Preparation method of double conductive network super-hydrophobic fabric strain sensor

Abstract

The invention discloses a preparation method of a double conductive network super-hydrophobic fabric strain sensor, comprising the following steps: subjecting an original non-woven fabric to dopamine self-polymerization treatment to obtain a polydopamine fabric; then immersing the non-woven fabric in a carbon nanotube dispersion to obtain a carbon nanotube conductive fiber network, taking it out and drying it, then immersing it in a silver trifluoroacetate solution, and then reducing it in an ascorbic acid solution to obtain a nano-silver conductive fiber network, and placing the obtained fabric in a polydimethylsiloxane solution for hydrophobic treatment to obtain the strain sensor. The carbon nanotube and nano-silver conductive network constructed by the method improves the sensitivity, sensing range and durable stability of the sensor. In addition, the fabric strain sensor prepared by the method has good hydrophobicity and maintains excellent conductivity in acid, alkali and salt environments, which provides a solution for the fabric strain sensor to work in a complex environment.

Description

Technical Field

[0001] The invention relates to a method for preparing a fabric strain sensor, in particular to a method for preparing a double conductive network super-hydrophobic fabric strain sensor. Background Art

[0002] In recent years, with the rapid development of sensors, wearable strain sensors have received extensive attention in many fields, such as motion monitoring, medical monitoring, human-machine interface, artificial intelligence, etc., and have broad application prospects. Strain sensors can respond to external mechanical stimuli with morphological changes and convert mechanical stimuli into resistance or current signal output. They have the advantages of simple sensing mechanism, easy manufacturing, and low energy consumption, and have broad application prospects in wearable devices. In order to improve the performance of strain sensors, predecessors have conducted a lot of research on the sensitivity and sensing range of sensors through material exploration or structural engineering. Although the optimization of sensing performance has been clearly understood, it is still a challenge to manufacture strain sensors with a wide sensing range (>50%), high sensitivity (>100), good flexibility and good durability (>2000 cycles). In addition, in long-term use, the harsh use environment will cause the decomposition or oxidation of conductive materials, thereby reducing the conductivity and causing irreversible damage to the sensor. Therefore, it is of great significance to develop strain sensors with waterproof performance and high sensing performance to cope with the detection of acid, alkali, salt and underwater environments.

[0003] Patent 202010078702.7 prepared a super-hydrophobic strain sensor composite membrane. The strain sensor has excellent sensitivity and sensing range, and can maintain super-hydrophobic properties under acid / alkali / salt solution erosion. However, the strain sensor prepared by this method has problems such as poor air permeability and poor fit to human skin. Patent 201910226819.2 prepared a super-hydrophobic paper-based flexible strain sensor. The strain sensor has good super-hydrophobic properties, but its strain sensing range is small, which is difficult to meet the needs of large-scale human motion monitoring. Patent 202110968514.6 prepared a super-hydrophobic reduced graphene oxide / polyurethane sponge sensor. The sensor prepared by this method has a wide strain sensing range, but the sensor has low sensitivity and thick size, which is not suitable for monitoring human motion. Patent 202010443697.5 prepared a breathable and waterproof multi-response fabric sensor. This strain sensor has good hydrophobicity, breathability and easy adhesion to the skin, but the sensor sensitivity and sensing range are relatively low, making it difficult to achieve high-precision and large-range human motion monitoring. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a double conductive network superhydrophobic fabric strain sensor with high sensitivity, wide sensing range and durable stability.

[0005] Technical solution: The preparation method of the double conductive network super-hydrophobic fabric strain sensor of the present invention comprises the following steps:

[0006] (1) subjecting the original nonwoven fabric to dopamine self-polymerization treatment to obtain a polydopamine fabric;

[0007] (2) immersing the polydopamine fabric in a carbon nanotube dispersion to obtain a carbon nanotube conductive fiber network, and then taking it out and drying it to obtain a polydopamine / carbon nanotube fabric;

[0008] (3) immersing the polydopamine / carbon nanotube fabric in a silver trifluoroacetate solution, taking it out and drying it, and then reducing it in an ascorbic acid solution to obtain a nanosilver conductive fiber network, and the obtained fabric is a polydopamine / carbon nanotube / nanosilver fabric;

[0009] (4) The polydopamine / carbon nanotube / nanosilver fabric is placed in a polydimethylsiloxane solution for hydrophobic treatment to obtain the strain sensor.

