A waterproof and breathable flexible resistance type pressure sensor based on a PA6 full fiber network and a preparation method thereof

Abstract

The application discloses a waterproof and breathable flexible resistance type pressure sensor based on a PA6 full-fiber network and a preparation method thereof, and belongs to the technical field of flexible pressure sensors.The application prepares a plurality of fiber structures based on PA6 through an electrostatic spinning technology and obtains a full-fiber resistance type pressure sensor.PA6 / PS fibers serve as the outermost layer to provide waterproof characteristics, PA6 / Au fibers serve as a flexible electrode layer, pure PA6 fibers serve as an isolation layer, and PA6 / PANI fibers serve as a sensitive layer.The introduction of the isolation layer significantly improves the linearity of the sensor, the linear detection range gradually increases with the increase of the thickness of the isolation layer, and the sensor has good repeatability and fast response recovery time.In addition, the sensor prepared by the application adopts a full-fiber structure and has good air permeability, so that sweat can be fully volatilized during long-time wearing;the outer layer of the sensor is encapsulated by hydrophobic fibers, and the sensor has good waterproof characteristics.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flexible pressure sensors, and particularly relates to a waterproof and breathable flexible resistance type pressure sensor based on a PA6 full fiber network and a preparation method thereof. BACKGROUND

[0002] Pressure sensors are widely used in the fields of smart cities, industrial production, consumer electronics, medical care, mechanical automation, etc. However, with the continuous development of electronic skin and wearable electronic devices, the application scenarios of pressure sensors tend to be diversified and complicated, and many curved and uneven contact surfaces appear. Traditional ceramic pressure-sensitive materials cannot be closely combined with these specific shapes due to poor compliance and no conformability, and have certain limitations. Compared with traditional rigid electronic devices, flexible and wearable electronic devices have flexibility, stretchability, and are very thin, and can adapt to various shapes and many other advantages, which have become the development trend in the future and have been widely studied by more and more scholars.

[0003] Flexible pressure sensors are divided into resistance type, capacitance type, triboelectric type and piezoelectric type according to the sensing mechanism. The resistance type pressure sensor converts external stimulation into resistance change. This type of sensor has excellent device performance, simple structure, and is easy to collect output signals. The device is usually composed of a flexible substrate, a flexible electrode and a sensitive material. The change of resistance after the device is subjected to pressure mainly comes from the bulk resistance change of the sensitive material and the contact resistance change between the sensitive material and the electrode. Therefore, the preparation of the topography structure of the sensitive material is the research focus of the preparation of high-performance resistance type pressure sensors.

[0004] In order to improve the performance of the resistance type pressure sensor, in addition to selecting appropriate elastic substrates and conductive fillers, various microstructures or nanoscale geometric structures can also be constructed to improve the sensitivity and detection range of the pressure sensor. Among them, the fiber structure in the form of nanofiber, yarn, fabric and textile has high flexibility, light weight and becomes an ideal candidate for the preparation of wearable sensors. This structure has a large specific surface area, high porosity and rich contact points, and can construct a pressure sensor with high sensitivity and fast response speed. However, this type of sensor usually has a small detection range under the premise of achieving high sensitivity, and the high pressure area is easy to saturate. Therefore, in practical applications, we pursue high sensitivity while hoping to prepare a sensor with high linearity. In addition to excellent mechanical sensing performance, many practical properties are also needed in the actual use process. The sensor is often in close contact with the skin when worn, and needs good air permeability to increase the wearing comfort. In addition, the sensor needs to have certain waterproof properties, otherwise it is easy to short circuit in a high humidity environment. Therefore, it is very important to invent a flexible resistance type pressure sensor with waterproof and breathable properties. SUMMARY

[0005] The present application aims to provide a waterproof and breathable flexible resistance type pressure sensor based on a polyamide 6 (PA6) full fiber network and a preparation method thereof.

