A nanofiber film fabric type flexible capacitive sensor and preparation method thereof

Abstract

The present invention provides a nanofiber film fabric-type flexible capacitive sensor and a preparation method thereof, wherein the preparation method comprises the steps of preparing polyvinylidene fluoride-ionic liquid nanofiber film, preparing polyvinylidene fluoride nanofiber film, preparing conductive polyvinylidene fluoride nanofiber film and preparing high-sensitivity low-resistance nanofiber film fabric-type flexible capacitive sensor. The present invention is based on the oriented polyvinylidene fluoride vinyl-based dielectric layer, electrode layer and packaging layer obtained by conjugate spinning, and achieves high mechanical strength while achieving good air permeability from a structural perspective, and establishes a fabric foundation of a flexible sensor composed entirely of polyvinylidene fluoride vinyl-based nanofiber film, and achieves the technical requirements of wearing comfort. The process of the present invention is characterized by high efficiency, convenience and repeatability, and the prepared fabric-type flexible capacitive sensor based on a high-sensitivity ion film takes into account high mechanical properties, high conductivity, high sensitivity, high linearity and high wearing comfort.

Description

Technical Field

[0001] The invention relates to a capacitive sensor and a preparation method thereof, and in particular to a fabric-type flexible capacitive sensor based on a high-sensitivity and low-resistance nanofiber film and a preparation method thereof. Background Art

[0002] With the development of science and technology and society, flexible electronic technology with bendable and foldable functions has become an important direction for the development of electronic devices. As core components, flexible sensors can effectively acquire and convert external signals, becoming an important component of the widespread application of electronic devices. Based on the extremely low energy loss characteristics, capacitive flexible sensors have become an important development direction for wearable flexible sensors. Fabric-type flexible sensors that take into account both wearing comfort and signal acquisition sensitivity and reliability have become an important research direction for the rapid development of the flexible sensor field due to their broad development and application prospects in the fields of sports health monitoring, intelligent robots, etc.

[0003] Although fabric-based flexible sensors have become one of the frontier research hotspots in the field of flexible sensor technology, existing fabric-based flexible sensors generally have many shortcomings, such as poor mechanical strength, low sensitivity, complex preparation methods, and relatively simple structures. In view of the above shortcomings, domestic and foreign scholars have conducted extensive and in-depth research on improving mechanical strength by adding reinforcing phases, improving sensitivity by changing material composition, and changing the structural form of fabric-based flexible sensors by using methods such as electrospinning and 3D printing. Although the above research has achieved remarkable results in improving the performance of fabric-type flexible sensors, there are still some technical deficiencies in the following aspects: (1) In terms of improving mechanical strength, although the mechanical strength of fabric materials is improved by adding reinforcing phases such as nanoparticles, the simultaneous improvement of electrical sensing performance has not been effectively taken into account; (2) The improvement of polymer electrical sensing performance is mainly achieved by replacing different conductive materials. While improving performance parameters such as conductivity and capacitance, the structural form and application scope of fabric-type flexible sensors are partially limited; (3) The use of stable and mature electrospinning technology has not effectively improved the electrical sensing performance and mechanical strength of nanofibers while increasing the range of optional materials for fabric-type flexible sensors and enriching the structural form. At the same time, the wearing comfort and performance stability are low; (4) Although methods such as the double-layer capacitor principle are adopted to construct capacitive fiber fabrics, their mechanical strength and sensitivity characteristics are not effectively taken into account, which reduces the wide application range. Therefore, the above existing preparation methods cannot form the technical advantages of high efficiency, stability and high wearing comfort, and cannot take into account the existing technical deficiencies of fabric-type flexible capacitive sensors. It is urgent to seek a new design method and preparation technology. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a nanofiber film fabric type flexible capacitive sensor and a preparation method thereof, the preparation method comprising the following steps:

[0005] Step 1, preparation of polyvinylidene fluoride-ionic liquid nanofiber film:

[0006] Step 1.1, according to volume V DMF :V AC =6:4 prepare a mixed solution of N-N-dimethylformamide (DMF) and acetone (AC), slowly add polyvinylidene fluoride (PVDF) powder into the mixed solution in an oil bath at 50°C, and stir mechanically until the PVDF powder is completely dissolved to obtain a PVDF mixed solution with a concentration of 15wt.%;

[0007] Step 1.2, according to the mass fraction of the ionic liquid to the PVDF powder, 40wt.%-70wt.% of the ionic liquid is added to the PVDF mixed solution, and mechanically stirred under a 50°C oil bath condition until the ionic liquid and the PVDF mixed solution are fully mixed to obtain a polyvinylidene fluoride-ionic liquid spinning solution;

[0008] Step 1.3, after ultrasonic treatment, a certain volume of polyvinylidene fluoride-ionic liquid spinning solution is drawn out with a syringe for conjugate spinning to obtain a polyvinylidene fluoride-ionic liquid nanofiber film with a certain thickness (0.2 mm-0.3 mm) and width;

[0009] Step 2: Preparation of polyvinylidene fluoride nanofiber film:

[0010] Step 2.1, by volume V DMF :V AC =6:4 prepare a mixed solution of N-N-dimethylformamide (DMF) and acetone (AC), slowly add polyvinylidene fluoride (PVDF) powder into the mixed solution in an oil bath at 50°C, and stir mechanically until the PVDF powder is completely dissolved to obtain a PVDF mixed solution with a concentration of 15wt.%;

[0011] Step 2.2, after ultrasonic treatment, a certain volume of PVDF mixed solution is extracted with a syringe, and conjugate spinning is performed to obtain a polyvinylidene fluoride nanofiber film with a certain thickness (0.3 mm-0.35 mm) and width;

[0012] Step 3: Preparation of conductive polyvinylidene fluoride nanofiber membrane:

[0013] Step 3.1, according to volume V DMF :V AC=6:4 ratio of NN dimethylformamide (DMF) and acetone (AC) mixed solution, in 50 ℃ oil bath conditions, slowly add polyvinylidene fluoride (PVDF) powder into the mixed solution, then press M PVP :M PVDF =0.35 ratio, slowly add PVP powder into the mixed solution, and stir mechanically until PVDF and PVP powder are completely dissolved to obtain a PVDF mixed solution with a concentration of 15wt.%;

[0014] Step 3.2, after ultrasonic treatment, a certain volume of PVDF mixed solution is extracted with a syringe, and conjugate spinning is performed to obtain a PVP-containing polyvinylidene fluoride nanofiber film of a certain thickness (0.3 mm-0.35 mm) and width;

[0015] Step 3.3, immersing the PVP-containing polyvinylidene fluoride nanofiber film in an ethanol solution for 2-3 hours, then taking it out and drying it to obtain a porous polyvinylidene fluoride nanofiber film;

[0016] Step 3.4, according to the mass ratio M PVP :M 去离子水 =1:9, and obtain a polyvinyl pyrrolidone (PVP) solution by magnetic stirring; ascorbic acid is dissolved in deionized water, and is prepared into an ascorbic acid solution with a concentration of 14.1 mg / mL by magnetic stirring; silver nitrate is added into deionized water to prepare a silver nitrate solution of 0.6 mol / L-1.4 mol / L;

[0017] Step 3.5, mixing equal volumes of ascorbic acid solution and PVP solution to prepare a reducing agent solution, and mixing equal volumes of silver nitrate solution and PVP solution to prepare a reducing solution;

[0018] Step 3.6, immersing the porous polyvinylidene fluoride nanofiber film in a reducing solution for 3-4 hours, then taking it out and placing it in a reducing agent solution for 3-4 hours, then taking it out and absorbing the residual solution to obtain a conductive polyvinylidene fluoride nanofiber film;

[0019] Step 4: Preparation of high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor:

[0020] Step 4.1, cutting the polyvinylidene fluoride-ionic liquid nanofiber film according to size parameters and folding it in half to make a dielectric layer of a flexible capacitive sensor;

