U.S. patent application number 10/115676 was filed with the patent office on 2003-05-22 for flexible electrode array for artificial vision.
This patent application is currently assigned to The Regents of the University of California.. Invention is credited to Hamilton, Julie, Humayun, Mark S., Krulevitch, Peter, Maghribi, Mariam N., Polla, Dennis L..
Application Number | 20030097165 10/115676 |
Document ID | / |
Family ID | 25538095 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030097165 |
Kind Code |
A1 |
Krulevitch, Peter ; et
al. |
May 22, 2003 |
Flexible electrode array for artificial vision
Abstract
An image is captured or otherwise converted into a signal in an
artificial vision system. The signal is transmitted to the retina
utilizing an implant. The implant consists of a polymer substrate
made of a compliant material such as poly(dimethylsiloxane) or
PDMS. The polymer substrate is conformable to the shape of the
retina. Electrodes and conductive leads are embedded in the polymer
substrate. The conductive leads and the electrodes transmit the
signal representing the image to the cells in the retina. The
signal representing the image stimulates cells in the retina.
Inventors: |
Krulevitch, Peter;
(Pleasanton, CA) ; Polla, Dennis L.; (Roseville,
MN) ; Maghribi, Mariam N.; (Davis, CA) ;
Hamilton, Julie; (Tracy, CA) ; Humayun, Mark S.;
(La Canada, CA) |
Correspondence
Address: |
Eddie E. Scott
P.O. Box 808, L-703
Livermore
CA
94551
US
|
Assignee: |
The Regents of the University of
California.
|
Family ID: |
25538095 |
Appl. No.: |
10/115676 |
Filed: |
April 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10115676 |
Apr 3, 2002 |
|
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09992248 |
Nov 16, 2001 |
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Current U.S.
Class: |
607/115 |
Current CPC
Class: |
Y10T 29/49155 20150115;
H05K 2201/09481 20130101; H05K 3/205 20130101; Y10S 623/905
20130101; Y10T 29/49224 20150115; Y10S 623/926 20130101; A61N
1/0543 20130101; H05K 2203/0733 20130101; Y10T 29/49147 20150115;
Y10S 623/90 20130101; Y10S 623/901 20130101; H05K 2201/0162
20130101; Y10T 29/49128 20150115; Y10T 29/4913 20150115; Y10T
29/49139 20150115; H05K 3/4007 20130101; Y10T 29/49165 20150115;
Y10T 29/49169 20150115; H05K 1/118 20130101 |
Class at
Publication: |
607/115 |
International
Class: |
A61N 001/05 |
Goverment Interests
[0001] The United States Government has rights in this invention
pursuant to Contract No. W-7405-ENG-48 between the United States
Department of Energy and the University of California for the
operation of Lawrence Livermore National Laboratory.
Claims
The invention claimed is:
1. An electrode array for connection to tissue containing cells,
comprising: a substrate composed of a polymer that has the ability
to conform to various shapes of said tissue, and electrodes
embedded in said substrate for contacting said tissue.
2. The electrode array for connection to tissue containing cells of
claim 1, including conductive leads connected to said
electrodes.
3. The electrode array for connection to tissue containing cells of
claim 2, wherein said polymer is flexible.
4. The electrode array for connection to tissue containing cells of
claim 2, wherein said polymer is stretchable.
5. The electrode array for connection to tissue containing cells of
claim 2, wherein said polymer is poly(dimethylsiloxane).
6. The electrode array for connection to tissue containing cells of
claim 1, wherein said electrodes for contacting said tissue are
useful for stimulating said cells.
7. The electrode array for connection to tissue containing cells of
claim 1, wherein said conductive leads are connected to a device
for transferring a visual image signal.
8. The electrode array for connection to tissue containing cells of
claim 2, wherein said electrodes for contacting said tissue are
useful for stimulating said cells and said conductive leads are
connected to a device for transferring a visual image signal.
9. The electrode array for connection to tissue containing cells of
claim 8, wherein said tissue is retina tissue.
10. The electrode array for connection to tissue containing cells
of claim 9, wherein said substrate is composed of a flexible
polymer and has the ability to conform to the shape of said retina
tissue.
11. The electrode array for connection to tissue containing cells
of claim 10, wherein said conductive leads and said electrodes
transmit said visual image signal to said cells in said retina
tissue.
12. The electrode array for connection to tissue containing cells
of claim 11, wherein said cells are retinal neurons.
13. The electrode array for connection to tissue containing cells
of claim 1, including micromachined points, barbs and/or hooks or
tacks in said electrodes embedded in said substrate for contacting
said tissue.
14. The electrode array for connection to tissue containing cells
of claim 1, wherein said polymer is an elastomer.
15. The electrode array for connection to tissue containing cells
of claim 1, wherein said polymer is an elastomer that is
flexible.
16. The electrode array for connection to tissue containing cells
of claim 1, wherein said polymer is liquid silicone rubber
(LSR).
17. The electrode array for connection to tissue containing cells
of claim 1, wherein said elastomer is poly(dimethylsiloxane).
18. An electrode array for an artificial vision system for
receiving an image signal representing an image and transferring
said image signal to a retina, comprising: an electrode array
including a polymer substrate, said polymer substrate being
flexible and stretchable and having the ability to conform to the
shape of said retina, and electrodes embedded in said polymer
substrate.
19. The artificial vision system of claim 18, wherein said
electrodes embedded in said polymer substrate contact said retina
and said signal representing said image stimulates cells in said
retina.
20. The artificial vision system of claim 18, wherein said
conductive leads and said electrodes transmit said signal
representing said image to said cells in said retina.
21. The artificial vision system of claim 20, wherein said cells
are retinal neurons.
22. The artificial vision system of claim 18, wherein said device
for transmitting a signal representing said image is a video
camera.