[0010] Wherein, in step (1), the concentration of dopamine is 0.5-0.8wt%, the pH is 8-8.5, the reaction temperature is 25-40°C, and the reaction time is 12-24h. The polydopamine prepared under the reaction conditions can be evenly coated on the fiber surface. Through the chemical polymerization of dopamine, the nonwoven fabric is transformed from a hydrophobic state to a hydrophilic state, which is conducive to the deposition of conductive carbon nanotubes on the fiber surface and reduces the initial resistance of the fabric strain sensor.

[0011] Wherein, in step (2), the carbon nanotube is at least one of a multi-walled carbon nanotube, a single-walled carbon nanotube or a carboxylated carbon nanotube.

[0012] Wherein, in step (2), the concentration of the carbon nanotube dispersion is 5-10 wt %. At this concentration, a complete multi-walled carbon nanotube conductive network will be formed on the surface of the fiber.

[0013] Wherein, in step (2), the polydopamine fabric is placed in the carbon nanotube dispersion and immersed for 40 to 70 minutes; wherein, the immersion is first carried out under ultrasonic conditions for 10 to 20 minutes, and then continued to be immersed for 30 to 50 minutes. This is more conducive to the adsorption of carbon nanotubes on the surface of the fiber.

[0014] Wherein, in step (3), the concentration of the silver trifluoroacetate solution is 5-20wt%, which provides sufficient silver ions for the solution.

[0015] Wherein, in step (3), the polydopamine / carbon nanotube fabric is immersed in the silver trifluoroacetate solution for 30 to 60 minutes, so that enough silver ions are adsorbed on the surface of the fiber.

[0016] Wherein, in step (3), the concentration of the ascorbic acid solution is 3-10wt%, and the reduction time is 30-60min, so that the silver ions on the fiber surface are completely reduced to silver particles.

[0017] Wherein, in step (4), the concentration of polydimethylsiloxane in the ethyl acetate solution is 0.5-2wt%, and the dipping time is 30-60min, which can make the conductive fabric have superhydrophobicity without affecting the surface morphology of the fiber, and the resistance and air permeability of the conductive fabric; the solvent of the polydimethylsiloxane solution is ethyl acetate and / or n-hexane.

[0018] Principle of the invention: In the present invention, the nonwoven fabric is modified by polydopamine, and the nonwoven fabric is changed from a hydrophobic state to a hydrophilic state, which is conducive to the attachment of conductive materials carbon nanotubes and nanosilver to the nonwoven fabric. The double conductive network of carbon nanotubes and nanosilver particles constructed by carbon nanotubes and nanosilver particles enables the sensor to have high sensitivity and a wide sensing range, while giving the fiber a rough microstructure. The low surface energy PDMS combined with the rough fiber microstructure surface makes the nonwoven fabric sensor super hydrophobic, and also improves the corrosion resistance and sensing stability of the sensor, which enables the strain sensor to be used in complex and more severe external environments, and can maintain stable conductivity. The prepared strain sensor can not only realize the monitoring of daily human body movements, but also has excellent responsiveness to underwater movements.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: (1) The fabric strain sensor prepared by the method has high sensitivity, wide sensing range and durable stability; (2) The carbon nanotube and nanosilver double conductive network reduces the resistance of the fabric strain sensor and improves the conductivity, so that the fabric strain sensor has fast response, low detection limit and high sensitivity to tensile deformation. At the same time, the carbon nanotube and nanosilver double conductive network has a rough microstructure surface morphology, combined with the low surface energy material PDMS, the fabric strain sensor has good hydrophobic properties. (3) After the hydrophobic treatment of the fabric strain sensor, the sensor has excellent resistance stability. Experiments have found that after being treated in chemical environments such as acid, alkali and salt, the sensor still maintains a high conductivity. And after 7 hours of ultrasonic cleaning and 500 stretching cycles, the resistance of the sensor has only a small fluctuation, showing good environmental stability. (4) The hydrophobic fabric strain sensor can not only realize ordinary human motion monitoring, but also realize finger movement recognition in underwater environments such as acid, alkali and salt, as well as weak underwater vibration recognition. (5) The sensor’s lower detection limit and wider monitoring range can identify tiny deformations and a wide range of motion, which also makes it suitable for use in underwater monitoring scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a SEM image of the fiber surface of the nonwoven fabric of Example 1 of the present invention;

