U.S. patent application number 09/071371 was filed with the patent office on 2001-05-31 for method and apparatus for providing a conductive, amorphous non-stick coating.
Invention is credited to KHANWILKAR, PRATAP, KUMAR, B. AJIT, OLSEN, DON B..
Application Number | 20010002000 09/071371 |
Document ID | / |
Family ID | 22100886 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002000 |
Kind Code |
A1 |
KUMAR, B. AJIT ; et
al. |
May 31, 2001 |
METHOD AND APPARATUS FOR PROVIDING A CONDUCTIVE, AMORPHOUS
NON-STICK COATING
Abstract
A conductive, non-stick coating is provided using a ceramic
material which is conductive, flexible and provides a surface which
exhibits the property of lubricity. A room or near room temperature
manufacturing process produces a coating of titanium nitride on a
substrate, where the coating is amorphous if the substrate is a
solid material including plastics, composites, metals, magnets, and
ceramics, enabling the substrate to bend without damaging the
coating. The coating can also be applied as a conformal coating on
a variety of substrate shapes, depending upon the application. The
coating is bio-compatible and can be applied to a variety of
medical devices.
Inventors: |
KUMAR, B. AJIT; (SALT LAKE
CITY, UT) ; KHANWILKAR, PRATAP; (SALT LAKE CITY,
UT) ; OLSEN, DON B.; (SALT LAKE CITY, UT) |
Correspondence
Address: |
DAVID W O'BRYANT
MORRISS, BATEMAN, O'BRYANT & COMPAGNI
5882 SOUTH 900 EAST,
SUITE 300
SALT LAKE CITY
UT
84121
US
|
Family ID: |
22100886 |
Appl. No.: |
09/071371 |
Filed: |
April 30, 1998 |
Current U.S.
Class: |
204/192.1 ;
427/126.1; 427/127 |
Current CPC
Class: |
A61B 2018/00077
20130101; C23C 14/0641 20130101; A61M 60/122 20210101; A61B
2018/00119 20130101; A61B 18/14 20130101; A61B 2018/00148 20130101;
A61B 2017/0088 20130101; A61B 2018/00107 20130101; A61M 60/00
20210101; A61M 60/871 20210101; A61M 60/268 20210101 |
Class at
Publication: |
204/192.1 ;
427/126.1; 427/127 |
International
Class: |
C23C 014/00; B05D
005/12; B05D 005/06; B05D 005/08 |
Claims
What is claimed is:
1. A method for providing a wear-resistant ceramic coating on a
substrate material which is used in an abrasive environment, such
that the substrate material is not deformed during a process of
applying the wear-resistant ceramic coating, said method comprising
the steps of: (1) selecting the ceramic coating from the group of
ceramics consisting of transition metal nitrides which are both
amorphous and conductive; and (2) using a generally room
temperature application process to apply the wear-resistant ceramic
coating to the substrate material such that the substrate material
is not deformed.
2. The method as defined in claim 1 wherein the method further
comprises the step of applying a wear-resistant ceramic coating
which is amorphous.
3. The method as defined in claim 1 wherein the method further
comprises the step of applying at least two ceramic materials which
are transition metal nitrides.
4. The method as defined in claim 1 wherein the method further
comprises the step of applying (i) at least one ceramic to the
substrate material which is a transition metal nitride, and (ii) at
least one material which is not a transition metal nitride.
5. The method as defined in claim 1 wherein the method further
comprises the step of applying a wear-resistant ceramic coating
which is conductive to thereby facilitate propagation of electrical
energy along the substrate material.
6. The method as defined in claim 1 wherein the method further
comprises the step of applying a wear-resistant ceramic coating
which is not worn away by application of RF energy thereto, by
abrasion or by repeated sterilization thereof.
7. The method as defined in claim 1 wherein the method further
comprises the step of deforming the substrate material from a
resting state, and wherein the wear-resistant ceramic coating is
flexible so as to be deformed with the substrate material without
damage to the wear-resistant ceramic coating.
8. The method as defined in claim 1 wherein the method further
comprises the step of depositing the wear-resistant ceramic coating
on the substrate material using a room or near room temperature
sputtering process.
9. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a continuous coating over the substrate material.
10. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a corrosion resistant coating over the substrate material.
11. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a fatigue resistant coating over the substrate material.
12. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a sterilizable and biocompatible coating over the substrate
material.
13. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a radio frequency opaque coating over the substrate
material.
14. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a conformal coating over the substrate material.
15. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a generally smooth and non-stick coating over the substrate
material.
16. The method as defined in claim 1 wherein the method further
comprises the step of depositing the wear-resistant ceramic coating
using room or near room temperature sputtering.
17. The method of manufacturing as defined in claim 16 wherein the
method comprises the further step of sputtering titanium nitride
onto the substrate material.
18. The method as defined in claim 1 wherein the method further
comprises the step of selecting the substrate material for the
substrate materials consisting of plastics, glass, ceramics,
metals, composites, magnetic materials and semiconductors.
19. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as shielding against electro magnetic interference.
20. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as shielding against radio frequency interference.
21. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a chemically inert, non-reactive and stable coating.
22. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
as a diffusion barrier, wherein the diffusion barrier reduces a
passing of fluids and gases therethrough.
23. The method as defined in claim 22 wherein the method further
comprises the step of selecting as the diffusion barrier a
bio-compatible coating which is amorphous, to thereby enable the
diffusion barrier to flex without damaging the bio-compatible
coating.
24. The method as defined in claim 22 wherein the method further
comprises the step of terminating any exchange of gases or fluids
through the diffusion barrier, thereby eliminating any exchange of
gases or fluids.
25. The method as defined in claim 22 wherein the method further
comprises the step of forming the diffusion barrier on an otherwise
permeable membrane which otherwise enables an exchange of fluids
and gases therethrough.
26. The method as defined in claim 1 wherein the method further
comprises the step of applying an adherent ceramic coating which
readily couples to the substrate material.
27. The method as defined in claim 1 wherein the method further
comprises the steps of: (1) providing a plurality of different
substrate materials in a single assembly; and (2) applying the
ceramic coating to the plurality of different substrate materials
of the single assembly such that the ceramic coating is applied to
all surfaces thereof.
28. The method as defined in claim 18 wherein the magnetic
materials are selected from the group of magnetic materials
consisting of magnetic tape, ceramic magnets, rare-earth magnets,
and metallic magnets, wherein the magnetic materials are thereby
protected from moisture which can damage the magnetic
materials.
29. The method as defined in claim 1 wherein the method further
comprises the step of applying the wear-resistant ceramic coating
to components of a storage unit for a computer, wherein the storage
unit includes a magnetic media which is caused to rotate, said
wear-resistant ceramic coating reducing friction of movable
components thereof.
30. The method as defined in claim 29 wherein the method further
comprises the step of at least partially coating the storage unit
with the ceramic coating to thereby provide protection from EMI and
RFI.
31. A method for providing a wear-resistant ceramic coating on a
semiconductor material which is used as part of an integrated
circuit, such that the semiconductor material achieves increased
conductivity and reduces diffusion of components thereof, said
method comprising the steps of: (1) selecting the ceramic coating
from the group of ceramics consisting of transition metal nitrides
which are both amorphous and conductive; and (2) using a generally
room temperature application process to apply the ceramic coating
to the semiconductor material such that the semiconductor material
is more conductive and so that there is reduced diffusion between
elements of the semiconductor material.
