Flexible implantable electrode assembly and manufacturing method

Description

[0001] The present invention relates to flexible implantable electrode arrangements, e.g., electrode arrays, and to a related manufacturing method.

[0002] Recent research and development in the field of neural engineering has led to a variety of active implantable medical devices (AIMDs) that can be used in a wide range of applications. These typically consist of a housing containing control electronics and a battery, implantable electrodes (or electrode arrays), and cables for electrically connecting the electrodes and the electronics. The electrodes are used for electrically stimulating cells or recording physiological signals.

[0003] Neural electrodes thus serve as an interface between the biological and technical systems, with their primary function being to record and / or stimulate neural signals. When neural electrodes are used in AIMD, they play a key role in restoring and maintaining bodily functions in patients with physical disabilities. Such electrodes feature an electrically conductive material for the contact areas and connection points, as well as a substrate material that insulates the electrically conductive materials. Key prerequisites for the success of implantable medical devices are, on the one hand, favorable tissue-electrode interaction and, on the other, sufficient biostability.For this reason, the mechanical flexibility of the electrode is an essential aspect in the design of neural probes to achieve structural biocompatibility and thereby reduce foreign body reaction and increase the lifetime of the implant.

[0004] Electrically conductive carbon materials meet the requirements regarding biostability as well as recording and stimulation capabilities, but they typically lack the ability to follow curved trajectories without breaking due to their hardness and brittleness. Therefore, carbon material is currently used only at the electrode contact points within a comparatively small area, while the conductive paths are made from thin metal films. Such electrodes are shown, for example, in the publication by S. Kassegne, "Electrical impedance, electrochemistry, mechanical stiffness, and hardness tunability in glassy carbon MEMS µECoG electrodes," Microelectronic Engineering, vol. 113, pp. 36-44, 2015. Coupling agents are sometimes also used between the carbon material and the metal (see M.Vomero, "Incorporation of Silicon Carbide and Diamond-Like Carbon as Adhesion Promoters Improves In Vitro and In Vivo Stability of Thin-Film Glassy Carbon Electrocorticography Arrays", Advanced Biosystems, vol. 2, p. 170081, 2018).

[0005] The article by Surabhi Nimbalkar et al., "Ultra-Capacitive Carbon Neural Probe Allows Simultaneous Long-Term Electrical Stimulations and High-Resolution Neurotransmitter Detection," SCIENTIFIC REPORTS, Vol. 8, No. 1, May 3, 2018, discloses carbon-based neural probes consisting of homogeneous glassy carbon (GC) microelectrodes, interconnecting elements, and bump pads. These electrodes exhibit purely capacitive behavior with an exceptionally high charge storage capacity (CSC) and are capable of withstanding more than 3.5 billion cycles of biphasic pulses at a charge density of <0.25 mC / cm². The probes enable both the recording of electrical signals with high SNR (>16) and remarkably high-resolution real-time detection of neurotransmitters on the same platform. The probes are fabricated using a two-sided, two-step structure transfer method for GC structures.These probes thus enable prolonged long-term electrical stimulation without corrosion of the electrode material. Cross-sectional characterization using FIB and SEM imaging reveals strong adhesion, mediated by covalent hydroxyl and carbonyl bonds between the GC microstructures and the upper insulating and lower substrate layers.

[0006] Publication US 2016 / 073920 A1 relates to hybrid metal and carbon or glassy carbon MEMS and ECoG electrode and microelectrode structures. Microelectromechanical systems are disclosed that comprise at least one electrode, microelectrode, or a combination thereof, wherein the at least one electrode comprises a carbon material, a glassy carbon material, or a combination thereof. The systems under consideration are suitable for µ-ECoG arrays.Additional microelectromechanical systems are disclosed that include at least one electrode, microelectrode, or combination thereof, wherein the at least one electrode comprises a carbon material, a glassy carbon material, or combination thereof; at least one substrate, surface, layer, or combination thereof, wherein the at least one electrode, microelectrode, or combination thereof is disposed on, coupled to, or otherwise layered upon the at least one substrate, surface, layer, or combination thereof; and at least one bump pad, wherein the at least one electrode, microelectrode, or combination thereof is coupled to the at least one bump pad via at least one conductive metal.A method of fabricating a microelectromechanical system comprises applying a polymer precursor, a carbonaceous material, or a combination thereof to a surface, a substrate, at least one layer, or a combination thereof; and heating or pyrolyzing the polymer precursor, a carbonaceous material, or a combination thereof to form a glassy carbon material.

