U.S. patent application number 11/801839 was filed with the patent office on 2007-11-01 for process for manufacturing electronically conductive components.
Invention is credited to Dusan Milojevic, John Parker.
Application Number | 20070251082 11/801839 |
Document ID | / |
Family ID | 25646676 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251082 |
Kind Code |
A1 |
Milojevic; Dusan ; et
al. |
November 1, 2007 |
Process for manufacturing electronically conductive components
Abstract
A method of forming a device, such as an electrode array for a
cochlear implant. The method comprises a step of forming a
predetermined pattern of relatively electrically conductive regions
and relatively electrically resistive regions in a sheet of
biocompatible electrically conductive material, such as platinum
foil. The method can comprise a step of working on the sheet to
remove predetermined portions therefrom to form the one or more
discrete relatively conducting regions. The step of working on the
sheet can comprise embossing the sheet, cutting or slicing the
sheet, or using electrical discharge machining (EDM) to remove
unwanted portions of the sheet, the EDM equipment having a cutting
tool comprising an electrode.
Inventors: |
Milojevic; Dusan;
(Westleigh, AU) ; Parker; John; (Roseville,
AU) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
PO BOX 7068
PASADENA
CA
91109-7068
US
|
Family ID: |
25646676 |
Appl. No.: |
11/801839 |
Filed: |
May 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10477434 |
Nov 7, 2003 |
7240416 |
|
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PCT/AU02/00575 |
May 7, 2002 |
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11801839 |
May 11, 2007 |
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Current U.S.
Class: |
29/594 ; 29/593;
29/609.1 |
Current CPC
Class: |
Y10T 29/49151 20150115;
Y10T 29/49128 20150115; Y10T 29/49004 20150115; Y10T 29/49529
20150115; Y10T 29/49176 20150115; Y10T 29/49155 20150115; Y10T
29/49002 20150115; A61N 1/0541 20130101; Y10T 29/49476 20150115;
Y10T 29/49005 20150115; Y10T 29/4908 20150115 |
Class at
Publication: |
029/594 ;
029/593; 029/609.1 |
International
Class: |
H04R 31/00 20060101
H04R031/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2001 |
AU |
PR 4818 |
Apr 23, 2002 |
AU |
PS 1924 |
Claims
1. A method of forming a device comprised of a predetermined
pattern of relatively electrically conductive regions and
relatively electrically resistive regions, the method comprising a
step of: working a sheet of electrically conductive material to
remove predetermined portions therefrom to form said one or more
discrete relatively conducting regions; wherein the step of working
the sheet includes a step of pressing a sheet of electrically
conductive material to form a predetermined pattern of raised
portions therein; and wherein one or more of those portions of the
sheet not raised during the pressing step are removed to leave a
remaining portion having a predetermined pattern.
2. A method of forming a device comprised of a predetermined
pattern of relatively electrically conductive regions and
relatively electrically resistive regions, the method comprising a
step of: working a sheet of electrically conductive material to
remove predetermined portions therefrom to form said one or more
discrete relatively conducting regions; wherein the step of working
the sheet includes a step of pressing a sheet of electrically
conductive material to form a predetermined pattern of raised
portions therein; and wherein at least some of the raised portions
and at least some of the unraised portion are removed to leave a
remaining portion having a predetermined pattern.
3. A method of forming a device comprised of a predetermined
pattern of relatively electrically conductive regions and
relatively electrically resistive regions, the method comprising
the steps of: (i) coating at least a first surface of an
electrically conductive material with a first layer of another
material that is relatively electrically insulating; (ii) forming a
predetermined pattern in the sheet of electrically conductive
material by removing portions of the sheet therefrom such that at
least the pattern of electrically conductive regions remain; and
(iii) coating a second surface of the sheet of electrically
conductive material with a layer of resiliently flexible material;
wherein the first layer comprises a polymeric material selected
from the group comprising a polycarbonate, polytetrafluoroethylene,
polyimide, PAA, and PVA; and wherein the device is a component of
an implantable tissue-stimulating device.
4. A device of claim 3 wherein the tissue-stimulating device is an
intracochlear electrode assembly.
5. An electrode array for use in a tissue stimulating or recording
device, the electrode array comprising a plurality of stimulating
or recording pads, each stimulating or recording pad having at
least one electrical conduction means extending away therefrom, the
stimulating or recording pads and electrical conduction means
formed from a worked sheet of electrically conducting material.
6. The electrode array of claim 5 wherein the sheet is a sheet of
platinum.
7. The electrode array of claim 5 wherein the stimulating pads and
at least a portion of the electrical conduction means are housed
within an elongate biocompatible carrier.
8. The electrode array of claim 7 wherein the sheet of platinum has
a thickness no greater than about 50 microns.
9. The electrode array of claim 8 wherein the sheet of platinum has
a thickness no greater than about 20 microns.
10. The electrode array of claim 5 wherein each electrode has an
areal dimension of less than about 0.5 mm.sup.2.
11. The electrode array of claim 5 wherein the sheet has a
dimension of about 50 mm.times.250 mm.
12. The electrode array of claim 11 wherein more than one electrode
array is formed from a single sheet of platinum.
13. The electrode array of claim 5 wherein the electrical
conduction means have a width of between about 1 and 100 microns,
more preferably between about 1 and 70 microns.
14. The electrode array of claim 13 wherein each electrical
conduction means is electrically insulated from its neighbour, the
spacing between neighbouring wires being between about 10 and 100
microns.
15. The electrode array of claim 5 wherein the array is formed by
pressing the sheet of electrically conductive material to form
raised and unraised portions and then removing the raised or
unraised portions to leave a remaining portion having a
predetermined pattern of electrically conductive and electrically
resistive regions.
16. The electrode array of claim 5 wherein the array is formed by
machining the sheet of electrically conductive material to remove a
portion therefrom such that at least a pattern of electrically
conductive regions remains.
17. The electrode array of claim 16 wherein the machining of the
sheet comprises a step of using electrical discharge machining
(EDM) to remove unwanted portions of the sheet.
18. A device having an electrically conductive component, the
component being formed from a worked sheet of electrically
conducting material, the sheet having a thickness less than about
50 microns.
19. The device of claim 18 wherein the sheet is a platinum
foil.
20. The device of claim 19 wherein the platinum foil has a
thickness no greater than about 20 microns.
21. The device of claim 19 wherein the sheet has a dimension of
about 50 mm.times.250 mm.
22. The device of claim 18 wherein the electrically conductive
component comprises at least one conductive wire formed from the
platinum foil, the wire having a width of between about 1 and 100
microns, more preferably between about 1 and 70 microns.
23. The device of claim 22 wherein the electrically conductive
component comprises a plurality of discrete conductive wires formed
from the platinum foil, each wire being electrically insulated from
its neighbouring wire.
24. The device of claim 23 wherein the spacing between neighbouring
wires is between about 10 and 100 microns.
25. The device of claim 24 wherein the wires are disposed for at
least a portion of their lengths in a parallel arrangement.
26. The device of claim 21 wherein the conductive wire extends from
an electrode also formed from the platinum foil, the electrode
having an areal dimension of less than about 0.5 mm.sub.2.
27. The device of claim 18 wherein the device is a component of a
tissue stimulating device.
28. The device of claim 27 wherein the tissue stimulating device is
an intracochlear electrode assembly.
29. The device of claim 18 wherein the device is a component of a
biosensor.
30. The device of claim 18 wherein the device is a miniature
wire.
31. The device of claim 18 wherein the component is formed by
machining the sheet of electrically conductive material to remove a
portion therefrom such that at least a pattern of electrically
conductive regions remains.
32. The device of claim 31 wherein the machining of the sheet
comprises a step of using electrical discharge machining (EDM) to
remove unwanted portions of the sheet.
33. A method of forming a device comprised of a predetermined
pattern of relatively electrically conductive regions and
relatively electrically resistive regions, the method comprising
the steps of: (i) mounting a sheet of electrically conductive
material in an electrical discharge machining (EDM) device, the
device having a discharge electrode of a predetermined shape; (ii)
programming the EDM device to bring the electrode adjacent the
sheet; and (iii) operating the EDM device to remove a portion of
the sheet corresponding to the shape of the electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/477,434 filed on Nov. 7, 2003 which is a National Phase
Patent Application of International Application Number
PCT/AU02/00575, filed on May 7, 2002, which claims priority of
Australian Patent Application Number PR 4818, filed on May 7, 2001,
and Australian Patent Application Number PS 1924, filed on Apr. 23,
2002.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of forming
miniature wiring and connector systems for electrical products.
More specifically the present invention relates to a method of
forming electrode arrays, such as arrays for sensors, including
biosensors, and implantable devices, such as an implantable
recording or stimulating electrode or pad for use in the body. An
electrode array formed using the method is also described.
BACKGROUND OF THE INVENTION
[0003] In many electrical devices, particularly those that are
manufactured on a very small scale, the manufacture of the wiring
and connector components is often a labour intensive and
specialised craft. Ensuring that the wiring and connection of the
various components of the systems occurs correctly is often the
most expensive and labour intensive aspect of the manufacturing
process, resulting in large costs associated with the time taken to
manufacture the device which is often passed on to the ultimate
consumer. This is also the case when such devices need to be
specifically hand made to a specification as often the availability
of the device is dependant upon the time taken to manufacture the
device, with the time taken being difficult or impossible to
expedite.
[0004] This is particularly the case in the field of medical
implants and electrical devices that are implanted in the body to
perform a specific task. Such devices may include: stimulating
devices such as pacemakers, cochlear implants, FES stimulators;
recording devices such as neural activity sensors and the like;
implantable cables which may be used to connect implantable devices
to other implantable devices or stimulating/sensing devices;
diagnostic devices capable of carrying out in-vivo analysis of body
parameters; and other types of implantable devices not yet
contemplated. In such devices, the size needs to be minimised to
ensure that they are minimally invasive upon implantation. As a
result, in such instances, the electronic wiring and connections
need also to be relatively very small. As such, manufacturing such
devices to ensure that they are reliable and sturdy is a
specialised art, and requires much time and expense.
[0005] As a result of the need to increase the miniaturisation of
such devices, a wide range of techniques have been developed to
create patterned components which would be too difficult or
impossible to create by hand design and satisfy the high volume
supply required. Techniques such as electroforming, vacuum
deposition (sputtering, evaporation), and chemical vapour
deposition, to name a few, are some of the known ways to produce
patterned electrically conductive features on insulating surfaces
on a micron scale. The problem with such methods however, has been
that the metallic films produced by these techniques have been
shown to feature properties that are different from the
corresponding properties of the bulk materials used. This results
in the desired materials functioning differently from their
intended purpose, and in the particular case of platinum, the thin
films have tended to crack and exhibit large impedance as well as a
high degree of delamination.
[0006] In the manufacture of such devices, the bulk material is
chosen based on the properties it exhibits. In the case of
implantable electrical components, platinum has been found to
exhibit particularly useful properties for such an application,
namely good conductivity and inertness. With this being understood,
it is beneficial in the manufacture of such devices for the bulk
material to exhibit the same properties, especially physical
properties, after manufacture as it did prior to manufacture, as
discussed above. Variations in these properties can have a bearing
on the functionality of the device, which, particularly in medical
implanted devices, is highly undesirable. As mentioned, platinum
films tend to crack and delaminate, hence delivering high impedance
which impairs the functionality of the device. The use of thin film
technology has been shown to work for a number of materials such as
copper, gold and nickel, however none of these materials are
suitable for active implantable devices.
