Flexible neural microelectrode based on carbon nanomaterial
By fabricating an insulating film layer with embedded conductive and wiring contacts on a silicon substrate and then removing the silicon substrate using hydrofluoric acid etching, the problems of conductive layer damage and poor contact during the fabrication of flexible neural microelectrodes were solved, thus achieving stability in conductivity and signal transmission.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING INSTITUTE OF GRAPHIC COMMUNICATION
- Filing Date
- 2026-01-04
- Publication Date
- 2026-05-01
AI Technical Summary
In the fabrication process of existing flexible neural microelectrodes, high-energy ion etching can damage the conductive layer by creating openings, and the conductive contacts are not fully exposed after etching, which affects the contact effect with nerve tissue.
A first insulating film layer with embedded conductive contacts and wiring contacts is prepared on a silicon substrate to form graphene conductive lines. After removing the silicon substrate, the conductive contacts and wiring contacts are fully exposed to avoid high-energy ion etching. The silicon substrate is then removed by hydrofluoric acid corrosion and dissolution.
This achieves the integrity and conductivity of graphene conductive lines, avoids damage to the conductive layer caused by high-energy ion etching, and ensures that conductive contacts are fully exposed, thereby improving the electrical signal transmission effect of nerve tissue.
Smart Images
Figure CN121944374A_ABST
Abstract
Description
A flexible neural microelectrode based on carbon nanomaterials Technical Field
[0001] This invention belongs to the field of neural microelectrode technology and relates to a flexible neural microelectrode based on carbon nanomaterials. Background Technology
[0002] As a crucial interface between neural tissue and functional devices, neural microelectrodes play a vital role in the treatment of neurological diseases such as paraplegia, Parkinson's disease, optic nerve injury, and auditory nerve injury. Flexible neural microelectrodes, a type of neural microelectrode, are characterized by their use of flexible materials (such as polyimide, liquid metal, and graphene) to match the mechanical properties of biological neural tissue, thereby reducing implantation damage and improving signal transmission and acquisition stability.
[0003] Existing flexible neural microelectrodes typically consist of three layers: two flexible insulating film layers on the top and bottom, and a conductive layer in the middle. To enable the conductive layer to contact and conduct with nerve tissue, contact vias need to be created in one of the flexible insulating film layers. However, creating these contact vias generally employs high-energy plasma etching or similar methods. This process can damage the conductive contacts made of graphene or other carbon nanomaterials at the corresponding locations on the conductive layer, affecting their conductivity. To address this issue, some studies have reported pre-embedding support pillars at the locations of the vias formed in the flexible insulating film layer, and then chemically dissolving and removing the support pillars to form the contact vias. While this method mitigates the damage to the conductive contacts made of graphene and other carbon nanomaterials caused by etching to some extent, the entire process, including the formation and dissolution of the support pillars, is relatively complex. Furthermore, after the support pillars are dissolved and removed, the conductive contacts remain within a certain depth of the contact via, not fully exposed to the surface of the flexible insulating film layer, thus affecting their adequate contact with nerve tissue. Summary of the Invention
[0004] This invention provides a flexible neural microelectrode based on carbon nanomaterials, aiming to overcome the above-mentioned shortcomings of the prior art.
[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a flexible neural microelectrode based on carbon nanomaterials, comprising the following steps:
[0006] S1. A first insulating film layer with a plurality of conductive contacts and wiring contacts embedded on the surface of a silicon substrate is prepared to obtain an initial structure. The conductive contacts and wiring contacts are one-to-one and are respectively disposed at both ends of the silicon substrate. The lower ends of the conductive contacts and wiring contacts are fixed on the silicon substrate, and the upper ends are exposed on the upper surface of the first insulating film layer.
[0007] S2. A conductive layer is prepared on the upper surface of the initial structural component to obtain an intermediate structural component. The conductive layer includes a plurality of graphene conductive lines that correspond one-to-one with the conductive contacts. One end of each graphene conductive line is electrically connected to the conductive contact, and the other end is electrically connected to the corresponding wiring contact.
