Cranial nerve electrode material and preparation method thereof

Abstract

The invention discloses a preparation method of a cranial nerve electrode material, and belongs to the technical field of cranial nerve electrodes. The preparation method provided by the invention comprises the following steps: providing a first high polymer material substrate; sequentially depositing a titanium film layer and a first gold film layer on the surface of one side or two sides of the first high polymer material substrate; a plurality of conductive circuits are machined through laser engraving; electroplating and preparing a second gold film layer on the surface of the first gold film layer of the conductive circuit; and depositing an insulating layer on the surfaces of the first high polymer material substrate and the conductive circuit, then wrapping a second high polymer material protective layer, curing, and then carving a plurality of through micropores in the surface of the formed material. According to the method provided by the invention, the internal stress of the material can be reduced, the surface smoothness can be improved, brain tissue damage can be reduced, meanwhile, the processing cost is relatively low, the material impedance is relatively low, the consistency is good, the image artifact image under magnetic resonance is small, and the service life is relatively long.

Description

Technical Field

[0001] The present invention relates to the technical field of brain nerve electrodes, and in particular to a brain nerve electrode material and a preparation method thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The core of brain-computer interface (BCI) and deep brain stimulation (DBS) technologies relies on high-quality signal acquisition and precise stimulation from implantable neural electrodes. With the advancement of BCI technology towards higher resolution and less invasiveness, and the increasing demand for intelligent and minimally invasive DBS technology, the market is placing higher demands on neural electrodes that combine high biocompatibility, excellent conductivity, and a flexible structure. Traditional electrodes generally use a micro-spring wire structure, consisting of multiple strands of metal wire wound and coated with an insulating material. This structural characteristic leads to significant drawbacks: as the number of spring wire strands increases, the movement of the electrode within the brain can easily cause wear or even failure of the insulation layer, resulting in signal distortion or functional interruption. Due to limitations in materials and processes, current products only have a maximum of eight stimulation channels (with four being the mainstream), and the seams at the channel edges can easily scratch brain tissue during implantation, compromising safety. Furthermore, the lifespan of traditional electrodes is typically set at five years, which fails to meet the long-term stability and personalized features (such as targeted stimulation and multi-channel control) required for neurological disease treatment.

[0004] In recent years, the maturation of semiconductor MEMS (Micro-Electro-Mechanical Systems) technology has driven the exploration of nanomembrane materials for use in neural electrodes. Nanomembrane materials, with their advantages of high signal transmission quality and consistent processing, offer a new direction for improving electrode performance. However, existing technologies have yet to overcome the structural bottlenecks of traditional electrodes. For example, photolithography-based processing methods are difficult to adapt to the production requirements of long DBS electrodes (e.g., approximately 40 cm), and they struggle to address stress concentration during dynamic electrode bending. These issues expose existing nanomembrane electrodes to the risk of internal stress-induced material fatigue during long-term implantation, while also hindering flexible expansion of channel count and directional stimulation capabilities. Developing brain neural electrodes that combine high channel density, long lifespan, minimal implant damage, and support for directional stimulation through material innovation, structural optimization, and process innovation has become a key challenge in advancing BCI and DBS technology. Summary of the Invention

[0005] In view of this, the present invention provides a brain nerve electrode material and a preparation method thereof. The brain nerve electrode material provided by the present invention can realize more signal channel designs, and the surface smoothness is significantly improved, which can reduce damage to brain tissue during surgical implantation; at the same time, the internal stress is small, which can effectively extend the service life.

[0006] In a first aspect, the present invention provides a method for preparing a cranial nerve electrode material, comprising the following steps: Providing a first polymer material substrate; Depositing a titanium film layer and a first gold film layer in sequence on one side or both sides of the surface of the first polymer material substrate; Use laser engraving to process multiple conductive circuits; Electroplating a second gold film layer on the surface of the first gold film layer of the conductive circuit; An insulating layer is deposited on the surface of the first polymer material substrate and the conductive circuit, and then wrapped with a second polymer material protective layer, solidified, and then a plurality of penetrating micropores are carved on the surface of the formed material to obtain the brain nerve electrode material.

