Coaxial electrospun polyurethane / graphene conductive fibers, preparation and applications

Abstract

The application provides coaxial electrospinning polyurethane / graphene conductive fiber, preparation and application, which is prepared by coaxial electrospinning to obtain porous PU / PDA / rGO coaxial nanofiber with polyurethane (PU) as a skin layer and graphene oxide (GO) as a core layer; the reactivity of dopamine (DA) is used to make DA in-situ polymerize during coaxial electrospinning and vacuum drying, simultaneously generate reduced graphene oxide (rGO) and make it adhere to the PU surface, and then improve the excessive aggregation of rGO in the conventional loading process and the falling off in the use process. In order to improve the polymerization rate of DA in N,N-dimethylformamide (DMF), triethylamine is added to capture H + generated by dopamine polymerization and promote dopamine polymerization. The PU / PDA / rGO coaxial nanofiber prepared in the application has the advantages of good rGO dispersity, strong interface adhesion with the skin layer, simple skin layer thickness and pore regulation, good conductive performance and the like, and can be used for the development of flexible pressure sensors.

Description

Technical Field

[0001] This invention relates to the field of conductive fiber preparation technology, and particularly to coaxial electrospun polyurethane / graphene conductive fibers, their preparation and application. Background Technology

[0002] Due to the wide application of smart textiles in the textile market, conductive fibers with excellent conductivity, antistatic properties, and flexibility have broad application prospects. In the field of flexible conductive fibers (sensor fabrics), spandex has attracted much attention due to its excellent elastic properties. Currently, existing methods for preparing polyurethane-based conductive fibers typically involve blending conductive particles with polyurethane and spinning or immobilizing them on the surface of polyurethane fibers. These methods suffer from problems such as the conductive filler being encapsulated and blocked by the matrix material or having poor dispersion, and the conductive coating easily peeling off, affecting the service life of the conductive fibers.

[0003] Thanks to the large specific surface area of ​​coaxial electrospun fibers, in-situ synchronous immobilization of graphene on the surface of polyurethane electrospun fibers holds promise for preparing high-performance flexible pressure sensing fibers with good conductive particle dispersion. However, the polyurethane and graphene are only bonded by hydrogen bonds, making them prone to delamination. Furthermore, the uneven size of the pores on the fiber surface leads to uneven resistance changes during pressure sensing tests due to variations in pore spacing, thus affecting the sensitivity of the conductive sensing fabric. Therefore, to address these issues, we propose a coaxial electrospun polyurethane / graphene conductive fiber, its preparation, and its application, which can improve the conductivity, sensitivity, and lifespan of conductive sensing fabrics. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose coaxial electrospun polyurethane / graphene conductive fibers, their preparation and application. The preparation method is simple and can improve the sensitivity, conductivity and service life of conductive sensing fabrics, effectively solving the technical problems in the background art.

[0005] Technical Effects: This invention provides coaxial electrospun polyurethane / graphene conductive fibers, their preparation, and applications. Porous PU / PDA / rGO coaxial nanofibers with a polyurethane (PU) skin and graphene oxide (GO) core are prepared using coaxial electrospinning. It utilizes the reactivity of dopamine (DA) to polymerize DA in situ during coaxial electrospinning and vacuum drying, simultaneously reducing it to generate reduced graphene oxide (rGO), which then adheres to the PU surface. This improves the excessive aggregation of rGO during conventional loading processes and reduces its shedding during use. To increase the polymerization rate of DA in N,N-dimethylformamide (DMF), triethylamine is added to capture the H+ generated during dopamine polymerization. +This promotes dopamine polymerization. Regulating the porosity of the skin structure is beneficial for significantly increasing the specific surface area, optimizing the conductive mesh, and increasing the sensitivity for sensing. The higher the pore density, the larger the contact angle of the corresponding fiber, which is beneficial for improving the hydrophobicity of the nanofiber, thereby expanding the application range and service life of conductive fibers.

[0006] The further defined technical solution of this invention is: a method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion, comprising the following steps:

[0007] S1, dissolve PU in DMF to obtain a skin spinning solution;

[0008] S2, Dissolve DA in DMF to obtain a solution; and uniformly disperse GO in the solution, add tris(hydroxymethyl)aminomethane buffer and triethylamine to obtain the core spinning solution;

[0009] S3. Using a syringe, take the skin spinning solution obtained in step S1 and the core spinning solution obtained in step S2 respectively, connect them to the coaxial spinning needle, place them in an electrospinning device for electrospinning, and vacuum dry them to obtain PU / PDA / rGO coaxial nanofibers.

