A neural microelectrode with long-term biocompatibility maintenance and a preparation method thereof

Abstract

The application discloses a nerve microelectrode with long-term biocompatibility maintenance and a preparation method thereof. Most of the existing nerve electrodes have only a few recording points, so that the spatial resolution is low; the flexible electrode implantation has a large width, so that more trauma areas are caused. The nerve microelectrode with long-term biocompatibility maintenance for nerve recording comprises a recording layer, an electrochemical modification layer and a biocompatibility coating. The preparation of the biocompatibility polypeptide coating is realized by adopting a MEMS compatible PVD technology, so that the preparation efficiency and consistency of the electrode are greatly improved. The biocompatibility coating which completely covers the electrode points and the whole probe surface has a special porous nanofiber structure and can realize ion conduction. The electrode point recording performance is improved by using the electrochemical modification layer, so that the biocompatibility is improved without seriously affecting the electrode impedance and recording capacity.

Description

Technical Field

[0001] This invention belongs to the field of flexible biosensor fabrication technology for brain-computer interfaces; specifically, it relates to a neural microelectrode for neural recording with long-term biocompatibility maintenance and its microfabrication method. Background Technology

[0002] Neural electrodes convert extracellular ion currents into electrical signals, serving as a crucial hub for brain-computer interfaces and one of the most widely used tools for recording neural activity. Over the past few decades, research into different materials and structures has led to unprecedented improvements in the recording of physiological signals from neural electrodes, revealing immense therapeutic potential. On one hand, the rapid development of MEMS fabrication technology has enabled the miniaturization of neural electrodes, significantly improving the spatial resolution of electrode point recording. On the other hand, breakthroughs have been achieved in the implantation of neural electrodes in animals; Neuralink, for example, enabled monkeys to "type with their thoughts" on a screen through electrode implantation and stimulation. However, rejection and long-term stability of implanted neural electrodes remain critical issues that urgently need to be addressed. Inflammation caused by the mechanical mismatch between rigid electrodes and neural tissue can lead to implanted electrodes being covered by glial scarring within weeks or months, resulting in loss of recording ability and a lack of long-term reliability. To address these issues, novel neural electrode structures have been proposed to improve the long-term stability of implanted electrodes.

[0003] A review of existing technical literature reveals that long-term biocompatible microelectrodes primarily utilize extracellular matrix coating technology, silk fibroin modification technology, and anti-fouling coating modification technology. In their paper "Extracellular matrix-based intracortical microelectrodes: Toward a microfabricated neural interface based on natural materials," Professor Mark G. Allen and colleagues at Georgia Institute of Technology used extracellular matrix to encapsulate neural electrodes. This design minimizes the entry of non-natural products into the brain, reducing inflammatory responses compared to inorganic methods. In their paper "Silk as a Multifunctional Biomaterial Substrate for Reduced Glial Scarring around Brain-Penetrating Electrodes," Professor D.L. Kaplan and colleagues at Tufts University applied silk fibroin to the surface of flexible electrodes. The hydration of the silk fibroin facilitated the transformation of the electrode from rigid to flexible, reducing the mechanical mismatch between the electrode and biological tissue. In their paper "Anti-fouling peptide functionalization of ultraflexible neural probes for long-term neural activity recordings in the brain," Professor Fang Ying's research group at the National Center for Nanoscience and Technology, Chinese Academy of Sciences, significantly improved the anti-fouling properties of electrodes against proteins through zwitterionic peptide modification. This provided a stable physical and chemical interface with brain tissue and enabled long-term neural recording. However, these electrodes still have some shortcomings, such as a limited number of recording points leading to lower spatial resolution, and the larger implantation width of flexible electrodes resulting in more traumatic areas and increased inflammatory responses after implantation. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by using the flexible polymer Parylene and PI (polyimide) as the substrate for the recording electrode, and combining them with peptides to achieve neural recording and long-term biocompatibility maintenance. By combining the flexible polymer with peptides, the recording electrode can have good flexibility, thereby reducing brain tissue damage caused by mechanical mismatch. On the other hand, it can also ensure the stability of the electrode in vivo after implantation, thereby increasing the time that the electrode can work normally in vivo.

[0005] A neural microelectrode with long-term biocompatibility maintenance comprises a recording layer as the main body and consists of an electrode substrate and one or more probes. The probes are coated with a biocompatibility coating.

