U.S. patent application number 10/563866 was filed with the patent office on 2006-10-26 for conductive elements.
This patent application is currently assigned to Cochlear Limited. Invention is credited to Peter Schuller.
Application Number | 20060236532 10/563866 |
Document ID | / |
Family ID | 31983164 |
Filed Date | 2006-10-26 |
United States Patent
Application |
20060236532 |
Kind Code |
A1 |
Schuller; Peter |
October 26, 2006 |
Conductive elements
Abstract
There is disclosed a method of forming a patterned conductive
element for an implantable medical device, the method comprising
the steps of: i) depositing a supplementary material on a sheet of
conductive, parent material (1) to form a sheet of composite
material; ii) applying a carrier material over the supplementary
material of the composite sheet to form a sheet of semi-finished
material; iii) removing portions from at least the conductive
parent material of the sheet of semi-finished material in
accordance with a desired pattern corresponding to a patterned
conductive element to be formed; and iv) releasing at least the
carrier material from the sheet of semi-finished material.
Inventors: |
Schuller; Peter; (Lane Cove,
AU) |
Correspondence
Address: |
JAGTIANI + GUTTAG
10363-A DEMOCRACY LANE
FAIRFAX
VA
22030
US
|
Assignee: |
Cochlear Limited
14-16 Mars Road
Lane Cove, NSW
AU
2066
|
Family ID: |
31983164 |
Appl. No.: |
10/563866 |
Filed: |
July 9, 2004 |
PCT Filed: |
July 9, 2004 |
PCT NO: |
PCT/AU04/00920 |
371 Date: |
April 21, 2006 |
Current U.S.
Class: |
29/825 ;
29/746 |
Current CPC
Class: |
A61N 1/0551 20130101;
Y10T 156/10 20150115; Y10T 29/49126 20150115; A61N 1/05 20130101;
H01L 21/4846 20130101; A61N 1/0553 20130101; Y10T 29/49204
20150115; Y10T 29/49117 20150115; Y10T 29/49156 20150115; Y10T
156/1039 20150115; Y10T 29/53204 20150115; A61N 1/0541
20130101 |
Class at
Publication: |
029/825 ;
029/746 |
International
Class: |
B23P 19/00 20060101
B23P019/00; H01R 43/00 20060101 H01R043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 2003 |
AU |
2003903532 |
Claims
1. A power management system for supplying power to an output
circuit comprising: a plurality of rechargeable batteries; first
conversion means for converting a supply voltage to a battery
voltage to enable charging of one or more of the plurality of
rechargeable batteries; and switch means to enable a selected
battery of the plurality of rechargeable batteries to be connected
to the output circuit to enable the selected battery to be
discharged through the output circuit.
2. The system according to claim 1 wherein the switch means is
connected to the first conversion means to enable charging to the
selected battery.
3. The system according to claim 1 further comprising second
conversion means connected between the output circuit and the
switch means for converting the voltage of the selected battery to
a voltage for use by the output circuit thereby discharging the
selected battery.
4. The system according to claim 1 wherein a rechargeable battery
of the plurality of rechargeable batteries is chosen, one at a
time, in order to be charged or discharged.
5. The system according to claim 1 wherein the first conversion
means acts as the second conversion means.
6. The system according to claim 1 wherein the switch means
comprises a plurality of switches enabling connection of a
respective rechargeable battery of the plurality of rechargeable
batteries to the first conversion means and to the output
circuit.
7. The system according to claim 1 further comprising a control
unit for controlling the switch means to either enable charging or
discharging of a rechargeable battery of the plurality of
rechargeable batteries.
8. The system according to claim 7 further comprising multiplexer
means having an input connected to one terminal of each
rechargeable battery in the plurality of rechargeable batteries to
enable the voltage signals pertaining to each battery to be
selected and forwarded to an analogue to digital converter.