[0007] Publication WO 2019 / 046631 A1 discloses a probe device comprising one or more insulating layers and a glassy carbon layer. The glassy carbon layer contains one or more channels. Each channel has a microstructure that may include an electrode region, a connection region, and a bump pad region. The electrode region can be brought into contact with a human or animal patient or subject and used to detect or deliver signals in applications such as electrocorticography (ECoG), electromyography (EMG), and nerve stimulation. A method for fabricating a probe comprises depositing a glassy carbon precursor on a substrate, patterning the precursor using photolithography, pyrolyzing the precursor to enable the formation of glassy carbon, and depositing one or more insulating layers.

[0008] However, known arrangements have at least one interface between the carbon electrodes and the metal, which easily leads to failures. With a larger number of interfaces, there is a risk of failures at each of these interfaces.

[0009] The fundamental problem with using carbon material is that it is inert and therefore difficult to bond with any type of surrounding material. This is particularly detrimental to adhesion to a substrate and the electrical connection to a metallic conductor or contact pad.

[0010] Furthermore, carbon material is hard and brittle. Therefore, deformation can lead to fracture of the structures, limiting both the flexibility of the electrode and the absolute size of the structures that can be realized.

[0011] If adhesion promoters are used between the carbon material and the metals connected to it, this further increases the number of interfaces and thus leads to an increased probability of failure.

[0012] There is therefore a need for a method for manufacturing flexible implantable electrode arrays that overcomes the disadvantages of known solutions, so that the manufactured electrode arrays are safe and reliable, yet can still be manufactured cost-effectively. Furthermore, there is a need for such a flexible implantable electrode array.

[0013] This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments of the present invention are the subject matter of the dependent patent claims.

[0014] The present invention, as defined in claims 1 and 5, is based on the idea of ​​producing a flexible, polymer-based electrode assembly with integrated contact points and electrical connection options in one piece from a carbon fiber material by embedding the carbon fiber material in an electrically insulating polymer material. Advantageously, the carbon fiber material is open-pored, allowing the first and / or second polymer material to at least partially penetrate the carbon fiber layer.

[0015] In particular, a flexible implantable electrode arrangement comprises an electrically insulating support structure comprising a first polymer material, an electrically conductive layer comprising an electrically conductive carbon fiber layer, wherein the electrically conductive layer is structured to integrally form at least one implantable electrode, at least one interconnect connected thereto, and at least one contact pad, and an electrically insulating cover layer, wherein the cover layer comprises a second polymer material and at least partially covers the electrically conductive layer. Advantageously, an entire array of electrodes, each integrally formed with the corresponding leads and contact pads, can be produced in this way.

[0016] The flexibility of the electrically conductive components can be ensured by using a highly flexible fiber material. Even if individual fibers break during bending, the electrical conductivity remains unchanged due to the mechanical embedding of the carbon fiber layer in the polymer material.

[0017] A wide variety of plastics can be used for the first and second polymer materials. For example, the first and / or second polymer materials include polyimide, PI, polyethylene terephthalate, PET, polyethylene, PE, polycarbonate, PC, polyvinyl chloride, PVC, polyamide, PA, polytetrafluoroethylene, PTFE, polymethyl methacrylate, PMMA, polyetheretherketone, PEEK, polysulfone, PSU, poly(p-xylylene), polydimethylsiloxane, PDMS, and / or polypropylene, PP. The support structure and the cover layer can be made of the same material or different materials. Polyimide has several advantages: Firstly, it is particularly inert and chemically stable in its fully crosslinked state. Secondly, it can be spin-coated in the form of a liquid precursor and also has a second, solid, but not yet fully cured preform, in which, for example, the adhesion of the carbon fiber layer and / or the next polymer layer is improved.Finally, there are photo-structurable polyimide resin systems that allow the contact pads to be opened easily, for example for the production of the cover layer.

