Composite carbon fiber material as well as preparation method and application thereof

Abstract

The invention provides a composite carbon fiber material as well as a preparation method and application thereof. The preparation method comprises the following steps: sequentially carrying out cleaning and heat treatment oxidation on carbon fibers to obtain activated carbon fibers; and depositing a layer of conductive polymer on the activated carbon fiber by an electrochemical deposition method, and then washing and drying to obtain the composite carbon fiber material. The carbon fiber is subjected to surface modification by adopting a heat treatment oxidation method, so that the interface impedance can be reduced. An electrochemical deposition method is further adopted, a layer of conductive polymer is deposited on the surface of the activated carbon fiber, the core-shell structure carbon fiber with the activated carbon fiber core / the conductive polymer shell is formed, and the interface impedance can be further reduced.

Description

Technical Field

[0001] This invention relates to the field of bioelectrode technology, specifically to a composite carbon fiber material, its preparation method, and its applications. Background Technology

[0002] Existing commercial bioelectrodes typically employ metal electrodes, such as platinum, iridium, and gold. Because metal electrodes use electrons as charge carriers, their carrier conversion efficiency with ion-conducting biological tissues is low, resulting in high interfacial impedance. Although metal electrodes can be surface-modified through various methods, the interfacial impedance remains high, and the cost is prohibitive.

[0003] Carbon fiber is considered an ideal electrochemical material due to its high electrical conductivity and chemical inertness. It not only possesses advantages such as fast mass transfer rate, rapid response, and high sensitivity, but also exhibits chemical stability and a wide potential window, thus finding wide application in fields such as small molecule detection, single-cell analysis, and in vivo monitoring. However, carbon fiber also uses electrons as charge carriers, and its relatively low specific surface area directly leads to low carrier conversion efficiency and insufficient effective electrochemical area between it and biological tissues. This, coupled with poor contact due to interfacial hydrophobicity, results in high interfacial impedance, ultimately limiting its application as a bioelectrode. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to reduce the interfacial impedance of carbon fibers.

[0005] The present invention solves the above-mentioned technical problems through the following technical means: The first aspect of the present invention provides a method for preparing a composite carbon fiber material, comprising the following steps: sequentially cleaning and oxidizing carbon fibers to obtain activated carbon fibers; depositing a layer of conductive polymer on the activated carbon fibers by electrochemical deposition; and then washing and drying to obtain the composite carbon fiber material.

[0006] Beneficial effects: This invention employs a thermal oxidation method to modify the surface of carbon fibers. This method is simple, environmentally friendly, and free of chemical pollution. After activation by the thermal oxidation method, the carbon fiber surface becomes rougher, significantly increasing the specific surface area. Simultaneously, it increases the number of surface active sites, enhances the electrochemical activity of the carbon fiber, and reduces its surface hydrophobicity. This solves the problems of insufficient effective electrochemical area and poor interfacial contact in carbon fibers, thereby reducing their interfacial impedance.

[0007] This invention further employs an electrochemical deposition method to deposit a layer of conductive polymer on the surface of activated carbon fibers, forming a core-shell structure carbon fiber with an activated carbon fiber core and a conductive polymer shell. The activated, roughened carbon fiber surface increases the contact area with the conductive polymer layer, and the active groups form polar interactions such as hydrogen bonds with the conductive polymer, thereby improving the interfacial adhesion between the carbon fiber and the conductive polymer and effectively solving the problem of easy detachment of the coating layer. At the same time, the conductive polymer has both ionic conductivity and electron / hole conductivity mechanisms, so it can serve as a conductive coupling interface material between biological tissue (ionic conductivity) and carbon fiber (electronic conductivity), further reducing interfacial impedance.

[0008] Preferably, the heat treatment temperature is 350℃~450℃ and the heat treatment time is 10min~2h.

[0009] Preferably, the electrochemical deposition method involves placing activated carbon fibers in a conductive polymer electroplating solution for electrochemical deposition.

[0010] Preferably, the conductive polymer electroplating solution includes a conductive polymer monomer and a solvent, wherein the conductive polymer includes one or more of poly(ethylene thiophene), polypyrrole, or polyaniline.