[0021] Figure 2 is a static contact angle diagram of the nonwoven fabric of Example 1 of the present invention;

[0022] Figure 3 is a SEM image of the fiber surface of the PDA-modified nonwoven fabric of Example 1 of the present invention;

[0023] Figure 4 is a SEM image of the fiber surface of the PDA / MWNTs nonwoven fabric of Example 1 of the present invention;

[0024] Figure 5 is a SEM image of the fiber surface of the PDA / MWNTs / AgNPs / PDMS nonwoven fabric of Example 1 of the present invention;

[0025] Figure 6 is a static contact angle diagram of the PDA / MWNTs / AgNPs / PDMS nonwoven fabric of Example 1 of the present invention;

[0026] Figure 7 is the wettability of the PDA / MWNTs / AgNPs / PDMS nonwoven fabric of Example 1 of the present invention to different solutions;

[0027] Figure 8 The hydrophobicity and electrical conductivity of the PDA / MWNTs / AgNPs / PDMS nonwoven fabric of Example 1 of the present invention under different external environments;

[0028] Fig. 9 In Example 1 of the present invention, the PDA / MWNTs / AgNPs / PDMS nonwoven fabric strain sensor recognizes finger movements and intermittent ultrasonic signals in acid, alkali and salt solutions. DETAILED DESCRIPTION

[0029] The present invention is described in further detail below.

[0030] Example 1

[0031] (1) A 5×5 cm nonwoven fabric was placed in a 0.5 wt % dopamine solution with a pH of 8.5 and a temperature of 35° C. The solution was shaken in a constant temperature water bath shaker for 24 h. The residue was washed with deionized water and placed in a 60° C. vacuum drying oven. After 15 min, the fabric was taken out for use.

[0032] (2) The polydopamine fabric prepared in step (1) was immersed in a 5 wt % aqueous dispersion of multi-walled carbon nanotubes, firstly ultrasonically immersed for 20 min, then naturally immersed for 30 min, placed in a 60° C. vacuum drying oven, and taken out after 15 min for use.

[0033] (3) The polydopamine / carbon nanotube fabric prepared in step (2) was immersed in a 5 wt % silver trifluoroacetate solution for 30 min, placed in a 60° C. vacuum drying oven for 15 min, taken out, and then immersed in a 3 wt % ascorbic acid solution for 30 min, placed in a 60° C. vacuum drying oven for 15 min, and taken out for use.

[0034] (4) The polydopamine / multi-walled carbon nanotube / nanosilver fabric prepared in step (3) was immersed in a 0.5wt% PDMS solution for 1 hour, placed in a 70°C vacuum drying oven, and taken out after 60 minutes, thereby successfully preparing a highly durable superhydrophobic fabric strain sensor.