[0006] The recording layer comprises a conductive layer and an insulating layer. The conductive layer is located inside the insulating layer. The conductive layer includes recording electrode points at the probe tip, signal lines, and recording electrode pads on the electrode substrate. Different recording electrode points are connected to their corresponding recording electrode pads via independent signal lines.

[0007] The recording electrode points and recording electrode pads are exposed through windows on the insulating layer. All recording electrode points are provided with an electrochemical modification layer to reduce electrode impedance; the electrochemical modification layer is disposed within the windows on the insulating layer and inside the biocompatible coating.

[0008] Preferably, the electrochemical modification layer comprises a stacked nano-metal layer and a conductive polymer layer. The nano-metal layer is bonded to the recording electrode site. The conductive polymer layer is located on the side of the nano-metal layer away from the recording electrode site.

[0009] Preferably, the thickness of the nano-metal layer is 0.5μm-5μm and the material is Pt-Black; the thickness of the conductive polymer layer is 0.5μm-5μm and the material is PEDOT:PSS.

[0010] Preferably, the biocompatible coating has a thickness of 0.5μm-5μm and is made of peptides.

[0011] Preferably, the insulating layer consists of an upper insulating layer and a lower insulating layer. A conductive layer is disposed between the upper insulating layer and the lower insulating layer.

[0012] Preferably, the insulating layer is made of Parylene-C or polyimide.

[0013] Preferably, the conductive layer is a Cr / Au bilayer metal.

[0014] The method for preparing this neural microelectrode with long-term biocompatibility maintenance includes the following steps:

[0015] Step 1: Prepare the recording layer using Parylene-C or polyimide as the insulating layer.

[0016] Step 2: Use ACF conductive adhesive to achieve thermo-press bonding between the recording electrode pads and the flexible flat cable, and use an electrochemical workstation to electroplate the electrode surface to form an electrochemical modification layer.

[0017] Step 3: Deposit peptides on the probe surface of the electrode using PVD coating to form a biocompatible coating.

[0018] As a preferred option, the specific process of step one is as follows:

[0019] Step 1-1. Deposit a layer of Parylene-C on the substrate as a lower insulating layer using a high-vacuum thermal evaporation coating machine.

[0020] Step 1-2. Deposit a metal as a conductive layer on the lower insulating layer. The metal of the conductive layer is Cr / Au.

[0021] Steps 1-3. Coat the conductive layer with positive photoresist and pattern the photoresist using planar photolithography.

[0022] Steps 1-4. Use wet etching to pattern the Au layer and Cr layer in the conductive layer, forming multiple independent sets of recording electrode points, signal lines and recording electrode pads.

[0023] Steps 1-5. A layer of Parylene-C is deposited on the patterned conductive layer using a high-vacuum thermal evaporation coating machine as the upper insulating layer for the flexible neural microelectrode.

[0024] Steps 1-6. Deposit a layer of Cr on the upper insulating layer as a hard mask for reactive ion etching.

[0025] Steps 1-7. Coat the hard mask with positive photoresist and pattern the photoresist using planar photolithography.

[0026] Steps 1-8. Pattern the hard mask using wet etching.

[0027] Steps 1-9. Pattern the insulating layer using reactive ion etching. Remove the hard mask using wet etching to create windows that expose the electrode points and electrode pads.

[0028] Steps 1-10. Laser cut out the contours of each electrode.

[0029] As a preferred option, the specific process of step one is as follows:

[0030] Step 1-1. Deposit a metal layer as a sacrificial layer on the polished surface of the silicon wafer substrate.

[0031] Step 1-2. Spin-coat a layer of polyimide onto the sacrificial layer as the lower insulating layer of the microelectrode.

[0032] Steps 1-3. Deposit a metal layer as a conductive layer on the lower insulating layer. The conductive layer metal is Cr / Au.

[0033] Steps 1-4. Coat the conductive layer with positive photoresist and pattern the photoresist using planar photolithography.

[0034] Steps 1-5. Use wet etching to pattern the Au layer and Cr layer in the conductive layer.

[0035] Steps 1-6. Spin-coat a layer of polyimide onto the front side of the patterned metal layer as an upper insulating layer.

[0036] Steps 1-7. Deposit a layer of Cr on the upper insulating layer as a hard mask for reactive ion etching.