[0006] The present application prepares a variety of fiber structures based on PA6 by electrospinning technology and makes a full fiber resistance type pressure sensor. Among them, polyamide 6 / polystyrene (PA6 / PS) fiber provides waterproof properties as the outermost layer, polyamide 6 / gold (PA6 / Au) fiber is a flexible electrode layer, pure PA6 fiber is an isolation layer which greatly increases linearity, and polyamide 6 / polyaniline (PA6 / PANI) fiber is a sensitive layer. The results show that the waterproof and breathable flexible resistance type pressure sensor based on the PA6 full fiber network significantly improves the linearity of the sensor by introducing an isolation layer between the sensitive layer and the electrode layer. With the increase of the thickness of the isolation layer, the linear detection range gradually increases. Example 2 shows linearity in a wide range of 0-37 kPa, and the sensitivity can reach 66 kPa -1 , which is 5.68 times larger than that of the sensor without the isolation layer, and the sensor has good repeatability and fast response recovery time. The sensor prepared by the present application adopts a full fiber structure and has good air permeability, which can make the sweat fully evaporate during long-term wearing. The outer layer of the sensor is packaged by hydrophobic fiber, which shows good waterproof properties.

[0007] The preparation method of the waterproof and breathable flexible resistance type pressure sensor based on the PA6 full fiber network according to the present application comprises the following steps:

[0008] (1) Preparation of waterproof layer

[0009] Dissolve 1.5 g of PA6 particles in 4.5-13.5 g of formic acid and stir at room temperature for 10-15 h to obtain a PA6 spinning solution; dissolve 2.5 g of PS particles in 5-10 g of DMF and stir at room temperature for 10-15 h to obtain a PS spinning solution; load the PA6 spinning solution and the PS spinning solution into 10 mL syringes with 19G needles respectively, and electrospin synchronously at a flow rate of 0.1 mL / h and 0.5 mL / h under a voltage of 18-25 kV on the same collection device for 1.5-3.0 h; the distance between the two needles placed above and below is fixed at 5 cm, and the collection device is placed at a position 10-20 cm away from the two needles; the environmental temperature is controlled at 18-22℃ during the spinning process, and the environmental humidity is 25-35% RH; then a PA6 / PS fiber waterproof layer is obtained on the collection device, and the solvent is completely volatilized by drying at room temperature;

[0010] (2) Preparation of electrode

[0011] The PA6 spinning solution is obtained by dissolving 1.5 g of PA6 particles in 4.5-13.5 g of formic acid and stirring at room temperature for 10-15 h; the PA6 spinning solution is loaded into a 10 mL needle tube with a 19G needle, and electrospinning is performed on the surface of the PA6 / PS fiber waterproof layer obtained in step (1) at a flow rate of 0.1 mL / h under a voltage of 18-25 kV for 1-2 h to obtain a composite fiber film; then, an 80-120 nm thick Au is deposited according to the electrode mask pattern, so as to prepare a PA6 / Au flexible electrode layer on the PA6 / PS fiber waterproof layer;

[0012] (3) Preparation of isolation layer

[0013] The PA6 spinning solution is obtained by dissolving 1.5 g of PA6 particles in 4.5-13.5 g of formic acid and stirring at room temperature for 10-15 h; the PA6 spinning solution is loaded into a 10 mL needle tube with a 19G needle, and electrospinning is performed on the PA6 / Au flexible electrode layer obtained in step (2) at a flow rate of 0.1 mL / h under a voltage of 18-25 kV for 5-15 min, so as to obtain a pure PA6 fiber isolation layer on the PA6 / Au flexible electrode layer;

[0014] (4) Preparation of sensitive layer

[0015] ① The PA6 spinning solution is obtained by dissolving 1.5 g of PA6 particles in 4.5-13.5 g of formic acid and stirring at room temperature for 10-15 h; the PA6 spinning solution is loaded into a 10 mL needle tube with a 19G needle, and electrospinning is performed at a flow rate of 0.1 mL / h under a voltage of 18-25 kV for 4-6 h to obtain a PA6 fiber film;