[0007] Other more conventional methods of manufacturing such
devices would be to directly stamp the desired components out of a
conductive sheet using a fine blanking or stamping method. This is
possible for applications whereby single components having large
dimensions are stamped and the components do not need to be thin
and flexible. However, simple stamping techniques are not suitable
for multiple components having very small dimensions made out of
thin conductive sheets, such as those proposed to be covered by the
present invention. In such applications, the line width dimensions
of the components and between the components are too small for
stamping machines and the sheet material is too thin to provide the
precision required for such components.
[0008] Because of these problems, medical implants, such as
cochlear implants, are still manufactured using labour intensive
manual procedures.
[0009] Hearing loss, which may be due to many different causes, is
generally of two types, conductive and sensorineural. In some
cases, a person may have hearing loss of both types. Of these
types, conductive hearing loss occurs where the normal mechanical
pathways for sound to reach the hair cells in the cochlea are
impeded, for example, by damage to the ossicles. Conductive hearing
loss may often be helped by use of conventional hearing aids, which
amplify sound so that acoustic information does reach the cochlea
and the hair cells.
[0010] In many people who are profoundly deaf, however, the reason
for their deafness is sensorineural hearing loss. This type of
hearing loss is due to the absence of, or destruction of, the hair
cells in the cochlea which transduce acoustic signals into nerve
impulses. These people are thus unable to derive suitable benefit
from conventional hearing aid systems, no matter how loud the
acoustic stimulus is made, because there is damage to or absence of
the mechanism for nerve impulses to be generated from sound in the
normal manner.
[0011] It is for this purpose that cochlear implant systems have
been developed. Such systems bypass the hair cells in the cochlea
and directly deliver electrical stimulation to the auditory nerve
fibres, thereby allowing the brain to perceive a hearing sensation
resembling the natural hearing sensation normally delivered to the
auditory nerve. U.S. Pat. No. 4,532,930, the contents of which are
incorporated herein by reference, provides a description of one
type of traditional cochlear implant system.
[0012] Typically, cochlear implant systems have consisted of
essentially two components, an external component commonly referred
to as a processor unit and an internal implanted component commonly
referred to as a receiver/stimulator unit. Traditionally, both of
these components have cooperated together to provide the sound
sensation to a user.
[0013] The external component has traditionally consisted of a
microphone for detecting sounds, such as speech and environmental
sounds, a speech processor that converts speech into a coded
signal, a power source such as a battery, and an external
transmitter coil.
[0014] The coded signal output by the sound processor is
transmitted transcutaneously to the implanted receiver/stimulator
unit situated within a recess of the temporal bone of the user.
This transcutaneous transmission occurs via the external
transmitter coil that is positioned to communicate with an
implanted receiver coil provided with the receiver/stimulator unit.
This communication serves two essential purposes, firstly to
transcutaneously transmit the coded sound signal and secondly to
provide power to the implanted receiver/stimulator unit.
Conventionally, this link has been in the form of a radio frequency
(RF) link, but other such links have been proposed and implemented
with varying degrees of success.
[0015] The implanted receiver/stimulator unit traditionally
includes a receiver coil that receives the coded signal and power
from the external processor component, and a stimulator that
processes the coded signal and outputs a stimulation signal to an
intracochlea electrode assembly which applies the electrical
stimulation directly to the auditory nerve producing a hearing
sensation corresponding to the original detected sound.
[0016] It is known in the art that the cochlea is tonotopically
mapped. In other words, the cochlea can be partitioned into
regions, with each region being responsive to signals in a
particular frequency range. This property of the cochlea is
exploited by providing the electrode assembly with an array of
electrodes or stimulating pads, each electrode or pad being
arranged and constructed to deliver a stimulating signal within a
preselected frequency range to the appropriate cochlea region. The
electrical currents and electric fields from each electrode or pad
stimulate the nerves disposed on the modiolus of the cochlea. As
the size of the cochlea is very small and the electrode assembly
needs to be flexible enough to be inserted into the cochlea, the
dimensions of the electrode assembly are such that do not allow for
traditional manufacturing techniques.
[0017] For this reason, the intracochlear electrode array has
generally been formed in a manual process by positioning a
plurality (eg. 22) of electrically conductive platinum rings in a
linear array and then welding electrical conductive wires to each
of the electrodes or pads. This process can lead to small
variations in the locations of the electrodes or pads and wiring
from one manufactured array to the next with consequent small
variations in the overall mechanical properties of the array once a
resiliently flexible carrier member is moulded about the array.
Each of the wires require connection to the receiver/stimulator
unit and in order to ensure system integrity, each of the wires
have been insulated from the others so that unwanted interaction
between different electrical components is eliminated.
[0018] While the above method has proven very successful, it is
labour intensive and hence a relatively expensive process. With
implanted devices and miniaturisation becoming more common, there
is an increasing need to provide electronic wiring and electronic
connections in such systems that are both simple and reliable. The
present invention is directed to a new method of forming such
wiring and connections that addresses at least some of the problems
with prior art processes.
[0019] Any discussion of documents, acts, materials, devices,
articles or the like which has been included in the present
specification is solely for the purpose of providing a context for
the present invention. It is not to be taken as an admission that
any or all of these matters form part of the prior art base or were
common general knowledge in the field relevant to the present
invention as it existed before the priority date of each claim of
this application.
SUMMARY OF THE INVENTION
[0020] Throughout this specification the word "comprise", or
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated element, integer or step, or
group of elements, integers or steps, but not the exclusion of any
other element, integer or step, or group of elements, integers or
steps.
[0021] The present invention enables the manufacture of a
multiplicity of components, where position of the individual
components with respect to each other is predetermined and kept
constant throughout the process, including the assembled final
product. This is achieved without the use of traditional methods
such as fine blanking and thin film technology/photolithography.
The present invention relates to a method of manufacture of
patterned features in the domain of microtechnology, wherein the
properties of the chosen bulk metal are maintained throughout the
manufacture of the device. The present invention also resides in a
multilayered assembly and the method of assembly of the
multilayered assembly.
[0022] The present application is directed to a method of forming
electrical components for an electrical device. The method provides
an advantage over the prior art in that it enables multiple
electrical components to be formed in a simple and efficient
manner, using materials and dimensions not possible with
traditional mass production forming methods. The invention uses a
sheet of material whose properties do not allow stamping out line
widths as narrow as are required in the final assembly and allows
multiple miniature components to be formed in very close proximity
of dimensions not achievable through traditional stamping
processes.
[0023] In a preferred embodiment, the present application is
directed to a method of forming an electrode array for an electrode
assembly. The method has potential advantages in providing a more
efficient and inexpensive process of electrode assembly
manufacture, particularly assembly of intracochlea electrode
assemblies. The present invention further provides a method of
forming an electrode array for an electrode assembly that
preferably allows the manufacturing process to become automated or
semi-automated so providing a desirable alternative to current
manufacturing processes which require extensive labour input and
increased manufacturing throughput.
[0024] In a first aspect, the present invention is a method of
forming a device comprised of a predetermined pattern of relatively
electrically conductive regions and relatively electrically
resistive regions, the method comprising a step of:
[0025] (a) working a sheet of electrically conductive material to
remove predetermined portions therefrom to form said one or more
discrete relatively conducting regions, wherein said sheet of
electrically conductive material has a thickness no greater than
about 100 microns.
[0026] In this aspect, the step of working the sheet can include a
step of pressing a sheet of electrically conductive material to
form a predetermined raised pattern therein. One or more of the
raised portions of the sheet can then, preferably, be removed to
leave a remaining portion having a predetermined pattern. In
another embodiment, those portions of the sheet not raised during
the pressing step can be removed to leave a remaining portion
having a predetermined pattern. In a still further embodiment, at
least some of the raised pattern and at least some of the unraised
portion can be removed to leave a remaining portion having a
predetermined pattern.
[0027] Still further, the step of working the sheet can include a
step of punching portions out of the sheet of electrically
conductive material. In this embodiment, portions of the sheet are
removed and separated from the sheet.
[0028] Yet further, the step of working the sheet can include a
step of slicing or cutting the sheet of electrically conductive
material.
[0029] In one embodiment, the remaining portion formed by the
method can be used as an electrode array or a portion thereof. For
example, the method can be used to form a layered component of an
electrode array. The electrode array can comprise a plurality of
stimulating pads or electrodes.
[0030] In yet another embodiment, the method can comprise an
additional step of placing said remaining portion on a flexible
carrier. Still further, the method can comprise the step of placing
a plurality of said remaining portions on a flexible carrier to
form an electrode array. In this embodiment, the plurality of
remaining portions can be adapted to be formed into a layered
configuration to form one or more electrode arrays.
[0031] In a preferred embodiment, the electrode array is for use as
an implantable tissue-stimulating device. More preferably, the
tissue-stimulating device is a cochlear electrode assembly, more
preferably an intracochlear electrode assembly. In another
embodiment, the electrode array could be used in a biosensor not
necessarily related to an implanted device.
[0032] In one embodiment, the sheet of electrically conductive
material is a biocompatible material. In a preferred embodiment,
the sheet is a metallic material. Still further, the metallic
material is a sheet of platinum. In a further embodiment, the sheet
can be annealed. In a further embodiment, the electrode array is
formed from a single sheet of electrically conductive material,
such as platinum. In a further embodiment, more than one array can
be formed from a single sheet of platinum. In yet a further
embodiment the sheet could be a laminate of two or more layers (eg
Pt & Ir), or could be an alloy.
[0033] The sheet preferably has a thickness between about 1 and 100
microns, more preferably between about 10 and 50 microns. The
method preferably uses a sheet of platinum having a thickness no
greater than 50 microns, more preferably no greater than 20
microns. Other suitable thicknesses can be envisaged. Each sheet
can have dimensions of about 50 mm.times.250 mm. The size of the
sheet will though depend on the requirements of the tooling used to
work the sheet. As such, sheets of different dimensions can be
envisaged. Generally it has been found that traditional stamping
techniques have proven difficult to perform with the required
accuracy upon sheets of material less than 50 microns, where the
presence of a shear lip is a problem.
[0034] Still further, a plurality of electrically conducting
connecting means can extend away from the stimulating pads of the
electrode array. Each stimulating pad of the electrode array
preferably has at least one connecting means extending away
therefrom. More than one connecting means can extend from some or
all of the stimulating pads in the electrode array.
[0035] The connecting means are preferably linearly aligned for a
majority of their length extending away from the electrode array.
In one embodiment, the connecting means can be disposed for at
least a portion of their lengths in a parallel arrangement. Where
the electrode array is formed from a single sheet, the plurality of
connecting means are also preferably formed from that sheet and are
integrally connected to respective electrodes in the array.
[0036] The sheet of conductive material can before the working step
be a planar sheet. Sheets that already have folds or embossments
formed therein prior to the working step of the present invention
can, however, also be envisaged.
[0037] In producing an electrode array, it is firstly desirable to
determine the configuration of the stimulating pads desired for the
electrode array. Once the configuration is determined, the step of
working the sheet can comprise using an embossing tool that is
fabricated for use in the method so as to produce the desired
electrode array configuration. Details of one possible type of
embossing tool will be provided in more detail below.
