A preparation method and processing device of high-strength conductive hydrogel fiber

Abstract

The present invention discloses a method for preparing high-strength conductive hydrogel fibers and a processing device thereof, which have the advantages of being simple, convenient, efficient, safe, quick and easy to shape, and low in price, and can be applied to the production of various hydrogel flexible sensors. The present invention adopts PVA (polyvinyl alcohol) and CNT (carbon nanotube) powders as the main raw materials, mixes PVA and CS / CNT (chitosan / carbon nanotube) solution, and prepares a hydrogel solution through pretreatment such as centrifugation and freeze-thaw. Based on an extrusion-type 3D printing device, the molding of the high-strength conductive hydrogel fibers is controlled, and the hydrogel fibers can be woven into different structures. The high-strength conductive hydrogel fibers provided by the present invention can be used as flexible strain sensors, applied to human physiological signal detection, or applied to biocompatibility sensors, and have broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible materials, and in particular relates to a preparation method of high-strength conductive hydrogel fibers and a processing device thereof. Background Art

[0002] Hydrogels, as soft, wet materials, show great potential for applications in tissue engineering, energy storage devices, and flexible electronics. Hydrogels are 3D polymer networks that swell in water. While these polymer networks appear solid, the aqueous phase of the hydrogel allows for rapid diffusion of carriers, demonstrating their liquid-like transport properties. These favorable properties have led to the biocompatibility and flexibility of many hydrogels. Limited by mold processing methods, traditional hydrogels are often formed as three-dimensional bulk gels or two-dimensional thin films, resulting in poor mechanical properties and electrical conductivity, making them unable to meet the growing demand for applications. If conductive hydrogels can be fabricated into one-dimensional fibers with ordered polymer chains, the resulting high-strength conductive hydrogel fibers would exhibit significantly enhanced mechanical properties and electrical conductivity compared to conventional conductive hydrogel films and monolithic materials. However, due to the poor spinnability of current conductive hydrogels or their precursor solutions, long fibers are rarely spun. Therefore, high-strength conductive hydrogel fibers with excellent mechanical properties and electrical conductivity are crucial for the development of stretchable electronics. Summary of the Invention

[0003] In order to solve the above problems, embodiments of the present invention provide a method for preparing high-strength conductive hydrogel fibers and a processing device thereof.

[0004] The processing device of high-strength conductive hydrogel fiber of an embodiment of the present invention includes a gantry, on which a 3D printing mobile platform and a continuously variable speed roller are installed. The continuously variable speed roller is located below the 3D printing mobile platform. The 3D printing mobile platform reciprocates on the cantilever beam of the gantry along the length direction of the cantilever beam. The bottom of the 3D printing mobile platform is connected to a pneumatic extrusion nozzle, and the bottom of the pneumatic extrusion nozzle is in contact with the continuously variable speed roller. The 3D printing mobile platform, the pneumatic extrusion nozzle and the continuously variable speed roller are all connected to a computer control system.

[0005] Optionally, the pneumatic extrusion nozzle includes a pressure loading device, a body and a nozzle, the pressure loading device is connected to the body, the gel material is stored in the body, the nozzle is located below the body, and the nozzle is in contact with the stepless speed change roller.

[0006] Optionally, the pressure loading device is an air compressor, a pneumatic cylinder, an air storage tank or a pressure regulator.

[0007] Optionally, the surface of the continuously variable speed roller is covered with a release film.

[0008] The method for preparing high-strength conductive hydrogel fibers of the present invention uses the processing device for high-strength conductive hydrogel fibers of an embodiment of the present invention, and the preparation method includes the following steps:

[0009] S1. Take 100 ml of carbon nanotube (CNT) aqueous solution and place it into a centrifuge for high-speed centrifugation. Pour out the upper liquid after centrifugation.

[0010] S2. The precipitate in the centrifuge tube was placed in an oven at 100°C and dried for three hours to obtain carbon nanotube powder;

[0011] S3. Take 10 mg of carbon nanotube powder and stir and dissolve it in deionized water. Ultrasonication was performed for 2 hours to obtain a 1 wt% carbon nanotube aqueous solution until the carbon nanotubes were completely dispersed.

