Implantable electrodes comprising mechanically constrained biocompatible hydrogels with conductive passthrough

Biomaterials, such as hydrogels, can be mechanically secured to an electrode of an implantable device using a non-swellable shell. Hydrogel can be applied to an electrode surface and then mechanically constrained in place by a non-swellable shell. The non-swellable material can be secured to a substrate supporting an electrode or can otherwise surround an electrode and the hydrogel. The non-swellable shell can include openings or passthroughs that allow for electrical conduction across the non-swellable shell. The hydrogel can extend out of the openings to contact adjacent biological tissue. In some cases, an outer layer of hydrogel can surround the non-swellable shell and connected to the inner layer of hydrogel through the openings of the non-swellable shell.

TECHNICAL FIELD

The present disclosure relates to medical devices generally and more specifically to coatings for implantable electrodes.

BACKGROUND

Implantable electrodes can suffer from in vivo fouling, such as due to protein adsorption to the surface of the implantable electrodes. This initial protein adsorption can trigger the beginning of an inflammatory response, which may eventually culminate as fibrotic tissue deposition at the implant site. The fibrotic tissue deposition can act as a capacitive tissue layer and can consequently lead to a gradual increase in impedance over time as the tissue continues to build. As surrounding impedance increases, the implant becomes less efficient and may require more power to operate as desired. As a result, the efficacy and/or battery lifetime of the implant may be decreased and an implant user may require follow-up surgery to replace the fouled implant.

Efforts to decrease the in vivo impedance and increase the overall lifetime of the implant can include coating the electrode in a biomaterial that resists protein adsorption, however such biomaterials can be very difficult to reliable secure to or around an electrode. Attachment can be attempted using covalent bonding between the hydrogel and an oxide layer of the electrode. However, for certain electrodes, such as noble metals, robust covalent bonding can be very challenging to achieve. These materials may not easily form an oxide layer, without which the biomaterial has no functional handle on which to reliably, chemically attach. Unreliable attachment of biomaterials can result in further problems and can result in a lower effective lifespan of the implant than desired.

DETAILED DESCRIPTION

Certain aspects and features of the present disclosure relate to mechanically securing biomaterials, such as hydrogels, to an electrode of an implantable device. The hydrogel can be mechanically secured to an electrode via anchoring features of the electrode. Anchoring features can include apertures, voids, textures, or other patterns created in or on the electrode. The hydrogel can incorporate into the anchoring features to mechanically hold the hydrogel against the electrode. The anchoring features, by being located in or on the electrode, can further increase the surface area of the electrode that is exposed to the hydrogel, which can facilitate the conduction of electrical signals between the electrode and surrounding biological tissue. The substrate supporting the electrode can include additional anchoring features that further assist in mechanically securing the hydrogel.

The hydrogel can be mechanically secured to an electrode via anchoring features of the electrode. Anchoring features can include apertures, voids, textures, or other patterns created in or on the electrode. The hydrogel can incorporate into the anchoring features to mechanically hold the hydrogel against the electrode. The anchoring features, by being located in or on the electrode, can further increase the surface area of the electrode that is exposed to the hydrogel, which can facilitate the conduction of electrical signals between the electrode and surrounding biological tissue. The substrate supporting the electrode can include additional anchoring features that further assist in mechanically securing the hydrogel.

In some cases, a flexible electrode array can include multiple electrodes. Anchoring features can be created by perforating the electrodes to create apertures. Any suitable method can be used to perforate the electrodes, such as mechanical drilling, laser drilling, laser cutting, laser ablation, or other suitable techniques. In some cases, anchoring features, such as apertures, can be formed during formation of the electrodes, such as through masking techniques. Anchoring features, such as apertures, can also be created in the substrate as well as the electrodes. A hydrogel coating precursor can be applied to the outward facing surfaces of the electrodes, and optionally substrates, as well as on the inner surfaces of the anchoring features (e.g., apertures). While apertures are described above, other anchoring features can be used, such as voids, blind holes (e.g., not through holes), hot embossing, cold embossing, bead blasting, or any other technique for creating anchoring features or increasing the surface roughness of the electrode. In some cases, an anchoring feature can be an opening that extends any depth into the electrode, such as an aperture extending through the electrode thickness or a void that extends partially through the electrode thickness. In some instances, the hydrogel coating may only be selectively applied to certain portions of the electrode array assembly (e.g. directly over one or more of the electrodes).

In some cases, the metal electrodes can be fabricated to include anchoring features. Such electrodes can take the form of mesh-like metal structures. In this manner, the starting seed metal may be patterned, for example with photolithography, and then the seed pattern mesh may be plated up to the specified thickness. In a subtractive process, a full-thickness metal may be clad onto the substrate, a high-aspect ratio electrode pattern may be defined photolithographically to the metal, the metal etched to form the mesh, and the photoresist layer removed. In any case, a variety of approaches can be used to physically anchor and/or entrap an applied hydrogel precursor so that it the hydrogel is substantially affixed to the electrode using mechanical anchoring without the need to rely primarily on covalently bonding the hydrogel to the metal. Once a hydrogel precursor is applied, it may be cross-linked in place using a flood ultraviolet (UV) system, if UV-curable, or any other suitable technique (e.g., heating to initiate a thermal polymerization of the precursor).

Certain aspects and features of the present disclosure relate to mechanically securing biomaterials, such as hydrogels, to an electrode of an implantable device using a non-swellable shell. Hydrogel can be applied to an electrode surface and then mechanically constrained in place by a non-swellable shell. The non-swellable material can be secured to a substrate supporting an electrode or can otherwise surround an electrode and the hydrogel. The non-swellable shell can include openings or passthroughs that allow for electrical conduction across the non-swellable shell. The hydrogel can extend out of the openings to contact adjacent biological tissue. In some cases, an outer layer of hydrogel can surround the non-swellable shell and connected to the inner layer of hydrogel through the openings of the non-swellable shell.

