A flexible electrode and a method of manufacturing the same

Abstract

The application discloses a flexible electrode and a preparation method thereof. The preparation method comprises the following steps: placing a first preset flexible electrode in a first modification solution, modifying a metal layer in the first preset flexible electrode to obtain a second preset flexible electrode; the first modification solution is an amino acid derivative solution containing a mercapto group and a primary amine group; placing the second preset flexible electrode in a second modification solution, modifying a first flexible substrate layer in the first preset flexible electrode; the second modification solution is an aqueous solution of an aliphatic compound; the aliphatic compound contains at least two primary amine groups; forming a second flexible substrate layer on the first flexible substrate layer and the metal layer, then performing etching treatment and releasing a device to obtain the flexible electrode. The surface of the first flexible substrate layer and the metal layer is modified by primary amination, so that the adhesion between the two flexible substrate layers and between the second flexible substrate layer and the metal layer is enhanced, and the service life of the flexible electrode is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brain-computer interface, in particular to a flexible electrode and a preparation method thereof. BACKGROUND

[0002] Brain-computer interface, sometimes also called "brain port" or "brain-machine fusion perception", is a direct connection path between the brain (or brain cell culture) of a human or animal and an external device. As a multi-disciplinary technology, brain-computer interface has attracted widespread attention from the scientific research community and the industry worldwide. As a branch of brain-computer interface, flexible electrode is considered as the "last form of brain-computer interface" due to its excellent biocompatibility.

[0003] In the prior art, the processing of high-throughput flexible electrodes is generally based on MEMS (Micro-Electro-Mechanical Systems) processing technology, and the processing process includes the stacking and compounding between multiple layers of organic polymers and metal inorganics. The existing electrode metal layer and polymer layer are adhered together by van der Waals force, which is a physical adsorption effect. The adhesion force gradually decreases during use or aging process, and finally leads to delamination of the electrode and shedding of the metal, affecting the long-term use of the electrode (such as shown in Figure 1

[0004] Therefore, how to improve the bonding force between the polymers in the flexible electrode and between the polymer and the metal layer, and improve the service life of the flexible electrode, has become a technical problem to be solved. SUMMARY

[0005] In order to solve the above technical problems, the embodiments of the present application provide a technical scheme of a flexible electrode and a preparation method thereof, and the technical scheme is as follows:

[0006] In one aspect, the embodiments of the present application provide a preparation method of a flexible electrode, and the preparation method comprises:

[0007] obtaining a first preset flexible electrode; the first preset flexible electrode comprises, from bottom to top, a substrate layer, a sacrificial layer, a first flexible substrate layer and a first photoresist layer; a metal layer is sputtered in the first photoresist layer, and the sacrificial layer partially covers the substrate layer;

[0008] placing the first preset flexible electrode in a first modification solution to modify the metal layer, and removing the first photoresist layer after the modification to obtain a second preset flexible electrode; the first modification solution is an amino acid derivative solution containing thiol and primary amine groups;

[0009] ​placing the second preset flexible electrode in a second modification solution to modify the first flexible substrate layer; the second modification solution is an aqueous solution of an aliphatic compound; the aliphatic compound contains at least two primary amine groups;

[0010] forming a second flexible substrate layer on the first flexible substrate layer and the metal layer, and etching the second flexible substrate layer to expose part of the metal layer;

[0011] removing the substrate layer and the sacrificial layer covered by the sacrificial layer to obtain a flexible electrode.

[0012] In a possible implementation, the metal layer includes a first metal layer and a second metal layer, the first metal layer is located on the surface of the first flexible substrate layer, and the second metal layer is located on the surface of the first metal layer; the method of placing the first preset flexible electrode in a first modification solution to modify the metal layer, and removing the first photoresist layer after the modification to obtain a second preset flexible electrode includes:

[0013] configuring a first preset concentration of a thiol and primary amine group-containing amino acid derivative solution; the first preset concentration is between 20 mmol / L and 200 mmol / L;

[0014] immersing the second metal layer in the first preset concentration of the thiol and primary amine group-containing amino acid derivative solution to modify the first preset flexible electrode;

[0015] cleaning and drying the first preset flexible electrode to obtain a modified first preset flexible electrode;

[0016] stripping the modified first preset flexible electrode to remove the first photoresist layer and expose the metal layer and the first flexible substrate layer to obtain the second preset flexible electrode.

[0017] In a possible implementation, the method of placing the second preset flexible electrode in a second modification solution to modify the first flexible substrate layer includes:

[0018] configuring a second modification solution with a preset volume fraction; the preset volume fraction is between 5% and 20%;

[0019] placing the second preset flexible electrode in the second modification solution with the preset volume fraction to modify the first flexible substrate layer;

[0020] cleaning and drying the second preset flexible electrode.

[0021] In a possible implementation, the forming a second flexible substrate layer on the first flexible substrate layer and the metal layer, and performing etching treatment on the second flexible substrate layer to expose part of the metal layer, comprises:

[0022] performing spin coating of polyimide on the surface of the first flexible substrate layer and curing treatment, to obtain the second flexible substrate layer covering the surface of the first flexible substrate layer and the metal layer;

[0023] forming a hard mask layer and a second photoresist layer on the surface of the second flexible substrate layer in sequence;

[0024] performing patterning treatment on the second photoresist layer to remove part of the second photoresist layer, to expose a to-be-etched region of the hard mask layer;

[0025] performing etching treatment on the hard mask layer in the to-be-etched region by using a hard mask layer etching solution, to form a patterned hard mask layer;

[0026] removing the second photoresist layer;

[0027] performing deep silicon etching treatment on the second flexible substrate layer and the first flexible substrate layer not covered by the patterned hard mask layer, to expose part of the metal layer, and to form a through hole penetrating through the second flexible substrate layer and the first flexible substrate layer.

[0028] In a possible implementation, the removing the substrate layer covered by the sacrificial layer and the sacrificial layer to obtain a flexible electrode comprises:

[0029] removing the patterned hard mask layer by using a hard mask layer etching solution;

[0030] removing part of the substrate layer covered by the sacrificial layer and removing the sacrificial layer to obtain the flexible electrode.

[0031] In a possible implementation, the method for manufacturing the first flexible electrode comprises:

[0032] obtaining a cleaned substrate as a substrate layer;

[0033] depositing a sacrificial layer on the surface of the substrate layer;

[0034] performing etching treatment on the sacrificial layer to form a patterned sacrificial layer, to expose a first region of the substrate layer;

[0035] performing spin coating of polyimide on the surface of the patterned sacrificial layer and curing treatment, to obtain the first flexible substrate layer; the first flexible substrate layer covers the patterned sacrificial layer and the first region;

[0036] forming the first photoresist layer on a surface of the first flexible substrate layer, and performing a patterning process on the first photoresist layer to form a wiring area in the first photoresist layer;

[0037] forming the metal layer in the wiring area by using a metal evaporation process.