[0021] Step 4.2. Cut the conductive polyvinylidene fluoride nanofiber membrane according to the size parameter to make the electrode layer of the flexible capacitive sensor, and the size parameter of the electrode layer is slightly larger than the dielectric layer;

[0022] Step 4.3, cutting the polyvinylidene fluoride nanofiber film according to the size parameter to make a flexible capacitive sensor packaging layer material, the size parameter of which is slightly larger than the electrode layer;

[0023] Step 4.4, in the order of packaging layer, electrode layer, dielectric layer, electrode layer, and packaging layer, various types of materials are combined and packaged to obtain a high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor.

[0024] Furthermore, the conjugate spinning conditions are 20° C., 8.5 kV positive high voltage, 8.5 kV negative high voltage, 12 cm spinning distance, 6 cm spinning height, 20G stainless steel needle, and 0.8 mm / min injection speed.

[0025] Furthermore, the parameters of the ultrasonic treatment are: 50° C., 40 KHz.

[0026] Furthermore, in step 1 of preparing the polyvinylidene fluoride-ionic liquid nanofiber film, the ionic liquid is 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide.

[0027] The nanofiber film fabric type flexible capacitive sensor is prepared by the above preparation method.

[0028] Working principle of the present invention:

[0029] The polyvinylidene fluoride and ionic liquid used in the present invention realize, in addition to the anions and cations in the ionic liquid, a double electric layer model based on hydrogen peroxide ions, hydroxide ions, and superoxide ions through the electrospinning process, providing a dielectric material layer with high capacitance and high sensitivity characteristics for a high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor. Based on the innovative use of the solubility characteristics of polyvinyl pyrrolidone particles in deionized water, a porous nanofiber with high adsorption characteristics is prepared by electrospinning, and a dense and firm silver nanoparticle layer is formed on its outer surface by a reduction reaction, which not only realizes a low-resistance electrode material, but also utilizes the composite effect of inorganic substances and metal nanoparticles to realize the high mechanical strength characteristics of the electrode material from a material perspective. Through a high-sensitivity dielectric layer and a low-resistance electrode layer, the electrical sensing performance foundation of the fabric-type flexible capacitive sensor is established.

[0030] The present invention is based on an oriented polyvinylidene fluoride-based dielectric layer, an electrode layer, and a packaging layer obtained by conjugated spinning, which achieves high mechanical strength while achieving good air permeability from a structural perspective, and establishes a fabric foundation for a flexible sensor composed entirely of polyvinylidene fluoride-based nanofiber membranes, thereby achieving the technical requirements for wearing comfort.

[0031] Beneficial effects of the present invention:

[0032] The present invention starts from the material preparation and structural composition of the fabric-type flexible capacitive sensor, and uses the polyvinylidene fluoride-ionic liquid nanofiber film prepared by the conjugated electrospinning method as the dielectric layer material to establish a high capacitance, high sensitivity, and high mechanical strength foundation; based on the high ion adsorption characteristics of the porous structure polyvinylidene fluoride nanofiber, a dense silver nanoparticle layer is formed on its outer surface by a reduction reaction to construct a conductive polyvinylidene fluoride nanofiber membrane with low resistance characteristics as an electrode material. The fabric-type flexible capacitive sensor with a high-sensitivity ion film is constructed by orderly encapsulation of the polyvinylidene fluoride nanofiber membrane, dielectric material, and electrode material.