In some cases, biocompatible hydrogels may be mechanically affixed to the electrode array using a non-swellable shell. In this approach, after a first hydrogel layer is applied to the electrode array, a non-swellable and patternable secondary coating can be applied. This second, non-swellable coating can further restrict movement and/or delamination of the hydrogel from the electrode array. Any suitable non-swellable material, conformal, or biocompatible coating may be used, such as parylene C or any of the other parylene vapor deposition polymers. In cases where the hydrogel may be selectively applied to the electrode array (e.g. just over the electrode metal), existing techniques to adhere the non-swellable material (e.g., parylene) to the substrate of the electrode array can be employed, such as any suitable primer or pre-treatment to assist in chemically anchoring the non-swellable material to the substrate. While the non-swellable material may be chemically anchored to the substrate, the hydrogel layer may not necessarily be chemically anchored to the electrodes and rather may be mechanically held in place due to physical interaction with the non-swellable material. Once the non-swellable material is in place, various openings or apertures may be created in the non-swellable material through any suitable technique, such as laser ablation, mechanical drilling, milling, inductively coupled plasma (ICP) etching, or any other convenient fabrication technique. The openings may allow the hydrogel to at least partially swell up through the openings. In some cases, an additional layer of hydrogel precursor can be applied over the non-swellable material. This additional layer may entangle or otherwise form an interpenetrating network with the first layer of hydrogel through the openings in the non-swellable material, thereby locking it in place. Such a secondary hydrogel coating may improve overall fouling resistance of the electrode array and may lead to better overall performance and biocompatibility.

Certain aspects and features of the present disclosure may be especially suitable for securing biomaterials (e.g., hydrogels) to electrodes made of noble metals (e.g., platinum, gold, and palladium). In some cases, the electrodes may specifically be made of platinum or gold. Platinum or gold can be especially useful as an implantable electrode due to their high biocompatibility and ability to be surface roughened. Metal electrodes and/or electrode arrays may be fabricated in any suitable geometries. Electrodes may be fabricated on thin, flexible substrates, such as polyimide, or a liquid crystal polymer (LCP).

As used herein, references are made to securing hydrogels to electrodes, however various aspects and features the present disclosure may involve securing other biomaterials to electrodes, such as brush layers, semi-interpenetrating networks, or other natural and/or synthetic polymeric compositions. The biomaterials can be electrically conductive, such as being naturally conductive or including conductive materials incorporated therein. For example, biomaterials can include a sufficient concentration of dissolved ions suitable for providing desired electrical conductivity. Any suitable hydrogel can be used, such as a cross-linked polyethylene glycol (PEG) diacrylate. As used herein, the term hydrogel may refer to a hydrogel precursor or a hydrogel, as appropriate.

In some cases, a non-swelling or low-swelling hydrogel can be uses. In some cases, a polymerizable hydrogel precursor may contain a non-reactive diluent (e.g., glycol ethers or alcohols), which can displace a volume equal to or approximately equal to the volume of physiological fluid that would ultimately swell the biocompatible hydrogel in vivo. In this manner, the swelling forces of the biocompatible hydrogel may be controlled to limit delamination of the hydrogel coating from the electrode array.

Certain aspects and features the present disclosure allow hydrogels to be mechanically secured to electrodes without the need to rely on covalent bonding between the hydrogel and the electrode. Such mechanical bonding can provide for a more robust and reliable attachment of the hydrogel to the electrode, especially for electrodes made of noble metals. Using the techniques disclosed herein, an implant can include desirable electrode materials (e.g., noble metals) and still retain the benefit of hydrogel coatings (e.g., improved biocompatibility) that would otherwise normally be very difficult to achieve with desirable electrode materials.

The improved ability to secure the hydrogel to an electrode using the techniques disclosed herein can allow the electrode to remain implanted for longer with no or fewer negative side effects. By reducing the amount of fibrotic response around an implant using the techniques described herein, the implant may be able to continue functioning without needing to compensate for otherwise expected increases in surrounding impedance that would have otherwise occurred due to fibrotic response. Thus, the implant may be able to function for longer on the same power supply or function similarly using a smaller power supply. An implant using certain aspects and features of the present disclosure may operate for a longer lifetime than previously possible, such as 10 or 20 years, thus decreasing the need for subsequent follow-up surgeries for a user.

FIG. 1is top view of an electrode array100prior to hydrogel application according to certain aspects of the present disclosure. The electrode array100can include a plurality of electrodes102, although in some cases an array may include only a single electrode. Each electrode102can include a base layer104and an upper layer106, although in some cases an electrode102can include only a single layer of metal or more than two layers of metal. In some cases, the base layer104and upper layer106can be different metals, such as a base layer104of gold and an upper layer106of platinum (e.g., platinum iridium). As used herein, reference to metals used to form an electrode102includes suitable alloys of those metals (e.g., platinum can refer to a platinum iridium alloy). Each electrode102can have an upper surface108. While the base layer104is depicted as larger in diameter than the upper layer106, that need not be the case and each layer can be any suitable size. The electrodes102of electrode array100are depicted as circular in shape, however any suitable shaped electrodes may be used, such as square, hexagonal, or others. The spacing of electrodes can be densely and regularly spaced with or without gaps in-between.

The electrodes102of the electrode array100can be supported on a substrate110. The electrodes102can be coupled to the substrate in any suitable manner, such as formed on the substrate110, attached to the substrate110, or embedded within the substrate110. The substrate110can have an upper surface120to which the electrodes102are coupled, although electrodes102can be coupled to more than one surface of the substrate110in some cases. Electrical conductors (e.g., wires) can be embedded within the substrate110and connect the electrodes102to other equipment, such as a controller of an implant.