[0038] In a preferred process, a planar sheet is placed relative to
an embossing tool in a pressing means. The pressing means can be
programmable to press a predetermined pattern in the sheet. Where
the embossing tool is horizontally or substantially horizontally
aligned, the planar sheet can be placed relatively above the
embossing tool or relatively below the embossing tool. Where the
embossing tool is vertically or substantially vertically aligned,
the planar sheet can also be disposed in a vertical or
substantially vertical alignment beside the embossing tool.
[0039] In one embodiment, the planar sheet can be moved relative to
the embossing means and the pressing means and so be brought into
position within the pressing means. In another embodiment, the
embossing means and/or the pressing means can be moved relative to
the planar sheet to relatively bring the planar sheet within the
pressing means. In one embodiment, the process can be a continuous
process, wherein a continuous sheet is fed through the pressing
means.
[0040] The pressing means can include any medium having suitable
properties to press the sheet of material and form the raised
pattern therein. In one embodiment, the pressing means can be
formed of a material with relatively low compressibility, such as a
liquid, or gel having a relatively high content of liquid whilst
retaining sufficient fluidity to occupy the available space. In
another embodiment, compressed gas can be used to press the planar
sheet against the embossing tool.
[0041] In one embodiment, the raised pattern is formed by a single
pressing of the sheet. In another embodiment, the raised pattern
can be formed by two or more pressings of the sheet. Where the
raised pattern is formed by two or more pressings, the second or
greater pressing of the sheet can be performed by the same
embossing tool or a different embossing tool to that used for the
first pressing. Where there are two or more pressings, the sheet
may remain stationary between pressings or be relatively moved to a
new press for each pressing of the sheet.
[0042] In a preferred embodiment, the pressing means used in the
method has at least one relatively movable platen. The relatively
movable platen preferably moves relative to a stationary platen.
The embossing tool is preferably mounted to the stationary platen
of the press.
[0043] Where the platens are horizontally disposed, the lower
platen is preferably stationary and the upper platen preferably
moves downwardly and upwardly relative to this stationary platen.
In this embodiment, the embossing tool is preferably placed on the
lower platen.
[0044] In one embodiment of the method, the sheet is placed above
and on the embossing tool. A layer of backing material is then
placed on top of the sheet before operation of the press. The layer
of backing material can comprise a layer of a resiliently flexible
polymeric or elastomeric material. The backing material can
comprise a sheet of silicone or rubber and in another embodiment
the backing material can be used as an integral part of the device.
In a situation where the backing material is used as an integral
part of the electrode array, the backing material must be suitable
for implantation purposes, eg silicone.
[0045] In another embodiment, a lubricant can be used to improve
the quality of embossed pattern. The lubricant is preferably
suitable for an implant to avoid the cleaning step. Ethanol could
be a suitable lubricant since it evaporates quickly and is in fact
used as a washing agent in the assembly of implantable devices. A
thin layer of the lubricant can be present between the embossing
tool and the foil, and between the foil and the backing, or
preferably both.
[0046] The pressing means can preferably apply differing levels of
pressure to the sheet of the electrically conducting material
placed on the embossing tool. For example, the pressing means can
apply an initial pressure for a first predetermined period of time
and then apply a second different pressure for a further
predetermined period of time. The second pressure can be greater or
lower than the initial pressure. The further predetermined period
of time can also be less than, greater than or the same as the
first predetermined period of time. In another embodiment, the
pressure applied by the pressing means can continue to gradually
increase throughout the embossing step.
[0047] In the method, the embossing tool with the embossed sheet
and protective layer positioned thereon, can be relatively removed
from within the pressing means. Following pressing of the sheet of
electrically conducting material, the layer of protective material
can be removed from the embossed sheet. The layer of protective
material is preferably removed from the embossed sheet before the
sheet is removed from the embossing tool. In another embodiment,
the protective layer is retained on the sheet through later
processing steps.
[0048] As described, once the sheet has been pressed to form a
raised pattern therein, unwanted portions of the sheet can be
removed. The unwanted portions can be removed by any number of
ways, such as by cutting or by an abrading means.
[0049] It is envisaged that the cutting step can be performed at
the same time as the pressing of the sheet of the conductive
material. In this case the pressure applied to the sheet can be
adjusted so as to be sufficient to cause the cutting of the sheet
over the sharp edges of the embossing tool. In such an embodiment,
the embossing tool is design to feature sharp edges that favour
cutting the sheet. The cutting step is preferably performed
relatively quickly. In a further embodiment, the sheet is
preferably cooled prior to cutting. In one embodiment, the sheet
can be cooled by liquid nitrogen prior to cutting.
[0050] In a still further embodiment, the sheet can be clamped to
the embossing tool at the location of the protrusions of the
tool.
[0051] The abrading means can preferably abrade or grind the
unwanted portions from the sheet. It will be appreciated that the
step of abrading the unwanted portions of the sheet may comprise
more than one step. For example, a relatively coarse first abrading
step may be firstly performed to move relatively large pieces of
the unwanted portion of the sheet. Once this first step is
complete, removal of finer pieces can be made by one or more
additional abrading or polishing steps. In one embodiment, each
additional abrading step removes finer pieces of the sheet than the
preceding step. These additional steps ensure that the dimensions
and shape of the remaining portions of the sheet match the
originally desired configuration.
[0052] To prepare the embossed sheet for removal of the unwanted
portion, the embossed sheet can be adhered by a layer of an
adhesive to a support base. The adhesive is preferably a material
that can be used to reversibly anchor the embossed sheet to the
base. In one embodiment a PVA (polyvinyl alcohol) based adhesive is
used that can hold the embossed sheet in place and, after the
removal of the unwanted material, can be dissolved in water,
freeing the said structure. In another embodiment, the preferred
adhesive is an electrodisbonding adhesive. In this case, the
support base must be electrically conducting. The support base can
be formed from a group consisting of high-alloy steel, carbon
steel, stainless steel, aluminium, aluminium alloys, copper, and
titanium.
[0053] In one embodiment, the electrodisbonding adhesive is an
epoxy resin formulation capable of forming relatively high strength
adhesive bonds with conductive substrates but which can be
relatively rapidly released through the application of a low
voltage current. Disbonding preferably occurs via electrochemical
reactions induced at the interface between the cured adhesive and
the bonded substrate.
[0054] To adhere the embossed sheet to the support base, a quantity
of adhesive is preferably firstly placed on a surface of the
support base. Support spacers for a top plate are preferably
positioned on the base plate around the border of the adhesive. The
spacers can be relatively short. For example, the spacers can have
a height of between about 1 and 1000 microns, more preferably about
150 microns.
[0055] Once the adhesive and spacers are in place, the embossed
sheet is preferably placed on the adhesive. In one embodiment, the
embossed sheet is placed on the adhesive such that the raised
pattern extends outwardly away from the adhesive. In an alternative
embodiment, the embossed sheet is placed on the adhesive such that
the raised pattern extends inwardly into the adhesive.
[0056] Once the embossed sheet is in position, a top plate is then
preferably placed on top of the embossed sheet and pressed
downwardly until it rests on the spacers. The top plate is
preferably formed from the same material as the base plate. A
different material for the top plate could, however, be utilised.
The top and bottom plate should be substantially parallel with
respect to each other.
[0057] Once the adhesive is cured, the top plate and spacers can be
removed. The support base, with the embossed sheet adhered thereto,
is then ready to undergo further processing as defined above.
[0058] Where the raised pattern extends outwardly away from the
support base, the abrading means will preferably remove a portion
of the raised pattern formed in the sheet. Where the raised pattern
extends inwardly into the adhesive, the non-raised portion of the
sheet, or at least a portion thereof, will preferably be removed by
the abrading means.
[0059] The remaining portion of the sheet left after the abrading
step preferably comprises a plurality of electrically independent
portions that preferably serve as stimulating pads of the electrode
array. Where desired, the remaining portion also serves to provide
the electrical connection means to the formed stimulating pads.
[0060] As previously defined, the step of working the sheet can
include a step of punching portions out of the sheet of
electrically conductive material. In one embodiment, the sheet of
electrically conductive material, such as the platinum sheet
defined herein, can be coated on a layer of resiliently flexible
material, preferably a biocompatible resiliently flexible material
like a silicone. A punch means fabricated so as to punch out a
desired portion of the sheet is preferably brought into engagement
with the sheet and punches out a desired portion. In a preferred
embodiment, the stroke of the punch is such that the punch pushes
the desired portion into the silicone layer where it can remain
embedded.
[0061] In one embodiment, the step of punching out portions can
comprise one use of a punch. In another embodiment, multiple uses
of a punch may be necessary to form a predetermined pattern in a
sheet. In another embodiment, the punch can be adapted to punch
different portions of the sheet to different levels within the
resiliently flexible layer.
[0062] This embodiment has the advantage of potentially forming two
or more conductive layers from a single sheet of electrically
conductive material.
[0063] As also previously defined, the step of working the sheet
can include a step of slicing or cutting the sheet of electrically
conductive material. In this embodiment, a cutting or slicing tool
can be fabricated to form appropriate cuts in the sheet of
electrically conductive material so resulting in the formation of a
predetermined pattern of electrically conductive regions. In using
such a tool, the sheet of electrically conductive material, such as
the platinum sheet defined herein, can be coated on a layer of
resiliently flexible material, preferably a biocompatible
resiliently flexible material like a silicone. The cutting tool can
be constructed so as to be relatively driven into contact with the
surface of the platinum sheet. The tool can further be fabricated
so as to drive at least a portion of the sheet into the resiliently
flexible material.
[0064] In one embodiment, the method can further include the step
of encapsulating at least one surface of the embossed sheet. In a
preferred embodiment, the abraded surface of the sheet can be
encapsulated in an electrically insulating material. This material
is further also preferably bicompatible and resiliently flexible.
One example of a possible encapsulating material is silicone.
[0065] Once the silicone is cured, the subassembly is removed from
the "reversible" adhesive. In the case of the PVA adhesive, this
can be removed by applying a certain quantity of water to dissolve
away the PVA-based adhesive.
[0066] Once disbonded, the result is a plurality of separate
electrically independent conductive portions having a layer of
silicone encapsulated on one side thereof. If desired, the formed
electrode array can undergo further processing, including washing
and drying, to render it suitable for implantation as an
intracochlea electrode assembly.
[0067] In another embodiment, the embossing tool can be retained in
contact with the sheet of electrically conductive material. With
the embossing tool in place against one face of the embossed sheet,
the other face of the sheet can be encapsulated with at least a
first layer of resiliently flexible material. This layer of
material can comprise a layer of a polymeric or elastomeric
material, such as a silicone or rubber. In a further embodiment,
more than one layer of encapsulating material can be coated on the
other face of the embossed sheet. The selected encapsulating
material is preferably adapted to adhere strongly to the other face
of the sheet. If necessary, a suitable silicone/metal adhesive can
be used to ensure the encapsulating silicone layer remains in
contact with the other face on subsequent removal of the embossing
tool from said one face of the sheet.
[0068] With the embossing tool removed, the one face can then be
subject to the abrading step of the process with at least a portion
of the sheet not comprising part of the raised pattern therein
being abraded from the sheet. If necessary, the encapsulation on
the other face of the sheet can be rapidly cooled, such as by
immersion in liquid nitrogen, to stiffen and harden the
encapsulation prior to and/or while the abrading step is being
performed.