9. The system according to claim 8 further comprising a shunt
impedance means connected to the other terminal of each battery in
the plurality of rechargeable batteries to measure the charge
current of each battery, represented as a voltage drop across the
shunt impedance means.
10. The system according to claim 9 wherein the shunt impedance
means is connected in parallel to a shunt switch to short circuit
the shunt impedance means when the shunt impedance is not in
use.
11. The system according to claim 10 further comprising
amplification means connected between the shunt impedance means and
the multiplexer means to amplify the voltage drop across the shunt
impedance means to the input voltage range of the analogue to
digital converter.
12. The system according to claim 11 wherein the analogue to
digital converter measures individual battery voltage of any one of
the rechargeable batteries in the plurality of rechargeable
batteries and converts the measured voltage to a digital value.
13. The system according to claim 11 wherein the analogue to
digital converter measures the voltage drop across the shunt
impedance means and converts the measured voltage into a digital
value.
14. The system according to claim 13 further comprising a register
for storing information pertaining to each battery.
15. The system according to claim 14 wherein said information
comprises any one or more of charge status of each battery in the
plurality of rechargeable batteries, error status of each battery
in the plurality of rechargeable batteries or a flag identifying
whether a battery in the plurality of rechargeable batteries has
been disabled from being charged or discharged.
16. The system according to claim 15 wherein the control unit is in
communication with the register and with the analogue to digital
converter for processing signals and data from the analogue to
digital converter and from the register.
17. The system according to claim 16 wherein the control unit
periodically senses the presence of a voltage at the input to the
switch means.
18. The system according to claim 17 wherein the control unit
selects a battery of the plurality of rechargeable batteries to be
charged or discharged on the basis of information stored in the
register pertaining to a particular battery of the plurality of
rechargeable batteries.
19. The system according to claim 1 wherein the second conversion
means enables discharging of a battery of the plurality of
rechargeable batteries such that charge in the selected battery of
the plurality of rechargeable batteries is forwarded to the output
circuit.
20. The system according to claim 19 wherein the output circuit
forms part of an implantable device.
21. The system according to claim 20 wherein the implantable device
is an implantable hearing prosthesis.
22. The system according to claim 1 wherein the first conversion
means includes an inductive means, one or more switches and a
switch control unit to enable charging and/or discharging of a
selected battery of the plurality of rechargeable batteries.
23. The system according to claim 1 wherein the second conversion
means includes an inductive means, one or more switches and a
switch control unit to enable discharging of a selected battery of
the plurality of rechargeable batteries.
24. The system according to claim 1 wherein the supply voltage is
derived from an inductive means and rectified into a direct voltage
to be applied to the inductive means of the first conversion
means.
25. A method of managing the supply of power to an output circuit
in a system that includes a plurality of rechargeable batteries,
the method comprising the steps of: converting a supply voltage to
a battery voltage to enable charging of one or more of the
plurality of the rechargeable batteries; and connecting a battery
in the plurality of rechargeable batteries, using switch means, to
the output circuit to enable the connected battery to be discharged
through the output circuit.
26. The method according to claim 25 wherein the connected battery
in the plurality of rechargeable batteries is discharged to the
output circuit by converting the voltage output from the connected
battery in the plurality of rechargeable batteries to a voltage for
use by the output circuit.
27. The method according to claim 25 further comprising the step of
providing the switch means in the form of a bank of switches, one
for each rechargeable battery of the plurality of rechargeable
batteries.
28. The method according to claim 27 further comprising the step of
controlling the switch means to enable the charging or discharging
of a selected battery of the plurality of rechargeable batteries on
the basis of information stored in a register on each of the
rechargeable batteries in the plurality of rechargeable
batteries.
29. The method according to claim 28 further comprising the steps
of multiplexing and measuring parameters, such as battery voltage,
battery charge and battery current, pertaining to each rechargeable
battery in the plurality of rechargeable batteries for storage as
digital values in the register.