[0038] In a possible implementation, the forming the metal layer in the wiring area by using a metal evaporation process includes:

[0039] forming the first metal layer and the second metal layer in the wiring area by using a metal evaporation process in sequence; a thickness ratio of the first metal layer and the second metal layer is between 1:10 and 1:50, a thickness of the first metal layer is between 50 Å and 500 Å, and a thickness of the second metal layer is between 500 Å and 5000 Å.

[0040] In a possible implementation, before the forming the metal layer in the wiring area by using a metal evaporation process, the method further includes:

[0041] forming an adhesion layer in the wiring area; a material of the adhesion layer is at least one of Ti, Ni, W, and TiW.

[0042] In a possible implementation, a thickness of the first flexible substrate layer is between 1 μm and 10 μm, and a thickness of the second flexible substrate layer is between 1 μm and 20 μm.

[0043] In another aspect, the embodiments of the present application further provide a flexible electrode, which is prepared by using the preparation method of the flexible electrode.

[0044] a second flexible substrate layer;

[0045] a first flexible substrate layer; the first flexible substrate layer is located on a lower surface of the second flexible substrate layer, and the first flexible substrate layer and the second flexible substrate layer are provided with a metal layer and a through hole penetrating through the first flexible substrate layer and the second flexible substrate layer, and one side surface of the metal layer is exposed to air;

[0046] a substrate layer; the substrate layer is located on a lower surface of the first flexible substrate layer.

[0047] In another aspect, the embodiments of the present application further provide an electronic device, which includes the flexible electrode or the flexible electrode prepared by using the preparation method.

[0048] In another aspect, the application also provides a brain-computer interface, which comprises the flexible electrode as described above or the flexible electrode prepared by the preparation method as described above; one end of the flexible electrode is used for collecting electroencephalogram signals, and the other end of the flexible electrode is used for outputting electrical signals to a signal processing device.

[0049] The flexible electrode and the preparation method thereof provided by the application have the following technical effects:

[0050] The application discloses a flexible electrode and a preparation method thereof. The preparation method comprises the following steps: placing a first preset flexible electrode in a first modification solution, performing modification treatment on a metal layer, and removing a first photoresist layer to obtain a second preset flexible electrode. The first preset flexible electrode comprises, from bottom to top, a substrate layer, a sacrificial layer, a first flexible base layer and the first photoresist layer. The metal layer is sputtered in the first photoresist layer. The first modification solution is an amino acid derivative solution containing a mercapto group and a primary amine group. The second preset flexible electrode is placed in a second modification solution to perform modification treatment on the first flexible base layer. The second modification solution is an aqueous solution of an aliphatic compound. The aliphatic compound contains at least two primary amine groups. A second flexible base layer is formed on the first flexible base layer and the metal layer, and etching treatment is performed on the second flexible base layer to expose part of the metal layer. The substrate layer and the sacrificial layer covered by the sacrificial layer are removed to obtain the flexible electrode. The preparation method performs primary amine modification on the surfaces of the first flexible base layer and the metal layer, so that the adhesion between the second flexible base layer and the first flexible base layer and between the second flexible base layer and the metal layer is enhanced, thereby prolonging the service life of the flexible electrode. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0052] Figure 1 is a microstructure diagram of a flexible electrode in the prior art provided by the embodiments of the application.

[0053] Figure 2 is a flowchart of a preparation method of a flexible electrode provided by the embodiments of the application.

[0054] Figure 3 is a structural diagram of a first preset flexible electrode provided by the embodiments of the application.

[0055] Figure 4is a corresponding process flow chart of a preparation method of a first preset flexible electrode provided by an embodiment of the present application.

[0056] Figure 5 is a corresponding process flow chart of a preparation process of a metal layer provided by an embodiment of the present application.

[0057] Figure 6 is a corresponding process flow chart of a surface modification process of a metal layer provided by an embodiment of the present application.

[0058] Figure 7 is a corresponding process flow chart of a surface modification of a first flexible substrate layer provided by an embodiment of the present application.

[0059] Figure 8 is a corresponding process flow chart of a preparation method of a flexible electrode provided by an embodiment of the present application.

[0060] Figure 9 is a corresponding process flow chart of a preparation method of a flexible electrode provided by an embodiment of the present application Figure 2 .

[0061] Figure 10 is a structural schematic diagram of a flexible electrode provided by an embodiment of the present application.

[0062] Hereinafter, the reference signs are described:

[0063] 1-substrate layer; 2-sacrificial layer; 3-first flexible substrate layer; 4-first photoresist layer; 5-metal layer; 51-first metal layer; 52-second metal layer; 6-second flexible substrate layer; 7-hard mask layer; 8-second photoresist layer; 9-via hole. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0065] It should be noted that in the description of the application, the following terms have the following definitions unless a different definition is set forth in the claims or elsewhere in the specification. All numerical values are defined as being "about" unless explicitly indicated otherwise. The term "about" generally refers to a range of numerical values, which those of ordinary skill in the art would recognize as equivalent to the recited value to produce substantially the same physical, functional, or chemical result. A numerical range expressed by a low value and a high value is defined to include all numerical values falling within the range, and all sub-ranges included within the range.

[0066] It should be noted that the terms "first", "second", and the like, used in the description and in the claims of the present application as well as above-described drawings, are used to distinguish between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of such terms in some contexts can be interchanged with one another, and the embodiments of the application described herein are capable of

[0067] It should be noted that in the description of the application, the terms "on", "over", "above", "up" are meant to include the meanings of these terms in the broadest sense, meaning that the description of the terms "on", "over", "above", "up" are interpreted to mean that the component can be disposed directly in contact with another component, or that there can be intervening components or layers between the component and the component. In addition, for the purposes of this description, spatially relative terms, such as "below", "beneath", "under", "above", "over", "up", "down", "downward", "upward", "vertical", "horizontal", and the like, can be used herein for ease of description to describe one element or component's or portion's relationship to another element, component or portion as illustrated in the figures. Spatially relative terms can be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device can be otherwise oriented (rotated 90° or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0068] The term "layer" as used in this application refers to a portion of material that includes a region having a thickness. A layer can extend over an entire underlying or overlying structure, or can extend over a partial area of an underlying or overlying structure. Further, a layer can be a region of a homogenous or inhomogenous continuous structure having a thickness that is less than the thickness of the continuous structure. For example, a layer can be between a top surface and a bottom surface of a continuous structure or between any pair of horizontal planes between the top surface and the bottom surface. A layer can extend horizontally, vertically, and / or along a tapered surface. A layer can include multiple layers. For example, a semiconductor layer can include one or more doped or undoped semiconductor layers and can have the same or different materials.