32. A method for providing a wear-resistant ceramic coating on a
magnetic material which can be damaged by application of thermal
energy, such that the magnetic material retains its magnetic
properties during a process of applying the wear-resistant ceramic
coating, said method comprising the steps of: (1) selecting the
ceramic coating from the group of ceramics consisting of transition
metal nitrides which are both amorphous and conductive; and (2)
using a generally room temperature application process to apply the
wear-resistant ceramic coating to the magnetic material such that
the magnetic material is not deformed.
33. A method for providing a wear-resistant ceramic coating on a
heat-sensitive material which is used in an abrasive environment,
such that the heat-sensitive material is not deformed during a
process of applying the wear-resistant ceramic coating, said method
comprising the steps of: (1) selecting the ceramic coating from the
group of ceramics consisting of transition metal nitrides which are
both amorphous and conductive; and (2) using a generally room
temperature application process to apply the wear-resistant ceramic
coating to the heat-sensitive material such that the heat-sensitive
material is not deformed.
33. A method for providing a wear-resistant ceramic coating on a
material which is used in an environment which is detrimental to
the material, such that the material is covered with a continuous,
smooth and fatigue resistant ceramic coating after an application
process thereof, said method comprising the steps of: (1) selecting
the ceramic coating from the group of ceramics consisting of
transition metal nitrides which are both amorphous and conductive;
and (2) using a generally room temperature application process to
apply the wear-resistant ceramic coating to the material such that
to thereby enhance properties of wear resistance, lubricity and
strength.
34. The method as defined in claim 33 wherein the material is
selected from the group of products including kitchen utensils,
gears, spark plugs, molds, plumbing fixtures, eyeglass frames,
cutting instruments, moisture barriers, sporting goods, writing
instruments, drilling instruments, fasteners, bearings, bushings,
electrical devices, semiconductors, jewelry, engine components,
toys, packaging, optical instruments, fuel cells, and recording
media.
35. A method for providing a wear-resistant ceramic coating on a
ceramic material which can be damaged by application of thermal
energy, such that the ceramic material retains its properties
during a process of applying the wear-resistant ceramic coating,
said method comprising the steps of: (1) selecting the ceramic
coating from the group of ceramics consisting of transition metal
nitrides which are both amorphous and conductive; and (2) using a
generally room temperature application process to apply the
wear-resistant ceramic coating to the ceramic material such that
the ceramic material is not deformed.
36. An audio system including a playback head for use in reading
data from an analog media which is disposed in contact with the
audio playback head and moved thereover during playback, said audio
playback head comprising: the audio playback head which is capable
of generating electrical signals in response to the analog media
being moved thereover, said electrical signals being indicative of
acoustical signals recorded on the analog media; a wear-resistant
ceramic coating disposed on the audio playback head to thereby
increase resistance to wear thereof and to thereby extend a usable
life of the audio playback head.
37. The audio playback head as defined in claim 36 wherein the
audio playback head is capable of recording analog signals to the
analog medium.
38. The audio playback head as defined in claim 36 wherein the
audio playback head is capable of playback of video data stored as
analog data on the analog medium.
39. A container for use in cooking wherein the cooking container is
exposed to heat to thereby heat the cooking container and food
contents therein, said cooking container comprising: an outer
surface; an inner surface on which the food contents are disposed
to thereby enable transfer of heat from the inner surface to the
food contents; and a wear-resistant and non-stick ceramic coating
disposed on the inner surface to thereby enable metal utensils to
be used in movement of the food contents without damaging the inner
surface of the cooking container.
40. A plastic gear for use in applications where weight is
relevant, said plastic gear comprising: a generally circular disk
having a plurality of splines on an outer edge thereof, wherein the
plurality of splines are designed so as to mesh with splines of
another device to thereby transmit or receive force thereby; a
wear-resistant ceramic coating disposed on the plurality of splines
to thereby provide enhance wear-resistance, maintain dimensional
accuracy, and improve a useful lifespan thereof.
41. A razor blade for use in shaving, wherein said blade is
relatively longer lasting because it is coated with a
wear-resistant ceramic coating having improved lubricity, said
razor blade comprising: a substrate having at least one cutting
edge, wherein the substrate is designed for being pulled across
skin to thereby remove hair from the skin; and a continuous ceramic
coating disposed on the substrate to thereby cover the at least one
cutting edge with an amorphous coating which resists wear caused by
cutting hair, and which can flex with the substrate without
damaging the continuity of the continuous ceramic coating.
42. A spark plug for use in generating an electrical spark for
igniting a mixture of fuel and air in an internal-combustion
engine, said spark plug comprising: a first electrode for carrying
an electrical charge from a power source; a second electrode for
receiving the electrical charge from the power source; an
electrically conductive, non-stick ceramic coating disposed on the
first and the second electrodes to thereby increase conductivity
and provide a surface which is resistant to a build-up of materials
which can interfere with generation of the electrical spark.
43. A method for providing a wear-resistant ceramic coating on a
ceramic material which can be damaged by application of thermal
energy, such that the ceramic material retains its properties
during a process of applying the wear-resistant ceramic coating,
said method comprising the steps of: (1) selecting the ceramic
coating from the group of ceramics consisting of transition metal
nitrides which are both amorphous and conductive; and (2) using a
generally room temperature application process to apply the
wear-resistant ceramic coating to the ceramic material such that
the ceramic material is not deformed and altered in its physical
properties.
44. A method for providing a bio-compatible coating on a
temperature-sensitive material which is used in a medical device,
such that the temperature sensitive material is not damaged during
a process of applying the bio-compatible coating, said method
comprising the steps of: (1) selecting the bio-compatible coating
from the group of ceramics consisting of transition metal nitrides
which are both amorphous and conductive; (2) using a generally room
temperature application process to apply the bio-compatible ceramic
coating to the temperature-sensitive material such that the
temperature-sensitive material is not damaged by thermal energy
from the application process; and (3) disposing the
temperature-sensitive material with its bio-compatible coating in
the medical device, to thereby enable the medical device to be
utilized in a medical environment.
45. The method as defined in claim 44 wherein the method further
comprises the step of selecting the temperature-sensitive material
from the group of temperature-sensitive materials including
plastic, glass, and magnetic materials.
46. The method as defined in claim 44 wherein the method further
comprises the step of selecting the bio-compatible coating from the
group of ceramics which provide corrosion resistance.
47. The method as defined in claim 46 wherein the method further
comprises the step of selecting the bio-compatible coating from the
group of ceramics which provide a surface texture of lubricity.
48. The method as defined in claim 47 wherein the
temperature-sensitive material is a plastic introducer catheter
which is able to be more easily inserted because of the plastic
introducer's lubricity.
49. The method as defined in claim 44 wherein the method further
comprises the step of applying the bio-compatible coating to a
plurality of permanent magnets which are used in an implantable
medical device requiring an electric motor, magnetic bearing,
sensor and other electromagnetic devices for operation.