[0037] Steps 1-8. Coat the hard mask with positive photoresist and pattern the photoresist using planar photolithography.

[0038] Steps 1-9. Pattern the hard mask using wet etching.

[0039] Steps 1-10. Pattern the insulating layer using reactive ion etching. Remove the hard mask using wet etching to create windows that expose the electrode points and electrode pads.

[0040] Step 1-11. Laser cut out the outline of each electrode.

[0041] As a preferred option, the specific process of step two is as follows:

[0042] Step 2-1. Apply a layer of ACF conductive adhesive to the surface of the recording electrode pads and pre-press it.

[0043] Step 2-2. Attach the flexible flat cable to the ACF conductive adhesive and press it.

[0044] Steps 2-3. Immerse the recording electrode of the probe in chloroplatinic acid solution, connect the flexible flat cable using an electrochemical workstation, and electroplate the recording electrode to form a nano-metal (Pt-Black) layer.

[0045] Steps 2-4. Deposit a conductive polymer (PEDOT:PSS) layer on the surface of the nanometal (Pt-Black) layer at the recording electrode point.

[0046] As a preferred option, the specific process of step three is as follows:

[0047] Step 3-1. Place the polypeptide (specifically H-Phe-Phe-OH, two molecules of phenylalanine) and the electrode obtained in step 2 into a PVD coating machine.

[0048] Step 3-2. Reduce the air pressure inside the PVD coating machine to the predetermined value.

[0049] Step 3-3: Heat and evaporate the peptide to eliminate the barrier between the peptide and the electrode, so that the peptide forms a coating on the probe surface of the electrode.

[0050] Steps 3-4. Release the electrodes.

[0051] The beneficial effects of this invention are:

[0052] 1. The present invention forms a biocompatible coating of peptides on the probe surface, which helps to delay or avoid electrode failure; at the same time, the present invention reduces the impedance of the electrode by electrochemically modifying the electrode surface, thus overcoming the problem of excessive impedance caused by the biocompatible coating.

[0053] 2. The H-Phe-Phe-OH coating (peptide) prepared by this invention has a rough surface morphology and good antibacterial properties, enabling the microelectrode to achieve long-term biocompatibility.

[0054] 3. This invention uses MEMS-compatible PVD (physical vapor deposition) technology to prepare biocompatible peptide coatings, which can greatly improve the preparation efficiency and consistency of electrodes.

[0055] 4. The polypeptide coating H-Phe-Phe-OH prepared by PVD in this invention has a special porous nanofiber surface structure, which allows it to completely cover the entire electrode point and probe surface without seriously affecting its impedance and recording performance. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0057] Figure 2 This is a schematic diagram of the probe along its length in this invention (the signal line part in the figure is only for illustration; in the actual structure, each electrode point is led out to the corresponding pad through an independent signal line).

[0058] Figure 3a The impedance of a standard bare electrode, an electrochemically modified electrode, and an electrode with increased biocompatibility after electrochemical modification is compared with frequency.

[0059] Figure 3b Comparison of phase versus frequency for a standard bare electrode, an electrochemically modified electrode, and an electrode with increased biocompatibility after electrochemical modification;

[0060] Figure 4 This is a process flow diagram of step S1 in the preparation method of Embodiment 1 of the present invention.

[0061] Figure 5 This is a process flow diagram of step S1 in the preparation method of Embodiment 2 of the present invention. Detailed Implementation

[0062] The present invention will be further described below with reference to the accompanying drawings.

[0063] Example 1

[0064] like Figure 1 and 2 As shown, a neural microelectrode with long-term biocompatibility maintenance comprises a recording layer 1 as its main body, and is further divided into an electrode substrate 5 and multiple elongated probes 6 extending from the electrode substrate 5. Both the electrode substrate 5 and the probes 6 include the recording layer 1. Each recording electrode point 1-1 at the tip of the elongated probes 6 is provided with an electrochemical modification layer 2. All or part of the elongated probes 6 is coated with a biocompatibility coating 3. The biocompatibility coating 3 is made of peptides.

[0065] Recording layer 1 includes a conductive layer and an insulating layer 4. The insulating layer 4 is divided into an upper insulating layer and a lower insulating layer. The conductive layer is embedded between the upper and lower insulating layers. The insulating layer 4 is made of a flexible polymer material. The conductive layer is a Cr / Au bilayer metal; the Cr (chromium) layer is 20 nm thick; the Au (gold) layer is 200 nm thick.

