An ECoG electrode and its preparation method

Abstract

The present invention belongs to the field of brain-computer interface, and specifically relates to an ECoG electrode and a preparation method thereof. The implantable electrode of the present invention includes a flexible support layer, an electrode metal layer and a packaging layer, wherein the electrode metal layer includes an electrode contact array area, a pad area and a conductive wire; the electrode contact array area contains one or more electrode contacts, and the pad area contains one or more solder joints; each of the electrode contacts and a corresponding solder joint is connected by a conductive wire to form a connection path, and different connection paths are electrically isolated from each other. The present invention sets different materials on the exposed surfaces of the electrode contacts and solder joints, so that different materials can give full play to their respective advantages, which not only optimizes the electrode performance, but also helps to maintain the consistency of signal transmission. At the same time, the manufacturing process required for the electrode is also relatively simple, the cost is lower, and it is also more environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of brain-computer interfaces, and particularly relates to an ECoG electrode and a preparation method thereof. Background Art

[0002] ECoG electrodes (electrocorticography electrodes) are electrodes used to record the electrical activities on the surface of the brain. This technology records brain electrical activities by implanting an electrode array on the surface of the brain. Compared with traditional EEG, ECoG can provide higher spatial resolution and can more accurately locate and identify the sources of brain activities.

[0003] ECoG electrodes are usually implanted subdurally in the cortex, and their performance design still faces the following requirements: (1) Good electrical performance: When designing the electrodes, it is necessary to optimize the electrical performance to achieve low impedance, high addressing rate, and stable electrical performance, so as to obtain a high signal-to-noise ratio and at the same time reduce the risk of tissue damage during the stimulation process. (2) High mechanical adaptability: The electrodes have high mechanical softness and flexibility to reduce the mechanical mismatch with biological tissues, so as to reduce the interference of brain micromovement on the signal quality and enable the electrodes to adapt to the morphological changes of brain tissues. (3) Good biocompatibility: Select electrode materials that meet the approval standards of relevant regulatory agencies to ensure good compatibility between the electrodes and biological tissues, without causing rejection reactions and reducing biological risks. However, the existing clinically used ECoG electrodes often have low leads, and the collected signals are not fine enough, and the signal-to-noise ratio is not high enough, which may lead to signal distortion and make it difficult to accurately locate abnormal activity areas, thus affecting diagnosis and treatment.

[0004] At present, most ECoG electrodes use flexible and bendable materials to make the substrate and encapsulation layer, and this flexible material is usually a polymer. As for the materials of the electrode tips, those commonly used now include polymer films, silicon films, metals, or carbon nanomaterials, etc. Flexible ECoG electrodes are usually designed in the form of arrays, which contain multiple electrode contacts. These arrays can contain dozens to hundreds of electrodes, allowing the simultaneous recording of the electrical activities of different regions of the brain, thus providing more detailed information. Generally speaking, the materials and structures of the electrodes are crucial for the performance, biocompatibility, and stability of the brain-computer interface. For example, carbon nanomaterials such as graphene and carbon nanotubes have excellent flexibility and strength, as well as high carrier mobility, etc., and they perform outstandingly in making microelectrode arrays. On the other hand, flexible materials such as polyimide perform excellently in providing high mechanical strength, biocompatibility, and flexibility. The flexible materials can better adhere to the surface of the cerebral cortex, reduce damage to brain tissue, and also help improve the biocompatibility of the electrodes. There are also some materials such as titanium dioxide nanowires, which can be made into a stretchable electrode network suitable for chronic recording. By depositing nanoparticles on the electrode surface, the specific surface area can be increased, the interface impedance can be reduced, the signal noise can be lowered, and the electrochemical activity and biocompatibility of the electrodes can be improved. With the progress of materials science and various technologies, the current bio-brain electrode arrays are developing towards the directions of ultra-high-density recording, large-range recording, minimal trauma, and high-performance technologies.