[0069] In another embodiment, the removal of the embossing tool is
not required. The embossed sheet in this embodiment is kept in
close proximity of the embossing tool after the embossing process.
In this embodiment the embossing tool is a disposable item and it
is preferably fabricated using a low cost process to minimise the
cost thereof.
[0070] As a result of the abrading step, a plurality of
electrically separated stimulating pads and appropriate conducting
means for each pad are formed. A layer of silicone or other
suitable resiliently flexible and preferably biocompatible material
is then used to form an encapsulation of the abraded side of the
sheet. While this layer of encapsulation should encapsulate the
electrical conduction means, it is preferred that the formed
stimulating pads are not encapsulated. Accordingly, the mould used
in the moulding of this encapsulation can incorporate upstanding
insets that extend outwardly from the mould and which are aligned
with the positions of the formed stimulating pads. These insets
preferably abut the pads and so prevent the encapsulation covering
the pads during the encapsulating process.
[0071] In one embodiment, two or more arrays formed using the
method can be laminated together to form a single tissue
stimulating electrode assembly. In one embodiment, the assembly can
be formed from a first lamination having 7 electrodes, a second
lamination having 8 electrodes and a third lamination having 8
electrodes, to form an electrode assembly having 23 electrodes. In
the case of a cochlear electrode array, the formed array will
preferably have 22 intracochlea electrodes and one extracochlea
electrode. Such a lamination process preferably results in a linear
array of the 22 electrodes.
[0072] In a further aspect, the present invention is a tool for use
in the method as defined herein. In one embodiment, the tool can be
an embossing tool.
[0073] In a preferred embodiment of this aspect, the tool is formed
from a material that will emboss the electrically conducting sheet
used in the method. Where the sheet is thin platinum sheet, the
embossing tool can be formed from a metal material, such as a
copper, or another material such as silicon wafer, or suitable
plastics such as polycarbonate or polyimide.
[0074] The embossing tool will have a plurality of protrusions
formed therein. The shape, dimension and position of the
protrusions represent the raised pattern to be formed in the sheet
of electrically conducting material. In the case of the silicon
wafer, the protrusions can be etched in the wafer. In the case of a
metallic embossing tool, the protrusions can be fabricated through
use of laser micromachining. The plurality of protrusions can be
adapted to form embossments in the sheet that are later removed
from the sheet. In another embodiment, the protrusions can be
adapted to form embossments that are not later removed from the
sheet.
[0075] As an example only, to form a plurality of parallel linearly
disposed electrical conduction means, the embossing tool preferably
has a series of protrusions extending for a length in side-by-side
relationship. The protrusions can narrow in thickness from their
base to their top. In one embodiment, each protrusion at its base
can have a thickness of between about 48 and 54 microns. At the
top, each protrusion can have narrowed in thickness to between
about 28 and 30 microns. The distance between adjacent protrusions
at the base can be between about 65 and 67 microns, while the
distance between the protrusions at the top is between about 86 and
87 microns. Each protrusion can have a height of about 30
microns.
[0076] Each ridge preferably ends in a pad protrusion adapted to
emboss the electrically conductive sheet in a manner suitable to
form a stimulating pad. The protrusion is preferably substantially
rectangular in shape. To allow the formation of a longitudinal
electrode array, each ridge preferably turns just prior to its join
with its respective electrode protrusion. The turn in the ridge can
be smoothly curved.
[0077] In a further embodiment, the plurality of aligned
protrusions for the electrical conduction means extend linearly
away from the pad protrusions for a length. The protrusions then
further preferably spiral inwardly in ever decreasing circles. At
an end distal the pad protrusion, each protrusion preferably
terminates in a feedthrough electrode protrusion. The distal
protrusion preferably forms an electrode for connection to the
feedthrough of a receiver/stimulator means that will preferably be
electrically connected to the electrode assembly formed using the
tool.
[0078] In one embodiment, each embossing tool can have two sets of
protrusions formed therein to allow creation of two electrode
arrays from a single sheet of electrically conducting material,
such as platinum.
[0079] According to a still further aspect, the present invention
is directed to another invention comprising a method of forming a
device comprised of a predetermined pattern of relatively
electrically conductive regions and relatively resistive regions,
the method comprising the steps of:
[0080] (i) coating at least a first surface of a sheet of
electrically conductive material with at least a first layer of
another electrically conductive material;
[0081] (ii) forming a predetermined pattern in the sheet of
electrically conductive material by removing portions of the sheet
therefrom such that at least the pattern of electrically conductive
regions remains;
[0082] (iii) coating a second surface of the sheet of electrically
conductive material with a layer of resiliently flexible material;
and
[0083] (iv) removing the first layer from the first surface of said
sheet.
[0084] In this aspect, the method is preferably used to form an
electrode array with step (ii) comprising a step of forming a
predetermined electrode array pattern in the sheet.
[0085] In a preferred embodiment of this aspect, the sheet of
electrically conductive material is a biocompatible material. In a
preferred embodiment, the sheet is a platinum sheet. The sheet is
preferably in the form of a foil having a thickness of between
about 1 and 100 microns. The foil preferably has a thickness no
greater than 50 microns, more preferably no greater than 20
microns. Other suitable thicknesses can be envisaged. Each sheet
can have a dimension of about 50 mm.times.250 mm. The size of the
sheet will though depend on the requirements of the tooling used
for the method. As such, sheets of different dimensions can be
envisaged.
[0086] In a further embodiment, the first layer of electrically
conductive material comprises a metal, such as copper. The copper
layer is preferably plated to the first surface of the sheet in a
plating bath. Prior to the first layer being applied to the sheet,
the sheet is preferably supported in a holder. An adhesive such as
a spray adhesive or tape adhesive can be used to support the sheet
to the holding member. The copper layer can have a thickness of
about 100 microns. In another embodiment, the first layer can
comprise a layer of electrically conductive paint or
electrodisbonding glue applied to the first surface of the sheet.
In still a further embodiment the first layer could be formed from
any type of conductive removable layer, such as electrically
conductive double sided tape.
[0087] In a still further embodiment, a thin layer of a suitable
conductive material that is biocompatible, such as gold, may be
deposited as an interface layer between said first layer and the
first surface of the sheet. The thickness of the thin interface
layer is preferably substantially smaller than the thickness of the
first layer. In one embodiment, the thickness of the first layer
and the sheet can be substantially similar or the same.
[0088] Once the first layer has been applied to the sheet, it is
preferably polished. The purpose of the polishing is to ensure that
the first, preferably copper, layer is as flat as possible.
[0089] Step (ii) of this aspect preferably comprises a process of
using electrical discharge machining (EDM), which is also known as
spark erosion, to remove unwanted portions of the sheet. In a
preferred embodiment, the EDM equipment used in the process has a
cutting tool comprising an electrode. The cutting tool does not
physically cut the sheet but instead relies on the equipment
generating a series of electrical discharges between the electrode
and the sheet in a dielectric fluid. The electrical discharges
serve to vaporise the sheet in the region adjacent the cutting
tool.
[0090] In a preferred embodiment, the cutting tool has a size and
shape that matches the size and shape of the portion of the sheet
to be removed from the sheet during the machining steps comprising
step (ii). In this embodiment, it is preferred that the tool is
brought adjacent the sheet at a number of different locations so as
to remove differing portions of the sheet. This multiple use of the
tool preferably serves to gradually build up the pattern of the
electrode array.
[0091] In a preferred embodiment, the cutting tool is preferably
used to form a linear array of discrete substantially rectangular
stimulating pads or electrodes in the sheet, each pad preferably
having a conducting portion extending away therefrom to a location
distal the pad. Each conducting portion can extend lineally away
from its pad. The linear conducting portions are preferably aligned
in a parallel arrangement. The conducting portions are hereinafter
referred to as "wires" as they serve to provide electrical
conduction between each pad to a location distal the electrode
array eventually formed using the method defined herein.
[0092] Each pad formed in the sheet can have a size of about 0.4
mm2-0.5 mm2. In one embodiment, each electrode can have dimensions
of about 500.times.600 microns. It will be appreciated that the
pads of the array can all be the same size. In another embodiment,
the dimensions of at least some of the pads can vary from that of
others in the array.
[0093] In a preferred embodiment, the EDM/milling equipment is used
to remove the platinum where desired and at least a portion of the
copper layer preferably plated therebeneath. The EDM/milling
equipment is preferably operated so as to not punch through the
copper layer. The copper layer, as well as enabling the machining
to occur, also acts as a carrier of the pattern after the
EDM/milling process has occurred, so that the pattern is in a form
that is easily handled.
[0094] In another embodiment, step (ii) can comprise a step of
using laser ablation, micro-knifing, etching, or milling to remove
unwanted portions of the sheet. The present inventors have
determined that a milling machine having a 100 micron cutter can be
used to create wires having a width of between 5 and 50 microns,
with a spacing between the wires of about 110 microns.
[0095] In a preferred embodiment, step (iii) can comprise coating
the second surface with a layer of parylene and/or silicone. The
process can further comprise an additional step prior to step (iii)
in which at least the second surface of the sheet is cleaned and/or
degreased.
[0096] The resilient flexible coating can be sprayed on to the
second surface of the sheet. Other coating techniques that could be
used in step (iii) comprise spinning, dipping, adhering or plasma
treatment.
[0097] The resiliently flexible layer serves to hold the sheet in
the pattern formed during step (ii) during subsequent processing
steps. The layer is also preferably relatively electrically
insulating and is used as an insulating layer in the electrode
array once formed, as is described in more detail below.
[0098] Prior to the coating of the second surface with the layer of
resiliently flexible material, the method can comprise an
additional step in which the areas of sheet removed in step (ii)
are filled with a relatively electrically insulating material. The
filler can be selected from the group comprising PVA, PEG, and a
similar compound. The filler serves to prevent the layer of
resiliently flexible material flowing into the gaps in the sheet
formed by the removal of those portions of the sheet in step
(ii).
[0099] The nature of step (iv) will depend on the material used to
form the first layer. In one embodiment, the copper layer can be
removed by dissolution. In one embodiment, an electromechanical
dissolution can be used which operates on the principle that the
copper layer can be oxidised and hence dissolved at a potential
that is lower than the potential required to oxidise the remaining
platinum of the sheet. Where an interface layer, such as a gold
layer, is present, the copper layer could be removed by dissolution
and the interface layer by electrodissolution.
[0100] Following step (iv) of this aspect, the method further
preferably comprises the following step:
[0101] (v) coating the exposed first surface of the sheet with a
layer of resiliently flexible material.
[0102] In one embodiment, the layer of material coated to the sheet
in step (v) can comprise the same material coated to the second
surface in step (iii) as defined herein. In another embodiment, the
layer can be a different material.
[0103] During step (v), the pads formed in step (ii) can be masked
to ensure they remain uncovered with the layer of resiliently
flexible material. The wires are preferably not masked and are
preferably coated by this layer of resiliently flexible material.
In another embodiment, the layer coated to the sheet in step (v)
can be removed where necessary, such as by laser ablation, so as to
expose the covered pads.
[0104] Following step (v), the sheet is preferably trimmed to
remove the remaining portions of the sheet that are not comprising
the desired electrode array and wires extending therefrom. In one
embodiment, the sheet can be trimmed with a knife. In another
embodiment, a stamping press can be used to cut the electrode array
and wires from the remaining portions of the original sheet. In
another embodiment, a mask can be used to mask those portions of
the sheet between the arrays prior to a spraying of the silicone
through the mask and onto the surface of the sheet.
