Preparation method and application of wearable flexible piezoresistive sensor with bionic earthworm structure

Abstract

The invention discloses a preparation method and application of a wearable flexible piezoresistive sensor with a bionic earthworm structure. The polyester fabric is adopted as a framework, wrinkles are formed on the surface of the polyester fabric through the synergistic effect of plasma and extension regulation, rich micro ridges are generated, and a foundation is laid for constructing a conductive bridge. And the carbon nanotubes are uniformly dispersed and arranged at the wrinkles in an electric field, so that a new conductive path can be constructed under different pressures. The flexible piezoresistive sensor has the advantages of extremely high sensitivity, low detection limit, short response time and good stability, and has great application potential in practical application of electronic skin, wearable electronic devices and the like. The sensor solves the problems that an existing bionic piezoresistive sensor is complex in preparation process and difficult to have high sensitivity and stability at the same time, and injects power for development of an intelligent wearable platform.

Description

Technical Field

[0001] The invention relates to a fabric micro-nano composite conductive material and a preparation method thereof, belonging to the technical field of fabric micro-nano structural materials and flexible electronic materials. Background Art

[0002] Traditional rigid sensors have significant deficiencies in flexibility, ductility and wearability, and are difficult to meet the diverse needs of modern technology for sensors. In contrast, flexible sensors, with their excellent flexibility and deformability, can adapt to various complex shapes and surfaces, and can be effectively integrated with other flexible electronic devices to build a more intelligent and convenient system. In recent years, with the continuous development of wearable electronic technology and the widespread application of smart terminals, flexible pressure sensors have shown broad development prospects and market potential in the fields of electronic skin, human health monitoring, soft robots, etc. Flexible sensors are usually composed of conductive sensing elements and elastic substrate materials, which can convert mechanical signals caused by material deformation into quantifiable electrical signals. In particular, piezoresistive strain sensors have become the focus of research and application due to their unique sensing principle, simple manufacturing process, excellent durability, convenient preparation process and good visualization characteristics.

[0003] The assembly of piezoresistive strain sensors relies on uniformly dispersing conductive materials in a flexible polymer matrix to construct a permeation network. In the study of improving the sensitivity of flexible piezoresistive strain sensors and expanding their response range, various flexible substrate materials with micro-nano structures have emerged. Common structures include fiber structures, array structures, crack structures, and electrospinning membrane structures. Although the strategy of improving sensor performance with the help of micro-nano structures has achieved initial results and shown good application prospects, the preparation process of these nano-microstructures is usually complicated, which undoubtedly brings challenges to large-scale industrial production. From the perspective of practical applications, the requirements of biocompatibility, high sensitivity, high stability, high durability, low-cost manufacturing, and wearing comfort have become the main scientific problems that need to be broken through in the current field of piezoresistive strain sensors. The various requirements are intertwined and have become the key factors restricting the expansion and deepening of piezoresistive strain sensors into a wider range of application fields. Summary of the invention

[0004] The problem to be solved by the present invention is that the current fabric-based micro-nanostructure flexible sensing composite material has the technical problems of complex process, high cost, small pressure measurement range and high sensitivity.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions:

[0006] A method for preparing a wearable bionic earthworm structure flexible piezoresistive sensor comprises the following steps:

[0007] S1: washing the polyester fabric and then drying it to obtain a clean polyester fabric; impregnating the clean polyester fabric with a PDMS solution to obtain a polyester fabric impregnated with PDMS; drying the polyester fabric impregnated with PDMS to obtain sample A;

[0008] S2: Using capacitively coupled plasma discharge, using argon as the plasma treatment gas, adjusting the discharge parameters according to the experimental requirements, placing sample A in a plasma machine for treatment, and then using a tensile tester for mechanical stretching and release to obtain sample B;

[0009] S3: adding multi-walled carbon nanotubes to anhydrous ethanol, and then performing probe ultrasonic treatment; the resulting dispersion is centrifuged to remove free MWCNTs, thereby obtaining a multi-walled carbon nanotube dispersion;

[0010] S4: immersing the pretreated sample B in a multi-walled carbon nanotube dispersion, then lifting it and placing it between two electrode plates to apply an alternating electric field for curing until the anhydrous ethanol is completely evaporated, taking out the fabric and placing it in an oven for drying and curing again to obtain sample C;

[0011] S5: Sample C is stacked, both ends are encapsulated with electrode materials, and connected to the detection instrument through wires to obtain a wearable bionic earthworm structured flexible piezoresistive sensor.

