A wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric and its preparation method

Abstract

The present invention discloses a wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric and a preparation method thereof, belonging to the field of wearable piezoresistive sensors. The present invention aims to solve the technical problems of traditional fiber sensors such as low conductivity, unsatisfactory thickness, poor flexibility, complex preparation process and high cost. The present invention first coats polydopamine on mulberry silk fabric in a Tris salt solution, then adds silver nitrate and ascorbic acid to coat silver nanoparticles on the composite fiber fabric; then coats MXene on the composite fiber fabric by a multiple dip coating method; then uses an electrochemical method to coat a layer of polypyrrole on the surface of the composite fiber fabric, and finally uses 3M tape, PDMS and conductive silver paste to encapsulate it to obtain the sensor. The preparation method of the present invention is simple, low-cost, and has excellent performance. It has great development potential in the fields of health monitoring, sports monitoring, motion monitoring, artificial intelligence, wearable devices and human-computer interaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of wearable flexible sensors, and specifically relates to a piezoresistive sensor with a wearable flexible multi-layer structure based on mulberry silk fabric and a preparation method thereof; the piezoresistive sensor with a wearable flexible multi-layer structure based on mulberry silk fabric is mainly used in health monitoring, motion monitoring, artificial intelligence, wearable devices and human-computer interaction and other fields. Background Art

[0002] In recent years, with the rapid development of science and technology and people's expectations for a better life, the demand for flexible wearable sensors has been growing. Piezoresistive sensors, due to their simple principles, easy preparation, low cost, and excellent performance, have a wide range of applications in fields such as artificial intelligence, wearable electronic devices, health monitoring, motion monitoring, and human-computer interaction, and are increasingly attracting widespread attention from researchers. However, previous flexible wearable piezoresistive sensors still suffer from common problems such as low sensitivity, slow response speed, poor cyclic stability, poor wearability, and poor compatibility with the human body, which limit their application.

[0003] Problems with existing technologies:

[0004] The application of sensors with porous structures is restricted by their large thickness, poor wearability, and low sensitivity.

[0005] In two-dimensional microstructure sensors, due to technical limitations, the preparation of microstructures is not ideal, mainly due to the inability to prepare on a large scale, complex preparation process, high cost, low signal-to-noise ratio and unsatisfactory performance.

[0006] Traditional fiber fabric sensors have problems such as low conductivity, unsatisfactory thickness, poor flexibility, complex preparation process and high cost.

[0007] The packaging method is not ideal, and only simple tape packaging methods are used, which is difficult to apply to industrial production and practical applications. Summary of the Invention

[0008] The present invention aims to solve the above technical problems and provides a method for preparing a wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric.

[0009] In order to improve the performance of wearable flexible piezoresistive sensors based on fiber fabrics, researchers have applied a variety of conductive materials to the design of sensors. The conductive materials tried mainly include carbon materials (carbon black, carbon nanotubes, graphene, etc.), metal nanomaterials (metal nanowires, metal nanoparticles, etc.), MXene, metal organic frameworks, conductive polymers, etc.

[0010] AgNPs (silver nanoparticles) have a zero-dimensional nanostructure and excellent electrical conductivity. Loading AgNPs onto silk fabrics is simple, low-cost, and provides excellent conductivity without destroying the silk fabric structure. They can be used as a conductive material in flexible, wearable fabric sensors.

[0011] MXene is a novel two-dimensional material. It is a two-dimensional transition metal carbon / nitride with high electrical conductivity, excellent thermal conductivity, and good hydrophilicity. Its structural formula is Mn+1XnTx, where M is a transition metal (such as Ti, V, Zr), X is carbon or nitrogen, and T is a functional group (such as -OH, -O, -F, etc.) that imparts excellent hydrophilicity. MXene plays an important role in numerous applications, including supercapacitors, flexible sensors, energy, catalysis, and electromagnetic shielding. It is particularly well-suited for the fabrication of flexible piezoresistive sensors.