[0010] S4. The PU / PDA / rGO coaxial nanofibers obtained in step S3 are immersed in a tetrahydrofuran / water blend solvent and subjected to ultrasonic homogenization to obtain porous PU / PDA / rGO coaxial nanofibers.

[0011] As a further improvement, this invention provides a method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion.

[0012] As a further improvement, this invention relates to the application of dopamine-adhesive coaxial electrospun polyurethane / graphene conductive fibers in flexible pressure sensors.

[0013] The beneficial effects of this invention are:

[0014] (1) In this invention, the coaxial electrospun polyurethane / graphene conductive fiber, its preparation and application are prepared by coaxial electrospinning with PU as the flexible skin and DA / GO as the core layer. The GO in the core layer is tightly bonded to the skin layer through PDA self-polymerization and is simultaneously reduced to rGO. The porous structure of the skin layer is formed by solubility difference and ultrasonic homogenization. The thickness and pore size of the skin layer are easy to control. In this way, the in-situ polymerization of biomimetic binder PDA and the in-situ reduction and dispersion of rGO are realized, which improves the bonding force between the skin layer fiber and the core layer conductive particles rGO.

[0015] (2) The coaxial electrospun polyurethane / graphene conductive fibers prepared by this invention, their preparation and application are as follows: PU is dissolved in DMF to obtain a skin spinning solution. DA is dissolved in DMF to obtain solution 1, and GO is uniformly dispersed in solution 1. Tris buffer and triethylamine are then added to adjust the pH to 8.5 to obtain a core spinning solution. By adjusting the amounts of Tris and triethylamine, the self-polymerization control of dopamine in the coaxial electrospinning and subsequent drying processes is achieved. The core spinning solution and skin spinning solution are respectively taken with a syringe, connected to a coaxial spinning needle, and placed on a coaxial electrospinning device for electrospinning. The product is collected, vacuum dried, and PU / PDA / rGO coaxial nanofibers are obtained. The PU / PDA / rGO coaxial nanofibers are immersed in a tetrahydrofuran / water mixed solvent and, with the aid of ultrasonic homogenization, the pore size and porosity of the PU skin are controlled, thereby optimizing the conductive fiber network. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the preparation method of coaxial electrospun polyurethane / graphene conductive fibers in this invention.

[0018] Figure 2 This is a physical image of the coaxial electrospun polyurethane / graphene conductive fiber of Example 1 in this invention. Detailed Implementation

[0019] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. 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. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. 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.

[0020] The coaxial electrospun polyurethane / graphene conductive fiber, its preparation, and its application provided in this invention are porous PU / PDA / rGO coaxial nanofibers prepared by coaxial electrospinning, with PU as the flexible skin and DA / GO as the core layer. The porous structure of the flexible skin layer is formed synergistically through solubility differences and ultrasonic homogenization. The GO in the core layer is tightly bound to the skin layer through PDA self-polymerization and is simultaneously reduced to rGO.

[0021] This invention provides a method for preparing coaxial electrospun polyurethane / graphene conductive fibers, comprising the following steps:

[0022] S1, dissolve PU in DMF to obtain the skin spinning solution;

[0023] As a preferred method, the specific preparation method of the skin spinning solution in step S1 is to dissolve PU in DMF, stir continuously at 20-50℃ for 2-12 hours, and then use it for ultrasonic defoaming.

[0024] As a further preferred option, the ratio of PU to DMF is 1-10g:100mL, which is conducive to the full reaction of the two.

[0025] S2, dissolve DA completely in DMF, then add GO and disperse it evenly in the DA / DMF solution, add Tris buffer and triethylamine to obtain the core spinning solution;

[0026] Preferably, Tris buffer is added to adjust the pH of the core spinning solution to 8.0-9.0, and triethylamine is added to promote the polymerization of DA during the spinning process and the vacuum drying process after spinning.

[0027] Preferably, the ratio of GO to PU is 1-10:100, and this ratio control is beneficial for GO to form a better conductive network in PU and to have better dispersion.

[0028] Preferably, the ratio of DA to DMF is 0.5-2.0 g: 100 mL, and the ratio of GO to DMF is 0.05-2.0 g: 100 mL. Controlling these ratios is beneficial for DA to dissolve completely in DMF, and controlling the ratio of GO to DMF is beneficial for GO to be uniformly dispersed in the DA / DMF solution, allowing for a full reaction and preventing side reactions.