[0033] The present invention is based on polyvinylidene fluoride with good flexibility, stability and biocompatibility; a nanofiber membrane with extremely high orientation and conductive function is established through a conjugated electrospinning method and a silver nanoparticle composite process as a mechanical strength basis and an electrode basis; a double-layer dielectric layer consisting of anions and cations in the ionic liquid and hydrogen peroxide ions, hydroxide ions, and superoxide ions is established by using a polyvinylidene fluoride-ionic liquid nanofiber film prepared by a conjugated electrospinning method; a good air permeability and wearability foundation is established based on the nanofiber membrane dielectric layer, electrode, and packaging form. At the same time, the fabric characteristics of the nanofiber membrane enable the flexible capacitive sensor to have a variety of structural forms through packaging, weaving, and other methods. The preparation process based on high-sensitivity ion film and low-resistance electrode involved in the present invention is efficient, convenient and repeatable. The prepared fabric-type flexible capacitive sensor based on high-sensitivity ion film has high mechanical properties, high conductivity, high sensitivity, high linearity and high wearing comfort, and can effectively and real-time detect tiny strains. The soft, foldable and cuttable polyvinylidene fluoride based nanofiber membrane can realize diversified structural forms through packaging, weaving and other methods to meet diversified application needs, providing an effective new method for the widespread application of fabric-type flexible sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the microscopic morphology of polyvinylidene fluoride-ionic liquid nanofiber films with different ionic liquid contents of the present invention.

[0035] Figure 2 This is a schematic diagram of the microscopic morphology of the polyvinylidene fluoride nanofiber film of the present invention.

[0036] Figure 3 It is a schematic diagram of the microscopic morphology of the porous polyvinylidene fluoride nanofiber membrane and the conductive polyvinylidene fluoride nanofiber membrane of the present invention.

[0037] Figure 4 This is a schematic diagram of stress and strain of the conductive polyvinylidene fluoride nanofiber membrane of the present invention.

[0038] Figure 5Schematic diagram of stress-strain of polyvinylidene fluoride-ionic liquid nanofiber films with different ionic liquid contents of the present invention.

[0039] Figure 6 This is a schematic diagram of the capacitance of the polyvinylidene fluoride-ionic liquid nanofiber film with different ionic liquid contents of the present invention.

[0040] Figure 7 This is a schematic diagram of the electrical conductivity of the conductive polyvinylidene fluoride nanofiber membrane of the present invention.

[0041] Figure 8 This is a schematic diagram of the sensitivity of the polyvinylidene fluoride-ionic liquid nanofiber film with different ionic liquid contents of the present invention.

[0042] Fig. 9 This is a schematic diagram of the test signal of 5000 cycles of the polyvinylidene fluoride-ionic liquid nanofiber membrane with 60 wt.% ionic liquid content of the present invention.

[0043] Fig.10 This is a schematic diagram of the constant strain and variable rate cyclic test signal of the high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor with 50wt.% ionic liquid content of the present invention.

[0044] Fig.11 This is a schematic diagram of the joint bending test signal of the high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor with 50wt.% ionic liquid content of the present invention.

[0045] Fig.12 This is a schematic diagram of a finger light pressure test signal of a high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor with a 70wt.% ionic liquid content according to the present invention. DETAILED DESCRIPTION

[0046] This embodiment provides a method for preparing a nanofiber film fabric type flexible capacitive sensor, comprising the following steps:

[0047] Step 1, preparation of polyvinylidene fluoride-ionic liquid nanofiber film:

[0048] Step 1.1, according to volume V DMF =6mL,V AC =4mL prepared a mixed solution of NN dimethylformamide (DMF) and acetone (AC), slowly added 1.554g polyvinylidene fluoride (PVDF) powder into the mixed solution under 50℃ oil bath condition, and mechanically stirred at a speed of 500r / min for 2 hours until the PVDF powder was completely dissolved to obtain a PVDF mixed solution;

[0049] Step 1.2, according to the mass fraction of the ionic liquid 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide to the PVDF powder, 40wt.%, 50wt.%, 60wt.%, or 70wt.% of the ionic liquid is added to the PVDF mixed solution, and mechanically stirred at a speed of 500r / min for 30 minutes under a 50°C oil bath condition until the ionic liquid and the PVDF mixed solution are fully mixed to obtain a polyvinylidene fluoride-ionic liquid spinning solution;