50. A method for utilizing nonbio-compatible materials in an
implantable medical device, wherein the implantable medical device
is made safe for implantation, said method comprising the steps of:
(1) selecting a bio-compatible coating from the group of ceramics
consisting of transition metal nitrides which are both amorphous
and conductive; (2) using a generally room temperature application
process to apply the bio-compatible ceramic coating to the
nonbio-compatible materials such that the nonbio-compatible
materials are covered completely by the bio-compatible ceramic
coating; and (3) implanting the nonbio-compatible material which is
coated with the bio-compatible coating.
51. The method as defined in claim 50 wherein the method further
comprises the step of using less expensive nonbio-compatible
materials to thereby reduce costs of the implantable devices.
52. The method as defined in claim 51 wherein the method further
comprises the step of utilizing temperature-sensitive materials for
the nonbio-compatible materials, wherein the temperature-sensitive
materials are selected from the group of temperature-sensitive
materials consisting of plastics, glass, and magnetic
materials.
53. The method as defined in claim 52 wherein the method further
comprises the step of selecting the implantable devices from the
group of implantable devices consisting of stents, ventricular
assist devices, pumps, impellers, balloons, diaphragms, volume
displacement chambers, plastic tubes providing fluid paths,
bearings, bearing components, catheters, occluders, soft-tissue
implants, valves, shunts, pacemakers, defibrillators,
cardioverters, electrodes, neural stimulators, filters, grafts,
patches, contraceptive devices, sensors, transducers, needles,
medical tubes, clips, surgical staples, prostheses and
electrosurgical blades.
54. A method for creating a more effective diffusion barrier for a
medical device, wherein the diffusion barrier is disposed on a
permeable membrane through which fluids and gases are able to pass,
said method comprising the steps of: (1) selecting a bio-compatible
coating for the diffusion barrier; and (2) applying the
bio-compatible coating to the diffusion barrier using a generally
room temperature application process to thereby avoid damaging the
permeable membrane, wherein the bio-compatible coating reduces
penetration of the fluids and gases therethrough.
55. The method as defined in claim 54 wherein the method further
comprises the step of selecting a bio-compatible coating which is
amorphous to thereby enable the diffusion barrier to flex without
damaging the bio-compatible coating.
56. The method as defined in claim 55 wherein the method further
comprises the step of reducing an exchange of working fluids and
body fluids.
57. The method as defined in claim 56 wherein the method further
comprises the step of reducing the exchange of working fluids which
are selected from the group of working fluids including silicone
oil, other lubricants and air.
58. A diffusion barrier for use in an implantable medical device
which is exposed to body fluids, wherein the diffusion barrier
reduces passage of working fluids between the implantable medical
device and the body fluids, said diffusion barrier comprising: a
first membrane which is disposed between the body fluids and the
working fluids; an amorphous, bio-compatible, ceramic coating which
is applied on a first side through a room or near room temperature
process to a first side of the first membrane, wherein the
amorphous, bio-compatible, ceramic coating is integrally bonded to
the first membrane; and a second membrane which is bonded to a
second side of the amorphous, bio-compatible, ceramic coating.
59. The diffusion barrier as defined in claim 58 wherein the first
membrane and the second membrane are comprised of a polymer.
60. The diffusion barrier as defined in claim 59 wherein the
polymer is comprised of polyurethane.
61. The diffusion barrier as defined in claim 58 wherein the
amorphous, bio-compatible, ceramic coating is selected from the
group of ceramics consisting of transition metal nitrides which are
both amorphous and conductive, and which are also
fatigue-resistant, corrosion-resistant, and abrasion-resistant.
62. The diffusion barrier as defined in claim 58 wherein the
working fluids are also comprised of working gases.
63. A method for preventing diffusion of fluids between an
implantable medical device which is exposed to body fluids, and
working fluids of the implantable medical device, said method
comprising the steps of: (1) providing a first membrane which is
disposed between the body fluids and the working fluids; (2)
disposing an amorphous, bio-compatible, ceramic coating on a first
side thereof to a first side of the first membrane through a room
or near room temperature process, wherein the amorphous,
bio-compatible, ceramic coating is integrally bonded to the first
membrane; and (3) disposing a second membrane to a second side of
the amorphous, bio-compatible, ceramic coating, wherein said
ceramic coating reduces diffusion of the body fluids and the
working fluids through the first membrane and the second
membrane.
64. A method for preventing diffusion of fluids between an
implantable medical device which is exposed to body fluids, and
working fluids of the implantable medical device, said method
comprising the steps of: (1) providing a first membrane which is
disposed between the body fluids and the working fluids; and (2)
disposing an amorphous, bio-compatible, ceramic coating on a first
side thereof to a first side of the first membrane through a room
or near room temperature process, wherein the amorphous,
bio-compatible, ceramic coating is integrally bonded to the first
membrane, wherein said ceramic coating reduces diffusion of the
body fluids and the working fluids through the first membrane.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention pertains to a method for providing a
conductive, non-stick coating at or near room-temperature to many
materials which can benefit therefrom. More specifically, the
present invention pertains to a method and apparatus for applying
the conductive, non-stick coating to different materials, as well
as presenting various embodiments which can take advantage of the
coating's properties including bio-compatibility, flexibility,
radio-opacity, diffusion resistance, wear and corrosion resistance,
hardness, ability to be hydrophobic or hydrophilic, adherence to
multiple materials, sterilizability, and chemical inertness and
stability.
[0003] 2. State of the Art
[0004] The present invention was originally developed as a result
to improve electrosurgical instruments used in cauterization and
other medical procedures, as well as to provide a bio-compatible
coating for long-term implantable blood pumps. For example, prior
U.S. patents have been issued for various electrosurgical blades
which apply a non-stick coating to a cutting edge thereof. These
blades typically suffered from small openings in the non-stick
coating which were sometimes intentionally allowed to form in order
to ensure electrical conductivity along the cutting edge. Exposing
the metallic surface of the blade disadvantageously resulted in
charred tissue sticking to these areas. The result was that the
blade quickly became non-conductive and consequently unusable.
[0005] In an attempt to improve the blade, Blanch was granted U.S.
Pat. No. 4,785,807 (the '807 patent) for teaching an
electrosurgical blade which has a cutting edge of the blade which
is abraded or etched, and a coat of a non-stick fluorinated
hydrocarbon material which is applied over the etched cutting edge.
A coating of non-stick material covers the surface area of the
cutting blade and is intended to eliminate or reduce the clinging
of charred tissue to the blade. By eliminating the small openings
in the non-stick coating of previous blades, the blade better
inhibited the build up of charred tissue. However, one drawback in
the principle of the '807 patent is that the non-stick coating is
not particularly durable, and will wear off after repeated usage.
This is true partly because the non-stick and non-conductive
coating has the properties of an insulator and had to be kept thin
in order to enable the radio-frequency energy to pass through the
non-stick coating to the tissue to cut and/or cauterize.
[0006] Another drawback of the blade described in the '807 patent
is that the non-stick coating is not flexible. This inability to
bend the electrosurgical blade seriously limits the options of the
surgeon in the surgical procedures in which the blade can be used.
Furthermore, bending the electrosurgical blade causes the non-stick
coating to fracture. The electrosurgical blade then begins to
rapidly build up charred tissue because of exposed etched metal of
the blade, and any advantages of the non-stick coating are
lost.