[0029] Preferably, the ratio of triethylamine to DA is 0.5-2:10. This ratio control is beneficial for DA to capture the H+ generated during the self-polymerization process of DA in anhydrous organic solvents. + This promotes the full progress of polymerization and the reduction reaction of GO.

[0030] S3. Using a syringe, take the skin spinning solution obtained in step S1 and the core spinning solution obtained in step S2 and connect them to the coaxial spinning needle. Place them on an electrospinning device for electrospinning and vacuum drying to obtain PU / PDA / rGO coaxial nanofibers.

[0031] Preferred conditions for coaxial electrospinning are as follows: the flow rate of the sheath spinning solution is 1.0-4.0 mL / h, the flow rate of the core spinning solution is 0.1-1.0 mL / h, the distance between the receiving plate and the spinneret is 10-15 cm, the static voltage is 10-18 kV, the temperature is 15-35℃, and the ambient humidity is 60±5%.

[0032] As a further preferred embodiment, the syringe has a specification of 5 mL, a coaxial electrospun inner needle inner diameter of 0.34 mm, and an outer needle inner diameter of 1.12 mm.

[0033] Preferably, the vacuum drying conditions are: drying in a vacuum drying oven at 30-50℃ for 12-18 hours.

[0034] S4. The PU / PDA / rGO coaxial nanofibers obtained in step S3 are immersed in a tetrahydrofuran / water blend solvent and then ultrasonically homogenized to obtain porous PU / PDA / rGO coaxial nanofibers.

[0035] As a further improvement, the volume ratio of tetrahydrofuran / water blended solvent is 1-5:5, the soaking temperature is 10-30℃, and the soaking time is greater than or equal to 2h; by adjusting the blended solvent ratio and coordinating with ultrasonic homogenization, the porosity of the PU skin layer is controlled to 70-80%, thereby optimizing the porous PU / PDA / rGO nanofibers.

[0036] The application of coaxial electrospun polyurethane / graphene conductive fibers in flexible pressure sensors provided in this embodiment of the invention.

[0037] Example 1:

[0038] Methods for preparing coaxial electrospun polyurethane / graphene conductive fibers, such as... Figure 1 As shown, the specific steps are as follows:

[0039] (1) Preparation of skin spinning solution: Dissolve 5g of polyurethane in 100mL of dimethylformamide, stir continuously at 35℃ for 6h, and defoam by ultrasonication to obtain skin spinning solution.

[0040] (2) Preparation of core spinning solution: Dissolve 0.5g of dopamine in 100mL of dimethylformamide, then add 0.1g of graphene oxide and disperse it evenly in the dopamine / dimethylformamide solution. Add tris(hydroxymethyl)aminomethane buffer dropwise to adjust the pH of the core spinning solution to 8.5. Add 0.05g of triethylamine to promote the polymerization of dopamine during spinning and vacuum drying after spinning. Mix thoroughly and set aside to obtain the core spinning solution.

[0041] (3) Coaxial electrospinning: Core spinning solution and sheath spinning solution were taken separately using a 5mL syringe. The flow rate of the sheath spinning solution was 3.0mL / h, and the flow rate of the core spinning solution was 1.0mL / h. These solutions were connected to a coaxial electrospinning needle with an inner needle diameter of 0.34mm and an outer needle diameter of 1.12mm. After electrospinning and product collection, the product was vacuum dried for 16h to obtain PU / PDA / rGO coaxial nanofibers.

[0042] (4) Control of pore structure: The PU / PDA / rGO coaxial nanofibers obtained in step (3) above were immersed in a tetrahydrofuran / water blend solvent ((4 / 5), v / v) at a temperature of 10℃ for 3 hours to obtain porous PU / PDA / rGO coaxial nanofibers, as detailed below. Figure 2 .

[0043] Example 2

[0044] Methods for preparing coaxial electrospun polyurethane / graphene conductive fibers, such as... Figure 1 As shown, the specific steps are as follows:

[0045] (1) Preparation of skin spinning solution: Dissolve 5g of polyurethane in 100mL of dimethylformamide, stir continuously at 35℃ for 6h, and use it for ultrasonic defoaming to obtain skin spinning solution.

