U.S. patent application number 10/825782 was filed with the patent office on 2006-04-06 for high density polymer-based integrated electrode array.
This patent application is currently assigned to The Regents of the University of California. Invention is credited to James Courtney Davidson, Julie K. Hamilton, Peter A. Krulevitch, Mariam N. Maghribi.
Application Number | 20060074460 10/825782 |
Document ID | / |
Family ID | 36126556 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060074460 |
Kind Code |
A1 |
Maghribi; Mariam N. ; et
al. |
April 6, 2006 |
HIGH DENSITY POLYMER-BASED INTEGRATED ELECTRODE ARRAY
Abstract
A high density polymer-based integrated electrode apparatus that
comprises a central electrode body and a multiplicity of arms
extending from the electrode body. The central electrode body and
the multiplicity of arms are comprised of a silicone material with
metal features in said silicone material that comprise electronic
circuits.
Inventors: |
Maghribi; Mariam N.;
(Livermore, CA) ; Krulevitch; Peter A.;
(Pleasanton, CA) ; Davidson; James Courtney;
(Livermore, CA) ; Hamilton; Julie K.; (Tracy,
CA) |
Correspondence
Address: |
Eddie E. Scott;Assistant Laboratory Counsel
Lawrence Livermore National Laboratory
P.O. Box 808, L-703
Livermore
CA
94551
US
|
Assignee: |
The Regents of the University of
California
|
Family ID: |
36126556 |
Appl. No.: |
10/825782 |
Filed: |
April 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60467004 |
Apr 30, 2003 |
|
|
|
Current U.S.
Class: |
607/53 |
Current CPC
Class: |
A61N 1/0541 20130101;
A61N 1/0539 20130101; A61N 1/0534 20130101; A61N 1/0543
20130101 |
Class at
Publication: |
607/053 |
International
Class: |
A61N 1/08 20060101
A61N001/08; A61N 1/04 20060101 A61N001/04 |
Goverment Interests
[0002] 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
1. A high density polymer-based integrated electrode apparatus,
comprising: a central electrode body, and a multiplicity of arms
extending from said electrode body, wherein said central electrode
body and said multiplicity of arms are comprised of a silicone
material with metal features in said silicone material that
comprise electronic circuits and wherein said arms comprise a
silicone material with 125 separate metal traces in said silicone
material.
2. The high density polymer-based integrated electrode apparatus of
claim 1 wherein said silicone material is
poly(dimethylsiloxane).
3. (canceled)
4. The high density polymer-based integrated electrode apparatus of
claim 1 wherein said arms comprise a silicone material with 1
through n separate metal traces in said silicone material.
5. (canceled)
6. The high density polymer-based integrated electrode apparatus of
claim 1 wherein said arms comprise a poly(dimethylsiloxane)
material with a multiplicity of separate metal traces in said
poly(dimethylsiloxane) material.
7. The high density polymer-based integrated electrode apparatus of
claim 1 wherein said arms comprise a poly(dimethylsiloxane)
material with 1 through n separate metal traces in said
poly(dimethylsiloxane) material.
8. The high density polymer-based integrated electrode apparatus of
claim 1 wherein said arms comprise a poly(dimethylsiloxane)
material with one hundred twenty five separate metal traces in said
poly(dimethylsiloxane) material.
9. The high density polymer-based integrated electrode apparatus of
claim 1 comprising eight separate arms made of a silicone material
and one hundred twenty five separate metal traces in said silicone
material of each of said eight separate arms.
10. The high density polymer-based integrated electrode apparatus
of claim 1 comprising eight separate arms made of a
poly(dimethylsiloxane) material and one hundred twenty five
separate metal traces in said poly(dimethylsiloxane) material of
each of said eight arms.
11. The high density polymer-based integrated electrode apparatus
of claim 1 comprising eight separate arms made of a silicone
material and one hundred twenty five separate metal traces in said
silicone material of each of said eight separate arms, said eight
separate arms and said central electrode body contained within an
area of 16 mm.sup.2.