[0008] S3. A second insulating film layer is prepared on the upper surface of the intermediate structural component to obtain a structural component to be post-processed, wherein the second insulating film covers the first insulating film layer and the conductive layer;
[0009] S4. Remove the silicon substrate of the structure to be post-processed to fully expose the lower ends of each of the conductive contacts and wiring contacts, thereby obtaining the flexible neural microelectrode.
[0010] Specifically, the preparation steps of the initial structure described in S1 are as follows: a metal conductive layer is formed on the surface of a silicon substrate, then photoresist is spin-coated and patterned. Under the protection of the patterned photoresist, the metal conductive layer except for each conductive contact and wiring contact is dissolved. After cleaning and drying, a first insulating film layer is formed on the surface of the substrate. The first insulating film at the corresponding position on the upper end of each conductive contact and wiring contact is etched to expose the upper end of each conductive contact and wiring contact, thus obtaining the structure.
[0011] Specifically, before forming a metal conductive layer on the surface of the silicon substrate, the areas corresponding to each conductive contact on the silicon substrate are etched to form grooves.
[0012] Specifically, the metal conductive layer is made of gold or platinum and has a thickness of 2.5-3.5 μm.
[0013] Specifically, before the metal conductive layer is formed on the surface of the silicon substrate by sputtering gold or platinum, a metal bonding layer is first formed by sputtering titanium.
[0014] Specifically, in S2, when preparing the conductive layer, a graphene layer covering the conductive contacts and wiring contacts is first formed on the upper surface of the initial structure. Then, photoresist is spin-coated onto the graphene layer and patterned. Subsequently, the excess graphene layer is removed to form graphene conductive lines.
[0015] Specifically, the method for forming a graphene layer on the upper surface of the initial structural component includes either a direct growth method or an indirect transfer method.
[0016] Preferably, in S4, hydrofluoric acid is used to etch and dissolve the silicon substrate to fully expose the lower ends of each conductive contact and wiring contact.
[0017] Preferably, the first insulating film layer and the second insulating film layer are PI film, parylene film or PDMS film.
[0018] This invention provides a flexible neural microelectrode based on carbon nanomaterials, which is prepared by the above method.
[0019] Compared with the prior art, the beneficial effects of the present invention are:
[0020] The flexible neural microelectrode based on carbon nanomaterials provided by this invention features graphene conductive wires that are electrically connected to conductive and wiring contacts during fabrication. These contacts are embedded within the first insulating film layer during its formation. Therefore, after the substrate is etched away, the graphene conductive wires within the two insulating film layers can transmit signals to the outside world through these contacts, thus enabling electrical signal transmission between the neural tissue and the external environment. This eliminates the need for additional high-energy ion etching of the first or second insulating film layer to expose the graphene conductive wires during fabrication. This method overcomes both the problem of damaging the graphene conductive wires during high-energy ion etching and the issue of poor contact between the conductive contacts and neural tissue after etching, where the contacts remain embedded within the pores. Attached Figure Description
[0021] Figure 1 is a cross-sectional schematic diagram of the overall structure of the flexible neural microelectrode based on carbon nanomaterials provided by the present invention when it is fabricated on a silicon substrate and the substrate has not yet been removed.
[0022] Figure 2 is a top view of the silicon substrate after the conductive contacts and wiring contacts of the flexible neural microelectrode shown in Figure 1 have just been formed during the fabrication process (the first insulating film layer has not yet been formed).
[0023] Figure 3 is a schematic diagram of the neural microelectrode corresponding to the overall structure shown in Figure 1 after the silicon substrate is removed;
[0024] Figure 4 is a cross-sectional schematic diagram of the overall structure of the flexible neural microelectrode finally obtained when grooves are provided at the positions of the conductive contacts on the silicon substrate, without removing the silicon substrate.
[0025] Figure 5 is a schematic diagram of the neural microelectrode corresponding to the overall structure shown in Figure 4 after the silicon substrate is removed;
[0026] Figure 6 is a cross-sectional schematic diagram of a silicon substrate with grooves in the overall structure shown in Figure 4;
[0027] Figure 7 is a schematic diagram of a multi-channel type of neural microelectrode when both conductive contacts and wiring contacts are set to multiple. The end where the wiring contacts are located can be folded 180 degrees inward along the dotted line and fixed.