Electrodes102of electrode array110are depicted in a repeating pattern, however any number of electrodes102may be positioned in any suitable fashion on the electrode array110, including randomly.

FIG. 2is a partial cutaway view of the electrode array100ofFIG. 1taken along line A:A according to certain aspects of the present disclosure. The substrate110can support the electrodes102on its top surface120. Each electrode102can include a base layer104supporting an upper layer106having an upper surface108.

FIG. 3is top view of an electrode array300having anchoring features322according to certain aspects of the present disclosure. The electrode array300can be the electrode array100ofFIG. 1after anchoring features322have been formed thereon (e.g., through mechanical drilling or laser ablation). The anchoring features322can include a plurality of apertures324created through the electrodes302. In some cases, apertures324can also be created through the substrate310.

FIG. 4is a partial cutaway view of the electrode array300ofFIG. 3taken along line B:B according to certain aspects of the present disclosure. The electrode array300can include multiple anchoring features322. The electrode array300can include a one or more apertures324passing through each electrode302. In some cases, the apertures324can also pass through the substrate310. In some cases, one or more additional anchoring features326can occur on the substrate310and not on the electrodes302. The additional anchoring feature326can be an aperture that passes through the substrate310, but not the electrodes302.

FIG. 5is a partial cutaway view depicting an electrode array500having anchoring features522that are apertures524according to certain aspects of the present disclosure. The electrode array500can be electrode array300ofFIG. 3. The electrode array500can include one or more electrodes502supported by a substrate510. The electrodes502can include a base layer504and an upper layer506. The electrodes502can have a thickness512. Any suitable thickness512can be used, such as thickness between about 3 microns to about 6 microns, although other thicknesses can be used, including less than 3 microns and greater than 6 microns. In some cases, the base layer504can have a thickness516that is about three to about five microns in thickness, although other values can be used. In some cases, the upper layer506can have a thickness514that is about 0.5 to about 1 micron in thickness, although other values can be used. In some cases, the base layer504of made of gold or a gold alloy and the upper layer506is made of platinum or a platinum alloy. The electrodes502can have any suitable dimensions, such as about 500 microns to about 2 mm in diameter, although other sizes can be used.

Apertures524can be formed in the electrodes502, such as using any suitable technique. The apertures524can be any suitable size, such as approximately 5 microns to approximately 50 microns, although other ranges may be used. An aperture524can be an opening that extends entirely through a material. As used herein, aperture524extends through the electrode502. Apertures524also happen to extend through the substrate510, although that need not always be the case. In some cases, additional anchoring features526can include apertures passing through the substrate510at locations not occupied by an electrode502. The substrate510can have a thickness518of any suitable size. In some cases, substrate510is thin and flexible to facilitate maneuverability and implantation of the electrode array500.

FIG. 6is a partial cutaway view depicting an electrode array600having anchoring features622that are apertures626with applied hydrogel632according to certain aspects of the present disclosure. The electrode array600can be the electrode array500ofFIG. 5after hydrogel632has been applied thereto. The hydrogel632can be placed over the electrodes602and optionally over the substrate610. The hydrogel632can be introduced into the anchoring features622of the electrodes602(e.g., apertures624), optionally including any additional anchoring features626of the substrate610. The hydrogel632can have a total thickness630and an over-electrode thickness628. The over-electrode thickness628can represent a minimum, maximum, or average thickness of the hydrogel632as measured from the top surface608of an electrode602. The over-electrode thickness628of the hydrogel632can be any suitable thickness, such as about 10 microns to about 100 microns, although other ranges can be used. In some cases, the over-electrode thickness628of the hydrogel632is in the tens of microns.

FIG. 7is a partial cutaway view depicting an electrode array700having anchoring features722that are voids734according to certain aspects of the present disclosure. The electrode array700can be electrode array100ofFIG. 1after anchoring features722have been applied thereto. The electrode array700can include one or more electrodes702supported by a substrate710. The electrodes702can include a base layer704and an upper layer706. The electrodes702can have a thickness712. Any suitable thickness712can be used, such as thickness between about 3 microns to about 6 microns, although other thicknesses can be used, including less than 3 microns and greater than 6 microns. In some cases, the base layer704can have a thickness716that is about three to about five microns in thickness, although other values can be used. In some cases, the upper layer706can have a thickness714that is about 0.5 to about 1 micron in thickness, although other values can be used. In some cases, the base layer704of made of gold or a gold alloy and the upper layer706is made of platinum or a platinum alloy. The electrodes702can have any suitable dimensions, such as about 700 microns to about 2 mm in diameter, although other sizes can be used.

Voids734can be formed in the electrodes702, such as using any suitable technique. The voids734can be any suitable size, such as approximately 5 microns to approximately 50 microns, although other ranges may be used. A void734can extend partially into a material (e.g., into an electrode702) without extending fully through the material. As used herein, void734extends into at least a portion of electrode702. Void734can extend partially or fully through the thickness714of the upper layer706and may optionally extend partially through the thickness716of the base layer704. Any suitable technique can be used to create the voids734, such as laser ablation. In some cases, voids can also be formed in the substrate710to act as additional anchoring features. The substrate710can have a thickness718of any suitable size. In some cases, substrate710is thin and flexible to facilitate maneuverability and implantation of the electrode array700.