[0012] S4. An alkaline carbon nanotube aqueous solution was prepared by mixing an aqueous solution of carbon nanotubes, LiOH·H2O, KOH, and urea in a ratio of 8:0.4:0.6:0.7. The alkaline solution was placed in a refrigerator after configuration;

[0013] S5. Add 0.6 g of chitosan powder to the pre-cooled alkaline solution, stir for 10 minutes, and freeze until completely frozen;

[0014] S6. After the solution was thawed at room temperature, it was stirred with a magnetic stirrer for 10 minutes to obtain a uniform solution. The chitosan alkaline solution was frozen and thawed at low temperature (-20°C) for three cycles to obtain a chitosan aqueous solution;

[0015] S7. 8 g of polyvinyl alcohol (PVA) powder was immersed in a mixture of deionized water and glycerol at a ratio of 8:3, allowed to swell at room temperature for 30 minutes, then heated to 90°C in a water bath and stirred continuously for 3 hours until completely dissolved.

[0016] S8. After turning off the heating, cool to room temperature and use, the PVA concentration is 15% wt;

[0017] S9. Thoroughly mix the CS / CNT (chitosan / carbon nanotube) solution with the PVA solution restored to room temperature at a CS / PVA mass ratio of 1:2, and centrifuge at 1000 rpm to remove bubbles.

[0018] S10. Transfer the resulting solution to a centrifuge tube for storage, and then transfer to a -20°C freezer for 30 min.

[0019] S11. The centrifuge tube containing the solution was removed, the solution was thawed at room temperature and injected into the pneumatic extrusion nozzle body. The pneumatic extrusion nozzle body was transferred to the top of the stepless speed roller. The nozzle of the pneumatic extrusion nozzle device was connected to the nozzle and the black hydrogel fiber was extruded to obtain preformed PVA-CS-CNT (polyvinyl alcohol-chitosan-carbon nanotube) hydrogel fibers;

[0020] S12. The preformed PVA-CS-CNT hydrogel fibers were transferred to a -20°C environment and frozen for 2 hours to obtain PVA-CS-CNT hydrogel fibers.

[0021] The content of deionized water in step S3 is 10 ml.

[0022] In step S4, the refrigerator temperature is -5°C and the refrigeration time is 10 minutes.

[0023] The high-strength conductive hydrogel fiber of the present invention is produced by the high-strength conductive hydrogel fiber preparation method of the embodiment of the present invention, and comprises: water, carbon nanotubes, LiOH·H2O, KOH, urea, chitosan, glycerol and polyvinyl alcohol.

[0024] Application of the high-strength conductive hydrogel fiber according to the embodiment of the present invention in the field of strain sensors.

[0025] The beneficial effect of the embodiments of the present invention is that the present invention discloses a method for preparing high-strength conductive hydrogel fibers and a processing device thereof, which has the advantages of being simple, convenient, efficient, safe, quick and easy to shape, and low in price, and can be applied to the production of various hydrogel flexible sensors. The present invention adopts PVA (polyvinyl alcohol) and CNT (carbon nanotube) powders as the main raw materials, mixes PVA and CS / CNT (chitosan / carbon nanotube) solution, and prepares a hydrogel solution through pretreatment such as centrifugation and freeze-thaw. Based on an extrusion-type 3D printing device, the molding of the high-strength conductive hydrogel fibers is controlled, and the hydrogel fibers can be woven into different structures. The high-strength conductive hydrogel fibers provided by the present invention can be used as flexible strain sensors, applied to human physiological signal detection, or applied to biocompatibility sensors, and have broad application prospects.

[0026] Compared with the prior art, the present application adds a freezing treatment process, which can improve the mechanical properties of the hydrogel material. Freeze-thaw cross-linking is a simple and effective method. The principle of freeze-thaw cross-linking is to utilize the crystal structure formed by PVA at low temperatures, and through the thermodynamic changes of the crystals during the thawing process, a cross-linked structure is formed between PVA molecules. When the PVA solution is frozen at low temperatures, water molecules will form ice crystals, and PVA molecules will form a network structure between the ice crystals. As the thawing process proceeds, the ice crystals gradually melt, and the cross-linked structure between the PVA molecules gradually forms. Ultimately, the PVA molecules in the PVA solution form a cross-linked network, thereby improving its mechanical properties and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the high-strength conductive hydrogel fiber processing device of the present invention, wherein 1-hydrogel pneumatic extrusion nozzle, 2-3D printing mobile platform, 3-gantry, 4-stepless speed-changing roller.

