WO2025136387A1

WO2025136387A1 - Multi-material contacts and cochlear implants including the same

Info

Publication number: WO2025136387A1
Application number: PCT/US2023/085261
Authority: WO
Inventors: Nicholas V. APOLLO; Nicholas A. WISE
Original assignee: Advanced Bionics LLC
Current assignee: Advanced Bionics LLC
Priority date: 2023-12-20
Filing date: 2023-12-20
Publication date: 2025-06-26
Anticipated expiration: 2026-06-20

Abstract

A contact assembly with an electrically non-conductive member and a contact, on the electrically non-conductive member, including a tissue contact member formed from a first electrically conductive material, and a base member, formed from a second electrically conductive material that is different than the first electrically conductive material, defining an outer surface on which the tissue contact member is located and an inner surface located on the non-electrically conductive member, wherein the second electrically conductive material is more chemically active than the first electrically conductive material.

Description

MULTI-MATERIAL CONTACTS AND COCHLEAR IMPLANTS INCLUDING THE SAME

BACKGROUND 1 Field

The present disclosure relates generally to the implantable portion of implantable cochlear stimulation (or “ICS”) systems and, in particular, to electrode arrays.

2. Description of the Related Art

Referring to FIGS. 1 and 2, the cochlea 10 is a hollow, helically coiled, tubular bone (similar to a nautilus shell) that is divided into the scala vestibuli 12, the scala tympani 14 and the scala media 16 by the Reissner’s membrane 18 and the basilar membrane 20. The cochlea 10, which typically includes approximately two and a half helical turns, is filled with a fluid that moves in response to the vibrations coming from the middle ear. As the fluid moves, a tectorial membrane 22 and thousands of hair cells 24 are set in motion. The hair cells 24 convert that motion to electrical signals that are communicated via neurotransmitters to the auditory nerve 26, and transformed into electrical impulses known as action potentials, which are propagated to structures in the auditory brainstem for further processing. Many profoundly deaf people have sensorineural hearing loss that can arise from the absence or the destruction of the hair cells 24 in the cochlea 10. Other aspects of the cochlea 10 illustrated in FIGS. 1 and 2 include the medial wall 28, the lateral wall 30 and the modiolus 32.

ICS systems are used to help the profoundly deaf perceive a sensation of sound by directly exciting the intact auditory nerve with controlled impulses of electrical current. Ambient sound pressure waves are picked up by an externally worn microphone and converted to electrical signals. The electrical signals, in turn, are processed by a sound processor, converted to a pulse sequence having varying pulse widths, rates, and/or amplitudes, and transmitted to an implanted receiver circuit of the ICS system. The implanted receiver circuit is connected to an implantable lead with an electrode array that is inserted into the cochlea of the inner ear, and electrical stimulation current is applied to varying electrode combinations to create a perception of sound. The electrode array may, alternatively, be directly inserted into the cochlear nerve without residing in the cochlea. A representative ICS system is disclosed in U.S. Patent No. 5,824,022, which is entitled “Cochlear Stimulation System Employing Behind-The-Ear Sound processor With Remote Control” and incorporated herein by reference in its entirety. Examples of commercially available ICS sound processors include, but are not limited to, the Advanced Bionics™ Harmony™ BTE sound processor, the Advanced Bionics™ Naida™ BTE sound processor and the Advanced Bionics™ Neptune™ body worn sound processor.

As alluded to above, some ICS systems include an implantable cochlear stimulator (or “cochlear implant”), a sound processor unit (e.g., a body worn processor, a behind-the-ear processor or a combined headpiece/sound processor) that communicates with the cochlear implant, and a microphone that is part of, or is in communication with, the sound processor unit. The cochlear implant may include a stimulation assembly as well as a cochlear lead. The cochlear lead may include an electrode array with a flexible body and a plurality of electrically conductive contacts, a handle (or “wing”) at the basal end of the electrode array flexible body, and a tubular member that extends from the stimulation assembly to the wing. The electrode array flexible body and a tubular member are commonly formed from silicone or another suitable polymer. The stimulation assembly, which may include a platinum disc that functions as a return electrode for stimulation energy from the electrode array, is in some instances placed against the recipient’s skull (e.g., within a bone-bed recess), and the electrode array is inserted into the cochlea.