[0016] ② 46 μL of aniline is dissolved in 15 mL of 0.8-1.2 mol / L HCL, and ultrasonic treatment is performed in an ice water bath for 20-40 min to obtain solution A; 57 mg of ammonium persulfate is dissolved in 15 mL of 0.8-1.2 mol / L HCL, and magnetic stirring is performed in an ice water bath for 20-40 min to obtain solution B; then, solution B is added to solution A and stirred uniformly, and the PA6 fiber film obtained in step ① is immersed in the mixed solution, and placed in the dark under ice bath conditions for 1-2 h to obtain a PA6 / PANI fiber sensitive layer in which polyaniline is polymerized.

[0017] (5) Preparation of sensor

[0018] ① The PA6 / PS fiber waterproof layer-PA6 / Au fiber flexible electrode layer-pure PA6 fiber isolation layer is cut into a size of 12 mm×12 mm, wherein the size of the Au electrode is 4 mm×10 mm, a copper wire with a diameter of 0.1 mm is fixed on one side of the wide edge of the Au electrode as a lead wire, and drying is performed;

[0019] ②Cut the PA6 / PANI fiber sensitive layer into a size of 6mmx6mm, and assemble in the order of PA6 / PS fiber waterproof layer-PA6 / Au flexible electrode layer-pure PA6 fiber isolation layer-PA6 / PANI fiber sensitive layer-pure PA6 fiber isolation layer-PA6 / Au flexible electrode layer-PS / PA6 fiber waterproof layer, the two strip-shaped Au electrodes in the two PA6 / Au flexible electrode layers are arranged perpendicular to each other, the PA6 / PANI fiber sensitive layer does not contact the silver paste lead, the sensitive area is 4mmx4mm, and finally the film is compacted and fixed by a hot pressing process, so that the sensor resistance type pressure sensor is obtained.

[0020] The waterproof and breathable flexible resistance type pressure sensor based on the PA6 full fiber network is prepared by the above method.

[0021] The advantages of the present application are as follows:

[0022] (1) A variety of fiber structures based on PA6 are prepared by electrospinning for making the waterproof layer, electrode layer, isolation layer and sensitive layer of the sensor, and the manufacturing process is simple and the cost is low.

[0023] (2) By introducing the isolation layer, the linear range of the sensor is improved from 0-3.6kPa to 0-80kPa, and the sensitivity can still reach 66kPa -1 (0-37kPa in Example 2), and has good repeatability and fast response recovery time.

[0024] (3) The flexible resistance type pressure sensor based on the PA6 full fiber network prepared by the present application also has waterproofness and air permeability, which is very important in practical application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structure schematic view of the waterproof and breathable flexible resistance type pressure sensor based on the PA6 full fiber network;

[0026] Figure 2 (a) is an SEM image of the pure PA6 fiber isolation layer, Figure 2 (b) is an SEM image of the PA6 / Au fiber electrode layer, Figure 2 (c) is an SEM image of the PA6 / PS fiber waterproof layer, and the inserted image is a local enlarged SEM image of the PA6 / PS fiber, Figure 2 (d) is an SEM image of the PA6 / PANI fiber sensitive layer;

[0027] Figure 3The curves showing the change in current between the two electrodes of the sensor as a function of pressure in Examples 1, 2, 3, and the comparative example of this invention are shown.

[0028] Figure 4 (a) shows the current variation curves of Example 2 under different pressures of 10–30 kPa for six loading cycles. Figure 4 (b) shows the response time and recovery time curves of the sensor;

[0029] Figure 5 (a) Photographs of droplets with different pH values ​​placed on the sensor surface in Example 2. Figure 5 (b) is a photograph of the water contact angle of the sensor in Example 2. Figure 5 (c) shows the water vapor permeability curves of the four thin films;

[0030] like Figure 1 As shown, the names of each part are: PA6 / PS fiber waterproof layer 1, PA6 / PANI fiber sensitive layer 2, pure PA6 fiber isolation layer 3, PA6 / Au fiber electrode layer 4. The size of the sensitive layer is 6mm×6mm, the size of the waterproof layer is 12mm×12mm, the length of the electrode layer is 10mm and the width is 4mm, and the sensitive area is 4mm×4mm.