[0005] In the patent US20210371987A1 of the Board of Trustees of the University of California, Dayeh Shadi A et al., the chemical properties of the electrode surface are improved by adding nanostructures. During the fabrication of this electrode, a planar metal electrode needs to be first formed on a flexible substrate, and then a platinum alloy layer is deposited on the planar electrode by physical vapor deposition. Subsequently, dealloying is used to etch the platinum alloy to form porous platinum nanorods. Dealloying is achieved by selectively etching the non-platinum part in the platinum alloy with acid. The platinum nanorod electrode prepared by the above method has a porous structure, a relatively large surface area, and is more sensitive to the signals of target neurons. In addition, this fabrication process can precisely control the shape, size, etc. of the platinum nanorods. Moreover, wrapping an insulating layer around the platinum nanorods and electrode leads can also improve the electrode stability and long-term performance, and reduce the oxidation and corrosion of the electrode. However, the structure of this electrode is relatively complex, and the required fabrication process is also rather numerous, including various processes, involving chemical deposition, physical deposition, dealloying treatment, etc. In physical deposition, co-sputtering technology is used, which involves sputtering of multiple different metal materials simultaneously, and requires more complex process control and parameter adjustment to ensure the required alloy ratio and performance. In chemical vapor deposition, relatively high temperatures are often required, usually between several hundred and several thousand degrees Celsius, which may limit the application of the substrate material and cause problems such as thermal expansion and mechanical stress of the material. And dealloying treatment requires a dedicated furnace or reactor, and precise temperature control of the reaction process. At the same time, strong corrosive acids, such as nitric acid, are needed to etch the platinum alloy part in this electrode during dealloying, which may generate toxic gases and liquid waste during the treatment process, and is also relatively troublesome during the treatment process. Summary of the Invention

[0006] The present invention provides a flexible electrode with high density for intracranial recording and stimulation. The structure of this electrode is simple, the required fabrication process is simpler, the cost is lower, and it is more environmentally friendly.

[0007] Specifically, the present invention first provides an implantable electrode, which includes: a flexible support layer; an electrode metal layer disposed on the flexible support layer, the electrode metal layer including an electrode contact array region, a pad region, and conductive wires; the electrode contact array region contains one or more electrode contacts, and the pad region contains one or more solder joints; each electrode contact is connected to a corresponding solder joint by a conductive wire to form a connection path, and different connection paths are electrically isolated from each other; and a packaging layer that covers the electrode metal layer and forms exposed surfaces only at the electrode contacts and the solder joints; wherein the materials of the exposed surfaces of the electrode contacts and the solder joints are different and are respectively selected from one of tungsten, titanium, platinum, gold, platinum-iridium alloy, iridium oxide, titanium nitride, poly(3,4-ethylenedioxythiophene) (PEDOT), and carbon nanotubes (CNT).

[0008] The present invention also provides a method for preparing the implantable electrode, which includes: providing a substrate; forming a sacrificial layer on the surface of the substrate; forming the flexible support layer on the sacrificial layer; processing and forming the electrode metal layer on the flexible support layer; forming a packaging layer on the electrode metal layer and exposing the electrode contacts and the solder joints; and releasing the implantable electrode from the sacrificial layer.

[0009] By providing different materials on the exposed surfaces of the electrode contacts and the solder joints, the present invention enables different materials to give full play to their respective advantages, not only optimizing the electrode performance, but also helping to maintain the consistency of signal transmission. At the same time, the manufacturing process required for this electrode is relatively simple, with lower costs and greater environmental friendliness. Description of the Drawings

[0010] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 It is a schematic cross-sectional view of the product in Step 1 during the preparation of the implantable electrode according to an embodiment of the present invention.

[0012] Figure 2 It is a schematic cross-sectional view of the product in Step 2 during the preparation of the implantable electrode according to an embodiment of the present invention.

[0013] Figure 3 It is a schematic cross-sectional view of the product in Step 3 during the preparation of the implantable electrode according to an embodiment of the present invention.

[0014] Figure 4 This is a schematic cross-sectional view of the product in Step 4 during the preparation of the implantable electrode in the embodiments of the present invention.

[0015] Figure 5 This is another schematic cross-sectional view of the product in Step 4 during the preparation of the implantable electrode in the embodiments of the present invention.

[0016] Figure 6 This is yet another schematic cross-sectional view of the product in Step 4 during the preparation of the implantable electrode in the embodiments of the present invention.

[0017] Figure 7 This is yet another schematic cross-sectional view of the product in Step 4 during the preparation of the implantable electrode in the embodiments of the present invention.

[0018] Figure 8 This is yet another schematic cross-sectional view of the product in Step 4 during the preparation of the implantable electrode in the embodiments of the present invention.