30. The method according to claim 29 further comprising the step of
maintaining a record in the register on the state of charge of each
rechargeable battery in the plurality of rechargeable
batteries.
31. The method according to claim 30 further comprising the step of
providing an optimum range, as a percentage value of the state of
charge, within which each rechargeable battery in the plurality of
rechargeable batteries is charged and/or discharged.
32. The method according to claim 31 further comprising the step of
disabling charging of a battery of the plurality of rechargeable
batteries where the charge of that battery of the plurality of
rechargeable batteries is above a first percentage limit of the
state of charge.
33. The method according to claim 31 further comprising the step of
terminating the discharging of a battery of the plurality of
rechargeable batteries where the charge of that battery of the
plurality of rechargeable batteries is below a second percentage
limit of the state of charge.
34. A method of forming a patterned conductive element for an
implantable medical device, the method comprising: (i) depositing a
supplementary material on a sheet of conductive, parent material to
form a sheet of composite material; (ii) applying a carrier
material over the supplementary material of the composite sheet to
form a sheet of semi-finished material; (iii) removing portions
from at least the conductive parent material of the sheet of
semi-finished material in accordance with a desired pattern
corresponding to a patterned conductive element to be formed; and
(iv) releasing at least the carrier material from the sheet of
semi-finished material.
35. A method of making a sheet of semifinished material, the method
comprising: depositing a supplementary material on a platinum sheet
to form a composite sheet; and applying a carrier material over the
supplementary material, to form a sheet of semi-finished material;
wherein the platinum sheet on the semi-finished material has a
thickness of not more than 100 .mu.m.
36. A method of forming an electrode array for an implantable
medical device, the method comprising: (i) preparing a
semi-finished sheet by depositing a supplementary material on a
platinum sheet and then applying a carrier material over the
supplementary material; (ii) removing portions from at least the
platinum sheet in accordance with a predetermined pattern, the
pattern including a linear array of stimulating or recording pads
and at least one electrical conduction means extending away from
each one of the pads to a location distal from the pad; and (iii)
releasing the carrier material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national stage application under 35
USC .sctn.371(c) of CT Application No. PCT/AU2004/000920, entitled
"Conductive Elements," filed on Jul. 9, 2004, which claims the
priority of Australian Patent No. 2003903532, filed on Jul. 9,
2003. The entire disclosure and contents of the above applications
are hereby incorporated by reference herein.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of making
conductive elements and in particular, to making patterned
conductive elements suitable for use in the manufacture of
implantable medical devices.
[0004] 2. Related Art
[0005] Medical devices that are implanted in the body are subject
to a large range of design and manufacturing constraints.
[0006] Such medical devices need to be as small as possible to
ensure they are minimally invasive. The order of size for
components can be in the micron scale.
[0007] Further, the materials from which the devices are made must
be "biocompatible". This means they must have been proven to not to
cause any significant adverse reactions in the body as a result of
contact with bodily fluids or tissue, such as tissue death, tumor
formation, allergic reaction, foreign body reaction (rejection),
inflammatory reaction, or blood clotting. Moreover,
biocompatibility means the material must not be susceptible to
damage from long-term placement in the body.
[0008] The material of choice for conductive elements in
implantable medical devices is platinum, following extensive trials
performed over the years.
[0009] Given the above requirements, the manufacturing of wiring
and connector components for implantable medical devices has
developed into a labour intensive and highly specialised craft.
[0010] One particular area where this is evident is in the field of
cochlear implants, which have been developed to provide the
sensation of hearing to hearing impaired individuals.
[0011] A cochlear implant system bypass the hair cells in the
cochlea to 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, describes
one type of cochlear implant system.
[0012] The intracochlear electrode array has generally been
manufactured by positioning a plurality of electrically conductive
platinum rings (for example, 22) in a linear array, manually
welding electrical conductive wires to each of the electrodes, and
then moulding a resiliently flexible carrier member about the
array. Each of the wires is insulated from one another to minimise
unwanted interaction between different electrical components.