12. The high density polymer-based integrated electrode apparatus
of claim 1 comprising eight separate arms made of a
poly(dimethylsiloxane) material and one hundred twenty five
separate metal traces in said poly(dimethylsiloxane) material of
each of said eight arms, said eight separate arms and said central
electrode body contained within an area of 16 mm.sup.2.
13. The high density polymer-based integrated electrode apparatus
of claim 1 comprising one thousand electrical circuits within an
area of 16 mm.sup.2 and contained in eight separate arms made of a
silicone material and one hundred twenty five separate metal traces
in said silicone material of each of said eight separate arms.
14. The high density polymer-based integrated electrode apparatus
of claim 1 comprising one thousand electrical circuits within an
area of 16 mm.sup.2 and contained in eight separate arms made of a
poly(dimethylsiloxane) material and one hundred twenty five
separate metal traces in said poly(dimethylsiloxane) material of
each of said eight arms.
15. The high density polymer-based integrated electrode apparatus
of claim 1 for capturing an image and transmitting the image into
an eye to a brain, the apparatus including a video camera that
captures the image and sends the image to the eye and through
separate metal traces in said arms and said central electrode body
to the brain.
16. The high density polymer-based integrated electrode apparatus
of claim 1 for capturing an image and transmitting the image into
an eye to a brain, the apparatus including a video camera that
captures the image and sends the image to the eye and through
separate metal traces in separate arms made of a
poly(dimethylsiloxane) and said central electrode body to the
brain.
17. The high density polymer-based integrated electrode apparatus
of claim 1 for capturing an image and transmitting the image into
an eye to a brain, the apparatus including a video camera that
captures the image and sends the image to the eye and through
separate metal traces in separate arms made of a
poly(dimethylsiloxane) and said central electrode body made of a
poly(dimethylsiloxane) to the brain.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 60/467,004 filed Apr. 30, 2003 and titled
"High Density Polymer-based Integrated Electrode Array." U.S.
Provisional Patent Application No. 60/467,004 filed Apr. 30, 2003
and titled "High Density Polymer-based Integrated Electrode Array"
is incorporated herein by this reference.
BACKGROUND
[0003] 1. Field of Endeavor
[0004] The present invention relates to electrode arrays and more
particularly to high density polymer-based integrated electrode
arrays.
[0005] 2. State of Technology
[0006] 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."
[0007] 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."
[0008] 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."
[0009] U.S. Pat. No. 6,324,429 for a chronically implantable
retinal prosthesis by Doug Shire, Joseph Rizzo, and John Wyatt, of
the Massachusetts Eye and Ear Infirmary Massachusetts Institute of
Technology issued Nov. 27, 2001 provides the following information,
"In the human eye, the ganglion cell layer of the retina becomes a
monolayer at a distance of 2.5-2.75 mm from the foveal center.
Since the cells are no longer stacked in this outer region, this is
the preferred location for stimulation with an epiretinal electrode
array. The feasibility of a visual prosthesis operating on such a
principle has been demonstrated by Humayun, et al. in an experiment
in which the retinas of patients with retinitis pigmentosa,
age-related macular degeneration, or similar degenerative diseases
of the eye were stimulated using bundles of insulated platinum
wire. The patients were under local anesthesia, and they described
seeing points of light which correctly corresponded with the region
of the retina in which the stimulus was applied (Humayun, M., et
al., Archiv. Ophthalmol., 114: 40-46, 1996). The form of the
stimulating device was, however, not suited for chronic
implantation. The threshold for perception was reported to be in
the range of 0.16-70 mC/cm.sup.2. This confirmed the results of
earlier experiments on animal subjects by the instant inventors and
others which indicated that strong evoked cortical potentials could
be observed when rabbit retinas were stimulated using passive
microfabricated electrode arrays similar in some respects to the
ones proposed in the current invention (Rizzo, J. F., et al., ARVO
Poster Session Abstract, Investigative Ophthalmology and Visual
Science, 37: S707, 1996; Walter, P., et al. Investigative
Ophthalmology and Visual Science, 39: S990, 1998). The instant
inventors have, with others, performed three surgical procedures
using microfabricated electrode arrays and similar in technique to
those described by Humayun and confirmed that a consistent response
to input electrical stimuli could be noted by the patient. The task
of creating a retinal implant has been addressed by Chow, in U.S.