Some cochlear leads include an indifferent electrode contact on the tubular member and adjacent to the stimulation assembly. The indifferent electrode contact may be used, for example, as a backup return electrode and/or as a reference electrode during electrophysiological measurements. Such contacts are typically formed from a noble metal such as platinum due to the relatively low electrochemical impedance, relatively high conductivity, and relatively low potential for corrosion or degradation of noble metals. The present inventors have, however, determined that there are various issues associated with the use of noble metals as hermetic interfaces. For example, noble metals are relatively inert, which precludes optimal chemical bonding with the silicone of the tubular member. This can lead to gross body fluid ingress or accumulation of water vapor that condenses in voids, both of which increase the likelihood of device failure. Noble metals also tend to have lower mechanical strength, as compared with titanium and steel, which may preclude the use of certain joining or welding techniques. The present inventors have also determined that while certain chemically active metals, such as titanium and steel, provide a more suitable surface for chemical priming and adhesion to silicone, they are less than optimal in the context of a functional electrode because chemically active metals may have relatively high impedance, relatively low conductivity, relatively low biocompatibility (e.g., Grade 5 titanium), and relatively high potential for corrosion or degradation. The osseointegration propensity of titanium also makes titanium a less than optimal choice due the associated increase in impedance and difficulty moving the indifferent electrode contact should revision surgery be required.

SUMMARY

A contact assembly in accordance with at least one of the present inventions comprises an electrically non-conductive member and a contact, on the electrically non-conductive member, including a tissue contact member formed from a first electrically conductive material, and a base member, formed from a second electrically conductive material that is different than the first electrically conductive material, defining an outer surface on which the tissue contact member is located and an inner surface located on the non-electrically conductive member, wherein the second electrically conductive material is more chemically active than the first electrically conductive material. The present inventions also include medical devices, such as a cochlear implant, that include such a contact assembly.

There are a number of advantages associated with the present contact assembly. By way of example, but not limitation, the base member is better able to bond with silicone and other polymers, which allows the tissue contact member to be formed from a material that has relatively low electrochemical impedance, relatively high conductivity, and relatively low potential for corrosion or degradation.

The above described and many other features of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed descriptions of the exemplary embodiments will be made with reference to the accompanying drawings.

FIG. 1 is a section view of a cochlea.

FIG. 2 is another section view of a cochlea.

FIG. 3 is a side view of a contact in accordance with one embodiment of a present invention.

FIG. 4 is a section view taken along line 4-4 in FIG. 3.

FIG. 5 is an end view of a portion of the contact illustrated in FIG. 3.

FIG. 6 is an end view of a portion of the contact illustrated in FIG. 3.

FIG. 7 is a top view of a portion of the contact illustrated in FIG. 3.

FIG. 8 is a plan view of an implantable cochlear stimulator in accordance with one embodiment of a present invention.

FIG. 9 is a bottom view of a portion of the cochlear lead illustrated in FIG. 8.

FIG. 10 is a section view taken along line 10-10 in FIG. 9.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.

An electrically conductive contact (or “contact”) 100 in accordance with one embodiment of a present invention is generally represented by reference numeral 100 in FIGS. 3 and 4. The contact 100 may be carried on the outer surface of an electrically non-conductive member formed from silicone or another suitable polymer. For example, the contact 100 may be carried on the outer surface 242 of the cochlear implant tubular member 220 (discussed below with reference to FIGS. 8-10) to form a contact assembly 10. The contact 100 includes an outer tissue contact member 102 and an inner base member 104 that is between the tissue contact member 104 and the tubular member 220. The tissue contact member 102 is formed from a material (discussed below) that has relatively low electrochemical impedance, high electrochemical capacitance, relatively high conductivity, and relatively low potential for corrosion or degradation, while the base member 104 is formed from a material (discussed below) which is better able to bond with silicone and other polymers. A pair of seals 106 cover the portions of the base member 104 that are not covered by tissue contact member 102. The seals 106 are formed from a non-conductive material (e.g., silicone or another polymer) that tends to bond with the tubular member and base member, thereby preventing moisture ingress and augmenting the structural integrity of the mechanical connection between the contact 100 and the tubular member, while leaving the tissue contact member exposed.

