reactant monomer is selected from the group consisting of ethylene,
xylene, 2-methyl 1-pentene, divinylmethylsilane,
hexamethyldisilane, tetramethyldisiloxane, and a combination
thereof.
[0021] Suitable plasma reactors are known in the art, examples of
which are described by Yasuda, H., Plasma Polymerization, Academic
Press (Orlando, Fla., 1985); and d'Agostino, R., Plasma Deposition,
Treatment, and Etching of Polymers, Academic Press (San Diego,
Calif., 1990). Typically, such plasma reactors use short wave
energy (RF or microwave) to excite plasma.
[0022] In general, a plasma reactor for use in the present
invention-can include a glass reaction chamber that is fitted with
a vacuum exhaust, gas inlets and at least one capacitively coupled
electrode. In addition, the reactor is fitted with a pressure
transducer and a mass flow controller for controlling and measuring
the amount of gas being introduced into the reactor. The theory and
practice of radio frequency (RF) gas discharge is explained in
detail in 1) "Gas-Discharge Techniques For Biomaterial
Modifications" by Gombatz and Hoffman, CRC Critical Reviews in
Biocompatibility. Vol. 4, Issue 1 (1987) pp 1-42; 2) "Surface
Modification and Evaluation of Some Commonly Used Catheter
Materials, I. Surface Properties" by Triolo and Andrade, Journal of
Biomedical Materials Research, Vol. 17, 129-147 (1983), and 3)
"Surface Modification and Evaluation of Some Commonly Used Catheter
Materials, II. Friction Characterized" also by Triolo and Andrade,
Journal of Biomedical Materials Research, Vol. 17, 149-165
(1983).
[0023] FIG. 1 illustrates in schematic form a plasma reactor 10
that can be employed in a method in accordance with the present
invention. The plasma reactor 10 includes, in general, a vertical
reaction chamber 12, R.F. power source 14 coupled across upper and
lower electrodes 16 and 18, vacuum pump 20 and a reactant monomer
source 22 in fluid communication with the reaction chamber 12.
Preferably, the reactant monomer source 22 also includes a means
for controlling the flow rate of the reactant monomer (not
shown).
[0024] A substrate having at least one surface 24 to be coated is
disposed on one electrode, for example, the lower electrode 18.
Optionally, the electrode 18 can be brought to a suitable
temperature by a heating/cooling unit (not shown) that may be
located in close proximity to electrode 18 and electrically
controlled by a temperature control unit (not shown). Preferably, a
plasma deposition method in accordance with the present invention
does not require the input of energy for heating or cooling, so
that the deposition takes place at a relatively low temperature,
more preferably ambient temperature (typically about 20EC to about
30EC). However, it will be recognized by those with ordinary skill
in the art that although plasma deposition takes place at a
relatively low temperature, the temperature of the surface so
coated may increase slightly, typically to a temperature just
slightly warmer than ambient temperature to the touch.
[0025] Optionally, a bellows (not shown) may be provided to adjust
the spacing between the electrodes and, hence, controlling the
confinement of the plasma 40. Preferably, a throttle valve 34 may
be provided to control the pressure in the reaction chamber 12. The
parameters that typically control the film characteristics formed
from the reactant monomer include gas composition, gas flow rate,
R.F. power, pressure, and temperature. Typically, the R.F. power
can range from about 30 Watts to about 100 Watts, but is preferably
at about 40 Watts for reactant monomer deposition. The pressure is
typically about 0.025 Torr to about 1.0 Torr. Preferably, a glow
discharge of the reactant monomer is created by using the R.F.
power above for a period of time of about 10 minutes or less, more
preferably, from about 15 seconds to about 5 minutes, and even more
preferably from about 1 minute to about 4 minutes.
[0026] Preferably, the reactant monomer is introduced into the
reaction chamber with an inert gas from source 38 that may be in
fluid communication with the reaction chamber 12. An inert gas can
be selected from the group of argon, helium, nitrogen, neon, and
the like. Preferably, the inert gas is argon. Combinations of the
inert gases can also be beneficial to make the initiation of
discharge (i.e., generation of the plasma) easier. For example,
argon can be added to neon in a minor amount that may improve
plasma initiation.