[0031] like Figure 2 As shown in Figure (a), the diameter of pure PA6 fibers is about 100 nm and the fiber surface is smooth. In Figure (b), the diameter of PA6 / Au fibers with a 100 nm gold deposit is significantly increased and the surface roughness is increased. Figure (c) shows PS / PA6 fibers prepared by synchronous electrospinning. It can be seen that the two fibers are interwoven and evenly distributed. The diameter of PS fibers is about 3 μm and that of PA6 fibers is about 100 nm. In Figure (d), after a layer of PANI is polymerized on the surface of PA6 fibers, obvious particle aggregation can be seen on the fiber surface. The fiber diameter becomes larger and the surface becomes rougher.

[0032] like Figure 3 As shown, the sensor fabricated in this invention exhibits a gradual increase in current variation with increasing pressure within the range of 0–80 kPa. The comparative example sensor, however, has a linear range of 0–3.6 kPa in the first segment, although its sensitivity can reach 273 kPa. -1 However, it is prone to saturation in the high-pressure range. As can be observed from the figure, with the increase of the insulation layer thickness, the linear range of Examples 1, 2, and 3 gradually increases, reaching 0–14 kPa, 0–37 kPa, and 0–80 kPa respectively, with sensitivities in the linear region of 133 kPa. -1 66kPa -1 20.45 kPa -1 ;

[0033] As shown in Figure 4 Figure (a) is the change of current value of the sensor in Example 2 during different pressure cycle load process, it can be seen that the current change of the sensor remains consistent during the process of loading different pressures of 10-30 kPa for six cycles, which shows good repeatability; Figure (b) is the response time and recovery time of the sensor in Example 2 obtained by loading and unloading 2 kPa pressure, which are 52 ms and 78 ms respectively, indicating that the sensor has fast response and recovery time.

[0034] As shown in Figure 5 Figure (a) is the photos of droplets of different pH values on the surface of the sensor in Example 2, which shows that the sensor can exhibit good hydrophobicity in various acid-base environments; Figure (b) is the water contact angle measured on the surface of the sensor in Example 2, which is 144°, further proving that the sensor has good hydrophobicity; Figure (c) is the water vapor permeability of commonly used PDMS film, medical dressing PU film, and PA6 fiber film and PA6 / PS fiber film prepared in the present application, it can be seen from the figure that compared with traditional rubber materials, the fiber film in the present application has good air permeability.

[0035] Note: the calculation method of sensitivity is where I P is the current value of the sensor under a certain pressure, I0 is the current value of the sensor without load, and ΔP is the pressure change of the sensor. DETAILED DESCRIPTION

[0036] Comparative Example 1:

[0037] A waterproof and breathable flexible resistance type pressure sensor based on PA6 full fiber network and a preparation method thereof, the steps are as follows:

[0038] (1) waterproof layer: 1.5 g of PA6 particles is dissolved in 8.5 g of formic acid and stirred at room temperature for 12 h to obtain a 15 wt% PA6 spinning solution. 2.5 g of PS particles is dissolved in 7.5 g of DMF and stirred at room temperature for 12 h to obtain a 25 wt% PS spinning solution. The PA6 and PS solutions are respectively loaded into 10 mL syringes with 19G needles, and the flow rates are 0.1 mL / h and 0.5 mL / h, and the voltage is 20 kV. The distance between the two needles is fixed at 5 cm, and the collection device is placed 16 cm away from the two needles. The environmental temperature is controlled at 20℃ and the environmental humidity is 30% RH during the spinning process. After two hours, a PA6 / PS fiber film is obtained, which is dried at room temperature to completely volatilize the solvent.