[0066] The conductive layer includes a recording electrode point 1-1 located at the tip of probe 6, a signal line 1-4, a recording electrode pad 1-2 located on the electrode substrate 5, and a functional expansion pad 1-3. Multiple recording electrode points 1-1 on the same probe are led out to their corresponding recording electrode pads 1-2 via independent signal lines 1-4, forming a complete recording electrode structure to achieve the output of neural acquisition signals. The functional expansion pad 1-3 is a reserved pad for expanding different functions. The recording electrode point 1-1, recording electrode pad 1-2, and functional expansion pad 1-3 are all exposed through windows on the upper insulating layer.

[0067] An electrochemical modification layer 2 is disposed on all recording electrode points 1-1. The electrochemical modification layer 2 is embedded within a window of the upper insulating layer to reduce the impedance between the recording electrode point 1-1 and the nerve cell, thereby reducing the impedance of the neural signal acquisition output pathway. The electrochemical modification layer 2 comprises a nano-metal (i.e., Pt-Black) layer 2-1 and a conductive polymer (i.e., PEDOT:PSS) layer 2-2, stacked sequentially. The nano-metal layer 2-1 is attached to the recording electrode point 1-1. The conductive polymer layer 2-2 is located on the side of the nano-metal layer 2-1 away from the recording electrode point 1-1. PEDOT is a polymer of 3,4-ethylenedioxythiophene monomer; PSS is polystyrene sulfonate.

[0068] like Figure 3a and 3b As shown, at a frequency of 1 kHz, the impedance of the microelectrode after deposition of electrochemical modification layer 2 decreased by 83% compared to the bare microelectrode, and the phase delay was significantly reduced. Furthermore, after modification with biocompatible coating 3, the impedance of the microelectrode increased slightly (by 10 kΩ) compared to before modification, but it still decreased by 70% compared to the bare microelectrode, and the phase delay was basically the same as that of the microelectrode after deposition of electrochemical modification layer 2 alone.

[0069] The method for preparing this neural microelectrode with long-term biocompatibility maintenance includes the following steps:

[0070] S1: Using ultrathin Parylene-C as the insulating layer for the electrodes, multiple recording units are formed on the insulating substrate to obtain flexible neural microelectrodes. The specific process is as follows:

[0071] 1-1. Using double-sided polished soda-lime glass as a substrate, the soda-lime glass was sequentially immersed in acetone, ethanol, and deionized water for ultrasonic cleaning for 5 minutes each, then dried with nitrogen gas and baked in a 180℃ oven for 15 minutes. Figure 4 As shown in section (1), a Parylene-C layer was deposited on the front side of the substrate as the lower insulating layer of the flexible neural microelectrode using a high-vacuum thermal evaporation coating machine. The thickness of the lower insulating layer was 4 μm.

[0072] 1-2. For example Figure 4 As shown in section (2), a metal layer is deposited on the lower insulating layer as a conductive layer. The conductive layer metal is Cr / Au and the thickness is 20 / 200nm.

[0073] 1-3. For example Figure 4 As shown in section (3), positive photoresist AZ5214 is coated on the conductive layer and the photoresist is patterned using planar photolithography. The photoresist thickness is 2μm.

[0074] 1-4. For example Figure 4 As shown in section (4), wet etching is used to pattern the Au layer and Cr layer in the conductive layer, forming multiple independent sets of electrode points, signal lines 1-4 and electrode pads.

[0075] 1-5. For example Figure 4 As shown in section (5), a Parylene-C layer is deposited on the front side of the patterned metal layer using a high-vacuum thermal evaporation coating machine as the upper insulating layer of the flexible neural microelectrode. The thickness of the upper insulating layer is 4 μm.

[0076] 1-6. For example Figure 4 As shown in section (6), a 100 nm thick Cr layer is deposited on the upper insulating layer as a hard mask for subsequent reactive ion etching (RIE).

[0077] 1-7. For example Figure 4 As shown in section (7), positive photoresist AZ5214 is coated on a hard mask and patterned using planar photolithography. The photoresist thickness is 2μm.

[0078] 1-8. For example Figure 4 As shown in section (8), the hard mask is patterned using wet etching.