[0013] In view of the high labour cost and complexity associated
with the manufacturing of the conductive elements, a number of
manufacturing alternatives have been investigated
[0014] For example, thin film technology can be used to create
electrically conductive features on insulating surfaces on a micron
scale. Such techniques include electroforming, vacuum deposition
(sputtering, evaporation), and chemical vapour deposition.
[0015] However, the metallic films produced by these techniques can
feature properties that are different from the corresponding
properties of the original, bulk materials used. This results in
the materials functioning differently from their intended purpose.
Further, the integrity of the biocompatible material must be
maintained, by avoiding or reducing any contamination introduced
during the manufacturing process.
[0016] In the case of platinum, thin film techniques tend to result
in cracking and delamination of the platinum. This forms a high
impedance path which impairs the functionality of the device.
[0017] It is desirable to provide an improved method of
manufacturing biocompatible conductive devices in the micron
scale.
SUMMARY
[0018] According to one aspect of the present invention, a method
of forming a patterned conductive element for an implantable
medical device, the method comprising:
[0019] (i) depositing a supplementary material on a sheet of
conductive, parent material to form a sheet of composite
material;
[0020] (ii) applying a carrier material over the supplementary
material of the composite sheet to form a sheet of semi-finished
material;
[0021] (iii) removing portions from at least the conductive parent
material of the sheet of semi-finished material in accordance with
a desired pattern corresponding to a patterned conductive element
to be formed; and
[0022] (iv) releasing at least the carrier material from the sheet
of semi-finished material.
[0023] According to one aspect of the present invention, there is
provided a method of managing the supply of power to an output
circuit in a system that includes a plurality of rechargeable
batteries, the method comprising the steps of:
[0024] converting a supply voltage to a battery voltage to enable
charging of one or more of the plurality of the rechargeable
batteries; and
[0025] connecting a battery in the plurality of rechargeable
batteries, using switch means, to the output circuit to enable the
connected battery to be discharged through the output circuit.
[0026] According to one aspect of the present invention, there is
provided a method of forming a patterned conductive element for an
implantable medical device, the method comprising the steps of:
[0027] (i) depositing a supplementary material on a sheet of
conductive, parent material to form a sheet of composite
material;
[0028] (ii) applying a carrier material over the supplementary
material of the composite sheet to form a sheet of semi-finished
material;
[0029] (iii) removing portions from at least the conductive parent
material of the sheet of semi-finished material in accordance with
a desired pattern corresponding to a patterned conductive element
to be formed; and
[0030] (iv) releasing at least the carrier material from the sheet
of semi-finished material.
[0031] According to another aspect of the present invention, there
is provided a method of making a sheet of semifinished material,
said method comprising the steps of:
[0032] depositing a supplementary material on a platinum sheet to
form a composite sheet; and
[0033] applying a carrier material over the supplementary material,
to form a sheet of semi-finished material;
[0034] wherein the platinum sheet on the semi-finished material has
a thickness of not more than 100 .mu.m.
