Flexible carbon-based fiber neural electrode with partitioned coating regulation and control function and preparation method of flexible carbon-based fiber neural electrode

Abstract

The invention relates to a flexible carbon-based fiber neural electrode with partition coating regulation and control and a preparation method thereof.The flexible carbon-based fiber neural electrode comprises a single flexible carbon-based fiber, the flexible carbon-based fiber comprises a front end, a front section, a rear section and a rear end which are sequentially distributed in the axial direction of the flexible carbon-based fiber, the front end is coated with a water-soluble rigid polymer, and the rear end is coated with a water-soluble rigid polymer; the front section is coated with biocompatible thermosetting rigid resin, the rear section is coated with rigid or flexible insulating resin, and the rear end serves as an electrode connector. The preparation method comprises the following steps: (1) coating the front end of the flexible carbon-based fiber with a water-soluble rigid polymer and carrying out curing treatment; (2) coating the front section of the flexible carbon-based fiber with biocompatible thermosetting rigid resin and carrying out curing treatment; and (3) flexible or rigid insulating resin is used, and the rear section of the flexible carbon-based fiber is coated and cured through a spin coating, dip coating or spray coating technology. The electric signal conduction performance of the neural electrode is effectively improved, and meanwhile the immune response after implantation is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of neuroscience monitoring, and particularly relates to a flexible carbon-based fiber nerve electrode with zoned coating regulation and a preparation method thereof. Background Art

[0002] With the continuous development of brain science research and brain-computer interface technology, the importance of safe, stable, and efficient in-vivo implantable electrodes in neuroscience research and clinical applications has become increasingly prominent. Traditional metal material electrodes, such as metal wires or metal needles, although excellent in the efficiency of electrical signal transmission, are prone to cause tissue inflammatory reactions and electrode performance attenuation after long-term implantation due to their high electrode stiffness and poor biocompatibility. These problems not only affect the integration of the electrode with the nervous system but also reduce the signal quality and stability in clinical use.

[0003] To solve the above problems, flexible materials such as carbon-based fibers have been introduced for the manufacture of electrodes to reduce stiffness and improve biocompatibility. Although carbon-based fibers have excellent properties, their poor stiffness regulation and rough surface in their original form may limit their application in brain tissue. Therefore, there is an urgent need for a new type of flexible biosensing electrode that coats different parts of the carbon-based fiber with materials having specific functions to ensure that the electrode can achieve optimal performance in each part, which is beneficial for the electrode to better adapt to the in-vivo environment after implantation and ensure the accurate transmission of electrical signals; at the same time, it also needs to be easily implantable and able to reduce tissue damage during the implantation process, thereby improving its overall performance. Summary of the Invention

[0004] Based on the above-mentioned disadvantages and deficiencies existing in the prior art, one of the purposes of the present invention is to at least solve one or more of the above problems existing in the prior art. In other words, one of the purposes of the present invention is to provide a flexible carbon-based fiber nerve electrode with zoned coating regulation and a preparation method thereof that meet one or more of the aforementioned requirements. The present invention uses the structural design of flexible carbon-based fibers and a biocompatible matrix, which significantly improves the stability of the electrode-brain tissue interface. At the same time, due to the rigid characteristics of the water-soluble rigid polymer at the front end of the electrode implantation, the electrode is more stable during the implantation process, facilitating operation and reducing the risk of damage to the surrounding brain tissue; after implantation, under the action of physiological saline in the living body, the water-soluble rigid polymer gradually dissolves, enabling the electrode to better adapt to the in-vivo environment and effectively extending the service life of the electrode.

[0005] To achieve the above invention purpose, the present invention adopts the following technical solutions:

[0006] A flexible carbon-based fiber nerve electrode with partition coating regulation, comprising a single flexible carbon-based fiber. The flexible carbon-based fiber includes a front end, a front section, a rear section, and a rear end sequentially distributed along its axial direction. The front end is coated with a water-soluble rigid polymer, the front section is coated with a biocompatible thermosetting rigid resin, the rear section is coated with a rigid or flexible insulating resin, and the rear end serves as an electrode joint.

[0007] As a preferred solution, the water-soluble rigid polymer includes at least one of polyvinyl alcohol and polyethylene glycol.

[0008] As a preferred solution, the cross-section of the water-soluble rigid polymer coated on the front end along the fiber axis is a semi-circular structure.

[0009] As a preferred solution, the biocompatible thermosetting rigid resin includes at least one of epoxy resin, phenolic resin, and polyurethane resin.

[0010] As a preferred solution, the flexible insulating resin includes at least one of silicone rubber and polydimethylsiloxane, and the rigid insulating resin is polyimide.