[0079] 1-9. For example Figure 4 As shown in section (9), the insulating layer is patterned using RIE. Subsequently, the hard mask is removed using wet etching to form windows that expose the electrode points and electrode pads.

[0080] 1-10. For example Figure 4 As shown in (10), the outlines of each electrode are cut out using a laser cutter, and the microelectrodes are soaked in ethanol and released using tweezers.

[0081] S2: ACF conductive adhesive is used to achieve thermo-press bonding of flexible microelectrode pads and flexible flat cables. Electroplating is used on the electrode surface using an electrochemical workstation to achieve modification. The specific process is as follows:

[0082] 2-1. Apply a layer of ACF conductive adhesive to the surface of the pads of the flexible neural microelectrode and pre-press it. The specific steps are as follows: use tape to fix the flexible neural electrode to the glass slide; apply the ACF conductive adhesive to the front of the pads; place the glass slide directly under the pressure head of the hot press, aligning the pressure head with the ACF conductive adhesive; adjust the pressure of the hot press to 0.14 MPa, the temperature to 140℃, and the hot pressing time to 5 seconds, and begin pre-pressing.

[0083] 2-2. Attach the flexible cable FPC to the ACF conductive adhesive and perform the pressing. The specific steps are as follows: Align the pads on the flexible cable FPC with the pads on the flexible neural electrode; attach the flexible FPC to the ACF conductive adhesive; place the glass slide directly under the pressure head of the hot press, aligning the pressure head with the ACF conductive adhesive; adjust the pressure of the hot press to 0.18 MPa, the temperature to 240℃, and the hot pressing time to 15 seconds to perform the pressing.

[0084] 2-3. Pt-Black was modified on the recording electrode surface of the flexible neural microelectrode. The specific steps were as follows: The FPC interface connecting the microelectrode was assembled onto the PCB adapter head; the reference electrode, counter electrode, and working electrode were connected to their respective interfaces one by one; the electrochemical workstation was started, and the needle handle of the microelectrode was immersed in chloroplatinic acid solution; the current was set to 3.18 × 10⁻⁶. -5 A / cm 2 The process is repeated 200 times, and a step method is used to electroplate a single electrode point to form a nano-metal layer.

[0085] 2-4. Deposit a conductive polymer layer on the surface of the nano-metal layer at the electrode points. The specific steps are as follows: connect the reference electrode, counter electrode, and working electrode to their respective interfaces one by one; start the electrochemical workstation and immerse the needle handle of the microelectrode in a PEDOT:PSS solution; set a constant current of 7 × 10⁻⁶. -9 A / cm 2 Electroplating is performed on a single electrode for 600 seconds.

[0086] S3: Long-term biocompatibility is achieved by depositing peptides on the electrode surface using PVD coating. The specific process is as follows:

[0087] 3-1. Place the peptide and microelectrode into the PVD coating machine. The specific steps are as follows: Weigh H-Phe-Phe-OH into a crucible and place it on the heating cylinder in the PVD coating machine; open the baffle corresponding to the heating source and fix the microelectrode on the platform behind the baffle; close the baffle and close the chamber.

[0088] 3-2. Reduce the chamber pressure to the predetermined value. The specific steps are as follows: Turn on the mechanical pump to reduce the chamber pressure to 5 Pa; open the solenoid valve and wait for it to fully operate, reducing the chamber pressure to 5 × 10⁻⁶ Pa. -4 Pa.

[0089] 3-3. Heating and evaporating the peptide. The specific steps are as follows: turn on the heating source and set the heating temperature to 220℃; wait for H-Phe-Phe-OH to heat up to 180℃ and then open the baffle; wait for the heating source to continue heating up to 220℃ and maintain this state for 60 seconds, then close the baffle.

[0090] The fourth step is to release the microelectrode. The specific steps are as follows: turn off the heating source to cool the device; turn off the solenoid valve and wait for it to stop completely; turn off the mechanical pump and open the vent valve to restore the air pressure in the chamber to atmospheric pressure; open the chamber and release the microelectrode modified with the biocompatible coating from the platform.

[0091] Example 2

[0092] A neural microelectrode with long-term biocompatibility maintenance. The difference between this embodiment and Embodiment 1 is that the insulating layer material is different and the preparation method is different. Specifically, step S1 in the preparation method is different, while steps S2 and S3 are the same.