[0028] The attached diagram lists the components represented by each number as follows:
[0029] 1. Silicon substrate; 2. First insulating film layer; 3. Conductive contact; 4. Wiring contact; 5. Graphene conductive wire; 6. Second insulating film layer; 7. Groove. Detailed Implementation
[0030] The technical solutions provided by the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] In the description of this invention, if terms such as "upper," "lower," "left," "right," "top," "bottom," "inner," and "outer" are used to indicate the orientation or positional relationship, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0032] As shown in Figures 1 to 7, the present invention provides a method for preparing a flexible neural microelectrode based on carbon nanomaterials, which includes the following steps:
[0033] S1. A first insulating film layer 2 with a plurality of conductive contacts 3 and wiring contacts 4 embedded on the surface of a silicon substrate 1 is prepared to obtain an initial structure. The conductive contacts 3 and wiring contacts 4 are one-to-one and are respectively disposed at both ends of the silicon substrate 1. The lower ends of the conductive contacts 3 and wiring contacts 4 are fixed on the silicon substrate 1, and the upper ends are exposed on the upper surface of the first insulating film layer 2.
[0034] S2. A conductive layer is prepared on the upper surface of the initial structural component to obtain an intermediate structural component. The conductive layer includes a plurality of graphene conductive wires 5 that correspond one-to-one with the conductive contacts. One end of each graphene conductive wire 5 is electrically connected to the conductive contact 3, and the other end is electrically connected to the corresponding wiring contact 4.
[0035] S3. A second insulating film layer 6 is prepared on the upper surface of the intermediate structural component to obtain a structural component to be post-processed. The second insulating film covers the first insulating film layer 1 and the conductive layer.
[0036] S4. Remove the silicon substrate 1 of the structure to be post-processed to fully expose the lower ends of each of the conductive contacts 3 and wiring contacts 4, thereby obtaining the flexible neural microelectrode.
[0037] In one embodiment of the present invention, the preparation steps of the initial structure in S1 are as follows: a metal conductive layer is formed on the surface of a silicon substrate, preferably by sputtering. In a vacuum environment, using platinum or gold as the target, platinum or gold atoms are bombarded by plasma to detach from the target and form a continuous metal conductive layer film on the silicon substrate. The thickness of the metal conductive layer is preferably controlled between 2.5-3.5 μm. Then, photoresist is spin-coated and patterned. Here, patterning refers to forming photoresist protection points at the positions corresponding to each conductive contact and wiring contact, while the remaining parts are unprotected. Therefore, under the protection of the patterned photoresist, the unprotected metal conductive layer is gradually dissolved and removed by brushing with aqua regia. Finally, only the conductive contacts and wiring contacts remain on the substrate. Then, the photoresist on the surface of each conductive contact and wiring contact is removed. After cleaning and drying, a first insulating film layer is formed on the substrate surface using a coating method or a chemical vapor deposition method. During the formation of the first insulating film layer, the upper surface of each conductive contact and wiring contact will inevitably be covered. After the first insulating film layer is formed, the first insulating film at the corresponding position on the upper end of each conductive contact and wiring contact needs to be etched to expose the upper end of each conductive contact and wiring contact. Before etching, the first insulating film outside the etched point can also be protected by spin-coating photoresist, so that only the upper end of each conductive contact and wiring contact is exposed by etching. Then, the photoresist is removed, and the substrate is cleaned and dried to obtain the initial structure.