[0035] According to another aspect of the present invention, there
is provided a method of forming an electrode array for an
implantable medical device, said method comprising the steps
of:
[0036] (i) preparing a semi-finished sheet by depositing a
supplementary material on a platinum sheet and then applying a
carrier material over the supplementary material;
[0037] (ii) removing portions from at least the platinum sheet in
accordance with a predetermined pattern, the pattern including a
linear array of stimulating or recording pads and at least one
electrical conduction means extending away from each one of the
pads to a location distal from the pad; and
[0038] (iii) releasing the carrier material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Various exemplary arrangements of the present disclosure
will now be described with reference to the drawings, in which:
[0040] FIG. 1A is a schematic representation of the steps required
to manufacture a semi-finished sheet material used to form an
electrode array for an implantable medical device in accordance
with one embodiment of the present invention;
[0041] FIG. 1B is a schematic representation of the steps required
to manufacture a conductive element for an implantable medical
device, starting with the semi-finished sheet material produced by
the method of FIG. 1A, in accordance with one embodiment of the
present invention;
[0042] FIG. 2A is a plan view of an electrode tip configuration of
an electric discharging machine;
[0043] FIG. 2B is a plan view of the semi-finished sheet material
showing a line vaporized by use of the tool of FIG. 2A;
[0044] FIG. 2C is a plan view of the semi-finished sheet material
of FIG. 2B showing how an electrode and adjoining wire can be
formed following a second use of the tool of FIG. 2A;
[0045] FIG. 2D is a plan view of the semi-finished sheet material
of FIG. 2B depicting how an array of electrodes and adjoining wires
are formed by a plurality of uses of the tool of FIG. 2A;
[0046] FIG. 3A is a plan view of another electrode tip of an
electric discharging machine;
[0047] FIG. 3B is a plan view of a semi-finished sheet material
showing three lines having been vaporised through use of the tool
depicted in FIG. 3A;
[0048] FIG. 3C is a plan view of the semi-finished sheet material
of FIG. 3C depicting how three electrodes and adjoining wires can
be formed following a second use of the tool of FIG. 3A;
[0049] FIG. 3D is a plan view of the semi-finished sheet material
of FIG. 3B depicting how an array of electrodes and adjoining wires
are formed by a plurality of uses of the tool of FIG. 3A;
[0050] FIG. 4 is a plan view of semi-finished sheet material
depicting how different sets of electrodes and adjoining wires can
be formed in a platinum sheet through appropriate machining;
[0051] FIG. 5 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;
[0052] FIG. 6 illustrates 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;
[0053] FIG. 7 shows the carrier member of FIG. 6 with the stylet
retracted thereby allowing the carrier member to adopt a more
pronounced curvature; and
[0054] FIG. 8 shows the carrier member of FIG. 6 with the stylet
fully retracted thereby allowing the carrier member to adopt its
fully curved configuration.
DETAILED DESCRIPTION
[0055] An example of a process used to make a semi-finished sheet
material that can later be used to form an electrode array will now
be described with reference to FIG. 1A.
[0056] Commencing with Step 11, a sheet of conductive,
biocompatible parent material 1 is sourced. This parent material is
most usually platinum, although other materials which have been
shown to possess the same properties at platinum for the purposes
of suitability as a conductive element in an implantable medical
device could also be used. Preferably, the platinum sheet is at
least 99.95% pure and has a thickness of approximately 20 .mu.m to
40 .mu.m, although other dimensions may be used. In one embodiment,
the platinum sheet has a thickness in the range of 10 .mu.m to 200
.mu.m.
[0057] Next at Step 12, a supplementary material 2 is deposited on
to one side of the platinum sheet 1 to form a new composite sheet
3. In this example, the supplementary material 2 is Titanium
Nitride (TiN) and is deposited at a thickness of around 2 .mu.m to
4 .mu.m on the upper surface. Other materials such as Tantalum
(Ta), Niobium (Nb), Nickel (Ni), or Iridium (Ir) could also be
used.
[0058] Preferably, the deposition technique uses the "Magnetron"
method, which minimizes high temperatures thought to be a
contributing factor to possible contamination.
[0059] Alternatively, the deposition technique can be performed
using vacuum cathodic arc deposition and more preferably, using a
filtered arc deposition system (FADS) that is described for example
in U.S. Pat. No. 5,433,836.
[0060] FADS uses a macroparticle filter which removes microdroplets
of cathode material emitted from the surface of the arcing cathode,
which results in a film which is free of microdroplets that are
present in films prepared by conventional arc evaporation
methods.
[0061] Vacuum deposition is the deposition of a film or coating in
a vacuum (or low-pressure plasma) environment. Generally, the term
is applied to processes that deposit atoms or molecules one at a
time, such as in physical vapor deposition (PVD) or low-pressure
chemical vapor deposition (LPCVD) processes. It can also be applied
to other deposition processes such as low-pressure plasma spraying
(LPPS).