[0069] The flexible electrode has certain application scenarios in the fields of flexible medical sensors, wearable sensors and the like, such as being applied to a brain-computer interface, which is a direct connection path established between a human or animal brain (or a culture of brain cells) and an external device. The flexible electrode, as a branch of the brain-computer interface, is considered to be the "last form of the brain-computer interface" due to its superior biocompatibility. As described above, the adhesion between polymers and between polymers and metal layers in the flexible electrode is mainly physical adsorption, and the adhesion gradually decreases during use or aging, eventually leading to electrode delamination and metal peeling, Figure 1 A microstructure diagram of a prior art flexible electrode is shown, Figure 1 which can be obtained by an optical microscope, Figure 1 As shown, electrode delamination and partial metal peeling occur in the flexible electrode, which will affect the service life of the flexible electrode.

[0070] Therefore, in order to solve the above technical problems, the embodiments of the present application provide a preparation method of a flexible electrode, as shown in Figure 2 The preparation method comprises the following steps:

[0071] S01: obtaining a first preset flexible electrode; the first preset flexible electrode comprises, from bottom to top, a substrate layer 1, a sacrificial layer 2, a first flexible substrate layer 3, and a first photoresist layer 4; a metal layer 5 is sputtered in the first photoresist layer 4, and the sacrificial layer 2 partially covers the substrate layer 1.

[0072] In the embodiments of the present application, Figure 3 A structural schematic diagram of the first preset flexible electrode is shown, and the lowermost layer of the first preset flexible electrode is a substrate layer 1, which is used to provide support and film-forming substrate for the entire flexible electrode. Optionally, the substrate layer 1 can be a metal substrate, a semiconductor substrate, a sapphire substrate, a plastic substrate, a glass substrate, etc., and preferably, a silicon substrate such as a silicon wafer can be used. Optionally, the thickness of the substrate layer 1 can be 10 μm-1000 μm.

[0073] Please continue to refer to Figure 3 The first preset flexible electrode further comprises a sacrificial layer 2 located on the surface of the substrate layer 1, and the sacrificial layer 2 partially covers the substrate layer 1, so that part of the substrate layer 1 directly contacts the first flexible substrate layer 3 above the sacrificial layer 2. Optionally, the material of the sacrificial layer 2 is one or a combination of several materials such as aluminum, silicon oxide and nickel. Optionally, the thickness of the sacrificial layer 2 is between 0.5 μm and 5 μm.

[0074] The first flexible substrate layer 3 covers the surface of the sacrificial layer 2 and the substrate layer 1 which is not covered by the sacrificial layer 2, and the material of the first flexible substrate layer 3 is a flexible organic polymer material capable of film formation, which satisfies the stringent requirements of ultralow modulus (matching the Young's modulus of brain tissue, between 1 kPa-10 kPa), high biocompatibility, micromachinability and long-term stability. Optionally, the material of the first flexible substrate layer 3 can be polyimide (PI).

[0075] The first photoresist layer 4 is located on the surface of the first flexible substrate layer 3, for positioning the position of the metal layer 5 and protecting the first flexible substrate layer 3 in the forming process of the metal layer 5. The metal layer 5 is provided in the first photoresist layer 4, and the metal layer 5 is a lead and an electrode in the flexible electrode, and the metal layer 5 is exposed to the air.

[0076] In an optional embodiment, as shown in Figure 4 The application further provides a preparation method of the first flexible electrode, which comprises the following steps:

[0077] S001: obtaining a cleaned substrate as a substrate layer 1;

[0078] S002: depositing a sacrificial layer 2 on the surface of the substrate layer 1;

[0079] S003: performing etching treatment on the sacrificial layer 2 to form a patterned sacrificial layer 2, so as to expose a first area of the substrate layer 1;

[0080] S004: spin-coating polyimide on the surface of the patterned sacrificial layer 2 and performing solidification treatment to obtain the first flexible substrate layer 3; the first flexible substrate layer 3 covers the patterned sacrificial layer 2 and the first area;

[0081] S005: forming the first photoresist layer 4 on the surface of the first flexible substrate layer 3, and performing patterned treatment on the first photoresist layer 4 to form a wiring area in the first photoresist layer 4;

[0082] S006: forming the metal layer 5 in the wiring area by using a metal evaporation process.

[0083] In the embodiment of the application, the cleaned substrate refers to a substrate with a clean and pollution-free surface, and the use of the cleaned substrate as the substrate layer 1 can avoid pollution of the flexible electrode. Then the sacrificial layer 2 is deposited on the surface of the substrate layer 1, and optionally, the material of the sacrificial layer 2 is one or a combination of aluminum, silicon oxide, nickel and the like. Optionally, the thickness of the sacrificial layer 2 is between 0.5 μm-5 μm.

[0084] In the above step S003, please refer to Figure 4The sacrificial layer 2 is patterned according to a preset pattern, so that part of the sacrificial layer 2 is etched to form a patterned sacrificial layer 2, and part of the substrate layer 1 is exposed.

[0085] In step S004, the first flexible substrate layer 3 is prepared on the patterned sacrificial layer 2. Specifically, polyimide (PI) is spin-coated by using a glue spreader, and the first flexible substrate layer 3 is obtained after curing treatment. Alternatively, the polyimide (PI) can also be coated by spraying or scraping. The curing treatment can be heating at a curing temperature, and the curing temperature can be set based on the material of the first flexible substrate layer 3. Alternatively, the curing temperature can be 350-380°C. Alternatively, the curing treatment can be performed by using a vacuum oven with stepwise temperature rising. It should be noted that the highest temperature of the curing treatment is not higher than 380°C, so as to avoid excessive temperature causing imidization reaction of the polyimide material, thereby avoiding the generation of other high-strength compound materials.

[0086] In an alternative embodiment, the thickness of the first flexible substrate layer 3 is between 1 μm and 10 μm.

[0087] In step S005, a first photoresist layer 4 is first deposited on the surface of the first flexible substrate layer 3, and a first photoetching pattern is formed in the first photoresist layer 4 by a photoetching patterning process, so as to expose part of the first flexible substrate layer 3. The part of the first photoresist layer 4 etched away is a wiring area, and the wiring area is used to form a metal wiring structure in the flexible electrode.

[0088] In a specific embodiment, the photoresist is spin-coated on the first flexible substrate layer 3 to form the first photoresist layer 4. The photoresist layer is photoetched and patterned by a mask exposure and developing process, so as to form a first photoetching pattern in the wiring area.

[0089] In step S006, based on the first photoetching pattern, a metal layer 5 is formed in the wiring area by a metal evaporation process, and the metal layer 5 is the aforementioned metal wiring structure.