[0011] As a preferred solution, the flexible carbon-based fiber is a carbon nanotube fiber, a graphene oxide fiber, or a graphene fiber.

[0012] As a preferred solution, the diameter of the flexible carbon-based fiber is 15 - 30 μm.

[0013] The present invention also provides a preparation method of the flexible carbon-based fiber nerve electrode according to any one of the above solutions, comprising the following steps:

[0014] (1) Coat a water-soluble rigid polymer on the front end of the flexible carbon-based fiber, and perform a curing treatment at 60 - 80 °C for 20 - 60 minutes;

[0015] (2) Coat a biocompatible thermosetting rigid resin on the front section of the flexible carbon-based fiber, and perform a curing treatment at 120 - 180 °C for 30 - 120 minutes;

[0016] (3) Use a flexible or rigid insulating resin to coat the rear section of the flexible carbon-based fiber by spin coating, dip coating, or spraying techniques, and perform a curing treatment at 80 - 150 °C for 1 - 3 hours.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] (1) The present invention uses a carbon-based fiber material to make the electrode. Due to its high conductivity and good biocompatibility, it can effectively improve the electrical signal conduction performance of the nerve electrode, while reducing the immune response after implantation, ensuring the stability and functionality of the electrode during long-term use;

[0019] (2) The biocompatible thermosetting rigid resin coated on the front section of the electrode implantation part of the present invention reduces the biological adverse reactions after implantation and can effectively extend the service life of the electrode in the body. At the same time, the water-soluble rigid polymer coated on the front end can dissolve after implantation, providing a more precise electrode contact area and ensuring the efficient conduction and recording of nerve signals. The insulating resin coated on the rear section reduces the movement or detachment of the electrode during implantation and ensures the stability after implantation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic cross-sectional structure diagram of the flexible carbon-based fiber nerve electrode of the present invention;

[0021] Figure 2 is a resistance-time curve graph of the flexible carbon-based fiber nerve electrode and carbon nanotube fiber of Example 1 of the present invention in a physiological saline environment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The flexible carbon-based fiber nerve electrode with partition coating regulation provided by the present invention and its preparation method will be further described below.

[0023] The flexible carbon-based fiber nerve electrode with partition coating regulation of the present invention includes an implantation part and a conduction part. The main body is composed of a continuous carbon-based fiber. The front section of the electrode implantation part is coated with a biocompatible thermosetting rigid resin, and at the same time, the tip of the front section (i.e., the front end) is also coated with a water-soluble rigid polymer. The rear section of the electrode implantation part is coated with a rigid or flexible insulating resin. The conduction part, that is, the rear end of the rear section of the implantation part, is used as an electrode connector to connect with circuit components.

[0024] Specifically, as Figure 1 shown, the flexible carbon-based fiber nerve electrode of the present invention includes a single flexible carbon-based fiber 3. The flexible carbon-based fiber includes a front end, a front section, a rear section, and a rear end distributed in sequence along its axial direction. The front end is coated with a water-soluble rigid polymer 1, the front section is coated with a biocompatible thermosetting rigid resin 2, the rear section is coated with a rigid or flexible insulating resin 4, and the rear end is used as an electrode connector 5. Among them, the electrode connector 5 is connected with circuit components 6 to realize the transmission of electrical signals. The cross-section of the water-soluble rigid polymer coated on the front end along the fiber axis is a semi-circular structure. The carbon-based fiber 3 is the main body part of the entire electrode. The tip of the implantation part (i.e., the front end) can penetrate into the nerve bundle by penetrating the nerve membrane. The thermosetting rigid resin 2 of the implantation part can fit with the epineurium, and the insulating resin 4 of the implantation part connects the part conducting electricity inside and outside the living body. After implantation, the water-soluble rigid polymer can dissolve, and the exposed carbon-based fiber electrode sites contact the nerve bundle in the membrane, so as to effectively collect electrical signals.

[0025] The water-soluble rigid polymer of the present invention includes at least one of polyvinyl alcohol and polyethylene glycol. The water-soluble rigid polymer will dissolve when it encounters physiological saline after implantation. The design of the water-soluble rigid polymer enables the electrode to better integrate with the surrounding tissues after implantation, improving the use effect and biocompatibility of the electrode.

[0026] The biocompatible thermosetting rigid resin of the present invention includes at least one of epoxy resin, phenolic resin, and polyurethane resin. The thermosetting rigid resin has high wear resistance, which can prevent abrasion when the electrode contacts nerve cells, thereby extending the service life of the electrode; due to the good matching of the resin during implantation, it can closely fit the tissue contour, thereby reducing the mechanical stress on nerve tissue and reducing the risk of injury.

