Method of making an electrode array for a neural prosthetic device

Abstract

The method for manufacturing an electrode array includes forming a first insulating layer from a first non-conductive material; depositing a first conductive material over a portion of the first insulating layer by pressure-driven extrusion printing to form a first conductive layer; depositing a second non-conductive material over a portion of the first conductive layer and over an exposed portion of the first insulating layer to form a second insulating layer defining a gap exposing a portion of the first conductive layer; and depositing a second conductive material in the gap and over the exposed portion of the first conductive layer by pressure-driven extrusion printing to form a second conductive layer electrically connected to the first conductive layer, thereby forming at least one electrode of the electrode array.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 830,347, filed on April 5, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to electrode arrays and, more particularly, to a method of making an electrode array for a neuroprosthetic device. Background Art

[0004] Neuroprosthetic devices are commonly used to treat neurological diseases and disorders, such as Parkinson's disease, deafness, epilepsy, chronic pain, paralysis, and blindness. An example of a neuroprosthetic device is a cochlear implant, a medical device implanted in the cochlea of ​​a living organism. A cochlear implant includes a stimulator that generates electrical signals and an electrode array that provides electrical signals to nerve fibers in the cochlea to improve hearing.

[0005] Electrode arrays have been manufactured using a variety of manufacturing techniques, including microfabrication processes and certain direct-write printing techniques. In some cases, electrode arrays are handmade. Microfabrication processes use vapor and / or electrodeposition of materials, and then can use subtractive techniques (such as etching and machining) during microfabrication to create three-dimensional (3D) features including traces, electrode contacts, channels, etc. In some cases, the 3D features formed using subtractive techniques cannot be well defined. In addition, the deposition process tends to use undesirable gases, and the materials used during microfabrication are often more rigid and cannot withstand common flexures, bends, and / or stretching.

[0006] Screen printing is another microfabrication technique commonly used to produce electrode arrays. Although screen printing can be used to print a wide variety of materials (a wide range), it requires the use of masks, requires direct contact with a flat substrate, and is limited in forming small 3D features including traces, electrode contacts, channels, etc.

[0007] Inkjet printing is a form of direct-write printing and involves extruding material (e.g., ink) through a nozzle as the nozzle moves across a substrate to form 3D features on the substrate. Although suitable for printing electronic devices on simple planar substrates, inkjet printing is often inadequate for printing curved electrode arrays, cannot print line widths less than 30 μm with sufficient resolution, and cannot print densely weighted (heavy density) materials, thereby limiting the type and / or content of metal particles to be printed. In addition, inkjet printing is often incompatible with high viscosity silicones and fluoropolymers that are often used as structural and insulating layers in electrode arrays. Therefore, another technology is usually required to deposit high viscosity materials to form structural or insulating layers for electrode arrays.

[0008] Aerosol jet printing is another form of direct write printing and involves propelling a jet of material onto a substrate. Since aerosol jet printing is an aerodynamic flow-based technology, aerosol jet printing can produce electrode array line widths as small as 5 μm. In addition, the print head of an aerosol jet printer allows for multi-axis rotation, enabling printing on curved substrates. However, aerosol jet printing often cannot print a variety of non-conductive materials, including insulating and / or high viscosity materials, and often prints discontinuous lines, which can adversely affect the electrical continuity and conductive characteristics of the electrode array.

[0009] The present disclosure is intended to solve the above-mentioned problems. Summary of the invention

[0010] The present disclosure provides a method for manufacturing an electrode array. The method includes the following steps: forming a first insulating layer from a first non-conductive material, wherein the first insulating layer has opposite first and second surfaces; depositing a first conductive material over (or on) a portion of the second surface of the first insulating layer by pressure-driven extrusion printing to form a first conductive layer having opposite first and second surfaces, wherein the first surface of the first conductive layer faces the first insulating layer, and another portion of the second surface of the first insulating layer remains exposed; depositing a second non-conductive material over a portion of the second surface of the first conductive layer and over an exposed portion of the second surface of the first insulating layer to form a second insulating layer, the second insulating layer having opposite first and second surfaces and a gap extending between the first and second surfaces of the second insulating layer, wherein the gap exposes a portion of the second surface of the first conductive layer; depositing a second conductive material into the gap and over the exposed portion of the second surface of the first conductive layer by pressure-driven extrusion printing to form a second conductive layer, the second conductive layer being electrically connected to the first conductive layer to form at least one electrode, thereby forming an electrode array. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Advantages of the present invention will be readily appreciated as the same may be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

[0012] Figure 1 A semi-schematic partial cross-sectional perspective illustration of a portion of an auditory system of an organism and a neuroprosthetic device implanted in the cochlea of ​​the organism.

[0013] Figure 2 is a schematic perspective view of a segment of an electrode array for a neuroprosthetic device.

[0014] FIG. 3A to FIG. 3F1 is a cross-sectional schematic diagram of the steps of the method for manufacturing an electrode array according to an embodiment of the present disclosure. It should be noted that the various material layers of the electrode array and the apparatus for forming the electrode array are not drawn to scale.

[0015] Figure 4 yes Figures 3A-3F Schematic cross-sectional view of alternative steps of a method for manufacturing an electrode array as shown in . It should be noted that the various material layers of the electrode array and the apparatus used to form the electrode array are not drawn to scale.