23. The artificial vision system of claim 18, wherein said
electrodes include micromachined barbs and/or hooks or tacks for
anchoring said implant to said retina.
24. The artificial vision system of claim 18, wherein said polymer
is poly(dimethylsiloxane).
25. An electrode array for an artificial vision system for
receiving an image signal representing an image into an eye and to
a retina, comprising: an implant connected to said retina
consisting of a flexible polymer substrate, said flexible polymer
substrate being flexible and stretchable and having the ability to
conform to the shape of said retina, and electrodes embedded in
said elastomer substrate.
26. The artificial vision system of claim 25, wherein said
electrodes embedded in said flexible polymer substrate contact said
retina and said signal representing said image stimulates cells in
said retina.
27. The system of claim 25, including conductive leads connected to
said electrodes wherein said conductive leads and said electrodes
transmit said signal representing said image to said cells in said
retina.
28. The system of claim 27, wherein said cells are retinal
neurons.
29. The system of claim 25, wherein said device for transmitting a
signal representing said image is a video camera.
30. The system of claim 25, wherein said electrodes include
micromachined barbs and/or hooks or tacks for anchoring said
implant to said retina.
31. The system of claim 25, wherein said flexible polymer is
poly(dimethylsiloxane).
32. A method of processing an electrode array for connection to
tissue containing cells, comprising the steps of: implementing
initial processing steps on a polymer substrate that has the
ability to conform to various shapes of said tissue, plating or
otherwise depositing a conductive material on said polymer
substrate to form electrodes on said polymer substrate for
contacting said tissue, patterning conducting lines on said polymer
substrate, and implementing final processing steps on said polymer
substrate.
33. The method of processing an electrode array of claim 32,
wherein said conductive material is biocompatable.
34. The method of processing an electrode array of claim 32,
wherein said conductive material is implantable.
35. The method of processing an electrode array of claim 32,
wherein said conductive material is gold or platinum.
36. The method of processing an electrode array of claim 32,
wherein said polymer is an elastomer.
37. The method of processing an electrode array of claim 32,
wherein said polymer is an elastomer that is flexible.
38. The method of processing an electrode array of claim 32,
wherein said polymer is an elastomer that is flexible and
stretchable.
39. The method of processing an electrode array of claim 32,
wherein said elastomer is poly(dimethylsiloxane).
40. A system of fabricating a flexible electrode array, comprising
the steps of: spin-coating a PDMS layer onto a handle wafer that
has been pre-coated with a conductive seed layer, patterning said
PDMS to expose said conductive seed layer to form electrodes,
plating said electrodes slightly higher than the thickness of said
PDMS until said electrodes form slight mushroom caps which later
will prevent said electrodes from popping out of said PDMS when
said PDMS is removed from said handle wafer, and patterning
conducing lines on said PDMS.
41. The system of fabricating a flexible electrode array of claim
40, wherein said step of patterning conducing lines on said PDMS is
conducted using thin film deposition.
42. The system of fabricating a flexible electrode array of claim
40, wherein said step of patterning conducing lines on said PDMS is
conducted using photolithography.
43. The system of fabricating a flexible electrode array of claim
40, wherein said step of patterning conducing lines on said PDMS is
conducted using shadow masking.
44. The system of fabricating a flexible electrode array of claim
40, including the step of directly embeding an electrical connector
into the device to interface with electronics.
45. The system of fabricating a flexible electrode array of claim
40, including the step of casting a PDMS capping layer to said
PDMS.
46. The system of fabricating a flexible electrode array of claim
40, including the step of bonding a PDMS capping layer to said
PDMS.
47. The system of fabricating a flexible electrode array of claim
40, wherein said conductive seed layer is biocompatible.
48. The system of fabricating a flexible electrode array of claim
40, wherein said conductive seed layer is gold.
49. The system of fabricating a flexible electrode array of claim
40, wherein said conductive seed layer is platinum.
50. The system of fabricating a flexible electrode array of claim
40, wherein said conductive seed layer is a conductive polymer
material.
51. The system of fabricating a flexible electrode array of claim
40, wherein a pre-patterned or formed PDMS layer is bonded to the
handle wafer.
52. The system of fabricating a flexible electrode array of claim
40, wherein a pre-patterned or formed PDMS layer is cast in place
with a mold
53. The system of fabricating a flexible electrode array of claim
40, wherein gold electrodes are electroplated onto said conductive
seed layer.
54. The system of fabricating a flexible electrode array of claim
40, wherein platinum electrodes are electroplated onto said
conductive seed layer.
55. The system of fabricating a flexible electrode array of claim
40, including the step of directly embedding an integrated circuit
into the device such that it interfaces with the electrode
array.
56. The system of fabricating a flexible electrode array of claim
40, including the step of spinning on a PDMS capping layer to said
PDMS.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of Endeavor
[0003] The present invention relates to electrodes and more
particularly to an electrode array that can be used for artificial
vision, that can be implanted, that is useful for surgical
insertion, that can be attached to the surface of the skin, that
can be used as a flex circuit, and that can be used in other
ways.
[0004] State of Technology
[0005] U.S. Pat. No. 4,573,481 for an implantable electrode array
by Leo A. Bullara, patented Mar. 4, 1986 provides the following
background information, "It has been known for almost 200 years
that muscle contraction can be controlled by applying an electrical
stimulus to the associated nerves. Practical long-term application
of this knowledge, however, was not possible until the relatively
recent development of totally implantable miniature electronic
circuits which avoid the risk of infection at the sites of
percutaneous connecting wires. A well-known example of this modern
technology is the artificial cardiac pacemaker which has been
successfully implanted in many patients. Modern circuitry enables
wireless control of implanted devices by wireless telemetry
communication between external and internal circuits. That is,
external controls can be used to command implanted nerve
stimulators to regain muscle control in injured limbs, to control
bladder and sphincter function, to alleviate pain and hypertension,
and to restore proper function to many other portions of an
impaired or injured nerve-muscle system. To provide an electrical
connection to the peripheral nerve which controls the muscles of
interest, an electrode (and sometimes an array of multiple
electrodes) is secured to and around the nerve bundle. A wire or
cable from the electrode is in turn connected to the implanted
package of circuitry."