[0035] Figure 1 This is a SEM of the nonwoven fabric fiber surface. It can be seen from the figure that the fiber is smooth. Figure 2 is the static contact angle of the nonwoven fabric, which is 134°, and it can be seen that the nonwoven fabric is in a hydrophobic state. By modifying the nonwoven fabric with PDA, the hydrophobic nonwoven fabric is transformed into a hydrophilic state, which is conducive to the attachment of MWNTs to the fiber surface. Figure 3 This is a picture of PDA material attached to the fiber surface. It can be observed that PDA is wrapped on the surface of the fiber and has a uniform morphology. Figure 4 The MWNTs are tightly wrapped on the surface of the PDA fibers. It can be observed that the MWNTs are wrapped on the PDA fibers and are tightly connected to form a complete conductive channel. Figure 5 AgNPs and PDMS are attached to the surface of the fiber. It can be seen that PDMS does not affect the morphology of the fiber surface. The double conductive network constructed by MWNTs and AgNPs not only improves the conductivity and sensing performance of the fabric, but also increases the roughness of the fiber. The combination of the rough fiber surface and PDMS makes the nonwoven fabric super hydrophobic. Figure 6 As shown, the static contact angle of the prepared PDA / MWNTs / AgNPs / PDMS nonwoven fabric is 156°. Figure 7 It was demonstrated that PDA / MWNTs / AgNPs / PDMS nonwoven fabrics have anti-wetting ability towards a variety of solutions. Figure 8 It was demonstrated that the PDA / MWNTs / AgNPs / PDMS nonwoven fabric still maintained its superhydrophobicity after 500 fatigue tests. Fig. 9It is demonstrated that the PDA / MWNTs / AgNPs / PDMS nonwoven fabric can identify underwater ultrasonic source signals and the state of underwater finger joint movement. Therefore, the super-hydrophobic and highly conductive fabric prepared by the present invention has good application value in wearable electronic devices, heaters, and underwater sensor monitoring.

[0036] Example 2

[0037] (1) A 5×5 cm nonwoven fabric was placed in a 0.5 wt % dopamine solution with a pH of 8 and a temperature of 35° C. The solution was shaken in a constant temperature water bath shaker for 24 h. The residue was washed with deionized water and placed in a 60° C. vacuum drying oven. After 15 min, the fabric was taken out for use.

[0038] (2) The polydopamine fabric prepared in step (1) was immersed in a 5 wt % aqueous dispersion of multi-walled carbon nanotubes, firstly ultrasonically immersed for 20 min, then naturally immersed for 30 min, placed in a 60° C. vacuum drying oven, and taken out after 15 min for use.

[0039] (3) The polydopamine / multi-walled carbon nanotube fabric prepared in step (2) was immersed in a 20 wt% silver trifluoroacetate solution for 30 min, placed in a 60°C vacuum drying oven for drying, and taken out after 15 min. It was then immersed in a 3 wt% ascorbic acid solution for 30 min, placed in a 60°C vacuum drying oven, and taken out after 15 min for use.

[0040] (4) The polydopamine / multi-walled carbon nanotube / nanosilver fabric prepared in step (3) was immersed in a 0.5wt% PDMS solution for 1 hour, placed in a 70°C vacuum drying oven, and taken out after 60 minutes, thereby successfully preparing a highly durable superhydrophobic fabric strain sensor.

[0041] Example 3

[0042] (1) A 5×5 cm nonwoven fabric was placed in a 0.8 wt % dopamine solution with a pH of 8.5 and a temperature of 35° C. The solution was shaken in a constant temperature water bath shaker for 24 h. The residue was washed with deionized water and placed in a 60° C. vacuum drying oven. After 15 min, the fabric was taken out for use.

[0043] (2) The polydopamine fabric prepared in step (1) was immersed in a 10 wt % single-walled carbon nanotube aqueous dispersion, firstly ultrasonically immersed for 20 min, then naturally immersed for 30 min, placed in a 60° C. vacuum drying oven, and taken out after 15 min for use.

[0044] (3) The polydopamine / single-walled carbon nanotube fabric prepared in step (2) was immersed in a 20 wt% silver trifluoroacetate solution for 30 min, placed in a 60°C vacuum drying oven for drying, and taken out after 15 min. It was then immersed in a 5 wt% ascorbic acid solution for 30 min, placed in a 60°C vacuum drying oven, and taken out after 15 min for use.

[0045] (4) The polydopamine / single-walled carbon nanotube / nanosilver fabric prepared in step (3) was immersed in a 2wt% PDMS ethyl acetate solution for 1 hour, placed in a 70°C vacuum drying oven, and taken out after 60 minutes, thereby successfully preparing a highly durable superhydrophobic fabric strain sensor.