[0016] Figure 5 is a schematic cross-sectional view of another alternative step in a method of making an electrode array. It should be noted that none of the features or individual material layers are drawn to scale. DETAILED DESCRIPTION

[0017] Referring now to the drawings, in which like reference numerals indicate like or corresponding parts throughout the several views, an embodiment of a method of manufacturing an electrode array 102 is described in detail below. The electrode array 102 formed by the method of the present disclosure can be used in a neuroprosthetic device for treating various neurological diseases and disorders. Non-limiting examples of neuroprosthetic devices include deep brain stimulators, spinal cord stimulators, retinal prostheses, cochlear prostheses, etc. For example, and as Figure 1 As shown, the electrode array 102 can be used in a cochlear prosthesis 100, which is a neuroprosthetic device that can be implanted in the cochlea 12 of a biological subject 10 (e.g., a human or animal) to treat hearing loss. At least in part due to the presence of a flexible material such as silicone in the various material layers, the electrode array 102 formed by the method of the present disclosure is flexible and elastic, and can be easily implanted into a small, curved space such as the cochlea 12 of the biological subject 10. It should be understood that the electrode array 102 can be used in any suitable stimulation device, not limited to neuroprosthetic devices. Applications of the electrode array 102 other than medical devices are also contemplated.

[0018] For medical applications, the electrode array 102 is ideally formed of a biocompatible material, ie, a material that is friendly and harmless to living tissue. In the present disclosure, the electrode array 102 formed by the method includes a biocompatible material, thereby making the electrode array 102 a biocompatible neuroprosthetic device.

[0019] Figure 2 is a schematic diagram of a prosthesis 100 including an electrode array 102. Figure 1 and Figure 2 As shown, the electrode array 102 has an interconnect region 112 and an electrode region 114. The interconnect region 112 allows the electrode array 102 to be connected to an external device (e.g., Figure 1The electrode region 114 includes a substrate 110 that supports a plurality of electrodes 116 of the electrode array 102, such as Figure 2 Best shown. Although Figure 2 102, four electrodes 116 are shown, but it should be understood that the electrode array 102 can have any number of electrodes 116. For example, in a cochlear prosthesis, the stimulator 104 operates to generate an electrical signal, and the electrode 116 operates to transmit the electrical signal to the cochlea 12 of the biological subject 10, thereby treating hearing loss. The stimulator 104 and the electrode array 102 are connected by a connector (e.g., a feed-through pin). The connector is connected to the electrodes 116 of the electrode array 102 via, for example, wires embedded in the substrate 110. Further details of the electrode array 102 are identified below in conjunction with a detailed description of a method of manufacturing the electrode array 102 and the co-pending patent application No. __ (Attorney Application No. 264.0002US2 / Atty. Docket No. 264.0002US2), the contents of which are incorporated herein by reference in their entirety.

[0020] Refer to Figure 3 and Figure 4 The details of the method for manufacturing the electrode array 102 are described. Figure 3A As shown, the method includes the step of providing a mold (step 300). The mold generally includes a top portion and a bottom portion relative to each other, and the bottom portion 200 of the mold is Figure 3A In the illustrated embodiment, the bottom portion 200 of the mold defines a cavity 201. As described below, the electrode array 102 is constructed within the cavity 201 of the mold 200.

[0021] refer to Figure 3B The method includes the step of forming a first insulating layer 202 from a first non-conductive material, wherein the first insulating layer 202 has opposite first and second surfaces 204 and 206. In one embodiment, the forming step is performed by depositing the first non-conductive material into the cavity 201 of the bottom portion 200 of the mold to form the first insulating layer 202, wherein the first surface 204 of the first insulating layer 202 faces the bottom portion 200 of the mold (step 302). The first insulating layer 202 is formed Figure 2 A portion of a substrate 110 of an electrode array 102 is shown.

[0022] The first non-conductive material is an electrically insulating material and is biocompatible. In one embodiment, the first non-conductive material has at least 1x10 11ohm·m resistivity. Non-limiting examples of biocompatible non-conductive materials include silicones, fluoropolymers (e.g., polytetrafluoroethylene), oxides, pre-stretched elastomers, poly(p-xylene), polyimides, polyurethanes, and combinations thereof. In particular embodiments, the non-conductive material is silicone or a combination of silicones. In alternative embodiments, the non-conductive material may be one or more silicones combined with another biocompatible non-conductive material. It is also contemplated to use a biocompatible non-conductive material other than silicone as the first conductive material.

[0023] The first insulating layer 202 can have any suitable thickness. For example, the first insulating layer 202 can have a thickness suitable for providing support for subsequent layers of the electrode array 102. In one embodiment, the first insulating layer 202 has a thickness of up to about 250 μm (μm). In another embodiment, the first insulating layer 202 has a thickness of about 10 to about 250 μm. In another embodiment, the first insulating layer 202 has a thickness of about 10 to about 60 μm. In yet another embodiment, the first insulating layer 202 has a thickness of about 10 to about 40 μm.