[0019] Figure 9 This is a schematic cross-sectional view of the product in Step 5 during the preparation of the implantable electrode in the embodiments of the present invention.

[0020] Figure 10 This is another schematic cross-sectional view of the product in Step 5 during the preparation of the implantable electrode in the embodiments of the present invention.

[0021] Figure 11 This is a schematic cross-sectional view of the product in Step 6 during the preparation of the implantable electrode in the embodiments of the present invention.

[0022] Figure 12 This is the etching layout of the electrode solder joint used in Step 4 when preparing the implantable electrode in the embodiments of the present invention.

[0023] Figure 13 This is the etching layout of the electrode structure used in Step 4 when preparing the implantable electrode in the embodiments of the present invention.

[0024] Figure 14 This is the development synchronous etching layout used in Step 5 when preparing the implantable electrode in the embodiments of the present invention.

[0025] In the drawings, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Embodiments

[0026] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention. Those skilled in the art can make various modifications and changes to the present invention without departing from the scope or spirit of the present invention. For example, the features described or illustrated as part of one embodiment can be used in another embodiment to produce a further embodiment.

[0027] Unless otherwise specified, the meanings of all terms (including technical and scientific terms) used to disclose the present invention are the same as those commonly understood by those of ordinary skill in the art to which the present invention pertains. Through further guidance, the following definitions are used to better understand the teachings of the present invention. The terms used in the specification of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0028] As used herein, the alternative ranges of the terms "and / or", "or / and", and "and / or" include any one of two or more related listed items, as well as any and all combinations of the related listed items. The said any and all combinations include combinations of any two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, this technical solution undoubtedly includes the technical solution connected by "logical AND", and undoubtedly also includes the technical solution connected by "logical OR". For example, "A and / or B" includes three parallel solutions: A, B, and A + B. Another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, it includes combinations of any two or any three of A, B, C, and D, and also includes the four-item combination of A, B, C, and D (that is, the technical solution connected by "logical AND").

[0029] The terms "comprising", "containing", and "including" used in the present invention are synonyms, which are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps.

[0030] In the present invention, the numerical ranges represented by endpoints include all the numerical values and fractions included within the range, as well as the recited endpoints.

[0031] Regarding the concentration values involved in the present invention, their meanings include fluctuations within a certain range. For example, it can fluctuate within the corresponding accuracy range. For example, for 2%, a fluctuation within the range of ±0.1% is allowed. For larger numerical values or those that do not require overly precise control, a greater fluctuation in their meanings is also allowed. For example, for 100 mM, fluctuations within the ranges of ±1%, ±2%, ±5%, etc. are allowed. Regarding the molecular weight, a fluctuation of ±10% in its meaning is allowed.

[0032] In the present invention, regarding descriptions such as "a plurality of" and "a variety of", unless otherwise specified, it means greater than or equal to 2 in quantity.

[0033] In the present invention, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0034] In the present invention, "preferably", "better", "more preferably", and "should be" are only used to describe the embodiments or examples with better effects, and it should be understood that they do not constitute a limitation to the protection scope of the present invention.

[0035] In the present invention, "optionally", "optional", "option", "optionally", "optional", "option", mean that it can be either present or absent, that is, it refers to any one of the two parallel options of "present" or "absent". If there are multiple "optionally" or "optional" in a technical solution, without special instructions, and without contradictions or mutual restrictions, each "optionally" or "optional" is independent of each other.

[0036] In the present invention, terms such as "upper" and "lower" describing the orientation are all relative orientations. When the placement direction of the implantable electrode changes, those skilled in the art can also confirm the actual orientation corresponding to the above-described descriptive terms.

[0037] Implantable electrode

[0038] The present invention first provides an implantable electrode, which includes: a flexible support layer; an electrode metal layer, the electrode metal layer is disposed on the flexible support layer, and the electrode metal layer includes an electrode contact array region, a pad region, and a conductive wire; the electrode contact array region contains one or more electrode contacts, and the pad region contains one or more solder joints; each electrode contact is connected to a corresponding solder joint through a conductive wire to form a connection path, and different connection paths are electrically isolated from each other; and a packaging layer, the packaging layer covers the electrode metal layer, and only forms an exposed surface at the electrode contact and the solder joint; wherein, the materials of the exposed surfaces of the electrode contact and the solder joint are different, and are respectively selected from one of tungsten, titanium, platinum, gold, platinum-iridium alloy, iridium oxide, titanium nitride, poly(3,4-ethylenedioxythiophene) (PEDOT), and carbon nanotubes (CNT).