[0018] Advantageously, the use of the carbon fiber material according to the invention makes it possible to provide a multimodal platform for simultaneous recording and stimulation of signals as well as for the detection of chemical substances.

[0019] According to an advantageous development of the present invention, the carbon fiber layer is made from a pyrolyzed polymer material. Therefore, the carbon fiber material can at least partially have a graphitic structure, i.e., have sp 2< -covalently hexagonally bonded carbon atoms arranged in mutually twisted and folded planes. The individual planes are bonded only via van der Waals forces. For example, the carbon fiber layer according to the invention can be produced from polyacrylonitrile (PAN) by stabilizing the PAN in air and then subjecting it to pyrolysis under a protective gas. However, it is clear to a person skilled in the art that all other common processes for producing a carbon fiber layer with sufficient electrical conductivity can also be used within the scope of the present invention. For example, cellulose or pitch can also serve as starting materials.

[0020] Particularly advantageously, the carbon fiber layer comprises a woven, knitted, or nonwoven fabric. For example, such a nonwoven fabric can be produced using an electrospinning process. Electrospinning can produce fibers with nanometer to micrometer diameters.

[0021] Nonwovens made of ultrathin fibers combine their relatively large specific surface area with macroporous properties, i.e., pore sizes of several micrometers. This makes them interesting for any application requiring excellent diffusion properties within a matrix with a large specific surface area. As a cohesive material, they are self-supporting and macroscopically easy to handle. The electrospinning process is based on the fact that the surface tension of a liquid droplet can be overcome by applying a high electrical voltage, causing a fine liquid jet to emerge from the droplet. For low-molecular-weight liquids, this jet breaks up into many very small, highly charged droplets. When polymeric substances are used, fibers are formed that are deposited on the counter electrode as a nonwoven.

[0022] Advantageously, the cover layer at least partially penetrates the carbon fiber layer. This allows for a strong bond to the carbon fiber layer on the one hand and to the underlying support structure on the other.

[0023] The present invention further relates to an associated method for producing an implantable electrode arrangement, the method comprising the following steps: Providing an electrically insulating support structure comprising a first polymer material, applying an electrically conductive layer comprising an electrically conductive carbon fiber layer, wherein the electrically conductive layer is structured to integrally form at least one implantable electrode, at least one conductor track connected thereto and at least one contact pad, applying an electrically insulating cover layer, wherein the cover layer comprises a second polymer material and at least partially covers the electrically conductive layer.

[0024] Such a one-piece arrangement, which includes at least one electrode structure, as well as the electrical leads and the contact pads required for contacting, has the advantage of being very efficient to manufacture. Furthermore, there are no transitions or interfaces between the electrode and the lead, or between the lead and the contacting surface, so that the electrical properties and long-term stability can be significantly improved compared to multi-part arrangements.

[0025] According to an advantageous development of the present invention, the electrically insulating support structure is provided in the form of an uncured or only partially cured precursor of the first polymer on a substrate. If, for example, polyimide is used, a polyimide precursor is used as the precursor, which is first imidized by a heat treatment step above 200°C and then cyclized by heat treatment at 400°C under nitrogen. The fully cyclized polyimide layer is temperature-stable up to nearly 500°C. The polyimide precursor can also be provided with photocrosslinkable additives so that the not yet cyclized polyimide layer can be photostructured.

[0026] According to an advantageous development of the method according to the invention, the step of applying the electrically conductive layer comprises the following steps: Providing a carbon fiber mat; attaching the carbon fiber mat to the electrically insulating support structure; structuring the carbon fiber mat.

[0027] The carbon fiber mat can be produced as a self-supporting component, for example, using an electrospinning process, making it available as a cost-effective semi-finished product. The fine electrode structures are then fabricated directly on the substrate, so that the structures are supported by the substrate and protected from damage. For example, the carbon fiber mat can be structured using an etching mask layer, either by wet etching or dry etching, or directly using laser ablation without a mask.