[0012] Polypyrrole is a typical conductive polymer that can be synthesized by chemical oxidation and electrochemical methods. It has the advantages of good air stability, easy electrochemical polymerization into film, high conductivity, good mechanical properties, and non-toxicity. It is very suitable for the production of flexible piezoresistive sensors.

[0013] Mulberry silk fiber fabric is a natural protein fiber fabric. It is particularly thin, soft, and light in weight, making it very suitable as a substrate for high-performance sensors and other smart devices.

[0014] PDMS is very suitable as a packaging material for flexible wearable sensors due to its good human compatibility, non-toxicity, excellent mechanical properties and easy preparation.

[0015] The invention adopts a method in which dopamine hydrochloride is added to a solution whose pH value is adjusted to 7.5-9.5 (preferably 8.3) by Tris salt to polymerize the solution, thereby coating polydopamine on mulberry silk fabric.

[0016] The invention adopts the method of adding a certain amount of silver nitrate and ascorbic acid into a solution and making them fully react, thereby coating a layer of silver nanoparticles on the mulberry silk composite fiber fabric.

[0017] The present invention adopts a multiple dip coating method to coat MXene onto the composite fiber fabric.

[0018] The present invention adopts an electrochemical method to coat a layer of polypyrrole on a composite fiber fabric. The method has the advantages of being non-toxic, harmless, highly controllable, highly efficient and low cost.

[0019] The present invention uses 3M tape, PDMS and conductive silver paste for packaging, so as to give full play to the performance of the sensor. The invention is characterized by being economical, simple and having superior performance.

[0020] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0021] The present invention provides a method for preparing a wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric, wherein the preparation method is carried out according to the following steps:

[0022] Step 1: washing the silk fiber fabric with acetone, anhydrous ethanol and deionized water in sequence;

[0023] Step 2: Add a certain amount of anhydrous ethanol and a certain amount of deionized water to a reaction vessel to obtain an ethanol-water solution, then weigh a certain amount of Tris and add it to the ethanol-water solution to adjust the pH value to 10.0-11.0, then weigh a certain amount of DA (acrylic acid-N,N-dimethylaminoethyl ester) and add it to the above solution, and measure the pH value with a pH meter to be 7.5-9.5. Add mulberry silk fiber fabric to the solution, stir it with a magnetic stirrer at room temperature for 24 hours, and then dry it in an oven to obtain PDA@mulberry silk fiber fabric;

[0024] Step 3: adding the PDA@silkworm fiber fabric obtained in step 1 to a certain amount of a certain concentration of AgNO3 solution and stirring at room temperature for a certain time, then gradually adding a certain amount of a certain concentration of ascorbic acid aqueous solution to the AgNO3 solution within a certain time, continuing to stir for a certain time and then stopping the reaction, taking out the fabric, washing it with a large amount of anhydrous ethanol and deionized water in sequence, and then drying it in an oven to obtain a fabric with a large amount of silver particles generated on the surface;

[0025] Step 4: Prepare MXene@Ag@PDA@silk fiber fabric by dip-coating method. The specific operation is as follows: dip-coat a certain amount of MXene dispersion of a certain concentration onto PDA@silk fiber fabric of a certain size and place it in an oven to dry;

[0026] Step 5: Repeat the dipping process in step 4 for 1 to 9 times;

[0027] Step 6. Electrochemical preparation of PPy@MXene@Ag@PDA@silk fiber fabric: Weigh a certain amount of pyrrole and a certain amount of p-toluenesulfonic acid, add a certain amount of ionized water, and stir evenly; then synthesize a polypyrrole film by electrochemical method; complete the preparation of PPy@MXene@Ag@PDA@silk fiber fabric, encapsulate it, and obtain the sensor.

[0028] Further defining, step six: Use conductive silver paste to connect flexible wires to the upper and lower fabric layers, creating a five-layer multilayer sensor. Then, seal them with 3M tape, apply a layer of PDMS resin, and place in an oven to cure. This completes the packaging.

[0029] The wire in step six is a copper wire with the insulation layer removed.

[0030] It is further defined that in step 2, the mass ratio of mulberry silk to solution is 1:20 to 1:100.

[0031] It is further defined that the concentration of silver nitrate in step three is 0.01 mol / mL to 0.08 mol / mL.