[0006] U.S. Pat. No. 6,052,624 for a directional programming for
implantable electrode arrays by Carla M. Mann, patented Apr. 18,
2000 provides the following background information, "Within the
past several years, rapid advances have been made in medical
devices and apparatus for controlling chronic intractable pain. One
such apparatus involves the implantation of an electrode array
within the body to electrically stimulate the area of the spinal
cord that conducts electrochemical signals to and from the pain
site. The stimulation creates the sensation known as paresthesia,
which can be characterized as an alternative sensation that
replaces the pain signals sensed by the patient. One theory of the
mechanism of action of electrical stimulation of the spinal cord
for pain relief is the "gate control theory". This theory suggests
that by simulating cells wherein the cell activity counters the
conduction of the pain signal along the path to the brain, the pain
signal can be blocked from passage. Spinal cord stimulator and
other implantable tissue stimulator systems come in two general
types: "RF" controlled and fully implanted. The type commonly
referred to as an "RF" system includes an external transmitter
inductively coupled via an electromagnetic link to an implanted
receiver that is connected to a lead with one or more electrodes
for stimulating the tissue. The power source, e.g., a battery, for
powering the implanted receiver-stimulator as well as the control
circuitry to command the implant is maintained in the external
unit, a hand-held sized device that is typically worn on the
patient's belt or carried in a pocket. The data/power signals are
transcutaneously coupled from a cable-connected transmission coil
placed over the implanted receiver-stimulator device. The implanted
receiver-stimulator device receives the signal and generates the
stimulation. The external device usually has some patient control
over selected stimulating parameters, and can be programmed from a
physician programming system."
[0007] U.S. Pat. No. 6,230,057 for a multi-phasic microphotodiode
retinal implant and adaptive imaging retinal stimulation system by
Vincent Chow and Alan Chow, patented May 8, 2001 and assigned to
Optobionics Corporation provides the following background
information, "A variety of retinal diseases cause vision loss or
blindness by destruction of the vascular layers of the eye
including the choroid, choriocapillaris, and the outer retinal
layers including Bruch's membrane and retinal pigment epithelium.
Loss of these layers is followed by degeneration of the outer
portion of the inner retina beginning with the photoreceptor layer.
Variable sparing of the remaining inner retina composed of the
outer nuclear, outer plexiform, inner nuclear, inner plexiform,
ganglion cell and nerve fiber layers, may occur. The sparing of the
inner retina allows electrical stimulation of this structure to
produce sensations of light. Prior efforts to produce vision by
electrically stimulating various portions of the retina have been
reported. One such attempt involved an externally powered
photosensitive device with its photoactive surface and electrode
surfaces on opposite sides. The device theoretically would
stimulate the nerve fiber layer via direct placement upon this
layer from the vitreous body side. The success of this device is
unlikely due to it having to duplicate the complex frequency
modulated neural signals of the nerve fiber layer. Furthermore, the
nerve fiber layer runs in a general radial course with many layers
of overlapping fibers from different portions of the retina.
Selection of appropriate nerve fibers to stimulate to produce
formed vision would be extremely difficult, if not impossible.
Another device involved a unit consisting of a supporting base onto
which a photosensitive material such as selenium was coated. This
device was designed to be inserted through an external scleral
incision made at the posterior pole and would rest between the
sclera and choroid, or between the choroid and retina. Light would
cause a potential to develop on the photosensitive surface
producing ions that would then theoretically migrate into the
retina causing stimulation. However, because that device had no
discrete surface structure to restrict the directional flow of
charges, lateral migration and diffusion of charges would occur
thereby preventing any acceptable resolution capability. Placement
of that device between the sclera and choroid would also result in
blockage of discrete ion migration to the photoreceptor and inner
retinal layers. That was due to the presence of the choroid,
choriocapillaris, Bruch's membrane and the retinal pigment
epithelial layer all of which would block passage of those ions.
Placement of the device between the choroid and the retina would
still interpose Bruch's membrane and the retinal pigment epithelial
layer in the pathway of discrete ion migration. As that device
would be inserted into or through the highly vascular choroid of
the posterior pole, subchoroidal, intraretinal and intraorbital
hemorrhage would likely result along with disruption of blood flow
to the posterior pole. One such device was reportedly constructed
and implanted into a patient's eye resulting in light perception
but not formed imagery. A photovoltaic device artificial retina was
also disclosed in U.S. Pat. No. 5,024,223. That device was inserted
into the potential space within the retina itself. That space,
called the subretinal space, is located between the outer and inner
layers of the retina. The device was comprised of a plurality of
so-called Surface Electrode Microphotodiodes ("SEMCPs") deposited
on a single silicon crystal substrate. SEMCPs transduced light into
small electric currents that stimulated overlying and surrounding
inner retinal cells. Due to the solid substrate nature of the
SEMCPs, blockage of nutrients from the choroid to the inner retina
occurred. Even with fenestrations of various geometries, permeation
of oxygen and biological substances was not optimal. Another method
for a photovoltaic artificial retina device was reported in U.S.