Referring to FIGS. 5-7, the exemplary tissue contact member 102 is tubeshaped and has annular wall 108 that defines an inner surface 110 and an outer surface 112. The exemplary base member 104 is also tube-shaped and has annular wall 114 that defines an inner surface 116 and an outer surface 118. The combined tissue contact member 102 and base member 104 may be assembled or otherwise formed using any suitable technique, including but not limited to the exemplary techniques described below. The inner surface 112 of the tissue contact member 102 abuts the outer surface 118 of the base member 104, while the inner surface 116 of the base member abuts the outer surface 242 of the tubular member 220. The tissue contact member 102 and the base member 104 have respective longitudinal ends 120 and 122. The tissue contact member longitudinal ends 120 are located between the base member longitudinal ends 122 and, in the exemplary embodiment, the tissue contact member 102 is longitudinally centered on the base member 104. So positioned, the base member outer surface 118 has regions 124 that are not covered by the tissue contact member 102 and may be covered by the seals 106. With respect to materials, suitable electrically conductive materials for the tissue contact member 102 include noble metals, such as platinum, platinum-iridium, gold, iridium, iridium oxide, titanium nitride, rhodium and palladium, and other materials such as carbon. Suitable electrically conducive materials for the base member 104 include metals, which are more chemically active than the tissue contact member metals, such as titanium, stainless steel and molybdenum. Heavily doped semiconductor materials which form a stable surface oxide, and are more chemically active than the tissue contact member metals, are also suitable base member materials. As used herein, “chemically active” means ability to form a covalent bond with organic materials due to surface functionalities such as metal oxides and hydroxides. There are a variety of advantages associated with this combination of contact member and base member materials. By way of example, but not limitation, the noble metals are well suited for indifferent electrode functionality, while the chemically active metals will better bond the underlying tubular member than would the noble metals. Chemically active surfaces are also more compatible with primers, as compared to noble metals, which may be used to further enhance bonding to the underlying tubular member. It should be noted here that the present contacts are not limited to return, ground, reference or other indifferent functionalities, and may also be used in stimulation and/or recording applications.

The combined tissue contact member 102 and base member 104 may be assembled or otherwise formed by any suitable technique. For example, a tissue contact member tube may be interference press fitted or thermally assisted shrink fitted onto, or welded to, a base member tube. Another possibility is an internally threaded tissue contact member and an externally threaded base member. Cladding techniques may be used to form a layer of tissue contact material over the outer surface of a base member, and portions of the tissue contact material may be removed by, for example, laser ablation, chemical/electrochemical etching, reactive ion etching, polishing, or machining, to expose the outer surface regions of the base member 104 (e.g., regions 124) that are not covered by the tissue contact member. Coating methods such as electroplating, electroless plating, sputtering and electron beam deposition may be used to form a tissue contact member onto a base member ring. Also, in some instances, the base member inner surface 116 and/or exposed regions 124 may treated with surface primers (such as silanes) prior to mounting on the tubular member 220 or other polymer structure.

The combined tissue contact member 102 and base member 104 may be connected to a lead wire 126 by way of any suitable technique. Referring to FIGS. 4 and 7, the lead wire 126 may be fed through the tubular member 220, through an aperture 128, and onto the outer surface 242 where the wire may be soldered, welded or otherwise attached and electrically connected to the base member 104. In the illustrated embodiment, the base member 104 includes a slot 130 where the lead wire 126 is soldered (note solder ball 132) to the base member. Alternatively, the connection may be made under the base member 104 or at one of the longitudinal ends 122 of the base member.

As illustrated in FIGS. 3 and 4, the seals 106 in the exemplary embodiment are positioned over the base member outer surface regions 124, i.e., the regions that are not covered by the tissue contact member 102, as well as a portion of the tubular member outer surface 242. The seals 106 also abut the longitudinal ends 120 of the tissue contact member 102, but do not cover the outer surface 112. The seals 106 may be formed from materials such as silicone, polyurethane and polyamide, which form a strong bond with the tubular member 220 and the base member 104. In some embodiments, the seal material will be the same as the tubular member material. So configured, the seals 106 prevent moisture ingress and augment the structural integrity of the mechanical connection between the contact 100 and the tubular member 220.

Although the present contacts are not limited to any particular dimensions, in the exemplary context of a cochlear implant indifferent electrode the length LTC (FIG. 4) of the tissue contact member 102 may range from about 1.0 mm to about 2.0 mm and is 1.5 mm in the illustrated embodiment, and the length LB (FIG. 4) of the base member 104 may range from about 1.5 mm to about 3.5 mm and is 2.5 mm in the illustrated embodiment. As used herein in the context of dimensions, the word “about” means ±10%. Additionally, the inner diameter of the base member 104 may range from about 1 .0 mm to about 1 .5 mm and is 1 .2 mm in the illustrated embodiment, the outer diameter of the tissue contact member 102 may range from about 1 .5 mm to about 2.5 mm and is 1.75 mm in the illustrated embodiment.