[0090] In an alternative embodiment, in step S006, the metal layer 5 is formed in the wiring area by a metal evaporation process, including: the first metal layer 51 and the second metal layer 52 are sequentially formed in the wiring area by a metal evaporation process; the thickness ratio of the first metal layer 51 and the second metal layer 52 is between 1:10 and 1:30; the thickness of the first metal layer 51 is between 50 Å and 500 Å; and the thickness of the second metal layer 52 is between 500 Å and 5000 Å.

[0091] In the present application, as shown in FIG. 1, the flexible electrode 100 includes a substrate layer 1, a sacrificial layer 2, a first flexible substrate layer 3, a first photoresist layer 4, a metal layer 5, and a second photoresist layer 6. Figure 5As shown, the metal layer 5 comprises at least a first metal layer 51 and a second metal layer 52, and the metal layer 5 is prepared by at least two times of metal evaporation processes. Specifically, the first metal layer 51 and the second metal layer 52 respectively serve as the electrode and the lead, and the first metal layer 51 and the second metal layer 52 can be synchronously deposited by the metal evaporation process using the corresponding material, i.e., the electrode and the lead are synchronously deposited, or the first metal layer 51 and the second metal layer 52 can be respectively evaporated by multiple times of metal evaporation processes to deposit the first metal layer 51 and the second metal layer 52 with different materials in the wiring area on the first flexible substrate layer 3. Optionally, in order to ensure the signal transmission effect of the flexible electrode, the thickness ratio of the first metal layer 51 and the second metal layer 52 is between 1:10 and 1:50, the thickness of the first metal layer 51 is between 50 Å and 500 Å, and the thickness of the second metal layer 52 is between 500 Å and 5000 Å. Preferably, the thickness ratio of the first metal layer 51 and the second metal layer 52 is 1:30.

[0092] Optionally, the material of the first metal layer 51 is one or more of gold, platinum and copper. Preferably, the material of the first metal layer 51 is copper.

[0093] Optionally, the material of the second metal layer 52 is one or more of gold, platinum and copper. Preferably, the material of the second metal layer 52 is gold.

[0094] Optionally, the critical dimension (CD) of the first metal layer 51 and the second metal layer 52 is 2-10 μm, and preferably 5 μm.

[0095] In an optional embodiment, before the step S006, the method further comprises: forming an adhesion layer in the wiring area; and the material of the adhesion layer is at least one of Ti, Ni, W and TiW.

[0096] In the embodiments of the present application, the adhesion between the metal layer 5 and the first flexible substrate layer 3 can be improved by arranging the adhesion layer between the metal layer 5 and the first flexible substrate layer 3, so as to avoid the peeling of the metal layer 5.

[0097] Optionally, the thickness of the adhesion layer is 5-50 nm.

[0098] In an optional embodiment, before the step S001, the method further comprises: cleaning the substrate to obtain a cleaned substrate. Specifically, the substrate can be cleaned by using a cleaning liquid. Exemplarily, the cleaning liquid can be a mixed solution formed by concentrated sulfuric acid solution and hydrogen peroxide solution. By cleaning, the contaminants on the substrate can be removed, so that the surface of the substrate is free of contaminants, thereby facilitating the preparation of the first flexible substrate layer 3.

[0099] S03: The first preset flexible electrode is placed in the first modification solution to modify the metal layer 5, and the first photoresist layer 4 is removed after the modification treatment to obtain the second preset flexible electrode; the first modification solution is an amino acid derivative solution containing thiol and primary amine groups.

[0100] In this embodiment, the surface of the metal layer 5 is modified by a first modifying solution. Specifically, the first preset flexible electrode is placed in an amino acid derivative solution containing thiol and primary amine groups to modify the surface of the metal layer 5. Through the reaction between the thiol groups and the surface of the metal layer 5, the metal surface contains a certain amount of primary amine groups. Optionally, the amino acid derivative solution containing thiol and primary amine groups can be a cysteine ​​hydrochloride solution, an L-cysteine ​​solution, a cysteine ​​ester hydrochloride solution, etc.

[0101] After the modification process is completed, the first photoresist layer 4 on the surface of the first flexible substrate 3 is removed, exposing the metal layer 5 and the first flexible substrate 3.

[0102] In a specific embodiment, taking gold as the metal layer 5 and cysteine ​​hydrochloride solution as the first modification solution, the surface modification of metal layer 5 in step S03 will be explained. Gold reacts with the -SH group in the cysteine ​​hydrochloride solution, and the terminal primary amine groups in the cysteine ​​hydrochloride solution perform primary amination modification on the gold surface, giving the surface of metal layer 5 certain primary amine groups. The reaction formula for the modification process is shown below:

[0103] ;

[0104] In one alternative implementation, such as Figure 6 As shown, the metal layer 5 includes a first metal layer 51 and a second metal layer 52. The first metal layer 51 is located on the surface of the first flexible substrate layer 3, and the second metal layer 52 is located on the surface of the first metal layer 51. In step S03 above, placing the first preset flexible electrode in a first modification solution to modify the metal layer 5, and removing the first photoresist layer 4 after modification to obtain the second preset flexible electrode, includes:

[0105] S031: Prepare a solution of an amino acid derivative containing thiol and primary amine groups at a first preset concentration; the first preset concentration is between 20 mmol / L and 200 mmol / L.

[0106] In the embodiments of the present application, the first preset concentration of the amino acid derivative solution containing thiol and primary amine groups is used as the first modification solution, and the first preset concentration is 20-200 mmol / L. The first modification solution is configured by deionized water and the corresponding amino acid derivative containing thiol and primary amine groups. For example, the first modification solution can be a 20-80 mmol / L cysteamine hydrochloride solution, and preferably, the first modification solution can be a 50 mmol / L cysteamine hydrochloride solution.

[0107] S033: The second metal layer 52 in the first preset flexible electrode is immersed in the first preset concentration of the amino acid derivative solution containing thiol and primary amine groups for modification treatment.

[0108] In the embodiments of the present application, as shown in Figure 6 The modification of the metal layer 5 refers to the modification of the surface of the metal layer 5, and more specifically, the surface of the second metal layer 52 is modified by primary amine. The second metal layer 52 in the first preset flexible electrode is immersed in the first modification solution for modification treatment.

[0109] Optionally, the reaction is carried out at room temperature.

[0110] Optionally, the reaction time of the modification reaction of the first flexible substrate layer 3 is between 0.5 h and 3 h.

[0111] Optionally, the second metal layer 52 is immersed in the first modification solution for modification treatment, which can be immersed in the solution as a whole, or only the surface of the second metal layer 52 can be immersed in the first modification solution.

[0112] S035: The first preset flexible electrode is subjected to cleaning treatment and drying treatment to obtain a modified first preset flexible electrode.

[0113] In the embodiments of the present application, the second metal layer 52 is immersed in the first modification solution for a corresponding reaction time, and then the first preset flexible electrode is subjected to cleaning treatment, and then drying treatment is performed to obtain a modified first preset flexible electrode. Optionally, isopropyl alcohol is used for cleaning treatment, and the drying treatment is carried out in a nitrogen atmosphere.