[0024] The first non-conductive material is deposited using any suitable additive manufacturing process or technique. In one embodiment, the deposition of the first non-conductive material is performed by printing. For example, the bottom portion 200 of the mold can be transferred to a print table of a suitable printer, and the first non-conductive material is printed into the cavity 201 of the bottom portion 200 of the mold. In one embodiment, the deposition of the first non-conductive material is accomplished using pressure-driven extrusion printing, which is a form of direct write printing used to form the first insulating layer 202. In another embodiment, the deposition of the first non-conductive material is performed by three-dimensional printing, which is an additive manufacturing process in which material is deposited into the cavity 201 of the bottom portion 200 of the mold in a single layer or multiple layers. In one embodiment, a three-dimensional (3D) structure including one or more 3D features can be formed by continuously adding layers of the first non-conductive material through multiple passes of the printer.

[0025] In one embodiment, the system is available from nScrypt Inc. (Orlando, FL). The printer performs printing on the first non-conductive material. The printer is a pressure-driven extrusion printing device, wherein a first non-conductive material is extruded in a liquid state through a print nozzle of the printer. The printer includes at least one print head defining a print nozzle. In one embodiment, the printer has a first print head and a second print head, wherein each print head defines a nozzle. The nozzle of the first print head is configured to extrude one or more non-conductive materials for forming the first insulating layer 202 and the second insulating layer 218 of the electrode array 102. The nozzle of the second print head is configured to extrude one or more conductive materials for forming the first conductive layer 208 and the second conductive layer 228 described below of the electrode array 102. Each nozzle has an orifice having a diameter of about 10 to 500 μm. In one embodiment, the nozzle of the printer has an orifice of about 10 to about 125 μm. In addition, the nozzle of the printer can have any suitable configuration. In one embodiment, the orifice of the nozzle for the non-conductive material is smaller than the orifice of the nozzle for the conductive material. For example, the diameter of the orifice of the nozzle for the non-conductive material can be about 75 μm, and the diameter of the orifice of the nozzle for the conductive material can be about 125 μm.

[0026] Printing embodiments of the first non-conductive material including silicone often presents challenges because silicone has a room temperature curing time of several hours. Figure 4 One way to overcome this challenge is to form a non-conductive support 203 having a desired configuration and then construct the electrode array 102 on the support 203. The support 203 is formed of a non-conductive material, such as a first non-conductive material used to form the insulating layer 202. The support 203 can have any suitable configuration and size and serves as a platform on which the electrode array 102 is constructed. As further described below, once the electrode array 102 has been constructed or formed, the support 203 can be removed from the electrode array 102.

[0027] The support member 203 may be formed when constructing the electrode array 102. For example and with continued reference to Figure 4, the method includes the steps of depositing a first portion of a first non-conductive material by any suitable additive manufacturing process to form a support 203, and then depositing a second portion of the first non-conductive material by printing over the deposited first portion to form a first insulating layer 202. In one embodiment, the first portion of the first non-conductive material is also deposited by printing to form the support 203. Typically, the first portion of the first non-conductive material is larger than the second portion of the first non-conductive material. In other words, a bulk or majority of the non-conductive material is deposited to form the support 203, and then the remaining portion of the non-conductive material is deposited over the first portion to form the first insulating layer 202 of the electrode array 102. During the second portion, at least one layer of the remaining portion of the non-conductive material may be printed by at least one pass of the printer. In one embodiment, the deposition (e.g., printing) of the first portion and the second portion of the first non-conductive material is completed at any suitable rate, for example, at a rate of about 10 to about 20 mm / s. The deposition of the first non-conductive material may also be completed at a pressure of less than 60 psi.

[0028] Other ways of overcoming the challenges of printing silicone are also envisioned, such as heating the printer while printing to cure the first non-conductive material or printing directly into the cavity 201 of the curved bottom portion 200 of the mold to prevent fluid flow before curing.

[0029] Once the first and second portions of the deposition step 302 are completed, the method further includes the step of curing the first and second portions of the first non-conductive material during or after the step of depositing the second portion of the first non-conductive material to solidify the support 203 and the first insulating layer 202. The first and second portions may be cured simultaneously or separately. Curing may be accomplished using a hot plate or oven at any suitable curing temperature for a predetermined period of time. For silicone, curing may be accomplished, for example, at a temperature of up to about 160° C. for 1 to about 15 minutes. Alternatively, curing may be accomplished during printing of the first and second portions of the non-conductive material.

[0030] It is worth noting that Figure 3B The step 302 shown in FIG. 1 shows an embodiment in which the electrode array 102 is constructed in the cavity 201 of the bottom portion 200 of the mold without forming the support 203. In this embodiment, all the first non-conductive material deposited into the cavity 201 of the bottom portion 200 of the mold is used to form the first insulating layer 202.

[0031] In one embodiment, the method includes the step of forming a non-conductive ink including a first non-conductive material and a curing agent. In one embodiment, the non-conductive ink also includes a solvent (such as but not limited to xylene, toluene, light petroleum, mineral spirits, chlorinated hydrocarbons, and combinations thereof) and optionally one or more additives. Figure 3B In the illustrated embodiment, the step of forming the first insulating layer includes printing a non-conductive ink into the cavity 201 of the bottom portion 200 of the mold using a suitable printer (e.g., a pressure-driven extrusion printer). Figure 4 In the illustrated embodiment, the step of depositing the second portion of the first non-conductive material includes depositing a non-conductive ink over the deposited first portion of the first non-conductive material by printing to form the first insulating layer 202. During printing, the non-conductive ink is printed onto the second section 210 using the pressure-driven extrusion printer described above.