[0028] Figure 2 Schematic diagram of the hydrogel pneumatic extrusion nozzle in the present invention.

[0029] Figure 3 This is a macroscopic image of a single high-strength hydrogel fiber prepared in the present invention.

[0030] Figure 4 This is a macroscopic image of the finished high-strength hydrogel fiber prepared according to the present invention.

[0031] Figure 5 This is the microscopic imaging of the high-strength hydrogel fiber prepared in the present invention in SEM.

[0032] Figure 6 This is the stress-strain curve of the high-strength hydrogel fiber containing 15% polyvinyl alcohol prepared in the present invention.

[0033] Figure 7 The stress-strain curves of the high-strength hydrogel fibers containing different percentages of polyvinyl alcohol prepared by the present invention;

[0034] Figure 8 This is the strain-stress curve of the high-strength hydrogel fiber network prepared in the present invention.

[0035] Figure 9 500 stretching and releasing strain cycles of the high-strength hydrogel fiber network prepared by the present invention. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0037] like Figures 1-9 As shown, the method for preparing high-strength conductive hydrogel fibers of the present invention comprises the following steps:

[0038] S1. Take 100 ml of carbon nanotube aqueous solution and centrifuge it at high speed. Pour out the upper liquid after centrifugation.

[0039] S2. The precipitate in the centrifuge tube was placed in an oven at 100°C and dried for three hours to obtain carbon nanotube powder;

[0040] S3. Take 10 mg of carbon nanotube powder and stir and dissolve it in 10 ml of deionized water. Ultrasonication was performed for 2 hours to obtain a 1 wt% aqueous solution of carbon nanotubes until the carbon nanotubes were completely dispersed.

[0041] S4. An alkaline carbon nanotube aqueous solution was prepared by mixing a carbon nanotube aqueous solution, LiOH·H2O, KOH, and urea in a ratio of 8:0.4:0.6:0.7. The alkaline solution was refrigerated at -5°C for 10 minutes.

[0042] S5. Add 0.6 g of chitosan powder to the pre-cooled alkaline solution, stir for 10 minutes, and freeze until completely frozen;

[0043] S6. After the solution was thawed at room temperature, it was stirred with a magnetic stirrer for 10 minutes to obtain a uniform solution, and after three cycles of freezing and thawing at -20°C, a chitosan aqueous solution was obtained;

[0044] S7. 8 g of polyvinyl alcohol powder was immersed in a mixed solvent of deionized water and glycerol in a ratio of 8:3, and expanded at room temperature for 30 minutes, then heated to 90 ° C in a water bath and stirred continuously for 3 hours until completely dissolved;

[0045] S8. After turning off the heating, cool to room temperature and use, the PVA concentration is 15% wt;

[0046] S9. Thoroughly mix the CS / CNT solution with the PVA solution that has been returned to room temperature at a CS / PVA mass ratio of 1:2, and centrifuge at 1000 rpm to remove bubbles.

[0047] S10. Transfer the resulting solution to a centrifuge tube for storage, and then transfer to a -20°C freezer for 30 min.

[0048] S11. The centrifuge tube containing the solution was removed, the solution was thawed at room temperature and injected into the pneumatic extrusion nozzle body. The pneumatic extrusion nozzle body was transferred to the top of the stepless speed roller. The nozzle of the pneumatic extrusion nozzle device was connected to the nozzle and the black hydrogel fiber was extruded to obtain a preformed PVA-CS-CNT hydrogel fiber.

[0049] S12. The preformed PVA-CS-CNT hydrogel fibers were transferred to a -20°C environment and frozen for 2 hours to obtain PVA-CS-CNT hydrogel fibers.

[0050] Principle: The order in which raw materials are added affects the mechanical properties of the prepared hydrogel fibers. This is achieved by adding them in stages to improve the material's mechanical properties. The main explanation is as follows: chitosan serves as the brittle first network of the double-network gel, while PVA serves as the tougher second network.