[0114] S037: The modified first preset flexible electrode is subjected to stripping treatment to remove the first photoresist layer 4, so that the metal layer 5 and the first flexible substrate layer 3 are exposed to obtain the second preset flexible electrode.

[0115] In the embodiment of the present application, the first preset flexible electrode after modification is subjected to stripping treatment to remove the first photoresist layer 4, so that the second metal layer 52 and the first flexible substrate layer 3 are exposed and treated, and a second preset flexible electrode is obtained. Optionally, the first photoresist layer 4 is removed by using acetone, and in the stripping process of the first photoresist layer 4, the metal layer 5 on the first photoresist layer 4 is stripped together. The surface of the first flexible substrate layer 3 in the second preset flexible electrode obtained after stripping only retains the first metal layer 51 and the second metal layer 52 in the wiring area.

[0116] In the embodiment of the present application, the surface of the metal is modified by primary amination, so that the surface has a certain content of primary amine groups, thereby laying a foundation for improving the interfacial force by forming chemical bond in the subsequent packaging process of the flexible electrode.

[0117] S05: The second preset flexible electrode is placed in a second modification solution to modify the first flexible substrate layer 3; the second modification solution is an aqueous solution of an aliphatic compound; the aliphatic compound contains at least two primary amine groups.

[0118] In the embodiment of the present application, as shown in Figure 7 The surface of the first flexible substrate layer 3 is modified by using a second modification solution, the second modification solution is an aliphatic compound containing at least two primary amine groups, the first flexible substrate is polyimide (PI), and in the modification process, the second modification solution can make the surface of the polyimide (PI) undergo primary amination reaction, so that the surface of the first flexible substrate layer has a certain content of primary amine groups.

[0119] Optionally, the aliphatic compound containing at least two primary amine groups can be hexanediamine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, etc.

[0120] Optionally, when the aliphatic compound containing at least two primary amine groups contains only two primary amine groups, the two primary amine groups are located at the ends of the molecular chain of the aliphatic compound. When the aliphatic compound contains more than two primary amine groups, at least two primary amine groups are located at the ends of the molecular chain of the aliphatic compound.

[0121] In a specific embodiment, the surface modification process of the first flexible substrate layer 3 is described by taking the second modification solution as an example, which is a hexanediamine solution, and the reaction equation of the modification process is as follows:

[0122] ;

[0123] During the modification process, the amino group of 1,6-hexanediamine attacks the nucleophilic ring-opening reaction of the ketone carbonyl group in the polyimide. Specifically, the amino group in the diamine acts as a nucleophile, using the lone pair of electrons on the nitrogen atom to attack the ketone carbonyl carbon atom in the imide ring (the carbon has a partial positive charge due to the polarity of C=O, making it susceptible to nucleophilic attack). The carbonyl double bond (C=O) is broken due to the nucleophilic attack, forming a negatively charged tetrahedral intermediate (the oxygen is negatively charged, and the carbon is bonded to the amino group). The intermediate re-forms a covalent bond between the carbonyl and the nitrogen by eliminating small molecules (such as hydrogen transfer or proton rearrangement), opening the imide ring, and finally forming an amide bond (CO CO NHX ), achieving the primary amine modification of the polyimide surface.

[0124] It should be noted that when the molecular formula of the aliphatic compound containing at least two primary amine groups contains more than two primary amine groups, only one primary amine group can undergo primary amine reaction with the polyimide.

[0125] In an alternative embodiment, in the above step S05, the modification treatment of the first flexible substrate layer 3 by placing the second pre-set flexible electrode in the second modification solution includes:

[0126] S051: configuring a second modification solution with a pre-set volume fraction; the pre-set volume fraction is between 5% and 20%;

[0127] S053: placing the second pre-set flexible electrode in the second modification solution with the pre-set volume fraction to perform modification treatment on the first flexible substrate layer 3;

[0128] S055: performing cleaning treatment and drying treatment on the second pre-set flexible electrode.

[0129] As mentioned before, the modification treatment of the first flexible substrate refers to the primary amine modification of the surface of the first flexible substrate layer 3. First, a second modification solution with a pre-set volume fraction concentration is configured, and the pre-set volume fraction is between 5% and 20%. For example, a 10% hexanediamine aqueous solution, a 15% 1,3-propanediamine, etc. can be used.

[0130] In the above step S053, the second pre-set flexible electrode is placed in the second modification solution with the pre-set volume fraction to perform primary amine modification on the surface of the first flexible substrate layer 3, so that the surface of the first flexible substrate layer 3 has a certain content of primary amine groups. In one embodiment, the second pre-set flexible electrode can be placed in the second modification solution with the pre-set volume fraction and incubated at a pre-set temperature for a pre-set time, the pre-set temperature is between 15 degrees Celsius and 30 degrees Celsius, and the pre-set time is between 18 hours and 30 hours. In a specific embodiment, the incubation reaction can be performed at room temperature for 24 hours.

[0131] In step S053 above, after the modification reaction is completed, the second flexible electrode is cleaned and dried, thus completing the modification treatment of the first flexible substrate layer 3. In a specific embodiment, isopropanol is used to clean the modified second pre-designed flexible electrode, and then it is dried under a nitrogen atmosphere.

[0132] S07: A second flexible substrate layer 6 is formed on the first flexible substrate layer 3 and the metal layer 5, and the second flexible substrate layer 6 is etched to expose a portion of the metal layer 5.

[0133] In this application, the material of the second flexible substrate layer 6 is a flexible organic polymer material capable of film formation. This material meets stringent requirements such as ultra-low modulus (matching the Young's modulus of brain tissue, between 1 kPa and 10 kPa), high biocompatibility, micromachinability, and long-term stability. Optionally, the material of the second flexible substrate layer 6 can be polyimide (PI). By using the above-mentioned flexible material, a uniform thickness and density, highly flexible, and biocompatible electrode support matrix is ​​formed, protecting the electrode layer and improving the flexibility, safety, and applicability of the flexible electrode. In brain-computer interface applications, it can reduce the implantation traces of the flexible electrode, thereby helping to shorten the postoperative recovery period of brain tissue.

[0134] Specifically, such as Figure 8 As shown, the second flexible substrate layer 6 serves as a sealing and protective layer, covering the first flexible substrate layer 3 and the metal layer 5. Since steps S03 and S05 respectively completed the primary amination modification of the metal layer 5 and the first flexible substrate layer 3, the surfaces of the first flexible substrate layer 3 and the metal layer 5 have certain primary amine groups. Thus, during the formation of the second flexible substrate layer 6, the first flexible substrate layer 3 and the metal layer 5 participate as reactants in the polymerization process of the second flexible substrate layer 6, realizing the in-situ growth of the second flexible substrate layer 6 on the metal layer 5 and the first flexible substrate layer 3. Consequently, not only are there van der Waals forces of physical interaction between the metal layer 5 and the second flexible substrate layer 6, and between the first flexible substrate layer 3 and the second flexible substrate layer 6, but also the effect of chemical bonds is introduced, increasing the bonding force between polymers and between metals and polymers.