[0093] Step S1 in this embodiment is as follows: In this embodiment, PI (polyimide) is used as the insulating layer of the recording electrode, and multiple recording units are formed on the insulating substrate to obtain a flexible neural microelectrode. The specific process is as follows:

[0094] 1-1. Using a single-sided polished silicon wafer as a substrate, the wafer is sequentially immersed in acetone, ethanol, and deionized water for ultrasonic cleaning for 5 minutes each. After drying with nitrogen, it is baked in a 180°C oven for 15 minutes. Figure 5 As shown in part (1), a metal layer is deposited on the polished surface of the silicon wafer as a sacrificial layer. The sacrificial layer metal is Cr and the thickness is 100 nm.

[0095] 1-2. For example Figure 5 As shown in section (2), a layer of PI is spin-coated on the sacrificial layer as the lower insulating layer of the microelectrode, and the thickness of the lower insulating layer is 4 μm.

[0096] 1-3. For example Figure 5 As shown in section (3), a metal layer is deposited on the lower insulating layer as a conductive layer for the recording electrode. The conductive layer metal is Cr / Au and the thickness is 20 / 200nm.

[0097] 1-4. For example Figure 5 As shown in section (4), positive photoresist AZ5214 is coated on the conductive metal layer and the photoresist is patterned using planar photolithography. The photoresist thickness is 2μm.

[0098] 1-5. For example Figure 5 As shown in section (5), the Au layer and Cr layer in the conductive layer are patterned sequentially using wet etching to form signal interconnects.

[0099] 1-6. For example Figure 5 As shown in section (6), a layer of PI is spin-coated on the front side of the patterned metal layer as the upper insulating layer of the flexible neural microelectrode, and the thickness of the upper insulating layer is 4 μm.

[0100] 1-7. For example Figure 5 As shown in section (7), a 100 nm thick Cr layer is deposited on the upper insulating layer as a hard mask for subsequent reactive ion etching (RIE).

[0101] 1-8. For example Figure 5 As shown in section (8), positive photoresist AZ5214 is coated on a hard mask and patterned using planar photolithography. The photoresist thickness is 2μm.

[0102] 1-9. For example Figure 5 As shown in section (9), the hard mask is patterned using wet etching.

[0103] 1-10. For example Figure 5 As shown in (10), the insulating layer is patterned using RIE. Subsequently, the hard mask is removed using wet etching.

[0104] 1-11. For example Figure 5 As shown in (11), the outlines of each electrode were cut out using a laser cutter. The microelectrodes were continuously immersed in chromium etching solution for 30 seconds, rinsed with deionized water, and then released into ethanol using tweezers.

[0105] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for fabricating a neural microelectrode with long-term biocompatibility maintenance, characterized in that: The fabricated neural microelectrode is based on a recording layer (1) and consists of an electrode substrate (5) and one or more probes (6). The probes (6) are coated with a biocompatible coating (3). The recording layer (1) includes a conductive layer and an insulating layer (4). The conductive layer is located inside the insulating layer (4). The conductive layer includes a recording electrode point (1-1) at the tip of the probe (6), a signal line (1-4), and a recording electrode pad (1-2) on the electrode substrate (5). Different recording electrode points (1-1) are connected to their respective recording electrode pads (1-2) via independent signal lines (1-4). The recording electrode points (1-1) and recording electrode pads (1-2) are exposed through windows on the insulating layer; all recording electrode points (1-1) are provided with an electrochemical modification layer (2) to reduce electrode impedance; the electrochemical modification layer (2) is disposed inside the window on the insulating layer and is located inside the biocompatible coating (3); The preparation method includes the following steps: Step 1: Prepare the recording layer using Parylene-C or polyimide as the insulating layer; Step 2: Use ACF conductive adhesive to achieve thermo-press bonding of the recording electrode pads and the flexible flat cable, and use an electrochemical workstation to electroplate the electrode surface to form an electrochemical modification layer (2). Step 3: Deposit peptides on the probe surface of the electrode using PVD coating to form a biocompatible coating (3). The specific process of step three is as follows: Step 3-1. Place the peptide and the electrode obtained in step 2 into a PVD coating machine; Step 3-2. Reduce the air pressure inside the PVD coating machine to a predetermined value; Step 3-3. Heating and evaporating the peptide eliminates the barrier between the peptide and the electrode, allowing the peptide to form a coating on the probe surface of the electrode. Steps 3-4: Release the electrodes; The polypeptide consists of two molecules of phenylalanine.