[0039] (2) Electrode layer: 1.5 g PA6 particles were dissolved in 8.5 g formic acid and stirred at room temperature for 12 h to obtain a 15 wt% PA6 spinning solution. The prepared PA6 / PS fiber film was electrospun with a flow rate of 0.1 mL / h and a voltage of 20 kV for 1 h to obtain a composite fiber film for the electrode. The PS / PA6 fibers were cut to a fixed size and deposited with a 100 nm gold layer according to the mask pattern to obtain a PA6 / Au electrode.

[0040] (3) Sensing layer: 1.5 g PA6 particles were dissolved in 8.5 g formic acid and stirred at room temperature for 12 h to obtain a 15 wt% PA6 spinning solution. The PA6 solution was loaded into a 10 mL needle tube with a 19G needle and electrospun at a flow rate of 0.1 mL / h and a voltage of 20 kV. After 5 h, pure PA6 fibers were obtained. The fibers were cut to a fixed size for use. 46 μL aniline was dissolved in 15 mL HCL (concentration 1.0 mol / L) and ultrasonicated in an ice water bath for 30 min to obtain solution A; 57 mg ammonium persulfate was dissolved in 15 mL HCL (concentration 1.0 mol / L) and magnetically stirred in an ice water bath for 30 min to obtain solution B; then, solution B was added to solution A and stirred uniformly, and the cut PA6 fiber film was immersed in the mixed solution and placed in the dark under ice water for 1.5 h to obtain PA6 fibers with polymerized polyaniline as the sensing material.

[0041] (4) The prepared electrode was cut to a fixed size of 12 mm x 12 mm, with a gold electrode pattern deposited with a width of 4 mm and a length of 10 mm. A 0.1 mm diameter copper wire was fixed to the electrode side as a lead wire and dried under a lamp. The prepared PA6 / PANI fiber sensing material was cut to a fixed size of 6 mm x 6 mm, and assembled in the order of electrode, sensing layer, and electrode, with the two strip-shaped electrodes placed perpendicular to each other and the sensing material not in contact with the lead wire. The sensing area was 4 mm x 4 mm, and finally the three layers of film were fixed to form a sensor by a hot pressing process.

[0042] Example 1:

[0043] A waterproof and breathable flexible resistance type pressure sensor based on a PA6 full fiber network and a preparation method thereof, the steps of which are as follows:

[0044] (1) Waterproof layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. 2.5g of PS particles were dissolved in 7.5g of DMF and stirred at room temperature for 12h to obtain a 25wt% PS spinning solution. The PA6 and PS solutions were respectively loaded into 10mL syringes equipped with 19G needles and electrospun synchronously at a flow rate of 0.1mL / h and 0.5mL / h, respectively, at a voltage of 20kV. The distance between the two needles was fixed at 5cm, and the collecting device was placed 16cm away from the two needles. The ambient temperature was controlled at 20℃ and the ambient humidity at 30%RH during the spinning process. After two hours, a PA6 / PS fiber film was obtained and dried at room temperature to allow the solvent to completely evaporate.

[0045] (2) Electrode layer: 1.5 g of PA6 particles were dissolved in 8.5 g of formic acid and stirred at room temperature for 12 h to obtain a 15 wt% PA6 spinning solution. PA6 was electrospun separately on the prepared PS / PA6 fiber film at a flow rate of 0.1 mL / h and a voltage of 20 kV for 1 h to obtain a composite fiber film for preparing the electrode. PA6 / PS fibers were cut to a fixed size and a 100 nm layer of gold was deposited according to a mask pattern to prepare a PA6 / Au electrode.

[0046] (3) Isolation layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. The isolation layer network was obtained by electrospinning on the prepared PA6 / Au electrode at a flow rate of 0.1mL / h and a voltage of 20kV for 5 minutes.

