Wide stress fully linear flexible capacitive sensor and preparation method thereof

Abstract

The application provides a wide stress full-linearity flexible ion-dissociation sensor and a preparation method thereof, which comprises a heat-shrinkable film material layer, a flexible AgNWs / MXene electrode, and a dielectric layer, the dielectric layer is attached between the two flexible AgNWs / MXene electrodes, and the two flexible AgNWs / MXene electrodes are provided with corresponding heat-shrinkable film material layers. The electrode of the application adopts the AgNWs / MXene composite electrode with good mechanical properties, the AgNWs microelectrode provides a conductive framework, and the MXene plays a role in protecting the AgNWs from oxidation and corrosion and providing a pseudo-capacitance; the application is based on the ion-dissociation effect of the ion gel film, uses the ion gel film with a porous microstructure as the dielectric layer, so that the dielectric layer has a larger deformable surface area and provides a larger deformation capacity, is thousands of times of the traditional solid-state similar sensor, and makes the ion-dissociation sensor have better linearity, higher sensitivity and faster response speed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a wide stress full-linear flexible capacitive sensor applicable to underwater and a preparation method thereof. BACKGROUND

[0002] With the vigorous development of artificial intelligence, Internet of Things, medical health and wearable electronics, flexible pressure sensors as an important component of human-computer interface have also ushered in vigorous development, and wearable electronic devices have shown great market prospects. Compared with pressure sensors based on optical signal measurement, electronic pressure sensors have the advantages of good flexibility, simple structure, easy integration and direct signal conversion, and have become the preferred sensing mode of flexible electronics.

[0003] Wearable flexible sensors have a wide range of applications in human-computer interaction, medical health and underwater monitoring. Developing a high-sensitivity, wide-stress working range and full-linear waterproof pressure sensor is a key scientific problem that researchers need to solve urgently.

[0004] Common electronic pressure sensors can be divided into four types: resistance type, capacitance type, piezoelectric type and triboelectric type. The piezoelectric and triboelectric electronic pressure sensors can only be applied to dynamic load, while the resistance type pressure sensor is easily disturbed by temperature and water. Capacitive sensors are deeply studied due to their simple manufacturing, good anti-interference and excellent long-term stability.

[0005] However, traditional capacitive sensors often exhibit low sensitivity under a larger working pressure, and the capacitance value of traditional parallel plate capacitors is only tens of picofarads, so the human body capacitance (up to hundreds of picofarads) and other parasitic noise sources (usually tens of picofarads) have a great influence on the accuracy and stability of the device. At present, one of the effective strategies to improve the performance of capacitive sensors is to introduce compressible microstructures in the dielectric layer or the electrode layer, because the effective compression distance d of the device is increased, which makes the capacitance (C = εS / d) rapidly increase in the low pressure range (~ several thousand pascals), thereby improving the sensitivity of the device (S = ΔC / C0P). However, due to the limited compression range of the microstructure, the sensitivity of the traditional capacitive sensor is low, and it shows low resolution under high pressure. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a wide stress full-linear flexible capacitive sensor and a preparation method thereof.

[0007] The technical scheme of the present application is: a wide stress full-linearity flexible capacitive sensor, the sensor comprising a heat-shrinkable film material layer, a flexible AgNWs / MXene electrode, a dielectric layer, the dielectric layer being attached between the two flexible AgNWs / MXene electrodes, and the two flexible AgNWs / MXene electrodes being provided with corresponding heat-shrinkable film material layers, and the conductive wires of the two flexible AgNWs / MXene electrodes being led out by silver paste and copper wires with an insulating layer.

[0008] The present application also provides a preparation method of a wide stress full-linearity flexible capacitive sensor, comprising the following steps:

[0009] S1), pretreatment of the base material

[0010] The cut base material is sequentially subjected to ultrasonic treatment in deionized water, ethanol and isopropanol solution, constant temperature drying, and then plasma pretreatment to obtain a hydrophilic support flexible base material;

[0011] S2), preparation of conductive nanomaterial

[0012] A certain amount of glucose, silver nitrate, ferrous sulfate and PVP are added to a hydrothermal kettle to prepare silver nanowires AgNWs by hydrothermal method, and the AgNWs are treated again with NaCl to remove PVP to obtain good conductive AgNWs;

[0013] S3), preparation of MXene material

[0014] A certain amount of concentrated hydrochloric acid, deionized water and LiF are used to etch Ti3AlC2, and after washing with deionized water and ultrasonic treatment, single-layer or few-layer MXene material is obtained;

[0015] S4), preparation of flexible electrode

[0016] A certain amount of AgNWs is coated on the cleaned PET substrate using the bar coating method until a flexible PET / AgNWs electrode with a square resistance of 10Ω / sq is obtained;

[0017] The coated PET / AgNWs electrode is soaked in the MXene solution and then dried, and the process is repeated for 3-5 times, and then the fine copper wire with an insulating layer is led out by silver;

[0018] S5), preparation of ion dielectric layer with microstructure and micropore

[0019] A certain amount of PVA, phosphoric acid and deionized water solution is mixed and quickly heated and stirred to prepare a multi-bubble ion gel solution, which is then uniformly coated on a PDMS mold with a semicircle, and then dried at a constant temperature to obtain an ion gel dielectric layer with microstructure and micropore;

[0020] S6), the ion gel dielectric layer is pasted between the two flexible AgNWs / MXene electrodes to form an ionic sensor, the dead zone is sealed with UV glue to form a waterproof layer, and the sensor is packaged again with a heat shrink film, thereby obtaining a high-sensitivity and wide-linearity ionic sensor with good waterproof performance.