[0007] The non-stick coating of the '807 patent is also
specifically described as Teflon (TM). The nature of Teflon (TM) is
such that it requires a high current to be used in cutting and
cauterization. This is because electrical current must pass through
the Teflon (TM) to the tissue. However, this constant passage of
current eventually breaks down the Teflon (TM), leaving small holes
or other imperfections in the Teflon (TM) coating. Charred tissue
then begins to adhere to the exposed metal beneath the Teflon (TM)
coating. Furthermore, electrical current will no longer be uniform
across the blade because the current will tend to concentrate at
locations where the metal is exposed.
[0008] Another problem in the state of the art electrosurgical
blades which utilize Teflon (TM) is that when heated, Teflon
disadvantageously breaks down and evolves fluorine as a gas. This
gas is hazardous to the patient and the surgical team.
[0009] The information above introduces some of the problems of
other non-stick coatings. However, the problems are associated
specifically with the issues which are involved when using the
non-stick coating for electrosurgical instruments. There are
actually numerous other embodiments of the present invention which
are able to take advantage of the characteristics of the
conductive, non-stick coating which was originally developed to
solve problems relating to electrosurgical instruments, blood
pumps, and other medical devices.
[0010] There are also other problems with state of the art medical
devices which are made from materials which do not react well or
ideally with body tissue. For example, stents can cause infection
and thrombosis, and have lubricity problems. Stents also clot up
after some period of time, and the body can form scar tissue around
the stent. A bio-compatible coating having greater lubricity and
which is flexible enough to expand with the stent when deployed.
Stents also tend to stick to the catheter that is used to insert
them.
[0011] Catheters also have lubricity problems. They can be
difficult to insert, especially when they are long. They are also
hard to extract because they can become stuck. Present coatings
that are used on catheters usually do not remain on the catheter,
and either have the property of bio-compatibility or lubricity, but
not both. Nonbio-compatible coatings are usually inflexible and
cannot be applied to flexing plastics such as catheters. Friction
during insertion also removes biological and polymeric coatings,
and they also wash off when exposed to flowing fluids, such as
blood. The tip of the catheter and the insertions site also tend to
be the site of blood clots. These problems are exacerbated for
balloon catheters in which the balloon sticks to the tissue or
tears, releasing potentially dangerous gases into the body.
[0012] It is also of interest to recognize that most catheters use
a radio-opaque metal band to denote the catheter position using
X-ray imaging. This band disadvantageously causes crimping of the
catheter. The metal band is also known to slip along the length of
the catheter, thereby causing false readings of the catheter
position in the body. The metal band providing radio-opacity is
also typically large. This can result in insertion and extraction
problems for the catheter. The metal band can also irritate and
damage the inner surface of the vessel through which the catheter
is inserted.
[0013] Guide wires used to install catheters also have problems of
lubricity because they provide a frictional surface which resists
entry into and passage through tissue.
[0014] The installation of a shunt is a painful process because of
the friction of the tissue. Furthermore, state of the art shunts
are also limited in their useful lifespan because they tend to have
bio-compatibility problems.
[0015] Needles such as those used in dialysis and for diabetics
which are of large diameter can also cause substantial pain during
insertion and cause significant tissue damage.
[0016] Silicone-based medical devices such as inhaler seals,
laryngechtomy prostheses, and nasal tampons have several major
problems. The solid silicone is sticky and rubbery, and thus these
devices are hard to insert and withdraw due to lubricity problems.
Some of these devices are also subject to infection and
thrombosis.
[0017] Trocars are also medical devices which would benefit from a
bio-compatible coating having a high degree of lubricity. Trocars
are used to introduce larger-sized implants and/or surgical tools,
especially for minimally invasive surgery. Like needles, they have
friction problems and can cause damage at the site of
insertion.
[0018] Soft tissue implants such as breast, penile, and testicular
implants, as well as devices such as pulsatile mechanical blood
pumps suffer from diffusion problems. In the case of breast
implants, huge liability has been incurred from silicone leaking
out and causing potential systemic harm to the body. In the case of
blood pumps, their pumping gases and fluids leak out, with
potentially harmful side effects, as well as inconvenience caused
by additional implanted hardware to replace lost fluids and added
cost and inconvenience to the patient who has to make repeated
trips to the hospital. Also, body fluids leak in, causing the
corrosion of components which eventually cause device failure.
These corrosion problems are also faced by implantable electrodes,
leads, and sensors such as those of pacemakers and defibrillators.
Drug containers also have problems of corrosion and chemical
reactions, especially with the newer and more potent drugs, as well
as of diffusion of drugs through the container, including the
rubber stoppers used as the caps of some drug containers.
[0019] It is also mentioned that syringe components such as
plungers often get stuck or caught while pulling in fluid. Often,
excessive force is used while expelling fluids. These situations
all combine to reduce patient safety because of increased risk of
injury.
[0020] These are also similar problems to contraceptive and OB/Gyn
devices which have problems with infection, thrombosis, tissue
growth and friction causing irritation and subsequent trauma to
surrounding tissue. Likewise, grafts and cuffs such as vascular
grafts and varicose vein cuffs have problems with infection and
thrombosis. Electrodes, especially those used for esophageal
pacing, fetal monitoring, spinal epidural, and for ablation have
problems of assuring electrical conductivity to the skin.
[0021] A different problem is raised by electro medical devices
which suffer from failures caused by inadequate electromagnetic
interference (EMI) shielding. Often, this failure relates to the
use of plastic and other non-metallic parts in the electrical
assembly that cannot be easily shielded.
[0022] Non-medical devices have other problems as well that could
be solved by a coating as described above. For example, magnets
have hydrogen embrittlement and subsequent degradation problems.
These problems are acute in the new high-strength rare-earth
magnets (e.g. Neodymium Iron Boron). This happens because hydrogen
diffuses into the material and causes failure. Hydrogen
embrittlement is also a problem in the aircraft industry with
titanium and other structural materials.
[0023] Another problem that could be solved with a coating as
described above is the sticking inside of a mold. The molded part
sometimes sticks to the mold, destroying the part or the mold.
Molds are presently made primarily of metal or ceramics, which
makes then very expensive to make.
[0024] Disk drives might also benefit from the present invention.
Specifically, EMI problems and friction problems could be
eliminated with a coating like the present invention.
[0025] Another industry which could benefit from such a coating is
in footwear. Polyurethane-based soccer shoes suffer from
degradation of the polymer caused by high humidity conditions and
subsequent diffusion of water vapor across the membranes used in
the shoe.
[0026] Integrated circuits suffer from problems of moisture and ion
ingress which can result in failure of the circuit. Another problem
is the diffusion of gold used in the gold/titanium ohmic
contacts.
[0027] Magnetic media could also substantially benefit from such a
coating. The degradation over time is often the result of high
humidity conditions and physical wear of the material from contact
with a read or write head.
[0028] Fiber optic conduits could also benefit because they suffer
from the diffusion of gases and other fluids which causes their
optical properties to degrade. Superconducting and photo diodes
also suffer from diffusion barrier problems.
[0029] Fluid valves and solenoids also having sticking problems.
Their moving parts tend to stick to their static components,
resulting in intermittent or terminal component failure.
[0030] All of the problems described above can be alleviated to
some degree, and even altogether eliminated in many cases by a
coating which has the characteristics of being conductive, having a
high degree of lubricity, providing bio-compatibility, flexibility,
radio-opacity, diffusion resistance, wear and corrosion resistance,
hardness, ability to be hydrophobic or hydrophilic, adherence to
multiple materials, sterilizability, and chemical inertness and
stability.