[0039] The present invention surprisingly discovers that by setting different materials on the exposed surfaces of the electrode contacts and the solder joints, the respective advantages of different materials can be fully utilized, which can not only significantly optimize the electrode performance, but also be beneficial to maintaining the consistency of signal transmission.

[0040] In some embodiments, the material of the exposed surface of the electrode contact is a metal with excellent conductivity and stability.

[0041] In some embodiments, the material of the exposed surface of the solder joint is a metal with excellent welding firmness and stability.

[0042] In some embodiments, the material of the exposed surface of the electrode contact is selected from one of platinum, gold, tungsten, iridium oxide, titanium nitride, poly(3,4-ethylenedioxythiophene), and carbon nanotubes, and the material of the exposed surface of the solder joint is selected from one of titanium, platinum, gold, and platinum-iridium alloy.

[0043] In some embodiments, the material of the exposed surface of the electrode contact is platinum, and the material of the exposed surface of the solder joint is gold.

[0044] In some embodiments, the electrode metal layer includes at least two different materials, and the exposed surfaces are formed by different layers of materials at the electrode contact and the solder joint.

[0045] In some embodiments, the electrode metal layer sequentially includes a titanium or chromium layer, a first platinum layer, a gold layer, and a second platinum layer from bottom to top. The exposed surface at the electrode contact is formed by the material of the second platinum layer, and the exposed surface at the solder joint is formed by the material of the gold layer.

[0046] In some embodiments, the diameter of the electrode contact is 5 μm to 1000 μm. This can be closer to neuron tissue, and the size is closer to that of cortical functional columns, which are between 100 and 500 microns and are considered the basic units of information processing. Therefore, such a size can obtain higher spatial resolution and finer information, has better biocompatibility, and is more suitable for long-term in-vivo recording.

[0047] In some specific embodiments, the diameter of the electrode contact can be 5 μm, 50 μm, 100 μm, 250 μm, 500 μm, 750 μm, 1000 μm, etc., or any diameter within the above range.

[0048] In some specific embodiments, the horizontal cross-section of the electrode contact is one of a square, rectangle, triangle, rhombus, ellipse, or polygon.

[0049] In some embodiments, the thickness of the implantable electrode is 5 μm to 1000 μm, and the thickness of the electrode metal layer is 0.01 μm to 10 μm.

[0050] In some specific embodiments, the thickness of the implantable electrode can be 5 μm, 10 μm, 50 μm, 100 μm, 250 μm, 500 μm, 750 μm, 1000 μm, etc., or any thickness within the above range.

[0051] In some specific embodiments, the thickness of the electrode metal layer is 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 2.5μm, 5μm, 7.5μm, 10μm, etc., or any thickness within the above range.

[0052] In some embodiments, in the electrode contact array region, there are also a plurality of holes penetrating the implantable electrode, and the holes are physically separated from the electrode contacts. Introducing holes in the contact area can improve the flexibility of the electrode and promote the natural flow of cerebrospinal fluid, so as to better adapt to biological tissues. At the same time, this also helps to better maintain a good environment in the brain, can promote the circulation of cerebrospinal fluid, contribute to maintaining brain health, as well as the cleanliness and normal function of the brain, and further reduce the abnormal deposition and aggregation of harmful proteins, reducing the risk of other brain diseases, and is more suitable for long-term in-vivo recording.

[0053] In some specific embodiments, the horizontal cross-section of the hole is circular or other geometric shapes.

[0054] In some specific embodiments, the holes are distributed around the electrode contacts and are physically separated from the electrode contacts.

[0055] In some embodiments, the corners of the conductive wires are all curved. This can make the signal transition more smoothly, reduce the sudden change of impedance, contribute to maintaining a more consistent signal transmission performance, and has certain electromagnetic compatibility (EMC) advantages. At the same time, it can also make the etching process smoother and more stable, effectively reduce the non-uniformity during the etching process, and minimize the operation error. In the existing technology, the commonly used straight-line wiring has sharp corners and connection points, which may cause signal reflection, resulting in signal attenuation and distortion; straight-line wiring also has the problem of impedance mismatch, damaging signal integrity, and is prone to electromagnetic coupling, leading to signal crosstalk.