[0021] Preferably, in step S1), the substrate material is ultrasonically cleaned with deionized water, ethanol, and isopropanol for 10 minutes, and then cleaned in a plasma cleaning machine for 15 minutes.

[0022] Preferably, in step S2), the molar ratio of glucose, silver nitrate, ferric sulfate, and polyvinylpyrrolidone (K30) is about 2:1.5:0.3:0.01-0.2.

[0023] Preferably, in step S2), the preparation of the conductive nanomaterial is as follows:

[0024] S21), 1.5 mmol of silver nitrate and 2 mmol of glucose are dissolved in a beaker at room temperature;

[0025] S22), 0.3 mmol of ferric sulfate is added, and magnetic stirring is performed for 30 minutes to obtain a light yellow solution;

[0026] S23), 4.5 g of polyvinylpyrrolidone (K30) is added to the solution;

[0027] S24), the uniformly mixed solution is transferred to a 100 mL capacity autoclave, sealed, and heated at 180°C for 6 hours;

[0028] S25), after cooling, the solution is washed several times with deionized water until it becomes transparent, and then 0-0.02 mol of NaCl is added to remove the PVP on the surface of the AgNWs; after 2 hours, the AgNWs are obtained by centrifugal washing with deionized water for 3 times.

[0029] Preferably, in step S3), the molar ratio of concentrated hydrochloric acid, deionized water, and LiF is 1.7:1-3:0.3.

[0030] Preferably, in step S3), the preparation of the MXene material is as follows:

[0031] S31), 5 ml of deionized water is added to 15 ml of concentrated hydrochloric acid, and then the prepared solution is poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC2 are sequentially added;

[0032] S32), the container is placed in a magnetic heating stirrer at 35°C and 550 rpm for etching for 35 h.

[0033] S33), after etching, multiple centrifugal cleaning with deionized water until the solution ph≥6, followed by ultrasonic treatment for 2 hours in a nitrogen environment, and finally a single-layer or few-layer MXene solution is obtained.

[0034] As preferred, in step S5), the concentration of the phosphoric acid solution is 85%.

[0035] As preferred, in step S5), the weight ratio of PVA, phosphoric acid and deionized water is 2:0.5-3:18.

[0036] As preferred, in step S5), after pouring the prepared ionic gel solution into the PDMS mold, heating at 50℃ for 0.5-2h to solidify the ionic gel film.

[0037] The beneficial effects of the present application are:

[0038] 1. The electrode of the present application adopts an AgNWs and MXene composite electrode with good mechanical properties, the AgNWs microelectrode provides a conductive skeleton, and the MXene plays a role in protecting the AgNWs from oxidation and corrosion and providing a pseudo-capacitance;

[0039] 2. Based on the ion gel film, the present application utilizes the porous microstructure of the ion gel film as the dielectric layer to obtain a larger deformable surface area and provide greater deformation capacity, which is thousands of times that of traditional solid-state sensors of the same type, and the ion sensing linearity is better, the sensitivity is higher, and the response speed is faster;

[0040] 3. The present application uses copper wire with an insulating layer as the lead wire, uses UV glue to seal the edges to isolate the device from air, and uses heat shrink tape for re-packaging to obtain a sensor with good waterproof performance;

[0041] 4. The process provided by the present application is simple to operate, and the electrode material, flexible electrode and dielectric layer are all prepared by solution method, which has the advantages of low cost and high scalability. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is the structure diagram of the sensor of embodiment 1 of the present application;

[0043] 1-heat shrink film material layer; 2-flexible PET / AgNWs / MXene electrode; 3-dielectric layer;

[0044] Figure 2 is the microstructure diagram of the ionic gel prepared in embodiments 2-4 of the present application, wherein, Figure 2(a) is a microstructure diagram of the microporous ionogel film of Example 2; Figure 2 (b) is a microstructure diagram of the microstructured ionogel film of Example 3; Figure 2 (c) is a microstructure diagram of the microporous ionogel film of Example 4;

[0045] Figure 3 This is a sensitivity comparison chart of the sensors prepared in Examples 2-4 of the present invention;

[0046] Figure 4 This is a schematic diagram of the PET / AgNWs / MXene electrode and the microstructured microporous ion gel thin film sensor of Embodiment 2 of the present invention;

[0047] Figure 5 The graph shows the performance of the response and recovery capabilities of the sensor prepared in Example 2 of this invention. Detailed Implementation

[0048] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0049] Example 1

[0050] like Figure 1 As shown, this embodiment provides the fabrication and packaging of a wide-stress, fully linear, flexible ionized electrode sensor. The sensor includes a heat-shrinkable film material layer 1, a flexible AgNWs / MXene electrode 2, and a dielectric layer 3. The dielectric layer 3 is attached between two flexible AgNWs / MXene electrodes 2, and corresponding heat-shrinkable film material layers 1 are disposed on the two flexible AgNWs / MXene electrodes 2. The conductive lines of the two flexible AgNWs / MXene electrodes 2 are led out with silver paste to form the fine copper wires of the insulating layer.