[0027] The flexible insulating resin of the present invention includes at least one of silicone rubber and polydimethylsiloxane, and the rigid insulating resin is polyimide. The insulating resin can prevent current leakage and protect the electrode from the external environment during implantation; at the same time, the flexible insulating resin can enhance the flexibility during implantation.

[0028] The flexible carbon-based fiber of the present invention is a carbon nanotube fiber, a graphene oxide fiber, or other commonly used existing carbon-based fibers.

[0029] The diameter of the flexible carbon-based fiber of the present invention is 15 - 30 μm.

[0030] The length of the front end of the flexible carbon-based fiber nerve electrode of the present invention, that is, the length of the exposed part after dissolution, is adjusted according to specific implantation requirements and is in the range of several micrometers to ten micrometers to adapt to brain tissue structures at different depths.

[0031] The present invention also provides a method for preparing the above flexible carbon-based fiber nerve electrode, including the following steps:

[0032] (1) Coat the water-soluble rigid polymer on the front end of the flexible carbon-based fiber and carry out a curing treatment at 60 - 80 °C for 20 - 60 minutes;

[0033] (2) Coat the biocompatible thermosetting rigid resin on the front section of the flexible carbon-based fiber and carry out a curing treatment at 120 - 180 °C for 30 - 120 minutes;

[0034] (3) Use the flexible or rigid insulating resin to coat the rear section of the flexible carbon-based fiber by spin coating, dip coating, or spraying technology, and carry out a curing treatment at 80 - 150 °C for 1 - 3 hours.

[0035] The following further explains the flexible carbon-based fiber nerve electrode with zoned coating regulation and its preparation method of the present invention through specific embodiments.

[0036] Example 1:

[0037] The preparation method of the flexible carbon-based fiber nerve electrode in this example includes the following steps:

[0038] Iron(III) nitrate and benzene are added to ethanol and dissolved to obtain a reaction precursor solution. This solution is injected into a vertical furnace for carbon nanotube growth, and a catalytic reaction is carried out under high temperature conditions of 1200 °C, and a nitrogen protective gas flow is introduced. During the reaction process, iron(III) nitrate decomposes at high temperature and reacts with the carbon source to generate carbon nanotube fibers; the diameter of the carbon nanotube fibers is about 20 μm;

[0039] After the growth of the carbon nanotube fibers is completed, a layer of water-soluble rigid polymer polyvinyl alcohol is coated on the tip of the carbon nanotube fibers, and it is placed in an environment of 60 °C for curing treatment for 20 minutes; after the treatment of the water-soluble rigid polymer coating is completed, a layer of biocompatible epoxy resin is evenly coated on the front section of the electrode, and a second curing treatment is carried out at a temperature of 120 °C for 30 minutes to ensure that the resin is completely cured and attached to the electrode surface, thereby enhancing its mechanical strength; after ensuring the stability of the biocompatible epoxy resin coating, silicone rubber is evenly coated on the rear section of the carbon nanotube fibers through spraying technology; after the coating is completed, a third curing treatment is carried out in an environment of 80 °C for 2 hours to ensure that the insulating layer has good mechanical strength and electrical properties; the preparation of the flexible carbon-based fiber nerve electrode with zoned coating regulation is completed. Connecting the rear end of the carbon nanotube fibers to circuit components can realize signal acquisition.

[0040] As Figure 2 shown, the resistance-time change curve recorded in real time is given. In the initial stage, the flexible carbon-based fiber nerve electrode in this example, that is, the carbon nanotube fibers coated with soluble resin, has a slightly higher resistance compared to the pure carbon nanotube fibers. Subsequently, as the soluble resin gradually dissolves, the resistance slightly decreases and tends to be stable, and finally the resistance change trend is basically the same as that of the pure carbon nanotube fibers; this result shows that the soluble resin provides additional mechanical support in the initial stage of implantation, enhancing the rigidity of the fibers, and does not affect the long-term electrical conductivity of the carbon nanotube fibers after its dissolution, providing experimental support for the implantation and stability of the flexible carbon-based fiber nerve electrodes.