FIG. 8is a partial cutaway view depicting an electrode array800having anchoring features822that are voids834with applied hydrogel832according to certain aspects of the present disclosure. The electrode array800can be the electrode array700ofFIG. 7after hydrogel832has been applied thereto. The hydrogel832can be placed over the electrodes802and optionally over the substrate810. The hydrogel832can be introduced into the anchoring features822of the electrodes802(e.g., voids834), optionally including any additional anchoring features of the substrate810. The hydrogel832can have a total thickness830and an over-electrode thickness828. The over-electrode thickness828can represent a minimum, maximum, or average thickness of the hydrogel832as measured from the top surface808of an electrode802. The over-electrode thickness828of the hydrogel832can be any suitable thickness, such as about 10 microns to about 100 microns, although other ranges can be used. In some cases, the over-electrode thickness828of the hydrogel832is in the tens of microns.

FIG. 9is a partial cutaway view depicting an electrode array having anchoring features922that are surface textures936according to certain aspects of the present disclosure. The electrode array900can be electrode array100ofFIG. 1after anchoring features922have been applied thereto. The electrode array900can include one or more electrodes902supported by a substrate910. The electrodes902can include a base layer904and an upper layer906. The electrodes902can have a thickness912. Any suitable thickness912can be used, such as thickness between about 3 microns to about 6 microns, although other thicknesses can be used, including less than 3 microns and greater than 6 microns. In some cases, the base layer904can have a thickness916that is about three to about five microns in thickness, although other values can be used. In some cases, the upper layer906can have a thickness914that is about 0.5 to about 1 micron in thickness, although other values can be used. In some cases, the base layer904of made of gold or a gold alloy and the upper layer906is made of platinum or a platinum alloy. The electrodes902can have any suitable dimensions, such as about 900 microns to about 2 mm in diameter, although other sizes can be used.

Surface textures936can be formed in the electrodes902, such as using any suitable technique. The surface textures936can increase the average roughness of the upper surface908of the electrodes902. The surface textures936can have any suitable precision, such as precision from approximately 5 microns to approximately 50 microns, although other ranges may be used. A surface texture936can include elements that extend partially into the upper layer906of the electrode902. Any suitable technique can be used to create the surface textures936, such as laser ablation or electrical discharge texturing. In some cases, surface textures can also be formed in the substrate910to act as additional anchoring features. The substrate910can have a thickness918of any suitable size. In some cases, substrate910is thin and flexible to facilitate maneuverability and implantation of the electrode array900.

FIG. 10is a partial cutaway view depicting an electrode array1000having anchoring features1022that are surface textures1034, the electrode array1000including applied hydrogel1032according to certain aspects of the present disclosure. The electrode array1000can be the electrode array900ofFIG. 9after hydrogel1032has been applied thereto. The hydrogel1032can be placed over the electrodes1002and optionally over the substrate1010. The hydrogel1032can be introduced into the anchoring features1022of the electrodes1002(e.g., surface textures1036), optionally including any additional anchoring features of the substrate1010. The hydrogel1032can have a total thickness1030and an over-electrode thickness1028. The over-electrode thickness1028can represent a minimum, maximum, or average thickness of the hydrogel1032as measured from the top surface1008of an electrode1002. The over-electrode thickness1028of the hydrogel1032can be any suitable thickness, such as about 10 microns to about 100 microns, although other ranges can be used. In some cases, the over-electrode thickness1028of the hydrogel1032is in the tens of microns.

FIG. 11is a flowchart depicting a process1100for mechanically securing hydrogel to an electrode using anchoring features according to certain aspects of the present disclosure. At block1102, an electrode can be provided. In some cases, the electrode can be pre-manufactured. In some cases, the electrode can be fabricated on a substrate. At block1106, an anchoring feature can be created on the electrode. Any suitable anchoring feature can be created. Creating an anchoring feature can include creating an aperture through the electrode at block1108, creating a void on the electrode surface at block1110, or texturizing the electrode surface at block1112. In some cases, creating an anchor feature at block1106can include any combination of block1108, block1110, and block1112. In some cases, other anchoring features can be created at block1106. At block1114, hydrogel is introduced to the anchoring feature. At block1114, hydrogel can also be introduced to the electrode and optionally the substrate. In some cases, introducing hydrogel at block1114includes introducing a hydrogel precursor. In some cases, introducing hydrogel at block1114can include pre-swelling the hydrogel, such as with a material selected to be offset by physiological fluids when the implant is implanted.

FIG. 12is top view of an electrode array1200prior to hydrogel application according to certain aspects of the present disclosure. The electrode array1200can include a plurality of electrodes1202, although in some cases an array may include only a single electrode. Each electrode1202can include a base layer1204and an upper layer1206, although in some cases an electrode1202can include only a single layer of metal or more than two layers of metal. In some cases, the base layer1204and upper layer1206can be different metals, such as a base layer1204of gold and an upper layer1206of platinum (e.g., platinum iridium). As used herein, reference to metals used to form an electrode1202includes suitable alloys of those metals (e.g., platinum can refer to a platinum iridium alloy). Each electrode1202can have an upper surface1208. While the base layer1204is depicted as larger in diameter than the upper layer1206, that need not be the case and each layer can be any suitable size. The electrodes1202of electrode array1200are depicted as circular in shape, however any suitable shaped electrodes may be used, such as square.

The electrodes1202of the electrode array1200can be supported on a substrate1210. The electrodes1202can be coupled to the substrate in any suitable manner, such as formed on the substrate1210, attached to the substrate1210, or embedded within the substrate1210. The substrate1210can have an upper surface1220to which the electrodes1202are coupled, although electrodes1202can be coupled to more than one surface of the substrate1210in some cases. Electrical conductors (e.g., wires) can be embedded within the substrate1210and connect the electrodes1202to other equipment, such as a controller of an implant.

Electrodes1202of electrode array1210are depicted in a repeating pattern, however any number of electrodes1202may be positioned in any suitable fashion on the electrode array1210, including randomly.