[0051] Example 2

[0052] This embodiment provides a method for fabricating a wide-stress, fully linear, flexible ionization sensor, including the following steps:

[0053] S1) Substrate material pretreatment

[0054] The PET film was cut into 5×5cm size. The cut PET substrate material was first placed in deionized water and ultrasonically treated for 10 minutes. Then it was placed in ethanol and isopropanol solutions and ultrasonically treated for 10 minutes in sequence. After treatment, the PET was placed in a constant temperature oven at 60℃ to dry. Finally, it was placed in the cavity of a plasma treatment machine and plasma treated in air environment for 15 minutes to obtain a hydrophilic PET flexible substrate.

[0055] S2) Preparation of conductive nanomaterials

[0056] S21), 1.5 mmol of silver nitrate and 2 mmol of glucose were dissolved in a beaker at room temperature;

[0057] S22), 0.3 mmol of ferric sulfate was added, and magnetic stirring was performed for 30 minutes to obtain a light yellow solution;

[0058] S23), 4.5 g of polyvinylpyrrolidone was introduced into the solution;

[0059] S24), the uniformly mixed solution was transferred to a 100 mL capacity autoclave, sealed and heated at 180°C for 6 hours;

[0060] S25), after cooling, the solution was directly washed with deionized water until the solution became transparent, and then 1 g of NaCl was added to remove the PVP on the surface of the AgNWs; after 2 hours, the AgNWs were obtained by centrifugal washing with deionized water for 3 times.

[0061] S3), preparation of MXene material

[0062] S31), 5 ml of deionized water was added to 15 ml of concentrated hydrochloric acid, and then the prepared solution was poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC2 were added in sequence;

[0063] S32), the container was placed in a magnetic heating stirrer at 35°C and 550 rpm for etching for 35 h;

[0064] S33), after the etching was completed, the solution was washed with deionized water by centrifugation for multiple times until the solution pH≥6, then the etched solution was transferred to a three-necked flask, and then ultrasonic treatment was performed in a nitrogen environment at room temperature for 2 h, and finally a single-layer or few-layer MXene solution was obtained.

[0065] S4), preparation of flexible electrode

[0066] 5 mg / ml of AgNWs were coated on the cleaned PET substrate using the bar coating method until a flexible PET / AgNWs electrode with a square resistance of 10 Ω / sq was obtained;

[0067] The coated PET / AgNWs electrode was immersed in the MXene solution and then dried, and the process was repeated for 5 times, and then a fine copper wire was led out from the insulating layer using a silver award;

[0068] S5), preparation of ion dielectric layer with microstructure and micropore

[0069] 2g PVA was mixed with 18g deionized water in a 100ml beaker and heated with rapid stirring at 500rpm in a 90℃ oil bath for 2h, then 1.6ml phosphoric acid was added and transferred to a 60℃ heating stirrer to continue rapid stirring at 500rpm for 2h, after the heating time, the multi-foam gel was poured into a pre-prepared micro-groove PDMS mold and dried in a 50℃ constant temperature oven, obtaining an ionic gel dielectric layer with microstructure and micropores;

[0070] S6), the ionic gel dielectric layer with microstructure and micropores was pasted between two flexible AgNWs / MXene electrodes to form an off-electric sensor, which was packaged with UV glue to form a waterproof layer, and the sensor was packaged again with a heat shrink film, thereby obtaining a high-sensitivity wide-linear off-electric sensor with good waterproof performance.

[0071] Example 3

[0072] The present embodiment provides a preparation method of a wide-stress full-linear flexible off-electric sensor, comprising the following steps:

[0073] S1), substrate material pretreatment

[0074] PET film was cut into a size of 5x5cm, and the cut PET substrate material was first placed in deionized water for ultrasonic treatment for 10min; then it was sequentially placed in ethanol and isopropanol solution for ultrasonic treatment for 10min, and the treated PET was placed in a constant temperature oven at 60℃ for drying, and finally it was placed in the cavity of a plasma treatment machine for plasma treatment in an air environment for 15min, obtaining a hydrophilic PET flexible substrate;

[0075] S2), preparation of conductive nanomaterial

[0076] S21), 1.5mmol silver nitrate and 2mmol glucose were dissolved in a beaker at room temperature;

[0077] S22), 0.3mmol ferric sulfate was added and magnetically stirred for 30min to obtain a light yellow solution;

[0078] S23), 4.5g polyvinylpyrrolidone (K30) was introduced into the solution;

[0079] S24), the uniformly mixed solution was transferred to a 100ml capacity autoclave, sealed and heated at 180℃ for 6h;

[0080] S25), after cooling, the solution was washed several times with deionized water until it became transparent, then 1g NaCl was added to remove the PVP on the surface of the AgNWs; after 2h, the AgNWs were obtained by centrifugal washing with deionized water for 3 times.