[0046] (2) Preparation of core spinning solution: Dissolve 0.5g of dopamine in 100mL of dimethylformamide, then add 0.5g of graphene oxide and disperse it evenly in the dopamine / dimethylformamide solution. Add tris(hydroxymethyl)aminomethane buffer dropwise to adjust the pH of the core spinning solution to 8.5. Add 0.05g of triethylamine to promote the polymerization of dopamine during the spinning process and the vacuum drying process after spinning. Mix thoroughly and set aside to obtain the core spinning solution.

[0047] (3) Coaxial electrospinning: The core spinning solution and the sheath spinning solution were taken separately using a 5mL syringe, with a flow rate of 3.0mL / h for the sheath spinning solution and 1.0mL / h for the core spinning solution. These were connected to a coaxial electrospinning needle with an inner needle diameter of 0.34mm and an outer needle diameter of 1.12mm. After electrospinning and product collection, the PU / PDA / rGO coaxial nanofibers were obtained by vacuum drying.

[0048] (4) Control of pore structure: The PU / PDA / rGO coaxial nanofibers obtained in step (3) above were immersed in a tetrahydrofuran / water blend solvent ((4 / 5), v / v) at a temperature of 150°C for 23 hours to obtain porous PU / PDA / rGO coaxial nanofibers.

[0049] Example 3

[0050] Methods for preparing coaxial electrospun polyurethane / graphene conductive fibers, such as... Figure 1 As shown, the specific steps are as follows:

[0051] (1) Preparation of skin spinning solution: Dissolve 5g of polyurethane in 100mL of dimethylformamide, stir continuously at 35℃ for 6h, and use it for ultrasonic defoaming to obtain skin spinning solution.

[0052] (2) Preparation of core spinning solution: Dissolve 1g of dopamine in 100mL of dimethylformamide, then add 0.5g of graphene oxide and disperse it evenly in the dopamine / dimethylformamide solution. Add tris(hydroxymethyl)aminomethane buffer dropwise to adjust the pH of the core spinning solution to 8.5. Add 0.05g of triethylamine to promote the polymerization of dopamine during the spinning process and the vacuum drying process after spinning. Mix thoroughly and set aside to obtain the core spinning solution.

[0053] (3) Coaxial electrospinning: The core spinning solution and the sheath spinning solution were taken separately using a 5mL syringe, with a flow rate of 3.0mL / h for the sheath spinning solution and 1.0mL / h for the core spinning solution. These were connected to a coaxial electrospinning needle with an inner needle diameter of 0.34mm and an outer needle diameter of 1.12mm. After electrospinning and product collection, the PU / PDA / rGO coaxial nanofibers were obtained by vacuum drying.

[0054] (4) Control of pore structure: The PU / PDA / rGO coaxial nanofibers obtained in step (3) above are immersed in a tetrahydrofuran / water blend solvent ((4 / 5), v / v) at a temperature of 10°C for 3 hours to obtain porous PU / PDA / rGO coaxial nanofibers.

[0055] Example 4

[0056] Methods for preparing coaxial electrospun polyurethane / graphene conductive fibers, such as... Figure 1 As shown, the specific steps are as follows:

[0057] (1) Preparation of skin spinning solution: Dissolve 5g of polyurethane in 100mL of dimethylformamide, stir continuously at 35℃ for 6h, and use it for ultrasonic defoaming to obtain skin spinning solution.

[0058] (2) Preparation of core spinning solution: Dissolve 1g of dopamine in 100mL of dimethylformamide, then add 0.5g of graphene oxide and disperse it evenly in the dopamine / dimethylformamide solution. Add tris(hydroxymethyl)aminomethane buffer dropwise to adjust the pH of the core spinning solution to 8.5. Add 0.1g of triethylamine to promote the polymerization of dopamine during the spinning process and the vacuum drying process after spinning. Mix thoroughly and set aside to obtain the core spinning solution.

[0059] (3) Coaxial electrospinning: The core spinning solution and the sheath spinning solution were taken separately using a 5mL syringe, with a flow rate of 3.0mL / h for the sheath spinning solution and 1.0mL / h for the core spinning solution. These were connected to a coaxial electrospinning needle with an inner needle diameter of 0.34mm and an outer needle diameter of 1.12mm. After electrospinning and product collection, the PU / PDA / rGO coaxial nanofibers were obtained by vacuum drying.

[0060] (4) Control of pore structure: The PU / PDA / rGO coaxial nanofibers obtained in step (3) above are immersed in a tetrahydrofuran / water blend solvent ((3 / 5), v / v) at a temperature of 10°C for 3 hours to obtain porous PU / PDA / rGO coaxial nanofibers.