Pat. No. 5,397,350, which is incorporated herein by reference. That
device was comprised of a plurality of so-called Independent
Surface Electrode Microphotodiodes (ISEMCPs), disposed within a
liquid vehicle, also for placement into the subretinal space of the
eye. Because of the open spaces between adjacent ISEMCPs, nutrients
and oxygen flowed from the outer retina into the inner retinal
layers nourishing those layers. In another embodiment of that
device, each ISEMCP included an electrical capacitor layer and was
called an ISEMCP-C. ISEMCP-Cs produced a limited opposite direction
electrical current in darkness compared to in the light, to induce
visual sensations more effectively, and to prevent electrolysis
damage to the retina due to prolonged monophasic electrical current
stimulation. These previous devices (SEMCPs, ISEMCPs, and
ISEMCP-Cs) depended upon light in the visual environment to power
them. The ability of these devices to function in continuous low
light environments was, therefore, limited. Alignment of ISEMCPs
and ISEMCP-Cs in the subretinal space so that they would all face
incident light was also difficult."
SUMMARY OF THE INVENTION
[0008] Features and advantages of the present invention will become
apparent from the following description. Applicants are providing
this description, which includes drawings and examples of specific
embodiments, to give a broad representation of the invention.
Various changes and modifications within the spirit and scope of
the invention will become apparent to those skilled in the art from
this description and by practice of the invention. The scope of the
invention is not intended to be limited to the particular forms
disclosed and the invention covers all modifications, equivalents,
and alternatives falling within the spirit and scope of the
invention as defined by the claims.
[0009] The present invention provides an electrode array system.
The system uses a substrate with embedded electrodes and conductive
leads for directly stimulating cells. The electrode array system
can conform to various shapes. The electrode array has many uses.
For example the electrode array system of the present invention
provides an artificial vision system. The electrode array system of
the present invention can provide an electrode array that is
implantable and can be used for surgical insertion. Also, the
electrode array system of the present invention can provide an
electrode array that can be attached to the surface of the skin.
The electrode array system of the present invention can provide an
electrode array that can be used in other ways. Other applications
of the electrode array system of the present invention include use
of the electrode array as a flex circuit.
[0010] In one embodiment, a method is provided for processing an
electrode array. The method includes implementing initial
processing steps on a substrate, depositing and/or plating a
conductive material on the substrate, and implementing final
processing steps on the substrate. In one embodiment the substrate
material is compliant. In another embodiment the substrate material
is flexible. In another embodiment the substrate material is
stretchable. In another embodiment the substrate material is
flexible and stretchable. In another embodiment the substrate
material and the conductive material is biocompatable. In another
embodiment the substrate material and the conductive material is
implantable. In another embodiment the conductive material is gold.
In another embodiment the conductive material is platinum. In
another embodiment the conductive material is gold with an
underlying adhesion layer of titanium.
[0011] The invention is susceptible to modifications and
alternative forms. Specific embodiments are shown by way of
example. It is to be understood that the invention is not limited
to the particular forms disclosed. The invention covers all
modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings, which are incorporated into and
constitute a part of the specification, illustrate specific
embodiments of the invention and, together with the general
description of the invention given above, and the detailed
description of the specific embodiments, serve to explain the
principles of the invention.
[0013] FIG. 1 illustrates a step of an electrode array fabrication
process wherein an electroplating seed layer is deposited onto a
handle wafer.
[0014] FIG. 2 illustrates a step of an electrode array fabrication
process wherein a patterned photoresist is produced.
[0015] FIG. 3 illustrates a step of an electrode array fabrication
process wherein a polymer is such as poly(dimethylsiloxane)--PDMS
(a form of silicone rubber) is spun or cast onto the patterned
photoresist on the handle wafer.
[0016] FIG. 4 illustrates a step of an electrode array fabrication
process wherein the remaining photoresist is removed resulting in
patterned PDMS on top of the handle wafer, revealing sections of
the underlying seed layer.
[0017] FIG. 5 illustrates a step of an electrode array fabrication
process wherein gold or platinum is electroplated through the
patterned PDMS to form electrodes.
[0018] FIG. 6 illustrates a step of an electrode array fabrication
process wherein conductive metal lines are patterned on the
PDMS.
[0019] FIG. 7 illustrates a step of an electrode array fabrication
process wherein a 2.sup.nd layer of PDMS is applied.
[0020] FIG. 8A shows a top view of the device removed from the
handle wafer.
[0021] FIG. 8B shows a bottom view of the device removed from the
handle wafer.
[0022] FIG. 9 shows the device with an encapsulated electronic chip
18 attached to the lead lines.
[0023] FIG. 10 illustrates another embodiment of an electrode array
of the present invention.
[0024] FIGS. 11A and 11B show another embodiment of an electrode
array of the present invention.
[0025] FIG. 12 illustrates an intraocular prosthesis.
[0026] FIG. 13 illustrates an artificial vision system.
[0027] FIGS. 14A and 14B illustrate embodiments of the electrode
array that include microfabricated features for improving the way
the electrode array contacts tissue.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Referring now to the drawings, to the following detailed
information, and to incorporated materials; a detailed description
of the invention, including specific embodiments, is presented. The
detailed description serves to explain the principles of the
invention. The invention is susceptible to modifications and
alternative forms. The invention is not limited to the particular
forms disclosed. The invention covers all modifications,
equivalents, and alternatives falling within the spirit and scope
of the invention as defined by the claims.
[0029] The present invention provides an electrode array for
artificial vision and a system that can be attached to the skin,
can be implanted, and has many other uses. In one embodiment an
electrode array is provided utilizing a substrate made of a
compliant material. Electrodes and conductive leads are embedded in
the substrate. The fact that the device can conform to various
shapes is advantageous. In one embodiment an electrode array is
provided utilizing a substrate made of a stretchable material. The
fact that the electrode array is stretchable is advantageous
because it will resist damage during handling. The substrate
contains embedded electrodes of a conductive material.