[0081] S3) Preparation of MXene material

[0082] S31) 5ml of deionized water was added to 15ml of concentrated hydrochloric acid, and then the prepared solution was poured into a polytetrafluoroethylene reaction container, and then 1.6g of LiF and 1g of Ti3ALC2 were sequentially added;

[0083] S32) The container was placed in a magnetic heating stirrer at 35°C and 550rpm for etching for 35h;

[0084] S33) After etching, the solution was washed with deionized water by centrifugation until the solution pH≥6, then the etched solution was transferred to a three-necked flask, and then ultrasonic was performed under nitrogen atmosphere at room temperature for 2h, and finally a single-layer or few-layer MXene solution was obtained.

[0085] S4) Preparation of flexible electrode

[0086] 5mg / ml of AgNWs was coated on the cleaned PET substrate by using the method of rod coating until a flexible PET / AgNWs electrode with a square resistance of 10Ω / sq was obtained;

[0087] The coated PET / AgNWs electrode was immersed in 5mg / ml of MXene solution and then dried, and the process was repeated for 5 times, and then a thin copper wire of the insulating layer was led out with a silver award;

[0088] S5) Preparation of ion dielectric layer with microstructure

[0089] 2g of PVA was mixed with 18g of deionized water in a 100ml beaker, and heated in a 90°C oil bath at a stirring speed of 100rpm for 2h, then 1.6ml of phosphoric acid was added and transferred to a 60°C heating stirrer and continued to be heated at a stirring speed of 100rpm for 2h, after the heating time, the foam-free gel was poured into a pre-prepared micro-groove PDMS mold and dried at room temperature to obtain an ion gel dielectric layer with microstructure;

[0090] S6) The ion gel dielectric layer with microstructure was attached between two flexible AgNWs / MXene electrodes to form an iontophoretic sensor, UV glue was used to seal the dead to form a waterproof layer, and a heat shrinkable film was used to encapsulate the sensor again, thereby obtaining a high-sensitivity iontophoretic sensor with good waterproof performance.

[0091] Example 4

[0092] The embodiment provides a preparation method of a wide-stress full-linear flexible iontophoretic sensor, comprising the following steps:

[0093] S1) Substrate material pretreatment

[0094] PET film is cut into a size of 5x5cm, and the cut PET base material is first placed in deionized water for ultrasonic treatment for 10 min; then it is sequentially placed in ethanol and isopropanol solution for ultrasonic treatment for 10 min, and the treated PET is placed in a constant temperature oven at 60°C for drying, and finally it is placed in the cavity of a plasma treatment machine for plasma treatment for 15 min in an air environment to obtain a hydrophilic PET flexible substrate;

[0095] S2), preparation of conductive nanomaterial

[0096] S21), 1.5 mmol of silver nitrate and 2 mmol of glucose are dissolved in a beaker at room temperature;

[0097] S22), 0.3 mmol of ferric sulfate is added, and magnetic stirring is performed for 30 minutes to obtain a light yellow solution;

[0098] S23), 4.5 g of polyvinylpyrrolidone (K30) is added to the solution;

[0099] S24), the uniformly mixed solution is transferred to a 100 mL capacity autoclave, sealed and heated at 180°C for 6 hours;

[0100] S25), after cooling, multiple washing with deionized water is performed until the solution appears transparent, and then 1 g of NaCl is added to remove the PVP on the surface of the AgNWs; after 2 hours, 3 times of centrifugal washing with deionized water is performed to obtain AgNWs.

[0101] S3), preparation of MXene material

[0102] S31), 5 ml of deionized water is added to 15 ml of concentrated hydrochloric acid, and then the prepared solution is poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC2 are sequentially added;

[0103] S32), the container is placed in a magnetic heating stirrer at 35°C and 550 rpm for etching for 35 h;

[0104] S33), after the etching is completed, multiple centrifugal washing with deionized water is performed until the solution ph≥6, and then the etched solution is transferred to a three-necked flask, and then ultrasonic treatment is performed in a nitrogen environment at room temperature for 2 h, and finally a single-layer or few-layer MXene solution is obtained.

[0105] S4), preparation of flexible electrode

[0106] The method of bar coating is used to coat 5 mg / ml of AgNWs on the cleaned PET substrate until a flexible PET / AgNWs electrode with a square resistance of 10Ω / sq is obtained;

[0107] The coated PET / AgNWs electrode is immersed in a 5mg / ml MXene solution and then dried, repeated 5 times, and then the fine copper wire of the insulating layer is led out with a silver award;

[0108] S5), preparation of an ionic dielectric layer with micropores

[0109] 2g of PVA is mixed with 18g of deionized water in a 100ml beaker and heated in a 90°C oil bath with rapid stirring at 500rpm for 2h, then 1.6ml of phosphoric acid is added and transferred to a 60°C heating stirrer for continuous rapid stirring at 500rpm for 2h, after the heating time, the foam gel is poured into a pre-prepared microstructure-free PDMS mold and dried in a 50°C constant temperature oven, obtaining an ionic gel dielectric layer with micropores;

[0110] S6), the ionic gel dielectric layer with micropores is attached between the two flexible AgNWs / MXene electrodes to form an ionic sensor, the dead are sealed with ultraviolet UV glue to form a waterproof layer, and the sensor is packaged again with a heat shrink film, thereby obtaining a high-sensitivity wide-linear ionic sensor with good waterproof performance.

