Preparation method and application of a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel

Abstract

The application belongs to the technical field of polymer photoelectric materials, and particularly relates to a preparation method of a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel and application thereof. A mixed aqueous solution A of carboxymethyl cellulose and sodium lignosulfonate is prepared. Liquid metal is added into the mixed aqueous solution A and ultrasonically treated to obtain a solution B. Acrylic acid is added into the solution B, and a crosslinking agent and an initiator are added after uniform stirring to obtain a solution C. The solution C is introduced into a mold for in-situ polymerization to obtain a hydrogel D. The hydrogel D is placed on a prepared polydimethylsiloxane elastomer film, copper electrodes are connected on both sides of the hydrogel through conductive silver paste, and the polydimethylsiloxane elastomer film is wrapped to obtain the flexible strain sensor. The wearable strain sensor has strong adhesion to various substrates, very stable conductivity, good flexibility and stable sensing of human body movement.

Description

Technical Field

[0001] This invention belongs to the field of polymer optoelectronic materials technology, and particularly relates to a method for preparing a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel and its application. Background Technology

[0002] Flexible wearable electronics is a cutting-edge research field, with a significant demand for highly flexible and multifunctional wearable electronic devices. Therefore, flexible wearable electronic devices with self-healing capabilities, photothermal conversion abilities, and high sensitivity have attracted widespread attention and hold promise for applications in disease diagnosis, human motion and health monitoring, and electronic skin. However, due to the high surface tension of liquid metals, they are difficult to disperse uniformly within hydrogels, leading to stress concentration and resulting in drawbacks such as low tensile strength, inherent brittleness, and low durability. Therefore, fabricating a wearable strain sensor with high durability, high sensitivity, and multifunctionality remains a significant challenge. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for fabricating a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel and its application. This method overcomes the defects of existing wearable strain sensors based on conductive hydrogels, such as low tensile strength, inherent brittleness, and low durability. The fabricated sensor possesses advantages such as self-healing, adhesiveness, and high sensing sensitivity, while also exhibiting good mechanical properties and durability.

[0004] The technical solution provided by this invention is as follows:

[0005] This invention provides a method for fabricating a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, comprising the following steps:

[0006] Prepare a mixed aqueous solution A of carboxymethyl cellulose and sodium lignosulfonate;

[0007] Liquid metal is added to a mixed aqueous solution A and ultrasonically treated to obtain solution B;

[0008] Acrylic acid was added to solution B, and after stirring until homogeneous, a crosslinking agent and an initiator were added to obtain solution C.

[0009] Solution C was introduced into a mold for in-situ polymerization to obtain hydrogel D;

[0010] Preparation of polydimethylsiloxane elastomer films;

[0011] Hydrogel D was placed on the prepared polydimethylsiloxane elastomer film, and copper electrodes were connected to both sides of hydrogel D by conductive silver paste. The hydrogel D was then wrapped with the polydimethylsiloxane elastomer film to obtain a flexible strain sensor.

[0012] Furthermore, the mass-to-volume ratio of carboxymethyl cellulose, sodium lignosulfonate, and water in the mixture A is 0.05~0.125:0.02:16 g / g / mL.

[0013] Furthermore, the mass-to-volume ratio of carboxymethyl cellulose, sodium lignosulfonate, and water in the mixed aqueous solution A is 0.1:0.02:16 g / g / mL.

[0014] Furthermore, the liquid metal is a gallium-indium alloy, wherein the mass ratio of metallic gallium to metallic indium in the gallium-indium alloy is 75.5:24.5, and the amount of gallium-indium alloy added is 0.3g.

[0015] Furthermore, the ultrasonic treatment power in S2 is 450-500W, and the treatment time is 80-90min.

[0016] Furthermore, the amount of acrylic acid added is 4g, and the crosslinking agent and initiator are N'N-methylenebisacrylamide and ammonium persulfate, respectively.

[0017] Furthermore, the method for preparing the polydimethylsiloxane elastomer film includes:

[0018] Weigh out a polydimethylsiloxane solution, add a curing agent and stir thoroughly. Drop the mixture onto a glass slide and level it. After vacuum curing, peel it off from the glass slide to obtain a film.

[0019] Furthermore, the amount of polydimethylsiloxane solution added is 1g~2g, the amount of curing agent added is 0.1g~0.2g, and the vacuum curing time is 40~60min.

[0020] Furthermore, the curing agent is diphenylcarbamate butyl ester.