[0046] Example 4

[0047] (1) A 5×5 cm nonwoven fabric was placed in a 0.6 wt % dopamine solution with a pH of 8.5 and a temperature of 35° C. The solution was shaken in a constant temperature water bath shaker for 24 h. The residue was washed with deionized water and placed in a 60° C. vacuum drying oven. After 15 min, the fabric was taken out for use.

[0048] (2) The polydopamine fabric prepared in step (1) was immersed in a 10 wt % carboxylated carbon nanotube aqueous dispersion, firstly ultrasonically immersed for 20 min, then naturally immersed for 30 min, placed in a 60° C. vacuum drying oven, and taken out after 15 min for use.

[0049] (3) The polydopamine / carboxylated carbon nanotube fabric prepared in step (2) was immersed in a 5 wt % silver trifluoroacetate solution for 30 min, placed in a 60° C. vacuum drying oven for 15 min, taken out, and then immersed in a 3 wt % ascorbic acid solution for 30 min, placed in a 60° C. vacuum drying oven for 15 min, and taken out for use.

[0050] (4) The polydopamine / carboxylated carbon nanotube / nanosilver fabric prepared in step (3) was immersed in a 0.5wt% PDMS ethyl acetate solution for 1 hour, placed in a 70°C vacuum drying oven, and taken out after 60 minutes, thereby successfully preparing a highly durable superhydrophobic fabric strain sensor.

Claims

1. A method for preparing a double conductive network super-hydrophobic fabric strain sensor, characterized in that: The following steps are involved: (1) subjecting the original nonwoven fabric to dopamine self-polymerization treatment to obtain a polydopamine fabric; the dopamine concentration is 0.5-0.8 wt%, the pH is 8-8.5, the reaction temperature is 20-40 °C, and the reaction time is 12-24 h; (2) immersing the polydopamine fabric in a carbon nanotube dispersion to obtain a carbon nanotube conductive fiber network, and then taking out and drying to obtain the polydopamine / carbon nanotube fabric; the concentration of the carbon nanotube dispersion is 5-10 wt%; (3) immersing the polydopamine / carbon nanotube fabric in a silver trifluoroacetate solution, taking it out and drying it, and then reducing it in an ascorbic acid solution to obtain a nanosilver conductive fiber network. The obtained fabric is a polydopamine / carbon nanotube / nanosilver fabric; (4) Placing the polydopamine / carbon nanotube / nanosilver fabric in a polydimethylsiloxane solution for hydrophobic treatment to obtain a hydrophobic strain sensor; the concentration of the polydimethylsiloxane solution is 0.5-2 wt%.

2. The method for preparing the double conductive network super-hydrophobic fabric strain sensor according to claim 1, characterized in that: In step (2), the carbon nanotubes are at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes or carboxylated carbon nanotubes.

3. The method for preparing the double conductive network super-hydrophobic fabric strain sensor according to claim 1, characterized in that: In step (2), the polydopamine fabric is placed in a carbon nanotube dispersion, first ultrasonicated for 10-20 min, and then immersed for 30-50 min.

4. The method for preparing the double conductive network super-hydrophobic fabric strain sensor according to claim 1, characterized in that: In step (3), the concentration of the silver trifluoroacetate solution is 5-20 wt%.

5. The method for preparing the double conductive network super-hydrophobic fabric strain sensor according to claim 1, characterized in that: In step (3), the polydopamine / carbon nanotube fabric is immersed in the silver trifluoroacetate solution for 30 to 60 minutes.

6. The method for preparing the double conductive network super-hydrophobic fabric strain sensor according to claim 1, characterized in that: In step (3), the concentration of the ascorbic acid solution is 3-10 wt%, and the reduction time is 30-60 min.

7. The method for preparing the double conductive network super-hydrophobic fabric strain sensor according to claim 1, characterized in that: In step (4), the solvent required for preparing the polydimethylsiloxane solution is ethyl acetate and / or n-hexane.

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