[0038] In one embodiment of the present invention, in order to ensure that one end of the conductive contact of the fabricated flexible neural microelectrode appropriately protrudes from the insulating film layer (first insulating film layer), the silicon substrate is pretreated before forming the conductive contact and the first insulating film layer. Specifically, a groove 7 is formed by appropriately etching the position on the silicon substrate where the conductive contact is to be formed. This can be done by hydrofluoric acid etching or other methods known to those skilled in the art, which will not be elaborated here. A cross-sectional view of the silicon substrate after pretreatment is shown in Figure 6. It is understood that when an Au film layer or a Pt film layer (conductive metal layer) is sputtered on the silicon substrate with the groove 7, the film layer at the groove will protrude downwards appropriately (i.e., below the upper surface of the silicon substrate). Thus, after the basic structure of the neural microelectrode is formed (the first insulating film layer, the conductive layer, and the second insulating film layer are all formed) and the silicon substrate is etched away, the lower end of the columnar (pancake-shaped) conductive contact of Au or Pt material protrudes from the lower surface of the first insulating film layer, which can more effectively contact and conduct electrical signals with nerve tissue.
[0039] In addition, to enhance the bonding strength between the metal conductive layer and the silicon substrate, and to ensure that the conductive contacts and wiring contacts pre-formed on the silicon substrate do not easily detach or shift during the coating or CVD formation of the first insulating film layer, a titanium bonding layer is first formed by sputtering titanium as the target material before sputtering the Au or Pt metal conductive layer. Then, the metal conductive layer is sputtered onto the titanium bonding layer. After the neural microelectrode is fabricated on the silicon substrate, the silicon substrate is etched away using a corrosive solution such as hydrofluoric acid. During this process, the titanium bonding layer on the lower end face of the conductive contacts and wiring contacts is also etched away, while the Au or Pt conductive contacts and wiring contacts are not etched. This ensures that each conductive contact and wiring contact is fully exposed and exhibits good conductivity.
[0040] In one embodiment of the present invention, during the fabrication of the conductive layer in step S2, a graphene layer covering the conductive contacts and wiring contacts is first formed on the upper surface of the initial structure. Then, photoresist is spin-coated onto the graphene layer and patterned. Subsequently, excess graphene layer is removed to form graphene conductive lines. The method for forming the graphene layer on the upper surface of the initial structure includes either a direct growth method or an indirect transfer method.
[0041] It should be noted that the direct growth method involves directly growing a graphene layer on the surface of the first insulating film layer (including the embedded conductive contacts and interconnections) using methods such as CVD, PECVD, or magnetron sputtering. The graphene layer is then post-processed to remove excess material, leaving only the graphene conductive lines. The indirect transfer method involves first preparing a complete graphene film layer on another substrate, and then transferring the synthesized graphene film layer onto the first insulating film layer using a water transfer technique. The removal of excess material from the graphene film layer can be accomplished using plasma etching techniques (such as oxygen or argon plasma). Graphene conductive wires possess the ability to maintain excellent conductivity even at minute dimensions. To ensure this conductivity, this invention ensures that the wires are electrically connected to each conductive contact and wiring contact during molding and are completely encapsulated between the first and second insulating film layers, thus providing effective protection. It eliminates the need for additional high-energy ion etching, such as plasma etching, to open holes in the first or second insulating film layers to expose the internal graphene conductive wires. Therefore, the graphene conductive wires are not damaged at the conductive or wiring contacts (graphene is significantly damaged upon contact with oxygen plasma, while Au or Pt conductive or wiring contacts are largely unaffected), maintaining good signal transmission capabilities.
[0042] In the above embodiments of the present invention, in S4, hydrofluoric acid is used to etch and dissolve the silicon substrate to fully expose the lower ends of each conductive contact and wiring contact.
[0043] It should be noted that the silicon substrate selected in this invention should be as thin as possible while still being able to achieve the basic load-bearing function, so as to make the etching and dissolution removal more efficient and save solvent.
[0044] In the above embodiments of the present invention, the first insulating film layer and the second insulating film layer are PI film, parylene film or PDMS film.
[0045] It is understood that the above membrane materials are commonly used in the preparation of flexible neural microelectrodes. The present invention preferably uses the above membrane materials, but does not limit the use of other membrane materials with similar physicochemical properties in the present and future.