[0021] The present invention also provides the application of the flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared by the above-described preparation method in wearable flexible electronic devices.

[0022] Beneficial effects

[0023] 1. In conductive hydrogels, the difficulty in uniformly dispersing conductive materials leads to stress concentration, resulting in low tensile strength, inherent brittleness, and low durability, hindering the practical application of wearable strain sensors based on conductive hydrogels. This invention constructs a dual-network conductive hydrogel using polyacrylic acid and carboxymethyl cellulose. Furthermore, the abundant negatively charged carboxyl groups on the surface of carboxymethyl cellulose allow for the uniform dispersion of the conductive liquid metal within the hydrogel matrix through electrostatic repulsion. This significantly improves the mechanical properties, toughness, and conductive stability of the conductive hydrogel, broadening the practical application range of wearable strain sensors based on conductive hydrogels.

[0024] 2. Self-adhesion is a crucial performance characteristic for wearable electronic devices. However, typical wearable strain sensors based on conductive hydrogels lack this property, limiting their practical application. Sulfonated lignin, with its abundant catechol groups in its chemical structure, can adhere to various substrates through both non-covalent and covalent chemical bonding.

[0025] 3. The water retention capacity of conductive hydrogels greatly affects their conductivity. Coating carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel with a polydimethylsiloxane elastomer film can slow down the evaporation of water from the hydrogel, thereby extending the service life of wearable strain sensors based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel. Attached Figure Description

[0026] Figure 1 It is based on the stress-strain curve of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel under tensile test;

[0027] Figure 2 It is based on the adhesion strength of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel to different substrates in the adhesion and peel test;

[0028] Figure 3 It is based on the output voltage curve of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel under simulated sunlight;

[0029] Figure 4 These are photographs and current-time variation curves of a wearable strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel at different finger bending angles (0°, 30°, 60° and 90°);

[0030] Figure 5These are photos of a wearable strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel during writing, along with its current-time variation curve.

[0031] Figure 6 It is a wearable strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel that transmits Morse code current-time change curves through long and short presses. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings. The following examples are used to more clearly illustrate the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0033] This invention provides a method for fabricating a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, comprising the following steps:

[0034] Prepare a mixed aqueous solution A of carboxymethyl cellulose and sodium lignosulfonate;

[0035] Liquid metal is added to a mixed aqueous solution A and ultrasonically treated to obtain solution B;

[0036] Acrylic acid was added to solution B, and after stirring until homogeneous, a crosslinking agent and an initiator were added to obtain solution C.

[0037] Solution C was introduced into a mold for in-situ polymerization to obtain hydrogel D;

[0038] Preparation of polydimethylsiloxane elastomer films;

[0039] Hydrogel D was placed on the prepared polydimethylsiloxane elastomer film, and copper electrodes were connected to both sides of hydrogel D by conductive silver paste. The hydrogel D was then wrapped with the polydimethylsiloxane elastomer film to obtain a flexible strain sensor.

[0040] In this embodiment, the mass-to-volume ratio of carboxymethyl cellulose, sodium lignosulfonate, and water in the mixture A is 0.05~0.125:0.02:16 g / g / mL.

[0041] Preferably, the mass-to-volume ratio of carboxymethyl cellulose, sodium lignosulfonate, and water in the mixed aqueous solution A is 0.1:0.02:16 g / g / mL.

[0042] In this embodiment, the liquid metal is a gallium-indium alloy, the mass ratio of gallium to indium in the gallium-indium alloy is 75.5:24.5, and the amount of gallium-indium alloy added is 0.3g.

[0043] In this embodiment, the power of the ultrasonic treatment in S2 is 450-500W, preferably 500W, and the treatment time is 80-90min, preferably 90min.

[0044] In this embodiment, the amount of acrylic acid added is 4g, and the crosslinking agent and initiator are N'N-methylenebisacrylamide and ammonium persulfate, respectively.

[0045] In this embodiment, the method for preparing the polydimethylsiloxane elastomer film includes:

[0046] Weigh out a polydimethylsiloxane solution, add a curing agent and stir thoroughly. Drop the mixture onto a glass slide and level it. After vacuum curing, peel it off from the glass slide to obtain a film.

[0047] In this embodiment, the amount of polydimethylsiloxane solution added is 1g~2g, the amount of curing agent added is 0.1g~0.2g, and the vacuum curing time is 40~60min.

[0048] In this embodiment, the curing agent is diphenylcarbamate butyl ester.