[0028] In particular, the carbon fiber mat can be produced by pyrolysis of a polymer, preferably by pyrolysis of polyacrylonitrile, PAN.

[0029] Just like the carrier structure, the cover layer can also be applied to the carbon fiber layer in the form of an uncured or only partially cured precursor of the second polymer. If polyimide is used, for example, a polyimide precursor is used as the precursor, which is first imidized by an annealing step above 200°C and then cyclized by annealing at 400°C under nitrogen. The fully cyclized polyimide layer is temperature-stable up to almost 500°C. The polyimide precursor can also be provided with photocrosslinkable additives, so that the not yet cyclized polyimide layer can be photostructured. This is particularly advantageous for the cover layer, because openings for the electrode tips and contact pads must be provided here.

[0030] In principle, the top layer can advantageously be deposited by means of a spin coating process, atomization or spray coating, vapor deposition or potting process, depending on the material used.

[0031] For example, the first and / or second polymer may comprise polyimide and / or polydimethylsiloxane.

[0032] As already mentioned, the carbon fiber mat is made of a woven, knitted, or nonwoven fabric, as this allows the advantageous porosity to be achieved while maintaining flexibility and stability. In particular, the production of the carbon fiber mat involves an electrospinning process.

[0033] In order to achieve good adhesion between the first polymer layer forming the support structure and the second polymer layer forming the cover layer, the method may further comprise the step of activating the first polymer material by means of oxygen plasma before depositing the second polymer.

[0034] The following terms and definitions are used below.

[0035] The term "flexible" in the context of the present invention means that a layer or substrate is flexible and, in particular, deformable within certain limits without breaking or at least without losing the desired electrical and mechanical properties.

[0036] The term "electrically conductive" is understood below to mean that a material is capable of conducting electrical current and is suitable for forming electrodes. In addition to the conductivity exhibited by metals, for example, this also encompasses the conductivity of a semiconducting material within the meaning of the present invention.

[0037] The term "graphitic" refers to a carbon material that sp2< -covalently hexagonally bonded carbon atoms which form solid planes, wherein the solid planes are arranged in any manner relative to one another to form the carbon fibers.

[0038] For a better understanding of the present invention, it will be explained in more detail with reference to the exemplary embodiments illustrated in the following figures. Identical parts are provided with the same reference numerals and component designations. Furthermore, some features or combinations of features from the various embodiments shown and described may represent independent, inventive, or inventive solutions. They show: Fig. 1 a schematic plan view of an electrode arrangement according to the present invention; Fig. 2A-I a schematic representation of a manufacturing process for an electrode arrangement according to a first embodiment of the present invention; Fig. 3A-G a schematic representation of a manufacturing process for an electrode arrangement according to a second embodiment of the present invention.

[0039] The present invention will be described below with reference to the figures, and in particular initially with reference to the schematic sectional views of the Figure 1 , explained in more detail. It should be noted that the proportions and, in particular, the layer thickness ratios in all figures are not necessarily shown to scale.

[0040] Figure 1 shows a top view of an exemplary embodiment of an electrode arrangement 100 comprising an array of 16 individual electrodes 116. Four (differently configured) individual electrodes 116 are combined to form a group of electrodes that form a sensor 118. Depending on the electrode shape, such a sensor 118 can be used to both feed stimulation signals into a nerve cell and to tap measurement signals from the nerve cell.

[0041] According to the invention, the individual electrodes 116 are each formed integrally with a conductor track 120. Furthermore, each conductor track 120 is in turn integrally connected to a contact surface 122 (hereinafter also referred to as contact pads). This eliminates the need for two interfaces that could otherwise cause failures.

[0042] According to the present invention, all electrically conductive structures are made of a carbon fiber material, as described with reference to the Figures 2 and 3 will be explained in more detail. For electrical insulation, the conductive structures 116, 118, 120, 122 are embedded in an electrically insulating polymer material 124. The polymer sheath is provided with corresponding openings at the locations where the electrically conductive material must be accessible, namely in the active areas 115 of the electrodes 116 and at the contact pads 122 (see Figures 2 and 3). The polymer material can be formed, for example, by polyimide.

