Composite structure flexible neural electrode based on micro-nano fibers and preparation method and application thereof

Abstract

The invention discloses a composite structure flexible neural electrode based on micro-nano fibers and a preparation method and application thereof, the electrode has a coaxial heterostructure, and comprises a substrate, a conductive layer and an insulating layer from inside to outside; the substrate is made of carbon fibers; the conductive layer is obtained by coating a metal conductor on the surface of the substrate; and the insulating layer is obtained by depositing an insulating material on the surface of the conductive layer. The composite structure flexible neural electrode based on the micro-nano fibers can adapt to brain tissue modulus, and has excellent conductivity and high charge injection capacity.

Description

Technical Field

[0001] The present invention belongs to the field of material science and engineering technology, and specifically relates to a composite structure flexible neural electrode based on micro-nano fibers. Background Art

[0002] Neural electrodes are key components in the research and application of brain-computer interface technology. They play a key role in connecting biological nerves and electronic devices, and are the main tool for recording biological neural electrical signals. Neural electrodes used in the brain are generally manufactured using hard conductive materials as substrates for the purpose of convenient implantation. However, the Young's modulus of neural electrodes made of hard conductive materials as substrates is seriously mismatched with the Young's modulus of brain tissue. This huge mechanical mismatch can easily induce acute tissue rejection reactions, leading to tissue coating, blood-brain barrier rupture, and more serious chronic neurodegenerative diseases. The above series of problems make it difficult for silicon-based electrodes to work stably and for a long time in biological tissues. Therefore, the production of reliable, modulus-matched, long-term stable and biocompatible neural electrodes is an important goal of current research.

[0003] Therefore, a flexible neural electrode is needed. Increasing the flexibility of the electrode and reducing the Young's modulus of the electrode material to improve the matching degree between the electrode and the cortical tissue can reduce tissue damage during implantation, delay electrode failure time, and increase electrode service life. Compared with hard conductive materials, carbon-based fibers as the substrate are more flexible and have a Young's modulus closer to brain tissue, which can significantly reduce acute and chronic damage during and after electrode implantation, and can also reduce rejection reactions.

[0004] However, there are still many shortcomings in using carbon-based fibers to make neural electrodes. As a good conductor among non-metallic materials, carbon-based fibers are still not as conductive as metal conductors. When using ordinary carbon fibers as neural electrodes, it is impossible to avoid the electrophysiological activities of other cells contacting the fibers during the reception of neural electrical signals, thereby causing interference. Another disadvantage is that during the implantation process, the carbon fibers are too soft to break through the meninges and enter the brain tissue, so neural electrical signals cannot be collected. In this regard, it is necessary to manufacture a neural electrode that retains the flexibility of carbon fibers and has the conductive properties of metal, retains only one conductive site at the end of the electrode, and hardens its surface. At the same time, a high charge injection capacity of the electrode is also a crucial factor in achieving efficient electrical signal transmission and neural stimulation. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flexible neural electrode which can adapt to the modulus of brain tissue and has excellent electrical conductivity and high charge injection capacity.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a composite structure flexible neural electrode based on micro-nano fibers, which has a coaxial heterogeneous structure and includes a substrate, a conductive layer and an insulating layer from the inside to the outside;

[0008] The substrate is carbon fiber;

[0009] The conductive layer is obtained by plating a metal conductor on the surface of the substrate;

[0010] The insulating layer is obtained by depositing insulating material on the surface of the conductive layer.

[0011] Furthermore, the diameter of the carbon fiber is 5-50 μm; the thickness of the conductive layer is 60-480 nm; and the thickness of the insulating layer is 400 nm-1 μm.

[0012] Furthermore, the carbon fiber is prepared by spinning a polyacrylonitrile spinning solution to obtain polyacrylonitrile fiber, and then the polyacrylonitrile fiber is pre-oxidized at 200-300°C and carbonized at 800-1800°C in sequence.

[0013] Furthermore, the metal conductor includes one of gold, silver and platinum; the insulating material includes Al 2 O 3 , one of the poly(p-dichlorotoluene).

