Fabrication method and application of wearable biomimetic earthworm-structured flexible piezoresistive sensor

Abstract

This invention discloses a method for fabricating and applying a wearable, biomimetic, earthworm-structured flexible piezoresistive sensor. The invention uses polyester fabric as a framework, and through the synergistic effect of plasma and stretching modulation, wrinkles are formed on the surface of the polyester fabric, creating abundant microridges, laying the foundation for constructing conductive bridges. Furthermore, under an electric field, carbon nanotubes are uniformly dispersed and arranged at the wrinkles, enabling the construction of new conductive paths under different pressures. The flexible piezoresistive sensor of this invention exhibits extremely high sensitivity, a low detection limit, fast response time, and good stability, demonstrating great application potential in practical applications such as electronic skin and wearable electronic devices. This invention solves the problems of complex fabrication processes and the difficulty in simultaneously achieving high sensitivity and stability in existing biomimetic piezoresistive sensors, injecting momentum into the development of intelligent wearable platforms.

Description

Technical Field

[0001] This invention relates to a fabric micro / nano composite conductive material and its preparation method, belonging to the technical field of fabric micro / nano structural materials and flexible electronic materials. Background Technology

[0002] Traditional rigid sensors suffer from significant shortcomings in flexibility, ductility, and wearability, making it difficult to meet the diverse sensor demands of modern technology. In contrast, flexible sensors, with their superior flexibility and deformability, can adapt to various complex shapes and surfaces and can be effectively integrated with other flexible electronic devices to build more intelligent and convenient systems. In recent years, with the continuous development of wearable electronics technology and the widespread application of smart terminals, flexible pressure sensors have shown broad development prospects and market potential in fields such as electronic skin, human health monitoring, and soft robotics. Flexible sensors are typically composed of a conductive sensing element and an elastic substrate material, capable of converting mechanical signals caused by material deformation into quantifiable electrical signals. In particular, piezoresistive strain sensors, due to their unique sensing principle, simple manufacturing process, excellent durability, convenient fabrication process, and good visualization characteristics, have become a key area of ​​research and application.

[0003] The assembly of piezoresistive strain sensors relies on uniformly dispersing conductive materials within a flexible polymer matrix to construct a permeable network. In research aimed at improving the sensitivity and extending the response range of flexible piezoresistive strain sensors, various flexible substrate materials with micro / nano structures have emerged, including common structures such as fiber structures, array structures, crack structures, and electrospun film structures. Although the strategy of enhancing sensor performance using micro / nano structures has achieved initial success and shown promising application prospects, the fabrication process of these nanostructures is typically complex, undoubtedly posing a challenge to large-scale industrial production. From a practical application perspective, the demands for biocompatibility, high sensitivity, high stability, high durability, low-cost manufacturing, and wearable comfort have become the main scientific challenges that urgently need to be overcome in the field of piezoresistive strain sensors. These intertwined requirements are key factors restricting the expansion and deepening of piezoresistive strain sensors into wider application areas. Summary of the Invention

[0004] The problem to be solved by this invention is that current fabric-based micro / nano structure flexible sensing composite materials suffer from complex processes, high costs, small pressure measurement ranges, and low sensitivity.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] A method for fabricating a wearable, biomimetic earthworm-structured flexible piezoresistive sensor includes the following steps:

[0007] S1: Wash and dry the polyester fabric to obtain a clean polyester fabric; mix and impregnate the clean polyester fabric with PDMS solution to obtain a PDMS-impregnated polyester fabric; dry the PDMS-impregnated polyester fabric to obtain sample A.

[0008] S2: Capacitively coupled plasma discharge is used, and argon is used as the plasma treatment gas. The discharge parameters are adjusted according to the experimental requirements. Sample A is placed in the plasma machine for treatment, and then mechanically stretched and released using a tensile tester to obtain sample B.

[0009] S3: Add multi-walled carbon nanotubes to anhydrous ethanol and then perform probe sonication; centrifuge the resulting dispersion to remove free MWCNTs and obtain a multi-walled carbon nanotube dispersion.

[0010] S4: Immerse the pretreated sample B in a multi-walled carbon nanotube dispersion, then lift it up and place it between two electrode plates to apply an alternating electric field for curing until the anhydrous ethanol is completely evaporated. Take out the fabric and put it in an oven to dry and cure it again to obtain sample C.

[0011] S5: Stack samples C, encapsulate both ends with electrode material, and connect them to the detection instrument through wires to obtain a wearable biomimetic earthworm-structured flexible piezoresistive sensor.

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

[0013] Preferably, in S2, the pressure of 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 tensile force of the tensile tester is 30-100 N.