[0050] Step 1.3, after ultrasonic treatment (50°C, 40KHz), a certain volume of polyvinylidene fluoride-ionic liquid spinning solution was extracted with a syringe, and conjugate spinning was performed under the conditions of 20°C, 8.5kV positive high voltage, 8.5kV negative high voltage, 12cm spinning distance, 6cm spinning height, 20G stainless steel needle, and 0.8mm / min injection speed to obtain a polyvinylidene fluoride-ionic liquid nanofiber film with a certain thickness (0.2mm-0.3mm) and width;

[0051] Step 2: Preparation of polyvinylidene fluoride nanofiber film:

[0052] Step 2.1, by volume V DMF =6mL,V AC =4mL prepared a mixed solution of NN dimethylformamide (DMF) and acetone (AC), slowly added 1.554g polyvinylidene fluoride (PVDF) powder into the mixed solution under 50℃ oil bath condition, and mechanically stirred at a speed of 500r / min for 2 hours until the PVDF powder was completely dissolved to obtain a PVDF mixed solution;

[0053] Step 2.2, after ultrasonic treatment (50°C, 40KHz), a certain volume of PVDF mixed solution was extracted with a syringe, and conjugate spinning was performed under the conditions of 20°C, 8.5kV positive high voltage, 8.5kV negative high voltage, 12cm spinning distance, 6cm spinning height, 20G stainless steel needle, and 0.8mm / min injection speed to obtain a polyvinylidene fluoride nanofiber film with a certain thickness (0.3mm-0.35mm) and width;

[0054] Step 3: Preparation of conductive polyvinylidene fluoride nanofiber membrane:

[0055] Step 3.1, by volume V DMF :V AC =6:4 ratio of NN dimethylformamide (DMF) and acetone (AC) mixed solution, in 50 ℃ oil bath conditions, slowly add polyvinylidene fluoride (PVDF) powder into the mixed solution, then press M PVP :M PVDF=0.35, slowly add PVP powder into the mixed solution, and stir mechanically until PVDF and PVP powder are completely dissolved to obtain a 15wt.% PVDF mixed solution;

[0056] Step 3.2, after ultrasonic treatment, a certain volume of PVDF mixed solution is extracted with a syringe, and conjugate spinning is performed to obtain a PVP-containing polyvinylidene fluoride nanofiber film of a certain thickness (0.3 mm-0.35 mm) and width;

[0057] Step 3.3, immersing the PVP-containing polyvinylidene fluoride nanofiber film in an ethanol solution for 2 hours, then taking it out and drying it to obtain a porous polyvinylidene fluoride nanofiber film;

[0058] Step 3.4, according to the mass ratio M PVP :M 去离子水 =1:9, and obtain a polyvinyl pyrrolidone (PVP) solution by magnetic stirring; ascorbic acid is dissolved in deionized water, and is prepared into a 14.1 mg / mL ascorbic acid solution by magnetic stirring; silver nitrate is added into deionized water to prepare a 0.6 mol / L, 1 mol / L, 1.2 mol / L, or 1.4 mol / L silver nitrate solution;

[0059] Step 3.5, mixing equal volumes of ascorbic acid solution and PVP solution to prepare a reducing agent solution, and mixing equal volumes of silver nitrate solution and PVP solution to prepare a reducing solution;

[0060] Step 3.6, immersing the porous polyvinylidene fluoride nanofiber film in a reducing solution for 3-4 hours, then taking it out and placing it in a reducing agent solution for 3-4 hours, then taking it out and absorbing the residual solution to obtain a conductive polyvinylidene fluoride nanofiber film;

[0061] Step 4: Preparation of high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor:

[0062] Step 4.1, cutting the polyvinylidene fluoride-ionic liquid nanofiber film according to size parameters and folding it in half to make a dielectric layer of a flexible capacitive sensor;

[0063] Step 4.2, cutting the conductive polyvinylidene fluoride nanofiber membrane according to the size parameter to make the flexible capacitive sensor electrode layer, the size parameter of which is slightly larger than the dielectric layer;

[0064] Step 4.3, cutting the polyvinylidene fluoride nanofiber film according to the size parameter to make a flexible capacitive sensor packaging layer material, the size parameter of which is slightly larger than the electrode layer;

[0065] Step 4.4, in the order of packaging layer, electrode layer, dielectric layer, electrode layer, and packaging layer, various types of materials are combined and packaged to obtain a high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor.