[0014] Furthermore, the electrode of the present invention also includes a layer of absorbable hardening material attached to the surface of the insulating layer as a hardening shell.

[0015] Furthermore, the absorbable hardening material includes one of polyethylene glycol, chitosan, and biological tissue glue.

[0016] In addition, the present invention also provides a method for preparing the above-mentioned micro-nano fiber-based composite structure flexible neural electrode, comprising the following steps:

[0017] S1. preparing polyacrylonitrile fiber by spinning the polyacrylonitrile spinning solution, placing the polyacrylonitrile fiber in a heating device, pre-oxidizing at 200-300° C. and carbonizing at 800-1800° C., respectively, to obtain carbon fiber as a substrate;

[0018] S2. A conductive layer is obtained by coating a metal conductor on the surface of the substrate by magnetron sputtering or vacuum evaporation;

[0019] S3. Depositing an insulating material onto the surface of the conductive layer by atomic layer deposition or chemical vapor deposition to obtain an insulating layer;

[0020] The composite structure flexible neural electrode based on micro-nano fibers is obtained.

[0021] Furthermore, when step S2 adopts the magnetron sputtering method, the process conditions are: 2-16 times of metal target sputtering for 100s or 110s and 5mA or 7mA, and the thickness of the prepared conductive layer is 60-480nm.

[0022] Furthermore, the method further includes step S4 of attaching a layer of absorbable hardening material on the surface of the insulating layer as a hardened shell.

[0023] In addition, the present invention also provides the application of the above-mentioned micro-nano fiber-based composite structure flexible neural electrode in neural signal detection, with a conductive site at each end of the electrode, one end connected to a wire and the other end used to collect neural electrical signals.

[0024] The present invention has the following beneficial effects:

[0025] (1) The present invention significantly changes the flexibility disadvantage of the neural electrodes made of traditional hard conductive materials, making them more compatible with the Young's modulus of brain tissue and causing less trauma to the brain tissue.

[0026] (2) The present invention solves the problem that the electrical conductivity of carbon fiber is not high enough and the impedance is large. The electrode of the present invention has low impedance characteristics and therefore has excellent conductive properties. At the same time, the AC impedance of the electrode can be regulated by changing the thickness of the conductive layer.

[0027] (3) The present invention has conductive sites only at the two ends of the fiber, and the entire circumference of the fiber is insulated, which effectively avoids interference from bioelectric signals of other non-target cells.

[0028] (4) The present invention solves the problem that the flexible fiber is not hard enough to break through the brain tissue. A hardened shell is added to the fiber electrode so that the flexible fiber can smoothly enter the brain tissue and reach the target nerve for collection.

[0029] (5) The present invention significantly improves the charge injection capacity of the electrode tip by alternating multiple conductive and insulating layers, so that the electrode has a more significant effect in electrical signal transmission and nerve stimulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic cross-sectional view of the flexible neural electrode with a composite structure based on micro-nano fibers of the present invention.

[0031] Figure 2 It is a cross-sectional schematic diagram of the flexible neural electrode with a composite structure based on micro-nano fibers of the present invention.

[0032] Figure 3 This is an electron microscope picture of the flexible neural electrode with a composite structure based on micro-nano fibers of the present invention.

[0033] Figure 4This is the AC impedance spectrum of the micro-nano fiber-based composite structure flexible neural electrode prepared in Examples 1-7.

[0034] Figure 5 This is the volt-ampere characteristic curve of the micro-nano fiber-based composite structure flexible neural electrode of Example 5.

[0035] Figure 6 This is the biphasic pulse curve of the micro-nano fiber-based composite structure flexible neural electrode of Example 5.

[0036] Description of reference numerals: 1-substrate, 2-conductive layer, 3-insulating layer, 4-hardened shell DETAILED DESCRIPTION

[0037] like Figure 1 , 2 As shown, a composite structure flexible neural electrode based on micro-nano fibers of the present invention has a coaxial heterogeneous structure, which comprises a substrate 1, a conductive layer 2 and an insulating layer 3 from the inside to the outside.