[0032] In alternative embodiments, other additive manufacturing processes may be used to complete the step of depositing the first non-conductive material to form the first insulating layer 202 .

[0033] In one embodiment, the first insulating layer 202 may include one or more 3D features, such as one or more channels or other structures that facilitate surgical placement or implantation of the prosthesis into the biological body 10. In addition, the second surface 206 of the first insulating layer 202 may be roughened to improve adhesion to subsequently formed layers, such as the first conductive layer 208 of the electrode array 102. Other features may include a wavy surface profile to enhance the ability of the electrode array 102 to stretch without adversely affecting the performance of the conductive features of the electrode array 102 and / or the first insulating layer 202 may be pre-stretched to enhance the elasticity of the electrode array 102. These features may be obtained during the printing of the first non-conductive material, for example by utilizing a mapping feature of a printer.

[0034] refer to Figure 3C The method further includes the step of depositing a first conductive material on a portion 210 of the second surface 206 of the first insulating layer 202 by pressure-driven extrusion printing to form a first conductive layer 208, the first conductive layer 208 having opposite first and second surfaces 212 and 214, wherein the first surface 212 of the first conductive layer 208 faces the first insulating layer 202 and another portion 216 of the second surface 206 of the first insulating layer 202 remains exposed (step 304). In one embodiment, the printing of the first conductive material utilizes the above The printer is executed, wherein the first conductive material is printed through the second nozzle. Again, the orifice of the nozzle for the first conductive material is larger than the nozzle for printing the non-conductive material. Although the nozzle can have any suitable configuration (as previously described), the second nozzle for printing the first conductive material can have a chamfered (chamfered) configuration. Chamfered nozzles are desirable to prevent metal particles of the conductive material from agglomerating, thereby reducing waste.

[0035] When printing through a nozzle having an orifice with a diameter of 75 μm, printing the first conductive material to form the first conductive layer 208 can be completed at a rate of about 1 to about 50 mm / s. In another embodiment, when printing through a nozzle having an orifice with a diameter of 75 μm, printing the first conductive material is completed at a rate of about 1 to about 15 mm / s. The formed first conductive layer 208 can have any suitable thickness. In one embodiment, the thickness of the first conductive layer 208 is about 10 to about 100 μm. In another embodiment, the thickness of the first conductive layer 208 is about 10 to about 50 μm. In yet another embodiment, the thickness of the first conductive layer 208 is about 20 to about 30 μm. In addition, printing the first conductive layer 208 can be completed at a pressure of less than 100 psi.

[0036] In one embodiment, the step of depositing a first conductive material includes forming a first conductive layer 208 having a plurality of 3D conductive features. The 3D conductive features include, for example, electrode contacts, traces, or interconnects for connecting the electrode array 102 to the stimulator 104 via the connector 106. Surface mapping can be used to determine the step height and surface roughness of the surface to ensure that the nozzle of the printer maintains a consistent distance from the surface during printing.

[0037] Pressure driven extrusion printing technology allows for precise formation of 3D conductive features. In addition, pressure driven extrusion printing reduces time and cost by eliminating additional process steps such as various subtractive manufacturing processes (e.g., etching or machining) used to form 3D conductive features. Pressure driven extrusion printing can be repeated multiple times to form multiple layers of conductive material that together form the first conductive layer 208 including one or more 3D conductive features.

[0038] In another embodiment, the method includes patterning all portions of the second surface 214 of the first conductive layer 208 except the exposed portion 217 (this is combined with the following steps 306 and Figure 3D 208) to form a plurality of 3D conductive features. The patterning may be accomplished using any suitable patterning technique known in the industry (e.g., by using a stripping process of a photoresist). Further processing of the first conductive layer 208 using one or more subtractive techniques may also be employed to further define the configuration of the 3D conductive features. Alternatively, microfabrication techniques such as chemical and / or physical deposition processes may be used to define the configuration of the 3D conductive features. For example, laser etching may be used to form individual traces in the first conductive layer 208.

[0039] In one embodiment, the method includes the step of forming a first conductive ink, the first conductive ink including a first conductive material disposed in a carrier. The conductive material of the first conductive ink includes conductive particles that are also biocompatible. Typically, the conductive particles have a diameter of less than 1x10 -7 ohm·m resistivity. Non-limiting examples of conductive particles include medical grade platinum particles, silver particles, copper particles, gold particles, chromium particles, titanium particles, iridium particles, stainless steel particles, conductive polymers, carbon nanotubes, and combinations thereof. Typically, the particles have an effective particle size of less than 1 μm and may be referred to as nanoparticles. In one embodiment, the particles have an effective particle size of about 50 nm to about 1 μm. Alternatively, the particles may have an effective particle size of up to about 10 μm. In one embodiment, the conductive material includes platinum particles, and the first conductive ink may be referred to as platinum ink. In another embodiment, the platinum particles are optimized by including platinum particles of different shapes, sizes, and / or concentrations to obtain excellent electrical properties, such as charge storage capacity, impedance, etc.