[0007] Preferably, the first polymer material substrate is selected from one or both of polyimide and polyetherimide; and the thickness of the first polymer material substrate is 10-100 μm.

[0008] Preferably, the thickness of the titanium film layer is 1-10 μm, and the thickness of the first gold film layer is 1-10 μm.

[0009] Preferably, in the steps of depositing the titanium film layer and the first gold film layer and depositing the insulating layer, chemical vapor deposition or physical vapor deposition is used for deposition.

[0010] Preferably, the total thickness of the first gold film layer and the second gold film layer is 20-50 μm; the thickness of the insulating layer is 100 nm-5 μm, and the breakdown voltage of the insulating layer is above 100 V / μm.

[0011] Preferably, the length and width of the micropores are 10-500 μm; the micropores are embedded in the gaps of the conductive circuits and are arranged in a periodic or gradient distribution.

[0012] Preferably, the width of the conductive circuit is 10-300 μm, and the spacing is above 10 μm.

[0013] Preferably, after the second gold film layer is prepared by electroplating on the surface of the first gold film layer of the conductive circuit, the method further includes electroplating a platinum layer on the surface of the second gold film layer, wherein the thickness of the platinum layer is 50 nm to 50 μm.

[0014] Preferably, the material of the second polymer material protective layer is polyimide (PI), polyetherimide (PEI) or polyethylene terephthalate (PET); the thickness of the second polymer material protective layer is 5~30uμm; and the curing temperature does not exceed 200°C.

[0015] In a second aspect, the present invention provides a brain nerve electrode material prepared by the above preparation method.

[0016] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The present invention breaks through the 4-8 channel limitation of traditional electrodes through the collaborative design of multi-layer nanofilms and microporous stress release structure, supports the preparation of multi-channel and directional electrodes, reduces internal stress, significantly extends service life, and improves surface smoothness, reduces brain tissue damage, and reduces MRI artifacts, thereby improving image quality.

[0017] (2) The present invention uses laser engraving technology to replace the traditional photolithography process, eliminating the mask and development steps, shortening the processing cycle, supporting non-planar processing of flexible substrates, adapting to the manufacturing of large-size electrodes for BCI and DBS, reducing equipment costs and improving processing accuracy and consistency.

[0018] (3) The present invention utilizes deposition and electroplating processes to selectively thicken the gold film layer, which can not only improve the current carrying capacity and reduce the stress within the film material, ensure low impedance and good consistency, optimize signal transmission quality and stimulation accuracy, but also improve production efficiency.

[0019] (4) The brain nerve electrode material prepared by the present invention supports bidirectional signal transmission (synchronous acquisition and stimulation), can be integrated with biochips and wireless power supply systems, and expand its application in intelligent medical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0021] In order to show the positions of various parts, the distances or sizes between them are exaggerated in the figure, and the schematic diagram is for reference only.

[0022] Figure 1 Schematic diagram of the structure of the cranial nerve electrode material according to Example 1 of the present invention; Figure 2 Schematic diagram of the planar structure of a single electrode according to embodiment 1 of the present invention; In the figure, 1. first polymer material substrate; 2. titanium film layer; 3. first gold film layer; 4. second gold film layer; 5. insulating layer; 6. second polymer layer; 7. conductive circuit; 8. micropore. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0024] As pointed out in the background technology, traditional brain nerve electrodes (such as electrodes based on microspring wire structures) have the following limitations: limited number of channels: limited by the number of metal wire strands, they usually only support 4-8 stimulation channels, which cannot meet the needs of multi-target precision treatment; risk of insulation failure: after long-term implantation, the insulation layer is easily broken due to mechanical wear, resulting in signal distortion or short circuit; large surface roughness: the metal wire structure is easy to scratch brain tissue during implantation, and MRI artifacts are obvious, affecting the postoperative image quality; complex process: traditional photolithography process relies on mask and development steps, and the processing of long electrodes (such as DBS electrodes over 40 cm) is costly and inefficient.