[0066] The microstructures of polyvinylidene fluoride-ionic liquid nanofiber film, polyvinylidene fluoride nanofiber film, porous polyvinylidene fluoride nanofiber membrane and conductive polyvinylidene fluoride nanofiber membrane were analyzed.

[0067] Based on the preparation method, the present invention successfully prepared polyvinylidene fluoride-ionic liquid nanofiber film, polyvinylidene fluoride nanofiber film, porous polyvinylidene fluoride nanofiber film and conductive polyvinylidene fluoride nanofiber film. When the ionic liquid content gradually increases, the average diameter of the single fiber gradually increases, and the porosity of the film gradually increases (such as Figure 1 Fibers in the conjugate spinning form), polyvinylidene fluoride-ionic liquid nanofiber films, polyvinylidene fluoride nanofiber thin films (such as Figure 2 Fibers in), porous polyvinylidene fluoride nanofiber membranes (such as Figure 3 (a) fibers), conductive polyvinylidene fluoride nanofiber membranes (e.g. Figure 3 The fibers in (b) are arranged in the same direction as a whole and have good orientation. After the reduction reaction, the silver nanoparticles are evenly distributed on the surface of the porous polyvinylidene fluoride nanofibers, and the silver nanoparticles are tightly combined with the fibers. The microscopic morphology results of various types of nanofibers show that the preparation method of the nanofiber membrane of the present invention is feasible, and the microscopic morphology changes caused by ionic liquids and silver nanoparticles on the nanofibers establish an efficient material foundation for their mechanical strength and electrical sensing properties.

[0068] The stress-strain, capacitance, conductivity, sensitivity and cycle durability of polyvinylidene fluoride-ionic liquid nanofiber film and conductive polyvinylidene fluoride nanofiber membrane are analyzed to determine the effectiveness of the dielectric layer and electrode layer.

[0069] The stress-strain of the conductive polyvinylidene fluoride nanofiber membrane prepared by the present invention is as follows: Figure 4 As shown in the figure, the mechanical strength of porous polyvinylidene fluoride nanofibers is significantly improved after being compounded with silver nanoparticles. Figure 5 As shown in the figure, as the ionic liquid content increases, the stress value of the polyvinylidene fluoride-ionic liquid nanofiber film gradually decreases. This is mainly due to the increase in fiber porosity and the decrease in elastic modulus caused by the increase in ionic liquid content. The combination of the oriented nanofiber arrangement and the nanofiber membrane layers with good mechanical strength effectively establishes the mechanical strength foundation of the fabric-type flexible capacitive sensor. The capacitance of the polyvinylidene fluoride-ionic liquid nanofiber film with different ionic liquid contents under no load and with a 500g weight applied is shown in Figure 2. Figure 6As shown, under no-load conditions, the increase in ionic liquid content effectively increases the capacitance of the polyvinylidene fluoride nanofibers. After the load is applied, the capacitance of each polyvinylidene fluoride nanofiber changes with the load, which effectively proves that the idea and method of preparing the capacitive nanofiber membrane of the present invention are feasible, and it is feasible to use the polyvinylidene fluoride-ionic liquid nanofiber film as the dielectric layer of the capacitive flexible sensor. Figure 7 The conductivity diagram of the conductive polyvinylidene fluoride nanofiber film shown in the figure effectively proves that the preparation method of the conductive nanocomposite fiber involved in the present invention is feasible, and the prepared conductive polyvinylidene fluoride nanofiber film has low resistance characteristics, and it is feasible to use it as the electrode layer of the capacitive flexible sensor. The sensitivity of the polyvinylidene fluoride-ionic liquid nanofiber film is an important condition for determining the application of fabric-type flexible capacitive sensors. Figure 8 The sensitivity diagram of polyvinylidene fluoride-ionic liquid nanofiber film with different ionic liquid contents effectively shows the sensitivity change process of various types of fiber films under 0-5KPa load conditions, and effectively shows that the capacitive flexible sensor involved in the present invention has an application basis under load conditions. Fig. 9 As shown, the signal output effect diagram of the polyvinylidene fluoride-ionic liquid nanofiber film with an ionic liquid content of 60wt.% was tested during 5000 cycles under 20% strain and 100mm / min loading rate conditions. During 5000 consecutive tests, the polyvinylidene fluoride-ionic liquid nanofiber film prepared by the present invention has a stable and effective signal output function, which effectively proves the effectiveness and innovation of the preparation method involved in the present invention and establishes an effective foundation for application.