[0014] Preferably, in step 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 centrifugation speed is 1000-2500 r / min, and the time is 15-30 min.

[0015] Preferably, in step S4, the impregnation time is 30–90 min; the voltage of the alternating electric field is 30–80 V; the curing time is 1–2 h; the temperature of the oven is 50–70 °C; and the drying and curing time is 0.5–2 h.

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

[0017] This invention also provides the application of the wearable biomimetic earthworm structure flexible piezoresistive sensor prepared by the above preparation method in a human motion detection device.

[0018] Preferably, the human movements include at least one of elbow flexion, wrist flexion, finger movement, pulse / heartbeat, and Morse code.

[0019] This invention applies micro / nano structures to the field of sensors, offering advantages such as improved substrate-interface bonding and significantly enhanced sensor sensitivity and stability. Furthermore, its fabrication process is environmentally friendly, efficient, and energy-saving, opening up new opportunities for the widespread 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 fabrication process, the technical solution of this invention uses plasma treatment, physical stretching, and electric field action, which has the advantages of simplicity, high efficiency, and low cost, and is expected to be mass-produced. The biomimetic earthworm structure obtained by the above methods, under the action of external micro-force, point contact and line contact replace surface contact, the conductive path is significantly increased, and it exhibits extremely high sensitivity. It can clearly distinguish physiological signals of the human body such as pulse fluctuations, which makes it show 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 has good flexibility, which not only makes good contact with the electrode, but also easily fits the uneven skin of the human body, thus ensuring that it can better monitor physical signals from the human body or detect external stimuli in practical applications.

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

[0024] (4) The sensor described in this invention solves the problem that the existing biomimetic fabric-based piezoresistive sensors have complex manufacturing processes and are difficult to simultaneously possess high sensitivity and stability. Attached Figure Description

[0025] Figure 1 The process flow diagram of the fabrication method of the wearable biomimetic earthworm structure flexible piezoresistive sensor provided by the present invention;

[0026] Figure 2 The images shown are physical images and SEM images of the wearable biomimetic earthworm structure conductive fabric in Example 2; where (a) is a physical image of the wearable biomimetic earthworm structure conductive fabric, (b) is an SEM image of the polyester fabric, (c) is an SEM image of the biomimetic earthworm structure fabric, and (d) is an SEM image of the biomimetic earthworm structure conductive fabric.

[0027] Figure 3 The following tests were conducted on the flexible piezoresistive sensor prepared in Example 3: (a) electrical response test under different pressures, (b) electrical response test under different frequencies, (c) device response time test, and (d) device stability test.

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

[0029] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a process flow diagram illustrating the fabrication method of the wearable biomimetic earthworm-structured flexible piezoresistive sensor provided by the present invention. Figure 1 As shown, the process includes the following steps:

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

[0032] (2) Preparation of biomimetic earthworm structure fabric;

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

[0034] (4) Preparation of biomimetic earthworm structure conductive fabric;

[0035] (5) Assembly of biomimetic earthworm structure conductive fabric.

[0036] Example 1

[0037] A method for fabricating and applying a wearable, biomimetic, earthworm-structured, highly sensitive, flexible piezoresistive sensor includes the following steps:

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

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

[0040] S2: Preparation of biomimetic earthworm structure fabric.

[0041] The polyester fabric treated in step S1 is placed in a plasma machine and capacitively coupled plasma discharge is performed using argon gas. The argon gas pressure is adjusted to 50 Pa, the discharge power is 30 W, and the discharge time is 60 s to obtain the plasma-treated polyester fabric. The plasma-treated polyester fabric is then placed in a tensile testing instrument for stretching and release, with a tensile force of 50 N, thus obtaining a biomimetic earthworm structure fabric.

[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 sonication was performed at a frequency of 20 kHz. The resulting dispersion was centrifuged to remove free MWCNTs at a speed of 1200 r / min for 15 min to obtain a well dispersed carbon nanotube solution.

[0044] S4: Preparation of biomimetic earthworm structure conductive fabric.

[0045] The biomimetic earthworm structure fabric obtained in S2 was immersed in the uniformly dispersed carbon nanotube solution in S3 for 45 min. Then, the immersed biomimetic earthworm structure fabric was lifted and placed between two electrode plates and a voltage of 60V was applied for curing for 1 h. Then, the cured biomimetic earthworm structure fabric was taken out and placed in a 60℃ oven for drying and curing again for 2 h to obtain the biomimetic earthworm structure conductive fabric.

[0046] S5: Fabrication of a biomimetic earthworm-structured piezoresistive sensor.