[0105] In a preferred embodiment, all of the required number of
pads for a single electrode array are formed in different regions
of a single platinum sheet. In this embodiment, each sheet can have
a number of respective sets of portions of what will become a
single electrode array formed therein. Once each of the sets are
formed as described herein, each trimmed set can be stacked one
above the other to form an aligned array of stimulating pads.
[0106] In one embodiment, the electrode array can comprise 30
stimulating pads. In this embodiment, the formed electrode array
can comprise 5 different sets of pads that have been formed in the
manner described herein and then stacked to form a single electrode
array. In one embodiment, where the electrode array comprises 30
pads, the array can comprise 3 sets of 7 pads, 1 set of five pads
and 1 set of 4 pads. In this embodiment, the 3 sets of 7 pads are
stacked one on top of the other, the set of five pads is stacked on
these sets, with the set of 4 pads on top of the stack. Other
combinations of sets can, however, be envisaged.
[0107] While the sets of stimulating pads are stacked one upon the
other, it will be appreciated that the actual position of the pads
in each set are not necessarily vertically aligned. Rather, the set
immediately above its lower set may be laterally offset so as to
ensure the pads are visible from beneath the stack.
[0108] The wires extending from each stimulating pad are preferably
of the same length. It can, however, be envisaged that the wires
could be formed with different lengths to account for the ultimate
offset present when forming the stack and to allow for alignment to
an adjoining component of a device, if necessary.
[0109] Once the stack is formed, the hitherto at least
substantially planar pads are preferably deformed so as to at least
partially extend through a third dimension. In a preferred
embodiment, each of the stimulating pads are curved out of the
plane of the wires for each set of pads. The curvature can be
substantially semi-circular. A mandrel can be used to form the
curvature in the pads.
[0110] Once the stimulating pads have been deformed to have a
substantially semi-circular curvature, each of the stimulating pads
can be further folded about a longitudinal axis of the array. This
folding of the pads preferably serves to bend the pads around the
wires of the array. The pads can be folded individually, in small
groups, or all together. In one embodiment, the stimulating pads
are folded so as to define a lumen that extends through the
array.
[0111] Once the electrode array is complete it can be encapsulated
in a further layer of a biocompatible material to form a electrode
carrier member. In a preferred embodiment, the biocompatible
material can be a silicone, such as a flexible silicone
elastomer-Silastic. Silastic MDX 4-4210 is an example of one
suitable silicone for use in the formation of the carrier
member.
[0112] In another embodiment, the elongate carrier member can be
formed from a polyurethane or similar material.
[0113] In one embodiment, this step can be formed in a mould with
the biocompatible material allowed to set around the array. In this
embodiment, the stimulating pads are preferably positioned in the
mould so as to not be coated with the biocompatible material. In
one embodiment, the carrier member can be moulded in a straight
configuration. In another embodiment, the carrier member can be
moulded in a curved configuration, such as a spirally-curved
configuration.
[0114] In a further embodiment of the method, step (i) can include
a step of also coating the second surface of the sheet with a top
layer of said another electrically conductive material. In this
embodiment, the top layer on the second surface is preferably
thinner than the layer on the first surface. During step (ii), and
in particular electrical discharge machining of the sheet, the top
layer preferably serves to minimise pitting in the sheet. It is
desirable to minimise such pitting as the pits may act as stress
risers in the ultimately formed electrode array. The top layer
again preferably comprises a layer of copper. The coating can be
formed using any one of the methods defined above for coating the
first surface of the sheet.
[0115] Where the top layer has been coated on the second surface in
step (i), it is necessary that this be removed prior to the laying
down of the layer of resiliently flexible material on the second
surface in step (iii). Where the top layer is thinner, the top
layer can be removed by dissolution. The time of dissolution would
need to be set to ensure removal of the top layer but not total
removal of the layer on the first surface of the sheet. In another
embodiment, the layer on the first surface could be masked while
the top layer is dissolved. The mask could comprise a double-sided
tape or a plastics coating which serves to protect this layer while
the top layer is being dissolved.
[0116] According to a still further aspect, the present invention
is directed to a further invention comprising a method of forming a
device comprised of a predetermined pattern of relatively
electrically conductive regions and relatively electrically
resistive regions, the method comprising the steps of:
[0117] (i) coating at least a first surface of an electrically
conductive material with a first layer of another material that is
relatively electrically insulating;
[0118] (ii) forming a predetermined pattern in the sheet of
electrically conductive material by removing portions of the sheet
therefrom such that at least the pattern of electrically conductive
regions remain; and
[0119] (iii) coating a second surface of the sheet of electrically
conductive material with a layer of resiliently flexible
material.
[0120] In this aspect, the device is preferably an electrode array
and step (ii) comprises forming a predetermined electrode array
pattern in the sheet.
[0121] In this aspect, step (ii) could not comprise use of EDM as
described above. Rather, step (ii) could comprise use of a sheet
portion removal technique such as laser cutting, micro-knifing,
chemical etching, stamping, milling or roller cutting.
[0122] In this aspect, the first layer can comprise a polymeric
material, such as a polycarbonate, polytetrafluoroethylene,
polyimide, PAA, or PVA, or other dissoluble material.
[0123] In this aspect, step (iii) can be performed in a manner
similar or identical to that defined above in the preceding
aspect.
[0124] Still further, this aspect can comprise the following
step:
[0125] (iv) removing the first layer from the first surface of said
sheet.
[0126] In another embodiment, the first layer can be retained on
the first surface of the sheet and incorporated into the electrode
array.
[0127] The method of this further aspect can incorporate the steps
outlined above with respect to the preceding aspect, where
compatible with the steps of the further aspect.
[0128] According to a still further aspect aspect, the present
application is directed to yet another invention comprising an
electrode array formed by the methods defined herein.
[0129] In still yet a further aspect, the present invention is an
electrode array for use in a tissue stimulating device, the
electrode array comprising a plurality of electrodes or stimulating
pads, each electrode or pad having at least one electrical
conduction means extending away therefrom, the electrodes and
electrical conduction means formed from a worked sheet of
electrically conducting material.
[0130] In a preferred embodiment of this aspect, the sheet is a
sheet of platinum, such as is defined above. The at least one
electrical conduction means and its respective stimulating pad can
be integrally formed. In another embodiment, the at least one
electrical conduction means and a stimulating pad can be separately
formed and later brought into electrical engagement with each
other.
[0131] In a preferred embodiment, the stimulating pads and at least
a portion of the electrical conduction means are housed within an
elongate carrier. In one embodiment, the elongate carrier can be
formed from a biocompatible polymeric or elastomeric material. In
one embodiment, the elastomeric material can be a silicone rubber.
In another embodiment, the elongate member can be formed from a
biocompatible polyurethane or similar material. The carrier
preferably has a proximal end, a distal end and at least an inner
surface adapted to conform to the inner wall of the cochlea. The
carrier can be formed from more than one layer.
[0132] The electrode array is preferably adapted to receive
stimulation signals and transmit electrical stimulations through
the stimulating pads to the implantee's auditory nerves.
[0133] In a still further embodiment, at least one pad in the array
has a surface that is at least adjacent the inner surface of the
carrier. More preferably, each of the pads in the array has a
surface that is adjacent the inner surface of the elongate carrier.
In a further embodiment, the surfaces of the pads are aligned with
the inner surface of the elongate member. In another embodiment,
the surfaces of the pads stand proud of the inner surface of the
elongate carrier. It is also envisaged that the pad surface could
also be recessed into the inner surface of the elongate
carrier.
[0134] The surfaces of the elongate member are preferably smooth to
prevent any damage to the cochlea as the array is placed in the
cochlea.
[0135] The electrode array fabricated by said method will
preferably have a straight array and may or may not require further
coating with nonconductive materials (e.g. silicone). If a
different final shape of the electrode array is required, at least
another coating of the array with a nonconductive biocompatible
material may be required to create the required shape. In one
embodiment, the array is overmoulded to create a curly shaped
array.
[0136] In yet a further embodiment, a longitudinal lumen can extend
through the elongate member for at least a portion of its length.
The lumen can act as a substance delivery means for delivering a
bio-active substance to the implant site following implantation. In
another embodiment, the lumen can receive a stylet to assist in
insertion and placement of the array in the cochlea.
[0137] In a preferred embodiment, the electrode array is for use as
an implantable tissue-stimulating device. More preferably, the
tissue-stimulating device is a cochlear electrode assembly, more
preferably an intracochlear electrode assembly.
[0138] In a preferred embodiment, the intracochlear electrode
assembly is a part of an implanted component of a cochlear implant
system. The implanted component further preferably comprises a
receiver coil and a housing for a stimulator means. The carrier
member preferably extends outwardly from the housing of the
stimulator means.
[0139] In a further embodiment, the carrier member has a leading
end that is insertable into a cochlea of an implantee and a
trailing end distal the leading end. The wires of the electrode
array preferably extend back towards the trailing end of the
carrier member.
[0140] The wires preferably extend back to the housing to at least
a first feedthrough in the wall of the housing. The wires are
preferably exposed at or adjacent the trailing end to allow
connection to the feedthroughs. In one embodiment, the feedthrough
provides hennetic and insulated electrical connection for each wire
extending from the electrode assembly into the housing of the
implantable component. Each feedthrough can be formed using the
method described in U.S. Pat. No. 5,046,242, the contents of which
are incorporated herein by reference.
[0141] In a preferred embodiment, the orientation of the carrier
member as it is firstly inserted through a cochleostomy into the
cochlea is preferably substantially straight. More preferably, the
implantable orientation is straight. Following completion of
implantation, the carrier member preferably adopts a spirally
curved configuration that matches the spiral nature of the scala
tympani of the human cochlea. The carrier member is preferably
pre-formed with this spiral configuration and is then straightened
either during manufacture and packaging of the device or prior to
implantation. The carrier member is preferably held straight prior
to a at least during the initial stages of implantation by a
stylet. The stylet preferably extends through a lumen of the
carrier member such as the lumen described herein that is formed by
the folding of the electrodes about the wires.
[0142] In a further embodiment, the housing is preferably
implantable in a recess of the temporal bone adjacent the ear of
the implantee that is receiving the output of the implant system.
The housing is preferably formed from a biocompatible material or
has a biocompatible coating. The housing can be coated with a layer
of silicone or parylene.
[0143] As already discussed, the implantable component preferably
also comprises a receiver coil. The receiver coil preferably
comprises a wire antenna coil. The antenna coil can be comprised of
at least one, and preferably at least three, turns of electrically
insulated platinum or gold wire tuned to parallel resonance by a
capacitor internal to the housing. The electrical insulation of the
antenna coil can be provided by a flexible silicone moulding and/or
silicone or polyurethane tubing. The external coil can be
constructed in a similar fashion to the implanted coil or have a
different construction.
[0144] The antenna coil is preferably external of the housing.
Electrical connection between the antenna coil and componentry of
the implantable componentry within the housing can be provided by
two hermetic and electrically insulated ceramic feedthroughs or an
electrical conductor. The ceramic feedthroughs can be formed using
the method described in abovementioned U.S. Pat. No. 5,046,242.