[0049] This invention also provides the application of the flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared by the above-described method in wearable flexible electronic devices.

[0050] Example 1

[0051] Step 1, the preparation of the carboxymethyl cellulose-liquid metal nanocomposite suspension, i.e., solution B, includes the following specific steps:

[0052] (1) Weigh 0.05g of carboxymethyl cellulose and add it to 16 mL of aqueous solution containing 0.02g of sodium lignosulfonate. Stir and mix the solution at 65°C using a magnetic stirrer to obtain aqueous solution A.

[0053] (2) Slowly add 0.3g of liquid metal to the solution in (1) for a certain period of time to pretreat and obtain a suspension of carboxymethyl cellulose-liquid metal nanocomposite.

[0054] Step 2, the preparation of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension, i.e., solution C, includes the following specific steps:

[0055] Add 4g of acrylic acid to the carboxymethyl cellulose-liquid metal nanocomposite suspension prepared in step 1, stir for 3-5 minutes, and after stirring evenly, add 0.02g of N'N-methylenebisacrylamide and 0.05g of ammonium persulfate to form a carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension.

[0056] Step 3, the preparation of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, i.e., hydrogel D, includes the following specific steps:

[0057] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-acrylic acid suspension prepared in step 2 was introduced into a mold and in-situ polymerized at 25~30℃ to obtain carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0058] Step 4, the preparation of the polydimethylsiloxane elastomer film, includes the following specific steps:

[0059] (1) Weigh 1~2g of polydimethylsiloxane solution, add 0.1~0.2g of curing agent (diphenylcarbamate), stir the mixture thoroughly with a magnetic stirrer, and let it stand for 30~40min;

[0060] (2) Weigh 1~2g of the mixture prepared in step (1) and drop it onto a glass slide to level it. Place it in a vacuum oven to cure for 40~60min. Peel it off from the glass slide to obtain a thin film of polydimethylsiloxane elastomer. Prepare another piece of polydimethylsiloxane elastomer using the same method.

[0061] Step 5, the fabrication of the flexible strain sensor, includes the following specific steps:

[0062] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared in step 3 is placed on the polydimethylsiloxane elastomer film prepared in step 4. Two copper electrodes are connected to both sides of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel through conductive silver paste. The system is then wrapped with the polydimethylsiloxane elastomer film to obtain a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0063] Example 2

[0064] Step 1, the preparation of the carboxymethyl cellulose-liquid metal nanocomposite suspension, i.e., solution B, includes the following specific steps:

[0065] (1) Weigh 0.075g of carboxymethyl cellulose and add it to 16 mL of aqueous solution containing 0.02g of sodium lignosulfonate. Stir and mix the solution at 65°C using a magnetic stirrer to obtain aqueous solution A.

[0066] (2) Slowly add 0.3g of liquid metal to the solution in (1) for a certain period of time to pretreat and obtain a suspension of carboxymethyl cellulose-liquid metal nanocomposite.

[0067] Step 2, the preparation of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension, i.e., solution C, includes the following specific steps:

[0068] Add 4g of acrylic acid to the carboxymethyl cellulose-liquid metal nanocomposite suspension prepared in step 1, stir for 3-5 minutes, and after stirring evenly, add 0.02g of N'N-methylenebisacrylamide and 0.05g of ammonium persulfate to form a carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension.

[0069] Step 3, the preparation of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, i.e., hydrogel D, includes the following specific steps:

[0070] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-acrylic acid suspension prepared in step 2 was introduced into a mold and in-situ polymerized at 25~30℃ to obtain carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0071] Step 4, the preparation of the polydimethylsiloxane elastomer film, includes the following specific steps:

[0072] (1) Weigh 1~2g of polydimethylsiloxane solution, add 0.1~0.2g of curing agent (diphenylcarbamate), stir the mixture thoroughly with a magnetic stirrer, and let it stand for 30~40min;

[0073] (2) Weigh 1~2g of the mixture prepared in step (1) and drop it onto a glass slide to level it. Place it in a vacuum oven to cure for 40~60min. Peel it off from the glass slide to obtain a thin film of polydimethylsiloxane elastomer. Prepare another piece of polydimethylsiloxane elastomer using the same method.