Pat. No. 5,016,633, who proposed a subretinal implant based on a
microphotodiode array. The procedure involved in its implantation
is so biologically intrusive, however, that successful
implementation of such a device in human subjects has not been
reported. Furthermore, an entirely passive array will be rather
insensitive under normal lighting conditions, and an array powered
from outside the body by means of a direct electrical connection
will likely lead to infections and again, be so intrusive as to be
objectionable. Earlier designs of the present inventors placed all
components of the prosthesis on the retinal surface (U.S. patent
application Ser. No. 19/074,196, filed May 7, 1998, and U.S. Pat.
No. 5,800,530, both of which are incorporated herein by reference).
It became quickly apparent that the delicate retina could not
withstand the mechanical burden which was at least partially the
result of the relatively thick profile of the microelectronic
components. A later prototype included one significant change in
design--the bulky microelectronic components were moved anteriorly
within the eye, off of the retinal surface. In this configuration,
the microelectronics are held in a custom-designed intraocular
lens, and only a thin ribbon containing the microelectrodes extends
rearwardly to the retinal surface."
SUMMARY
[0010] 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.
[0011] The present invention provides a high density polymer-based
integrated electrode apparatus. The apparatus comprises a central
electrode body and a multiplicity of arms extending from the
electrode body. The central electrode body and the multiplicity of
arms are comprised of a silicone material with metal features in
said silicone material that comprise electronic circuits. The
present invention provides increased density of electrodes to meet
increased resolution requirements needed for electrical devices
such as artificial vision and hearing implants.
[0012] 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
[0013] 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.
[0014] FIG. 1 embodiment of a system constructed in accordance with
the present invention.
[0015] FIG. 2 shows one of the tabs or arms that contains the metal
traces in a substrate composed of a polymer.
[0016] FIG. 3 illustrates an embodiment showing how the metal
traces are connected through the central electrode array.
[0017] FIG. 4 illustrates another embodiment showing how the metal
traces are connected through the central electrode array.
[0018] FIG. 5 illustrates process steps for depositing lead and
electrode metal on PDMS and subsequent passivation with PDMS.
[0019] FIG. 6 illustrates a system that restores vision to people
with certain types of eye disorders.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring now to the drawings, to the following detailed
description, and to incorporated materials, detailed information
about the invention is provided including the description of
specific embodiments. 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.
[0021] Referring now to FIGS. 1, 2, and 3, an embodiment of a
system constructed in accordance with the present invention is
illustrated. The system is designated generally by the reference
numeral 100. The system 100 provides a significant number of
electrodes contained within a small area. The system 100 provides
increased density of electrodes to meet increased resolution
requirements needed for electrical devices such as artificial
vision and hearing implants. By way of example, the system 100
meets increased resolution requirements that require placing 1000
electrodes in a 4.times.4 mm area.
[0022] As illustrated in FIG. 1, a multiplicity of tabs or arms
radiate from a central electrode array 109. Tabs or arms 101
through 108 are shown in FIG. 1. The central electrode array 109
contains the conducting metallization required to energize each
individual electrode.
[0023] The individual tabs or arms contain separate metal traces
for electrical contact. As illustrated in FIG. 2, the arm 101
contains separate metal traces, 111 through n, for electrical
contact. Depending on the desired size of the individual electrodes
each tab or arm contains from one to a predetermined number of
separate metal traces.
[0024] Referring now to FIG. 3 one embodiment of a system is
illustrated wherein the metal traces are connected through the
central electrode array and contain the conducting metallization
required to energize each individual electrode. The embodiment is
designated generally by the reference numeral 300.
[0025] The system 300 provides electrodes 301 contained in a
polymer substrate 302. The substrate 302 is composed of a polymer.