OBJECTS AND SUMMARY OF THE INVENTION
[0031] It is an object of the present invention to provide a
conductive, non-stick coating which can be applied to materials
which can benefit from exhibiting the property of having a surface
which functions as if lubricated.
[0032] It is another object to provide a conductive, non-stick
coating which has a non-stick coating which will not burn off, wear
away or scrape away after repeated exposure to heat, friction and
sharp edges.
[0033] It is another object to provide a conductive, non-stick
coating which can flex with the material on which it is
applied.
[0034] It is another object to provide a conductive, non-stick
coating which is a ceramic.
[0035] It is another object to provide a conductive, non-stick
coating which uses a conductive ceramic as the non-stick
coating.
[0036] It is another object to provide a conductive, non-stick
coating which is an amorphous ceramic coating that can flex without
breaking or detaching itself from a substrate to which the coating
is applied.
[0037] It is another object to provide a coating which can be
applied to temperature-sensitive components which can also provide
EMI and radio frequency interference (RFI) shielding.
[0038] It is another object to increase diffusion resistance for
fluids and gases using the coating which is also flexible enough to
prevent diffusion on flexing objects.
[0039] It is another object to provide a coating which can adhere
to a plurality of different materials of an assembly so as to
provide uniform protection.
[0040] It is another object to provide a coating which is
chemically insert and stable so as to be usable in environments
where it is important that the coating be non-reactive.
[0041] It is another object to provide a conductive, non-stick
coating which uses transition metal nitrides, carbides and oxides
as the ceramic coating.
[0042] It is another object to provide a conductive, non-stick
coating which has the ceramic coating applied through sputtering to
produce an amorphous ceramic coating.
[0043] It is another object to provide a conductive, non-stick
coating which is cost effective to produce, and simple and
efficient to apply to various substrate surfaces, including metals,
plastics, composites, ceramics, semiconductors, magnets, and
tissues.
[0044] It is another object to provide a conductive, non-stick
coating which is radio-opaque, bio-compatible, diffusion resistant,
corrosion resistant, sterilizable, and adherent in nature.
[0045] It is another object to provide a conductive, non-stick
coating at or near room temperature, which permits the coating to
be applied to many heat-sensitive materials and substrates such as
plastics, semiconductors, magnets, and tissues.
[0046] In accordance with these and other objects of the present
invention, the advantages of the invention will become more fully
apparent from the description and claims which follow, or may be
learned by the practice of the invention.
[0047] The present invention provides in a preferred embodiment a
ceramic coating which is conductive, flexible and provides a
surface which functions as if it were lubricated. The manufacturing
process produces a coating of titanium nitride on a surface of a
desired substrate material. The coating is amorphous, enabling the
substrate to bend if desired.
[0048] One aspect of the invention is the considerably improved
durability of the ceramic coating. Unlike other coatings, the
present invention does not burn away, flake or scrape off after
repeated exposure to heat and abrasion from sharp edges.
[0049] These and other objects, features, advantages and
alternative aspects of the present invention will become apparent
to those skilled in the art from a consideration of the following
detailed description taken in combination with the accompanying
drawings.
DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 is a schematic diagram of a sputtering chamber used
in the direct sputtering manufacturing process of the present
invention.
[0051] FIG. 2 is a diagram of the components of a pulsatile blood
pump, showing where diffusion of gases and liquids occurs which
leads to failure or reduced performance of the pump, and possible
health consequences to the patient.
[0052] FIG. 3 is a cross-sectional diagram of the presently
preferred embodiment for a diffusion barrier in medical
devices.
DETAILED DESCRIPTION OF THE INVENTION
[0053] Reference will now be made to the drawings in which the
various elements of the present invention will be given numerical
designations and in which the invention will be discussed so as to
enable one skilled in the art to make and use the invention. It is
to be understood that the following description is only exemplary
of the principles of the present invention, and should not be
viewed as narrowing the claims which follow.
[0054] The present invention is comprised of a method of applying
the conductive, non-stick coating, at or near room temperature, as
well as the particular materials which can benefit from the coating
in their normal use. In other words, devices, instruments and
various apparati can take advantage of being coated. These devices
include those which can benefit from a conductive wear resistant
coating which can also provide the benefits of being conductive and
amorphous (and thus flexible).
[0055] Specifically, the conductive, non-stick coating is a ceramic
coating. In the preferred embodiment, the ceramic coating is
composed of titanium nitride (TiN) which is applied over the
substrate by any appropriate method, such as those to be discussed
later.
[0056] Advantageously, the ceramic coating of the present invention
can be applied in relatively thin layers to substrates, typically
on the order of Angstroms.
[0057] Most important to the present invention are the properties
of the ceramic coating composed of TiN. It should also be mentioned
that while the preferred embodiment uses TiN as the ceramic
coating, there are other ceramics from the family of ceramics known
as transition metal nitrides which might be used in the present
invention. These ceramic coating materials include titanium
nitride, among others. These materials are classified in terms of
properties of hardness, corrosion resistance, color and high
spectral reflectance (smoothness). What is important to the
preferred embodiment of the present invention is that the material
selected for the ceramic coating 104 have the desirable
characteristics of TiN. In electrosurgical instruments, it is
appreciated that the most important of these characteristics are
that the coating (a) be conductive, (b) act amorphous after
application to the electrosurgical instrument, and (c) have a high
degree of lubricity to thereby flow smoothly through tissue being
cut/cauterized. It should also be realized that TiN can be used
alone or in combination with other materials having desirable
characteristics. These other materials might also include other
conductive (transition metal nitrides) or non-conductive
ceramics.
[0058] Although never applied in an amorphous form by others using
a room-temperature process in any of the applications to be
described, Titanium Nitride is a ceramic whose crystalline form is
well known for its advantageous properties of hardness, wear
resistance, inertness, lubricity, biocompatibility, diffusion
resistance, corrosion resistance and thermal stability in such
applications where a low friction interface is needed to protect
moving parts from wear. While it is the properties of electrical as
well as thermal conductivity jointly with lubricity which make it
attractive as a suitable coating for an electrosurgical blade, it
is often the case that only one or two of the characteristics of
the coating are used by the other embodiments of the present
invention.
[0059] The preferred process of applying the coating to different
substrates is the process of sputtering. However, it is helpful to
know at this stage that advantageously, the TiN can be applied
using sputtering at room or near-room temperatures, significantly
simplifying the manufacturing process. TiN can also be applied with
high dimensional accuracy to obtain an even coating thickness along
all surfaces. As TiN can be applied at thicknesses in the Angstrom
level, the coated part's dimensions are not materially affected.
Furthermore, TiN exhibits a very high load carrying capacity and
toughness. TiN also has excellent adhesion qualities so that it
does not spall, even under plastic deformation of the surface. The
high toughness and excellent adhesion properties are due to a
metallurgical bonding between some substrates and the TiN coating.
In particular, the TiN coating bonds well with other metals such as
steel and stainless steel.
[0060] Most importantly, however, TiN advantageously has high
hardness and low friction coefficients (referred to as lubricity).