[0135] In a specific embodiment, taking the metal layer 5 as gold and the first flexible substrate layer 3 and the second flexible substrate layer 6 as both polyimide (PI), please refer to the following reaction equation for the chemical interaction between the second flexible substrate layer 6 and the first flexible substrate layer 3:

[0136] ;

[0137] As shown in the above reaction equation, in the encapsulation process of the second flexible substrate layer 6 to the first flexible substrate layer 3 and the metal layer 5, since the surface of the first flexible substrate layer 3 contains primary amine groups, the primary amine groups on the surface of the first flexible substrate layer 3 can react with the second flexible substrate layer 6, specifically, the polyimide can replace the primary amine groups on the surface of the first flexible substrate layer 3, so that the first flexible substrate layer 3 and the second flexible substrate layer 6 are connected by covalent bonds. It should be noted that the above process is described by taking an example that the raw materials in the first modified solution only include two primary amine groups, and if the first modified solution includes more than two primary amine groups, only the reaction of PI replacing the primary amine groups will occur, and the structure of the polyimide will not be affected.

[0138] The chemical action between the second flexible substrate layer 6 and the metal layer 5 is as shown in the following reaction process:

[0139] ;

[0140] As shown in the above reaction equation, in the encapsulation process of the second flexible substrate layer 6 to the first flexible substrate layer 3 and the metal layer 5, since the surface of the metal layer 5 contains primary amine groups, in the preparation process of the second flexible substrate layer 6, the polyimide and the primary amine groups on the surface of the metal layer 5 again undergo primary amination reaction, and a covalent bond is formed, so that the second flexible substrate layer 6 and the metal layer 5 are not only connected by the van der Waals force of physical action, but also introduce Au-S bonds and covalent bonds, and the bonding force between the two interfaces is enhanced.

[0141] Please refer to Figure 8 After the second flexible substrate layer 6 is formed, etching treatment is performed on the second flexible substrate layer 6 to expose part of the surface of the metal layer 5.

[0142] In an optional embodiment, as shown in Figure 9 the step S07, the step of forming the second flexible substrate layer 6 on the first flexible substrate layer 3 and the metal layer 5, and performing etching treatment on the second flexible substrate layer 6 to expose part of the metal layer 5, comprises:

[0143] S071: spin-coating polyimide on the surface of the first flexible substrate layer 3 and performing curing treatment to obtain the second flexible substrate layer 6 covering the surfaces of the first flexible substrate layer 3 and the metal layer 5.

[0144] In the embodiments of the present application, the second flexible substrate layer 6 serves as a sealing encapsulation layer and forms a flexible part of the flexible electrode together with the first flexible sealing layer, thereby improving the flexibility, safety and applicability of the flexible electrode. In some embodiments, the thickness of the second flexible substrate layer 6 is between 1 μm and 20 μm. It can be understood that the thickness of the second flexible substrate layer 6 can be any value within the above range. By setting the thickness to the above range, the electrode is ensured to have high flexibility and to effectively protect the metal layer 5.

[0145] In some embodiments, the material of the second flexible substrate layer 6 is polyimide. The polyimide can be spin-coated on the surface of the first flexible substrate layer 3 and the electrode layer and the metal layer 5, and the second flexible substrate layer 6 is obtained after curing treatment. Here, the curing treatment refers to heating at a curing temperature. The curing temperature can be set based on the material of the second flexible substrate layer 6. Specifically, the curing temperature can be 350°C-380°C, and the maximum temperature is not more than 380°C, so as to avoid excessive temperature causing the polyimide material to undergo imidization reaction and generate other high-strength compound materials.

[0146] As described above, since the surface of the first flexible substrate layer 3 and the metal layer 5 is modified by primary amination and has a certain content of primary amine groups, in the preparation process of the second flexible substrate layer 6, the primary amine groups on the surface of the first flexible substrate layer 3 and the metal layer 5 react with the polyimide as a reactant, so that, in addition to the van der Waals force between the first flexible substrate layer 3 and the second flexible substrate layer 6, a chemical connection is established through a carbon-hydrogen covalent bond, and in addition to the van der Waals force between the metal layer 5 and the second flexible substrate layer 6, a connection is established through a metal-S bond and a covalent bond, thereby increasing the bonding force between the interfaces of the metal layer 5 and the second flexible substrate layer 6 and the first flexible substrate layer 3, relieving the problem of adhesion reduction, and improving the service life of the flexible electrode.

[0147] S072: sequentially forming a hard mask layer 7 and a second photoresist layer 8 on the surface of the second flexible substrate layer 6.

[0148] Please continue to see Figure 9 The material of the hard mask layer 7 can be metal or metal oxide, and specifically can include one or more of Al, SiO2, Ni, etc., and is preferably Al. The hard mask layer 7 can be formed on the second flexible substrate layer 6 by a sputtering process, and the thickness can be 2700-3300 angstroms, and preferably the thickness of the hard mask layer 7 can be 3000 angstroms. Please refer to Figure 9 The hard mask layer can be formed on the surface of the second flexible substrate layer 6 by a sputtering process.

[0149] The second photoresist layer 8 is used to form a second photoetching pattern, so that the hard mask layer is etched according to the second photoetching pattern in the subsequent steps. As shown inFigure 9 As shown in FIG. 7, a second photoresist layer 8 is formed on the surface of the hard mask layer 7.

[0150] S073: The second photoresist layer 8 is subjected to a patterning process to remove part of the second photoresist layer 8, thereby exposing the area to be etched of the hard mask layer 7.

[0151] Please continue to refer to Figure 9 , specifically, a patterned hard mask layer is formed by an etching process. The patterned hard mask layer can expose the area to be etched and cover other areas. Specifically, please refer to Figure 9 , the second photoresist layer 8 is first subjected to a patterning process to form a second photoresist pattern, which exposes the area to be etched on the hard mask layer.

[0152] S074: The hard mask layer 7 in the area to be etched is subjected to an etching process using a hard mask layer 7 etchant to form a patterned hard mask layer 7.

[0153] As shown in Figure 9 , the area to be etched is etched by a wet etching removal method to remove part of the hard mask layer in the area to be etched, thereby obtaining a patterned hard mask layer 7. Specifically, the area to be etched is etched using a hard mask layer etchant. For example, in the case of Al as the hard mask layer, an aluminum etchant is used to remove part of the hard mask layer, such as a BOE (Buffered Oxide Etchant) etchant to etch Al (or SiO2).

[0154] S075: The second photoresist layer 8 is removed.