[0062] After deposition of the supplementary material 2, Step 13 is
executed by sourcing and then applying a carrier material to the
composite sheet 3, so that the supplementary material 2 is disposed
between the parent material 1 and the carrier material 2.
[0063] In a first example, the carrier material 2 is a copper sheet
and is applied to the composite sheet 3 by co-rolling. This process
is known as "roll cladding" and effectively "cold welds" or "crush
bonds" the materials together, while reducing the overall thickness
of the rolled materials.
[0064] Alternatively, the carrier material 4 according to this
example can be electroplated to the composite sheet.
[0065] Finally, at Step 14, the semi-finished sheet material 5 is
produced having the following characteristics: TABLE-US-00001
Material Thickness Parent material Platinum 20 .mu.m to 40 .mu.m
Supplementary Titanium 0.5 .mu.m to 4 .mu.m material Nitride
Carrier material Copper 100 .mu.m
[0066] Referring now to FIG. 1B, an example of a process used to
work the sheet of semi-finished material into a patterned
conductive element for an implantable medical device will be
described. The patterned conductive element has a plurality of
conductive paths and in this example, is formed into an electrode
array for a cochlear implant. Whilst the example described below
uses a micro-machining technique to work the semi-finished
material, it is emphasised that the scope of this disclosure
includes other methods such as dry etching, where this can be
adapted to work for the required micron-scale. Similarly, other
micro-machining techniques can be used, such as milling or
cutting.
[0067] Commencing with Step 15, a portion of the sheet of
semi-finished material produced by the process of FIG. 1A is cut to
a workable size and placed on a work surface of a machine that can
perform micromachining, such as electrical discharge machining
(EDM). An example of a workable size for the semi-finished material
could be approximately 50 mm.times.250 mm, although this will
depend on the actual machine and other routine manufacturing
variations.
[0068] EDM removes material from an electrically conductive work
piece by applying a series of electrical discharges between the
electrode and the sheet in a dielectric fluid. The electrode melts
and vaporizes the work piece material but never actually touches
the work. The size and shape of the tip of the electrode, together
with the way in which the electrode is moved around and bought to
bear on the surface of the conductive work piece, determines the
size and shape of the portions that are to be removed.
[0069] At Step 16, the EDM is operated by bringing an electrode tip
21 adjacent the semi-finished sheet material. An example of the
configuration of the electrode tip 21 is shown in FIG. 2A.
[0070] The EDM process penetrates the platinum parent material, the
TiN supplementary material and at least part of the copper carrier
material. The copper carrier material is party retained during the
EDM process to enable easier, subsequent handling of the fragile
platinum material.
[0071] In the example of FIG. 2A, the EDM equipment relies on use
of a single tip 21 that is brought adjacent the sheet 22 at a
number of different locations so as to remove differing portions 23
of the sheet 22. As can be seen in FIG. 2D, multiple use of the
single tip electrode 21 at different locations on the sheet 22
gradually leads to the creation of a linear array of discrete,
substantially rectangular electrodes 25 or stimulating pads. Each
electrode has a conducting portion or wire 24 extending away to a
location distal the electrode 25.
[0072] Typically, each electrode 25 formed in the sheet 22 has a
size of about 0.4 mm.sup.2 to 0.5 mm.sup.2 and the width of each
respective wire is around 100 .mu.m or less, with a similar spacing
between neighbouring wires.
[0073] As shown in FIG. 4, the linear wires 24 are aligned in a
parallel arrangement for at least a portion of their lengths.
[0074] FIG. 3A depicts an alternative electrode tip arrangement, in
which three separate electrode tips 21 are arranged to
simultaneously remove three regions 23 of sheet 22 as depicted, for
example in FIG. 3B.