[0012] Preferably, in S1, the washing is performed with deionized water for 0.5 to 2 hours; the drying temperature is 50 to 70°C for 0.5 to 2 hours; the solvent of the PDMS solution is anhydrous ethanol with a concentration of 10 to 40 g / L; the immersion time is 30 to 60 minutes; and the drying is performed in an oven at a temperature of 55 to 85°C for 0.5 to 3 hours.

[0013] Preferably, in S2, the pressure of the argon gas in the plasma machine is 10-80 Pa, the discharge power is 30-100 W, and the discharge time is 30-90 s; the tension of the tensile tester is 30-100 N.

[0014] Preferably, in S3, the mass concentration of the multi-walled carbon nanotube dispersion is 1-5%; the frequency of the probe ultrasonic treatment is 10-30 kHz, and the time is 0.5-2 h; the speed of the centrifugation is 1000-2500 r / min, and the time is 15-30 min.

[0015] Preferably, in S4, the immersion time is 30 to 90 minutes; the voltage of the AC electric field is 30 to 80 V; the curing time is 1 to 2 hours; the temperature of the oven is 50 to 70° C.; and the drying and curing time is 0.5 to 2 hours.

[0016] Preferably, in S5, the number of stacked layers is 1 to 7 layers.

[0017] The present invention also provides the use of a wearable bionic earthworm structure flexible piezoresistive sensor prepared by the above preparation method in a human motion detection device.

[0018] Preferably, the human body movement includes at least one of elbow bending, wrist bending, finger movement, pulse heartbeat, and Morse code.

[0019] The present invention applies micro-nano structures to the field of sensors, which has the advantages of improving the combination of the substrate and the interface, and greatly improving the sensitivity and stability of the sensor. Moreover, its preparation process is environmentally friendly, efficient, and energy-saving, opening up new opportunities for the wide application of sensors.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) Compared with the traditional pressure sensor preparation process, the method of plasma treatment, physical extension and electric field action in the technical solution of the present invention has the advantages of simplicity, high efficiency, low cost, etc., and is expected to be mass-produced. The bionic earthworm structure obtained by the above method, under the action of external micro-force, point contact and line contact replace surface contact, and the conductive path is significantly increased, showing extremely high sensitivity, and can clearly distinguish physiological signals of the human body such as pulse fluctuations, so that it has great potential in practical applications such as electronic skin and wearable electronic devices.

[0022] (2) In the technical solution of the present invention, the fabric bionic layer used has good flexibility. It can not only have good contact with the electrode, but also easily fit the uneven skin of the human body, thus ensuring that it can better monitor physical signals from the human body or detect stimuli from the outside world in practical applications.

[0023] (3) The sensitive layer obtained by impregnating the fabric base with carbon nanotube solution in the present invention exhibits extremely high sensitivity and low detection limit, low operating voltage, fast response time and good cycle stability. Under the action of a small external force, the bionic earthworm structure deforms, the conductive path increases, and the resistance decreases.

[0024] (4) The sensor of the present invention solves the problem that the existing bionic structure fabric-based piezoresistive sensors have complex preparation processes and are difficult to have both high sensitivity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A process flow chart of a method for preparing a wearable bionic earthworm structure flexible piezoresistive sensor provided by the present invention;

[0026] Figure 2 The figures are the physical pictures and SEM pictures of the wearable bionic earthworm structure conductive fabric in Example 2; wherein, (a) is the physical picture of the wearable bionic earthworm structure conductive fabric, (b) is the SEM picture of the polyester fabric, (c) is the SEM picture of the bionic earthworm structure fabric, and (d) is the SEM picture of the bionic earthworm structure conductive fabric;

[0027] Figure 3 The flexible piezoresistive sensor prepared in Example 3 (a) tests on electrical response to different pressures, (b) tests on electrical response to different frequencies, (c) tests on device response time, and (d) tests on device stability;

[0028] Figure 4 This is a practical application test of the flexible piezoresistive sensor prepared in Example 3 for monitoring human body signals; wherein, (a) is an elbow bending test, (b) is a finger bending test, (c) is a wrist pulse test, and (d) is a Morse code test. DETAILED DESCRIPTION

[0029] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0030] Figure 1 The process flow chart of the preparation method of the wearable bionic earthworm structure flexible piezoresistive sensor provided by the present invention. Figure 1 As shown, the process includes the following steps:

[0031] (1) Pretreatment of polyester fabric and immersion in PDMS;

[0032] (2) Preparation of bionic earthworm structure fabrics;

[0033] (3) Preparation of carbon nanotube solution;

[0034] (4) Preparation of bionic earthworm structure conductive fabrics;

[0035] (5) Assembly of bionic earthworm structure conductive fabrics.