[0056] In some embodiments, the materials of the flexible support layer and the encapsulation layer are both non-degradable low-temperature-curing flexible materials, and the curing temperature of the flexible material is lower than the melting point of PMMA. This can better be compatible with the PMMA sacrificial layer, thus facilitating the simplification of the preparation process and reducing costs.

[0057] In some embodiments, the flexible material is at least one of polyimide, SU-8, liquid crystal polymer, and Parylene-C, and more preferably a low-temperature-curing polyimide.

[0058] In some embodiments, at least one of the electrode contacts is used for signal acquisition.

[0059] In some embodiments, at least one of the electrode contacts is used for electrical stimulation.

[0060] In some embodiments, the electrode contact for electrical stimulation has a charge injection capacity (CIC) of 10 mC / cm2 to 100 mC / cm2.

[0061] In some embodiments, the electrode contact for electrical stimulation has a charge storage capacity of 10 mC / cm2 to 100 mC / cm2.

[0062] In some embodiments, the impedance of the electrode contact for electrical stimulation is 100 ohms to 10 megohms.

[0063] The present invention does not particularly limit the number of connection paths. In some specific embodiments, the number of the connection paths is an integer greater than or equal to 1, for example, 1, 2, 3,... 63, 65, 120, etc.

[0064] In some specific embodiments, the number of the connection paths may be an integer power of 2 such as 16, 32, 64, 128, 256, 512, 1024, etc.

[0065] Preparation method

[0066] The present invention also provides a method for preparing the implantable electrode, which includes: providing a substrate; forming a sacrificial layer on the surface of the substrate; forming the flexible support layer on the sacrificial layer; processing and forming the electrode metal layer on the flexible support layer; forming a packaging layer on the electrode metal layer and exposing the electrode contact and the solder joint; releasing the implantable electrode from the sacrificial layer.

[0067] In some embodiments, the material of the sacrificial layer is PMMA; when forming the flexible support layer and the packaging layer, the material is cured at a temperature lower than the melting point of PMMA; preferably, the curing temperature is 220 - 240 °C. Selecting polymethyl methacrylate (PMMA) as the sacrificial layer material will be more convenient for peeling, so as to simplify the preparation process, reduce costs, and make its production more environmentally friendly.

[0068] In some embodiments, the preparation method further includes: after releasing the implantable electrode from the sacrificial layer, further curing the materials of the flexible support layer and the packaging layer by thermal stepwise temperature rise curing.

[0069] In some embodiments, when releasing the implantable electrode from the sacrificial layer, acetone solution is used to dissolve the sacrificial layer.

[0070] Example

[0071] The embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions noted in the following examples, the guidance given in the present invention shall be preferentially referred to, and it can also be carried out according to the experimental manuals or conventional conditions in the art, or other experimental methods known in the art, or according to the conditions recommended by the manufacturer.

[0072] In the following specific examples, regarding the measurement parameters of raw material components, if there is no special instruction, there may be slight deviations within the weighing accuracy range. Regarding temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0073] As Figures 1 to 14 shown (where Figures 1 to 11 is a schematic cross-sectional view of the product during the preparation of the implantable electrode, which has no practical limiting significance for the actual positions of each region such as solder joints, electrode contacts, holes, etc., and the actual size of the implantable electrode), the preparation method of the implantable electrode provided in this embodiment includes the following steps:

[0074] Step 1: Provide a substrate 1;

[0075] As Figure 1 shown, in some examples, Step 1 includes providing a substrate 1, cleaning the substrate 1 with a solvent, and then drying the surface. In a specific example, the material of the substrate 1 includes any one of silicon nitride, silicon, quartz glass, etc. The size of the substrate 1 can also be four inches, six inches, eight inches, etc. The solvents for cleaning the substrate include acetone, isopropyl alcohol, deionized water, etc.