This property of lubricity enables the conductive, non-stick
coating to glide through tissue for extended periods of time
between cleaning. But unlike Teflon (TM) coatings, TiN will not
burn off or wear away quickly from repeated use to leave a
substrate exposed. The ceramic TiN either has no wear, or wears
substantially less than, for example, the Teflon (TM) coating used
in the prior art because Teflon (TM) burns away, and peels off the
substrate. Consequently, the present invention has a longer useful
lifespan.
[0061] Most advantageously, the TiN ceramic coating of the present
invention also has great flexibility. The coating process allows
the TiN to be applied on surfaces which are not normally able to
receive such a coating. This includes surface materials such as
plastics, magnets, semiconductors, and other heat-sensitive
materials including aluminum. The present invention also has a much
stronger bond between a base metal substrate and its ceramic
coating. This bond extends down to the molecular level. More
specifically, there is a metallurgical bonding between a metallic
substrate and the TiN coating. What is created is defined as an
interfacial nanometer layer consisting of both the base metal
substrate and the TiN ceramic coating. This interfacial zone is
created in the first stage of the coating process when TiN is
sputtered onto the base metal substrate. In other words, it is
accurate to state that the TiN ceramic coating can be referred to
as an amorphous bond, having no crystalline structure subject to
fracturing. The amorphous TiN ceramic coating can therefore flex
integrally with the base metal substrate to which it is
attached.
[0062] When examining the potential applications of the non-stick
coating of the present invention, the list is impressive, and
ranges from simple devices to high-tech equipment. The following
list is only provided as an example of applications. Items which
can benefit from the ceramic coating of the present invention
include scissors, knives, drill bits, reamers, saw blades, pliers,
end mills, wire cutters, precision coining dies, rollers, pins,
screws, bore gauges, stamp metal forming tools, extrusion dies,
spool lips for spinning reels, counter bores, taps broaches, gear
cutters, bearings bushings, gears, splines, actuators, push rods,
cams, cam shafts, hobs, punches, valve stems, router bits, engine
parts, blanking dies, resistance welding electrodes, scrapers,
gouges, countersinks, counterbores, silicon wafers and chips, pump
plungers, embroidery needles, VLSI semiconductors, compressor
blades/vanes, jewelry, door hardware, writing instruments, eyeglass
frames, shafts and seals, marine hardware, plumbing fixtures,
slitters, aerospace components, plastic molds, dental instruments
and devices, food processing equipment, key duplicators, forming
dies, cutting tools, granulator blades, powdered metal dies,
seaming rolls, burnishers, engravers, minting devices, razor
blades, toy components, umbrellas, optical fibers, integrated
circuits, video/audio heads, video/audio tapes, computer floppy
disks, packaging, solar cells, kitchen utensils, window panes, golf
clubs, bicycle components, reflectors, spark plugs, lamp shades,
key chains, piston rings, fluid pumps, super conducting thin films,
photo diodes, light emitting diodes, diode lasers, electrodes,
electrochemical cells, thermolytic coolers, nuclear fuel pellets,
magnetic recording media and heads, fluid valves, solenoids, disk
drives, circuits to provide protection from EMI, circuit boards,
belts, footwear, UV adhesives, tubing, casters, filters, paper
products, actuators, fishing equipment, etc.
[0063] Some of the specific benefits which are provided by the
ceramic coating include biocompatibility, a continuous coating, a
smooth coating, a non-stick coating (reduces friction and
eliminates galling and seizing), it is aesthetically appealing,
corrosion resistant, wear resistant, fatigue resistant,
sterilizable, generally radio opaque, applicable to flexible
surfaces, adheres to a variety of surfaces which comprises
different materials including composites, is applicable as a
room-temperature process, does not introduce residual stresses, is
conductive, is conformal and thin, and can act as a diffusion
barrier.
[0064] Other applications include using the coating for integrated
circuits. Specifically, integrated circuits currently use a
titanium gold two-step process for the circuit. The coating should
result in higher yield production, better purity, a higher
diffusion barrier, equal or improved conductivity, applied in a
one-step process instead of two, and should result in less
expensive operation.
[0065] Regarding audio/video recording equipment and media, the
potential benefits are increased head life and longevity of the
media, improved quality of audio or video reproduction, less wear
on the media, and the ability to coat plastics and thereby replace
metal heads.
[0066] Regarding kitchen utensils such as pots and pans, the
coating can be applied to aluminum, while Teflon (TM) cannot, it
will resist scratching and chipping better, it will result in a pot
or pan with a longer life, it is non-stick, and metal spoons,
spatulas and other metal utensils can be used without fear of
damaging the coating.
[0067] Regarding plastic gears, the potential benefits are improved
wear, less weight, lower costs, maintaining of dimensional
accuracy, and longer life.
[0068] Regarding razor blades, there should be less skin
irritation, lower costs of producing blades, improved quality, and
a large marketing advantage.
[0069] Regarding spark plugs, the coating should provide longer
life, reduced fouling and improved performance, particularly in the
two cycle oil-mix variety.
[0070] In summary, the TiN ceramic coating of the present invention
provides many unique advantages over the prior art. The TiN ceramic
coating does not significantly wear or burn off, thereby providing
improved reliability and durability, and not evolving by-product
gases. Advantageously, the TiN ceramic coating can also be
repeatedly cleaned so that the device which is coated can be reused
many times. Furthermore, many different sterilization techniques
can be used without damaging the TiN coating.
[0071] While the invention teaches that the substrate can be
stainless steel, other materials can also be used. These other
materials might also be conductive metals such as titanium, but can
also include non-conductive materials such as plastics.
[0072] A final advantage in these non-medical applications
described above concerns the manufacturing process for applying the
ceramic coating. In a preferred embodiment, the TiN ceramic coating
is applied to a stainless steel blade using a room temperature
direct sputtering process. Sputtering is a room or relatively low
temperature process by which a controlled thin film of Titanium
Nitride is uniformly deposited on the stainless steel blade or any
other substrate.
[0073] The sputtering process itself is relatively simple, and has
numerous advantages for the present invention. For example, the
sputtering process does not change the characteristics of the base
metal substrate or the TiN ceramic coating. The other advantages
become obvious with an examination of the sputtering process.
[0074] There are two forms of sputtering which are described
herein. The first form of sputtering is known as direct sputtering.
This means that the sputtering is done directly from a TiN source.
TiN sources are available commercially, and pure TiN can be coated
onto a base metal substrate using radio frequency sources in a
non-reactive atmosphere.
[0075] Another method of applying TiN to a base metal substrate is
through the process of reactive sputtering. In this process, the
reactive atmosphere must be composed of nitrogen. The titanium
reacts with the nitrogen atmosphere to form titanium nitride. The
TiN then coats the surface of the stainless steel.
[0076] The process of both direct and reactive sputtering involves
much of the same equipment as shown in FIG. 1. The sputtering takes
place in a stainless steel chamber 10. In this preferred
embodiment, the stainless steel chamber 10 has dimensions of
approximately 18 inches in diameter and 12 inches in height. The
actual sputtering function is accomplished by sputtering guns 12
which are generally located at the top of the stainless steel
chamber 10. The sputtering guns 12 are capable of movement in both
the horizontal and vertical directions as desired.
[0077] The sputtering system described above is accomplished using
standard equipment readily available for manufacturing. An example
of the direct sputtering process is as follows. The stainless steel
chamber 10 is evacuated of ambient air through evacuation port 14.