[0070] The applicability of the fabric capacitive flexible sensor is determined by analyzing the strain, variable rate cycle test, knuckle test, and finger light pressure test of the high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor.

[0071] Based on the preparation method of the present invention, the packaging layer, the electrode layer, and the dielectric layer are assembled into a fabric-type flexible capacitive sensor based on a high-sensitivity and low-resistance nanofiber film, and the sensor is subjected to 30 cycles of loading at loading rates of 1 mm / min, 2 mm / min, 4 mm / min, 10 mm / min, 20 mm / min, 40 mm / min, 100 mm / min, 200 mm / min, 400 mm / min, 600 mm / min, and 1000 mm / min, respectively, under a strain of 40%. Fig.10 ). Under the conditions of large strain and loading rate, the nanofiber film fabric-type flexible capacitive sensor has a stable signal output function, which effectively verifies that the fabric-type flexible sensor prepared by the present invention is effective in the test environment of large strain, large loading rate, and multiple cycles. At the same time, under the conditions of small strain and small load, such as finger joint activities (such as Fig.11 ) and finger press (such as Fig.12 ), it can still produce effective load sensing function to produce capacitance changes. The results of various test environments show that the method for preparing a fabric-type flexible capacitive sensor based on a high-sensitivity and low-resistance nanofiber film of the present invention is effective and feasible. The prepared fabric-type flexible capacitive sensor has high sensitivity, high mechanical strength, high stability, and high adaptability. It can effectively respond to large strain and large load environments, as well as small strain and small load environments. It has the advantages of wide application environments and reliable test results.