The polymer has the ability to conform to various shapes of the
tissue. The polymer in the embodiment 300 is poly(dimethylsiloxane)
or PDMS. Metal traces 303 are provided for electrical connection.
The metal traces 303 in the embodiment 300 are composed of lead
metal.
[0026] The production of a substrate that can be used as the
poly(dimethylsiloxane) or PDMS substrate 302 and production of
metal traces that can be used as the metal traces 303 is described
in U.S. patent application No. 2003/0097166 by Peter Krulevitch,
Dennis L. Polla, Mariam Maghribi, and Julie Hamilton for a Flexible
Electrode Array for Artificial Vision published May 22, 2003; U.S.
patent application No. 2003/0097165 by Peter Krulevitch, Dennis L.
Polla, Mariam Maghribi, Julie Hamilton, and Mark S. Humayun for a
Flexible Electrode Array for Artificial Vision published May 22,
2003; and U.S. patent application No. 2004/0018297 by Courtney
Davidson, Peter Krulevitch, Mariam Maghribi, William Benett, Julie
Hamilton, and Armando Tovar for Conductive Inks for Metalization in
Integrated Polymer Microsystems published Jan. 29, 2004. U.S.
patent applications Nos. 2003/0097166, 2003/0097165, and
2004/0018297 are incorporated herein in their entirety by this
reference.
[0027] The system 100 has many uses. For example, the system 100
has uses for implantable, biocompatible electrode arrays;
biological, chemical, temperature, radiation sensor; sensors and
stimulators for interfacing with human body and inanimate objects;
non-destructive evaluation sensors; flexible display monitors;
smart notes; and monitoring devices. The system 100 also has uses
for implantable devices: epiretinal, subretinal, and cortical
artificial vision implant, cochlear implants, neurological
implants, spinal cord implants and other neural interface implants;
implantable electrode array devices; monitoring devices;
implantable ribbon cables and electrode array for deep brain
stimulation, spinal cord reattachment, nerve regeneration, cortical
implants, retinal implants, cochlear implants, drug delivery,
muscle stimulation and relaxation; and flexible displays and smart
notes, conformable circuits.
[0028] The system 100 provides an electrode array system with
embedded electrodes and conductive leads that can be used for
directly stimulating cells. U.S. patent applications Nos.
2003/0097165 and 2003/0097166 show electrode array systems. The
systems use a substrate with embedded electrodes and conductive
leads for directly stimulating cells. The disclosures of U.S.
patent applications Nos. 2003/0097165 and 2003/0097166 are
incorporated herein by reference.
[0029] The system 100 can provide a system that is implantable and
can be used for surgical insertion. The system 100 can also be
attached to the surface of the skin or other tissue. The system 100
can be used in other ways. Other applications of the system 100
include use as a flex circuit. The system 100 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.
[0030] OctoPDMS--One specific embodiment of the invention has been
designated "OctoPDMS." The embodiment utilizes metal features on
Poly(dimethylsiloxane) a type of silicone rubber know as PDMS. An
electrode array is contained in an octagonal base with eight tabs
or arms extending from the octagonal base. The embodiment is
produced by fabricating stretchable metal traces on PDMS
(silicone).
[0031] The OctoPDMS embodiment will be described using FIGS. 1, 2,
3, 4, and 5. As illustrated in the figures, the OctoPDMS system is
designated generally by the reference numeral 100. The OctoPDMS
system 100 provides one thousand electrodes contained within an
area of 16 mm.sup.2. The electrode array is contained in the
octagonal base 109 with eight tabs or arms 101 through 108,
containing 125 metal traces 111 through n, for electrical contact,
where n=the remaining metal traces to equal 125.
[0032] As illustrated by FIG. 2, the tab or arm 101 contains 125
metal traces 111 through n, for electrical contact, where n=the
remaining metal traces. The tab or arm 101 includes a substrate
composed of a polymer. The polymer has the ability to conform to
various shapes of the tissue. The polymer is poly(dimethylsiloxane)
or PDMS.