[0076] Step 2: Form a sacrificial layer 2 on the surface of the substrate 1;

[0077] As Figure 2 shown, in some examples, Step 2 includes coating the material PMMA of the sacrificial layer 2 on the substrate 1 and heating and curing it. In a specific example, the coating method includes spin coating, spraying, etc. The material of the sacrificial layer 2 can also be a photocurable material, including photosensitive polymers, photocurable resins, photosensitive adhesives, photosensitive polymer films, optical adhesives, etc., and its thickness is 0.1 - 100 μm. As an example, the thickness of the sacrificial layer 2 can be 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, etc. or any thickness within its range.

[0078] Step 3: Form the flexible support layer 3 on the sacrificial layer 2;

[0079] As Figure 3As shown, in some examples, Step 3 includes coating the surface of the sacrificial layer 2 with a flexible support layer 3 and curing it by low-temperature heating at 135°C. In a specific example, the coating method includes spin coating, spraying, etc. The material of the flexible support layer 3 is a low-temperature curing polyimide, and the thickness of the flexible support layer 3 is 0.2 - 100 μm. As an example, the thickness of the flexible support layer 3 can be 0.2 μm, 0.8 μm, 2 μm, 4 μm, 6 μm, 9 μm, etc. or any thickness within this range.

[0080] Step 4, fabricating the electrode metal layer 4 on the flexible support layer 3;

[0081] As Figure 4 shown, in some examples, Step 4 includes depositing multiple times on the surface of the flexible support layer 3 to form an electrode metal layer 4 including a titanium layer, a first platinum layer, a gold layer, and a second platinum layer in sequence from bottom to top. In some specific examples, the titanium layer in the above electrode metal layer 4 can also be replaced with a chromium layer. In some specific examples, the materials of the electrode metal layer 4 include tungsten, titanium, platinum, gold, platinum-iridium alloy, iridium oxide, titanium nitride, poly(3,4-ethylenedioxythiophene), carbon nanotubes, or any combination of any number of the above types. In some specific examples, the thickness of each layer of material in the electrode metal layer 4 is 5 - 1000 nm, or any thickness within this range. In some specific examples, the deposition methods include chemical vapor deposition, magnetron sputtering, electron beam evaporation, and ion beam deposition (IBD), etc.

[0082] As Figure 5 、 Figure 6 、 Figure 12 shown, in some examples, Step 4 further includes forming a predefined pattern area 5 on the formed electrode metal layer 4. This area is an area formed by lithographic development patterning, and the area without photoresist protection after development is the FPC solder joint area 6 of the electrode. In some examples, Step 4 further includes etching the area 6 at the electrode solder joint. In some specific examples, the method of forming the etching area includes electron beam etching, laser etching, ion beam etching, chemical etching, etc. The etching depth is 5 - 300 nm, or any thickness within this range. The final etching depth is equivalent to or slightly exceeds the thickness of the first layer of metal to ensure that the outermost exposed surface at the solder joint is the second layer of metal.

[0083] As Figure 7 shown, in some examples, Step 4 further includes, after removing the photoresist, using photoresist again for lithographic development patterning to form area 7, and etching to form a graphic area 8 outside the electrode pattern (including the holes in the electrode contact array area and the electrode peripheral contour area). In some specific examples, the etching method includes electron beam etching, laser etching, ion beam etching, chemical etching, etc. The etching depth is the thickness value of all metal layers.

[0084] As Figure 8 , Figure 13 shown, in some examples, step four further includes removing the photoresist to obtain an electrode structure with a preset shape.

[0085] Step five: Form a packaging layer 9 on the electrode metal layer 4, and expose the electrode contacts and the solder joints;

[0086] As Figure 9 shown, in some examples, step five includes coating a packaging layer 9 on the previously formed electrode metal layer 4. In some specific examples, the material of the packaging layer 9 is low-temperature curable polyimide. The coating methods include roll coating, spin coating, etc., which are the same as the material of the flexible support layer 3. The thickness range of the packaging layer 9 is 1 - 10 μm. Specifically, it can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, etc. or any thickness within this range. The total thickness range of the two layers of polyimide after coating is 6 - 110 μm.

[0087] As Figure 10 , Figure 14 shown, in some examples, step five further includes lithography and development patterning again. During development, the surface polyimide is etched synchronously. Solder joints 10, electrode contacts 11, and holes 12 in the electrode contact array area where the polyimide is completely etched and the electrode peripheral contour area are formed at the etched areas.