[0047] Three layers of the biomimetic earthworm conductive fabric obtained in S4 were stacked together, and the two ends were encapsulated with electrode material. The fabric was then connected to a detection instrument via wires to create a wearable biomimetic earthworm structure piezoresistive sensor. This sensor is applied to human movement, including elbow flexion, wrist flexion, finger movement, pulse and heartbeat, and Morse code.

[0048] Example 2

[0049] A method for fabricating and applying a wearable, biomimetic, earthworm-structured, highly sensitive, flexible piezoresistive sensor includes the following steps:

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

[0051] 7g of polyester fabric was washed in 300ml of deionized water for 1.5h, followed by drying at 60℃ for 1.5h; the clean polyester fabric was then treated in a PDMS solution at a concentration of 30g / L for 45min to obtain PDMS-impregnated polyester fabric; the PDMS-impregnated polyester fabric was then dried at 70℃ for 1.2h.

[0052] S2: Preparation of biomimetic earthworm structure fabric.

[0053] The polyester fabric treated in step S1 is placed in a plasma machine and capacitively coupled plasma discharge is performed using argon gas. The argon gas pressure is adjusted to 30 Pa, the discharge power is 90 W, and the discharge time is 50 s to obtain the plasma-treated polyester fabric. The plasma-treated polyester fabric is then placed in a tensile testing instrument for stretching and release, with a tensile force of 80 N, thus obtaining a biomimetic earthworm structure fabric.

[0054] S3: Preparation of carbon nanotube solution.

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

[0056] S4: Preparation of biomimetic earthworm structure conductive fabric.

[0057] The biomimetic earthworm structure fabric obtained in S2 was immersed in the uniformly dispersed carbon nanotube solution in S3 for 30 min. Then, the immersed biomimetic earthworm structure fabric was lifted and placed between two electrode plates and a voltage of 80V was applied for curing for 1.2 h. Then, the cured biomimetic earthworm structure fabric was taken out and placed in a 70℃ oven for drying and curing again for 1.2 h, thus obtaining the biomimetic earthworm structure conductive fabric.

[0058] S5: Fabrication of a biomimetic earthworm-structured piezoresistive sensor.

[0059] The biomimetic earthworm conductive fabric obtained in S4 is stacked in 6 layers, and the two ends are encapsulated with electrode material. It is then connected to the detection instrument through wires to create a wearable biomimetic earthworm structure piezoresistive sensor, which can be applied to human movement, including elbow flexion, wrist flexion, finger movement, pulse and heartbeat, and Morse code.

[0060] Example 3

[0061] A method for fabricating and applying a wearable, biomimetic, earthworm-structured, highly sensitive, flexible piezoresistive sensor includes the following steps:

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

[0063] 6g of polyester fabric was washed in 500ml of deionized water for 1 hour, followed by drying at 65℃ for 0.8 hours; the clean polyester fabric was then treated in a PDMS solution at a concentration of 25g / L for 60 minutes to obtain PDMS-impregnated polyester fabric; the PDMS-impregnated polyester fabric was then dried at 68℃ for 0.8 hours.

[0064] S2: Preparation of biomimetic earthworm structure fabric.

[0065] The polyester fabric treated in step S1 is placed in a plasma machine and capacitively coupled plasma discharge is performed using argon gas. 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 plasma-treated polyester fabric. The plasma-treated polyester fabric is then placed in a tensile testing instrument for stretching and release, with a tensile force of 35 N, thus obtaining a biomimetic earthworm structure fabric.

[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 sonication was performed at a frequency of 18 kHz. The resulting dispersion was centrifuged to remove free MWCNTs at a speed of 2000 r / min for 25 min to obtain a well dispersed carbon nanotube solution.

[0068] S4: Preparation of biomimetic earthworm structure conductive fabric.

[0069] The biomimetic earthworm structure fabric obtained in S2 was immersed in the uniformly dispersed carbon nanotube solution in S3 for 90 min. Then, the immersed biomimetic earthworm structure fabric was lifted and placed between two electrode plates and a voltage of 70V was applied for curing for 1.5 h. Then, the cured biomimetic earthworm structure fabric was taken out and placed in a 68℃ oven for drying and curing again for 1.5 h, thus obtaining the biomimetic earthworm structure conductive fabric.

[0070] S5: Fabrication of a biomimetic earthworm-structured piezoresistive sensor.

[0071] The biomimetic earthworm conductive fabric obtained in S4 is stacked in 7 layers, and the two ends are encapsulated with electrode material. It is then connected to the detection instrument through wires to create a wearable biomimetic earthworm structure piezoresistive sensor, which can be applied to human movement, including elbow flexion, wrist flexion, finger movement, pulse and heartbeat, and Morse code.