[0155] As shown in Figure 9 , after the patterned hard mask layer 7 is formed, the second photoresist layer 8 is removed. Optionally, the second photoresist layer 8 can be peeled off using acetone.

[0156] S076: The second flexible substrate layer 6 and the first flexible substrate layer 3 not covered by the patterned hard mask layer 7 are subjected to a deep silicon etching process to expose part of the metal layer 5 and form a through hole 9 penetrating the second flexible substrate layer 6 and the first flexible substrate layer 3.

[0157] In the embodiments of the present application, as shown in Figure 9 , the second flexible substrate layer 6 and the first flexible substrate layer 3 are etched using the patterned hard mask layer as a mask to form a through hole 9 penetrating the second flexible substrate layer 6 and the first flexible substrate layer 3 and to partially expose the surface of the metal layer 5.

[0158] Specifically, the through hole 9 penetrates the second flexible substrate layer 6 and the first flexible substrate layer 3, so as to match other structures, improve the adhesion of the flexible electrode, and improve the stability and timeliness of the collection, transmission and recording of the electrical signal. In actual use, the size, position and number of the through hole 9 can be set according to the specific application scene and product demand.

[0159] Further, the electrode channel formed by etching penetrates the second flexible substrate layer 6 and stops at the surface of the metal layer 5, so that at least part of the surface of the metal layer 5 is exposed, thereby realizing the collection of the electrical signal. Optionally, the number of the electrode channel is determined according to the metal layer 5 and the signal transmission requirement. In this way, through the above steps S071-S076, not only the packaging of the metal layer 5 is completed, but also at the interface formed by the packaging, different from the traditional physical action, a chemical action is formed between the flexible substrate layers and between the flexible substrate layer and the metal layer 5, thereby making the packaging different from the traditional packaging process, realizing the interface enhancement effect, and avoiding the delamination of the electrode and the metal falling off, and improving the service life of the flexible electrode.

[0160] S09: removing the substrate layer 1 and the sacrificial layer 2 covered by the sacrificial layer 2 to obtain a flexible electrode.

[0161] Please refer to Figure 10 , removing part of the substrate layer 1 and the sacrificial layer 2 to release the device and obtain a flexible electrode. The removed part of the substrate layer 1 includes the substrate layer 1 covered by the sacrificial layer 2. Specifically, the removed part of the substrate layer 1 at least includes the region where the metal layer 5 is located. The unremoved substrate layer 1 serves as a support for the flexible electrode, facilitating the operation and probe connection.

[0162] In summary, the preparation method of the flexible electrode provided in the embodiments of the present application modifies the surfaces of the first flexible substrate layer 3 and the metal layer 5, so that the surfaces of both have a certain content of primary amine groups. Therefore, in the formation process of the second flexible substrate layer 6, the first flexible substrate layer 3 and the metal layer 5 participate in the polymerization process of the second flexible substrate layer 6 as reactants, realizing the in-situ growth of the second flexible substrate layer 6 on the metal layer 5 and the first flexible substrate layer 3. Further, the chemical bond effect is introduced between the metal layer 5 and the second flexible substrate layer 6, and between the first flexible substrate layer 3 and the second flexible substrate layer 6, in addition to the van der Waals force of the physical action, thereby increasing the bonding force between the polymers and between the metal and the polymers.

[0163] In an optional embodiment, the removing the substrate layer 1 and the sacrificial layer 2 covered by the sacrificial layer 2 in the step S09 to obtain a flexible electrode comprises:

[0164] S091: removing the patterned hard mask layer 7 by using a hard mask layer 7 etching liquid;

[0165] S093: removing the part of the substrate layer 1 covered by the sacrificial layer 2 and removing the sacrificial layer 2, to obtain the flexible electrode.

[0166] In the embodiments of the present application, referring to Figures 8-10 , the patterned hard mask layer is removed by using a hard mask layer etching solution. Optionally, when the hard mask layer is Al, an aluminum etching solution is used to remove the hard mask layer. Specifically, BOE etching solution (Buffered Oxide Etchant) is used to etch Al (or SiO2).

[0167] Then, the sacrificial layer 2 and the part of the substrate layer 1 covered by the sacrificial layer 2 are removed, and the removed part of the substrate layer 1 at least includes the area covering the metal layer 5. The structure of the obtained flexible electrode is shown in Figure 10 or Figure 8 In an optional embodiment, the removed part of the substrate layer 1 also includes the part covering the through hole 9, so as to facilitate adsorption, and the unremoved part of the substrate layer 1 is used to form an electrode support, facilitating operation and substrate connection.

[0168] It should be noted that, since the first flexible substrate layer 3 and the second flexible substrate layer 6 are preferably made of the same material, in the drawings, the first flexible substrate layer 3 and the second flexible substrate layer 6 are marked with the same color.

[0169] On the other hand, the present application also provides a flexible electrode prepared by the above method, as shown in Figure 10 , the flexible electrode comprises:

[0170] a second flexible substrate layer 6;

[0171] a first flexible substrate layer 3; the first flexible substrate layer 3 is located on the lower surface of the second flexible substrate layer 6, and the first flexible substrate layer 3 and the second flexible substrate layer 6 are provided with a metal layer 5 and a through hole 9 penetrating the first flexible substrate layer 3 and the second flexible substrate layer 6, and one side surface of the metal layer 5 is exposed to air;

[0172] a substrate layer 1; the substrate layer 1 is located on the lower surface of the first flexible substrate layer 3.

[0173] as shown in Figure 10As shown, the flexible electrode provided by the embodiment of the present application comprises, from bottom to top, a substrate layer 1, a first flexible base layer 3 and a second flexible base layer 6. The surface of the substrate layer 1 is equal to the surface area of the removed part of the patterned sacrificial layer 2, that is, the first flexible base layer 3 comprises two parts connected together, one part is deposited in the patterned sacrificial layer 2 during the forming process and directly covers the substrate layer 1, and the other part covers the sacrificial layer 2, the second flexible base layer 6 is located on the upper surface of the first flexible base layer 3, and the first flexible base layer 3 and the second flexible base layer 6 are provided with a through hole 9 and a metal layer 5, wherein the through hole 9 penetrates through the first flexible base layer 3 and the second flexible base layer 6, and the upper surface of the metal layer 5 is exposed to the air, and the other surfaces are surrounded by the first flexible base layer 3 and the second flexible base layer 6.

[0174] It should be noted that the flexible electrode embodiment and the preparation method of the flexible electrode embodiment are based on the same concept.

[0175] On the other hand, the embodiment of the present application also provides an electronic device, which comprises the flexible electrode as described above, or comprises the flexible electrode prepared by the preparation method as described above.