[0011] Preferably, the conductive polymer monomer includes one or more of 3,4-ethylenedioxythiophene, pyrrole, or aniline.

[0012] Preferably, the solvent includes one or more of propylene carbonate and sulfuric acid solution.

[0013] Preferably, the conductive polymer electroplating solution further includes a co-solvent, which includes one or more of lithium perchlorate and sodium dodecyl sulfate.

[0014] Preferably, the electrochemical deposition method is performed using a chronopotentiometric method with the following parameters: voltage of 1.1V~1.2V; deposition time of 100s~1000s.

[0015] Preferably, the electrochemical deposition method is performed using cyclic voltammetry with the following parameters: lower limit potential of -0.5V to -0.2V, upper limit potential of 1.0V to 1.5V, and 2 to 10 cycles.

[0016] Preferably, the washing process involves soaking the food in deionized water and anhydrous ethanol for 1 minute each.

[0017] Preferably, the drying process is carried out at 80℃~100℃ for 30 minutes.

[0018] The second aspect of the present invention provides a method for preparing the above-mentioned composite carbon fiber material to obtain the composite carbon fiber material.

[0019] Beneficial effects: The composite carbon fiber material of the present invention has stable bioelectric signal intensity and good biocompatibility.

[0020] The third aspect of this invention provides a method for preparing the above-mentioned composite carbon fiber material and its application as a bioelectrode.

[0021] The fourth aspect of this invention provides a method for preparing the above-mentioned composite carbon fiber material and its application in wearable electronic devices. Attached Figure Description

[0022] Figure 1 These are schematic diagrams of the composite carbon fiber materials obtained in Examples 1-3 of this invention. Figure 2 These are morphological images of the composite carbon fiber materials and activated carbon fibers obtained in Examples 1-3 of this invention; Figure 3 These are diagrams of the solutions after sonication for Comparative Example 1 and Example 3; the left side shows the solution after sonication for Comparative Example 1, and the right side shows the solution after sonication for Example 3. Figure 4 These are cyclic voltammetry diagrams of the composite carbon fiber materials prepared in Examples 1-3 of this invention and the untreated carbon fiber. Figure 5 These are cyclic voltammetry diagrams from the preparation of composite carbon fiber materials in Example 3 and Comparative Example 1 of this invention. Figure 6 This is the electrochemical impedance spectroscopy of the composite carbon fiber material, platinum wire, and activated carbon fiber obtained in Embodiment 2 of the present invention; Figure 7 The data are the electrochemical impedance data of the composite carbon fiber material prepared in Example 2 of the present invention; where A represents the electrochemical impedance of the composite carbon fiber material over time from 0 to 21 days at 0.1 Hz; and B represents the amplitude-frequency diagram and phase-frequency diagram of the composite carbon fiber material on day 1 and day 21. Figure 8 This is a cytotoxicity test diagram of the composite carbon fiber material prepared in Example 2 of the present invention; Figure 9 This is a graph of bioelectrical signals collected from mice over 5 consecutive days using composite carbon fiber material and platinum wire prepared in Example 2 of this invention as bioelectrodes. Figure 10 This is a graph showing the TNF-α level in peripheral serum one month after the composite carbon fiber material and activated carbon fiber prepared in Example 2 of this invention were subcutaneously implanted. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0024] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0025] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0026] Example 1 This embodiment provides a method for preparing composite carbon fiber materials, the specific steps of which are as follows: S1 Preparation of Activated Carbon Fibers 20 mg of carbon fiber (approximately 10 μm in diameter) was soaked in acetone for 10 min and then rinsed repeatedly with water for 5 min to remove organic impurities and stains adhering to the surface of the carbon fiber. The carbon fiber was then placed in a tube furnace for heat treatment to oxidize the surface of the carbon fiber. The heat treatment temperature was 400℃ and the heat treatment time was 15 min to obtain activated carbon fiber.

[0027] S2 Preparation of Composite Carbon Fiber Materials 0.7 g of lithium perchlorate and 0.17 g of 3,4-ethylenedioxythiophene were dissolved in 60 mL of propylene carbonate to obtain a polyethylenedioxythiophene electroplating solution.