[0030] The electrode array has many uses. For example the electrode
array system provides an electrode array system with embedded
electrodes and conductive leads for directly stimulating cells. The
electrode array system can provide a system that is implantable and
can be used for surgical insertion. The electrode array system can
also be attached to the surface of the skin or other tissue. The
electrode array system can be used in other ways. Other
applications of the electrode array system include use as a flex
circuit. The electrode array has uses including shaped acoustic
sensors and transmitters and formed biological sensors and
stimulators for interfacing with the human body. These can be used
for applications ranging from non-destructive evaluation to sensors
for virtual reality simulators. An implantable electrode array is
shown in U.S. Pat. No. 4,573,481 by Leo A. Bullara, patented Mar.
4, 1986. The disclosure of this patent is incorporated herein in
its entirety by reference. A directional programming for
implantable electrode arrays is shown in U.S. Pat. No. 6,052,624
for by Carla M. Mann, patented Apr. 18, 2000. The disclosure of
this patent is incorporated herein in its entirety by reference. A
multi-phasic microphotodiode retinal implant and adaptive imaging
retinal stimulation system, patented May 8, 2001, is shown in U.S.
Pat. No. 6,230,057 by Vincent Chow and Alan Chow. The disclosure of
this patent is incorporated herein in its entirety by reference. A
photovoltaic artificial retina device is in U.S. Pat. No.
5,397,350. The disclosure of this patent is incorporated herein in
its entirety by reference.
[0031] Descriptions of Specific Embodiments
[0032] Referring now to FIGS. 1 through 8, embodiments of the
present invention's methods of producing electrode array systems
and electrode array systems constructed in accordance with the
present invention are shown. Electrode systems constructed in
accordance with the embodiments shown in FIGS. 1 through 8 were
constructed and successfully tested. As shown in FIGS. 1-8,
embodiments of the present invention provide a processing method
and an electrode array for connection to tissue. The electrode
array includes a substrate composed of a polymer. The polymer has
the ability to conform to various shapes of the tissue. In one
embodiment the polymer is compliant. In another embodiment the
polymer is an elastomer. In another embodiment the polymer is an
elastomer that is flexible and stretchable. In another embodiment
the elastomer is liquid silicone rubber (LSR). In another
embodiment the elastomer is poly(dimethylsiloxane) or PDMS.
[0033] Electrodes are embedded in the substrate for contacting the
tissue. Conductive leads are connected to the electrodes. The
electrodes are useful for stimulating the cells. In one embodiment
the conductive leads are connected to a device for transferring a
visual image signal. In one embodiment the cells are retina cells.
In one embodiment the substrate is composed of an elastomer and has
the ability to conform to the shape of the retina tissue.
[0034] One embodiment of the present invention provides a system of
fabricating a conformable electrode array. The system comprises the
steps of spin-coating a PDMS layer onto a handle wafer that has
been pre-coated with a conductive seed layer. The PDMS is patterned
to expose the conductive seed layer to form electrodes. One
embodiment includes the step of directly embeding an electrical
connector into the device to interface with electronics. Another
embodiment includes the step of casting a PDMS capping layer on to
the first PDMS. Another embodiment includes the step of bonding a
PDMS capping layer to the first PDMS. In one embodiment the
conductive seed layer is biocompatible. In another embodiment the
conductive seed layer is gold. In another embodiment the conductive
seed layer is platinum. In another embodiment the conductive seed
layer is a conductive polymer material. In another embodiment a
pre-patterned or formed PDMS layer is bonded to the handle wafer.
In another embodiment a pre-patterned or formed PDMS layer is cast
in place with a mold. In another embodiment the conductive seed
layer is electroplated using gold. In another embodiment the
conductive seed layer is electroplated using platinum. In another
embodiment a step of patterning conducting lines on the PDMS is
performed using thin film deposition. The conducting lines are
patterned using a combination of thin film deposition and
photolithography. In another embodiment the step of patterning
conducting lines on the PDMS is conducted using photolithography.
In another embodiment the step of patterning conducing lines on the
PDMS is conducted using shadow masking. An embodiment includes
doping the PDMS with metal particles to selectively render it
conductive. An embodiment includes removing the PDMS from the
handle wafer.
[0035] The flexible electrode array 10 shown in FIGS. 1-8 is
produced by implementing various processing steps on a substrate. A
conductive material 12 is deposited on the handle wafer 14 and
various processing steps are taken to complete the flexible
electrode array 10. The thin film conductive layer can be deposited
by evaporation. The flexible electrode array system, generally
designated by the reference numeral 10, includes a
poly(dimethylsiloxane) or PDMS (a form of silicone rubber)
substrate 11 with embedded electrodes and conductive leads. The
substrate 11 is initially positioned on a handle wafer 14.
[0036] The steps illustrated in FIGS. 1-8 and described below were
used for constructing the flexible electrode array 10. The
electrode system was constructed using a combination of
electroplating, and deposition, and patterning of thin film metals
on PDMS.
[0037] Electrode Fabrication Process
[0038] 1. Deposit Gold 12 (or Platinum) on to handle wafer 14 as
shown in FIG. 1. This provides an electroplating seed layer and
allows for removal of the PDMS from the substrate after
processing.
[0039] 2. Spin on thick photoresist 15.
[0040] 3. Expose through mask and develop to produce the patterned
photoresist shown in FIG. 2.
[0041] 4. Mix PDMS 10:1 ratio resin to curing agent. Mix well and
degas.
[0042] 5. Spin on or cast desired thickness of PDMS 11 onto the
patterned photoresist on the handle wafer, preferably round wafers
15 to make later processing steps easier, as shown in FIG. 3.
[0043] 6. Let PDMS settle at room temperature before curing. This
allows PDMS to separate from the photoresist.
[0044] 7. Cure PDMS 1 hr at 66.degree. C.
[0045] 8. Allow PDMS to cool.
[0046] 9. Remove remaining photoresist using acetone. This results
in patterned PDMS 11 on top of handle wafer with a partially
exposed seed layer 12 as shown in FIG. 4.
[0047] 10. Electroplate gold or platinum through the patterned PDMS
to form electrodes 12 as shown in FIG. 5.