Claims

1. A method for preparing a nanofiber film fabric type flexible capacitive sensor, Features: The following steps are involved: Step 1, preparation of polyvinylidene fluoride-ionic liquid nanofiber film: Step 1.1, according to volume V DMF :V AC =6:4 ratio of NN dimethylformamide and acetone to prepare a mixed solution, in a 50°C oil bath condition, slowly add polyvinylidene fluoride powder into the mixed solution, and mechanically stir until the PVDF powder is completely dissolved to obtain a PVDF mixed solution with a concentration of 15wt.%; Step 1.2, according to the mass fraction of the ionic liquid to the PVDF powder, 40wt.%-70wt.% of the ionic liquid is added to the PVDF mixed solution, and mechanically stirred under a 50°C oil bath condition until the ionic liquid and the PVDF mixed solution are fully mixed to obtain a polyvinylidene fluoride-ionic liquid spinning solution; Step 1.3, after ultrasonic treatment, a certain volume of polyvinylidene fluoride-ionic liquid spinning solution is drawn out with a syringe for conjugate spinning to obtain a polyvinylidene fluoride-ionic liquid nanofiber film of a certain thickness and width; Step 2: Preparation of polyvinylidene fluoride nanofiber film: Step 2.1, by volume V DMF :V AC =6:4 ratio of NN dimethylformamide and acetone to prepare a mixed solution, in a 50°C oil bath condition, slowly add polyvinylidene fluoride powder into the mixed solution, and mechanically stir until the PVDF powder is completely dissolved to obtain a 15wt.% PVDF mixed solution; Step 2.2, after ultrasonic treatment, a certain volume of PVDF mixed solution is extracted with a syringe, and conjugate spinning is performed to obtain a polyvinylidene fluoride nanofiber film of a certain thickness and width; Step 3: Preparation of conductive polyvinylidene fluoride nanofiber membrane: Step 3.1, by volume V DMF :V AC =6:4 ratio of NN dimethylformamide and acetone solution, slowly add polyvinylidene fluoride powder into the mixed solution under 50℃ oil bath condition, then press M PVP :M PVDF =0.35 ratio, slowly add PVP powder into the mixed solution, and stir mechanically until PVDF and PVP powder are completely dissolved to obtain a PVDF mixed solution with a concentration of 15wt.%; Step 3.2, after ultrasonic treatment, a certain volume of PVDF mixed solution is extracted with a syringe, and conjugate spinning is performed to obtain a PVP-containing polyvinylidene fluoride nanofiber film of a certain thickness and width; Step 3.3, immersing the PVP-containing polyvinylidene fluoride nanofiber film in an ethanol solution for 2-3 hours, then taking it out and drying it to obtain a porous polyvinylidene fluoride nanofiber film; Step 3.4: Prepare according to the mass ratio of M PVP :M 去离子水 = 1:9, and obtain a polyvinylpyrrolidone solution through magnetic stirring; dissolve ascorbic acid in deionized water and prepare an ascorbic acid solution with a concentration of 14.1 mg / mL through magnetic stirring; add silver nitrate to deionized water and prepare a silver nitrate solution with a concentration of 0.6 mol / L - 1.4 mol / L; Step 3.5, mixing equal volumes of ascorbic acid solution and PVP solution to prepare a reducing agent solution, and mixing equal volumes of silver nitrate solution and PVP solution to prepare a reducing solution; Step 3.6, immersing the porous polyvinylidene fluoride nanofiber film in a reducing solution for 3-4 hours, then taking it out and placing it in a reducing agent solution for 3-4 hours, then taking it out and absorbing the residual solution to obtain a conductive polyvinylidene fluoride nanofiber film; Step 4: Preparation of high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor: Step 4.1, cutting the polyvinylidene fluoride-ionic liquid nanofiber film according to size parameters and folding it in half to make a dielectric layer of a flexible capacitive sensor; Step 4.2, cutting the conductive polyvinylidene fluoride nanofiber membrane according to the size parameter to make the flexible capacitive sensor electrode layer, the size parameter of which is slightly larger than the dielectric layer; Step 4.3, cutting the polyvinylidene fluoride nanofiber film according to the size parameter to make a flexible capacitive sensor packaging layer material, the size parameter of which is slightly larger than the electrode layer; Step 4.4, in the order of packaging layer, electrode layer, dielectric layer, electrode layer, and packaging layer, various types of materials are combined and packaged to obtain a high-sensitivity, low-resistance nanofiber film fabric-type flexible capacitive sensor.

2. A method for preparing a nanofiber film fabric type flexible capacitive sensor according to claim 1, Features: The conjugate spinning conditions are 20° C., 8.5 kV positive high voltage, 8.5 kV negative high voltage, 12 cm spinning distance, 6 cm spinning height, 20G stainless steel needle, and 0.8 mm / min injection speed.

3. The method for preparing a nanofiber film fabric type flexible capacitive sensor according to claim 1, Features: The parameters of the ultrasonic treatment are: 50° C., 40 KHz.

4. The method for preparing a nanofiber film fabric type flexible capacitive sensor according to claim 1, Features: In the preparation of the polyvinylidene fluoride-ionic liquid nanofiber film in step 1, the ionic liquid is 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide.

5. The method for preparing a nanofiber film fabric type flexible capacitive sensor according to claim 1, Features: The thickness of the polyvinylidene fluoride-ionic liquid nanofiber film is 0.2mm-0.3mm; the thickness of the polyvinylidene fluoride nanofiber film is 0.3mm-0.35mm; the thickness of the PVP-containing polyvinylidene fluoride nanofiber film is 0.3mm-0.35mm.

6. A nanofiber film fabric type flexible capacitive sensor, Features: Prepared according to any one of the preparation methods of claims 1-5.

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