[0043] Experiments have shown that the electrode assembly 100 according to the invention can be manufactured in a highly miniaturized form (e.g., with critical dimensions of approximately 12.5 µm). The conductive structures are highly flexible and mechanically stable, and excellent mechanical anchoring between the carbon fiber layer and the electrically insulating material was demonstrated. The carbon fiber structures showed no measurable decrease in electrical conductivity even after 100,000 cycles of bending stress. Thus, the present invention provides a completely metal-free and extraordinarily flexible electrode assembly 100 that is both mechanically and electrically extremely stable.

[0044] In summary, the electrode arrangement according to the present invention offers the following advantages: no additional interfaces between the active area of ​​the electrodes and the connection area to external components, strong mechanical integration of the conductive structures into the polymer, mechanical flexibility required for structural biocompatibility, high mechanical and electrical stability of the electrically conductive material, long lifetime of the electrode due to the increased stability.

[0045] The Figures 2A to 2I schematically show the manufacturing process of a flexible implantable electrode arrangement 100 according to the invention. Fig. 2A shows a substrate 102, for example a silicon or glass wafer, as the starting material, on which the future carrier structure 104, for example a polyimide layer, is applied. Of course, other polymers that form this first polymer layer 104 can also be used.

[0046] The polyimide layer can be deposited on the substrate 102, for example, using a spin-on process in the form of a liquid precursor. Advantageously, the decomposed polyimide layer 104 is first subjected to a drying step in which solvents are driven off, but without complete cyclization, before the carbon fiber layer is applied.

[0047] In the next step, which is Figure 2B As shown, a not yet structured carbon fiber layer 106 is deposited on the carrier structure 104.

[0048] The layer sequence is then subjected to a thermal treatment step in which the support structure 104 is converted into the fully cyclized polyimide form. This is indicated by the hatching. As is generally known, polyimide cures at approximately 400°C. Of course, temperature step profiles can also be used during this annealing process. Advantageously, this annealing step results in the carbon fibers 106 being partially embedded in the upper regions of the support structure 104.

[0049] In order to form an electrode arrangement, for example an array of electrodes, and electrical lines as well as contact pads, the carbon fiber layer 106 must be structured. Figure 2Dschematically illustrates that a mask 108 is applied for this purpose. The mask 108 leaves all the areas exposed in which the electrically conductive carbon fiber layer 106 is to be removed. For example, this mask 108 can be patterned using photolithography, as is common in semiconductor technology.

[0050] In the next step (see Figure 2E ), the material is removed from the areas not protected by the mask 108 using a wet or dry etching step. For example, reactive ion beam etching (RIE) can be advantageously used. In this case, not only the carbon fiber layer 106 but also at least a portion of the carrier structure 104 can be removed from the areas not covered by the mask 108. This is advantageous for the later bonding of a cover layer. The mask 108 is then removed again.

[0051] However, it is clear to a person skilled in the art that direct, i.e. maskless, structuring of the carbon fiber layer, e.g. by means of a laser structuring process, can also be used to produce the conductive structures.

[0052] The result of the structuring process is in any case the Figure 2F shown arrangement, in which the electrode arrangement, for example an array of electrodes, and electrical lines as well as contact pads are formed on the carrier structure 104.

[0053] In the next step, which is Figure 2GAs illustrated, a cover layer 110 comprising a second polymer material is applied over the entire surface. Advantageously, the cover layer 110 bonds to the support structure 104, so that the structured carbon fiber layer 106 is completely encased by the first and second polymer materials 104, 110. This ensures high mechanical stability and reliable electrical insulation of the carbon fiber layer 106.

[0054] For example, the second polymer forming the cover layer 110 may again be polyimide, which is spun on in the form of a precursor material and then cured in an annealing step.

[0055] The electrically conductive structures of the carbon fiber layer 106 must essentially be accessible at two interfaces and thus freed from the cover layer 110: Firstly, the active areas of the electrode must be able to come into contact with the biological environment, and secondly, the contact pads must be electrically contactable in order to connect the electrical conductor tracks to further electronic components for feeding and / or reading the electrodes.