[0025] In view of this, the present invention provides a method for preparing a cranial nerve electrode material, comprising the following steps: Providing a first polymer material substrate; Depositing a titanium film layer and a first gold film layer in sequence on one side or both sides of the surface of the first polymer material substrate; Use laser engraving to process multiple conductive circuits; Electroplating a second gold film layer on the surface of the first gold film layer of the conductive circuit; An insulating layer is deposited on the surface of the first polymer material substrate and the conductive circuit, and then wrapped with a second polymer material protective layer, solidified, and then a plurality of penetrating micropores are carved on the surface of the formed material to obtain the brain nerve electrode material.

[0026] In this invention, the titanium film layer serves as an adhesion layer, enhancing the bonding strength between the substrate and the gold film layer. The gold film layer, serving as the primary conductive layer, exhibits high conductivity and biocompatibility, while minimizing MRI artifacts (gold and platinum are metals with low magnetic susceptibility). The first gold film layer is deposited to achieve a dense gold film, facilitating the subsequent electroplating step. The electroplating process for the second gold film layer not only achieves a shorter processing cycle at a given film thickness, but also effectively reduces internal stress in the film material.

[0027] The present invention uses laser engraving to replace the traditional photolithography process, that is, a high-precision ultraviolet / fiber laser is used to directly engrave the circuit (removing the metal layer outside the conductive circuit), eliminating the mask and development steps, improving processing efficiency, and being able to process large-scale electrode materials. The number of channels can be expanded to more than 12 channels. The present invention ensures stable insulation performance during dynamic bending through the design of the insulating layer material, and obtains a smooth electrode material surface through multi-layer structure design and preparation process, which can reduce damage to brain tissue during surgical implantation. In addition, the micropores of the present invention can effectively induce stress to be evenly dispersed along the edge of the hole when the brain nerve electrode material is curled, which can reduce the internal stress effect by more than 50% compared with traditional solid film materials.

[0028] In the present invention, the first polymer substrate is selected from one or both of polyimide and polyetherimide; the thickness of the first polymer substrate is 10-100 μm. Polyimide (PI) or polyetherimide (PEI) has excellent biocompatibility, high temperature resistance (withstanding processing temperatures near 200°C), chemical stability, and mechanical strength, making it suitable for long-term brain implantation scenarios.

[0029] In the present invention, the thickness of the titanium film layer is 1-10 μm, and the thickness of the first gold film layer is 1-10 μm. The titanium film layer is kept ultra-thin to reduce the stiffness difference.

[0030] In the present invention, the steps of depositing the titanium film layer and the first gold film layer and depositing the insulating layer are performed by chemical vapor deposition or physical vapor deposition. The present invention does not impose any particular limitation on the specific chemical vapor deposition or physical vapor deposition method, and any deposition method commonly used in the art can be used.

[0031] In the present invention, the total thickness of the first gold film layer and the second gold film layer is 20-50 μm; the thickness of the insulating layer is 100 nm-5 μm, and the breakdown voltage of the insulating layer is above 100 V / μm, ensuring no damage during dynamic bending.

[0032] In the present invention, the micropores have dimensions of 10 to 500 μm in length and width; they are embedded in the gaps between the conductive circuits and are arranged in a periodic or gradient distribution. The micropores of the present invention are through-holes that can be adjusted to shapes such as circular, diamond, or rounded rectangles depending on the application scenario. The arrangement of the micropores disperses curling stress, improving electrode flexibility and long-term implant stability. The present invention does not impose any particular restrictions on the micropore engraving method; conventional cutting equipment can be used for micropore engraving.

[0033] In this invention, the conductive traces have a width of 10 to 300 μm, with a pitch of at least 10 μm. Laser engraving accuracy is controlled within ±2 μm. This design ensures insulation between traces and minimum trace impedance. The number of trace channels can be flexibly adjusted based on the actual scenario.

[0034] The present invention, after electroplating a second gold film layer on the surface of the first gold film layer of the conductive circuit, further includes electroplating a platinum layer on the surface of the second gold film layer. The platinum layer has a thickness of 50 nm to 50 μm. The platinum layer has good biochemical safety and is less susceptible to artifacts under MRI, thus providing better postoperative brain MRI imaging for the electrode.

[0035] The conductive circuits prepared in the present invention are easy to control the consistency of layer thickness, and the impedance between circuit channels can be controlled at a level of <30Ω / 40cm, which is much lower than the impedance value of mainstream DBS electrodes on the market (typical index is <100Ω / 40cm).