[0033] As illustrated by FIG. 3, the metal traces, 111 through n,
are connected through the central electrode array 109 and contain
the conducting metallization required to energize each individual
electrode.
[0034] The OctoPDMS system 100 is produced by implementing various
processing steps on a substrate. A description of a system for
manufacturing the tab or arm 101 is described in U.S. patent
applications Nos. 2003/0097165 and 2003/0097166 and the disclosures
of U.S. patent applications Nos. 2003/0097165 and 2003/0097166 are
incorporated herein by reference. A conductive material is
deposited on a handle wafer and various processing steps are taken
to complete the OctoPDMS system 100.
[0035] The OctoPDMS system 100 is produced using a number of
processing steps. The OctoPDMS system 100 provides a process for
depositing metal features on Poly(dimethylsiloxane) which is a type
of silicone rubber. With the process Applicants are capable of
fabricating stretchable metal traces on PDMS (silicone) using a
cost effective batch fabrication process. Applicants have
demonstrated selective passivation of these metal traces with PDMS
exposing the traces only in areas needed to make contact with the
outside world. The embodiment includes improvements in the process
of metalizing PDMS, selective passivation, using batch fabrication
photolithographic techniques to fabricate PDMS, and producing
stretchable metal traces that are capable of withstanding strains
of 7% with S.D. 1.
[0036] Referring now to FIG. 4 another embodiment of a system is
illustrated wherein the metal traces are connected through the
central electrode array and contain the conducting metallization
required to energize each individual electrode. The embodiment is
designated generally by the reference numeral 400.
[0037] The system 400 provides electrodes 401 contained in a
polymer substrate 402. The substrate 402 is composed of a polymer.
The polymer has the ability to conform to various shapes of the
tissue. The polymer in the embodiment 400 is poly(dimethylsiloxane)
or PDMS. Metal traces 403 are provided for electrical connection.
The metal traces 403 in the embodiment 400 are composed of lead
metal.
[0038] Referring now to FIG. 5, the basic process steps for
depositing lead and electrode metal on PDMS and subsequent
passivation with PDMS is illustrated. The process is designated
generally by the reference numeral 500. The system 500 includes the
steps of casting 501, spin 502, metallization 503, spin coating
504, and release 505. Applicants approach is to use PDMS as the
substrate material to batch produces a low-cost device that is
ready for implantation without the need for additional packaging
steps. Because PDMS has not previously been used in this type of
micromachining application, applicants developed new fabrication
processes enabling PDMS patterning, metalization, and selective
passivation. The metal features are embedded (deposited) within a
thin substrate fabricated using poly(dimethylsiloxane) (PDMS), an
inert biocompatible elastomeric material that has simultaneously
low water and high oxygen permeability. The conformable nature of
PDMS is critical for ensuring uniform contact with the curved
surfaces.
[0039] PDMS is a form of silicone rubber, a material that is used
in many implants and has been demonstrated to withstand the body's
chemical and physical conditions without causing adverse side
effects and is a favorable material to implant within the body.
Robustness of the metalized PDMS is another important design
criterion that applicants considered, as stretching and bending
occur during fabrication and implantation of the device. The PDMS
metalization process was demonstrated to produce devices that will
be sufficiently rugged for implantation, with a demonstrated strain
to failure of 7%, (SD=1). Applicants attribute the stretchability
to a tensile residual stress from curing the PDMS.
[0040] In one of the initial steps, silicone is spun onto a silicon
handle wafer. The silicone is poly(dimethylsiloxane) known as PDMS.
PDMS has very low water permeability and protects the electronic
components from the environment. PDMS is flexible and will conform
to curved surfaces. It is transparent, stretchable, resinous,
rubbery, stable in high temperatures and provides numerous
applications for the electronic devices produced by the method
300.