[0056] Fig. 2H shows the arrangement after corresponding openings 112 have been introduced into the cover layer 110. For the introduction of the openings 112, for example, further photolithography can be performed (the mask is not shown in the figures), or direct structuring can be performed using a laser. Furthermore, a photo-structurable resin, e.g., a photo-structurable polyimide, can be used directly as the second polymer material.

[0057] In the final step, the electrode assembly is separated from the substrate 102 supporting it during the manufacturing process, as shown in Fig. 2I This can be done either by etching the substrate 102 or by lifting off the electrode arrangement 100.

[0058] With reference to Fig. 3A modified manufacturing process for the electrode arrangement according to the invention is explained below. It will be clear to a person skilled in the art that individual features of the two processes can be combined with one another as desired, and some of the individual process steps can also be carried out in different orders. In particular, it is also possible to reverse the layer sequence of cover layer and carrier layer such that first a layer with the contact openings is produced on the substrate, then the carbon fiber layer is applied and structured, and finally the carrier structure is deposited and, if necessary, also structured. This procedure has the advantage that openings for rear-side contacts are possible.

[0059] As in Fig. 3AAs shown, in a first step in the production of an electrode assembly, a polyacrylonitrile (PAN) fiber mat 114 can be produced, for example, by means of an electrospinning process. A 10% (weight / volume) solution of PAN in dimethylformamide (DMF) is spun onto a silicon substrate at 10 kV and a polymer flow rate of 0.6 ml / h. The PAN fiber mat can then be stabilized in an oxygen-containing atmosphere in a dry heating chamber for 120 minutes at 220 °C. This gives the PAN fiber mat 114, which in Fig. 3A is shown.

[0060] The stabilized PAN fiber mat is then pyrolyzed under a nitrogen atmosphere at 940 °C. A heating ramp of 5 °C / min and a holding time of 60 min can be used. Fig. 3B shows the resulting carbon fiber mat 106.

[0061] In the next step ( Fig. 3C) a 2 µm thick layer of a polyimide precursor is spun onto a silicon substrate 102 and dried at 90° for 3 minutes. A second polyimide layer is spun onto the first polyimide layer (not visible in the figure) to form the support structure 104. A carbon fiber mat 106 is placed onto the not yet cured surface of the polyimide layer and the Figure 3C The arrangement shown is then dried at 90°C for 3 minutes (soft-curing). The final cyclization then takes place at 450 °C.

[0062] In order to form the conductive structures in the carbon layer 106, the next step ( 3D figure) using a reactive ion etching (RIE) step using oxygen plasma. The areas not to be removed are covered with a photo-structured metallization (not shown in the figures), and the metal mask is then removed.

[0063] As in Figure 3E As shown, a polyimide layer, for example 4 µm thick, is spin-coated as the cover layer 110 and fully cycled. Optionally, before applying the cover layer 110, the surface to be coated can be 3D figure The arrangement shown can be activated using oxygen plasma (e.g., 80 W for 30 seconds). This improves the adhesion of the cover layer 110 to the substrate. To define the outer contours of the electrode arrangement, another RIE etching step can be performed using a photo-technically produced mask.

[0064] As in Figure 3FAs shown, the openings 112 for the active areas and the contact pads are also introduced using a further RIE etching step.

[0065] Finally, the individual electrode arrangements 100 are detached from the silicon substrate 102 (see Figure 3 G) .

[0066] In summary, the present invention provides a method for manufacturing electrode assemblies comprising pyrolyzed carbon fiber material for forming the conductive structures, embedded in a polyimide material. The carbon fiber structures proved to be highly flexible and electrically and mechanically stable. The adhesion of the individual layers to one another can be ensured by the special process, even over long periods of time and in aggressive environments. Since the carbon fiber material is applied as a fiber mat, it can also be used to form larger structures, such as contact pads, without breaking under deformation and without requiring an additional interface between the active electrode region and the connection to external devices. This integration results in high mechanical stability and high stability during electrical stimulation.Furthermore, the use of carbon fibers results in the electrically conductive structures being embedded in and permeated by the insulating polymer material. Furthermore, because graphitic carbon material is highly resistant to corrosion, electrode arrays with excellent stability and durability can be manufactured. Therefore, implanted electrodes need to be replaced less frequently, which is beneficial for the user. Furthermore, the carbon fiber material can be used to enable a multimodal platform for simultaneous recording, stimulation, and detection of chemical substances. List of reference symbols:

[0067] Reference number Description 100 Electrode arrangement 102 Substrat 104 Support structure; first polymer layer 106 Carbon fiber layer 108 mask 110 Top layer 112 Openings in the top layer 114 PAN fiber mat 115 Active area 116 electrode 118 sensor 120 conductor track 122 Contact pad 124 Polymer material

Claims

1. Flexible implantable electrode arrangement (100) comprising: an electrically insulating carrier structure (104) comprising a first polymer material, an electrically conductive layer, wherein said electrically conductive layer is structured in order to integrally form at least one implantable electrode (116), at least one conductor track (120) connected thereto, and at least one contact pad (122), and an electrically insulating cover layer (110), wherein said cover layer (110) comprises a second polymer material and covers said electrically conductive layer (106) at least in part, characterized in that the electrically conductive layer comprises an electrically conductive carbon fiber layer (106), which comprises a woven fabric, knitted fabric, or non-woven fabric.

2. Electrode arrangement according to claim 1, wherein said first and / or said second polymer material comprise polyimide, PI, polyethylene terephthalate, PET, polyethylene, PE, polycarbonate, PC, polyvinyl chloride, PVC, polyamide, PA, polytetrafluoroethylene, PTFE, polymethyl methacrylate, PMMA, polyether ether ketone, PEEK, polysulfone, PSU, Poly(p-xylylene), polydimethylsiloxane, PDMS, and / or polypropylene, PP.

3. Electrode arrangement according to claim 1 or 2, wherein said carbon fiber layer (106) is produced from pyrolyzed polymer material.

4. Electrode arrangement according to one of the preceding claims, wherein said cover layer (110) and / or said carrier structure (104) penetrates into said carbon fiber layer at least in part.

5. Method for the production of an implantable electrode arrangement (100), said method comprising the steps of: providing an electrically insulating carrier structure (104) comprising a first polymer material, applying an electrically conductive layer (106) comprising an electrically conductive carbon fiber layer, which comprises a woven fabric, knitted fabric, or non-woven fabric, wherein said electrically conductive layer is structured in order to integrally form at least one implantable electrode (116), at least one conductor track (120) connected thereto, and at least one contact pad (122), applying an electrically insulating cover layer (110), wherein said cover layer comprises a second polymer material and covers said electrically conductive layer at least in part.

6. Method according to claim 5, wherein said electrically insulating carrier structure (104) is provided on a substrate in the form of a precursor of said first polymer that has not cured or only in part.

7. Method according to claim 5 or 6, wherein the step of applying said electrically conductive layer (106) comprises the following steps: providing a carbon fiber mat; attaching said carbon fiber mat to said electrically insulating carrier structure; structuring said carbon fiber mat.

8. Method according to claim 7, wherein said carbon fiber mat is structured using an etching mask layer by way of wet etching or dry etching or without a mask directly by way of laser ablation.

9. Method according to one of the claims 7 or 8, wherein said carbon fiber mat is produced by pyrolysis of a polymer, preferably by pyrolysis of polyacrylonitrile, PAN.

10. Method according to one of the claims 5 to 9, wherein said cover layer (110) is applied onto said carbon fiber layer (106) in the form of a precursor of the first polymer that has not cured or only in part.

11. Method according to one of the claims 5 to 10, wherein said cover layer (110) is deposited in a spin-on process, by atomization, or spray coating, by vapor deposition, or in a potting process.

12. Method according to one of the claims 5 to 11, wherein said first and / or said second polymer comprise polyimide and / or polydimethylsiloxane.

13. Method according to one of the claims 5 to 12, wherein the production of said carbon fiber mat comprises an electrospinning process.

14. Method according to one of the claims 5 to 13, further comprising the step of activating said first polymer material by way of oxygen plasma prior to the deposition of said second polymer.