[0032] It is further defined that, based on a 4 cm×4 cm fabric, the amount of silver nitrate added in step 3 is 20 mL to 80 mL.

[0033] It is further defined that the concentration of the ascorbic acid aqueous solution in step 3 is 0.01 mol / mL to 0.08 mol / mL.

[0034] It is further defined that the amount of the ascorbic acid aqueous solution added in step 3 is 20 mL-80 mL.

[0035] It is further defined that the reaction time in step 3 is 0.5 hours to 4 hours.

[0036] It is further defined that the oven temperature in step 3 is 40°C-80°C.

[0037] It is further defined that the concentration of the MXene dispersion in step 4 is 2 mg / mL-10 mg / mL based on a 4 cm×4 cm fabric.

[0038] It is further defined that the amount of MXene dispersion added in step 4 is 0.1 mL-1 mL based on a 4 cm×4 cm fabric.

[0039] It is further defined that the concentration of pyrrole in step six is 2.5 mg / mL-0.02 g / mL.

[0040] It is further defined that the concentration of p-toluenesulfonic acid in step six is 0.02 g / mL-0.06 g / mL.

[0041] It is further defined that in step six, a constant current method is used to coat the polypyrrole.

[0042] Further, the current in step 6 is 5 mA / cm 2 -80mA / cm 2 .

[0043] It is further defined that the reaction time in step six is 10 min-120 min.

[0044] It is further defined that the materials used for packaging in step six are commercially available 3M tape and PDMS.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention adopts an economical and simple method to prepare PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric with excellent flexibility, mechanical properties and conductivity.

[0047] The present invention adopts a method of adding dopamine hydrochloride to a solution with a pH value adjusted to 7.5-9.5 (preferably 8.3) by Tris salt to polymerize the solution, thereby coating polydopamine on mulberry silk fabric. The method is economical, simple, and has very ideal effects.

[0048] The present invention adopts a method of adding a certain amount of silver nitrate and ascorbic acid into a solution and allowing them to fully react to coat a layer of silver nanoparticles on a mulberry silk composite fiber fabric. The method is economical, simple, and has very ideal effects.

[0049] The present invention uses a multiple-dip coating method to coat MXene onto a composite fiber fabric. This method is economical, simple, and has very ideal results.

[0050] The present invention adopts an electrochemical method to coat a layer of polypyrrole on a composite fiber fabric. The method has the advantages of being non-toxic, harmless, highly controllable, highly efficient and low cost.

[0051] The present invention uses 3M tape, PDMS and conductive silver paste for packaging, so as to give full play to the performance of the sensor. The invention is characterized by being economical, simple and having superior performance.

[0052] The present invention uses silver nanoparticles, MXene and polypyrrole as raw materials, and in a solution with a pH value of 8.3 adjusted by Tris salt, polydopamine is coated on a mulberry silk fabric, and then a certain amount of silver nitrate and ascorbic acid are added to coat a layer of silver nanoparticles on the mulberry silk composite fiber fabric. Subsequently, a commercially available MXene dispersion is used to coat the composite fiber fabric by multiple dip coating methods, and then a layer of polypyrrole is coated on the surface of the composite fiber fabric using an electrochemical method. Finally, commercially available 3M tape, PDMS and conductive silver paste are used to encapsulate it to obtain a wearable flexible multilayer piezoresistive sensor based on mulberry silk fabric. The present invention greatly improves the performance of the sensor by using a thin, soft mulberry silk fiber fabric and a multilayer structure. When the sensor is compressed and deformed, the fiber fabric is squeezed, which changes the contact between the fabrics, forms a large number of new conductive paths, and increases the contact area between the fiber fabrics, thereby reducing the resistance of the sensor. The sensor preparation method of the present invention is simple, low-cost, and has excellent performance. It has great development potential in the fields of health monitoring, sports monitoring, motion monitoring, artificial intelligence, wearable devices, and human-computer interaction.