[0047] (4) Sensitive Layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. The PA6 solution was loaded into a 10mL syringe with a 19G needle and electrospun at a flow rate of 0.1mL / h and a voltage of 20kV for 5 hours to obtain pure PA6 fibers. The fibers were cut to a fixed size for later use. 46μL of aniline was dissolved in 15mL of HCl (concentration of 1.0mol / L) and sonicated in an ice-water bath for 30 minutes to obtain solution A; 57mg of ammonium persulfate was dissolved in 15mL of HCl (concentration of 1.0mol / L) and magnetically stirred in an ice-water bath for 30 minutes to obtain solution B; then, solution B was added to solution A and stirred rapidly until homogeneous. The cut PA6 fiber film was immersed in the mixed solution and allowed to stand for 1.5 hours under light-protected and ice-bath conditions to obtain PA6 fiber sensitive material polymerized with polyaniline.

[0048] (5) The electrodes with the prepared 5-minute isolation layer are cut to a fixed size of 12mm × 12mm, wherein the gold electrode pattern is 4mm wide and 10mm long. A copper wire with a diameter of 0.1mm is fixed as a lead on one side of the electrode with silver paste and dried under a lamp. The prepared PA6 / PANI fiber sensitive material is cut to a fixed size of 6mm × 6mm, and assembled in sequence according to the electrode, sensitive layer, and electrode, wherein the two strip electrodes are placed perpendicular to each other, the sensitive material does not contact the lead, and the sensitive area is 4mm × 4mm. Finally, the three-layer film is fixed to form a sensor by hot pressing.

[0049] Example 2:

[0050] A waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network and its fabrication method are disclosed, comprising the following steps:

[0051] (1) Waterproof layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. 2.5g of PS particles were dissolved in 7.5g of DMF and stirred at room temperature for 12h to obtain a 25wt% PS spinning solution. The PA6 and PS solutions were respectively loaded into 10mL syringes equipped with 19G needles and electrospun synchronously at a flow rate of 0.1mL / h and 0.5mL / h, respectively, at a voltage of 20kV. The distance between the two needles was fixed at 5cm, and the collecting device was placed 16cm away from the two needles. The ambient temperature was controlled at 20℃ and the ambient humidity at 30%RH during the spinning process. After two hours, a PA6 / PS fiber film was obtained and dried at room temperature to allow the solvent to completely evaporate.

[0052] (2) Electrode layer: 1.5 g of PA6 particles were dissolved in 8.5 g of formic acid and stirred at room temperature for 12 h to obtain a 15 wt% PA6 spinning solution. PA6 was electrospun separately on the prepared PS / PA6 fiber film at a flow rate of 0.1 mL / h and a voltage of 20 kV for 1 h to obtain a composite fiber film for preparing the electrode. PA6 / PS fibers were cut to a fixed size and a 100 nm layer of gold was deposited according to a mask pattern to prepare a PA6 / Au electrode.

[0053] (3) Isolation layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. The isolation layer network was obtained by electrospinning on the prepared PA6 / Au electrode at a flow rate of 0.1mL / h and a voltage of 20kV for 10 minutes.

[0054] (4) Sensitive Layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. The PA6 solution was loaded into a 10mL syringe with a 19G needle and electrospun at a flow rate of 0.1mL / h and a voltage of 20kV for 5 hours to obtain pure PA6 fibers. The fibers were cut to a fixed size for later use. 46μL of aniline was dissolved in 15mL of HCl (concentration of 1.0mol / L) and sonicated in an ice-water bath for 30 minutes to obtain solution A; 57mg of ammonium persulfate was dissolved in 15mL of HCl (concentration of 1.0mol / L) and magnetically stirred in an ice-water bath for 30 minutes to obtain solution B; then, solution B was added to solution A and stirred rapidly until homogeneous. The cut PA6 fiber film was immersed in the mixed solution and allowed to stand for 1.5 hours under light-protected and ice-bath conditions to obtain PA6 fiber sensitive material polymerized with polyaniline.