[0040] In one embodiment, the carrier is or includes silicone, such as polydimethylsiloxane, which imparts elasticity to the first conductive ink. Silicone is usually used together with a curing agent. In another embodiment, the carrier also includes silicone and optionally includes one or more traditional solvents (such as toluene, heptane, etc.). Siloxane is used to reduce the viscosity of the first conductive ink, and compared with traditional solvents, it tends to evaporate slowly, thereby maintaining ink consistency during printing. Non-limiting examples of suitable silicones for the first conductive ink include cyclosiloxanes (such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, etc.) and linear siloxanes (such as hexamethyldisiloxane, octamethyltrisiloxane, etc.). One or more additives (such as surfactants, etc.) can also be used in the first conductive ink.

[0041] The first conductive ink is formed by combining a conductive material, a silicone resin, a siloxane, and optionally one or more additives. For example, the combination can be accomplished by mixing the conductive material, the silicone resin, and the siloxane (and the additives) using ultrasonic treatment (sonic wave fragmentation), planetary centrifugal mixing, roll-to-roll grinding, and the like. Other methods of combining the components of the first conductive ink known in the art are also contemplated. Once the first conductive ink is formed, the step of depositing the first conductive material is further defined as depositing the first conductive ink over a portion 210 of the second surface 206 of the first insulating layer 202. In addition, the first conductive ink is cured, which can be accomplished during printing or after printing using an oven, and the like.

[0042] In one embodiment, the formation of 3D conductive features can be controlled during printing. One way to control the formation of 3D conductive features is to control the settings and / or availability of the printer. For example, the deposition of the first conductive material is formed using a printer and includes a step of depositing the first conductive material onto the second surface 206 of the first insulating layer 202 using multiple passes, varying speeds, varying pressures, or a combination thereof of the printer to form a first conductive layer 208, wherein the first conductive layer 208 has multiple thicknesses defining multiple 3D conductive features. For example, the 3D conductive features at the locations where the electrode contacts will be formed can be thicker than the 3D conductive features at other locations (e.g., 3D conductive features extending to the stimulator 104 of the neuroprosthetic device 100). In addition, the 3D conductive features can be corrugated to enhance the flexibility of the electrode array 102 without significant loss of conductivity. Another way to control the formation of 3D conductive features is to control the components of the first conductive ink. For example, during the deposition of the first conductive ink, the method includes a step of changing the particle density, viscosity, or a combination thereof of the first conductive ink to form a first conductive layer 208 having the multiple thicknesses defining the multiple 3D conductive features.

[0043] refer to Figure 3D The method further includes a step of depositing a second non-conductive material over at least a portion 226 of the second surface 214 of the first conductive layer 208 and over one or more exposed portions 216 of the second surface 206 of the first insulating layer 202 to form a second insulating layer 218 (step 306), wherein the second insulating layer 218 has opposite first and second surfaces 220, 222 and a gap 224 extending between the first surface 220 and the second surface 222. During step 306, the method includes embedding the portion 210 of the first conductive layer 208 between the second surface 206 of the first insulating layer 202 and the first surface 220 of the second insulating layer 218.

[0044] The gap 224 exposes a portion 217 of the second surface 214 of the first conductive layer 208. The portion 217 of the second surface 214 remains unpatterned. As described below, a second conductive layer 228 is deposited on the portion 217 of the second surface 214 of the first conductive layer 208 to form the electrodes 116 of the electrode array 102.

[0045] In one embodiment, the second non-conductive material deposited during step 306 has the same composition as the first non-conductive material deposited during step 302. In addition, the second non-conductive material can be deposited using the same deposition technique as previously described for depositing the first non-conductive material in step 302 to form the first insulating layer 202. The formed second insulating layer 218 can have any suitable thickness. In one embodiment, the second insulating layer 218 has a thickness of up to about 250 μm. In another embodiment, the thickness of the second insulating layer 218 is about 10 to about 250 μm. In another embodiment, the thickness of the second insulating layer 218 is about 10 to about 60 μm. In yet another embodiment, the thickness of the second insulating layer 218 is about 10 to about 50 μm. In addition, the thickness of the second insulating layer 218 can be the same as or different from the thickness of the first insulating layer 202. The combination of the first insulating layer 202 and the second insulating layer 218 forms the substrate 110 and is suitable for electrically insulating the various conductive elements of the electrode array 102. Additionally, the second surface 222 of the second insulating layer 218 serves as a support surface for additional conductive elements (in the vertical direction) for constructing the electrode array 102 .

[0046] In one embodiment and with reference to Figure 5 , the method includes the steps of forming at least one opening 230 in the first insulating layer 202 and at least one opening 232 in the second insulating layer 218. The openings 202, 232 are generally formed in the interconnection region 112 of the electrode array 102. In one embodiment, the electrode array 102 also includes a layer of conductive material 240 located between the first insulating layer 202 and the second insulating layer 218. The layer 240 includes conductive traces and / or other features connected or attached to one or more electrodes 116. Therefore and in this embodiment, the method includes the steps of forming at least one opening 230 in the first insulating layer 202, forming at least one opening 234 in the layer 240, and forming at least one opening 232 in the second insulating layer 218. The at least one opening 232 of the second insulating layer 218 is aligned with the at least one opening 230 of the first insulating layer 202 (and aligned with the at least one opening 234 of the layer 240). The aligned openings 230, 232 (and 234) are adapted to receive connectors, such as feed-through pins, of the stimulator 106 of the neuroprosthetic device 100. The forming step is accomplished using printing as described above for depositing the first and second non-conductive materials.