FIG. 13is a cutaway view of the electrode array1200ofFIG. 12taken along line C:C according to certain aspects of the present disclosure. The substrate1210can support the electrodes1202on its top surface1220. Each electrode1202can include a base layer1204supporting an upper layer1206having an upper surface1208.

FIG. 14is a cutaway view depicting an electrode array1400prior to hydrogel application according to certain aspects of the present disclosure. The electrode array1400can be electrode array1200ofFIG. 12. The electrode array1400can include one or more electrodes1402supported by a substrate1410. The electrodes1402can include a base layer1404and an upper layer1406. The electrodes1402can have a thickness1412. Any suitable thickness1412can be used, such as thickness between about 3 microns to about 6 microns, although other thicknesses can be used, including less than 3 microns and greater than 6 microns. In some cases, the base layer1404can have a thickness1416that is about three to about five microns in thickness, although other values can be used. In some cases, the upper layer1406can have a thickness1414that is about 0.5 to about 1 micron in thickness, although other values can be used. In some cases, the base layer1404of made of gold or a gold alloy and the upper layer1406is made of platinum or a platinum alloy. The electrodes1402can have any suitable dimensions, such as about 500 microns to about 2 mm in diameter, although other sizes can be used.

The substrate1410can have a thickness1418of any suitable size. In some cases, substrate1410is thin and flexible to facilitate maneuverability and implantation of the electrode array1400.

FIG. 15is a cutaway view depicting an electrode array1500with an applied hydrogel layer1532according to certain aspects of the present disclosure. The electrode array1500can be electrode array1400ofFIG. 14after hydrogel1532has been applied thereto. The hydrogel1532can be applied over the electrodes1502and optionally over the substrate1510.

FIG. 16is a cutaway view depicting an electrode array1600with a non-swellable shell1638over an applied hydrogel layer1632according to certain aspects of the present disclosure. The electrode array1600can be electrode array1500ofFIG. 15after a non-swellable shell1638has been applied thereto. The non-swellable shell1638can be applied over the hydrogel layer1632and can couple to the substrate1610. The non-swellable shell1638can couple to the substrate1610at locations devoid of hydrogel (e.g., due to masking during hydrogel application). In some cases, a pre-treatment can be applied to the substrate1610to facilitate coupling of the non-swellable shell1638thereto. The non-swellable shell1638can define a cavity1642between the non-swellable shell1638and the electrodes1602, which is filled with the hydrogel1632.

FIG. 17is a cutaway view depicting an electrode array1700with a non-swellable shell1738having openings1740according to certain aspects of the present disclosure. The electrode array1700can be electrode array1600ofFIG. 16after openings1740have been formed in the non-swellable shell1738. The cavity1742defined by the non-swellable shell1638and the electrodes1602can therefore include openings1740through which hydrogel1632may pass. Any suitable number and size of openings1740can be used. The number and size of openings1740can be selected to provide sufficient mechanical retention properties while also providing sufficient electrical conductivity through the non-swellable shell1738(e.g., via hydrogel1732passing through the openings1740.

FIG. 18is a cutaway view depicting an electrode array1800with hydrogel1832exposed through openings1840in a non-swellable shell1838according to certain aspects of the present disclosure. The electrode array1800can be electrode array1700ofFIG. 17after sufficient time has passed to allow the hydrogel1832to swell through the openings1840of the non-swellable shell1838. The openings1840can therefore facilitate electrical conductivity from the outside of the non-swellable shell1838to the electrodes1802via hydrogel1832(e.g., conductive hydrogel) in the cavity1842of the non-swellable shell1838and swelling out of the openings1840of the non-swellable shell1838.

FIG. 19is a cutaway view depicting an electrode array1900with an outer hydrogel layer1946connected to an inner hydrogel layer1944through openings1940in a non-swellable shell1938according to certain aspects of the present disclosure. The electrode array1900can be electrode array1700ofFIG. 17after an outer hydrogel layer1946has been applied to the outer surface of the non-swellable shell1938. The outer hydrogel layer1946can couple to the inner hydrogel layer1944to form a uniform hydrogel mass1932that is mechanically held in place by the non-swellable shell1938embedded therein. The non-swellable shell1938can become embedded within the hydrogel1932by coupling of the outer hydrogel layer1946to the inner hydrogel layer1644through openings1940. Thus, the openings1940can facilitate electrical conductivity from the outside of the non-swellable shell1938(e.g., the outer surface of the outer hydrogel layer1946) to the electrodes1902via the hydrogel mass1932.

FIG. 20is a cutaway view depicting an electrode array2000with hydrogel2032anchored using a non-swellable shell2038and anchoring features2022of the electrodes2002that are voids2034according to certain aspects of the present disclosure. The electrode array2000can be similar to electrode array1900ofFIG. 19, but with electrodes2002having anchoring features2022that are voids2034, similar to electrodes702ofFIG. 7. Thus, the hydrogel mass2032including an outer hydrogel layer2046coupled to an inner hydrogel layer2044can be secured to the electrodes2002via the non-swellable shell2038coupled to the substrate2010as well as the anchoring features2022of the electrodes2002.

FIG. 21is a cutaway view depicting an electrode array2100with hydrogel2132anchored using a non-swellable shell2138and anchoring features2122of the electrodes2102that are apertures2124according to certain aspects of the present disclosure. The electrode array2100can be similar to electrode array1900ofFIG. 19, but with electrodes2102having anchoring features2122that are apertures2124, similar to electrodes502ofFIG. 5. Thus, the hydrogel mass2132including an outer hydrogel layer2146coupled to an inner hydrogel layer2144can be secured to the electrodes2102via the non-swellable shell2138coupled to the substrate2110as well as the anchoring features2122of the electrodes2102. In some cases, other anchoring features (e.g., surface textures936ofFIG. 9) can be used in addition to or instead of anchoring features2122.