[0111] The above examples and descriptions described in the specification are only to illustrate the principles and best embodiments of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed application.

[0112] Example 5

[0113] The present embodiment provides a preparation method of a wide-stress full-linear flexible ionic sensor, comprising the following steps:

[0114] S1), substrate material pretreatment

[0115] The PET film is cut into a size of 5x5cm, and the cut PET substrate material is first placed in deionized water for ultrasonic treatment for 10min; then placed in ethanol and isopropanol solution for ultrasonic treatment for 10min, the treated PET is placed in a constant temperature oven at 60°C for drying, and finally placed in the cavity of a plasma treatment machine for plasma treatment in air for 15min, obtaining a hydrophilic PET flexible substrate;

[0116] S2), preparation of conductive nanomaterial

[0117] S21), 1.5mmol of silver nitrate and 2mmol of glucose are dissolved in a beaker at room temperature;

[0118] S22), 0.3mmol of ferric sulfate is added, and magnetic stirring is performed for 30min to obtain a light yellow solution;

[0119] S23), 4.5 g of polyvinylpyrrolidone (K30) was added to the solution;

[0120] S24), the uniformly mixed solution was transferred to a 100 mL capacity autoclave, sealed and heated at 180°C for 6 hours;

[0121] S25), after cooling, multiple washing was performed using deionized water until the solution appeared transparent, then 1 g of NaCl was added to remove the PVP on the surface of the AgNWs; after 2 hours, 3 times of centrifugal washing was performed using deionized water, and AgNWs were obtained.

[0122] S3), preparation of MXene material

[0123] S31), 5 ml of deionized water was added to 15 ml of concentrated hydrochloric acid, then the prepared solution was poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC2 were sequentially added;

[0124] S32), the container was placed in a magnetic heating stirrer at 35°C and 550 rpm for etching for 35 h;

[0125] S33), after the etching was completed, multiple centrifugal washing was performed using deionized water until the solution ph≥6, then the etched solution was transferred to a three-necked flask, and then ultrasonic treatment was performed in a nitrogen environment at room temperature for 2 h, and finally a single-layer or few-layer MXene solution was obtained.

[0126] S4), preparation of flexible electrode

[0127] 5 mg / ml of AgNWs was coated on the cleaned PET substrate using a bar coating method until a flexible PET / AgNWs electrode with a square resistance of 10 Ω / sq was obtained;

[0128] The coated PET / AgNWs electrode was immersed in 5 mg / ml of MXene solution and then dried, and the process was repeated 5 times, and then a fine copper wire of the insulating layer was led out using a silver award;

[0129] S5), preparation of ion dielectric layer with microstructure and micropore

[0130] 2 g of PVA and 18 g of deionized water were mixed in a 100 ml beaker, and heated at 90°C in an oil bath at 500 rpm for 2 h, then 0.8 ml of phosphoric acid was added and transferred to a 60°C heating stirrer for continued rapid stirring at 500 rpm for 2 h, and after the heating time, the foam gel was poured into a previously prepared microstructure and micropore PDMS mold, and dried in a constant temperature oven at 50°C, to obtain an ion gel dielectric layer with microstructure and micropore;

[0131] S6), the ion gel dielectric layer with microstructure and micropore is pasted between the two flexible AgNWs / MXene electrodes to form an ionic sensor, the dead zone is sealed with UV glue to form a waterproof layer, and the sensor is packaged again with heat shrink film, thereby obtaining a high-sensitivity wide-linear ionic sensor with good waterproof performance. The sensitivity is also relatively reduced due to the reduction of the concentration of the ionic liquid phosphoric acid.

[0132] Example 6

[0133] The embodiment provides a preparation method of a wide-stress full-linear flexible ionic sensor, comprising the following steps:

[0134] S1), substrate material pretreatment

[0135] PET film is cut into a size of 5*5 cm, the cut PET substrate material is first placed in deionized water for ultrasonic treatment for 10 min; then sequentially placed in ethanol and isopropanol solution for ultrasonic treatment for 10 min, the treated PET is placed in a constant temperature oven at 60°C for drying, and finally placed in the cavity of a plasma treatment machine for plasma treatment in an air environment for 15 min, to obtain a hydrophilic PET flexible substrate;

[0136] S2), preparation of conductive nanomaterial

[0137] S21), 1.5 mmol of silver nitrate and 2 mmol of glucose are dissolved in a beaker at room temperature;

[0138] S22), 0.3 mmol of ferric sulfate is added, and magnetic stirring is performed for 30 minutes to obtain a light yellow solution;

[0139] S23), 4.5 g of polyvinylpyrrolidone (K30) is added to the solution;

[0140] S24), the uniformly mixed solution is transferred to a 100 mL capacity autoclave, sealed and heated at 180°C for 6 hours;

[0141] S25), after cooling, multiple washing is performed with deionized water until the solution presents a transparent color, and then 1 g of NaCl is added to remove the PVP on the surface of the AgNWs; after 2 hours, 3 times of centrifugal washing is performed with deionized water, to obtain AgNWs.