[0047] In one embodiment, the step of forming at least one opening 230 in the first insulating layer 202 is completed during the step of depositing the first non-conductive material. The step of forming at least one opening 232 in the second insulating layer 218 is completed during the step of depositing the second non-conductive material. In addition, the step of forming at least one opening 234 in the layer 240 is completed during the deposition of the first conductive material. The deposition step utilizes, for example, pressure-driven extrusion printing as described above. Alternatively, the openings 230, 232 (and 234) can be formed using a suitable subtractive technique, such as by forming the openings 230, 232 (and 234) using a suitable stabbing or stamping tool or device. Alternatively, conventional techniques for attaching the electrode array 102 to the stimulator 104, such as wire bonding or welding, can also be used.

[0048] Once one or more connectors have been positioned or inserted into the aligned openings 230, 232 (and 234), conductive ink may be introduced into the openings 230, 232 (and 234) to form an electrical connection between the electrode array 102 and the stimulator 104. Additional layers of conductive ink may also be added to further ensure electrical connection.

[0049] refer to Figure 3E The method further includes depositing a second conductive material into the gap 224 and over the exposed portion 217 of the second surface 214 of the first conductive layer 208 to form a second conductive layer 228 electrically connected to the first conductive layer 208 (step 308). The second conductive material is deposited into the gap 244 by using a pressure-driven extrusion printer (e.g., the above-mentioned ) is accomplished by pressure-driven extrusion printing. The second conductive layer 228 touches and / or directly contacts the first conductive layer 208 to establish an electrical connection between the two layers 208, 228. The second conductive layer 228 has opposite first and second surfaces 230, 232, wherein the first surface 230 faces the second surface 214 of the first conductive layer 208.

[0050] The printing process of step 308 can be repeated multiple times by multiple passes of the pressure-driven extrusion printer to form multiple layers of the second conductive material, thereby building up the second conductive layer 228 and forming the electrode 116. As previously described, the deposition of the second conductive material can be controlled by controlling the number of passes, changing the speed, and / or changing the pressure of the printer.

[0051] In one embodiment, the method includes the step of forming a second conductive ink comprising a second conductive material disposed in a carrier. The second conductive material comprises biocompatible conductive particles. Typically, the conductive particles have a particle size of less than 1x10 -7ohm·m resistivity. Non-limiting examples of conductive particles include medical grade platinum particles, silver particles, copper particles, gold particles, chromium particles, titanium particles, iridium particles, stainless steel particles, conductive polymers, carbon nanotubes, and combinations thereof. Similar to the first conductive ink described above, these particles have an effective particle size of less than 1 μm and can be referred to as nanoparticles. In one embodiment, the particles have an effective particle size of about 50 nm to about 1 μm. Alternatively, the particles may have an effective particle size of up to about 10 μm. In one embodiment, the second conductive material includes platinum particles, and the second conductive ink may be referred to as platinum ink. In another embodiment, the platinum particles are optimized by including platinum particles of different shapes, sizes, and / or concentrations to obtain excellent electrical properties, such as charge storage capacity, impedance, etc. In one embodiment, the first conductive material of the first conductive ink is the same as the second conductive material of the second conductive ink. In addition, the shape, size, type, and / or concentration of the first conductive material may be the same as or different from the shape, size, type, and / or concentration of the second conductive material.

[0052] In one embodiment and similar to the first conductive ink, the carrier of the second conductive ink is or includes silicone, such as polydimethylsiloxane, which gives the second conductive ink elasticity. Silicone is usually used together with a curing agent. In another embodiment, the carrier also includes siloxane and optionally includes one or more traditional solvents (such as toluene, heptane, etc.). Siloxane is used to reduce the viscosity of the second conductive ink, and compared with traditional solvents, it tends to evaporate slowly, thereby maintaining ink consistency during printing. Non-limiting examples of suitable siloxanes for the first conductive ink include cyclosiloxanes (such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, etc.) and linear siloxanes (such as hexamethyldisiloxane, octamethyltrisiloxane, etc.). One or more additives (such as surfactants, etc.) can also be used in the second conductive ink. The second conductive ink can be formed in the same manner as described above for the first conductive ink.

[0053] The resulting electrode assembly 102 is Figure 3F After forming the electrode assembly 102, and in one embodiment, the method further includes the step of depositing a third non-conductive material over the electrode assembly 102. The third non-conductive layer is used to seal and electrically isolate the electrical connections between the electrodes 116 formed in the electrode array 102 and the connectors (to be disposed in the aligned openings 230, 232 (and 234)).

[0054] The above describes steps 304 to 308 (combined Figures 3C to 3E) for forming a single electrode 116. Additional electrodes may be formed in the same manner, typically simultaneously with the formation of the electrode 116 described above. For example, several first conductive layers 208 may be deposited (by printing) along the second surface 206 of the first insulating layer 202, wherein adjacent layers 208 are spaced apart from one another. The first conductive layers 208 may be deposited in any desired pattern, such as arranged in one or more rows. The electrodes 116 are formed or constructed by the deposition of second conductive layers 218 deposited over respective first conductive layers 208 according to the pattern. Examples of this are described in Figure 2 , where the electrodes 116 are formed in a single row. The second insulating layer 218 is deposited in the same manner as previously described to embed one or more relevant portions of each of the first conductive layers 208 and electrically isolate the various electrodes 116 that are subsequently formed. Deposition of the second insulating layer 218 to form several electrodes 116 is accomplished simultaneously.