[0027] The reactant monomer is preferably provided to the reaction
chamber in a ratio with the inert gas of about 3 parts to about 6
parts, preferably about 3 parts to about 5 parts, reactant monomer
to about 1 part inert gas. For example, the reactant monomer gas
flow rate is preferably about 8 sccm to about 12 sccm, more
preferably about 9 sccm to about 10 sccm, and the inert gas flow
rate is preferably about 2 sccm. Of course, one skilled in the art
will readily appreciate that the deposition rate of the reactant
monomer depends on the gas composition and is directly proportional
to the gas flow rate, power, pressure, and is inversely
proportional to temperature so that one could empirically determine
the optimum parameters, such as those indicated above, for desired
film characteristics.
[0028] For example, in one embodiment, the operating pressure can
be about 0.1 Torr. The reactant monomer can be supplied at a rate
of about 10 sccm and an inert gas can be supplied at a rate of
about 2 sccm. A glow discharge can be created by supplying R.F.
power of about 40 Watts for a period of time of about 2 minutes.
Preferably, the reactant monomer is selected from the group
consisting of ethylene, 2-methyl-1-pentene, xylene,
divinylmethylsilane, hexamethyldisilane, tetramethyldisiloxane, and
a combination thereof. Preferably, the inert gas is argon.
[0029] A surface to be coated in accordance with the present
invention is plasma pretreated to further prepare the surface prior
to coating. For example, the surface can be pretreated in a plasma
reactor, such as described above. An inert gas, such argon, can be
supplied to the reaction chamber at a flow rate of about 2 sccm.
The operating pressure can be about 5 mTorr to about 15 mTorr. A
glow discharge can be created using an R.F. power of about 100
Watts for a time of about 2 minutes or less.
[0030] Preferably, prior to plasma depositing a reactant monomer on
a device surface, the surface to be coated is thoroughly cleaned to
remove any contaminating debris and the like. More preferably, the
surface to be coated in accordance with the present invention is
first cleaned and plasma pretreated prior to plasma depositing the
reactant monomer. Conventional techniques can be used to adequately
clean the surface, such as applying typical cleaning solvents
(e.g., isopropyl alcohol, acetone, and the like) and/or ultrasonic
cleaning in an aqueous solution, solvent cleaning, and the like.
For example, the device to be coated can be placed in a
conventional ultrasonic bath containing an aqueous detergent
solution for cleaning and then subsequently rinsed to remove
detergent prior to coating.
[0031] Although the foregoing was described with particular
attention to the corrosion-resistance of a coating formed in
accordance with the present invention, it is to be understood by
those skilled in the art that such a coating can also be utilized
in other applications. For example, a coating formed in accordance
with the present invention can be used as an adhesion promoting
primer to enhance adhesion of a second coating to the device, as a
barrier layer for electronic contacts and devices, and a
passivating layer.
[0032] For example, once a surface of a device has been coated as
described above, a polymer can now be applied to the coated surface
by conventional methods by dipping, spraying, or other application
techniques. Polymers particularly suitable include a natural
hydrogel, a synthetic hydrogel, silicone, polyurethane,
polysulfone, cellulose, polyethylene, polypropylene, polyamide,
polyimide, polyester, polytetrafluoroethylene (TEFLON), polyvinyl
chloride, epoxy, phenolic, neoprene, polyisoprene, and a
combination thereof. Additionally, a bio-active compound can be
adhered to a surface coated in accordance with the present
invention. The bio-active compound can be applied directly to the
surface that has been plasma treated, as described above, or the
surface that has been plasma treated and includes the polymer
adhered thereto. A suitable bio-active compound can be selected
from the group consisting of an antithrombotic agent, an
antiplatelet agent, an antimitotic agent, an antioxidant, an
antimetabolite agent, an anti-inflammatory agent, and a combination
thereof. For example, one preferred bio-active compound is heparin.
The subsequent addition of a polymer and/or a bio-active compound
can be accomplished utilizing conventional techniques known in the
art, such as described by Y. Ikada, "Surface Modification of
Polymers for Medial Applications," Biomaterials, Vol. 15:725-736
(1994); E. A. Kulik, et al., "Peroxide Generation and Decomposition
on Polymer Surface," J. of Polymer Science: Part A: Polymer
Chemistry, Vol. 33:323-330 (1995); and K. Allmr et al., J. of
Polymer Science, Vol. 28:173-183 (1990), for example.
[0033] An implantable device may be any implantable device. For
example, in the case where the implantable device is a pacemaker,
the implantable device may be a pacemaker such as that described in
U.S. Pat. No. 5,158,078 to Bennett, et al.; U.S. Pat. No. 5,312,453
to Shelton et al.; or U.S. Pat. No. 5,144,949 to Olson et al.