[0055] (5) The electrodes with the prepared 10-minute isolation layer are cut to a fixed size of 12mm × 12mm, wherein the gold electrode pattern is 4mm wide and 10mm long. A copper wire with a diameter of 0.1mm is fixed as a lead on one side of the electrode with silver paste and dried under a lamp. The prepared PA6 / PANI fiber sensitive material is cut to a fixed size of 6mm × 6mm, and assembled in sequence according to the electrode, sensitive layer, and electrode, wherein the two strip electrodes are placed perpendicular to each other, the sensitive material does not contact the lead, and the sensitive area is 4mm × 4mm. Finally, the three-layer film is fixed to form a sensor by hot pressing.

[0056] Example 3:

[0057] A waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network and its fabrication method are disclosed, comprising the following steps:

[0058] (1) Waterproof layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. 2.5g of PS particles were dissolved in 7.5g of DMF and stirred at room temperature for 12h to obtain a 25wt% PS spinning solution. The PA6 and PS solutions were respectively loaded into 10mL syringes equipped with 19G needles and electrospun synchronously at a flow rate of 0.1mL / h and 0.5mL / h, respectively, at a voltage of 20kV. The distance between the two needles was fixed at 5cm, and the collecting device was placed 16cm away from the two needles. The ambient temperature was controlled at 20℃ and the ambient humidity at 30%RH during the spinning process. After two hours, a PA6 / PS fiber film was obtained and dried at room temperature to allow the solvent to completely evaporate.

[0059] (2) Electrode layer: 1.5 g of PA6 particles were dissolved in 8.5 g of formic acid and stirred at room temperature for 12 h to obtain a 15 wt% PA6 spinning solution. PA6 was electrospun separately on the prepared PA6 / PS fiber film at a flow rate of 0.1 mL / h, a rotation speed of 500 r, and a voltage of 20 kV for 1 hour to obtain a composite fiber film for preparing the electrode. The PS / PA6 fibers were cut to a fixed size and a 100 nm layer of gold was deposited according to a mask pattern to prepare a PA6 / Au electrode.

[0060] (3) Isolation layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. The isolation layer network was obtained by electrospinning on the prepared PA6 / Au electrode at a flow rate of 0.1mL / h and a voltage of 20kV for 15 minutes.

[0061] (4) Sensitive Layer: 1.5g of PA6 particles were dissolved in 8.5g of formic acid and stirred at room temperature for 12h to obtain a 15wt% PA6 spinning solution. The PA6 solution was loaded into a 10mL syringe with a 19G needle and electrospun at a flow rate of 0.1mL / h and a voltage of 20kV for 5 hours to obtain pure PA6 fibers. The fibers were cut to a fixed size for later use. 46μL of aniline was dissolved in 15mL of HCl (concentration of 1.0mol / L) and sonicated in an ice-water bath for 30 minutes to obtain solution A; 57mg of ammonium persulfate was dissolved in 15mL of HCl (concentration of 1.0mol / L) and magnetically stirred in an ice-water bath for 30 minutes to obtain solution B; then, solution B was added to solution A and stirred rapidly until homogeneous. The cut PA6 fiber film was immersed in the mixed solution and allowed to stand for 1.5 hours under light-protected and ice-bath conditions to obtain PA6 fiber sensitive material polymerized with polyaniline.

[0062] (5) The electrodes with the prepared 15-minute isolation layer were cut to a fixed size of 12mm × 12mm, with the gold electrode pattern being 4mm wide and 10mm long. A 0.1mm diameter copper wire was fixed as a lead on one side of the electrode using silver paste and dried under a lamp. The prepared PA6 / PANI fiber sensitive material was cut to a fixed size of 6mm × 6mm and assembled in sequence according to the electrode, sensitive layer, and electrode. The two strip electrodes were placed perpendicular to each other, and the sensitive material did not contact the lead. The sensitive area was 4mm × 4mm. Finally, the three thin films were fixed together to form the sensor using a hot pressing process.