2. The preparation method according to claim 1, characterized in that: The electrochemical modification layer (2) includes a stacked nano metal layer (2-1) and a conductive polymer layer (2-2); the nano metal layer (2-1) is attached to the recording electrode point (1-1); the conductive polymer layer (2-2) is located on the side of the nano metal layer (2-1) away from the recording electrode point (1-1).

3. The preparation method according to claim 2, characterized in that: The thickness of the nano-metal layer (2-1) is 0.5μm-5μm and the material is Pt-Black; the thickness of the conductive polymer layer (2-2) is 0.5μm-5μm and the material is PEDOT:PSS.

4. The preparation method according to claim 1, characterized in that: The biocompatible coating (3) has a thickness of 0.5μm-5μm and is made of polypeptide.

5. The preparation method according to claim 1, characterized in that: The insulating layer (4) is divided into an upper insulating layer and a lower insulating layer; the conductive layer is disposed between the upper insulating layer and the lower insulating layer.

6. The preparation method according to claim 1, characterized in that: The specific process of step one is as follows: Step 1-1. Deposit a layer of Parylene-C on the substrate as a lower insulating layer using a high-vacuum thermal evaporation coating machine; Step 1-2. Deposit a metal as a conductive layer on the lower insulating layer. The metal of the conductive layer is Cr / Au. Steps 1-3. Coat the conductive layer with positive photoresist and pattern the photoresist using planar photolithography. Steps 1-4. Use wet etching to pattern the Au layer and Cr layer in the conductive layer to form multiple independent sets of recording electrode points, signal lines and recording electrode pads; Steps 1-5. A layer of Parylene-C is deposited on the patterned conductive layer using a high-vacuum thermal evaporation coating machine as the upper insulating layer for the flexible neural microelectrode; Steps 1-6. Deposit a Cr layer on the upper insulating layer as a hard mask for reactive ion etching; Steps 1-7. Coat positive photoresist on the hard mask and pattern the photoresist using planar photolithography; Steps 1-8. Pattern the hard mask using wet etching; Steps 1-9. Pattern the insulating layer using reactive ion etching; remove the hard mask using wet etching to create windows that expose the electrode points and electrode pads; Steps 1-10. Laser cut out the contours of each electrode.

7. The preparation method according to claim 1, characterized in that: The specific process of step one is as follows: Step 1-1. Deposit a metal layer as a sacrificial layer on the polished surface of the silicon wafer substrate; Step 1-2. Spin-coat a layer of polyimide onto the sacrificial layer as the lower insulating layer of the microelectrode; Steps 1-3. Deposit a metal layer as a conductive layer on the lower insulating layer. The conductive layer metal is Cr / Au. Steps 1-4. Coat the conductive layer with positive photoresist and pattern the photoresist using planar photolithography. Steps 1-5. Pattern the Au and Cr layers within the conductive layer sequentially using wet etching; Steps 1-6. Spin-coat a layer of polyimide onto the front side of the patterned metal layer as an upper insulating layer; Steps 1-7. Deposit a layer of Cr on the upper insulating layer as a hard mask for reactive ion etching; Steps 1-8. Coat positive photoresist on the hard mask and pattern the photoresist using planar photolithography; Steps 1-9. Pattern the hard mask using wet etching; Steps 1-10. Pattern the insulating layer using reactive ion etching; remove the hard mask using wet etching to create windows that expose the electrode points and electrode pads. Step 1-11. Laser cut out the outline of each electrode.

8. The preparation method according to claim 1, characterized in that: The specific process of step two is as follows: Step 2-1. Apply a layer of ACF conductive adhesive to the surface of the recording electrode pads and pre-press it; Step 2-2. Attach the flexible flat cable to the ACF conductive adhesive and apply pressure. Steps 2-3. Immerse the recording electrode points of the probe in chloroplatinic acid solution, connect the flexible flat cable using an electrochemical workstation, and electroplate the recording electrode points to form a nano-metal layer; Steps 2-4. Deposit a conductive polymer layer on the surface of the nanometal layer at the recording electrode point.

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