[0038] The substrate 1 is carbon fiber;

[0039] The conductive layer 2 is obtained by plating a metal conductor on the surface of the substrate;

[0040] The insulating layer 3 is obtained by depositing insulating material on the surface of the conductive layer.

[0041] The diameter of the carbon fiber is 5-50μm; the thickness of the conductive layer is 60-480nm; the thickness of the insulating layer is 400nm-1μm. Controlling the diameter of the substrate can be more widely applied to a variety of conditions; controlling the thickness of the conductive layer can ensure that the present invention has good impedance while not affecting the modulus of the entire electrode due to an overly thick conductive layer; the thickness of the insulating layer should be selected to ensure the density of its coating and reduce the impact of its thickness on impedance and modulus.

[0042] The carbon fiber is prepared by spinning a polyacrylonitrile spinning solution to obtain polyacrylonitrile fiber, and then the polyacrylonitrile fiber is pre-oxidized at 200-300° C. and carbonized at 800-1800° C. in sequence.

[0043] The metal conductor includes one of gold, silver and platinum.

[0044] The insulating material includes Al 2 O 3 , one of the poly(p-dichlorotoluene).

[0045] like Figure 2 As shown, the electrode further includes a layer of absorbable hardening material attached to the surface of the insulating layer 3 as a hardening shell.

[0046] The absorbable hardening material includes one of polyethylene glycol, chitosan and biological tissue glue. These colloid materials can harden quickly and degrade within the target time and are safe, non-toxic and have good biocompatibility.

[0047] Example 1

[0048] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0049] First, acrylonitrile: itaconic acid: acrylamide mass ratio of 98:1:1 was dissolved in dimethyl sulfoxide solvent at room temperature, stirred evenly, and prepared into polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution was injected into a syringe for stretching and spinning, and the fibers collected in the mold were polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers were placed in a heating device for pre-oxidation at 200°C and carbonization at 800°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers was 50μm.

[0050] Secondly, the substrate was placed in a magnetron sputtering device, and gold target sputtering was performed on the substrate surface 16 times at 110 s and 7 mA to prepare a conductive layer with a thickness of 480 nm.

[0051] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and an Al layer with a thickness of 1 μm is deposited by atomic layer deposition (ALD). 2 O 3 Deposited onto the surface of the conductive layer as an insulating layer.

[0052] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0053] Example 2

[0054] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0055] First, polyacrylonitrile was dissolved in dimethylformamide, stirred at 50°C until completely dissolved, and a solution with a concentration of 0.42kg / L was prepared. The above solution was dissolved in 0.02kg / L of itaconic acid aqueous solution to finally prepare a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution was injected into a syringe for wet spinning, and the fibers collected in the mold were polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers were placed in a heating device for pre-oxidation at 250°C and carbonization at 1450°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers was 5μm.

[0056] Secondly, the substrate was placed in a magnetron sputtering device, and gold target sputtering was performed on the substrate surface four times at 110 s and 7 mA to prepare a conductive layer with a thickness of 120 nm.

[0057] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and poly(p-dichlorotoluene) is deposited on the surface of the conductive layer by chemical vapor deposition (CVD) to prepare an 800 nm insulating layer.

[0058] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0059] Example 3

[0060] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0061] First, acrylonitrile: dimethyl sulfoxide: sodium dodecyl sulfate in a mass ratio of 24:200:1 is dissolved at 60°C and stirred evenly to prepare a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution is injected into a syringe for stretching and spinning, and the fibers collected in the mold are polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers are placed in a heating device for pre-oxidation at 300°C and carbonization at 1800°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers is 10 μm.

[0062] Secondly, the substrate was placed in a magnetron sputtering device, and gold target sputtering was performed on the substrate surface 16 times at 110 s and 7 mA to prepare a conductive layer with a thickness of 480 nm.