[0034] Implantable device may also be a
pacemaker-cardioverter-defibrillat- or (PCD) corresponding to any
of the various commercially-available implantable PCDs. For
example, the present invention may be practiced in conjunction with
PCDs such as those described in U.S. Pat. No. 5,545,186 to Olson,
et al.; U.S. Pat. No. 5,354,316 to Keimel; U.S. Pat. No. 5,314,430
to Bardy; U.S. Pat. No. 5,131,388 to Pless; or U.S. Pat. No.
4,821,723 to Baker, et al.
[0035] Alternatively, an implantable device may be an implantable
neurostimulator or muscle stimulator such as that disclosed in U.S.
Pat. No. 5,199,428 to Obel, et al.; U.S. Pat. No. 5,207,218 to
Carpentier, et al.; or U.S. Pat. No. 5,330,507 to Schwartz, or an
implantable monitoring device such as that disclosed in U.S. Pat.
No. 5,331,966 to Bennett, et al.
[0036] Additionally, the implantable device may be micromachined
devices such as implantable fluid handling devices for continuous
administration of therapeutic agents including those for pain
management, cancer chemotherapy, treatment of intractable
spasticity, to name a few. Such devices are described in, for
example, U.S. Pat. Nos. 5,705,070; 5,702,618; and 5,660,728 all to
Saaski et al.
[0037] Further, for example, an implanted device may be a
defibrillator, a cardioverter/defibrillator, a brain stimulator, a
gastric stimulator, a drug pump, a hemodynamic monitoring device,
or any other implantable device that would benefit from a coating
for protection against corrosion. Therefore, the present invention
is believed to find wide application in any form of implantable
device. As such, the description herein making reference to any
particular medical device is not to be taken as a limitation of the
type of medical device that can be protected from corrosion as
described herein.
[0038] In accordance with the present invention, at least one
surface of an implantable device can be coated as described above.
The at least one surface can be formed from a material selected
from the group consisting of a metal (including alloys), a
nonmetal, and a combination thereof. "Metal" refers to a group of
compounds that tend to form positive ions when the compounds are in
solution and include alkali metals, alkaline earth metals,
transition metals, noble metals, rare metals, rare earth metals, to
name a few. "Nonmetal" refers to a group of compounds that, in
general, have very low to moderate conductivity and relatively high
electronegativity and include germanium-, selenium-, and
silicon-containing compounds, to name a few. Metals and nonmetals
are both intended to include oxides and nitrides, and combinations
thereof. For example, suitable materials that can be plasma treated
in accordance with the present invention include gold, stainless
steel, silicon, to name a few. The at least one surface may be
located on the exterior surface, interior surface, or both, of an
implantable device.
EXAMPLES
[0039] While surface modification methods and apparatuses in
accordance with the invention have been described herein, the
following non-limiting examples will further illustrate the
invention.
[0040] In each of the following examples, silicon wafers having a
size of about 1 cm.sup.2 were coated as described below. Prior to
plasma coating a reactant monomer on the surface of the wafer, each
wafer was thoroughly cleaned. First, the wafers were cleaned by
placing the wafers into a beaker containing acetone and soaked for
10 minutes at room temperature. The wafers were then removed from
the acetone and placed in isopropyl alcohol and soaked for 10
minutes at room temperature. A beaker was filled with a cleaning
solution of 30 parts DI water to 1 part cleaning solution
commercially available under the trade designation of ULTRAMET,
from Buehler, Lake Bluff, Ill. Water was then placed in a
conventional ultrasonic cleaner commercially available under the
trade designation of ULTRASONIC CLEANER, from Branson Cleaning
Equipment Co., Shelton, Conn., to a depth of at least 1/4 the
height of the beaker. The wafers were placed in the cleaning
solution in the beaker. The beaker containing the wafers in the
cleaning solution were placed into the ultrasonic cleaner. The
ultrasonic cleaner was set for a cleaning time of 3 minutes.
[0041] The wafers were then removed from the cleaning solution and
placed on a drying rack. The wafers were rinsed thoroughly with DI
water by rinsing 5 times with 2 quarts of DI water at ambient
conditions. The wafers were then removed and placed on rice paper
to dry for at least one half hour at ambient conditions.