[0028] Then, using activated carbon fiber as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode, the three electrodes were correctly connected to an electrochemical workstation. Simultaneously, the three electrodes were immersed in a polyethylene glycol thiophene electroplating solution, and a polyethylene glycol thiophene film was coated onto the surface of the activated carbon fiber using a chronopotentiometric method. The deposition voltage was 1.2 V, and the deposition time was 800 s. After deposition, the activated carbon fiber was sequentially immersed in deionized water and anhydrous ethanol for 1 min each, and then dried at 80℃ for 30 min to obtain the composite carbon fiber material.

[0029] Example 2 This embodiment provides a method for preparing composite carbon fiber materials, the specific steps of which are as follows: The preparation of activated carbon fibers in S1 is the same as step S1 in Example 1.

[0030] S2 Preparation of Composite Carbon Fiber Materials Dissolve 1.75 g of sodium dodecyl sulfate and 0.2 g of pyrrole in 60 mL of water to obtain a polypyrrole electroplating solution.

[0031] Then, using activated carbon fiber as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode, the three electrodes were correctly connected to an electrochemical workstation. Simultaneously, all three electrodes were immersed in a polypyrrole electroplating solution, and a polypyrrole film was coated onto the surface of the activated carbon fiber using a chronopotentiometric method. The deposition voltage was 1.1 V, and the deposition time was 800 s. After deposition, the activated carbon fiber was immersed in deionized water and anhydrous ethanol for 1 min each, and then dried at 80℃ for 30 min to obtain the composite carbon fiber material.

[0032] Example 3 This embodiment provides a method for preparing composite carbon fiber materials, the specific steps of which are as follows: The preparation of activated carbon fibers in S1 is the same as step S1 in Example 1.

[0033] S2 Preparation of Composite Carbon Fiber Materials 600 μL of aniline was dissolved in 60 mL of 0.5 M sulfuric acid solution to obtain a polyaniline electroplating solution.

[0034] Then, using activated carbon fiber as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode, the three electrodes were correctly connected to an electrochemical workstation. Simultaneously, all three electrodes were immersed in a polyaniline electroplating solution. Cyclic voltammetry was used to coat the surface of the activated carbon fiber with a polyaniline film. The lower limit potential was -0.2V, and the upper limit potential was 1.2V; the scan rate was 50 mV / s, and the number of cycles was 7. After deposition, the activated carbon fiber was immersed in deionized water and anhydrous ethanol for 1 min each, and then dried at 80℃ for 30 min to obtain the composite carbon fiber material.

[0035] according to Figure 1 As shown, this invention increases the effective specific surface area and surface active sites of carbon fibers by oxidizing them through heat treatment; then, a conductive polymer deposition layer is formed on the surface of the carbon fibers by in-situ polymerization using electrochemical deposition, thus forming a composite carbon fiber material. When the composite carbon fiber material is placed in an ionic solution, the conductive polymer shell has both ionic and electronic / hole conductivity properties, which can efficiently couple biological tissue (ionic conductivity) and electrode materials (electronic conductivity), thereby significantly reducing the interfacial impedance of the composite carbon fiber material.

[0036] Comparative Example 1 This comparative example provides a method for preparing composite carbon fiber material. The difference between this comparative example and Example 3 is that the carbon fiber was not heat-treated, while everything else is the same as in Example 3.

[0037] The cyclic voltammetry curves recorded when depositing polyaniline using cyclic voltammetry in Example 3 and Comparative Example 1 are as follows: Figure 5 As shown, compared with the composite carbon fiber material prepared in Comparative Example 1, the redox peak positions of the activated carbon fiber in Example 3 remained basically unchanged, indicating that the polyaniline deposited on the activated carbon fiber had better conductivity; Figure 5 As can be seen from the results, the composite carbon fiber material prepared in Example 3 exhibits a greater current increase per electroplating cycle, indicating that the polyaniline deposited on the activated carbon fiber in each cycle enhances the electrochemical activity.

[0038] Experimental Example The composite carbon fiber materials prepared in Examples 1-3 and Comparative Example 1 were subjected to performance characterization.