[0088] Step six: Release the implantable electrode from the sacrificial layer 2;

[0089] As Figure 11 shown, in some examples, step six includes using a solution to dissolve the sacrificial layer 2. In a specific example, acetone solution can be used to dissolve the sacrificial layer 2.

[0090] In some examples, step six further includes the materials of the flexible support layer 3 and the packaging layer 9. In a specific example, the way to cure the material is thermal stepwise temperature curing.

[0091] As Figures 11 to 14 shown, the implantable electrode provided in this embodiment includes a flexible support layer 3, an electrode metal layer 4, and a packaging layer 9.

[0092] Among them, the material of the flexible support layer 3 is a low-temperature type curable polyimide with a curing temperature lower than the melting point of PMMA.

[0093] The electrode metal layer 4 is disposed on the flexible support layer 3. The electrode metal layer 4 includes an electrode contact array region, a pad region, and conductive wires 13. The electrode contact array region contains a plurality of electrode contacts 11, and the pad region contains a plurality of solder joints 10. Each electrode contact 11 is connected to a corresponding solder joint 10 by a conductive wire 13 to form a connection path, and different connection paths are electrically isolated from each other. The electrode metal layer 4 sequentially includes a titanium layer, a first platinum layer, a gold layer, and a second platinum layer from bottom to top. An exposed surface is formed at the electrode contact 11 with the material of the second platinum layer, and an exposed surface is formed at the solder joint 10 with the material of the gold layer. The diameter of the electrode contact is 5 μm to 1000 μm. As an example, the diameter of the electrode contact can be 5 μm, 50 μm, 100 μm, 250 μm, 500 μm, 750 μm, 1000 μm, etc., or any diameter within the above range. The corners of the conductive wire 13 are all curved.

[0094] In the electrode contact array region, there are also a plurality of holes 12 penetrating the implantable electrode, and the holes 12 are physically separated from the electrode contacts 11.

[0095] The encapsulation layer 9 covers the electrode metal layer 4, and exposed surfaces are formed only at the electrode contacts 11 and the solder joints 10. The material of the encapsulation layer 9 is the same as that of the flexible support layer 3, and both are low-temperature cured polyimide with a curing temperature lower than the melting point of PMMA.

[0096] In some examples, the implantable electrode can be obtained by the above preparation method.

[0097] In the description of this specification, the description made with reference to terms such as "some possible embodiments", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application, and the above terms do not necessarily represent the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples to obtain other embodiments of the implantable electrode or its preparation method in the present invention.

[0098] Compared with the prior art, the implantable electrode provided by the embodiment of the present invention has the following significant technical effect improvements:

[0099] First, the implantable electrode uses different metal materials at the solder joints and the uppermost exposed surface of the electrode contacts to give full play to their respective advantages. The contact surface uses a metal with excellent conductivity and stability, while the solder joints use a metal with excellent welding firmness and stability. This design not only optimizes the electrode performance but also helps to maintain the consistency of signal transmission.

[0100] Second, the implantable electrode introduces tiny holes in the electrode contact array area to improve the flexibility of the electrode and promote the natural flow of cerebrospinal fluid, so as to better adapt to biological tissues. It helps to better maintain a good environment in the brain. The opening design can promote the circulation of cerebrospinal fluid, contribute to maintaining brain health, improve brain cleanliness and normal function, and thus reduce the abnormal deposition and aggregation of harmful proteins and the risk of other brain diseases.

[0101] Third, in terms of electrode wiring, all the conducting wires in the implantable electrode adopt an arc-shaped wiring design, smoothing the corners of the electrode contour, effectively reducing the non-uniformity during the etching process, and minimizing operation errors. In addition, the curved wiring can promote the smooth transition of signals, reduce the sudden change of impedance, improve signal transmission performance, and have good electromagnetic compatibility (EMC) advantages.

[0102] Fourth, the implantable electrode uses a large amount of flexible materials and has openings on the electrode to reduce the strength of the electrode, making it easy to deform, increasing its flexibility, improving the adaptability and flexibility of the electrode to cortical tissue, reducing the risk of potential inflammatory reactions, and being more suitable for long-term in-vivo recording.

[0103] Fifth, the size of the electrode contacts of the implantable electrode is designed at the micron level, which can be closer to neuron tissue and is closer in size to cortical functional columns - their size is between 100 and 500 microns, which is considered the basic unit of information processing. Such a size can obtain higher spatial resolution and finer information and has better biocompatibility.