[0042] Plasma pretreatment was applied directly to a cleaned
silicon wafer surface. The wafer was placed in a plasma reaction
chamber as described above and shown in FIG. 1. The wafers were
placed on the lower electrode. The reaction chamber was evacuated
to an initial pressure of less than about 5 mTorr. The operating
pressure for plasma pretreatment was set at 11 mTorr and the
reaction chamber was allowed to equilibrate for 15 minutes. Mass
flow controllers were used to meter the argon gas into the reaction
chamber at the rate of 2 sccm. A glow discharge was created by
putting a 100 Watt RF power load on the electrodes for 1 minute
exposure time.
[0043] All wafers, whether pretreated or not, were coated using a
plasma reactor as described above and the parameters for reactant
monomer deposition are recited for each example below.
Example 1
[0044] A silicon wafer that was not cleaned and pretreated as
described above was placed in the plasma reaction chamber. The
wafer was placed on the lower electrode. The reaction chamber was
evacuated to a base pressure of 5 mTorr. The operating pressure was
set 0.1 Torr and the reaction chamber was allowed to equilibrate
for 15 minutes. Mass flow controllers were used to meter the
ethylene flow at a rate of 15 sccm and the argon gas into the
reaction chamber at the rate of 2 sccm. A glow discharge was
created by putting a 100 Watt RF power load on the electrodes for 1
minute exposure time.
[0045] Under these conditions, a blue coating was visually observed
on the wafer. The durability of the coated was evaluated by wiping
the coated wafer surface with a laboratory tissue commercially
available under the trade designation KIMWIPE (Kimberly Clark
Corporation, Roswell, Ga.) with isopropyl alcohol. The coated
surface scratched easily under these conditions.
Example 2
[0046] A cleaned and plasma pretreated silicon wafer, as described
above, was placed in the plasma reaction chamber and plasma coated
using the same conditions as described in Example 1.
[0047] Under these conditions, a blue coating was visually observed
on the wafer. The durability of the coated was evaluated by wiping
the coated wafer surface with a laboratory tissue commercially
available under the trade designation KIMWIPE with isopropyl
alcohol. The coated surface did not scratch under these conditions.
To further evaluate durability, the coated wafer was cut in half,
where a first half was placed in a 1N aqueous solution of sodium
hydroxide and the second half was placed in a 1N aqueous solution
of hydrochloric acid. Each half was soaked in the respective
solution for 40 hours at room temperature. The coating on the first
half of the wafer was observed with the naked eye as having many
"pore-like" openings. The coating on the second half of the wafer
lifted off the wafer surface after soaking in the hydrochloric acid
solution.
Example 3
[0048] A cleaned and plasma pretreated silicon wafer was plasma
coated with 2-methyl-1-pentene. After plasma pretreating the wafer
for 1 minute, the RF power remained at 100 Watts and the operating
pressure was increased to 0.1 Torr and the reaction chamber was
allowed to equilibrate for 15 minutes. Thereafter, the RF power was
decreased to 40 Watts. Mass flow controllers were used to meter the
2-methyl-1-pentene flow at a rate of 10 sccm and the argon gas into
the reaction chamber at the rate of 2 sccm. A glow discharge was
created by putting the 40 Watt RF power load on the electrodes for
2 minutes exposure time. A coating was produced on the wafer
surface that had a thickness of 750.DELTA..
[0049] Under these conditions, a smooth blue coating was visually
observed on the wafer. Using a conventional dissecting microscope
at a magnification of 10.times., holes in the coating could not be
detected. The durability of the coated was evaluated by wiping the
coated wafer surface with a laboratory tissue commercially
available under the trade designation KIMWIPE with isopropyl
alcohol. The coated surface did not scratch under these conditions.
To further evaluate durability, the coated wafer was placed in a 1N
aqueous solution of sodium hydroxide for 16 hours at room
temperature. The coating on the wafer was observed under 10.times.
magnification as having many "pore-like" openings.
Example 4
[0050] A cleaned and pretreated silicon wafer was coated with
2-methyl-1-pentene as described in Example 3 with the only
exception being that the glow discharge was created by putting the
40 Watt RF power load on the electrodes for 4 minutes exposure
time. A coating was produced on the wafer surface that had a
thickness of 575.DELTA..