[0053] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a sensitivity test graph of a wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of Example 1;

[0055] Figure 2 This is a cyclic stability test chart of a wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of Example 1;

[0056] Figure 3 This is a sensitivity test chart of the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of Example 1 at different temperatures;

[0057] Figure 4 is a diagram of the application test of the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of Example 1, in which a—elbow joint activity monitoring, b—knee joint activity monitoring, c—finger joint activity monitoring, d—wrist joint activity monitoring, e—speech monitoring, f—speech monitoring, and g—speech monitoring;

[0058] Figure 5 is the XRD spectrum of a series of composite fiber fabrics prepared by the method of Example 1. In Figure 5, a is the XRD spectrum of mulberry silk fiber fabric, b is the XRD spectrum of PDA@mulberry silk fiber fabric, c is the XRD spectrum of Ag@PDA@mulberry silk fiber fabric, d is the XRD spectrum of MXene@Ag@PDA@mulberry silk fiber fabric, and e is the XRD spectrum of PPy@MXene@Ag@PDA@mulberry silk fiber fabric.

[0059] Figure 6 These are SEM images of a series of composite fiber fabrics prepared by the method of Example 1. DETAILED DESCRIPTION

[0060] The present invention will be further described below with reference to specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0061] The thickness of the 3M tape used in the following examples is 0.5 mm.

[0062] Example 1:

[0063] The preparation method of the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric in this embodiment is carried out according to the following steps:

[0064] Step 1: Take a 4cm×4cm piece of mulberry silk fiber fabric and wash it with acetone, anhydrous ethanol and deionized water in sequence;

[0065] Step 2: Add 150 mL of anhydrous ethanol and 350 mL of deionized water to a 500 mL beaker to obtain an ethanol aqueous solution, weigh 0.4325 g of Tris and add it to the ethanol aqueous solution to adjust the pH value. The pH value was measured by a pH meter and was 10.3. Then, weigh 1.4020 g of DA and add it to the above solution. The pH value was measured by a pH meter and was 8.3. The mulberry silk fiber fabric treated in step 1 was added to the above solution (by mass, solid-liquid ratio 1:50) and stirred with a magnetic stirrer at room temperature for 24 hours.

[0066] Step 3: PDA@ mulberry silk fiber fabric was added to 50 mL of 0.04 mol / mL AgNO3 solution and stirred at room temperature for 20 minutes. 50 mL of 0.05 mol / mL ascorbic acid aqueous solution was gradually added to the AgNO3 solution within 25 minutes. The mixture was stirred for 2 hours. After stopping the reaction, the fabric was taken out and washed with a large amount of anhydrous ethanol and deionized water in sequence. It was then dried in an oven at 60°C to obtain a fabric with a large number of silver particles generated on the surface, i.e., Ag@PDA@ mulberry silk fiber fabric was obtained.

[0067] Step 4: Dip-coat 0.25 mL of 5 mg / mL MXene dispersion onto the PDA@ mulberry silk fiber fabric and dry it in a 60 °C oven.

[0068] Step 5: Repeat step 4 5 times to obtain MXene@Ag@PDA@silk fiber fabric;

[0069] Step 6: Electrochemical preparation of PPy@MXene@Ag@PDA@ mulberry silk fiber fabric. The specific operation is: weigh 1.3505g of pyrrole and 6.8552g of p-toluenesulfonic acid, add them to 200mL of deionized water, stir evenly, and then electrochemically synthesize polypyrrole film using a constant current method with a current of 20mA / cm 2 The electrode is the prepared MXene@Ag@PDA@silk fiber fabric, the inter-electrode distance is 1 cm, and the reaction time is 90 minutes. The preparation of PPy@MXene@Ag@PDA@silk fiber fabric is completed;

[0070] Step 7: Encapsulate the sensor: Use conductive silver paste to connect soft wires to the upper and lower layers of fiber fabric, and then prepare a 5-layer multilayer structure sensor. Then, use 3M tape to seal it. Finally, apply a layer of PDMS resin on its surface and put it into an oven to cure it to complete its encapsulation.