[0061] Comparative Example 1

[0062] (1) Comparative Example 1 is a blank sample of pure PU electrospun coaxial nanofibers.

[0063] Comparative Example 2

[0064] The preparation method of PU / rGO coaxial nanofibers includes the following steps:

[0065] (1) Preparation of skin spinning solution: Dissolve 5g of polyurethane in 100mL of dimethylformamide, stir continuously at 35℃ for 6h, and use it for ultrasonic defoaming to obtain skin spinning solution.

[0066] (2) Preparation of core spinning solution: 0.5g of reduced graphene oxide was uniformly dispersed in dimethylformamide solution to obtain core spinning solution;

[0067] (3) Coaxial electrospinning: Core spinning solution and sheath spinning solution were taken separately using a 5mL syringe, with a flow rate of 3.0mL / h for the sheath spinning solution and 1.0mL / h for the core spinning solution. These were connected to a coaxial electrospinning needle with an inner needle diameter of 0.34mm and an outer needle diameter of 1.12mm. After electrospinning, product collection, and vacuum drying, PU / rGO coaxial nanofibers were obtained.

[0068] Comparative Example 3

[0069] The preparation method of PU / PDA / rGO coaxial nanofibers includes the following steps:

[0070] (1) Preparation of skin spinning solution: Dissolve 5g of polyurethane in 100mL of dimethylformamide, stir continuously at 35℃ for 6h, and use it for ultrasonic defoaming to obtain skin spinning solution.

[0071] (2) Preparation of core spinning solution: Dissolve 1g of dopamine in 100mL of dimethylformamide, then add 0.5g of graphene oxide and disperse it evenly in the dopamine / dimethylformamide solution. Add tris(hydroxymethyl)aminomethane buffer dropwise to adjust the pH of the core spinning solution to 8.5. Mix thoroughly and set aside to obtain the core spinning solution.

[0072] (3) Coaxial electrospinning: Core spinning solution and sheath spinning solution were taken separately using a 5mL syringe. The flow rate of the sheath spinning solution was 3.0mL / h, and the flow rate of the core spinning solution was 1.0mL / h. These solutions were connected to a coaxial electrospinning needle with an inner needle diameter of 0.34mm and an outer needle diameter of 1.12mm. After electrospinning and product collection, PU / PDA / rGO coaxial nanofibers were obtained by vacuum drying.

[0073] (4) Control of pore structure: The PU / PDA / rGO coaxial nanofibers obtained in step (3) above are immersed in a tetrahydrofuran / water blend solvent ((4 / 5), v / v) at a temperature of 10°C for 3 hours to obtain porous PU / PDA / rGO coaxial nanofibers.

[0074] Characterization:

[0075] (1) Mechanical property test: The coaxial nanofibers prepared in Examples 1, 2, 3, 4, Comparative Examples 1, 2 and 3 were cut into 1cm×5cm strips and placed on a universal electronic testing machine for tensile testing, wherein the tensile speed was 20mm / min.

[0076] (2) Porosity test: The coaxial nanofibers prepared in Examples 1, 2, 3, 4, Comparative Examples 1, 2, and 3 were freeze-dried, a certain mass was weighed, and they were soaked in ethanol for 1 hour. Then, the excess ethanol was removed with filter paper and weighed.

[0077] The formula for calculating porosity is as follows:

[0078]

[0079] In the formula, ω0(g) and V0(mL) correspond to the mass and volume of the fiber soaked in ethanol, respectively; ω1(g) is the mass of the fiber after soaking in ethanol; and ρ is the density of ethanol at 20℃ (0.7893 g / cm³). 3 ).

[0080] (3) Resistance test: The coaxial nanofibers prepared in Examples 1, 2, 3, 4, Comparative Examples 1, 2 and 3 were cut into nanofiber circular samples with a diameter of 12 cm and tested by a high resistance meter.

[0081] The characterization test data in Table 1 were obtained from the above characterization of Examples 1, 2, 3, 4, Comparative Examples 1, 2, and 3.

[0082] Table 1 Characterization Test Data

[0083]

[0084]

[0085] As can be seen from the characterization test data in Table 1 above, compared with Example 1, Comparative Example 1 and Comparative Example 2, it was found that when rGO was added to the coaxial nanofibers, the resistance value could be significantly reduced. However, Comparative Example 2 had problems such as poor interfacial adhesion. After 100 washes, the resistance increased, the conductivity decreased, and the elongation at break decreased. Furthermore, by comparing Example 1 and Example 2, it was found that when the amount of GO added was increased, the conductivity could be improved, and the mechanical properties could be improved to a certain extent, indicating that rGO could be well dispersed in the coaxial nanofibers.