[0036] Example 1

[0037] A preparation method and application of a wearable bionic earthworm structured highly sensitive flexible piezoresistive sensor, comprising the following steps:

[0038] S1: Pretreatment of polyester fabric and immersion in PDMS.

[0039] 5 g of polyester fabric was washed in 200 ml of deionized water for 1 hour, and then dried at 50° C. for 1 hour; the clean polyester fabric was treated in a PDMS solution for 35 minutes, wherein the concentration of PDMS was 10 g / L, to obtain a polyester fabric impregnated with PDMS; the polyester fabric impregnated with PDMS was dried at 60° C. for 1 hour;

[0040] S2: Preparation of bionic earthworm structured fabrics.

[0041] The polyester fabric treated in step S1 is placed in a plasma machine, and capacitively coupled plasma discharge is used, using argon gas, wherein the gas pressure of the argon gas is adjusted to 50 Pa, the discharge power is 30 W, and the discharge time is 60 s, to obtain the polyester fabric treated with plasma; the polyester fabric treated with plasma is placed in a tensile tester for stretching and release, and the tensile force is 50 N, so that the fabric with a bionic earthworm structure is obtained;

[0042] S3: Preparation of carbon nanotube solution.

[0043] 1.5 g of multi-walled carbon nanotubes were added to 300 mL of anhydrous ethanol, and then probe ultrasonic treatment was performed at a frequency of 20 kHz. The resulting dispersion was centrifuged to remove free MWCNTs at a centrifuge speed of 1200 r / min for 15 min to obtain a well-dispersed carbon nanotube solution;

[0044] S4: Preparation of bionic earthworm structured conductive fabrics.

[0045] The bionic earthworm structure fabric obtained in S2 is immersed in the uniformly dispersed carbon nanotube solution in S3 for 45 minutes; then the immersed bionic earthworm structure fabric is lifted and placed between two electrode plates, and a voltage of 60V is applied for curing for 1 hour; then the cured bionic earthworm structure fabric is taken out and placed in a 60°C oven for drying and curing for 2 hours, so as to obtain a bionic earthworm structure conductive fabric;

[0046] S5: Preparation of bionic earthworm structure piezoresistive sensor.

[0047] Three layers of the bionic earthworm conductive fabric obtained in S4 are selected and stacked, the two ends are encapsulated with electrode materials, and connected to the detection instrument through wires to obtain a wearable bionic earthworm structure piezoresistive sensor, which is applied to human body movements, including elbow bending, wrist bending, finger movement, pulse heartbeat, and Morse code.

[0048] Example 2

[0049] A preparation method and application of a wearable bionic earthworm structured highly sensitive flexible piezoresistive sensor, comprising the following steps:

[0050] S1: Pretreatment of polyester fabric and immersion in PDMS.

[0051] 7g of polyester fabric was washed in 300ml of deionized water for 1.5h, and then dried at 60°C for 1.5h; the clean polyester fabric was treated in a PDMS solution for 45min, wherein the concentration of PDMS was 30g / L, to obtain a polyester fabric impregnated with PDMS; the polyester fabric impregnated with PDMS was dried at 70°C for 1.2h;

[0052] S2: Preparation of bionic earthworm structured fabrics.

[0053] The polyester fabric treated in step S1 is placed in a plasma machine, and capacitively coupled plasma discharge is used, using argon gas, wherein the gas pressure of the argon gas is adjusted to 30 Pa, the discharge power is 90 W, and the discharge time is 50 s, to obtain the polyester fabric treated with plasma; the polyester fabric treated with plasma is placed in a tensile tester for stretching and release, and the tensile force is 80 N, so that the fabric with a bionic earthworm structure is obtained;

[0054] S3: Preparation of carbon nanotube solution.

[0055] 3 g of multi-walled carbon nanotubes were added to 500 mL of anhydrous ethanol, and then probe ultrasonic treatment was performed at a frequency of 25 kHz. The resulting dispersion was centrifuged to remove free MWCNTs at a centrifuge speed of 1500 r / min for 20 min to obtain a well-dispersed carbon nanotube solution;

[0056] S4: Preparation of bionic earthworm structured conductive fabrics.