[0041] The silicon handle wafer provides a temporary base for
production of the electronic device. Silicon wafers are convenient
for the handle material because they are flat, stable, routinely
used in microfabrication applications, and they are readily
available. However, other materials such as glass, plastic, or
ceramic could be used as well. The electronic devices will
eventually need to be removed from the handle wafer. Since the
flexible polymer layer would become permanently bonded to the
surface of the silicon handle wafer, a non-stick layer is first
provided on the silicon handle wafer. The step comprises the
deposition of gold (or platinum) onto the handle wafer. This allows
for removal of the PDMS from the substrate after processing. The
gold film facilitates removal of the polymer membrane from the
wafer after completion of the fabrication process. Needed areas on
the silicon wafer is left without the gold coating to prevent the
PDMS membrane from lifting off during processing for example a 2 mm
wide ring a the edge is left uncoated with gold. PDMS is then spun
onto the wafer at a desired thickness and cured. For example the
PDMS may be cured at 66.degree. C. for 24-48 hours (or at
manufactures' specifications). It is to be understood that the step
301 could be omitted if the surface on which the PDMS layer is
deposited is such that the PDMS will not become bonded.
[0042] In a subsequent step 303 the process of forming the
electrical circuit lines and the central electrode array of the
OctoPDMS system 100 is initiated. A photoresist (AZ.RTM.1518,
Clariant) is spun onto the PDMS membrane surface at 1000 rpm for 20
seconds and baked at 60.degree. C. for 45 minutes. The temperature
is brought down slowly (30 min. to ramp temperature down) to room
temperature to avoid cracking in the photoresist. Prior to
photoresist application, the wafer is placed in an oxygen plasma to
activate the surface. This allows the resist to wet the PDMS
surface preventing beading and ensuring the formation of a smooth
and uniform coat of photoresist on the polymer surface. The
substrate is placed flowing at 300 sccm. The photoresist features
are then UV exposed at 279 mJ and developed in AZ developer mixed
1:1 with water for 70 sec. Then the wafer is rinsed under a gentle
stream of water and dried using N2. The wafer is placed for a
second time in the oxygen plasma to activate the newly exposed PDMS
surface, and promote adhesion of the metal, which is deposited in
the next step.
[0043] In the next step a 150 nm gold film is e-beam evaporated
onto the wafer using titanium as the adhesion layer. The e-beam
needs to be sufficiently cooled down before removing the parts.
Cool down is conducted for 10 min. under vacuum and for 20 min.
with the system vented, but not open. The metal adheres to the PDMS
surface in regions where the photoresist was removed, and the
excess metal is removed through a lift-off process by placing the
wafer in acetone. The wafer is then prepared for the next step by
rinsing with ethanol and drying gently. If the PDMS surface is
contaminated or aged, it can be refreshed by soaking in a 20%
solution of HCl for 8 min.
[0044] In the next steps the process of forming the vias through a
passivating layer of PDMS to connect the electrical circuit lines
to the electronic components of the OctoPDMS system 100 is
initiated. A thick photoresist is spun onto the PDMS membrane
surface. The photoresist is patterned by exposing the resist to UV
through a photomask and developing. The passivating layer of
silicone is spun onto the wafer, over the patterned photoresist.
The surface is gently swabbed to remove excess PDMS from the top of
the photoresist features before stripping the resist. This ensures
the removal of the photoresist and the complete clearance of the
vias. To strip the resist the wafer is soaked in acetone for 15
min. and then soaked in isoproponol for 5 min. and then rinsed with
isoproponol and dried.
[0045] Another way of patterning and passivating the PDMS is using
a shadow-mask, which is a stencil-like mask exposing the areas that
need to be passivated or patterned. A third way of passivating the
PDMS is by protecting the areas needed for electrical connection
and dipping the wafer in PDMS and curing.
[0046] In the next step conductive material is applied to the vias.
The vias can be filled with electroplating, conductive silicone
adhesive, conductive ink or solder paste. An automated dispenser or
applicator machine is used to deposit precise amounts of material
in the vias locations. Alternatively, the conductive material can
be screen-printed using conductive inks, or liquid ink can be
injected into channels formed in the first PDMS layer. As another
option, metal can be electroplated in the PDMS vias to form an
array of electrical contacts.