[0142] S3), preparation of MXene material

[0143] S31), 5 ml of deionized water is added to 15 ml of concentrated hydrochloric acid, then the prepared solution is poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC2 are sequentially added;

[0144] S32), put the container in a magnetic heating stirrer at 35℃, 550rpm for 35h;

[0145] S33), after etching, wash the solution with deionized water by centrifugation for several times until the solution pH≥6, then transfer the etched solution to a three-necked flask, and then ultrasonic in normal temperature for 2h under nitrogen atmosphere, finally get the single-layer or few-layer MXene solution.

[0146] S4), preparation of flexible electrode

[0147] Use the method of bar coating to coat 5mg / ml of AgNWs on the cleaned PET substrate until the flexible PET / AgNWs electrode with sheet resistance of 10Ω / sq is obtained;

[0148] Soak the coated PET / AgNWs electrode in 5mg / ml MXene solution and then dry, repeat for 5 times, then use silver wire to lead out the insulating layer of fine copper wire;

[0149] S5), preparation of ion dielectric layer with microstructure and micropore

[0150] Mix 2g of PVA with 18g of deionized water in a 100ml beaker, and heat in a 90℃ oil bath with 500rpm fast stirring for 2h, then add 0.4ml of phosphoric acid and transfer to a 60℃ heating stirrer for continuous 500rpm fast stirring and heating for 2h, after the heating time, pour the foam gel into the previously prepared microstructure and micropore PDMS mold, and dry in a 50℃ constant temperature oven, to obtain an ion gel dielectric layer with microstructure and micropore;

[0151] S6), paste the ion gel dielectric layer with microstructure and micropore between two flexible AgNWs / MXene electrodes to form an iontophoretic sensor, use ultraviolet UV glue to seal the dead to form a waterproof layer, and use heat shrink film to package the sensor again, to obtain a high-sensitivity wide-linearity iontophoretic sensor with good waterproof performance. Due to the decrease of the concentration of ionic liquid phosphoric acid, the sensitivity is also relatively reduced.

[0152] Example 7

[0153] The embodiment provides a preparation method of a wide-stress full-linear flexible iontophoretic sensor, comprising the following steps:

[0154] S1), substrate material pretreatment

[0155] PET film is cut into 5x5cm size, and the cut PET substrate is first placed in deionized water for ultrasonic treatment for 10min; then it is placed in ethanol and isopropanol solution for ultrasonic treatment for 10min, respectively; the treated PET is placed in a constant temperature oven at 60℃ for drying, and finally it is placed in the cavity of the plasma treatment machine for plasma treatment for 15min in air environment to obtain a hydrophilic PET flexible substrate;

[0156] S2), preparation of conductive nanomaterials

[0157] S21), 1.5mmol of silver nitrate and 2mmol of glucose are dissolved in a beaker at room temperature;

[0158] S22), 0.3mmol of ferric sulfate is added, and magnetic stirring is performed for 30min to obtain a light yellow solution;

[0159] S23), 9g of polyvinylpyrrolidone (K30) is added to the solution;

[0160] S24), the uniformly mixed solution is transferred to a 100mL capacity autoclave, sealed and heated at 180℃ for 6h;

[0161] S25), after cooling, multiple centrifugal washing is performed using deionized water until the solution shows a transparent color. Then 0.1g of NaCl is added to remove the PVP on the surface of the AgNWs; after 2h, 3 times of centrifugal washing is performed using deionized water to obtain AgNWs.

[0162] S3), preparation of MXene material

[0163] S31), 5ml of deionized water is added to 15ml of concentrated hydrochloric acid, and then the prepared solution is poured into a polytetrafluoroethylene reaction container, and then 1.6g of LiF and 1g of Ti3ALC2 are added in sequence;

[0164] S32), the container is placed in a magnetic heating stirrer at 35℃ and 550rpm for etching for 35h;

[0165] S33), after etching, multiple centrifugal washing is performed using deionized water until the solution ph≥6, and then the etched solution is transferred to a three-necked flask, and then ultrasonic treatment is performed in a nitrogen environment at room temperature for 2h, and finally a single-layer or few-layer MXene solution is obtained.

[0166] S4), preparation of PET / AgNWs flexible electrode

[0167] 5mg / ml of AgNWs is coated on the cleaned PET substrate using a bar coating method, and due to the reason that PVA is not removed completely; the conductivity of the electrode is poor.