The present electrically conductive contacts, such as the contact 100, may be employed in a variety of medical devices. One example of such a medical device is an implantable cochlear stimulator (or “cochlear implant”). To that end, and referring to FIGS. 8-10, an exemplary cochlear implant 200 includes stimulation assembly 202 and a cochlear lead 204. The stimulation exemplary assembly 202 includes a flexible housing 206 formed from a silicone elastomer or other suitable material, a processor assembly 208 with a stimulation processor within a titanium case 209, an antenna 210 that may be used to receive data and power by way of an external antenna that is associated with, for example, a sound processor unit, and a positioning magnet 212 located within a magnet pocket 214. The magnet 212 is used to maintain the position of a sound processor headpiece over the antenna 210. The cochlear implant may, in some instances, be configured in a manner that facilitates magnet removal and replacement. Here, the housing 206 may be provided with a magnet aperture (not shown) that extends from the magnet pocket 214 to the exterior of the housing.

The exemplary cochlear lead 204 includes an electrode array 216, a wing 218 that functions as a handle for the surgeon during the implantation surgery, and a tubular member 220. The electrode array 216 in the illustrated implementation has a flexible body 222 and a plurality of electrically conductive contacts 224 (e.g., sixteen contacts) spaced along the flexible body between the tip end 226 of the flexible body and the base region 228 that is adjacent to the wing 218. The electrically conductive contacts 224 (or “contacts”) may be located inward of the flexibly body outer surface 230 and exposed by way of a corresponding plurality of contact windows (or “windows”) 232 that extend through the outer surface of the flexible body to the contacts. The contacts 224 are each connected to a respective lead wire 234 that extends through the flexible body 222. In some instances, the flexible body 222 may include a depth (or “cochleostomy”) marker 236 that is a predetermined distance from the tip end 226. In addition to functioning as a handle, the wing 218 provides tension relief for the lead wires 234 that do not run straight through the wing. The lead wires 234 also extend through the tubular member 220, which may consist of tubes of different sizes, to a connector (not shown) in the housing 206. The connection between the stimulation assembly 202 and the cochlear lead 204 may be a temporary connection, whereby the stimulation assembly and a cochlear lead may be disconnected from one another (e.g., for in situ replacement of the stimulation assembly), or a permanent connection.

The exemplary cochlear implant also includes a return electrode 238, which may be a platinum disc welded to the exterior of the titanium case 209, that is exposed by way of an opening 240 in the flexible housing 206. The return electrode 238, which is connected to electronics within the case 209 (e.g., the ground portion) and provides a return path for stimulation signals emitted by contacts 224. The contact 100 is positioned on the outer surface 242 of the tubular member 220 and the lead wire 126 (FIG. 4) is connected to the connector (not shown) in the housing 206. The contact 100 may function as an indifferent electrode and be used, for example, as a backup return electrode and as a reference electrode for various electrophysiological measurements (e.g., neural response imaging).

Although the present inventions are not so limited, the flexible body 222 of the exemplary electrode array 206 illustrated in FIGS. 8-10 has a non-circular shape with a flat bottom in a cross-section perpendicular to the longitudinal axis LA, which defines the length direction of the electrode array. The flexible body 222 may also be tapered, with a perimeter in a plane perpendicular to the longitudinal axis LA that is smaller at the tip end 226 than at the basal region 228. Any other suitable flexible body shape (e.g., circular or oval), with or without a flat surface, may also be employed. Suitable materials for the flexible body 222 include, but are not limited to, electrically non-conductive resilient and biocompatible materials such as liquid silicone rubber (LSR), high temperature vulcanization (“HTV”) silicone rubbers, room temperature vulcanization (“RTV”) silicone rubbers, and thermoplastic elastomers (“TPEs”). The flexible projections 108 may be molded together with, and formed from the same material as, the flexible body 222.

Suitable materials for the contacts 224 include, but are not limited to, platinum, platinum-iridium, iridium, gold and palladium. Although the present inventions are not limited to any particular electrode configuration, the exemplary contacts 224 may be generally U-shaped and may be formed by a placing a tubular workpiece into an appropriately shaped fixture, placing the end of a lead wire 136 into the workpiece, and then applying heat and pressure to the workpiece to compress the workpiece onto the lead wire. The insulation may be removed from the portion of the lead wire within the workpiece prior to the application of heat and pressure or during the application of heat and pressure. Various examples of tubular workpieces being compressed onto lead wires are described in WO2018/031025A1 and WO2018/102695A1 , which are incorporated herein by reference in their entireties. The contact windows 232 extend from the outer surface 230 of the flexible body 222 to the contacts 224, thereby exposing portions of the contacts. In the exemplary implementation, the windows 232 are the same shape and expose the same portion of the associated contacts 224.