[0145] The antenna coil of the implantable component preferably
acts as part of the radio frequency (RF) link to allow
transcutaneous bidirectional data transfer between the implantable
component and an external components of the cochlear implant
system. The radio frequency signals can comprise frequency
modulated (FM) signals. While described as a receiver coil, the
receiver coil can preferably transmit signals to the transmitter
coil which receives the signals.
[0146] The link between the two coils also provides a means of
powering the componentry of the internal component. Where the
implantable component further has an on-board or implantable power
source, such as a rechargeable battery, the link can provide a
means of inductively charging the battery when required.
[0147] The implanted housing preferably contains, in addition to
the stimulator means, a receiver means. The receiver means is
preferably adapted to receive signals from the external
component.
[0148] The housing of the external component preferably houses a
speech processor adapted to receive signals output by a microphone.
In a preferred embodiment, the microphone can be mounted to the
housing or an ear hook member. Other suitable locations for the
microphone and/or the housing for the speech processor can be
envisaged, such as a lapel of the implantee's clothing.
[0149] The speech processor encodes the sound detected by the
microphone into a sequence of electrical stimuli following given
algorithms, such as algorithms already developed for cochlear
implant systems. The encoded sequence is transferred to the
implanted receiver/stimulator means using the transmitter and
receiver coils. The implanted receiver/stimulator means demodulates
the FM signals and allocates the electrical pulses to the
appropriate attached electrode by an algorithm which is consistent
with the chosen speech coding strategy.
[0150] The external component preferably further comprises a power
supply. The power supply can comprise one or more rechargeable
batteries. The transmitter and receiver coils are used to provide
power via transcutaneous induction to the implanted
stimulator/receiver means and the electrode array.
[0151] While the implant system can rely on external componentry,
in another embodiment, the microphone, speech processor and power
supply can also be implantable. In this embodiment, these
components can be contained within a hermetically sealed housing or
the housing used for the stimulator means.
[0152] In this aspect, the array can be formed by the embossing or
EDM processes defined herein.
[0153] In a still further aspect, the present invention is a device
having an electrically conductive component, the component being
formed from a worked sheet of electrically conducting material, the
sheet having a thickness less than about 50 microns.
[0154] In this aspect, the sheet can be a platinum foil, such as is
defined herein. For example, the platinum foil can have a thickness
no greater than about 20 microns. The sheet can further have a
dimension of about 50 mm.times.250 mm.
[0155] In a further embodiment of this aspect, the electrically
conductive component can comprise at least one conductive wire
formed from the platinum foil, the wire having a width of between
about 1 and 100 microns, more preferably 1 and 70 microns.
[0156] Still further, the electrically conductive component can
comprise a plurality of discrete conductive wires formed from the
platinum foil, each wire being electrically insulated from its
neighbouring wire. In one embodiment, the spacing between
neighbouring wires can be between about 10 and 100 microns. Still
further, the wires can be disposed for at least a portion of their
lengths in a parallel arrangement.
[0157] Each conductive wire can extend from an electrode also
formed from the platinum foil. The electrode can have an areal
dimension of less than about 0.5 mm2.
[0158] In this aspect, the device can be a component of a tissue
stimulating device, such as an intracochlear electrode assembly. In
another embodiment, the device can be a biosensor. Still further,
the device can be a miniature wire.
[0159] In this aspect, the component can be formed by machining the
sheet of electrically conductive material to remove a portion
therefrom such that at least a pattern of electrically conductive
regions remains. The machining of the sheet can comprise a step of
using electrical discharge machining (EDM) to remove unwanted
portions of the sheet. Other methods as defined herein can also be
utilised.
[0160] In yet a further aspect, the present invention is a method
of forming a device comprised of a predetermined pattern of
relatively electrically conductive regions and relatively
electrically resistive regions, the method comprising the steps
of:
[0161] (i) mounting a sheet of electrically conductive material in
an electrical discharge machining (EDM) device, the device having a
discharge electrode of a predetermined shape;
[0162] (ii) programming the EDM device to bring the electrode
adjacent the sheet; and
[0163] (iii) operating the EDM device to remove a portion of the
sheet corresponding to the shape of the electrode.
[0164] In this aspect, the sheet prior to mounting in the EDM
device is firstly coated on at least a first surface thereof with a
sheet of electrically conductive material. The layer can comprise a
layer of metal, such as copper. The copper layer is preferably
plated to the first surface of the sheet in a plating bath. Prior
to the first layer being applied to the sheet, the sheet is
preferably supported in a holder. An adhesive such as a spray
adhesive or tape adhesive can be used to support the sheet to the
holding member. The copper layer can have a thickness of about 100
microns. In another embodiment, the first layer can comprise a
layer of electrically conductive paint applied to the first surface
of the sheet. In still a further embodiment the first layer could
be formed from any type of conductive removable layer.
[0165] Once the first layer has been applied to the sheet, it is
preferably polished. The purpose of the polishing is to ensure that
the first, preferably copper, layer is as flat as possible.
[0166] Once the pattern has been formed in the sheet, a second
surface of the sheet of electrically conductive material can be
coated with a layer of resiliently flexible material. Once
completed, the method can then comprise a step of removing the
first layer from the first surface of said sheet.
[0167] In this aspect, the method is preferably used to form an
electrode array with step (iii) comprising a step of forming a
predetermined electrode array pattern in the sheet.
[0168] In a preferred embodiment of this aspect, the sheet of
electrically conductive material is a biocompatible material. In a
preferred embodiment, the sheet is a platinum sheet. The sheet is
preferably in the form of a foil having a thickness of between
about 10 and 50 microns. The foil preferably has a thickness no
greater than 50 microns, more preferably no greater than 20
microns. Other suitable thicknesses can be envisaged. Each sheet
can have a dimension of about 50 mm.times.250 mm. The size of the
sheet will though depend on the requirements of the tooling used
for the method. As such, sheets of different dimensions can be
envisaged.
[0169] Step (iii) of this aspect preferably comprises a process of
using electrical discharge machining (EDM), which is also known as
spark erosion, to remove unwanted portions of the sheet. In a
preferred embodiment, the EDM equipment used in the process has a
cutting tool comprising an electrode. The cutting tool does not
physically cut the sheet but instead relies on the equipment
generating a series of electrical discharges between the electrode
and the sheet in a dielectric fluid. The electrical discharges
serve to vaporise the sheet in the region adjacent the cutting
tool. It is considered that other types of material removal such as
those performed by a milling machine could also be implemented in
this step to form the desired shapes on the sheet.
[0170] In a preferred embodiment, the cutting tool has a size and
shape that matches the size and shape of the portion of the sheet
to be removed from the sheet during the machining steps comprising
step (ii). In this embodiment, it is preferred that the tool is
brought adjacent the sheet at a number of different locations so as
to remove differing portions of the sheet. This multiple use of the
tool preferably serves to gradually build up the pattern of the
electrode array.
BRIEF DESCRIPTION OF THE DRAWINGS
[0171] By way of example only, preferred embodiments of the
invention are now described with reference to the accompanying
drawings, in which:
[0172] FIG. 1 is a perspective view of one example of the
protrusions of an embossing tool for use in one embodiment of the
method according to the present invention;
[0173] FIG. 2 is a cross-sectional view of another embossing tool
for use in the method according to the present invention;
[0174] FIG. 3 is an expanded cross-sectional view of the embossing
tool of FIG. 2 positioned in a horizontal press;
[0175] FIG. 4 is an expanded cross-sectional view of an embossed
sheet positioned on the embossing tool of FIG. 2;
[0176] FIG. 5 depicts the embossed sheet being prepared for an
abrading step;
[0177] FIG. 6 depicts a portion of the embossments formed in the
embossed sheet being removed in an abrading step;
[0178] FIG. 7 depicts the sheet following completion of the
abrading step;
[0179] FIG. 8 depicts the sheet following encapsulation with a
layer of silicone;
[0180] FIG. 9 is a cross-sectional view of the formed electrical
conduction means having a silicone encapsulation formed on one
side;
[0181] FIG. 10 is a plan view of an embossing tool for use in
forming two electrode arrays for a cochlear implant from a single
sheet of electrically conducting material;
[0182] FIG. 11 is an enlarged cross-sectional view of the
embossments formed in the sheet of platinum by the protrusions of
the embossing tool of FIG. 10 in the region used for formation of
the electrical conduction means;
[0183] FIGS. 12a, 12b, 13, 14 and 15 are simplified cross-sectional
views of further steps of the process for forming an electrode
array from a sheet of electrically conducting material according to
the present invention;
[0184] FIG. 15a is a cross-sectional view of a punch for use in
another embodiment of an invention according to the present
application;
[0185] FIG. 15b is a cross-sectional view of a sheet of
electrically conductive material mounted to a sheet of
biocompatible resiliently flexible material ready to be punched
using the punch of FIG. 15a;
[0186] FIG. 15c is a cross-sectional view of the sheet of FIG. 15b
following use of the punch of FIG. 15a;
[0187] FIG. 16 is a pictorial representation of a prior art
cochlear implant system;
[0188] FIG. 17a is a plan view of an electrode tip for use in EDM
equipment for use in one embodiment of the method according to the
present invention;
[0189] FIG. 17b is a plan view of a platinum sheet showing a line
of the sheet vaporised through use of the tool depicted in FIG.
17a;
[0190] FIG. 17c is a plan view of the platinum sheet of FIG. 17b
depicting how an electrode and adjoining wire can be formed
following a second use of the tool of FIG. 17a;
[0191] FIG. 17d is a plan view of the platinum sheet of FIG. 17b
depicting how an array of electrodes and adjoining wires are formed
by a plurality of uses of the tool of FIG. 17a;
[0192] FIG. 18a is a plan view of another electrode tip for use in
EDM equipment for use in one embodiment of the method according to
the present invention;
[0193] FIG. 18b is a plan view of a platinum sheet showing how
three lines of the sheet are vaporised through use of the tool
depicted in FIG. 18a;
[0194] FIG. 18c is a plan view of the platinum sheet of FIG. 18b
depicting how three electrodes and adjoining wires can be formed
following a second use of the tool of FIG. 18a;
[0195] FIG. 18d is a plan view of the platinum sheet of FIG. 18b
depicting how an array of electrodes and adjoining wires are formed
by a plurality of uses of the tool of FIG. 18a;
[0196] FIG. 19 is a plan view of a platinum sheet depicting how
different sets of electrodes and adjoining wires can be formed in a
platinum sheet through appropriate machining;
[0197] FIG. 20 is a drawing depicting how sets of electrodes formed
using an embodiment of the method defined herein can be stacked on
top of each other to form an electrode array suitable for use in a
cochlear implant system;
[0198] FIG. 21 is a drawing depicting a carrier member having an
array of curved electrodes with a stylet positioned therein, the
carrier being depicted in a configuration ready for insertion into
the cochlea of an implantee;
[0199] FIG. 22 is a drawing depicting the carrier member of FIG. 21
with the stylet retracted thereby allowing the carrier member to
adopt a more pronounced curvature;
[0200] FIG. 23 is a drawing depicting the carrier member of FIG. 21
with the stylet fully retracted thereby allowing the carrier member
to adopt its fully curved configuration; and
[0201] FIG. 24 is a flow chart depicting at least some of the steps
of the method of forming an electrode array according to the
present invention.