[0168] The coated PET / AgNWs electrode is immersed in a 5mg / ml MXene solution and then dried, repeated 5 times, and then a thin copper wire insulated layer is led out with a silver award;

[0169] S5), preparation of an ionic dielectric layer with microstructure and micropores

[0170] 2g of PVA was mixed with 18g of deionized water in a 100ml beaker and heated at 90℃ in an oil bath with rapid stirring at 500rpm for 2h, then 0.8ml of phosphoric acid was added and transferred to a 60℃ heating stirrer for continuous rapid stirring at 500rpm for 2h, after the heating time, the foam gel was poured into a previously prepared microstructure and microporous PDMS mold, and dried in a constant temperature oven at 50℃, obtaining an ionic gel dielectric layer with microstructure and micropores;

[0171] S6), the ionic gel dielectric layer with microstructure and micropores is attached between the two flexible AgNWs / MXene electrodes to form an EDL sensor, the dead are sealed with UV glue to form a waterproof layer, and the sensor is packaged again with heat shrink film, thus obtaining an EDL sensor with good waterproof performance. Due to the poor conductivity of the electrode, the electrostatic interaction between the electrode and the dielectric layer is reduced, resulting in a decrease in the EDL of the nanolayer, thus the sensor has low sensitivity.

[0172] Example 8

[0173] The present embodiment provides a preparation method of a wide-stress full-linear flexible EDL sensor, comprising the following steps:

[0174] S1), substrate material pretreatment

[0175] The PET film is cut into a size of 5x5cm, and the cut PET substrate material is first placed in deionized water for ultrasonic treatment for 10min; then placed in ethanol and isopropanol solution for ultrasonic treatment for 10min, respectively, the treated PET is placed in a constant temperature oven at 60℃ for drying, and finally placed in the cavity of a plasma treatment machine for plasma treatment in an air environment for 15min, obtaining a hydrophilic PET flexible substrate;

[0176] S2), preparation of conductive nanomaterial

[0177] S21), 1.5mmol of silver nitrate and 2mmol of glucose are dissolved in a beaker at room temperature;

[0178] S22), 0.3mmol of ferric sulfate is added, and magnetic stirring is carried out for 30min to obtain a light yellow solution;

[0179] S23), 4.5g of polyvinylpyrrolidone is introduced into the solution;

[0180] S24), the uniformly mixed solution was transferred to a 100 mL capacity autoclave, sealed and heated at 180°C for 6 hours;

[0181] S25), after cooling, the direct solution was washed several times with deionized water until it became transparent, then 1 g of NaCl was added to remove the PVP on the surface of the AgNWs; after 2 hours, the AgNWs were obtained by centrifugal washing with deionized water for 3 times.

[0182] S3), preparation of MXene material

[0183] S31), 10 ml of deionized water was added to 15 ml of concentrated hydrochloric acid, then the prepared solution was poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC2 were added in turn;

[0184] S32), the container was placed in a magnetic heating stirrer at 35°C and 550 rpm for etching for 35 h;

[0185] S33), after etching, the solution was washed several times with deionized water until the pH of the solution was ≥6, then the etched solution was transferred to a three-necked flask, and then ultrasonic was performed in a nitrogen environment at room temperature for 2 h, and finally a single-layer or few-layer MXene solution was obtained.

[0186] S4), preparation of flexible electrode

[0187] 5 mg / ml of AgNWs was coated on the cleaned PET substrate using the rod coating method until a flexible PET / AgNWs electrode with a square resistance of 10 Ω / sq was obtained;

[0188] The coated PET / AgNWs electrode was immersed in the MXene solution and then dried, and the process was repeated 5 times, then a fine copper wire was led out from the insulating layer with a silver award; due to the increase of deionized water, the Al in the MXene was not completely etched clean, so the pseudo-capacitance of the electrode was reduced, according to the capacitive sensing theory, C EDL = UAC x A, where UAC is the unit capacitance of the electrode, so the unit capacitance UAC of the electrode that is not etched clean is lower, thus leading to a lower sensitivity of the sensor.

[0189] The microstructure of the ionogel prepared in Examples 2-4 is shown in Figure 2 .

[0190] As shown in Figure 3 , the sensitivity of the sensor prepared in Example 2 is 125.67 kPa -1, response time is <5ms, linearity is 0.999; the prepared ionization pressure sensor of Example 2 mainly utilizes the super EDL capacitor formed at the electrode-ion interface to realize pressure sensing.

[0191] As shown in Figure 4 , under the applied test voltage, the electrode band has positive charge A or negative charge D, and under the action of no applied external stress, the cations and anions in the ionic dielectric layer are disordered, so the capacitance is low at this time; when the external stress is applied, the electrode and the ionic gel layer are in full contact at this time, and under the action of electrostatic force, the cations and anions in the ionic gel film will move to the electrode surface, thereby forming a double electric layer (EDL), and a super capacitor is formed on the nanoscale thickness interface. According to the point double-layer EDL theory: C EDL = UAC x A, under the same test voltage, the external pressure load will change the actual contact area of the electrode and the ionic gel film, resulting in a change in the EDL capacitor formed, thereby sensing the size of the pressure. The microporous microstructure design adopted makes the microporous surface appear a secondary microstructure, thereby increasing the variable contact area and improving the sensitivity of the device. At the same time, the micropores can also increase the linear working interval of the sensor.