[0055] Once the electrodes 116 are formed, the electrode array 102 is removed (taken out) from the mold. Figure 3F When the support member 23 is formed, the method further comprises the step of removing the support member 203 from the second surface 204 of the first substrate layer 202 to form the electrode array 102. The support member 203 may be removed using any suitable removal technique (e.g., peeling, laser cutting, etching, etc.).

[0056] In one embodiment, the layers 202, 208, 218, 228 are cured independently during the formation of each individual layer 202, 208, 218, 228 using a printer. Alternatively, the entire electrode array 102 may be cured after forming each layer 202, 208, 218, 228. In this alternative embodiment, curing of the electrode array 102 may be accomplished using a hot plate or oven at a temperature of, for example, up to about 160°C.

[0057] Although not shown, several layers of conductive features separated by insulating layers can be deposited (by printing) on ​​top of each other to produce a high density of electrode contacts and multiple layers of conductive features. In this way, a network of conductive features can be formed to minimize device footprint and maximize functionality.

[0058] In addition, multiple electrode arrays 102 can be formed by repeating the method described in detail above. For example, the multiple electrode arrays 102 are formed by repeating each of the forming step (step 302) and the deposition step (steps 304, 306, and 308). Once formed, each electrode array 102 can then be attached to a pre-stretched elastomeric substrate.

[0059] Embodiments of the manufacturing method described in detail above can be used to form a flexible and elastic electrode array, so that the electrode array 102 can be used for a neuroprosthetic device to be implanted or used in a small curved area or space. The method advantageously utilizes pressure-driven extrusion printing, which is a direct-write printing technology, to form a 3D structure including individual material layers containing silicone to form an electrode array that can be flexed, bent, or pulled. The pressure-driven extrusion printing technology also enables the formation of small 3D features in one or more individual material layers of the electrode array.

[0060] The electrode array 102 formed by the method of the present disclosure is advantageously flexible and elastic, so that the electrode array 102 can be used for stimulation devices to be implanted or used in curved areas or spaces, such as neuroprosthetic devices. In one embodiment, the electrode array 102 can be stretched up to an elongation of about 140% while remaining conductive. The stretchability of the electrode array 102 is measured using a tensile test, in which the electrode array 102 is immersed in saline at 37°C for 10 days and removed, subjected to a percentage (%) elongation at 1 mm / s, and then maintained for 1 minute before returning to a relaxed state. The electrode array 102 is stretched until no resistance can be recorded. The electrode array 102 was also subjected to a 15 degree flexure test (where the array 102 was bent 15 degrees around a 2 mm rod at 2 Hz while being subjected to a force of 0.03 N for 100,000 cycles), a 90 degree bend test (where the array 102 was bent 90 degrees around a 5 mm rod at 1 mm / s for 10 cycles), and a 360 degree twist test (where the array 102 was twisted forward 360 degrees and then reversed 360 degrees at 1 mm / s for 50 cycles). Based at least on these results, the electrode array 102 complies with European Standard EN 45502 Parts 1 and 2 and American National Standard ANSI / AAMI C186:2017 for cochlear implant systems.

[0061] In addition, the electrodes 116 of the electrode array 102 exhibit a linear conductivity of about 30 to about 200 mC / cm at 1 kHz for a line thickness of about 25 to about 300 μm. 2 The cathode charge storage capacity of about 100 to about 5000 'Ω and the electrochemical impedance spectrum (EIS) of about 100 to about 5000 'Ω. Compared with the platinum foil electrode, the electrode 116 (formed by the first and second conductive inks including at least conductive particles and silicone resin) exhibits lower polarization. This lower voltage potential indicates that higher charge density can be input without causing tissue damage to the organism.

[0062] The present disclosure has been described in an illustrative manner, and it should be understood that the terms used are intended to have the nature of description rather than restrictive words. It will be apparent to those skilled in the art that many modifications and variations of the present disclosure are possible in accordance with the above teachings. Therefore, it should be understood that the present disclosure may be practiced in a manner different from that specifically described.

Claims

1. A method for manufacturing an electrode array, the method comprising the following steps: forming a first insulating layer from a first non-conductive material, wherein the first insulating layer has first and second opposing surfaces; Depositing a first conductive material over a portion of the second surface of the first insulating layer by pressure-driven extrusion printing to form a first conductive layer, wherein the first conductive layer has first and second opposite surfaces, the first surface of the first conductive layer faces the first insulating layer, and another portion of the second surface of the first insulating layer remains exposed; depositing a second non-conductive material over a portion of the second surface of the first conductive layer and over an exposed portion of the second surface of the first insulating layer to form a second insulating layer, wherein the second insulating layer has opposing first and second surfaces and a gap extending between the first and second surfaces of the second insulating layer, the gap exposing a portion of the second surface of the first conductive layer; as well as A second conductive material is deposited into the gap and over the exposed portion of the second surface of the first conductive layer by pressure-driven extrusion printing to form a second conductive layer electrically connected to the first conductive layer, thereby forming at least one electrode of the electrode array.