An inert gas such as argon is then fed into the stainless steel
chamber 10 through a gas port 16. The argon gas is ionized using
the cathode 18 and the anode 20 to generate an ion flux 22 which
strikes the Titanium Nitride 24. The impact of the ion flux 22 will
eject TiN sputtered flux 26 which travels and adheres to the base
substrate 30. It is important to note that there are other
sputtering processes well known to those skilled in the art which
are also appropriate for applying the TiN ceramic coating 26.
[0078] While sputtering times may vary, experimentally it has been
determined that the sputtering time is generally 1 to 1.5 hours to
generate a TiN ceramic coating 26 on the base metal substrate 30
which is approximately 0.5 microns thick. Generally it has been
found that the sputtering process applies the TiN ceramic coating
26 according to a linear function, so the application time is
easily adjusted accordingly to obtain the desired thickness. The
0.5 micrometer thick TiN coating thus corresponds to a TiN
deposition rate of approximately 1 angstrom thickness being added
every second.
[0079] The process above has described the application process for
applying the ceramic coating to a metallic substrate. In general,
it is important to understand that sputtering is a momentum
transfer process. It is a process wherein constituent atoms of the
material are ejected from surface of a target because of momentum
exchange associated with bombardment by energetic particles. The
bombarding species are generally ions of heavy inert gas, usually
argon. Sputtering may be used for both surface etching and/or
coating. The flux of sputtered atoms that may collide repeatedly
with the working gas atoms before reaching the substrate where they
condense to form a coating of the target material.
[0080] A key difference between coating on metals and coating on
plastics is that plasma is used to modify and/or pretreat the
surface of the plastic to a greater extent on plastics than on
metals. For coating certain plastics such as silicone, a plasma
treatment can be given in a separate chamber or by using the same
sputtering machine used for coating at lower energy levels at which
plasma forms but no or minimal sputtering occurs. This
pre-treatment helps the coating adhere better to the plastic
substrate. For the pre-treatment of plastics to be coated, the
plastic surface is in contact with the plasma, and plasma ion
bombardment on the surface modifies the plastic surface by plasma
etching which is more conducive to receiving the target atoms. This
promotes a dense, fine-grained amorphous structure on the surface
depending on the process conditions such as pressure and power. The
bombardment effects will give the target atoms enough energy to get
into the surface layers of the plastic, thereby giving excellent
bonding of the coating with the substrate. The flux of sputtered
material leaving the target will be identical in composition to the
target.
[0081] The quality of the coating depends on the sputter emission
directions, the gas phase transport, and the substrate-sticking
coefficient of the constituents. Because the coating target
material transfers to vapor phase by a mechanical process (momentum
transfer) rather than by a chemical or thermal process, the heating
of the substrate can be controlled by carefully adjusting the
conditions (keeping sputtering energy levels and thus temperatures
low). This adjustment makes it possible to coat plastic surfaces at
room or near room temperature without damaging the substrate.
[0082] While the presently preferred method of application of the
ceramic to the substrate is through sputtering, it should be
apparent that there are other methods. These include such methods
as CVD and plasma deposition. Therefore, the application method of
sputtering should not be considered limiting in the present
invention.
[0083] It should be mentioned that TiN also differs from other
state of the art coatings for base metals in that it does not
evolve dangerous gases. When heated, TiN does not evolve any
gases.
[0084] While the presently preferred embodiment of the invention
emphasize the amorphous coating of a ceramic on the base metal
substrate, it should also be realized that crystalline coatings can
also be used.
[0085] The materials to which the ceramic coating of the present
invention is applied above are generally considered those which are
found specifically in non-medical applications. However, the
obvious benefits of the present invention to the medical industry
should be examined carefully because of the substantial benefits
that can result.
[0086] From a short list of the medical devices, implants and
instruments which can be coated with the ceramic coating of the
present invention, the advantages of the present invention become
more obvious. First, mechanical devices which can benefit from the
present invention include blood pumps such as Ventricular Assist
Devices, Artificial Hearts, Intra-Aortic Balloon Pumps and
Impellers. The coating is applied to most plastic, metallic and
ceramic components including magnets which can be coated at the
room or near room temperature process to thereby not affect the
magnetic properties. Furthermore, the coating provides such
advantageous features as bio-compatibility including non-toxicity,
even when the underlying material might not be bio-compatible. The
coating can also function as corrosion resistance, and even as a
diffusion barrier.
[0087] Not only can the coating of the present invention be applied
to the blood-contacting surfaces, but also to the exterior of
implanted device. Such devices include balloons such as epitaxis,
catheter, occluder, intra-aortic balloons and angioplasty balloons.
The coating can also be disposed on diaphragms, volume displacement
chambers, and associated fluid paths in plastic tubes.
[0088] When addressing motors, the coating can also be used on
bearings and bearing components. These components include balls,
pivots, and inner and outer races used in actuators for medical
devices. The result is a reduction in wear and thus increased
lifespan of the medical devices.
[0089] Other medical devices that can benefit are catheters,
especially those used in long-term indwelling procedures,
cardiotomy and cerebrovascular, and those needing a safer and more
reliable radio-opaque covering or marker. Soft-tissue implants
include intravaginal and colostomy pouches, breast implants, penile
and testicular implants.
[0090] Valves of the type used in hearts can also be improved by
the coating disposed on disks and struts. Existing stents made from
metal, ceramic and plastic and used for an annulplasty ring can be
coated to provide the desired flexible and bio-compatible outer
covering.
[0091] Shunts such as a dialysis shunt, an A-V shunt, a central
nervous system shunt, an endolymphatic shunt tube, a peritoneal
shunt and a hydrocephalys shunt can also be coated.
[0092] Silicone-based medical devices including inhaler seals,
valves for laryngechtomy prostheses, nasal tampons, and tubes can
also be coated.
[0093] The present invention can also serve to coat a plastic
sheath covering current-carrying loads, as well as the leads
themselves, connectors, feedthroughs for any implanted,
electrically powered device such as a pacemaker, defibrillator,
cardioverter, bipotential electrodes and leads, neural stimulators
such as a cerebellar, brain, cranial, nerve and spinal cord device.
The implanted devices can also be optical or cochlear in
nature.
[0094] Other devices that can benefit include arterial filters,
vascular grafts, varicose vein cuffs, as well as intracardiac,
pledget, pericardial and epicardial patches. Contraceptive and
Ob/Gyn devices include a plug prostheses, tubal occlusion devices
(band, clip, insert and valve), urethal devices such as a stent,
dilator and a catheter, IUDs and diaphragm. Other devices include
an angiographic and other guide wire.
[0095] Sensors and transducers which are of the implantable variety
as well as the non-implantable short-term variety can be coated.
These include those used in measuring blood flow, blood pressure,
vascular access devices, those which can be protected with a
conductive layer of the coating, a catheter tip pressure
transducer, and an invasive glucose sensor. The coating itself can
be used as sensing material which detects changes in its property
such as conductivity as a function of the thing being measured.
[0096] Occluders include those used in patent ductus arteriosus. A
tracheotomy tube can also be coated.
[0097] Finally, hermetically sealed cans and other enclosures
having a plastic-based substrate can be coated, including those
used to encase electronics of any type, for actuators, sensors and
fluids.