[0039] 1. Surface morphology characterization of composite carbon fiber materials The activated carbon fibers and the composite carbon fiber materials prepared in Examples 1-3 were dried in an oven at 60°C for 2 hours. The fiber length was cut to about 2 cm. The surface morphology was observed using a cold field emission scanning electron microscope (SEM) with an accelerating voltage of 15 kV.

[0040] The results are as follows Figure 2 As shown, the composite carbon fiber materials prepared in Examples 1-3 are all coated with a conductive polymer deposition layer. This deposition layer exhibits a loose and porous network structure or a wrinkled structure, which is significantly different from that of activated carbon fiber, proving that a complete conductive polymer shell has been successfully deposited on the surface of activated carbon fiber.

[0041] 2. Stability testing of composite carbon fiber materials The composite carbon fiber materials prepared in Examples 1-3 and Comparative Example 1 were placed in beakers containing 10 mL of deionized water and sonicated in a 600 W water bath for 1 h. The changes in the solution were then observed.

[0042] The results are as follows Figure 3 As shown, the left side shows the color of the solution after ultrasound in Comparative Example 1. It can be seen that the solution color has turned significantly green, indicating that the polyaniline deposition layer has been significantly detached. The reason is that the carbon fiber core without heat treatment is not tightly bonded to the conductive polymer shell. The right side shows the color of the solution after ultrasound in Example 3. The solution color has not changed significantly, indicating that the conductive polymer shell and the activated carbon fiber core in the composite carbon fiber materials prepared in Examples 1-3 are firmly bonded and the structure is stable.

[0043] 3. Electrochemical activity characterization of composite carbon fiber materials Cyclic voltammetry was performed on an electrochemical workstation using a three-electrode system. The composite carbon fiber materials prepared in Examples 1-3 and untreated carbon fibers were used as working electrodes, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire was used as the auxiliary electrode. In a 0.15 mol / L NaCl solution, the voltage range was -0.5 V to 1.0 V, and the scan rate was 25 mV / s.

[0044] The results are as follows Figure 4 As shown, the composite carbon fiber materials exhibit improved electrochemical activity compared to untreated carbon fibers. Among them, the composite carbon fiber material prepared in Example 2 showed no obvious redox peaks within the detection range and had a large current density, indicating that it had the best electrochemical activity.

[0045] 4. Electrochemical impedance characterization of composite carbon fiber materials The electrochemical impedance of platinum wire, activated carbon fiber, and the composite carbon fiber material prepared in Example 2 was measured in a 0.1 mol / L phosphate buffer solution at pH 7.4. Figure 6 As shown, the decreasing trend from platinum wire > activated carbon fiber > Example 3 verifies that the conductive polymer shell has a significant effect on reducing the interfacial impedance of activated carbon fiber. Especially in the low-frequency region (0.1Hz~500Hz) where bioelectric signals are common, the interfacial impedance of the composite carbon fiber material prepared in Example 2 is about 2 to 3 orders of magnitude lower than that of platinum wire.

[0046] 5. Electrochemical stability characterization of composite carbon fiber materials The composite carbon fiber material prepared in Example 2 was immersed in 0.1 mol / L phosphate buffer solution (pH=7.4) for 21 days, and the electrochemical impedance spectroscopy was detected at different time points during the period.

[0047] The results are as follows Figure 7 As shown, the impedance of the composite carbon fiber material remained stable throughout the detection period, demonstrating the electrochemical stability of the composite carbon fiber material.

[0048] 6. Cytotoxicity characterization of composite carbon fiber materials The composite carbon fiber materials prepared in Examples 1-3 were subjected to double sterilization by immersion in 75% ethanol for 30 min and ultraviolet irradiation for 60 min, respectively, and then co-cultured with HeLa cells for 72 h. The cytotoxicity of the materials was detected by the MTT assay. The results are as follows: Figure 8 As shown, the composite carbon fiber materials prepared in Examples 1-3 all showed no significant cytotoxicity.