[0057] The bionic earthworm structure fabric obtained in S2 is immersed in the uniformly dispersed carbon nanotube solution in S3 for 30 minutes; then the immersed bionic earthworm structure fabric is lifted and placed between two electrode plates, and a voltage of 80V is applied for curing for 1.2 hours; then the cured bionic earthworm structure fabric is taken out and placed in a 70°C oven for drying and curing again for 1.2 hours, so as to obtain a bionic earthworm structure conductive fabric;

[0058] S5: Preparation of bionic earthworm structure piezoresistive sensor.

[0059] Six layers of the bionic earthworm conductive fabric obtained in S4 are selected and stacked, the two ends are encapsulated with electrode materials, and connected to the detection instrument through wires to obtain a wearable bionic earthworm structure piezoresistive sensor, which is applied to human body movements, including elbow bending, wrist bending, finger movement, pulse heartbeat, and Morse code.

[0060] Example 3

[0061] A preparation method and application of a wearable bionic earthworm structured highly sensitive flexible piezoresistive sensor, comprising the following steps:

[0062] S1: Pretreatment of polyester fabric and immersion in PDMS.

[0063] 6 g of polyester fabric was washed in 500 ml of deionized water for 1 hour, and then dried at a temperature of 65° C. for 0.8 hours; the clean polyester fabric was treated in a PDMS solution for 60 minutes, wherein the concentration of PDMS was 25 g / L, to obtain a polyester fabric impregnated with PDMS; the polyester fabric impregnated with PDMS was dried at a temperature of 68° C. for 0.8 hours;

[0064] S2: Preparation of bionic earthworm structured fabrics.

[0065] The polyester fabric treated in step S1 is placed in a plasma machine, and capacitively coupled plasma discharge is used, using argon gas, wherein the gas pressure of the argon gas is adjusted to 65 Pa, the discharge power is 85 W, and the discharge time is 90 s, to obtain the polyester fabric treated with plasma; the polyester fabric treated with plasma is placed in a tensile tester for stretching and release, and the tensile force is 35 N, so that the fabric with a bionic earthworm structure is obtained;

[0066] S3: Preparation of carbon nanotube solution.

[0067] 2.8 g of multi-walled carbon nanotubes were added to 500 mL of anhydrous ethanol, and then probe ultrasonic treatment was performed at a frequency of 18 kHz. The resulting dispersion was centrifuged to remove free MWCNTs at a centrifuge speed of 2000 r / min for 25 min to obtain a well-dispersed carbon nanotube solution;

[0068] S4: Preparation of bionic earthworm structured conductive fabrics.

[0069] The bionic earthworm structure fabric obtained in S2 is immersed in the uniformly dispersed carbon nanotube solution in S3 for 90 minutes; then the immersed bionic earthworm structure fabric is lifted and placed between two electrode plates, and a voltage of 70V is applied for curing for 1.5 hours; then the cured bionic earthworm structure fabric is taken out and placed in a 68°C oven for drying and curing again for 1.5 hours, so as to obtain a conductive fabric with a bionic earthworm structure;

[0070] S5: Preparation of bionic earthworm structure piezoresistive sensor.

[0071] Seven layers of the bionic earthworm conductive fabric obtained in S4 are selected and stacked, and the two ends are encapsulated with electrode materials and connected to the detection instrument through wires to obtain a wearable bionic earthworm structure piezoresistive sensor, which is applied to human body movements, including elbow bending, wrist bending, finger movement, pulse heartbeat, and Morse code.

[0072] Example 4

[0073] A preparation method and application of a wearable bionic earthworm structured highly sensitive flexible piezoresistive sensor, comprising the following steps:

[0074] S1: Pretreatment of polyester fabric and immersion in PDMS.

[0075] 5.5 g of polyester fabric was washed in 300 ml of deionized water for 1.2 h, and then dried at 70° C. for 0.5 h; the clean polyester fabric was treated in a PDMS solution for 50 min, wherein the concentration of PDMS was 35 g / L, to obtain a polyester fabric impregnated with PDMS; the polyester fabric impregnated with PDMS was dried at 70° C. for 1.8 h;

[0076] S2: Preparation of bionic earthworm structured fabrics.

[0077] The polyester fabric treated in step S1 is placed in a plasma machine, and capacitively coupled plasma discharge is used, using argon gas, wherein the gas pressure of the argon gas is adjusted to 78 Pa, the discharge power is 95 W, and the discharge time is 65 s, to obtain the polyester fabric treated with plasma; the polyester fabric treated with plasma is placed in a tensile tester for stretching and release, and the tensile force is 55 N, so that the fabric with a bionic earthworm structure is obtained;

[0078] S3: Preparation of carbon nanotube solution.