FIG. 22is a cutaway view depicting an electrode array2200with hydrogel2232contained within a non-swellable shell2238according to certain aspects of the present disclosure. The non-swellable shell2238can surround a cross section of the electrode array2200, thereby forming a cavity2242surrounding the electrodes2202and substrate2210at that particular cross section. Thus, hydrogel2232within the cavity2242can be located adjacent the electrodes2202as well as opposite the substrate2210from the electrodes2202. The non-swellable shell2238can include openings2240through which hydrogel2232can swell out. The electrode array2200can be similar to electrode array1800ofFIG. 18, however with its non-swellable shell2238held in place relative to the substrate2210via outward pressure from the hydrogel2232within the cavity2242, rather than being directly coupled to the substrate2210.

FIG. 23is a cutaway view depicting an electrode array2300with an inner hydrogel layer2344contained within a non-swellable shell2338that is connected to an outer hydrogel layer2346through openings2340in the non-swellable shell2338according to certain aspects of the present disclosure. The non-swellable shell2338can surround a cross section of the electrode array2300, similar to the non-swellable shell2238ofFIG. 22, thereby forming a cavity2342surrounding the electrodes2302and substrate2310at that particular cross section. Thus, an inner hydrogel layer2344within the cavity2342can be located adjacent the electrodes2302as well as opposite the substrate2310from the electrodes2302. The non-swellable shell2338can include openings2340through which an outer hydrogel layer2346can couple to the inner hydrogel layer2344to form a single hydrogel mass2332. The electrode array2300can be similar to electrode array1900ofFIG. 19, however with its non-swellable shell2338held in place relative to the substrate2310via outward pressure from the inner hydrogel layer2344within the cavity2342, rather than being directly coupled to the substrate2310.

As seen inFIG. 23, openings2340are depicted in the non-swellable layer2338on both the upper side (e.g., nearest the electrodes2302) and the lower side (e.g., the side opposite the substrate2310from the electrodes2302. In some cases, openings2340are only provided in the non-swellable layer2338on the side nearest the electrodes2302. In some cases, openings2340are only provided in the non-swellable layer2338at locations adjacent the electrodes2302.

FIG. 24is a flowchart depicting a process2400for mechanically securing hydrogel to an electrode using a non-swellable layer according to certain aspects of the present disclosure. At block2402, an electrode can be provided. In some cases, the electrode can be pre-manufactured. In some cases, the electrode can be fabricated on a substrate. At optional block2404, an anchoring feature can be created on the electrode. Any suitable anchoring feature can be created. Creating an anchoring feature can include creating an aperture through the electrode at block2406, creating a void on the electrode surface at block2408, or texturizing the electrode surface at block2410. In some cases, creating an anchor feature at block2404can include any combination of block2406, block2408, and block2410. In some cases, other anchoring features can be created at block2404.

At optional block2412, the substrate can be masked, such as with a chemical or physical mask. At block2414, hydrogel can be introduced to the electrode surface. At block2414, hydrogel may also be introduced to the substrate. In cases where the substrate is masked at block2412, introducing hydrogel to the substrate at block2414can include not introducing or removing hydrogel from the portion of the substrate that was masked at block2412. In some cases, introducing the hydrogel at block2414can first include cleaning the electrodes and/or the substrate.

At block2416, a non-swellable layer is provided over the hydrogel. In some cases, the non-swellable layer is provided entirely over the hydrogel, such as seen with non-swellable layer2338ofFIG. 23. In some cases, the non-swellable layer can be coupled to the substrate at block2416, such as seen in with non-swellable layer1938ofFIG. 19. In some cases where the non-swellable layer is coupled to the substrate, providing the non-swellable layer at block2416can further include first applying a pre-treatment to the substrate and then applying the non-swellable layer to the substrate. In some cases, providing the non-swellable layer at block2416can include otherwise coupling the non-swellable layer to the substrate.

In some cases, providing the non-swellable layer at block2416can include coupling the non-swellable layer to the substrate at locations between adjacent electrodes, thus reducing electrical conductivity through the inner hydrogel layer between the adjacent electrodes.

In some cases, any sprayable hydrophobic polymer capable of having openings created therein can be used for a non-swellable layer. The term non-swellable layer can include a layer of material exhibiting no or low swelling in vivo.

At block2418, openings can be created in the non-swellable layer. Openings can be created in any suitable manner, including through photolithography, laser ablation, or other techniques. The openings can pass entirely through the thickness of the non-swellable layer. In some cases, at block2418the non-swellable layer can be surface roughened.

At optional block2420, an additional coating of hydrogel can be applied around the non-swellable layer. This overcoating of hydrogel can result in the hydrogel mass2332ofFIG. 23.

FIG. 25is a scanning electron micrograph2500depicting a first example electrode2502having hydrogel2532mechanically coupled to a textured anchoring feature according to certain aspects of the present disclosure. The electrode2502can be supported by a substrate2510and can include a base layer2504coupled to an upper layer2506. The upper layer2506can include anchoring features in the form of surface textures, such as surface textures936ofFIG. 9, into which the hydrogel2532can interdigitate. Thus, the hydrogel2532can be mechanically affixed to the electrode2502without the need to rely substantially on covalent bonds between the hydrogel2532and the metal (e.g. noble metal) of the upper layer2506of the electrode2502.