[0086] Comparing Examples 2, 3, and 4 with Comparative Example 3, it was found that when the same amount of rGO was added to the coaxial nanofibers, the amount of dopamine needed to be increased accordingly. Therefore, it is necessary to synergistically increase the amounts of rGO and dopamine to ensure sufficient interfacial adhesion between rGO and PU; however, simultaneously increasing the amount of dopamine (DA) also requires a simultaneous increase in the amount of triethylamine to more effectively absorb the H2 produced during DA polymerization. + This ensures the reaction proceeds fully;

[0087] Comparing Examples 3 and 4, it was found that tetrahydrofuran is a good solvent for PU, while water is a poor solvent. Increasing the proportion of tetrahydrofuran in the mixed solvent is beneficial to increasing the porosity. Ultrasonic homogenization can further promote the homogenization of pores.

[0088] This invention utilizes a coaxial electrospinning method to prepare a polyurethane flexible skin layer and a dopamine / graphene oxide (rGO) conductive core layer. Taking advantage of dopamine's self-polymerization under alkaline conditions and its ability to reduce GO, coaxial electrospinning is employed to simultaneously disperse and adhere GO and generate rGO, resulting in a PU / PDA / rGO skin-core structure fiber. The porous structure of the skin layer is synergistically formed through solubility difference adjustment and ultrasonic homogenization. The prepared PU / PDA / rGO fibers exhibit advantages such as good rGO dispersibility, strong interfacial adhesion to the skin layer, simple control of skin layer thickness and porosity, and good conductivity, thus enabling their application in the development of flexible pressure sensors.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion, characterized in that, Includes the following steps: S1, dissolve PU in DMF to obtain a skin spinning solution; S2, Dissolve DA in DMF to obtain a solution; and uniformly disperse GO in the solution, add tris(hydroxymethyl)aminomethane buffer and triethylamine to obtain the core spinning solution; S3. Using a syringe, take the skin spinning solution obtained in step S1 and the core spinning solution obtained in step S2 and connect them to the coaxial spinning needle. Place them in an electrospinning device for electrospinning and vacuum drying to obtain PU / PDA / rGO coaxial nanofibers. S4. The PU / PDA / rGO coaxial nanofibers obtained in step S3 are immersed in a tetrahydrofuran / water blend solvent and subjected to ultrasonic homogenization to obtain porous PU / PDA / rGO coaxial nanofibers.

2. The method for preparing coaxial electrospun polyurethane / graphene fibers based on dopamine adhesion according to claim 1, characterized in that: The mass ratio of GO to PU in the porous PU / PDA / rGO coaxial nanofiber is 1-10:

100.

3. The method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion according to claim 1, characterized in that: In step S1, the ratio of PU to DMF is 1-10g:100mL.

4. The method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion according to claim 1, characterized in that: In step S2, the ratio of DA to DMF is 0.5-2.0g:100mL; the ratio of GO to DMF is 0.05-2.0g:100mL.

5. The method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion according to claim 1, characterized in that: In step S2, the tris(hydroxymethyl)aminomethane is added to adjust the pH to 8.0-9.0, and the mass ratio of triethylamine to DA is 0.5-2:

10.

6. The method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion according to claim 1, characterized in that: In step S3, the vacuum drying conditions for the PU / PDA / rGO coaxial nanofibers are: drying in a vacuum drying oven at 30-50℃ for 12-18 hours.

7. The method for preparing coaxial electrospun polyurethane / graphene conductive fibers based on dopamine adhesion according to claim 1, characterized in that: In step S4, the volume ratio of the tetrahydrofuran / water blend solvent is 1-5:5, and the soaking temperature is 10-30℃, with a soaking time of ≥2h.

8. A coaxial electrospun polyurethane / graphene conductive fiber based on dopamine adhesion, characterized in that: The dopamine-adhesive-based coaxial electrospun polyurethane / graphene conductive fiber is prepared by the preparation method described in any one of claims 1-7.

9. The application of the dopamine-adhesive-based coaxial electrospun polyurethane / graphene conductive fiber according to claim 8 in a flexible pressure sensor.

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