[0063] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and poly(p-dichlorotoluene) is deposited on the surface of the conductive layer by chemical vapor deposition (CVD) to prepare a 400 nm insulating layer.

[0064] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0065] Example 4

[0066] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0067] First, acrylonitrile: dimethyl sulfoxide: sodium dodecyl sulfate in a mass ratio of 24:200:1 is dissolved at 60°C and stirred evenly to prepare a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution is injected into a syringe for stretching and spinning, and the fibers collected in the mold are polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers are placed in a heating device for pre-oxidation at 300°C and carbonization at 1800°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers is 10 μm.

[0068] Secondly, the substrate was placed in a magnetron sputtering device, and gold target sputtering was performed on the substrate surface 12 times at 110 s and 7 mA to prepare a conductive layer with a thickness of 360 nm.

[0069] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and poly(p-dichlorotoluene) is deposited on the surface of the conductive layer by chemical vapor deposition (CVD) to prepare a 400 nm insulating layer.

[0070] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0071] Example 5

[0072] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0073] First, acrylonitrile: dimethyl sulfoxide: sodium dodecyl sulfate in a mass ratio of 24:200:1 is dissolved at 60°C and stirred evenly to prepare a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution is injected into a syringe for stretching and spinning, and the fibers collected in the mold are polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers are placed in a heating device for pre-oxidation at 300°C and carbonization at 1800°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers is 10 μm.

[0074] Secondly, the substrate was placed in a magnetron sputtering device, and gold target sputtering was performed on the substrate surface 8 times for 110 s and 7 mA to prepare a conductive layer with a thickness of 240 nm.

[0075] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and poly(p-dichlorotoluene) is deposited on the surface of the conductive layer by chemical vapor deposition (CVD) to prepare a 400 nm insulating layer.

[0076] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0077] Example 6

[0078] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0079] First, acrylonitrile: dimethyl sulfoxide: sodium dodecyl sulfate in a mass ratio of 24:200:1 is dissolved at 60°C and stirred evenly to prepare a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution is injected into a syringe for stretching and spinning, and the fibers collected in the mold are polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers are placed in a heating device for pre-oxidation at 300°C and carbonization at 1800°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers is 10 μm.

[0080] Secondly, the substrate was placed in a magnetron sputtering device, and gold target sputtering was performed on the substrate surface four times at 110 s and 7 mA to prepare a conductive layer with a thickness of 120 nm.

[0081] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and poly(p-dichlorotoluene) is deposited on the surface of the conductive layer by chemical vapor deposition (CVD) to prepare a 400 nm insulating layer.

[0082] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0083] Example 7

[0084] The composite structure flexible neural electrode based on micro-nano fibers is prepared according to the following method:

[0085] First, polyacrylonitrile was dissolved in dimethylformamide, stirred at 50°C until completely dissolved, and a solution with a concentration of 0.42kg / L was prepared. The above solution was dissolved in 0.02kg / L of itaconic acid aqueous solution to finally prepare a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution was injected into a syringe for wet spinning, and the fibers collected in the mold were polyacrylonitrile fibers for preparing carbon fibers. The polyacrylonitrile fibers were placed in a heating device for pre-oxidation at 250°C and carbonization at 1450°C to obtain carbon fibers as a substrate, and the diameter of the obtained carbon fibers was 5μm.

[0086] Secondly, the substrate was placed in a magnetron sputtering device, and silver target sputtering was performed on the substrate surface 14 times at 100 s and 5 mA to prepare a conductive layer with a thickness of 60 nm.

[0087] Secondly, the substrate with the conductive layer is placed in an atomic layer deposition device, and poly(p-dichlorotoluene) is deposited on the surface of the conductive layer by chemical vapor deposition (CVD) to prepare a 400 nm insulating layer.

[0088] Finally, a layer of polyethylene glycol (PEG4000) with a relative mass fraction of 4000 in a molten state is attached to the surface of the insulating layer as a hardened shell of the electrode.