Claims

1. A method for fabricating a waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network, comprising the following steps: (1) Preparation of waterproof layer PA6 spinning solution and PS spinning solution were respectively loaded into 10 mL syringes with 19 G needles, and electrospun synchronously on the same collection device for 1.5 to 3.0 h at a voltage of 18 to 25 kV; then PA6 / PS fiber waterproof layer was obtained on the collection device and dried at room temperature to allow the solvent to evaporate completely. (2) Electrode preparation The PA6 spinning solution was loaded into a 10 mL syringe with a 19 G needle, and electrospun on the surface of the PA6 / PS fiber waterproof layer obtained in step (1) at a voltage of 18~25 kV for 1~2 h to obtain a composite fiber film; then Au with a thickness of 80~120 nm was deposited according to the electrode mask pattern to prepare a PA6 / Au flexible electrode layer on the PA6 / PS fiber waterproof layer. (3) Preparation of isolation layer The PA6 spinning solution was loaded into a 10 mL syringe with a 19 G needle, and electrospun on the PA6 / Au flexible electrode layer obtained in step (2) at a voltage of 18~25 kV for 5~15 min, thereby obtaining a pure PA6 fiber isolation layer on the PA6 / Au flexible electrode layer. (4) Preparation of sensitive layer ① The PA6 spinning solution was loaded into a 10 mL syringe with a 19 G needle, and electrospun at a voltage of 18~25 kV for 4~6 h to obtain a PA6 fiber membrane. ② Dissolve 46 µL of aniline in 15 mL of 0.8~1.2 mol / L HCl and sonicate in an ice-water bath for 20~40 minutes to obtain solution A; dissolve 57 mg of ammonium persulfate in 15 mL of 0.8~1.2 mol / L HCl and magnetically stir in an ice-water bath for 20~40 minutes to obtain solution B; then, add solution B to solution A and stir rapidly until homogeneous; then immerse the PA6 fiber membrane obtained in step ① into the mixed solution and let it stand for 1~2 h under light-protected and ice-bath conditions to obtain a PA6 / PANI fiber sensitive layer polymerized with polyaniline; (5) Sensor fabrication ① Cut the PA6 / PS fiber waterproof layer-PA6 / Au fiber flexible electrode layer-pure PA6 fiber isolation layer to a size of 12 mm×12 mm, wherein the size of the Au electrode is 4 mm×10 mm. Fix a copper wire with a diameter of 0.1 mm as a lead wire on one side of the wide side of the Au electrode with silver paste and dry it. ② Cut the PA6 / PANI fiber sensitive layer to a size of 6 mm × 6 mm, and assemble them in the following order: PA6 / PS fiber waterproof layer - PA6 / Au flexible electrode layer - pure PA6 fiber isolation layer - PA6 / PANI fiber sensitive layer - pure PA6 fiber isolation layer - PA6 / Au flexible electrode layer - PS / PA6 fiber waterproof layer. The two strip-shaped Au electrodes in the two PA6 / Au flexible electrode layers are arranged perpendicular to each other. The PA6 / PANI fiber sensitive layer does not contact the silver paste lead. Finally, the film is pressed and fixed by hot pressing process to obtain the flexible resistive pressure sensor.

2. The method for fabricating a waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network as described in claim 1, characterized in that: The PA6 spinning solution is obtained by dissolving 1.5 g of PA6 particles in 4.5~13.5 g of formic acid and stirring at room temperature for 10~15 h; the PS spinning solution is obtained by dissolving 2.5 g of PS particles in 5~10 g of DMF and stirring at room temperature for 10~15 h.

3. The method for fabricating a waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network as described in claim 1, characterized in that: The spinning flow rate of the PA6 spinning solution is 0.1 mL / h, and the spinning flow rate of the PS spinning solution is 0.5 mL / h.

4. The method for fabricating a waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network as described in claim 1, characterized in that: The distance between the two needles in the electrospinning process is fixed at 5 cm, and the collecting device is placed 10-20 cm away from the two needles. The ambient temperature is controlled at 18-22℃ and the ambient humidity is controlled at 25-35%RH during the spinning process.

5. A waterproof and breathable flexible resistive pressure sensor based on a PA6 all-fiber network, characterized in that: It is prepared by the method described in any one of claims 1 to 4.

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