PREFERRED MODE OF CARRYING OUT THE INVENTION
[0202] Before describing the features of the present invention, it
is appropriate to briefly describe the construction of one type of
known cochlear implant system with reference to FIG. 16.
[0203] Known cochlear implants typically consist of two main
components, an external component including a speech processor 29,
and an internal component including an implanted receiver and
stimulator unit 22. The external component includes a microphone
27. The speech processor 29 is, in this illustration, constructed
and arranged so that it can fit behind the outer ear 11.
Alternative versions may be worn on the body. Attached to the
speech processor 29 is a transmitter coil 24 that transmits
electrical signals to the implanted unit 22 via a radio frequency
(RF) link.
[0204] The implanted component includes a receiver coil 23 for
receiving power and data from the transmitter coil 24. A cable 21
extends from the implanted receiver and stimulator unit 22 to the
cochlea 12 and terminates in an electrode array 20. The signals
thus received are applied by the array 20 to the basilar membrane 8
and the nerve cells within the cochlea 12 thereby stimulating the
auditory nerve 9. The operation of such a device is described, for
example, in U.S. Pat. No. 4,532,930.
[0205] One simplified example of an embossing tool for use in the
method of the present invention is depicted generally as 30 in FIG.
1. In the depicted embodiment, the tool 30 is formed from copper,
however, other suitable materials can be envisaged. The tool 30 has
a plurality of parallel linearly aligned protrusions 31. The widths
of each of the protrusions 31 is representative of the desired
width of the wires in the final product and is in the vicinity of
between about 1 and 100 microns, more preferably 1 and 70 microns.
The spacing between neighbouring protrusions can be between about
10 and 100 microns, representative of the spacings between the
wires of the final product. Each protrusion 31 has a right angle
turn that terminates in a larger electrode-forming protrusion 32.
Use of the tool 30 results in the formation of a raised pattern in
a suitable sheet of electrically conducting material, such as
platinum, that is pressed by the protrusions 31 and
electrode-forming protrusions 32.
[0206] Once the raised pattern is formed in the platinum sheet, as
is described below, those portions of the sheet that are not part
of the raised pattern can be removed from the sheet by abrasion or
other suitable methods. The result is as plurality of electrodes
each having an integrally formed electrical conduction means
extending away therefrom.
[0207] FIG. 2 is a cross-sectional view of a portion of another
embossing tool 40, made in this case from copper, for use in the
method according to the present invention. The portion depicted in
FIG. 2 is of the protrusions 41 used to form the electrical
conduction means for the electrode array.
[0208] The protrusions 41 extend outwardly from a base 42. The
protrusions 41 narrow in thickness from their base to their top.
Each protrusion at its base has a thickness of between about 48 and
54 microns. At the top, each protrusion has narrowed in thickness
to between about 28 and 30 microns. The distance between adjacent
protrusions at the base is between about 65 and 67 microns, while
the distance between the protrusions at the top is between about 86
and 87 microns. Each protrusion has a height of about 30 microns.
These dimensions should be considered as illustrative only.
[0209] As depicted in FIG. 3, the tool 40 can be positioned on a
relative stationary platen 51 of a press. The press used in the
method preferably can apply a pressure of up to 4-5 tonnes. Once
the tool 40 is in position, a sheet of platinum 43 (10-15 microns
thickness) is placed on the tool 40. A silicone backing layer 44 is
then laid over the sheet 43. In another embodiment, a thin layer of
a lubricant can be placed between the tool 40 and the sheet of
platinum 43 and between the sheet of platinum 43 and the backing
layer 44,
[0210] Once the silicone backing layer 44 is in position, the top
platen 52 of the press can be moved relatively downwardly to apply
pressure to the sheet 43 positioned on the tool 40. The platen 52
preferably applies an initial pressure for a predetermined period
of time (eg. 2 tonnes for 15 seconds) before an increased pressure
is applied for a further predetermined period of time (eg. 4 tonnes
for 60 seconds).
[0211] Once pressed, the platen 52 moves relatively upwardly to
allow removal of the tool 40 from the press with the sheet 43 and
backing layer 44 still in position on the tool 40.
[0212] Once removed from the press, the backing layer 44 can be
removed leaving the platinum foil 43, with a plurality of raised
ridges formed therein (43a), in position on the tool 40 as depicted
in FIG. 4.
[0213] FIG. 5 depicts the steps necessary to prepare the embossed
sheet 43 for removal of those portions of the sheet 43 that are
unwanted. A steel base plate 61 has a relatively thin smear of
electrodisbonding adhesive 62 (eg. ElectRelease.TM. E4 available
from EIC Laboratories, Inc.) or other adhesive coated thereon.
Spacers 63 having a height of about 80 are placed on the base plate
61 on each side of the adhesive 62. The lower face of the embossed
platinum foil 43 is then placed on the glue with the ridges 43a
extending upwardly. A top plate 64 is then placed on the top of the
embossed foil 43 and pressed down until it rests on the spacers
63.
[0214] The embossed foil 43 remains between plates 61 and 64 until
the adhesive 62 has cured. Once the adhesive is cured, the top
plate 64 and spacers 63 are removed. The support base 61, with the
embossed platinum foil sheet 43 adhered thereto, is then ready to
undergo step (ii) of the process defined above.
[0215] With the raised ridges 43a extending outwardly away from the
base plate 61, an abrading means 65 is used to remove a portion of
the raised pattern formed in the sheet 43. It will be appreciated
that if the foil 43 had been adhered to the base plate 61 with the
raised ridges 43a facing downwardly into the adhesive then the
non-raised portions of the foil 43 would be removed in the step of
the process depicted in FIG. 6.
[0216] As is depicted in FIG. 7, the remaining portions 43b of the
original sheet 43 left after completion of the step depicted in
FIG. 6 preferably comprise a plurality of electrically independent
portions. In FIG. 7, the depicted remaining portions 43b represent,
in cross-section, longitudinal conduction means that extend to
respective electrodes (not depicted) also formed from the sheet
43.
[0217] As depicted in FIG. 8, the method further includes the step
of encapsulating the embossed sheet 43 in an electrically
insulating, biocompatible and resiliently flexible silicone 45.
[0218] Once the silicone 45 is cured, an electrical connection can
be made to the remaining portions 43b of the platinum and to the
base plate 61. The respective electrical connections are then
preferably connected to a power supply. The positive terminal of
the power supply is preferably connected to the remaining portions
43b and the negative terminal to the base plate 61. Once turned on,
the provision of electrical current through the electrodisbonding
adhesive 62 results in it releasing from the embossed sheet 43b.
The applied voltage is preferably between 5V and 50V for a period
of between 1 second and 30 minutes.
[0219] Once disbonded, the result is a plurality of separate
electrically independent conductive portions 43b having a layer of
silicone 45 encapsulated on one side thereof, as depicted in FIG.
9. If desired, the electrode array and electrical conduction means
can undergo further processing, including further encapsulating
steps, washing and drying, to render it suitable for implantation
as an intracochlea electrode assembly.
[0220] FIG. 10 is a plan view of the raised pattern formed in an
embossing tool 70 for forming two electrode arrays for use as
cochlear implant electrode arrays.
[0221] The depicted tool 70 is adapted to form suitable embossments
in a sheet of platinum foil that are ultimately used to form
electrodes 1 to 7 of the cochlear implant electrode array. The
remaining formed electrodes are formed by separate tools and
laminated together with the electrodes formed by tool 70 to form a
complete array.
[0222] The tool 70 in addition to having suitable protrusions 71
for forming each of the electrodes 1 to 7 also has linear
protrusions 72 extending away from the electrode-forming
protrusions 71 that are used to form the respective integral
electrical conduction means for each formed electrode.
[0223] As depicted, each of the protrusions 72 eventually spiral
inwardly in ever decreasing circles. At an end distal the electrode
protrusion 71, each protrusion 72 terminates in a feedthrough
electrode protrusion 73. The distal protrusion 73 forms an
electrode for connection to the feedthrough of a
receiver/stimulator means that will preferably be electrically
connected to the electrode assembly formed using the tool.
[0224] FIGS. 11 to 15 depict a further method of forming an
electrode array according to the present invention.
[0225] In FIG. 11, the embossing tool 80 is formed from an etched
silicon wafer. The tool 80 has three groups of protrusions that
result in the formation of an equivalent number of ridges 81 in the
platinum foil sheet 43 when pressed by the tool in a manner similar
to that depicted in FIG. 3.
[0226] Once pressed, the sheet 43, with the tool 80, still in place
can have a thin layer of silicone 84 moulded thereto as depicted in
FIG. 12a. The molded layer 84 is preferably relatively thin. During
the subsequent process, a keeper 82 is used to hold the molded
layer 84 and platinum foil 43 in place. If necessary, more than one
layer can be molded or a suitable platinum/silicon adhesive layer
83 can be used to assist in bonding the layer 84 to the sheet 43
(see FIG. 12b).
[0227] As depicted in FIG. 13, the non-pressed portions 43b are
removed from the sheet 43 by an abrading or polishing step. Below
polishing line 90, the platinum sheet is removed from sheet 43 so
leaving the formed ridges 43a embedded in the silicone layer 84.
The depicted ridges 43a are electrically isolated from each other
and act as longitudinal conduction means for the formed electrodes
as discussed above.
[0228] To form a full array of electrodes for a cochlear implant
array, three laminations are required of three separately formed
smaller electrode arrays. As depicted in FIG. 14, a second set of
electrical conduction means are formed and then laid above the
first set of electrical conduction means. This process is then
again repeated to form the full array.
[0229] It is preferred during the molding process that the formed
electrode pads are recessed slightly into the surrounding silicone.
One example of how this can be achieved is depicted in FIG. 15. In
FIG. 15, the laminating die 100 includes upstanding insets 91 that
extend outwardly from the die 100 and which are aligned with the
positions of the formed electrodes 92. These insets 91 preferably
abut the electrodes 92 and so prevent the encapsulation covering
the electrodes 92 during the subsequent encapsulating process.
[0230] FIG. 15a depicts an alternative device for use in the
working of a sheet of electrically conductive material, such as
platinum foil as already described herein. The device comprises a
punch tool 95 that is adapted to be moved relative to a sheet 96,
such as that depicted in FIG. 15b. The sheet of FIG. 15b comprises
a layer of platinum foil 43 that has been mounted to a surface of a
thicker layer of silicone 96.
[0231] In the depicted example, on relative downward movement of
the punch 95, its working surface 97 serves to effectively slice or
cut portions of the platinum from the sheet 43 and drive them to
varying depths within the silicone layer 96. Due to the resilient
nature of the silicone, the silicone layer can be expected to at
least substantially close about the punched portions of the sheet
43 on relative upward withdrawal of the punch 95.
[0232] In the depicted example, the punch preferably extends
longitudinally such that during use longitudinal portions of
platinum sheet are forced into the silicone layer. This
longitudinal portions can then act as conducting wires as has been
described herein.
[0233] The depicted process described above results in the
formation of a plurality of electrode pads and integrally formed
electrical conduction means embedded within a silicone carrier. The
process is relatively straightforward and has the potential to be
automated so reducing the cost of manufacture of electrode arrays
for devices such as cochlear implants.
[0234] An alternative process for the manufacture of an electrode
array is depicted in FIGS. 17a to 24.