FIG. 26is a scanning electron micrograph2600depicting a second example electrode2602having hydrogel2632mechanically coupled to a textured anchoring feature according to certain aspects of the present disclosure. The electrode2602can be supported by a substrate2610and can include a base layer2604coupled to an upper layer2606. The upper layer2606can include anchoring features in the form of surface textures, such as surface textures936ofFIG. 9, into which the hydrogel2632can interdigitate. Thus, the hydrogel2632can be mechanically affixed to the electrode2602without the need to rely substantially on covalent bonds between the hydrogel2632and the metal (e.g. noble metal) of the upper layer2606of the electrode2602.

FIG. 27is a schematic diagram depicting an implantable medical device2700electrically coupled to biological tissue2752according to certain aspects of the present disclosure. The implantable medical device2700can include a controller2748coupled to an electrode array2750. The implantable medical device2700can be located within a biological cavity2754(e.g., within a body of a patient). The implantable medical device2700can be separated from an external atmosphere2756by skin2758or other tissue. The electrode array2750can be any electrode array described herein, such as electrode array2300ofFIG. 23. The electrode array2750can be coupled to the biological tissue2752using any suitable technique, such as clamps, sutures, pins, screws, adhesives, or other methods. Electrode array2750can facilitate electrical communication between the controller2748and the biological tissue2752by passing electrical signals through the electrodes and hydrogel of the electrode array2750. Thus, electrode array2750can operate to send, receive, or send and receive electrical signals to, from, or to and from biological tissue2752. Thus, electrode array2750can be suitable for use as a stimulation device, a measurement device, or any combination thereof.

The foregoing description of the embodiments, including illustrated embodiments, has been presented only for the purpose of illustration and description and is not intended to be exhaustive or limiting to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to those skilled in the art.

Example 1 is an implantable electrode array, comprising: at least one electrode comprising a conductible metal layer having one or more anchoring features; and a hydrogel layer mechanically coupled to the conductible metal layer at the one or more anchoring features.

Example 2 is the electrode array of example 1, wherein the one or more anchoring features include an aperture passing through a thickness of the at least one electrode.

Example 3 is the electrode array of examples 1 or 2, wherein the one or more anchoring features include a void having a depth that is less than a thickness of the at least one electrode.

Example 4 is the electrode array of examples 1-3, further comprising a substrate having at least one additional anchoring feature, wherein the at least one electrode is coupled to the substrate, and wherein the hydrogel layer is further mechanically coupled at the at least one additional anchoring feature.

Example 5 is the electrode array of examples 1-4, wherein the hydrogel layer comprises electrically conductive hydrogel material.

Example 6 is the electrode array of examples 1-5, wherein the hydrogel layer comprises a non-swelling hydrogel material or a low-swell hydrogel material.

Example 7 is the electrode array of examples 1-6, wherein the conductible metal layer is a noble metal.

Example 8 is the electrode array of example 7, wherein the conductible metal layer is selected from the group consisting of platinum and gold.

Example 9 is an implantable device, comprising: an electrode array positionable adjacent biological tissue, the electrode array comprising: at least one electrode comprising a conductible metal layer having one or more anchoring features; and a hydrogel layer mechanically coupled to the conductible metal layer at the one or more anchoring features, wherein the hydrogel layer is located between the at least one electrode and the biological tissue for conducting a signal between the at least one electrode and the biological tissue when the electrode array is positioned adjacent the biological tissue; and a controller electrically coupled to the electrode array.

Example 10 is the implantable device of example 9, wherein the one or more anchoring features include an aperture passing through a thickness of the at least one electrode.

Example 11 is the electrode array of examples 9 or 10, wherein the one or more anchoring features include a void having a depth that is less than a thickness of the at least one electrode.

Example 12 is the electrode array of examples 9-11, further comprising a substrate having at least one additional anchoring feature, wherein the at least one electrode is coupled to the substrate, and wherein the hydrogel layer is further mechanically coupled at the at least one additional anchoring feature.

Example 13 is the electrode array of examples 9-12, wherein the hydrogel layer comprises electrically conductive hydrogel material.

Example 14 is the electrode array of examples 9-13, wherein the hydrogel layer comprises a non-swelling hydrogel material or a low-swell hydrogel material.

Example 15 is the electrode array of examples 9-14, wherein the conductible metal layer is a noble metal.

Example 16 is the electrode array of example 15, wherein the conductible metal layer is selected from the group consisting of platinum and gold.

Example 17 is a method of preparing an electrode array, comprising: providing an electrode comprising a conductible metal layer; creating one or more anchoring features on the conductible metal layer; and introducing a hydrogel layer, wherein introducing the hydrogel layer includes mechanically securing the hydrogel layer against the conductible metal layer using the one or more anchoring features.

Example 18 is the method of example 17, wherein creating the one or more anchoring features includes creating at least one aperture through a thickness of the at least one electrode.

Example 19 is the method of examples 17 or 18, wherein creating the one or more anchoring features includes creating a void in the conductible metal layer extending from a surface of the conductible metal layer to a depth that is less than a thickness of the at least one electrode.

Example 20 is the method of examples 17-19, wherein providing the electrode includes applying the conductible metal layer to a substrate, the method further comprising creating at least one additional anchoring feature in the substrate, wherein introducing the hydrogel layer further includes mechanically securing the hydrogel layer using the at least one additional anchoring feature.

Example 21 is the method of examples 17-20, wherein the hydrogel layer comprises electrically conductive hydrogel material.

Example 22 is the method of examples 17-21, wherein the hydrogel layer comprises a non-swelling hydrogel material or a low-swell hydrogel material.

Example 23 is the method of examples 17-22, wherein the conductible metal layer is a noble metal.

Example 24 is the method of example 23, wherein the conductible metal layer is selected from the group consisting of platinum and gold.