[0089] Performance test methods and results of the micro-nano fiber-based composite structure flexible neural electrodes prepared in Examples 1-7:

[0090] By simulating the brain tissue environment in phosphate buffered saline (PBS), in a two-electrode system, using Examples 1-7 as the working electrode and a platinum wire as the counter electrode, the AC impedance spectrum of the electrode prepared by the present invention was tested. Figure 4 As shown, it is shown that the electrode of the present invention has low impedance characteristics and thus has excellent conductive properties. In the same solution, the CV curve is tested in a three-electrode system with Example 5 as the working electrode, a platinum wire electrode as the counter electrode, and Ag / AgCl as the reference electrode. Figure 5 As shown in Figure 2, the charge storage capacity is calculated to be 300-400 mC cm -2 The biphasic pulse test was performed in the same solution and three-electrode system to calculate the charge injection capacity, such as Figure 6 As shown, the charge injection capacity obtained is 15-25 mC cm -2 This indicates that the electrode of the present invention has a high charge injection capacity.

Claims

1. A composite structure flexible neural electrode based on micro-nano fibers, characterized in that: It has a coaxial heterostructure, which includes a substrate, a conductive layer and an insulating layer from the inside to the outside; The substrate is carbon fiber; The conductive layer is obtained by plating a metal conductor on the surface of the substrate; The insulating layer is obtained by depositing insulating material on the surface of the conductive layer.

2. The micro-nano fiber composite structure flexible neural electrode according to claim 1, characterized in that: The diameter of the carbon fiber is 5-50 μm; the thickness of the conductive layer is 60-480 nm; and the thickness of the insulating layer is 400 nm-1 μm.

3. The micro-nano fiber composite structure flexible neural electrode according to claim 1, characterized in that: The carbon fiber is prepared by spinning a polyacrylonitrile spinning solution to obtain polyacrylonitrile fiber, and then the polyacrylonitrile fiber is pre-oxidized at 200-300° C. and carbonized at 800-1800° C. in sequence.

4. The micro-nano fiber-based composite structure flexible neural electrode according to claim 1, characterized in that: The metal conductor includes one of gold, silver and platinum; the insulating material includes one of Al2O3 and poly(p-dichlorotoluene).

5. The micro-nano fiber composite structure flexible neural electrode according to claim 1, characterized in that: The method also includes attaching a layer of absorbable hardening material on the surface of the insulating layer as a hardening shell.

6. The micro-nano fiber-based composite structure flexible neural electrode according to claim 5, characterized in that: The absorbable hardening material includes one of polyethylene glycol, chitosan, and biological tissue glue.

7. The method for preparing a composite structure flexible neural electrode based on micro-nano fibers according to claim 1, characterized in that: The following steps are involved: S1. preparing polyacrylonitrile fiber by spinning the polyacrylonitrile spinning solution, placing the polyacrylonitrile fiber in a heating device, pre-oxidizing at 200-300° C. and carbonizing at 800-1800° C., respectively, to obtain carbon fiber as a substrate; S2. A conductive layer is obtained by coating a metal conductor on the surface of the substrate by magnetron sputtering or vacuum evaporation; S3. Depositing an insulating material onto the surface of the conductive layer by atomic layer deposition or chemical vapor deposition to obtain an insulating layer; The composite structure flexible neural electrode based on micro-nano fibers is obtained.

8. The preparation method according to claim 7, characterized in that: When the magnetron sputtering method is used in step S2, the process conditions are: 2-16 times of metal target sputtering for 100s or 110s and 5mA or 7mA, and the thickness of the prepared conductive layer is 60-480nm.

9. The preparation method according to claim 7, characterized in that: The method further includes step S4 of attaching a layer of absorbable hardening material on the surface of the insulating layer as a hardened shell.

10. The application of a composite structure flexible neural electrode based on micro-nano fibers as described in claim 1 in neural signal detection, wherein there is a conductive site at each end of the electrode, one end is connected to a wire and the other end is used to collect neural electrical signals.

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