[0071] The method for encapsulating the sensor with the PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric prepared by the above method is completed by the following steps:

[0072] Step (1), cutting the effective part of the prepared PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric into a size of 1 cm×1 cm, while leaving a lead portion for connecting a copper wire;

[0073] Step (2): Use a small amount of conductive silver paste to fix the soft wire to the lead-out portion of the pleated film. Place it in a 110°C oven and cure for 10 minutes to complete the wire connection.

[0074] Step (3), align the centers of the five layers of PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric on one side of the 3M tape and then stick a new piece of 3M tape (12 cm × 12 cm in size), then place the folds of the two electrodes face to face and stagger the wires, and stick them together;

[0075] Step (4): Coat the upper and lower surfaces of the bonded sensor with a layer of PDMS and place it in a 110°C oven for curing for 10 minutes. Remove the sensor and cool it to room temperature to complete the sensor packaging.

[0076] The sensitivity test of the wearable flexible multilayer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment is as follows Figure 1 As shown by Figure 1 It can be seen that the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment has a high sensitivity under small strain, a moderate sensitivity under medium strain, and a very low sensitivity under large strain.

[0077] The cyclic stability test of the wearable flexible multilayer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment is as follows Figure 2 As shown by Figure 2 It can be seen that the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment can still be used normally after 1000 cycles.

[0078] The sensitivity test of the wearable flexible multilayer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment at different temperatures is as follows: Figure 3 As shown by Figure 3 It can be seen that the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment can still be used normally at -20℃, 0℃, 20℃, 40℃, 60℃ and 80℃.

[0079] The application test of the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment is shown in Figure 4. As can be seen from Figure 4, the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric prepared by the method of this embodiment can realize the detection of pulse, voice, large joint movement and small joint movement.

[0080] The XRD spectra of a series of composite fiber fabrics prepared by the method of this embodiment are shown in FIG5 . As shown in FIG5 , in the series of composite fiber fabrics prepared by the method of this embodiment, the loaded substances are well loaded onto the mulberry fiber fabrics.

[0081] A series of SEM electron microscope images of composite fiber fabrics according to the present embodiment are shown in FIG. Figure 6 As shown by Figure 6 It can be seen that the series of composite fiber fabrics prepared by the method of this embodiment have uniform distribution of loaded substances and ideal coating effects.

[0082] Example 2:

[0083] The preparation method of the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric in this embodiment is carried out according to the following steps:

[0084] Step 1: Take a 4cm×4cm piece of mulberry silk fiber fabric and wash it with acetone, anhydrous ethanol and deionized water in sequence;

[0085] Step 2: Add 200 mL of anhydrous ethanol and 300 mL of deionized water to a 500 mL beaker to obtain an ethanol-water solution, then weigh 0.6 g of Tris and add it to the ethanol-water solution to adjust the pH value. The pH value was measured to be 10.3 using a pH meter. Then weigh 2 g of DA and add it to the above solution. The pH value was measured to be 8.3 using a pH meter. The mulberry silk fiber fabric treated in step 1 was added to the above solution (by mass, solid-liquid ratio 1:50) and stirred at room temperature with a magnetic stirrer for 24 hours.

[0086] Step 3: PDA@ mulberry silk fiber fabric was added to 40 mL of 0.08 mol / mL AgNO3 solution and stirred at room temperature for 30 minutes. 60 mL of 0.06 mol / mL ascorbic acid aqueous solution was gradually added to the AgNO3 solution within 25 minutes. The mixture was stirred for 2.5 hours. After stopping the reaction, the fabric was taken out and washed with a large amount of anhydrous ethanol and deionized water in sequence. It was then dried in an oven at 60°C to obtain a fabric with a large number of silver particles generated on the surface, i.e., Ag@PDA@ mulberry silk fiber fabric was obtained.

[0087] Step 4: Dip-coat 0.5 mL of 5 mg / mL MXene dispersion onto a 4 × 4 cm PDA@ mulberry silk fabric and dry it in a 60 °C oven.