Example 5
[0051] A gold wafer was coated with 2-methyl-1-pentene as described
in Example 3, except as follows. The gold wafer was placed in a
plasma reaction chamber as described above and shown in FIG. 1. The
wafers were placed on the lower electrode. The reaction chamber was
evacuated to a base pressure of 5 mTorr. The operating pressure was
set 0.03 Torr and the reaction chamber was allowed to equilibrate
for 15 minutes. Mass flow controllers were used to meter the argon
gas into the reaction chamber at the rate of 2 sccm. A glow
discharge was created by putting a 100 Watt RF power load on the
electrodes for 30 seconds exposure time.
[0052] After plasma pretreating the wafer for 30 seconds, the RF
power remained at 100 Watts and the 2-methyl-1-pentent was added to
the reaction chamber that was allowed to equilibrate for 5 minutes.
Thereafter, the RF power was decreased to 40 Watts. Mass flow
controllers were used to meter the 2-methyl-1-pentene flow at a
rate of 9.6 sccm and the argon gas into the reaction chamber at the
rate of 2 sccm. A glow discharge was created by putting the 40 Watt
RF power load on the electrodes for 10 minutes exposure time. A
coating was produced on the wafer surface that had a thickness of
1640.DELTA..
Example 6
[0053] A cleaned and plasma pretreated silicon wafer was plasma
coated with 2-methyl-1-pentene. After plasma pretreating the wafer
for 1 minute, the RF power remained at 100 Watts and the operating
pressure was increased to 0.1 Torr and the reaction chamber was
allowed to equilibrate for 15 minutes. Thereafter, the RF power was
decreased to 40 Watts. Mass flow controllers were used to meter the
2-methyl-1-pentene flow at a rate of 10 sccm and the argon gas into
the reaction chamber at the rate of 2 sccm. A glow discharge was
created by putting the 40 Watt RF power load on the electrodes for
2 minutes exposure time. A coating was produced on the wafer
surface that had a thickness of 750.DELTA..
[0054] Under these conditions, a smooth blue coating was visually
observed on the wafer. Using a conventional dissecting microscope
at a magnification of 10.times., holes in the coating could not be
detected. The durability of the coated was evaluated by wiping the
coated wafer surface with a laboratory tissue commercially
available under the trade designation KIMWIPE with isopropyl
alcohol. The coated surface did not scratch under these conditions.
To further evaluate durability, the coated wafer was placed in a 1N
aqueous solution of sodium hydroxide for 16 hours at room
temperature. The coating on the wafer was observed under 10.times.
magnification as having many "pore-like" openings.
Example 7
[0055] A cleaned and plasma pretreated silicon wafer was plasma
coated with tetramethyldisiloxane (TMDSO) under the same conditions
as described in Example 6. A coating was produced on the wafer
surface that had a thickness of 750.DELTA..
[0056] Under these conditions, a smooth blue coating was visually
observed on the wafer. Using a conventional dissecting microscope
at a magnification of 10.times., holes in the coating could not be
detected. The durability of the coated was evaluated by wiping the
coated wafer surface with a laboratory tissue commercially
available under the trade designation KIM WIPE with isopropyl
alcohol. The coated surface did not scratch under these conditions.
To further evaluate durability, the coated wafer was placed in a 1N
aqueous solution of sodium hydroxide for 16 hours at room
temperature. The coating on the wafer was observed under 10.times.
magnification as having many "pore-like" openings.
Example 8
[0057] A cleaned and plasma pretreated silicon wafer was plasma
coated with divinylmethylsilane under the conditions described in
Example 6. A coating was produced on the wafer surface that had a
thickness of 750.DELTA..
[0058] Under these conditions, a smooth blue coating was visually
observed on the wafer. Using a conventional dissecting microscope
at a magnification of 10.times., holes in the coating could not be
detected. The durability of the coating was evaluated by wiping the
coated wafer surface with a laboratory tissue commercially
available under the trade designation KIMWIPE with isopropyl
alcohol. The coated surface did not scratch under these conditions.
To further evaluate durability, the coated wafer was placed in a 1N
aqueous solution of sodium hydroxide for 16 hours at room
temperature. The coating on the wafer was observed under 10.times.
magnification as having many "pore-like" openings.
[0059] The complete disclosures of all patents, patent
applications, and publications are incorporated herein by reference
as if individually incorporated. The above disclosure is intended
to be illustrative and not exhaustive. The description will suggest
many variations and alternatives to one of ordinary skill in this
art. All these alternatives and variations are intended to be
included within the scope of the attached claims. Those familiar
with the art may recognize other equivalents to the specific
embodiments described herein which equivalents are also intended to
be encompassed by the claims attached thereto.
* * * * *