Carboxymethyl cellulose conductive hydrogel flexible strain sensor and preparation method thereof

Abstract

The invention relates to a carboxymethyl cellulose conductive hydrogel flexible strain sensor and a preparation method thereof. The conductive hydrogel is prepared from the following raw materials: acrylic acid, 1-vinyl imidazole, carboxymethyl cellulose and MXene. The conductivity of the hydrogel can reach 1.1 S / m by adjusting the proportion range of the monomer and the carboxymethyl cellulose and the content range of the MXene nanosheet. The conductive hydrogel has high mechanical strength and good conductivity and antibacterial property, and the preparation method is simple and reliable. The strain sensor formed by the hydrogel can realize quick response to human body movement, and can be applied to the field of wearable electronic equipment.

Description

Technical Field

[0001] The present invention relates to the construction of an acrylic / carboxymethyl cellulose / 1-vinylimidazole / MXene hydrogel, which is intended to be used as a new type of human strain detection sensor in applications. Background Art

[0002] Flexible electronic devices refer to electronic devices that can still work under certain deformations (such as stretching, folding, compressing, or twisting). The substrates of existing flexible electronic devices use various synthetic polymers, which have a large Young's modulus or lack sufficient biocompatibility. In order to meet the development needs of flexible electronic devices, it is necessary to find substrate materials that match biological tissues and have good mechanical properties.

[0003] Hydrogels can feedback the strain applied by the outside world through the changes in their complex three-dimensional network structure. At the same time, they have good recovery performance when compressed and stretched, and can be used to manufacture various electronic devices and strain sensors.

[0004] However, most of the current hydrogel-based flexible strain sensors have low sensitivity, low mechanical properties, and poor conductivity, seriously affecting the comprehensive detection and analysis of flexible strain sensors for complex physiological signals and physical movements of the human body.

[0005] Chinese Patent (CN113943427A) describes a hydrogel strain sensor. The hydrogel uses polyvinyl alcohol and borax as the hydrogel skeleton, water as the solvent, carbon nanotubes modified with silver nanoparticles as the conductive substance, and glycerol as the substance incorporated into the system to improve the anti-water loss performance of the hydrogel. The prepared hydrogel has the advantages of elasticity, conductivity, low-temperature resistance, and anti-water loss. The maximum fracture strain is 270%, and the fracture stress is 240 kPa.

[0006] Chinese Patent (CN116355242A) describes a hydrogel strain sensor. The hydrogel uses natural polymer materials and polymer polymers as the hydrogel matrix, and introduces carboxymethyl cellulose-conductive polymer composites and alkali lignin-metal salts. The prepared hydrogel has good self-adhesion, conductivity, and self-healing properties. The maximum fracture strain is 950%, and the fracture stress is 30 kPa. Summary of the Invention

[0007] In order to overcome the deficiencies in the prior art, the technical problems to be solved by the present invention are to provide a hydrogel that can be used in flexible strain sensors, which has high mechanical strength, antibacterial ability, and high conductivity, and can also adjust characteristics such as conductivity by changing the degree of tensile deformation. Another technical problem to be solved by the present invention is to provide a preparation method for the above-mentioned hydrogel that can be used in flexible strain sensors.

[0008] 1. To solve the above technical problems, the technical solution adopted by the present invention is: a hydrogel that can be used for flexible strain sensors, and the raw materials for preparation include acrylic acid, 1-vinylimidazole, carboxymethyl cellulose, and MXene.

[0009] 2. It is characterized in that the specific steps are as follows:

[0010] (1) Freeze-drying: The MXene dispersion is vacuum freeze-dried to obtain MXene nanosheets. Preferably, the drying time is 48 h.

[0011] (2) Ultrasonic dispersion: Use an ultrasonic machine to disperse the MXene nanosheets into deionized aqueous solution. Preferably, in step (2), 3 ml of deionized water is used, and the mass of MXene is 0.5-2% of the total mass of the monomers. Further preferably, in step (2), the content of MXene is 1% of the total mass of the monomers.