[0048] 11. The next step is to pattern the conductive metal lines
16 on the PDMS 11 as shown in FIG. 6.
[0049] Process for Patterning Conductive Metal Lines Using Lift-Off
Process
[0050] 1. Oxidize the PDMS surface for 1 min. at 100 watts RF
power.
[0051] 2. Spin on AZ1518 Photoresist at 1000 rpm for 20 sec.
[0052] 3. Soft bake the resist at 60.degree. C. for 10 min then
bring down temperature to 45.degree. C. for 10 min and then bring
down temperature to 30.degree. C. for 10 min. (Lowering the
temperature slowly minimizes cracking in the photoresist).
[0053] 4. Expose for 15 sec. through mask.
[0054] 5. Develop in AZ developer for approximately 1 min.
[0055] 6. Deposit metal using electron-beam evaporator.
[0056] 7. Deposit 200 angstroms of titanium as the adhesion layer
at 2 angstroms/sec.
[0057] 8. Deposit 1000 angstroms of gold as the conductive metal at
2 angstroms/sec. (another metal that can be used is platinum).
[0058] 9. Deposit 200 angstroms of titanium on top of the gold to
provide an adhesion layer for the 2.sup.nd PDMS layer that will be
deposited later.
[0059] 10. Following metal deposition place in acetone to remove
excess metal through lift-off process, but do not shake or stir as
this may cause the PDMS to lift off of the substrate. Apply PDMS
around the edges of the wafer to ensure that the PDMS membrane
remains attached to the substrate.
[0060] 11. Gently rinse with acetone and isopropyl alcohol and set
on flat surface. Air dry.
[0061] 12. Oxidize PDMS surface again.
[0062] 13a. Apply 2.sup.nd layer 17 of PDMS using a stencil-like
mask. This mask must be made of a material that sticks to the PDMS
enough not to cause seepage of the PDMS under the mask, but can be
removed after either spinning or casting the PDMS without ripping
or damaging the underlying metalized PDMS membrane. An overhead
projector transparency sheet can be used for this purpose.
[0063] Cut sections from the mask in regions where the 2.sup.nd
layer of PDMS is desired. Apply the mask to the 1.sup.st layer of
PDMS.
[0064] Spin, cast, or mold PDMS over the mask.
[0065] Remove mask gently.
[0066] Cure at 66.degree. C. for 1 hr.
[0067] Step 13a is illustrated in FIG. 7.
[0068] Remove device 10 from handle wafer as shown in FIGS. 8A and
8B. 13b. A second approach for applying 2.sup.nd layer of PDMS is
by membrane transfer from UV tape, soft substrate, or flexible
wafer (examples: Polyimide or transparency)
[0069] UV tape example:
[0070] Apply UV tape onto a hard substrate using adhesive side.
[0071] Spin, cast or mold PDMS on non-adhesive side of UV tape.
[0072] Cure at 66.degree. C. for 1 hr.
[0073] Expose the UV tape with UV light.
[0074] Remove tape from hard substrate.
[0075] Oxidize both the PDMS on original wafer and on the UV
tape.
[0076] Bond PDMS on tape to PDMS on the handle wafer
[0077] Use razor blade to cut part of the PDMS from the tape
[0078] Peel back the tape slowly
[0079] PDMS that was on the tape is now bonded to PDMS on the
handle wafer (See FIG. 7.)
[0080] Remove the device from the handle wafer (See FIG. 8.)
[0081] 13c. A third approach for applying the 2.sup.nd layer of
PDMS is to partially dip coat the desired area to be encapsulated
in PDMS.
[0082] Referring now to FIG. 9, the device 10 is shown with an
encapsulated electronic chip 18 attached to the lead lines 16. The
device 10 was fabricated as illustrated in FIGS. 1 through 8. The
device 10 was fabricated by a method that produces a polymer
substrate 11 that has the ability to conform to various shapes of
tissue. An electroplating seed layer 12 is deposited onto handle
wafer 14. A patterned photoresist is produced. Polymer 15 is spun
or cast onto the patterned photoresist on the handle wafer 14. The
remaining photoresist is removed resulting in patterned PDMS 11 on
top of the handle wafer 14 with sections of the underlying seed
layer 12 exposed. Gold or platinum is electroplated through the
patterned PDMS to form electrodes 12. Conductive metal lines 16 are
patterned on the PDMS 11. A 2.sup.nd layer 17 of PDMS is applied.
The device 10 is removed from the handle wafer. In one embodiment
the device is biocompatable. In another embodiment the device is
implantable. In one embodiment the polymer is an elastomer. In
another embodiment the polymer is an elastomer that is conformable.
In another embodiment the polymer is an elastomer that is flexible
and stretchable. In another embodiment the elastomer is
poly(dimethylsiloxane). The flexible electrode array 10, shown in
FIGS. 1-9 and constructed as described above, was successfully
tested.
[0083] During implantation or use, it is possible that the
electrode array might be stretched. Thus it is important that the
device is not only flexible, but is also stretchable. Pull tests
were performed to demonstrate that the devices are flexible and
stretchable and still maintain conductivity to large strains (up to
3%). Thus, the devices will not fail when handled by the physician
for implantation, or when used in applications in which they must
deform periodically, for example if attached to the skin. Even when
the devices are stretched to the point where the conducting lines
fail, with time they regain their conductivity. This is due to the
viscoelastic nature of the PDMS. When metalizing the PDMS, there
are several factors that contribute to the ability to create robust
conducting lines. When the PDMS is spin-coated onto a substrate, it
has a built-in tensile residual stress (the PDMS wants to contract,
but is constrained by the substrate). This occurs because of the
volume change associated with curing the PDMS. When removed from
the handle wafer, the PDMS contracts and the tensile stress
relaxes. Depositing a metal film with compressive residual stress
(the film wants to expand) onto the PDMS before release from the
handle wafer results in wrinkling of the metal. The metal becomes
even more wrinkled when the PDMS contracts after release from the
handle wafer. The combination of these two effects results in metal
conductors that can be stretched without breaking after releasing
the load. Even if stretched to the point where the metal breaks,
when the load is released, the PDMS substrate contracts and the
broken conducting lines reestablish contact.