[0074] Step 5, the fabrication of the flexible strain sensor, includes the following specific steps:

[0075] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared in step 3 is placed on the polydimethylsiloxane elastomer film prepared in step 4. Two copper electrodes are connected to both sides of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel through conductive silver paste. The system is then wrapped with the polydimethylsiloxane elastomer film to obtain a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0076] Example 3

[0077] Step 1, the preparation of the carboxymethyl cellulose-liquid metal nanocomposite suspension, i.e., solution B, includes the following specific steps:

[0078] (1) Weigh 0.1g of carboxymethyl cellulose and add it to 16 mL of aqueous solution containing 0.02g of sodium lignosulfonate. Stir and mix the solution at 65°C using a magnetic stirrer to obtain aqueous solution A.

[0079] (2) Slowly add 0.3g of liquid metal to the solution in (1) for a certain period of time to pretreat and obtain a suspension of carboxymethyl cellulose-liquid metal nanocomposite.

[0080] Step 2, the preparation of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension, i.e., solution C, includes the following specific steps:

[0081] Add 4g of acrylic acid to the carboxymethyl cellulose-liquid metal nanocomposite suspension prepared in step 1, stir for 3-5 minutes, and after stirring evenly, add 0.02g of N'N-methylenebisacrylamide and 0.05g of ammonium persulfate to form a carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension.

[0082] Step 3, the preparation of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, includes the following specific steps:

[0083] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-acrylic acid suspension prepared in step 2 was introduced into a mold and in-situ polymerized at 25~30℃ to obtain carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0084] Step 4, the preparation of the polydimethylsiloxane elastomer film, includes the following specific steps:

[0085] (1) Weigh 1~2g of polydimethylsiloxane solution, add 0.1~0.2g of curing agent (diphenylcarbamate), stir the mixture thoroughly with a magnetic stirrer, and let it stand for 30~40min;

[0086] (2) Weigh 1~2g of the mixture prepared in step (1) and drop it onto a glass slide to level it. Place it in a vacuum oven to cure for 40~60min. Peel it off from the glass slide to obtain a thin film of polydimethylsiloxane elastomer. Prepare another piece of polydimethylsiloxane elastomer using the same method.

[0087] Step 5, the fabrication of the flexible strain sensor, includes the following specific steps:

[0088] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared in step 3 is placed on the polydimethylsiloxane elastomer film prepared in step 4. Two copper electrodes are connected to both sides of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel through conductive silver paste. The system is then wrapped with the polydimethylsiloxane elastomer film to obtain a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0089] Example 4

[0090] Step 1, the preparation of the carboxymethyl cellulose-liquid metal nanocomposite suspension, i.e., solution B, includes the following specific steps:

[0091] (1) Weigh 0.125g of carboxymethyl cellulose and add it to 16 mL of aqueous solution containing 0.02g of sodium lignosulfonate. Stir and mix the solution at 65°C using a magnetic stirrer to obtain aqueous solution A.

[0092] (2) Slowly add 0.3g of liquid metal to the solution in (1) for a certain period of time to pretreat and obtain a suspension of carboxymethyl cellulose-liquid metal nanocomposite.

[0093] Step 2, the preparation of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension, i.e., solution C, includes the following specific steps:

[0094] Add 4g of acrylic acid to the carboxymethyl cellulose-liquid metal nanocomposite suspension prepared in step 1, stir for 3-5 minutes, and after stirring evenly, add 0.02g of N'N-methylenebisacrylamide and 0.05g of ammonium persulfate to form a carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid suspension.

[0095] Step 3, the preparation of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, i.e., hydrogel D, includes the following specific steps:

[0096] The carboxymethyl cellulose-liquid metal-sodium lignosulfonate-acrylic acid suspension prepared in step 2 was introduced into a mold and in-situ polymerized at 25~30℃ to obtain carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0097] Step 4, the preparation of the polydimethylsiloxane elastomer film, includes the following specific steps:

[0098] (1) Weigh 1~2g of polydimethylsiloxane solution, add 0.1~0.2g of curing agent (diphenylcarbamate), stir the mixture thoroughly with a magnetic stirrer, and let it stand for 30~40min;

[0099] (2) Weigh 1~2g of the mixture prepared in step (1) and drop it onto a glass slide to level it. Place it in a vacuum oven to cure for 40~60min. Peel it off from the glass slide to obtain a thin film of polydimethylsiloxane elastomer. Prepare another piece of polydimethylsiloxane elastomer using the same method.

[0100] Step 5, the fabrication of the flexible strain sensor, includes the following specific steps:

[0101] (1) Place the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared in step 3 on the polydimethylsiloxane elastomer film prepared in step 4, connect two copper electrodes to both sides of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel with conductive silver paste, and then wrap the above system with the polydimethylsiloxane elastomer film to obtain a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel.