[0088] Step 5: Repeat step 4 6 times to obtain MXene@Ag@PDA@silk fiber fabric;

[0089] Step 6: Electrochemical preparation of PPy@MXene@Ag@PDA@ mulberry silk fiber fabric. Weigh 2g of pyrrole and 8g of p-toluenesulfonic acid, add them to 200mL of deionized water, stir evenly, and then electrochemically synthesize polypyrrole film using a constant current method with a current of 40mA / cm 2 The electrode is the prepared MXene@Ag@PDA@silk fiber fabric, the inter-electrode distance is 1 cm, and the reaction time is 30 min to complete the preparation of PPy@MXene@Ag@PDA@silk fiber fabric;

[0090] Step 7: Encapsulate the sensor: Use conductive silver paste to connect soft wires to the upper and lower layers of fiber fabric, and then prepare a 7-layer multilayer structure sensor. Then, use 3M tape to seal it, and finally apply a layer of PDMS resin on its surface and put it into an oven to cure it to complete its encapsulation.

[0091] The method for encapsulating the sensor with the PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric prepared by the above method is completed by the following steps:

[0092] Step (1), cutting the effective part of the prepared PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric into a size of 2×2 cm, while leaving a lead portion for connecting a copper wire;

[0093] Step (2): Use a small amount of conductive silver paste to fix the soft wire to the lead-out portion of the pleated film. Place it in a 110°C oven and cure for 10 minutes to complete the wire connection.

[0094] Step (3), align the centers of the 7-layer PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric on one side of the 3M tape and then stick a new piece of 3M tape (12 cm × 12 cm in size), then place the folds of the two electrodes face to face and stagger the wires, and stick them together;

[0095] Step (4): Coat the upper and lower surfaces of the bonded sensor with a layer of PDMS and place it in a 110°C oven for curing for 10 minutes. Remove the sensor and cool it to room temperature to complete the sensor packaging.

[0096] Example 3:

[0097] The preparation method of the wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric in this embodiment is carried out according to the following steps:

[0098] Step 1: Take a 4cm×4cm piece of mulberry silk fiber fabric and wash it with acetone, anhydrous ethanol and deionized water in sequence;

[0099] Step 2: Add 200 mL of anhydrous ethanol and 300 mL of deionized water to a 500 mL beaker to obtain an ethanol-water solution. Weigh 0.5 g of Tris and add it to the ethanol-water solution to adjust the pH. The pH value was measured to be 10.3 using a pH meter. Weigh 3 g of DA and add it to the solution. The pH value was measured to be 8.3 using a pH meter. Add the mulberry silk fiber fabric treated in step 1 to the solution (by mass, solid-to-liquid ratio 1:50) and stir with a magnetic stirrer at room temperature for 24 hours.

[0100] Step 3: Add PDA@ mulberry silk fiber fabric to 40 mL of 0.1 mol / mL AgNO3 solution and stir at room temperature for 30 minutes. Gradually add 60 mL of 0.05 mol / mL ascorbic acid aqueous solution to the above AgNO3 solution within 25 minutes, continue stirring for 3 hours, stop the reaction, take out the fabric, wash it with a large amount of anhydrous ethanol and deionized water in turn, and then place it in a 60°C oven to dry, to obtain a fabric with a large number of silver particles generated on the surface, that is, to obtain Ag@PDA@ mulberry silk fiber fabric;

[0101] Step 4: Dip-coat 0.2 mL of 10 mg / mL MXene dispersion onto the PDA@ mulberry silk fiber fabric and dry it in a 60 °C oven.

[0102] Step 5: Repeat step 4 6 times to obtain MXene@Ag@PDA@silk fiber fabric;

[0103] Step 6: Electrochemical preparation of PPy@MXene@Ag@PDA@ mulberry silk fiber fabric. The specific operation is: weigh 4g of pyrrole and 8g of p-toluenesulfonic acid, add them to 200mL of deionized water, stir evenly, and then electrochemically synthesize polypyrrole film using a constant current method with a current of 60mA / cm 2 The electrode is the prepared MXene@Ag@PDA@silk fiber fabric, the inter-electrode distance is 2 cm, and the reaction time is 20 min to complete the preparation of PPy@MXene@Ag@PDA@silk fiber fabric;

[0104] Step 7: Sensor Encapsulation: Conductive silver paste is used to connect flexible wires to the upper and lower fabric layers, creating a nine-layer multilayer sensor. 3M tape is then used to seal the sensor, followed by a layer of PDMS resin applied to the surface and cured in an oven, completing the encapsulation.