[0084] FIG. 10 illustrates another embodiment of an electrode array
of the present invention. This embodiment of the flexible electrode
array system is generally designated by the reference numeral 20.
The flexible electrode array 20 is produced by the steps
illustrated in FIGS. 1-8 and described above. The electrode array
20 utilizes a substrate 21 made of a compliant material. Electrodes
22 are embedded in the substrate 21. Conductive leads 23 are
connected to the electrodes 22 and to a ribbon cable 24. The ribbon
cable 24 includes a connector 25 for connecting the electrode array
20 to other electronics. For example, the connector 25 may be
connected to a device for transferring an image signal to tissue in
a retina. The ribbon cable 24 also could be fabricated using the
same process described above for PDMS with embedded conducting
lines. In this embodiment, the implanted electrode array and ribbon
cable form one continuous device.
[0085] Referring now to FIGS. 11A and 11B, an embodiment of a
metalized PDMS device is shown. This embodiment is designated
generally by the reference numeral 30. An upper view of the
electrode array 30 is show in FIG. 11A and a lower view is shown in
FIG. 11B. Electrodes 32 extend through the substrate 31.
[0086] The substrate 31 is compliant. In one embodiment the
substrate is composed of an elastomer and has the ability to
conform to the shape of tissue. The elastomer can be
poly(dimethylsiloxane) or PDMS.
[0087] Description of an Embodiment for Artificial Vision
[0088] One embodiment of the present invention provides an
intraocular prosthesis. This provides a system that restores vision
to people with certain types of eye disorders. An image is captured
or otherwise converted into a signal representing the image. The
signal is transmitted to the retina utilizing an implant. The
implant consists of a polymer substrate. In one embodiment the
polymer substrate is flexible and stretchable and has the ability
to conform to the shape of the retina. Electrodes are embedded in
the polymer substrate. Conductive leads are connected to the
electrodes for transmitting the signal representing the image to
the electrodes. The electrodes embedded in the polymer substrate
contact the retina and the signal representing the image stimulates
cells in the retina. In one embodiment the device for capturing a
signal representing the image is a video camera and the signal is
relayed to the electrode array via wires, or by a wireless link. In
one embodiment the electrodes include micromachined points, barbs,
hooks, and/or tacks to attach the array to the retinal tissue. In
one embodiment the polymer is liquid silicone rubber (LSR). In one
embodiment the polymer is poly(dimethylsiloxane).
[0089] FIG. 13 illustrates an intraocular prosthesis. This is an
embodiment of the present invention that provides a system that
restores vision to people with certain types of eye disorders. The
system is generally designated by the reference numeral 50. A video
camera captures an image 51. A device sends the image via cable
connection, a laser or RF signal 52 into a patient's eye 53.
Electronics 54 within the eye 53 receive the image signal 51 and
send it to the electrode array 55. The implant 54 includes an
electrode array 55 utilizing a substrate made of a compliant
material with electrodes and conductive leads embedded in the
substrate. The electrodes contact tissue of the retina. The implant
54 stimulates retinal neurons. The retinal neurons transmit a
signal to be decoded to the brain 57.
[0090] The present invention provides an artificial vision system
that can help restore vision to people left totally or partially
blind by retinal degeneration or other retinal diseases. In
retinitis pigmentosa (RP), the progression of the disease can be
slow, but eventually can lead to total blindness. However, some of
the inner nuclear layer cells and some of the ganglion cells remain
viable, and it may be possible to restore vision through
stimulation of these cells.
[0091] Even when photoreceptor cells have been lost, the retinal
cells are often still viable. Directly stimulating these cells may
restore vision to patients suffering from photoreceptor
degeneration. Localized electrical stimulation to the retina
induces light perception in patients blind from outer retinal
degenerations. Small patterns can be recognized through stimulation
with multielectrode arrays. Thus, an implanted visual prosthesis
appears promising.
[0092] Referring again to FIG. 13, the video camera captures the
image 51. The image is sent via wire, a laser or RF signal 52 into
the eye 53 to the implant 54. The implant 54 is connected to the
retina by electrodes. The implant 54 stimulates retinal neurons.
The retinal neurons transmit the signal to be decoded. The system
senses an image and stimulates the retina with a pattern of
electrical pulses based on the sensed image signal. The implanted
component 54 receives the transmitted signal, derives power from
the transmitted signal, decodes image data, and produces an
electrical stimulus pattern at the retina based on the image
data.
[0093] The implant 54 includes an electrode array of
poly(dimethylsiloxane) (PDMS, a form of silicone rubber) for the
substrate. The substrate includes embedded electrodes and
conductive leads for directly stimulating cells in the retina and
transmitting a visual image. The fact that the device is flexible
and can conform to the shape of the patient's retina is highly
advantageous. The device is stretchable, making it rugged during
handling, insertion, and use. PDMS is oxygen-permeable but absorbs
very little water, two properties that are advantageous for a
biological implant. PDMS is an example of a material that works
well for this application, but other polymers also could be
used.
[0094] The flexible, stretchable electrode arrays have many uses,
including shaped acoustic transducers, and formed biological
sensors and stimulators for interfacing with the human body. These
can be used for applications ranging from non-destructive
evaluation to sensors and stimulators for virtual reality
simulators.
[0095] The present invention provides a method for fabricating
flexible electrode arrays using PDMS (silicone) substrates. The
devices have embedded electrodes and conducting lines for
transmitting signals to cells in the eye. The fact that the devices
are flexible allows them to conform to the shape of the retina
without damaging cells.