[0098] Surgical instruments and devices can also be coated. Such
devices include catheters of all types, needles, trocars,
feeding/breathing tubes, transfusion tubes, clips, surgical
staples, electrosurgical instruments, pumps, as well as knives,
scalpels, scissors, clamps, coagulators, dilators, retractors,
examination gloves, non-absorbable sutures and ligatures,
microtomes, surgical meshes, tonsil dissectors, and vascular
clamps, stereotaxis instruments and accessories, and heat
exchangers.
[0099] There are also various orthopedic devices that can be
coated, such as synthetic ligaments and tendons, fallopian tube
replacements, ear prostheses, Stiennman Pins, bone plates and skull
plates.
[0100] Measuring and analytical devices include blood measuring and
evaluating devices, blood collection systems, containers for blood
and other sensitive fluids, linings, tubes and blood-contacting
surfaces of laboratory instruments, and coatings for leads used in
such things as an EEG, ECG, etc.
[0101] Other devices that can be coated are syringes, plungers,
intra ocular lenses, drug containers and packaging.
[0102] It should ne be surprising that the preceding pages do not
represent an exhaustive list of all of the possible medical
devices, instruments and applications of the present invention, but
it serves to suggest many of the applications.
[0103] One particularly important medical application of the
present invention is in diffusion barriers. Many implantable
devices such as a blood pump, as well as soft-tissue implants
(breast, penile and testicular) have diffusion barriers containing
fluids. The diffusion barriers are supposed to prevent the passage
of working fluids (such as a lubricating oil) from within the
medical device to the body. Likewise, body fluids (blood) are not
supposed to enter into the medical device. However, it is the case
that diffusion barriers are soft membranes which are
disadvantageously permeable to gases and fluids. The present
invention functions as a diffusion barrier to prevent or at least
reduce the passage of gases and fluids through the permeable
membranes.
[0104] To understand the nature of the problem, it is helpful to
look at a diagram of a pulsatile blood pump. FIG. 2 is a blood pump
40. The blood pump 40 has a pumping chamber 42 in which is disposed
a polyurethane membrane 44 which functions as a diaphragm. On one
side of the membrane 44 is blood 46. On the other side of the
membrane 44 is a working fluid 48 of the blood pump 40. The pumping
chamber 42 is coupled via an energy converter 50 to a volume
displacement chamber 52. Within the volume displacement chamber 52
is the working fluid 48 of the blood pump 40.
[0105] The arrows 54 indicate that diffusion occurs through the
membrane 44 between the blood 46 and the working fluid 48 in the
pumping chamber 42, and between the working fluid 48 and tissues 56
which surround the volume displacement chamber 52. It should be
remembered that the working fluid 48 of the blood pump 40 is
typically some of type of lubricating oil such as silicone oil.
Obviously, it is desirable to prevent blood 46 and working fluid 48
from passing through the flexible membrane 44.
[0106] Presently, existing pulsatile pumps accept diffusion of
blood and working fluids, and simply try to treat the symptoms of
the problem. In other words, the pulsatile pumps are often provided
with a priming port for receiving gas or working fluids.
[0107] Allowing diffusion is detrimental to the pulsatile pumps for
several reasons. First, providing a priming port enables
contaminants to enter into the device, thus increasing the chances
of infection. Second, the passage of blood into the pumping
mechanism increases speed of corrosion of internal components, and
thus increases the chances of failure of the device.
[0108] There remain unanswered questions regarding the long-term
health effects of silicone. It is reported that connective tissue
diseases and breast cancer are one result. However, it is obviously
prudent to reduce the introduction of silicone oils into the blood
stream.
[0109] It has been determined experimentally that some pulsatile
blood pump devices will lose between 10 and 15 cc's of silicone oil
into the body per year. The loss of this volume of working fluid is
also detrimental to the operation of the device because it reduces
the stroke volume, for example, by 15% to 25%. Such a loss in
stroke volume is likely to be an unacceptably high loss. However,
electrohydraulic pumps are not the only ones whose performance
suffers from diffusion. Pusher-plate devices are also susceptible
to failure.
[0110] Referring to the volume displacement chambers, the membranes
used in these chambers also allow body fluids into the device.
These body fluids contain ions and moisture which cause corrosion
and wear of the blood pump's energy converter, thus leading to
eventual failure of the pump due to short-circuiting or
corrosion.
[0111] Previous attempts to reduce permeability of the membrane
have failed to stop diffusion. For example, multiple membrane
layers or different membrane materials have been tried.
Unfortunately, none of these attempts have succeeded.
[0112] The present invention advantageously reduces diffusion of
working fluids and blood through the membrane by coating the
membrane with a flexible, bio-compatible, corrosion resistant
ceramic coating.
[0113] FIG. 3 is a cross-sectional profile view of the presently
preferred embodiment of a membrane 60 to be used in a pumping
mechanism. In the presently preferred embodiment, a layer of the
ceramic coating 62 is disposed between two layers 64 and 66 of the
membranes. In this embodiment, polyurethane is used for the
membranes 64 and 66.
[0114] The thickness of the ceramic coating 62 has experimentally
been determined to be within the range of approximately 5000 to
10,000 angstroms. The ceramic coating 62 is deposited on one of the
polyurethane membranes 64 or 66 after vacuum forming or solution
casting. During sputtering, the polyurethane surface is energized
by the argon plasma. Accordingly, the ions of the ceramic coating
material will actively bond with the surface, thus creating a
diffusion layer which is amorphous.
[0115] The second layer of polyurethane will form an active surface
while heated during vacuum forming. During solution casting, the
polymer will be in a liquid phase, enabling the polyurethane to
enter surface micro-irregularities of the ceramic coating. This
bonding will prevent surface delamination.
[0116] Because amorphous Titanium Nitride is insert, fatigue
resistance, bio-compatible, corrosion resistant and lightweight.
Furthermore, TiN is hydrophobic, and thus prevents the diffusion of
any liquids through its surface. It is possible to also make the
surface hydrophilic by appropriate surface plasma treatments.
Diffusion occurs predominantly along grain boundaries. Since the
amorphous nature of the TiN coating does not have any grain
boundaries, diffusion through the TiN ceramic layer 62 is greatly
reduced.
[0117] When examining other materials to use as a diffusion barrier
coating between the polyurethane layers, it is observed that gold
can also be sputtered. However, gold is likely to fail due to its
low fatigue resistance under continuous flexing and stretching
conditions of the membrane in a blood pump. Furthermore, gold is
relatively expensive compared to TiN. Silver and copper are
corrosive and hence cannot be used in this medical application.
[0118] However, it is possible that other ceramics of the family of
TiN can be used as the diffusion barrier. These ceramics include
Aluminum Oxide, Titanium Carbide, Silicon Carbide, Silicon Nitride,
Boron Nitride and Zirconia. The advantages of these ceramics is
that like TiN, they provide an amorphous coating through
sputtering, they also inhibit permeability of gases and fluids,
they can be deposited at room or near-room temperature, they can be
applied to multiple materials to thereby provide a same coating on
different parts and materials of the pump, and they are all
bio-compatible.
[0119] It is to be understood that the above-described embodiments
are only illustrative of the application of the principles of the
present invention. Numerous modifications and alternative
arrangements may be devised by those skilled in the art without
departing from the spirit and scope of the present invention.
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