[0051] After adding carbon nanotube powder to deionized water and ultrasonically dissolving and dispersing it, the carbon nanotube powder is dissolved in an alkaline solution. The carbon nanotube powder is added later to prevent heat generated when the alkaline substance dissolves, which may cause carbon nanotube aggregation and affect the conductive properties. Chitosan is dissolved in the above-prepared alkaline aqueous solution of carbon nanotubes to obtain a chitosan alkaline solution of corresponding concentration. The chitosan alkaline solution (5wt%) is frozen and thawed three times at a low temperature (-20°C). The dynamic equilibrium of the hydrogen bonds between the chitosan chains is destroyed, forming a chitosan primary network.

[0052] Then, a second PVA network is introduced through a freeze-thaw process. At low temperatures, the PVA molecular chains form crystalline regions and interact with the chitosan chains to form stable hydrogen bonds, resulting in a chitosan-PVA hydrogel.

[0053] In summary, during the preparation process, if chitosan powder is added first and dissolved in a deionized water solution, or if chitosan powder is added first and dissolved in an alkaline deionized water solution before adding carbon nanotube powder, the dispersibility of the carbon nanotubes will be affected, causing the carbon nanotubes to aggregate and not be well dispersed in the solution, affecting their conductivity. The prepared alkaline chitosan aqueous solution must be repeatedly frozen and thawed at low temperatures to promote the first layer of the chitosan solution network, which is conducive to the physical cross-linking of PVA and chitosan. Therefore, changing the order of the above steps will lead to a decrease in the mechanical and conductive properties of the hydrogel fiber.

[0054] like Figure 1-Figure 2 As shown, the processing device of high-strength conductive hydrogel fiber of an embodiment of the present invention includes a gantry 3, on which a 3D printing mobile platform 2 and a continuously variable speed roller 4 are installed. The continuously variable speed roller 4 is located below the 3D printing mobile platform 2. The 3D printing mobile platform 2 reciprocates on the cantilever beam of the gantry 3 along the length direction of the cantilever beam. The bottom of the 3D printing mobile platform 2 is connected to a pneumatic extrusion nozzle 1, and the bottom of the pneumatic extrusion nozzle 1 is in contact with the continuously variable speed roller 4. The 3D printing mobile platform 2, the pneumatic extrusion nozzle 1 and the continuously variable speed roller 4 are all connected to a computer control system.

[0055] The pneumatic extrusion nozzle 1 includes a pressure loading device, a body and a nozzle. The pressure loading device is connected to the body. The gel material is stored in the body. The nozzle is located below the body and contacts the stepless speed-changing roller.

[0056] Optionally, the pressure loading device is an air compressor, a pneumatic cylinder, an air storage tank or a pressure regulator.

[0057] The gel material in the body is squeezed by a pressure loading device, so that the gel material stored in the body is squeezed out from a nozzle and attached to an infinitely variable speed roller to obtain high-strength conductive hydrogel fibers.

[0058] The computer control system adjusts the rotation speed of the infinitely variable speed drum and the movement speed of the pneumatic extrusion nozzle to achieve controllable printing of extruded gel fibers. By controlling the speed ratio of the two, standard network or filamentous stacked structures of different shapes and sizes can be printed.

[0059] like Figure 6 As shown, the hydrogel fiber described in this article, which is prepared by adding 15% PVA, has an elongation at break of 387%. It can be seen that the hydrogel fiber has very good tensile properties.

[0060] Figure 7 、 Figure 8 The figure shows the tensile and cyclic release strain of a single hydrogel fiber and its textile under different tensile forces, indicating that the hydrogel fiber has good elasticity and after being woven into a hydrogel fabric, its maximum breaking stress is significantly improved compared to that of a single hydrogel, and the degree of elastic deformation is also improved to a certain extent.

[0061] Figure 9 The figure shows the change in relative resistance of the hydrogel braid during cyclic stretching. This indicates that the relative resistance of the hydrogel braid changes periodically under varying tensile forces. Therefore, the hydrogel braid described in this article has great potential for monitoring human physiological activity.