[0096] Referring now to FIG. 12, a concept diagram illustrates the
technical approach of an electrode array 40 of the present
invention. As shown in FIG. 12, an imaging chip 46 transmits a
signal representing an image to RF control unit 44 through an RF
link 45. The RF control unit 44 is connected to an interface
contact 43. The interface contact unit 43 is connected to a
conformable PDMS substrate 42. The conformable PDMS substrate 42
has embedded microstimulator electrodes 41. The microstimulators 41
connect the implant to the retina. The electrodes 41 stimulate the
retina with a pattern of electrical pulses based on the sensed
image signal. The implant receives the transmitted signal, derives
power from the transmitted signal, decodes image data, and produces
an electrical stimulus pattern at the retina based on the image
data.
[0097] In order to realize an array of microelectrodes, several
microelectronics and micromechanical systems (MEMS) processing
approaches are applied. These technologies help enable artificial
sight. The following engineering characteristics are included in
the implantable electrode array:
[0098] 1. Platinum electrodes with photolithographically defined
features including micron-scale contacts for precision stimulation,
tailored impedance for overall systems matching requirements, and
micromachined barbs, hooks or tacks for anchoring the implant to
the retina.
[0099] 2. A flexible biocompatible electrode substrate measuring
approximately 4 mm.times.4 mm.times.0.1 mm that can be easily
inserted and positioned according to the contour of the inner
eye.
[0100] 3. An electrical interconnection array for interfacing with
a regulated current drive derived from the processed image of the
receiver chip as shown in FIG. 12. This device consists of a
micromachined conformable electrode surface hybrid-bump bonded to a
second RF control circuit that applies electrical signals derived
from the sensed image. FIG. 12 shows electrical connections through
the back of the implant. Other ways can be used to interface to the
electronics chip. For example, leads from the back of the electrode
array can connect to an array of bond pads on the same PDMS
substrate, and the electronics chip can be flip-chip bonded to the
bond pad array. The electronics chip can be embedded in the PDMS,
forming a single, integrated, implantable device.
[0101] 4. All electrical leads and circuits except the electrode
contacts will be embedded in the PDMS substrate. Thus, the PDMS
forms a biocompatible package.
[0102] Photolithographically-Defined Microelectrodes
[0103] Several groups have used MEMS fabrication approaches to
realize microelectrodes for a variety of applications including
neurostimulation. These approaches have been primarily based on the
use of photolithographically-defined silicon. While offering the
capability of precise local electrical stimulation, the inherent
brittleness of silicon as an electrode is a significant reliability
concern that necessitates the consideration of other materials
approaches, particularly in applications such as retinal implants
where microelectrode breakage could have significant medical
consequences.
[0104] Materials such as platinum, titanium, and iridium oxide can
be prepared by sputtering, electron beam evaporation, and
electroplating. An important approach described for fabricating the
above neurostimulator array lies in the use of PDMS as the starting
material substrate. The conformable nature of the PDMS material is
important in order to ensure stable and uniform mechanical contact
with retinal tissue. Technical approaches based on the use of
traditional silicon substrates are limited due to the mechanical
rigidity and fragility of silicon.
[0105] Previous experience in processing this material for other
BioMEMS applications have shown this material to be remarkably easy
to deposit, pattern, and handle. PDMS allows the mechanical
flexibility, robustness, and strechability required for placement
in full area contact according to the shape of the retina.
Attachment holes for sutures or tacks can easily be formed in the
PDMS substrate by simple spacer castings. In addition, barbs or
hooks or tacks can be formed on the surface of the PDMS using a
suitable mold, or can be made of other materials and embedded
within the PDMS.
[0106] Electrical Interfacing between the Electrode Array and
Image
[0107] Processing Chip
[0108] Electrical interconnection between the stimulation electrode
array and front-end electronics presents unique challenges in this
implantable biomedical device application. For the retinal
prosthesis application an encoded RF broadcast signal is used to
communicate an image pattern to a multiplexor. The multiplexor in
turn sets a pattern on temporal current pulses that drives the
electrode array. The main advantage of this approach lies in the
use of a short-range RF broadcast signal (.about.1 cm). This
eliminates the need for mechanical wire interconnections that are
subject to failure and present significant packaging problems. A
second RF signal applied external to the eye is used to charge
storage capacitors that ultimately deliver current to the electrode
array.
[0109] Electrode interconnections must be mechanically robust to
prevent breakage, exhibit characteristics of an ideal electrical
conductor, and provide isolation from the biological environment
within the eye. Bump bonding the integrated circuit chip onto the
microelectrode array device, then encapsulating in PDMS addresses
both of these issues. The IC chip can be directly bonded to the
back of the electrode array, with an optional interface chip, or
can be bonded to the side of the electrode array with conducting
leads delivering the signal to the electrodes.
[0110] Referring now to FIGS. 14A and 14B, embodiments of the
electrode array are illustrated that include structures for
improving the way the electrode array contacts tissue. One use of
the electrodes is targeting specific areas in the retina without
tearing or damaging the tissue or cells. The system, generally
designated by the reference numeral 60, uses a PDMS substrate 61
with embedded electrodes 62. The electrodes are micromachined to
produce points, barbs, hooks, or tacks. As shown in FIGS. 14A and
14B the surface of the electrode contains sharp points. The
microfabricated electrode arrays illustrated in FIGS. 14A and 14B
demonstrate that it is possible to obtain sharp, compliant features
63 in the PDMS 61. It is also possible to produce barbs, hooks, or
tacks on or adjacent to the electrodes using micromachining
technology.
[0111] While the invention may be susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and have been described in
detail herein. However, it should be understood that the invention
is not intended to be limited to the particular forms disclosed.
Rather, the invention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the
invention as defined by the following appended claims.
* * * * *