2. The method of claim 1, wherein: Each of the steps of depositing the first non-conductive material and depositing the second non-conductive material is performed by printing.

3. The method of claim 1, wherein: The step of depositing a first non-conductive material comprises the following steps: depositing a first portion of the first non-conductive material to form a support; and then A second portion of the first non-conductive material is deposited over the deposited first portion by printing to form the first insulating layer.

4. The method of claim 3, wherein: The step of depositing the second portion includes depositing the first non-conductive material over the deposited first portion by pressure driven extrusion printing.

5. The method of claim 3, wherein: The step of depositing the second portion of the first non-conductive material over the deposited first portion by printing is accomplished using a pressure driven extrusion printer operating at a rate of 1 to 50 mm / s and at a pressure of less than 100 psi.

6. The method of claim 3, further comprising the step of curing the first and second portions of the first non-conductive material to solidify the support and the first insulating layer during or after the step of depositing the second portion of the first non-conductive material.

7. The method of claim 3, wherein: After the step of depositing the second conductive material, the method further comprises the step of removing the support from the electrode array.

8. The method according to any one of claims 1 to 7, wherein: Depositing the first conductive material includes forming the first conductive layer having a plurality of first three-dimensional conductive features.

9. The method according to any one of claims 1 to 7, wherein: The step of depositing the first conductive material is performed using a pressure-driven extrusion printer, and includes the step of depositing the first conductive material onto the second surface of the first insulating layer to form the first conductive layer using multiple passes, varying speeds, varying pressures, or a combination thereof of the pressure-driven extrusion printer, wherein the first conductive layer has multiple thicknesses defining multiple first three-dimensional conductive features.

10. The method of any one of claims 1 to 7, further comprising the step of forming a first conductive ink, the first conductive ink comprising the first conductive material disposed in a carrier comprising silicone, and the step of depositing the first conductive material is further defined as depositing the first conductive ink over the portion of the second surface of the first insulating layer to form the first conductive layer, and further comprising the step of forming a second conductive ink, the second conductive ink comprising the second conductive material disposed in a carrier comprising silicone, and the step of depositing the second conductive material is further defined as depositing the second conductive ink into the gap and over the exposed portion of the second surface of the first conductive layer to form the second conductive layer electrically connected to the first conductive layer, and in, The first conductive material of the first conductive ink is the same as the second conductive material of the second conductive ink.

11. The method of claim 10, wherein: During the step of depositing the first conductive ink, the method includes the step of varying a particle density, a viscosity, or a combination thereof of the first conductive ink to form the first conductive layer, wherein the first conductive layer has a plurality of thicknesses defining a plurality of first three-dimensional conductive features.

12. The method of claim 10, wherein: Each of the first conductive material and the second conductive material is selected from platinum particles, silver particles, copper particles, gold particles, chromium particles, titanium particles, iridium particles, stainless steel particles, conductive polymers, carbon nanotubes, and combinations thereof.

13. The method of claim 12, wherein: The first conductive ink further comprises a solvent selected from the group consisting of xylene, toluene, light petroleum, mineral spirits, chlorinated hydrocarbons, and combinations thereof.

14. The method of any one of claims 1 to 7, further comprising the step of patterning all but the exposed portions of the second surface of the first conductive layer to form a plurality of three-dimensional conductive features.

15. The method of claim 14, wherein: During the step of depositing the second non-conductive material, the method includes the step of embedding the plurality of three-dimensional conductive features between the second surface of the first insulating layer and the first surface of the second insulating layer.

16. The method according to any one of claims 1 to 7, wherein: Each of the steps of depositing the first conductive material and the second conductive material is performed using a pressure-driven extrusion printer having a plurality of nozzles, wherein one nozzle of the plurality of nozzles is configured to deposit the first conductive material and the second conductive material.

17. The method of claim 16, wherein: Each of the steps of forming the first insulating layer and depositing the second non-conductive material is performed by printing using a pressure-driven extrusion printer having multiple nozzles, wherein another nozzle of the multiple nozzles is configured to deposit the first non-conductive material and the second non-conductive material.

18. The method according to any one of claims 1 to 7, further comprising the steps of: forming at least one opening in the first insulating layer; as well as forming at least one opening in the second insulating layer, wherein the at least one opening in the second insulating layer is aligned with the at least one opening in the first insulating layer, Therein, the aligned openings are adapted to receive feed-through pins of a stimulator of a neuroprosthetic device.

19. The method of claim 18, wherein: The step of forming at least one opening in the first insulating layer is performed during the step of depositing the first non-conductive material by printing.

20. The method of claim 18, wherein: The step of forming at least one opening in the first insulating layer is performed during the step of depositing the first non-conductive material by printing, and The step of forming at least one opening in the second insulating layer is completed during the step of depositing the second non-conductive material by printing.

21. The method of any one of claims 1 to 7, further comprising the step of repeating each of the forming step and the depositing step to form a plurality of electrode arrays.

22. The method of any one of claims 1 to 7, wherein: The at least one electrode is capable of stretching to an elongation of up to 140% while remaining electrically conductive.

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