[0235] Current techniques for the manufacture of electrode arrays
for cochlear implant systems are highly labour intensive. This is
in the main due to the intricate nature of the array and the very
small dimensions of the array necessary to allow it to be inserted
in the scala tympani of the human cochlea. Being an implantable
device, the method of manufacture also needs to result in a
biocompatible product that is not susceptible to damage from
long-term placement in the body.
[0236] FIG. 24 is a flow chart of an example of some of the steps
of a method according to a present invention, depicted generally as
110, for forming an electrode array that is suitable for use as a
tissue-stimulating device within the human cochlea. The method 110
is more susceptible to automation that hitherto known techniques
for manufacturing cochlea implant electrode arrays.
[0237] As depicted, the method 110 firstly comprises a step 111.
Step 111 comprises coating a first surface of a sheet of platinum
with a first layer of copper or other sacrificial type material. In
the depicted method, platinum is used as it is a biocompatible
material and is a proven material for use in cochlear implants
manufactured using traditional techniques. The sheet is in the form
of a foil and has a thickness between about 10 and 50 microns. Each
sheet can have a dimension of about 50 mm.times.250 mm.
[0238] In step 111, the copper layer is plated to the first surface
or underside of the sheet in a plating bath. Prior to the first
layer being applied to the sheet, the sheet is though normally
supported in a holder. Double-sided tape or other types of
adhesives can be used to support the sheet to the holding member.
The copper layer in this example of the method can have a thickness
of about 100 microns. In another embodiment, the first layer can
comprise a layer of electrically conductive film applied to the
first surface of the sheet.
[0239] Once the first layer has been applied to the sheet, it is
preferably polished. The purpose of the polishing is to ensure that
the copper layer is as flat as possible.
[0240] The method 110 further comprises a step 112 in which an
electrode array pattern is formed in the sheet of platinum. In this
example, step 112 comprises removing portions of the platinum sheet
therefrom such that at least the desired pattern of the electrode
array and the wires remains.
[0241] In the example, step 112 comprises a process of using
electrical discharge machining (EDM) to remove unwanted portions of
the sheet. EDM relies on use of an electrode that generates a
series of electrical discharges between the electrode and the sheet
in a dielectric fluid. The electrical discharges serve to vaporise
the sheet in the region adjacent the cutting tool.
[0242] As depicted in FIGS. 17a and 18a, the size and shape of the
tip 121 of the electrode used in the EDM equipment together with
the way in which the electrode is moved around the surface of the
platinum and bought to bear on the surface, determines the size and
shape of the portion 122 of the sheet 130 to be removed from the
sheet 130 during step 112.
[0243] In the example depicted in FIG. 17a, the EDM equipment
relies on use of a single tip 121 that is brought adjacent the
sheet 130 at a number of different locations so as to remove
differing portions 122 of the sheet 130. This multiple use of the
tool serves to gradually build up the desired pattern of the
electrode array 140. As can be seen in FIG. 17d, multiple use of
the electrode 121 at different locations on the sheet 130 gradually
leads to the creation of a linear array of discrete substantially
rectangular electrodes 141 in the sheet 130, each electrode 141
having a conducting portion or wire 142 extending away therefrom to
a location distal the electrode 141. Each conducting portion or
wire can extend lineally away from its electrode.
[0244] As is depicted in FIG. 17d, the linear wires 142 are aligned
in a parallel arrangement.
[0245] FIG. 18a depicts an alternative electrode tip arrangement to
that depicted in FIG. 17a. In this arrangement, the EDM uses three
tips 121 that simultaneously operate to remove three regions 122 of
sheet 130 as depicted in FIG. 17b. As depicted in FIGS. 17c and
17d, through multiple uses of the EDM, an array of electrodes 141
and associated wires 142 are formed in the sheet 130. The advantage
of the use of the arrangement depicted in FIG. 18a is that fewer
uses of the EDM tip results in the formation of the same array
140.
[0246] Each electrode 141 formed in the sheet 130 has a size of
about 0.4 mm.sup.2-0.5 mm.sup.2.
[0247] During step 112, the EDM equipment is used in a manner such
that it removes those portions of the platinum sheet 130 where
desired and at least a portion of the copper layer that is plated
to the sheet 130 therebeneath. The EDM equipment is operated in
step 112 so as to not punch through the copper layer.
[0248] While not depicted, it will be appreciated that in step 112,
those portions of the sheet 130 to be removed can be removed by
other techniques, such as laser ablation, micro-knifing or milling
to remove unwanted portions of the sheet.
[0249] The method 110 further comprises a step 113 of coating a
second surface or topside of the platinum sheet with a layer of
resiliently flexible and relatively electrically insulating
material. This coating is made on the surface of the sheet 130
opposite to that which has received the copper layer.
[0250] In the example, step 113 comprises coating the second
surface with a layer of parylene and/or silicone. Prior to this, at
least the second surface of the sheet is cleaned and degreased.
This coating is sprayed on to the second surface of the sheet.
Other coating techniques could, however, be used including
spinning, dipping, and adhering.
[0251] The resiliently flexible layer serves to hold the sheet in
the pattern formed during step 112 during subsequent processing
steps. By being relatively electrically insulating, the layer also
acts as an insulating layer in the electrode array once formed, as
is described in more detail below.
[0252] Prior to the coating of the second surface with the layer of
resiliently flexible material, the method 110 can comprise an
additional step in which the areas of sheet removed in step 112 are
filled with a relatively electrically insulating material. The
filler can be selected from the group comprising PVA, PEG, or a
similar compound. The filler serves to prevent the layer of
resiliently flexible material flowing into the gaps in the sheet
formed by the removal of those portions of the sheet in step
112.
[0253] The method 110 comprises a still further step 114 in which
the first layer of copper is removed from the first surface of the
platinum sheet. In the depicted example, the copper layer is
removed by dissolution in a bath. Other techniques can, however, be
envisaged.
[0254] With the copper layer removed, the method 110 can still
further comprise a step 115 in which a coating is applied to the
first exposed surface or underside of the sheet 130. This coating
preferably comprises a layer of resiliently flexible material. In
the depicted example, the layer of material coated to the sheet 130
in step 115 is the same material coated to the second surface in
step 113.
[0255] During step 115, the electrodes 141 are masked to ensure
they remain uncovered with the layer of resiliently flexible
material. The wires 142 are not masked and so are coated by this
later of resiliently flexible material. In another arrangement, the
layer coated to the sheet in step 115 can be removed where
necessary, such as by laser ablation, so as to expose the covered
electrodes 141.
[0256] Following step 115, the sheet 130 is preferably trimmed to
remove the remaining portions of the sheet 130 that are not
comprising the desired electrode array 140 and wires 142 extending
therefrom. In the depicted example, the sheet 130 is trimmed with a
knife. In another embodiment, a punch and die can be used to cut
the electrode array and wires from the remaining portions of the
original sheet 130.
[0257] While the electrode tip of the EDM equipment is depicted as
having a particular arrangement depicted in FIGS. 17a and 18a, it
will be appreciated that the electrode tip can have other
arrangements. The result of one such other arrangement is depicted
in FIG. 19. In this arrangement, use of the EDM tool results in the
formation of five different electrodes sets, depicted as 151-155,
respectively, on the one platinum sheet 130.
[0258] Each of the electrode sets, and corresponding wires, are
formed in a manner such that their position with respect to each
other is predetermined and kept constant throughout the process and
in the final product.
[0259] In FIG. 19, the width of the wires of the electrode sets can
be a between about 1 and 100 microns, more preferably 1 and 70
microns, and as such traditional manufacturing methods have
problems producing such small dimensions. Further to this, the
spacing between neighbouring wires can be between about 10 and 100
microns. Still further, the wires can be disposed for at least a
portion of their lengths in a parallel arrangement.
[0260] Once each of the sets 151-155 are formed, each set can be
trimmed from the sheet 130 and stacked one above the other to form
an aligned array of electrodes 141. In the embodiment depicted in
FIG. 19, the electrode array comprises 30 electrodes, with the
array comprising 3 stacked sets of 7 electrodes, 1 set of five
electrodes above these, and 1 set of 4 electrodes on top. Other
combinations of sets can be, however, be envisaged.
[0261] While the sets of electrodes are stacked one upon the other,
it will be appreciated that the actual position of the electrodes
in each set are not necessarily vertically aligned. Rather, the set
immediately above its lower set may be laterally offset so as to
ensure the electrodes are visible from beneath the stack. A photo
depicting a part of a longitudinal array of electrodes 141 formed
using the method 110 is depicted as FIG. 20.
[0262] As depicted in FIG. 19, the wires 142 extending from each
electrode 141 are of the same length. It can, however, be envisaged
that the wires 142 could be formed with different lengths to
account for the ultimate offset present when forming the stack.
[0263] Once the stack is formed, the hitherto at least
substantially planar electrodes are preferably deformed so as to at
least partially extend in a third dimension. In a preferred
embodiment, each of the electrodes are curved out of the plane of
the wires 142 for each set of electrodes. The curvature can be
substantially semi-circular. A mandrel can be used to form the
curvature in the electrodes.
[0264] Once the electrodes 141 have been deformed to have a
substantially semi-circular curvature, each of the electrodes 141
are further folded about a longitudinal axis of the array 140. This
folding of the electrodes 141 serves to bend the electrodes around
the wires 142 of the array. The electrodes are preferably folded
together and define a lumen that extends through the array 140. An
example of the curvature of individual electrodes is depicted in
FIG. 21.
[0265] Once the electrode array 140 is complete it is encapsulated
in a further layer of a biocompatible silicone material to form a
electrode carrier member 160. Silastic MDX 4-4210 is an example of
one suitable silicone for use in the formation of the carrier
member 160.
[0266] The step of forming the carrier member 160 can comprise
mounting the array 140 in a mould and filling the mould with the
silicone and allowing it to cure. In this arrangement, the
electrodes are positioned in the mould so as to not be coated with
the silicone. In the arrangement depicted in FIGS. 21-23, the
carrier member is moulded in a spirally-curved configuration and
preferentially adopts this configuration unless straightened by the
presence of a stylet 161 or other straightening means. In FIGS. 22
and 23, the degree of curvature of the depicted carrier member is
to be taken as illustrative only. The electrode array and carrier
member may be formed and moulded, respectively, to adopt a greater
or lesser degree of curvature than that depicted when the stylet
161 is fully retracted.
[0267] In FIG. 21, it can be seen that the stylet 161 passes
through a lumen in the carrier member 160 formed by the folding of
the electrodes 141 as defined above.
[0268] While the depicted method relies on use of a layer of copper
coated to the platinum sheet, the present application is also
directed to an arrangement in which the platinum sheet is coated
with a first layer of another material that is relatively
electrically insulating. In this case, EDM cannot be used as
described above. Rather, the unwanted portions of the platinum
sheet 130 are preferably removed by another sheet portion removal
technique, such as laser cutting, micro-knifing, chemical etching,
stamping, or roller cutting. In this method, the first layer can
comprise a polymeric material, such as a polycarbonate,
polytetrafluoroethylene, polyimide, PAA, or PVA.
[0269] Use of the method 110 and the steps detailed herein results
in the formation of a carrier member 160 for a cochlear implant
system in which there has been no requirement to manually weld a
wire to each electrode of the array. This serves to streamline the
manufacturing process and allow greater automation thereof,
resulting in suitable quality carrier members at a potentially
lower cost.
[0270] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
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