[0036] In the present invention, the second polymer protective layer is made of polyimide (PI), polyetherimide (PEI), or polyethylene terephthalate (PET); the thickness of the second polymer protective layer is 5 to 30 μm; and the curing temperature does not exceed 200°C. The present invention imposes no particular restrictions on the insulating layer material; for example, parylene can be used. The second polymer protective layer and the insulating layer together form a sealed structure to prevent brain tissue fluid from penetrating and causing a short circuit.

[0037] The present invention also provides a cranial nerve electrode material prepared using the aforementioned preparation method. The cranial nerve electrode material of the present invention has a multi-layer nanofilm synergistic structure, with a gradient combination of titanium film layers, gold film layers, and insulating layers. This material balances conductivity, signal fidelity, and dynamic bending insulation. The conductive circuits and micropores are spatially staggered to avoid material fatigue fracture caused by stress concentration.

[0038] The structural design of the brain nerve electrode material of the present invention can realize more signal channels, breaking through the limitation of 4 to 8 channels of traditional electrodes, and can also support the preparation of directional electrodes. Various required stimulation point shapes can be engraved on the ring surface formed by the curling of the brain nerve electrode material to achieve the effect of directional stimulation therapy, thereby meeting the needs of directional stimulation therapy.

[0039] In addition, the double-sided conductive layer design of the present invention supports bidirectional signal transmission (acquisition + stimulation), and the single-sided structure can be optimized into an ultra-thin implantable electrode, providing more possibilities for EEG applications; and the brain nerve electrode material of the present invention can support the connection of micro-biochips, expanding them into on-chip systems with on-chip sensing functions.

[0040] The technical solution of the present invention is further described below with reference to specific embodiments.

[0041] Example 1 This embodiment provides a method for preparing a cranial nerve electrode material. The schematic diagram of the cranial nerve electrode material structure of this embodiment is shown in FIG. Figure 1As shown, the schematic diagram of the single electrode plane structure is as follows Figure 2 shown.

[0042] (1) Polyimide (PI) was selected as the first polymer substrate 1, with a thickness of 25 μm and a size of 60 cm × 60 cm; the surface was plasma cleaned to enhance adhesion.

[0043] (2) Vacuum evaporation (CVD) is used to deposit the following on both sides of the substrate: titanium film layer 2: thickness of 5 μm on both sides, deposition temperature 150°C; first gold film layer 3: thickness of 8 μm on both sides, deposition temperature 180°C.

[0044] (3) Use a UV laser engraving machine (wavelength 355nm, power 10W) to process the conductive circuit 7: Line width: 100μm, spacing 20μm, 6 channels on each side; engraving accuracy: ±1.5μm, edge smoothness Ra≤0.2μm.

[0045] (4) Electroplating gold is performed on the surface of the first gold film layer 3 of the conductive circuit 7 to thicken the surface and obtain the second gold film layer 4: Plating solution: potassium cyanide gold system, current density 1.5A / dm 2 ; The thickness of the gold plating on each side is increased to 30μm (the thickness of the first gold film layer and the second gold film layer is 30μm in total).

[0046] (5) Deposition of insulating layer 5 and wrapping second polymer layer 6: Insulation layer 5: Parylene deposited by vacuum vapor deposition (PVD), with a thickness of 2 μm and a breakdown voltage ≥ 100 V / μm; The second polymer layer 6 is wrapped with medical-grade polyetherimide (PEI), with a thickness of 5 μm and a curing temperature of 180° C. (curing time of 30 minutes).

[0047] (6) Engraving microporous stress relief structure: Use cutting equipment to carve through-rounded rectangular micro-holes on the surface of the material 8: The hole length and width dimensions are: 200μm×100μm, arranged periodically (spacing 300μm), and the fillet radius is 40μm.

[0048] According to measurements, the impedance between the conductive lines 7 (channels) in this embodiment is less than 30Ω / 40cm.

[0049] Example 2 This embodiment provides a method for preparing a cranial nerve electrode material.

[0050] (1) Polyetherimide (PEI) was selected as the first polymer substrate with a thickness of 25 μm and a size of 60 cm × 60 cm; the surface was plasma cleaned to enhance adhesion.