[0192] From Figure 5 , it can be seen that the sensor prepared in Example 2 has the performance of fast response and recovery ability, so the ionization pressure sensing paper based on the microporous microstructure ionic gel dielectric layer of Example 2 shows extremely high response linearity, extremely high device sensitivity, mechanical stability and fast response.

[0193] The above examples and descriptions in the specification only illustrate the principles and the best mode of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for preparing a wide-stress full-linear flexible capacitive sensor, characterized in that, The method comprises the following steps: S1), substrate material pretreatment The cut substrate material is sequentially treated by ultrasonic in deionized water, ethanol and isopropanol solution, constant temperature drying, and then plasma pretreatment to obtain a hydrophilic support flexible substrate material; S2), preparation of conductive nanomaterial A certain amount of glucose, silver nitrate, ferrous sulfate and PVP are added to the hydrothermal kettle to prepare silver nanowires AgNWs by hydrothermal method, and the AgNWs are treated again with NaCl to remove PVP to obtain good conductive AgNWs; S3), preparation of MXene material A certain amount of concentrated hydrochloric acid, deionized water and LiF are used to etch Ti3AlC2, and after cleaning with deionized water and ultrasonic, single-layer or few-layer MXene material is obtained; S4), preparation of flexible electrode A certain amount of AgNWs is coated on the flexible substrate material cleaned in step S1 by rod coating method until a flexible AgNWs electrode with a square resistance of 10Ω / sq is obtained; The coated flexible AgNWs electrode is soaked in the MXene solution and then dried, and the process is repeated for 3-5 times, and then the fine copper wire of the insulating layer is led out with a silver award; S5), preparation of ion dielectric layer with microstructure and micropore A certain amount of PVA, phosphoric acid and deionized water solution is mixed and quickly heated and stirred to prepare a multi-bubble ion gel solution, which is then uniformly scraped on a PDMS mold with a semicircle, and then dried at constant temperature to obtain an ion gel dielectric layer with microstructure and micropore; S6), the ion gel dielectric layer with microstructure and micropore is attached between the two flexible AgNWs / MXene electrodes to form an ion capacitive sensor, the dead are sealed with ultraviolet UV glue to form a waterproof layer, and the sensor is packaged again with heat shrink film, so as to obtain an ion capacitive sensor with good waterproof performance and high sensitivity and wide linearity.

2. The method of claim 1, wherein the method further comprises: In step S1, the substrate material is ultrasonically cleaned with deionized water, ethanol and isopropanol for 10 minutes, and then cleaned in the plasma cleaning machine for 15 minutes.

3. The method of claim 1, wherein the method further comprises: coating the substrate with a first layer of a first material; coating the first layer with a second layer of a second material; and coating the second layer with a third layer of a third material. In step S2, the molar ratio of glucose, silver nitrate, ferrous sulfate and polyvinylpyrrolidone (K30) is about 2:1.5:0.3:0.01-0.

2.

4. The method of claim 1, wherein the method further comprises: In step S2, the conductive nanomaterial is prepared as follows: S21), 1.5 mmol of silver nitrate and 2 mmol of glucose are dissolved in a beaker at room temperature; S22), 0.3 mmol of ferrous sulfate is added, and magnetic stirring is performed for 30 minutes to obtain a light yellow solution; S23), 4.5 g of polyvinylpyrrolidone (K30) is added to the solution; S24), the uniformly mixed solution is transferred to a 100 mL capacity autoclave, sealed and heated at 180℃ for 6 hours; S25), after cooling, multiple washing with deionized water is performed, and the solution is transparent, then 0-0.02 mol of NaCl is added to remove PVP on the surface of AgNWs; after 2 hours, 3 times of centrifugal washing with deionized water is performed to obtain AgNWs.

5. The method of claim 1, wherein the method further comprises: In step S3), the molar ratio of the concentrated hydrochloric acid, deionized water and LiF is 1.7:1-3:0.

3.

6. The method of claim 1, wherein the method further comprises: In step S3), the MXene material is prepared as follows: S31), 5 ml of deionized water was added to 15 ml of concentrated hydrochloric acid, and then the prepared solution was poured into a polytetrafluoroethylene reaction container, and then 1.6 g of LiF and 1 g of Ti3ALC were sequentially added 2； S32), the container is placed in a magnetic heating stirrer at 35℃ and 550rpm for etching for 35h; S33), after etching, the solution is washed by centrifugation with deionized water until the pH of the solution is greater than or equal to 6, followed by ultrasonic treatment for 2 hours in a nitrogen environment, and finally a single-layer or few-layer MXene solution is obtained.

7. The method of claim 1, wherein the method further comprises: In step S5), the concentration of the phosphoric acid solution is 85%.

8. The method of claim 1, wherein the method further comprises: In step S5), the weight ratio of the PVA, phosphoric acid and deionized water is 2:0.5-3:

18.

9. The method of claim 1, wherein the method further comprises: In step S5), the prepared ionic gel solution is poured into a PDMS mold, and heated at 50℃ for 0.5-2h to solidify the ionic gel film. ​

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