[0047] In the next step, the surface of the second PDMS layer is
rinsed with ethanol and exposed to an oxygen plasma. This activates
the surface in preparation for bonding the electronic components to
the PDMS. The following step is performed in a nitrogen environment
in order to extend the lifetime of the activated surface.
[0048] Referring now to FIG. 6, an embodiment of a system
constructed in accordance with the present invention is
illustrated. The system is designated generally by the reference
numeral 600.
[0049] The system 600 provides a system that restores vision to
people with certain types of eye disorders. The system 600 includes
a video camera 608 that captures an image 609. A device sends the
image via a cable connection, a laser or RF signal into a patient's
eye 604. Electronics 601 within the eye 604 receives the image 609
signal and send it to the electrode array 601. The electrode array
601 utilizing a substrate made of a compliant material with
electrodes and conductive leads embedded in a substrate. The
electrodes contact tissue of the retina. The implant 601 stimulates
retinal neurons. The retinal neurons transmit a signal to the brain
605.
[0050] The system 600 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 visual
cortex 606 and some of the optic nerve cells 607 remain viable, and
it may be possible to restore vision through stimulation of these
cells.
[0051] Referring again to FIG. 6, the video camera 608 captures the
image 609. The image is sent via wire, a laser or RF signal 52 into
the eye 604 to the implant 610. The implant 610 is connected to the
retina by electrodes 601. The implant 610 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.
[0052] The implant 610 includes the electrode array 601 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.
[0053] The flexible, stretchable electrode array 601 has 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. The engineering characteristics described below are
included in the implantable electrode array 601.
[0054] Platinum electrodes with photolithographically defined
features including micron-scale contacts for precision stimulation,
tailored impedance for overall systems matching requirements.
[0055] A flexible biocompatible electrode substrate that can be
easily inserted and positioned according to the contour of the
inner eye.
[0056] An electrical interconnection array for interfacing with a
regulated current drive derived from the processed image of the
receiver chip. This 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. The
electronics chip can be embedded in the PDMS, forming a single,
integrated, implantable device.
[0057] All electrical leads and circuits except the electrode
contacts will be embedded in the PDMS substrate. Thus, the PDMS
forms a biocompatible package. Another approach is to attach the
PDMS electrode array to a hermetically sealed electronics
package.
[0058] 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.
[0059] 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 stretchability 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.
[0060] 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.
[0061] Electrode interconnections are 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.
[0062] The base will lie against the retina while the arms conform
to the curvature of the eye and converge onto an IC chip in the
region where the lens usually resides.
[0063] The final implant specifications calls for a device with
approximately a 1000 electrodes contained within an area of 16
mm.sup.2. The electrode array is contained in the octagonal base
with eight arms containing 125 metal traces for electrical
contact.
[0064] The central portion of the device contains an arbitrary
number of electrodes. The tabs radiating from the central electrode
array contain the conducting metallization required to energize
each electrode. Depending on the size of the individual electrodes
each tab may contain from one to an arbitrary number. (While this
describes eight connections to the array it is easy to extend this
approach to an arbitrary number of connectors, each containing an
arbitrary number of conductors.)
[0065] Long-term biocompatibility studies are currently being
performed to ensure life long durable implants. The main obstacle
to the implantation will be the maintenance of the implant inside
the body. It is prerequisite that the implant remains viable and
biocompatible for the entire life of the recipient.
[0066] The medical purpose of the retinal implant is strictly to
give enough sight to the blind in order to make their lives more
self-sufficient. Researchers are exploring and have yet to discover
methods to provide depth perception, color, and contrast to the
images created by the implant. A grand challenge still exists to
develop an implant capable of providing complete natural vision.
However the great success of the cochlear implant is proof that a
neural implant can make a significant impact despite its simplicity
in comparison to natural biologicai system. There is no doubt that
an implantable retina will have a significant impact on our society
as it helps to alleviate some forms of blindness. Providing sight
to the visually impaired through retinal prosthesis will be a
phenomenal application of polymer-based microtechnology.
[0067] 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.
* * * * *