[0102] Figure 1 The tensile stress-strain curves of carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogels were shown in the tensile test. As the amount of carboxymethyl cellulose added increased from 0 g to 0.125 g, the tensile strength of the hydrogel first increased and then decreased. When the amount of carboxymethyl cellulose added reached 0.1 g, the hydrogel exhibited the best mechanical strength, with an elongation at break of 331% and a tensile strength of 101.96 kPa. This indicates that a certain amount of carboxymethyl cellulose can act as a reinforcing phase, significantly improving the mechanical properties of the hydrogel. Figure 2 The values ​​represent the adhesion strength of the carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel to different substrates, indicating that the hydrogel has high adhesion strength to a variety of substrates and is suitable for application in wearable flexible electronic devices. Figure 3 It is a mixture of carboxymethyl cellulose, liquid metal, sodium lignosulfonate, and polyacrylic acid under simulated sunlight (100mW cm⁻¹). -2 The output voltage curve under irradiation shows that the continuous voltage output can remain stable under irradiation conditions of more than 10,000 seconds, indicating that the hydrogel has excellent photothermal-electric conversion capability and can stabilize the output voltage (3mV). Figure 4 The graph shows the change in current over time at different bending angles (30°, 60° and 90°) of the finger, which is monitored by a flexible strain sensor. This indicates that the sensor has good sensing sensitivity, stability and repeatability. Figure 5The flexible strain sensor monitors the writing of fingers. It can respond quickly to the complex and minute movements of the fingers when writing, demonstrating the repeatable and stable current response capability of the flexible strain sensor. Figure 6 The flexible strain sensor transmits Morse code through long and short presses, and it can also respond quickly to current signals, indicating that the flexible strain sensor can be applied in different sensing fields.

[0103] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. The above descriptions are merely preferred embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A method for fabricating a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel, characterized in that, Includes the following steps: Prepare a mixed aqueous solution A of carboxymethyl cellulose and sodium lignosulfonate; Liquid metal is added to a mixed aqueous solution A and ultrasonically treated to obtain solution B; Acrylic acid was added to solution B, and after stirring until homogeneous, a crosslinking agent and an initiator were added to obtain solution C. Solution C was introduced into a mold for in-situ polymerization to obtain hydrogel D; Preparation of polydimethylsiloxane elastomer films; Hydrogel D was placed on the prepared polydimethylsiloxane elastomer film, and copper electrodes were connected to both sides of hydrogel D by conductive silver paste. Then, the hydrogel D was wrapped with polydimethylsiloxane elastomer film to obtain a flexible strain sensor. The mass-to-volume ratio of carboxymethyl cellulose, sodium lignosulfonate, and water in the mixed aqueous solution A is 0.05~0.125:0.02:16 g / g / mL; The liquid metal is a gallium-indium alloy, in which the mass ratio of metallic gallium to metallic indium is 75.5:24.5, and the amount of gallium-indium alloy added is 0.3g. The amount of acrylic acid added is 4g, and the crosslinking agent and initiator are N'N-methylenebisacrylamide and ammonium persulfate, respectively.

2. The method for preparing a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel according to claim 1, characterized in that, The mass-to-volume ratio of carboxymethyl cellulose, sodium lignosulfonate, and water in the mixed aqueous solution A is 0.1:0.02:16 g / g / mL.

3. The method for preparing a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel according to claim 1, characterized in that, The ultrasonic treatment power is 450-500W, and the treatment time is 80-90min.

4. The method for preparing a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel according to claim 1, characterized in that, The method for preparing the polydimethylsiloxane elastomer film includes: Weigh out a polydimethylsiloxane solution, add a curing agent and stir thoroughly. Drop the mixture onto a glass slide and level it. After vacuum curing, peel it off from the glass slide to obtain a film.

5. The method for preparing a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel according to claim 4, characterized in that, The amount of polydimethylsiloxane solution added is 1g~2g, the amount of curing agent added is 0.1g~0.2g, and the vacuum curing time is 40~60min.

6. The method for preparing a flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel according to claim 4, characterized in that, The curing agent is diphenylcarbamate butyl ester.

7. The application of the flexible strain sensor based on carboxymethyl cellulose-liquid metal-sodium lignosulfonate-polyacrylic acid hydrogel prepared by the preparation method of any one of claims 1-6 in wearable flexible electronic devices.

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