Example 25 is an electrode array, comprising: at least one electrode comprising a conductible metal layer; a substrate supporting the at least one electrode; a non-swellable material defining an internal cavity surrounding the at least one electrode, the non-swellable material having one or more openings; and hydrogel material disposed within the internal cavity between the non-swellable material and the at least one electrode, wherein the non-swellable material mechanically secures the hydrogel material against the at least one electrode.

Example 26 is the electrode array of example 25, further comprising additional hydrogel material disposed opposite the non-swellable material from the internal cavity, wherein the additional hydrogel material contacts the hydrogel material.

Example 27 is the electrode array of examples 25 or 26, wherein the non-swellable material is coupled to the top surface of the substrate, and wherein the internal cavity is defined in part by at least a portion of the top surface of the substrate.

Example 28 is the electrode array of examples 25-27, wherein the internal cavity is sized to surround at least a portion of a bottom surface of the substrate, and wherein the hydrogel material is further disposed within the internal cavity between the non-swellable material and the bottom surface of the substrate.

Example 29 is the electrode array of examples 25-28, wherein the conductible metal layer of the at least one electrode includes one or more anchoring features, and wherein the hydrogel material is further mechanically coupled to the at least one electrode at the one or more anchoring features.

Example 30 is the electrode array of examples 25-29, wherein the substrate includes at least one additional anchoring feature, and wherein the hydrogel layer is further mechanically coupled at the at least one additional anchoring feature.

Example 31 is the electrode array of examples 25-30, wherein the hydrogel layer comprises electrically conductive hydrogel material.

Example 32 is the electrode array of examples 25-31, wherein the hydrogel layer comprises a non-swelling hydrogel material or a low-swell hydrogel material.

Example 33 is the electrode array of examples 25-32, wherein the conductible metal layer is a noble metal.

Example 34 is the electrode array of example 33, wherein the conductible metal layer is selected from the group consisting of platinum and gold.

Example 35 is an implantable device, comprising: an electrode array positionable adjacent biological tissue, the electrode array comprising: at least one electrode comprising a conductible metal layer; a substrate supporting the at least one electrode; a non-swellable material defining an internal cavity surrounding the at least one electrode, the non-swellable material having one or more openings; and hydrogel material disposed within the internal cavity between the non-swellable material and the at least one electrode, wherein the non-swellable material mechanically secures the hydrogel material against the at least one electrode, and wherein at least a portion of the hydrogel extends through the one or more openings for electrically coupling to the biological tissue and conducting a signal between the at least one electrode and the biological tissue when the electrode array is positioned adjacent the biological tissue; and a controller electrically coupled to the electrode array.

Example 36 is the implantable device of example 35, wherein the electrode array further comprises additional hydrogel material disposed opposite the non-swellable material from the internal cavity, wherein the additional hydrogel material contacts the hydrogel material for electrically coupling the hydrogel material to the biological tissue through the additional hydrogel material.

Example 37 is the implantable device of examples 35 or 36, wherein the non-swellable material is coupled to the top surface of the substrate, and wherein the internal cavity is defined in part by at least a portion of the top surface of the substrate.

Example 38 is the implantable device of examples 35-37, wherein the internal cavity is sized to surround at least a portion of a bottom surface of the substrate, and wherein the hydrogel material is further disposed within the internal cavity between the non-swellable material and the bottom surface of the substrate.

Example 39 is the implantable device of examples 35-38, wherein the conductible metal layer of the at least one electrode includes one or more anchoring features, and wherein the hydrogel material is further mechanically coupled to the at least one electrode at the one or more anchoring features.

Example 40 is the implantable device of examples 35-39, wherein the substrate includes at least one additional anchoring feature, and wherein the hydrogel layer is further mechanically coupled at the at least one additional anchoring feature.

Example 41 is the implantable device of examples 35-40, wherein the hydrogel layer comprises electrically conductive hydrogel material.

Example 42 is the implantable device of examples 35-41, wherein the hydrogel layer comprises a non-swelling hydrogel material or a low-swell hydrogel material.

Example 43 is the implantable device of examples 35-42, wherein the conductible metal layer is a noble metal.

Example 44 is the implantable device of example 43, wherein the conductible metal layer is selected from the group consisting of platinum and gold.

Example 45 is a method of preparing an electrode array, comprising: providing an electrode on a substrate, the electrode comprising a conductible metal layer; applying hydrogel material to the electrode; coating the hydrogel material with a non-swellable material, wherein the non-swellable material mechanically secures the hydrogel layer to the electrode; and creating one or more openings in the non-swellable material to expose the hydrogel material.

Example 46 is the method of example 45, wherein coating the hydrogel material with the non-swellable material includes coupling the non-swellable material to the substrate.

Example 47 is the method of examples 45 or 46, further comprising masking a first portion of the substrate prior to applying the hydrogel material to the electrode, wherein coating the hydrogel material with the non-swellable material includes coupling the non-swellable material to the first portion of the substrate.

Example 48 is the method of examples 45-47, further comprising overcoating the non-swellable material with additional hydrogel material, wherein the additional hydrogel contacts the hydrogel material through the openings in the non-swellable material.

Example 49 is the method of examples 45-48, further comprising creating one or more anchoring features on the conductible metal layer, wherein applying hydrogel material to the electrode includes mechanically securing the hydrogel layer against the conductible metal layer using the one or more anchoring features.

Example 50 is the method of examples 45-49, wherein the hydrogel layer comprises electrically conductive hydrogel material.

Example 51 is the method of examples 45-50, wherein the hydrogel layer comprises a non-swelling hydrogel material or a low-swell hydrogel material.

Example 52 is the method of examples 45-51, wherein the conductible metal layer is a noble metal.

Example 53 is the method of example 52, wherein the conductible metal layer is selected from the group consisting of platinum and gold.