[0104] Sixth, the preparation method of the implantable electrode is simpler. Poly(methyl methacrylate) (PMMA) is selected as the sacrificial layer material, which is convenient for peeling, simplifies the preparation process, reduces costs, and makes its production more environmentally friendly.

[0105] Seventh, the flexible support layer and encapsulation layer of the implantable electrode use low-temperature curing polyimide, and the curing temperature is lower than the melting point of PMMA, which can be better compatible with the PMMA sacrificial layer.

[0106] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. An implantable electrode, characterized in that: It includes: Flexible support layer; An electrode metal layer, wherein the electrode metal layer is disposed on the flexible supporting layer, and the electrode metal layer includes an electrode contact array area, a pad area and a conductive line; The electrode contact array region contains one or more electrode contacts, and the pad region contains one or more solder joints; each electrode contact is connected to a corresponding solder joint via a conductive line to form a connection path, and different connection paths are electrically isolated from each other; as well as an encapsulation layer, the encapsulation layer covers the electrode metal layer, and only forms an exposed surface at the electrode contact and the solder joint; the electrode metal layer comprises, from bottom to top, a titanium or chromium layer, a first platinum layer, a gold layer, and a second platinum layer, wherein the exposed surface at the electrode contact is formed by the material of the second platinum layer, and the exposed surface at the solder joint is formed by the material of the gold layer; The electrode contacts and the exposed surfaces of the solder joints are made of different materials to maintain consistency in signal transmission.

2. The implantable electrode according to claim 1, characterized in that The diameter of the electrode contact is 5 μm to 1000 μm.

3. The implantable electrode according to claim 1, characterized in that The thickness of the implantable electrode is 5 μm to 1000 μm, and the thickness of the electrode metal layer is 0.01 μm to 10 μm.

4. The implantable electrode according to claim 1, characterized in that The electrode contact array region also contains a plurality of holes penetrating the implantable electrode, wherein the holes are physically separated from the electrode contacts.

5. The implantable electrode according to claim 1, characterized in that The corners of the conductive lines are all curved.

6. The implantable electrode according to claim 1, characterized in that The materials of the flexible support layer and the packaging layer are both non-degradable low-temperature curing flexible materials, and the curing temperature of the flexible materials is lower than the melting point of PMMA.

7. The implantable electrode according to claim 6, characterized in that The flexible material is at least one of polyimide, SU-8, liquid crystal polymer and Parylene-C.

8. The implantable electrode according to claim 7, characterized in that The flexible material is low temperature curing polyimide.

9. The implantable electrode according to claim 1, characterized in that At least one of the electrode contacts is used for signal collection.

10. The implantable electrode according to claim 1, characterized in that At least one of the electrode contacts is used for electrical stimulation; the electrode contact for electrical stimulation has a 10mC / cm 2 ~100mC / cm 2 charge injection capacity.

11. The implantable electrode according to claim 10, characterized in that The electrode contacts for electrical stimulation have a 10 mC / cm 2 ~100mC / cm 2 charge storage capacity.

12. The implantable electrode according to claim 10, characterized in that The impedance of the electrode contacts used for electrical stimulation is 100 ohms to 10 megohms.

13. A method for preparing an implantable electrode according to any one of claims 1 to 12, characterized in that: It includes: providing a substrate; forming a sacrificial layer on the surface of the substrate; forming the flexible supporting layer on the sacrificial layer; Processing and forming the electrode metal layer on the flexible supporting layer; forming a packaging layer on the electrode metal layer and exposing the electrode contacts and the solder joints; The implantable electrode is released from the sacrificial layer.

14. The method for preparing an implantable electrode according to claim 13, characterized in that: The material of the sacrificial layer is PMMA; When forming the flexible support layer and the encapsulation layer, the material is solidified at a temperature lower than the melting point of PMMA.

15. The method for preparing an implantable electrode according to claim 14, characterized in that: The preparation method further comprises: After the implantable electrode is released from the sacrificial layer, the materials of the flexible support layer and the encapsulation layer are further cured by thermal step curing.

16. The method for preparing an implantable electrode according to claim 14, characterized in that: When releasing the implantable electrode from the sacrificial layer, the sacrificial layer is dissolved using an acetone solution.

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