[0049] 7. Composite carbon fiber materials are used for implantable bioelectrical signal acquisition and stability characterization. The composite carbon fiber material prepared in Example 2 was used as the bioelectric signal acquisition electrode and connected to the wireless acquisition module of a small animal radio physiological recording device. Healthy adult C57 mice were selected, anesthetized, and prepared. A bone window of about 0.5 mm was made in the skull, and medical screws were screwed in around the periphery as grounding and fixation points. The composite carbon fiber material or platinum wire was inserted into the cerebral cortex and trapezius muscle of the neck of the mouse. Then, bone cement was used to fix the wireless acquisition module to the surface of the skull and sutured. After the operation, the mice were housed in single cages, analgesicated, and continuously monitored until the signal acquisition ended on the 5th day. The mice were then euthanized by cervical dislocation.

[0050] The results are as follows Figure 9 As shown, the bioelectric signals recorded by the composite carbon fiber material prepared in Example 2 during the 5-day collection period showed no significant attenuation, and the signal intensity was significantly better than that of platinum wire.

[0051] 8. Testing the electrostimulation effect of composite carbon fiber materials Healthy adult C57 mice were selected, and after anesthesia, the sciatic nerve was exposed and separated for about 5 mm. The composite carbon fiber material prepared in Example 2 was gently placed under the sciatic nerve as a stimulation electrode to ensure full contact. Then, a single stimulation was applied with a frequency of 0.1 Hz, a pulse width of 0.2 ms, and a voltage of 2 V. The gastrocnemius muscle was clearly contracted, which proved that the composite carbon fiber material can be used for electrical stimulation of biological tissues.

[0052] 9. Biocompatibility Characterization of Composite Carbon Fiber Materials Healthy adult C57 mice were selected, anesthetized, and prepared. A subcutaneous incision was made near the midline of the abdomen, and the composite carbon fiber material prepared in Example 2 was implanted into the cavity after blunt dissection. The mice were then housed individually post-surgery. One month later, the wounds showed good healing with no visible redness, swelling, ulceration, or electrode exposure, and no significant decrease in mouse weight was observed. Peripheral blood samples were collected and tumor necrosis factor-α (TNF-α) levels were detected using ELISA.

[0053] The results are as follows Figure 10 As shown, the TNF-α level in mice implanted with the composite carbon fiber material prepared in Example 2 was slightly higher than that in healthy mice, but significantly lower than that in mice implanted with activated carbon fiber. This verifies that coating activated carbon fiber with conductive polymer can significantly reduce the chronic inflammatory response induced by the implant, confirming that the conductive polymer shell has an effect on improving biocompatibility.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite carbon fiber material, characterized in that, Includes the following steps: Activated carbon fibers are obtained by sequentially cleaning and heat-treating for oxidation. A layer of conductive polymer is deposited on the activated carbon fibers by electrochemical deposition, followed by washing and drying to obtain composite carbon fiber material.

2. The method for preparing the composite carbon fiber material according to claim 1, characterized in that, The heat treatment temperature is 350℃~450℃, and the heat treatment time is 10min~2h.

3. The method for preparing the composite carbon fiber material according to claim 1, characterized in that, The electrochemical deposition method involves placing activated carbon fibers in a conductive polymer electroplating solution for electrochemical deposition.

4. The method for preparing the composite carbon fiber material according to claim 3, characterized in that, The conductive polymer electroplating solution includes conductive polymer monomers and solvents. The conductive polymers include one or more of poly(ethylene thiophene), polypyrrole, or polyaniline.

5. The method for preparing the composite carbon fiber material according to claim 1, characterized in that, Electrochemical deposition was performed using a chronopotentiometric method with the following parameters: deposition voltage of 1.1V to 1.2V; deposition time of 100s to 1000s.

6. The method for preparing the composite carbon fiber material according to claim 1, characterized in that, Electrochemical deposition was performed using cyclic voltammetry with the following parameters: lower limit potential of -0.5V to -0.2V, upper limit potential of 1.0V to 1.5V, and 2 to 10 cycles.

7. The method for preparing the composite carbon fiber material according to claim 1, characterized in that, Drying is carried out at 80℃~100℃ for 30 minutes.

8. A method for preparing composite carbon fiber material according to any one of claims 1-7.

9. The application of a composite carbon fiber material prepared by a method according to any one of claims 1-7 as a bioelectrode.

10. The application of a method for preparing composite carbon fiber material as described in any one of claims 1-7 in wearable electronic devices.

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