[0046] The flexible neural microelectrode based on carbon nanomaterials provided by this invention, in addition to the single-channel neural microelectrode structure shown in Figures 1 to 6 (each electrode has only one conductive contact), can also be a multi-channel neural microelectrode structure shown in Figure 7 (each electrode has multiple conductive contacts arranged in an array). To facilitate the connection and fixation of the wiring contacts at one end of the electrode with external signal lines, the end of the flexible neural microelectrode shown in Figure 7, where the wiring contacts are located, can be folded back 180 degrees along the dotted line in the figure and bonded to the second insulating film layer with adhesive (essentially, the folded and bonded second insulating film layers are bonded together). The flexibility of the graphene conductive wires and the two insulating film layers allows this operation without affecting the basic signal transmission performance of the electrode. Thus, each wiring contact is located on the back side of one end of the flexible neural microelectrode for easy wiring, and each conductive contact is located on the front side of the other end of the flexible neural microelectrode for easy contact with nerve tissue.
[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a flexible neural microelectrode based on carbon nanomaterials, characterized in that, The process includes the following steps: S1. Preparing a first insulating film layer embedded with a plurality of conductive contacts and wiring contacts on the surface of a silicon substrate to obtain an initial structure. The conductive contacts and wiring contacts are one-to-one and are respectively disposed at both ends of the silicon substrate. The lower ends of the conductive contacts and wiring contacts are fixed to the silicon substrate, and the upper ends are exposed on the upper surface of the first insulating film layer; S2. Preparing a conductive layer on the upper surface of the initial structure to obtain an intermediate structure. The conductive layer includes a plurality of graphene conductive lines corresponding one-to-one with the conductive contacts. One end of each graphene conductive line is electrically connected to the conductive contact, and the other end is electrically connected to the corresponding wiring contact; S3. Preparing a second insulating film layer on the upper surface of the intermediate structure to obtain a structure to be post-processed. The second insulating film covers the first insulating film layer and the conductive layer; S4. Removing the silicon substrate of the structure to be post-processed to fully expose the lower ends of each conductive contact and wiring contact, thereby obtaining the flexible neural microelectrode.
2. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 1, characterized in that, The preparation steps of the initial structure described in S1 are as follows: a metal conductive layer is formed on the surface of a silicon substrate, then photoresist is spin-coated and patterned. Under the protection of the patterned photoresist, the metal conductive layer except for each conductive contact and wiring contact is dissolved. After cleaning and drying, a first insulating film layer is formed on the surface of the substrate. The first insulating film at the corresponding position on the upper end of each conductive contact and wiring contact is etched to expose the upper end of each conductive contact and wiring contact, thus obtaining the structure.
3. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 2, characterized in that, Before forming a metal conductive layer on the surface of a silicon substrate, the areas of the silicon substrate corresponding to each conductive contact are etched to form grooves.
4. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 2, characterized in that, The conductive metal layer is made of gold or platinum and has a thickness of 2.5-3.5 μm.
5. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 4, characterized in that, Before forming the metal conductive layer on the surface of the silicon substrate by sputtering gold or platinum, a metal bonding layer is first formed by sputtering titanium.
6. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 1, characterized in that, In S2, when preparing the conductive layer, a graphene layer covering the conductive contacts and wiring contacts is first formed on the upper surface of the initial structure. Then, photoresist is spin-coated onto the graphene layer and patterned. Subsequently, the excess graphene layer is removed to form graphene conductive lines.
7. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 6, characterized in that, The method for forming a graphene layer on the upper surface of the initial structural component includes either a direct growth method or an indirect transfer method.
8. The method for preparing a flexible neural microelectrode based on carbon nanomaterials according to claim 1, characterized in that, In S4, hydrofluoric acid is used to etch and dissolve the silicon substrate to fully expose the lower ends of each conductive contact and wiring contact.
9. A method for preparing a flexible neural microelectrode based on carbon nanomaterials according to any one of claims 1 to 8, characterized in that, The first insulating film layer and the second insulating film layer are PI film, parylene film or PDMS film.
10. A flexible neural microelectrode based on carbon nanomaterials, characterized in that, It is prepared by the method according to any one of claims 1 to 9.