[0062] Although the above embodiments have been shown and described, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those skilled in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength conductive hydrogel fiber, characterized in that: The high-strength conductive hydrogel fiber is prepared using a processing device, which includes a 3D printing mobile platform, the bottom of which is connected to a pneumatic extrusion nozzle, and the bottom of the pneumatic extrusion nozzle is in contact with an infinitely variable speed roller. The preparation method includes the following steps: S1. Take 100 ml of carbon nanotube aqueous solution and centrifuge it at high speed. Pour out the upper liquid after centrifugation. S2. The precipitate in the centrifuge tube was placed in an oven at 100°C and dried for three hours to obtain carbon nanotube powder; S3. Take 10 mg of carbon nanotube powder and stir and dissolve it in deionized water. Ultrasonication was performed for 2 hours to obtain a 1 wt% carbon nanotube aqueous solution until the carbon nanotubes were completely dispersed. S4. An alkaline carbon nanotube aqueous solution was prepared by mixing an aqueous solution of carbon nanotubes, LiOH·H2O, KOH, and urea in a certain proportion, and the alkaline solution was placed in a refrigerator after configuration; S5. Add 0.6 g of chitosan powder to the pre-cooled alkaline solution, stir for 10 minutes, and freeze until completely frozen; S6. After the solution was thawed at room temperature, it was stirred with a magnetic stirrer for 10 minutes to obtain a uniform solution. After three cycles of freezing and thawing the chitosan alkaline solution at low temperature, an aqueous chitosan solution was obtained; S7. 8 g of polyvinyl alcohol powder was immersed in a mixed solvent of deionized water and glycerol, expanded at room temperature for 30 minutes, then heated to 90 ° C in a water bath and stirred continuously for 3 hours until completely dissolved; S8. After turning off the heating, cool to room temperature and use, the PVA concentration is 15% wt; S9. Thoroughly mix the CS / CNT solution with the PVA solution that has been returned to room temperature at a CS:PVA mass ratio of 1:2 and centrifuge at 1000 rpm to remove bubbles. S10. Transfer the resulting solution to a centrifuge tube for storage, and then transfer to a -20°C freezer for 30 min. S11. The centrifuge tube containing the solution was removed, the solution was thawed at room temperature and injected into the pneumatic extrusion nozzle body. The pneumatic extrusion nozzle body was transferred to the top of the stepless speed roller. The nozzle of the pneumatic extrusion nozzle device was connected to the nozzle and the black hydrogel fiber was extruded to obtain a preformed PVA-CS-CNT hydrogel fiber. S12. The preformed PVA-CS-CNT hydrogel fibers were transferred to a -20°C environment and frozen for 2 hours to obtain PVA-CS-CNT hydrogel fibers.

2. The method for preparing high-strength conductive hydrogel fiber according to claim 1, characterized in that: The content of deionized water in step S3 is 10 ml.

3. The method for preparing high-strength conductive hydrogel fiber according to claim 1, characterized in that: In step S4, the refrigerator temperature is -5°C and the refrigeration time is 10 minutes.

4. A processing device for high-strength conductive hydrogel fibers, characterized in that: It is used to implement the method for preparing high-strength conductive hydrogel fibers as described in claim 1, comprising a gantry, a 3D printing mobile platform and a continuously variable speed roller installed on the gantry, the continuously variable speed roller being located below the 3D printing mobile platform, the 3D printing mobile platform reciprocating on the cantilever beam of the gantry along the length direction of the cantilever beam, the bottom of the 3D printing mobile platform is connected to a pneumatic extrusion nozzle, the bottom of the pneumatic extrusion nozzle is in contact with the continuously variable speed roller, and the 3D printing mobile platform, the pneumatic extrusion nozzle and the continuously variable speed roller are all connected to a computer control system.

5. The processing device for high-strength conductive hydrogel fiber according to claim 4, characterized in that: The pneumatic extrusion nozzle includes a pressure loading device, a body and a nozzle. The pressure loading device is connected to the body. The body stores gel material. The nozzle is located below the body and contacts the stepless speed-changing roller.

6. The processing device for high-strength conductive hydrogel fiber according to claim 5, characterized in that: The pressure loading device is an air compressor, a pneumatic cylinder, an air storage tank or a pressure regulator.

7. The processing device for high-strength conductive hydrogel fibers according to claim 4, characterized in that: The surface of the continuously variable speed roller is covered with a release film.

8. A high-strength conductive hydrogel fiber, characterized in that: The high-strength conductive hydrogel fiber is prepared by the preparation method of claim 1, and the components of the high-strength conductive hydrogel fiber include: water, carbon nanotubes, LiOH·H2O, KOH, urea, chitosan, glycerol and polyvinyl alcohol.

9. Use of the high-strength conductive hydrogel fiber according to claim 8 in the field of strain sensors.

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