[0075] As depicted in FIGS. 3C and 3D, through multiple uses of the
EDM, an array of electrodes 25 and associated wires 26 are formed
in the sheet 22. The advantage of the use of the arrangement
depicted in FIG. 3A is that fewer uses of the EDM tip results in
the formation of the same array 24.
[0076] Having completed the `working` or micro-machining of the
semi-finished material, Step 17, is then performed t. Here, a top
side of the worked platinum sheet is cleaned and degreased in
preparation for the remaining process steps.
[0077] At Step 18, a holding layer is applied to the top side of
the worked platinum sheet to increase strength. The holding layer
is typically resiliently flexible and also relatively electrically
insulating. An example material would be parylene which is
typically applied using vapor phase deposition. Alternatively,
silicone could be sprayed on to the sheet.
[0078] If desired, the electrodes 25 can be masked before the
holding layer is applied Alternatively, the holding layer can be
later removed from the electrodes 25, such as by laser ablation, to
expose the electrodes.
[0079] At Step 19, the layer of copper carrier material is released
by way of a chemical etch, for example, by using ammonium
persulfate. Where the carrier is copper, this can be achieved by
dissolving the copper in a bath. This technique operates on the
principle that the copper layer is oxidised and hence dissolved at
a potential that is lower than the potential required to oxidise
the remaining platinum of the sheet.
[0080] Other techniques to remove the carrier material may be
utilized in alternative embodiments of the present invention,
depending on the material used.
[0081] Step 20 involves formation of the electrode array, in which
the sets of electrodes are stacked one upon the other. 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 example of a part of a longitudinal array
of electrodes 25 is depicted as FIG. 5.
[0082] As depicted in FIG. 4, the wires 24 extending from each
electrode 25 are of the same length. It can, however, be envisaged
that the wires 24 could be formed with different lengths to account
for the ultimate offset present when forming the stack.
[0083] Once the stack is formed, the electrodes are deformed so as
to at least partially extend in a third dimension. Preferably, each
of the electrodes are curved out of the plane of the wires 24 for
each set of electrodes. The curvature can be substantially
semi-circular. A mandrel can be used to form the curvature in the
electrodes.
[0084] Once the electrodes 25 have been deformed to have a
substantially semi-circular curvature, each of the electrodes 25
are further folded about a longitudinal axis of the array 21. This
folding of the electrodes 25 serves to bend the electrodes around
the wires 24 of the array. The electrodes are folded together and
define a lumen that extends through the array 21. An example of the
curvature of individual electrodes is depicted in FIG. 6.
[0085] Once the electrode array 21 is complete it is encapsulated
in a further layer of a biocompatible silicone material to form a
electrode carrier member 61. Silastic MDX 4-4210 is an example of
one suitable silicone for use in the formation of the carrier
member 61. The carrier member can be formed by mounting the array
21 in a mould and filling the mould with 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. 6-8, the carrier member is moulded in a
spirally-curved configuration and preferentially adopts this
configuration unless straightened by the presence of a stylet 60 or
other straightening means.
[0086] In FIGS. 7 and 8, the degree of curvature of the carrier
member is 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 60 is
fully retracted.
[0087] 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.
[0088] While the electrode tip of the EDM equipment is depicted as
having a particular arrangement depicted in FIGS. 2A and 3A, it
will be appreciated that the electrode tip can have other
arrangements. The result of one such other arrangement is depicted
in FIG. 4. In this arrangement, use of the EDM tool results in the
formation of five different electrodes sets, depicted as 41-45,
respectively, on the one platinum sheet.
[0089] In FIG. 6, it can be seen that the stylet 60 passes through
a lumen in the carrier member 61 formed by the folding of the
electrodes 25 as defined above.
[0090] The method described herein results in the formation of a
carrier member 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. Further, the integrity
of the platinum is maintained.
[0091] 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. For
example, the techniques described could be applied to 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; and
diagnostic devices capable of carrying out in-vivo analysis of body
parameters.
[0092] 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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