[0176] On the other hand, the embodiment of the present application also provides a brain-computer interface, which comprises the flexible electrode as described above, or comprises the flexible electrode prepared by the preparation method as described above; one end of the flexible electrode is used for collecting electroencephalogram signals, and the other end of the flexible electrode is used for outputting electrical signals to a signal processing device.

[0177] It should be noted that each of the embodiments in the present specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0178] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a flexible electrode, characterized in that, The preparation method includes: A first preset flexible electrode is obtained; the first preset flexible electrode includes, from bottom to top, a substrate layer, a sacrificial layer, a first flexible substrate layer, and a first photoresist layer; a wiring region is formed in the patterned first photoresist layer, a metal layer is sputtered in the wiring region, and the sacrificial layer partially covers the substrate layer; The first preset flexible electrode is placed in a first modification solution to modify the metal layer, and the first photoresist layer is removed after modification to obtain a second preset flexible electrode; the first modification solution is an amino acid derivative solution containing thiol and primary amine groups; the surface of the modified metal layer contains primary amine groups; The second preset flexible electrode is placed in the second modification solution to modify the first flexible substrate layer. The second modified solution is an aqueous solution of an aliphatic compound; the aliphatic compound contains two primary amine groups; A second flexible substrate layer is formed on the first flexible substrate layer and the metal layer, and the second flexible substrate layer is etched to expose a portion of the metal layer; the material of the second flexible substrate layer is polyimide, and during the formation of the second flexible substrate layer, the primary amine groups on the surface of the first flexible substrate layer and the primary amine groups on the surface of the metal layer react with the polyimide respectively; The substrate layer and the sacrificial layer, which are covered by the sacrificial layer, are removed to obtain a flexible electrode.

2. The preparation method according to claim 1, characterized in that, The metal layer includes a first metal layer and a second metal layer, wherein the first metal layer is located on the surface of the first flexible substrate layer, and the second metal layer is located on the surface of the first metal layer; the step of placing the first preset flexible electrode in a first modification solution to modify the metal layer, and removing the first photoresist layer after modification to obtain the second preset flexible electrode includes: Prepare a solution of an amino acid derivative containing thiol and primary amine groups at a first preset concentration; the first preset concentration is between 20 mmol / L and 200 mmol / L. The second metal layer in the first preset flexible electrode is modified by immersing it in a solution of amino acid derivatives containing thiol and primary amine groups of the first preset concentration. The first preset flexible electrode is cleaned and dried to obtain the modified first preset flexible electrode. The modified first preset flexible electrode is stripped to remove the first photoresist layer, exposing the metal layer and the first flexible substrate layer to obtain the second preset flexible electrode.

3. The preparation method according to claim 1, characterized in that, The step of placing the second preset flexible electrode in the second modification solution to modify the first flexible substrate layer includes: Prepare a second modified solution with a preset volume fraction; the preset volume fraction is between 5% and 20%. The second preset flexible electrode is placed in the second modified solution with the preset volume fraction to modify the first flexible substrate layer. The second preset flexible electrode is cleaned and dried.

4. The preparation method according to claim 1, characterized in that, The step of forming a second flexible substrate layer on the first flexible substrate layer and the metal layer, and etching the second flexible substrate layer to expose a portion of the metal layer, includes: Polyimide is spin-coated onto the surface of the first flexible substrate layer and then cured to obtain a second flexible substrate layer covering the surface of the first flexible substrate layer and the metal layer. A hard mask layer and a second photoresist layer are sequentially formed on the surface of the second flexible substrate layer; The second photoresist layer is patterned to remove part of the second photoresist layer and expose the area to be etched in the hard mask layer; The hard mask layer in the area to be etched is etched using a hard mask layer etchant to form a patterned hard mask layer; Remove the second photoresist layer; Deep silicon etching is performed on the second flexible substrate layer and the first flexible substrate layer not covered by the patterned hard mask layer to expose a portion of the metal layer and to form vias penetrating the second flexible substrate layer and the first flexible substrate layer.

5. The preparation method according to claim 4, characterized in that, The process of removing the substrate layer and the sacrificial layer covered by the sacrificial layer to obtain a flexible electrode includes: The patterned hard mask layer is removed using a hard mask layer etchant; The flexible electrode is obtained by removing the portion of the substrate layer covered by the sacrificial layer and removing the sacrificial layer.

6. The preparation method according to claim 2, characterized in that, The method for preparing the first preset flexible electrode includes: Obtain the cleaned substrate as the substrate layer; A sacrificial layer is deposited on the surface of the substrate layer; The sacrificial layer is etched to form a patterned sacrificial layer to expose a first region of the substrate layer; Polyimide is spin-coated onto the surface of the patterned sacrificial layer and then cured to obtain the first flexible substrate layer; the first flexible substrate layer covers the patterned sacrificial layer and the first region; The first photoresist layer is formed on the surface of the first flexible substrate layer, and the first photoresist layer is patterned to form a wiring area located in the first photoresist layer. The metal layer is formed in the wiring area using a metal vapor deposition process.

7. The preparation method according to claim 6, characterized in that, The process of forming the metal layer in the wiring area using a metal evaporation process includes: The first metal layer and the second metal layer are sequentially formed in the wiring area using a metal vapor deposition process; the thickness ratio of the first metal layer to the second metal layer is between 1:10 and 1:50, the thickness of the first metal layer is between 50 Å and 500 Å, and the thickness of the second metal layer is between 500 Å and 5000 Å.

8. The preparation method according to claim 6, characterized in that, Before forming the metal layer in the wiring area using a metal evaporation process, the method further includes: An adhesive layer is formed in the wiring area; the material of the adhesive layer is at least one of Ti, Ni, W, and TiW.

9. The preparation method according to any one of claims 1-8, characterized in that, The thickness of the first flexible substrate layer is between 1 μm and 10 μm; the thickness of the second flexible substrate layer is between 1 μm and 20 μm.

10. A flexible electrode, characterized in that, The flexible electrode is prepared by the method for preparing a flexible electrode according to any one of claims 1-9, and the flexible electrode comprises, from top to bottom: The second flexible substrate layer is made of polyimide. A first flexible substrate layer is located on the lower surface of a second flexible substrate layer. Both the first and second flexible substrate layers contain metal layers and through-holes penetrating both layers. One surface of the metal layer is exposed to air. The metal layer is modified with a first modifying solution, and the surface of the modified metal layer contains primary amine groups. The first modifying solution is a solution of an amino acid derivative containing thiol and primary amine groups. The first flexible substrate layer is modified with a second modifying solution, and the surface of the modified first flexible substrate layer contains primary amine groups. The second modifying solution is an aqueous solution of an aliphatic compound containing two primary amine groups. During the formation of the second flexible substrate layer, the primary amine groups on the surface of the first flexible substrate layer and the primary amine groups on the surface of the metal layer react with polyimide, respectively. Substrate layer; the substrate layer is located on the lower surface of the first flexible substrate layer.

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