[0079] 3 g of multi-walled carbon nanotubes were added to 300 mL of anhydrous ethanol, and then probe ultrasonic treatment was performed at a frequency of 28 kHz. The resulting dispersion was centrifuged to remove free MWCNTs at a centrifuge speed of 1800 r / min for 15 min to obtain a well-dispersed carbon nanotube solution;

[0080] S4: Preparation of bionic earthworm structured conductive fabrics.

[0081] The bionic earthworm structure fabric obtained in S2 is immersed in the uniformly dispersed carbon nanotube solution in S3 for 65 minutes; then the immersed bionic earthworm structure fabric is lifted and placed between two electrode plates, and a voltage of 75V is applied for curing for 1.2 hours; then the cured bionic earthworm structure fabric is taken out and placed in a 60°C oven for drying and curing again for 1.2 hours, so as to obtain a bionic earthworm structure conductive fabric;

[0082] S5: Preparation of bionic earthworm structure piezoresistive sensor.

[0083] Five layers of the bionic earthworm conductive fabric obtained in S4 are selected and stacked, the two ends are encapsulated with electrode materials, and connected to the detection instrument through wires to obtain a wearable bionic earthworm structure piezoresistive sensor, which is applied to human body movements, including elbow bending, wrist bending, finger movement, pulse heartbeat, and Morse code.

Claims

1. A method for preparing a wearable bionic earthworm-structured flexible piezoresistive sensor, characterized in that: The following steps are involved: S1: washing the polyester fabric and then drying it to obtain a clean polyester fabric; impregnating the clean polyester fabric with a PDMS solution to obtain a polyester fabric impregnated with PDMS; drying the polyester fabric impregnated with PDMS to obtain sample A; S2: Using capacitively coupled plasma discharge, using argon as the plasma treatment gas, adjusting the discharge parameters according to the experimental requirements, placing sample A in a plasma machine for treatment, and then using a tensile tester for mechanical stretching and release to obtain sample B; S3: adding MWCNTs to anhydrous ethanol followed by probe sonication; The obtained dispersion is centrifuged to remove free MWCNTs to obtain a multi-walled carbon nanotube dispersion; S4: immersing the pretreated sample B in a multi-walled carbon nanotube dispersion, then lifting it and placing it between two electrode plates to apply an alternating electric field for curing until the anhydrous ethanol is completely evaporated, taking out the fabric and placing it in an oven for drying and curing again to obtain sample C; S5: Sample C is stacked, both ends are encapsulated with electrode materials, and connected to the detection instrument through wires to obtain a wearable bionic earthworm structured flexible piezoresistive sensor.

2. The method for preparing the wearable bionic earthworm structure flexible piezoresistive sensor according to claim 1, characterized in that: In S1, the washing is performed with deionized water for 0.5 to 2 hours; the drying temperature is 50 to 70°C for 0.5 to 2 hours; the solvent of the PDMS solution is anhydrous ethanol with a concentration of 10 to 40 g / L; the immersion time is 30 to 60 minutes; and the drying is performed in an oven at a temperature of 55 to 85°C for 0.5 to 3 hours.

3. The method for preparing the wearable bionic earthworm structure flexible piezoresistive sensor according to claim 1, characterized in that: In S2, the pressure of the argon gas in the plasma machine is 10-80 Pa, the discharge power is 30-100 W, and the discharge time is 30-90 s; the tension of the tensile tester is 30-100 N.

4. The method for preparing the wearable bionic earthworm structure flexible piezoresistive sensor according to claim 1, characterized in that: In S3, the mass concentration of the multi-walled carbon nanotube dispersion is 1-5%; the frequency of the probe ultrasonic treatment is 10-30 kHz, and the time is 0.5-2 h; the speed of the centrifugation is 1000-2500 r / min, and the time is 15-30 min.

5. The method for preparing the wearable bionic earthworm structure flexible piezoresistive sensor according to claim 1, characterized in that: In S4, the immersion time is 30 to 90 minutes; the voltage of the AC electric field is 30 to 80 V; the curing time is 1 to 2 hours; the temperature of the oven is 50 to 70° C.; and the drying and curing time is 0.5 to 2 hours.

6. The method for preparing the wearable bionic earthworm structure flexible piezoresistive sensor according to claim 1, characterized in that: In S5, the number of stacked layers is 1 to 7 layers.

7. Application of a wearable bionic earthworm structure flexible piezoresistive sensor prepared by the preparation method according to any one of claims 1 to 6 in a human motion detection device.

8. The use according to claim 7, characterized in that The human body movement includes at least one of elbow bending, wrist bending, finger movement, pulse heartbeat, and Morse code.

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