The exemplary electrode array 216 may in some instances have preset spiral shape (e.g. a helical shape) with a tight curvature (resulting from the mold shape) in an unstressed state that corresponds to the interior geometry of the cochlea. A spiral electrode array may maintained in a straightened until it is inserted into the cochlea with a stylet (not shown) or an embedded shape memory polymer element (not show) that will soften and allow the flexible body to return to the pre-curved shape during implantation.

Although the contacts 224 are all the same size and the windows 232 are all the same size in the illustrated embodiment, the contacts and/or windows may be different in sizes and/or shapes in other implementations. For example, the contacts may be larger in the portion of the array that will be positioned in the basal region of the cochlea than the contacts in the portion that will be positioned in the apical region of the cochlea. The position of the contacts may be such that a portion of each contact is aligned with the flexible body outer surface, thereby eliminating the need for a window.

Although the inventions disclosed herein have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. For example, although described in the exemplary context of cochlear implants, the present inventions are not so limited and are applicable to implantable devices that are configured to treat other medical conditions. By way of example, but not limitation, cardiac rhythm management, deep brain stimulation. The inventions also include any combination of the elements from the various species and embodiments disclosed in the specification that are not already described. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.

Claims

We claim:

1 . A contact assembly, comprising: an electrically non-conductive member; and a contact, on the electrically non-conductive member, including a tissue contact member formed from a first electrically conductive material, and a base member, formed from a second electrically conductive material that is different than the first electrically conductive material, defining an outer surface on which the tissue contact member is located and an inner surface located on the non-electrically conductive member, wherein the second electrically conductive material is more chemically active than the first electrically conductive material.

2. A contact assembly as claimed in claim 1 , wherein the first electrically conductive material is a noble metal; and the second electrically conductive material is not a noble metal.

3. A contact assembly as claimed in claim 1 , wherein the first electrically conductive material is a material selected from the group consisting of platinum, platinum-iridium, gold, iridium, iridium oxide, titanium nitride, rhodium, palladium, and carbon; and the second electrically conductive material is a material selected from the group consisting of titanium, stainless steel and molybdenum.

4. A contact assembly as claimed in any one of claims 1 to 3, wherein the tissue contact member is tube-shaped; and the base member is tube-shaped.

5. A contact assembly as claimed in any one of claims 1 to 4, wherein the base member defines longitudinal ends; and the tissue contact member defines an outer surface and longitudinal ends that are located between the base member longitudinal ends, thereby defining base member outer surface regions that are not covered by the tissue contact member.

6. A contact assembly as claimed in any one of claims 1 to 5, wherein the tissue contact member is longitudinally centered on the base member.

7. A contact assembly as claimed in claim 5 or claim 6, further comprising first and second seals that cover the base member outer surface regions that are not covered by the tissue contact member and that cover adjacent portions of the electrically non-conductive member.

8. A contact assembly as claimed in claim 7, wherein the first and second seals abut respective longitudinal ends of the tissue contact member; and the first and second seals do not extend onto the tissue contact member outer surface.

9. A contact assembly as claimed in any one of claims 1 to 4, wherein the contact defines first and second longitudinal ends; and the contact assembly further comprises first and second seals respectively associated with the first and second longitudinal ends of the contact.

10. A contact assembly as claimed in any one of claims 7 to 9, wherein the electrically non-conductive member and the first and second seals are formed from the same material.

11. A contact assembly as claimed in any one of claims 7 to 9, wherein the first and second seals are formed from a material selected from the group consisting of silicone, polyurethane and polyamide.

12. A contact assembly as claimed in any one of claims 1 to 11 , wherein the electrically non-conductive member comprises an electrically non-conductive tubular member.

13. A contact assembly as claimed in claim 12, wherein the electrically non-conductive member is formed from material selected from the group consisting of silicone, polyurethane and polyamide.

14. A cochlear implant, comprising: a housing; an antenna within the housing; a stimulation processor within the housing operably connected to the antenna; a cochlear lead including an electrode array that is operably connected to the stimulation processor and a tubular member between the housing and the electrode array; and a contact assembly as claimed in any one of claims 1 to 13 on the tubular member.

15. A cochlear implant as claimed in claim 14, wherein the electrode array includes a flexible array body and a plurality of electrically conductive contacts on the flexible array body.

16. A cochlear implant as claimed in claim 15, wherein the contacts are embedded within the flexible array body; and the flexible array body includes a plurality of windows that respectively expose portions of the contacts.

17. A cochlear implant as claimed in any one of claims 14 to 16, further comprising: a titanium case in which the stimulation processor is located; and a return electrode on the exterior of the titanium case.