[0051] (2) Magnetron sputtering (PVD) was used to deposit the following on one side of the substrate: a titanium (Ti) film layer with a thickness of 3 μm, a deposition temperature of 150 °C, and an argon atmosphere; and a first gold (Au) film layer with a thickness of 10 μm, a deposition temperature of 180 °C, and an argon atmosphere.

[0052] (3) Use a UV laser engraving machine (wavelength 355nm, power 10W) to process the conductive circuits on both sides: Line width: 100μm, spacing 20μm, 6 channels on one side; engraving accuracy: ±1.5μm, edge smoothness Ra≤0.2μm.

[0053] (4) Electroplating gold is performed on the surface of the first gold film layer of the conductive circuit to thicken the second gold film layer: Plating solution: potassium cyanide gold system, current density 1.5A / dm 2 ; Plating thickness: The gold layer thickness increases to 30μm.

[0054] (5) Platinum is electroplated on the surface of the second gold film layer to obtain a platinum layer: Plating solution: chloroplatinic acid system, current density 0.8A / dm 2 ;Coating thickness: 10μm.

[0055] (6) Deposition of insulating layer and wrapping of second polymer layer: Insulation layer: Parylene is deposited by vacuum vapor deposition (PVD), with a thickness of 1.2μm and a breakdown voltage of ≥120V / μm; The second polymer layer: wrapped with medical-grade polyetherimide (PEI), with a thickness of 15 μm and a curing temperature of 180°C (30 minutes).

[0056] (6) Engraving microporous stress relief structure: Use cutting equipment to carve through-holes with rounded rectangular shapes on the surface of the material: The hole dimensions are 200 μm × 100 μm in length and width, arranged periodically (spacing 300 μm), and the fillet radius is 40 μm.

[0057] According to measurements, the impedance between the conductive lines (channels) in this embodiment is less than 30Ω / 40cm.

[0058] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a cranial nerve electrode material, characterized in that: The steps include: Providing a first polymer material substrate; Depositing a titanium film layer and a first gold film layer in sequence on one side or both sides of the surface of the first polymer material substrate; Use laser engraving to process multiple conductive circuits; Electroplating a second gold film layer on the surface of the first gold film layer of the conductive circuit; An insulating layer is deposited on the surface of the first polymer material substrate and the conductive circuit, and then wrapped with a second polymer material protective layer, solidified, and then a plurality of penetrating micropores are carved on the surface of the formed material to obtain the brain nerve electrode material.

2. The preparation method according to claim 1, wherein The first polymer material substrate is selected from one or both of polyimide and polyetherimide; the thickness of the first polymer material substrate is 10-100 μm.

3. The preparation method according to claim 1, wherein The thickness of the titanium film layer is 1-10 μm, and the thickness of the first gold film layer is 1-10 μm.

4. The preparation method according to claim 1, wherein In the steps of depositing the titanium film layer and the first gold film layer and depositing the insulating layer, chemical vapor deposition or physical vapor deposition is used for deposition.

5. The preparation method according to claim 1, wherein The total thickness of the first gold film layer and the second gold film layer is 20-50 μm; the thickness of the insulating layer is 100 nm-5 μm, and the breakdown voltage of the insulating layer is above 100 V / μm.

6. The preparation method according to claim 1, wherein The length and width of the micropores are 10-500 μm; the micropores are embedded in the gaps of the conductive circuits and are arranged in a periodic or gradient distribution.

7. The preparation method according to claim 1, wherein The width of the conductive circuit is 10-300 μm, and the spacing is above 10 μm.

8. The preparation method according to claim 1, wherein After the second gold film layer is electroplated on the surface of the first gold film layer of the conductive circuit, the method further includes the step of electroplating a platinum layer on the surface of the second gold film layer, wherein the thickness of the platinum layer is 20 nm to 50 μm.

9. The preparation method according to claim 1, wherein The material of the second polymer material protective layer is polyimide, polyetherimide or polyethylene terephthalate; the thickness of the second polymer material protective layer is 5-30 μm; and the curing temperature does not exceed 200°C.

10. The cranial nerve electrode material prepared by the preparation method according to any one of claims 1 to 9.

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