[0072] Example 4

[0073] A method for fabricating and applying a wearable, biomimetic, earthworm-structured, highly sensitive, flexible piezoresistive sensor includes the following steps:

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

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

[0076] S2: Preparation of biomimetic earthworm structure fabric.

[0077] The polyester fabric treated in step S1 is placed in a plasma machine and capacitively coupled plasma discharge is performed using argon gas. 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 plasma-treated polyester fabric. The plasma-treated polyester fabric is then placed in a tensile testing instrument for stretching and release, with a tensile force of 55 N, thus obtaining a biomimetic earthworm structure fabric.

[0078] S3: Preparation of carbon nanotube solution.

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

[0080] S4: Preparation of biomimetic earthworm structure conductive fabric.

[0081] The biomimetic earthworm structure fabric obtained in S2 was immersed in the uniformly dispersed carbon nanotube solution in S3 for 65 min. Then, the immersed biomimetic earthworm structure fabric was lifted and placed between two electrode plates and a voltage of 75V was applied for curing for 1.2 h. Then, the cured biomimetic earthworm structure fabric was taken out and placed in a 60℃ oven for drying and curing again for 1.2 h, thus obtaining the biomimetic earthworm structure conductive fabric.

[0082] S5: Fabrication of a biomimetic earthworm-structured piezoresistive sensor.

[0083] Five layers of the biomimetic earthworm conductive fabric obtained in S4 were stacked together, and the two ends were encapsulated with electrode material. The fabric was then connected to a detection instrument via wires to create a wearable biomimetic earthworm structure piezoresistive sensor. This sensor is applied to human movement, including elbow flexion, wrist flexion, finger movement, pulse and heartbeat, and Morse code.

Claims

1. A method for fabricating a wearable, biomimetic earthworm-structured flexible piezoresistive sensor, characterized in that, Includes the following steps: S1: Wash and dry the polyester fabric to obtain a clean polyester fabric; mix and impregnate the clean polyester fabric with PDMS solution to obtain a PDMS-impregnated polyester fabric; dry the PDMS-impregnated polyester fabric to obtain sample A. S2: Capacitively coupled plasma discharge is used, and argon is used as the plasma treatment gas. The discharge parameters are adjusted according to the experimental requirements. Sample A is placed in the plasma machine for treatment, and then mechanically stretched and released using a tensile tester to obtain sample B. S3: Add multi-walled carbon nanotubes to anhydrous ethanol and then perform probe sonication. The resulting dispersion was centrifuged to remove free MWCNTs, yielding a multi-walled carbon nanotube dispersion. S4: Immerse the pretreated sample B in a multi-walled carbon nanotube dispersion, then lift it up and place it between two electrode plates to apply an alternating electric field for curing until the anhydrous ethanol is completely evaporated. Take out the fabric and put it in an oven to dry and cure it again to obtain sample C. S5: Stack samples C, encapsulate both ends with electrode material, and connect them to the detection instrument through wires to obtain a wearable biomimetic earthworm-structured flexible piezoresistive sensor.

2. The method for fabricating the wearable biomimetic earthworm-structured flexible piezoresistive sensor as described in claim 1, characterized in that, In step S1, the washing is performed using deionized water for 0.5–2 hours; the drying temperature is 50–70°C for 0.5–2 hours; the solvent for the PDMS solution is anhydrous ethanol with a concentration of 10–40 g / L; the immersion time is 30–60 minutes; and the drying is carried out in an oven at 55–85°C for 0.5–3 hours.

3. The method for fabricating the wearable biomimetic earthworm-structured flexible piezoresistive sensor as described in claim 1, characterized in that, In S2, the pressure of 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 tensile force of the tensile tester is 30-100 N.

4. The method for fabricating the wearable biomimetic earthworm-structured flexible piezoresistive sensor as described in 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 centrifugation speed is 1000-2500 r / min, and the time is 15-30 min.

5. The method for fabricating a wearable biomimetic earthworm-structured flexible piezoresistive sensor as described in claim 1, characterized in that, In S4, the impregnation time is 30-90 min; the voltage of the AC electric field is 30-80 V; the curing time is 1-2 h; the temperature of the oven is 50-70 °C; and the drying and curing time is 0.5-2 h.

6. The method for fabricating a wearable biomimetic earthworm-structured flexible piezoresistive sensor as described in claim 1, characterized in that, In S5, the number of stacked layers is 1 to 7.

7. The application of the wearable biomimetic earthworm-structured flexible piezoresistive sensor prepared by the preparation method according to any one of claims 1-6 in a human motion detection device.

8. The application as described in claim 7, characterized in that, The human movements mentioned include at least one of elbow flexion, wrist flexion, finger movement, pulse and heartbeat, and Morse code.

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