[0041] Example 2:

[0042] The preparation method of the flexible carbon-based fiber nerve electrode in this example includes the following steps:

[0043] The graphene oxide slurry was centrifugally concentrated to 3 wt%, and then injected into a coagulation bath at a speed of 0.042 mL / min. The coagulation bath was composed of ethanol and deionized water mixed at a volume ratio of 1:3 and contained 5 wt% calcium chloride. Wet spinning was carried out to produce a preliminarily formed graphene oxide fiber. After the fiber was formed in the coagulation bath, it was immersed in a curing bath for 30 minutes to enhance its structural stability. Then, it was placed in an oven at 50 °C and dried for 24 hours to remove moisture. The dried graphene oxide fiber was subjected to a thermal reduction treatment at 450 °C for 1 hour under a protective argon atmosphere while applying a tension of 3 MPa, so that the oxygen-containing functional groups in the fiber were removed and the carbon atoms were rearranged to form a reduced graphene structure with better conductivity, and finally graphene fiber was obtained. Among them, the diameter of the graphene fiber was about 30 μm. The graphene fiber has extremely high flexibility and a large surface area, which is beneficial to improving the interfacial contact between the electrode and nerve tissue, thereby enhancing the sensitivity of signal acquisition.

[0044] A layer of water-soluble polyethylene glycol was evenly coated on the tip of the graphene fiber and cured in an environment at 60 °C for 20 minutes. After the treatment with water-soluble polyethylene glycol was completed, a layer of biocompatible polyurethane resin was coated on the front section of the graphene fiber, and a second curing treatment was carried out at a temperature of 120 °C for 30 minutes to ensure that the resin was completely cured and adhered to the surface of the graphene fiber, thereby enhancing its mechanical strength; after ensuring the stability of the biocompatible polyurethane resin, through spraying technology, silicone rubber was evenly coated on the rear section of the graphene fiber. After the coating was completed, a third curing treatment was carried out in an environment at 80 °C for 2 hours to ensure that the insulating layer had good mechanical strength and electrical properties, and the preparation of the flexible carbon-based fiber nerve electrode with zoned coating regulation was completed.

[0045] Connecting the rear end of the graphene fiber to circuit components can achieve signal acquisition.

[0046] In view of the large number of embodiments of the present invention, the raw materials and dosages involved can be selected according to actual needs within the limited range. The experimental data of each embodiment are numerous and not suitable for listing and explaining them one by one here. However, the contents to be verified and the final conclusions obtained in each embodiment are close. Therefore, the verification contents of each embodiment are not explained one by one here.

[0047] The above is only a detailed description of the preferred embodiments and principles of the present invention. For those of ordinary skill in the art, according to the idea provided by the present invention, there will be changes in the specific implementation manners, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A flexible carbon-based fiber nerve electrode with partitioned coating regulation, characterized in that, It includes a single flexible carbon-based fiber. The flexible carbon-based fiber includes a front end, a front section, a rear section, and a rear end that are sequentially distributed along its axial direction. The front end is coated with a water-soluble rigid polymer, the front section is coated with a biocompatible thermosetting rigid resin, the rear section is coated with a rigid or flexible insulating resin, and the rear end serves as an electrode joint.

2. The flexible carbon-based fiber nerve electrode according to claim 1, wherein, The water-soluble rigid polymer includes at least one of polyvinyl alcohol and polyethylene glycol.

3. The flexible carbon-based fiber nerve electrode according to claim 2, wherein The cross-section of the water-soluble rigid polymer coated on the front end along the fiber axial direction is a semi-circular structure.

4. The flexible carbon-based fiber nerve electrode according to claim 1, wherein The biocompatible thermosetting rigid resin includes at least one of epoxy resin, phenolic resin, and polyurethane resin.

5. The flexible carbon-based fiber nerve electrode according to claim 1, wherein The flexible insulating resin includes at least one of silicone rubber and polydimethylsiloxane, and the rigid insulating resin is polyimide.

6. The flexible carbon-based fiber nerve electrode according to any one of claims 1-5, characterized in that, The flexible carbon-based fiber is a carbon nanotube fiber, a graphene oxide fiber, or a graphene fiber.

7. The flexible carbon-based fiber nerve electrode according to claim 6, characterized in that, The diameter of the flexible carbon-based fiber is 15 - 30 μm.

8. The preparation method of the flexible carbon-based fiber nerve electrode according to any one of claims 1-7, characterized in that, It includes the following steps: (1) Coat the front end of the flexible carbon-based fiber with a water-soluble rigid polymer, and carry out a curing treatment at 60 - 80 °C for 20 - 60 minutes; (2) Coat the front section of the flexible carbon-based fiber with a biocompatible thermosetting rigid resin, and carry out a curing treatment at 120 - 180 °C for 30 - 120 minutes; (3) Use a flexible or rigid insulating resin to coat the rear section of the flexible carbon-based fiber by spin coating, dip coating, or spraying techniques, and carry out a curing treatment at 80 - 150 °C for 1 - 3 hours.

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