[0105] The method for encapsulating the sensor with the PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric prepared by the above method is completed by the following steps:

[0106] Step (1), cutting the effective part of the prepared PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric into a size of 1×1 cm, while leaving a lead portion for connecting a copper wire;

[0107] Step (2): Use a small amount of conductive silver paste to fix the soft wire to the lead-out portion of the pleated film. Place it in a 110°C oven and cure for 10 minutes to complete the wire connection.

[0108] Step (3), align the centers of 9 layers of PPy@MXene@Ag@PDA@mulberry silk composite fiber fabric on one side of the 3M tape and then stick a new piece of 3M tape (12 cm × 12 cm in size), then place the folds of the two electrodes face to face and stagger the wires, and stick them together;

[0109] Step (4): Coat the upper and lower surfaces of the bonded sensor with a layer of PDMS and place it in a 110°C oven for curing for 10 minutes. Remove the sensor and cool it to room temperature to complete the sensor packaging.

Claims

1. A method for preparing a wearable flexible multi-layer piezoresistive sensor based on mulberry silk fabric, characterized in that The preparation method is carried out according to the following steps: Step 1: washing the silk fiber fabric with acetone, anhydrous ethanol and deionized water in sequence; Step 2: Mix anhydrous ethanol and deionized water, add Tris to adjust the pH to 10.0-11.0, then add DA to control the pH to 7.5-9.5, then add the mulberry silk fiber fabric treated in step 1, and then stir at room temperature for 24 hours, and then dry to obtain PDA@mulberry silk fiber fabric; Step 3: Add the PDA@ mulberry silk fiber fabric to the AgNO3 solution, stir at room temperature, add ascorbic acid aqueous solution dropwise while stirring, continue stirring, take out the fabric after the reaction is complete, wash it with anhydrous ethanol and deionized water in sequence, and then dry it to obtain the PDA@ mulberry silk fiber fabric; Step 4: Dip-coat the MXene dispersion onto the PDA@ mulberry silk fiber fabric and then dry it; Repeat steps 5 and 4 1 to 9 times; Step 6: Pyrrole and p-toluenesulfonic acid are mixed in deionized water, stirred evenly, and the fabric treated in step 5 is added, and polypyrrole is coated by electrochemical method to obtain PPy@MXene@Ag@PDA@mulberry silk fiber fabric, which is then encapsulated to obtain the sensor; The concentration of the MXene dispersion in step 4 is 2 mg / mL-10 mg / mL.

2. The preparation method according to claim 1, characterized in that In step 2, the mass ratio of the mulberry silk fiber fabric to the solution is 1: (20-100).

3. The preparation method according to claim 1, characterized in that The concentration of the AgNO3 solution in step 3 is 0.01 mol / mL to 0.08 mol / mL; the concentration of the ascorbic acid aqueous solution in step 3 is 0.01 mol / mL to 0.08 mol / mL.

4. The preparation method according to claim 1, characterized in that The reaction time in step 3 is 0.5 h-4 h.

5. The preparation method according to claim 1, characterized in that In step 3, the oven temperature is 40°C-80°C.

6. The preparation method according to claim 1, characterized in that In step six, the concentration of pyrrole is 2.5 mg / mL-0.02 g / mL; the concentration of p-toluenesulfonic acid is 0.02 g / mL-0.06 g / mL.

7. The preparation method according to claim 1, characterized in that The electrochemical method in step 6 is a constant current method; wherein the current is controlled at 5 mA / cm 2 -80mA / cm 2 , the reaction time is 10min-120min.

8. The preparation method according to claim 1, characterized in that The sensor described in step six is encapsulated by at least three layers of PPy@MXene@Ag@PDA@mulberry silk fiber fabric.

9. A wearable flexible piezoresistive sensor prepared by the method according to any one of claims 1 to 8.

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