[0012] (3) Dissolution: Add a certain amount of carboxymethyl cellulose (CMC) to the dispersed solution, and stir the carboxymethyl cellulose (CMC) until it dissolves at room temperature. Preferably, in step (3)

[0013] the mass of carboxymethyl cellulose is 100 mg.

[0014] (4) Preparation: Add a certain amount of acrylic acid, 1-vinylimidazole, ammonium persulfate, tetramethylethylenediamine, and N,N′-methylenebisacrylamide to the above solution and stir evenly. Preferably, in step (4), 1.6 ml of acrylic acid, 400 mg of 1-vinylimidazole, 16 mg of ammonium persulfate, 10 μl of tetramethylethylenediamine, and 10 mg of N,N′-methylenebisacrylamide are used.

[0015] (5) Polymerization: Pour the above solution into a mold, ultrasonically remove all bubbles, and heat in a constant temperature oven. After polymerization, the gel is demolded and washed to remove unreacted substances. Preferably, the mold material in step (5) is polytetrafluoroethylene, and the free radical copolymerization reaction temperature set in the constant temperature oven is 60 °C, and the reaction time is 1.5 h. Description of the Drawings

[0016] Figure 1 is the scanning electron micrograph of the target product prepared in Example 3

[0017] Figure 2 is the stress-strain curve of the target products prepared in Examples 1-4

[0018] Figure 3 is the bar graph of the conductivity of the target products prepared in Examples 1-4

[0019] Figure 4Antibacterial properties of the target products prepared in Examples 1 and 3

[0020] Figure 5 Sensitivity factor curves of the target product prepared in Example 3 under different strains

[0021] Figure 6 Strain sensors composed of the target product prepared in Example 3 for monitoring human motion and physiological activities Detailed implementation manners

[0022] The above content of the present invention will be further described in detail below through examples. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention.

[0023] Example 1

[0024] 1. Add 0.1 g of carboxymethyl cellulose (CMC) to 3 ml of deionized water, and stir the carboxymethyl cellulose (CMC) until dissolved at room temperature.

[0025] 2. Then add 1.6 ml of acrylic acid (AA), 400 mg of 1-vinylimidazole (1-VI), 16 mg of ammonium persulfate (APS), 10 μl of N,N,N',N'-tetramethylethylenediamine (TEMED), and 10 mg of N,N'-methylenebisacrylamide (MBA) and mix well.

[0026] 3. Pour the above solution into a mold, ultrasonically remove all air bubbles, and heat in a constant temperature oven at 60 °C for 1.5 h

[0027] After demolding, wash with deionized water 3 times to remove unreacted substances to obtain a conductive hydrogel.

[0028] Example 2

[0029] 1. Disperse 10.9 mg of MXene nanosheets into 3 ml of deionized aqueous solution, and use an ultrasonic machine to disperse evenly.

[0030] 2. Add 0.1 g of carboxymethyl cellulose (CMC) to the dispersed solution, and stir the carboxymethyl cellulose (CMC) until dissolved at room temperature.

[0031] 3. Then add 1.6 ml of acrylic acid (AA), 400 mg of 1-vinylimidazole (1-VI), 16 mg of ammonium persulfate (APS), 10 μl of N,N,N',N'-tetramethylethylenediamine (TEMED), and 10 mg of N,N'-methylenebisacrylamide (MBA) and mix well.

[0032] 4. Pour the above solution into a mold, ultrasonically remove all air bubbles, and heat in a constant temperature oven at 60 °C for 1.5 h

[0033] After demolding, wash it 3 times with deionized water to remove unreacted substances, and obtain a conductive hydrogel.

[0034] Example 3

[0035] 1. Ultrasonic dispersion: Disperse 21.8 mg of MXene nanosheets into 3 ml of deionized water solution, and use an ultrasonic machine to disperse them evenly.

[0036] 2. Add 0.1 g of carboxymethyl cellulose (CMC) to the dispersed solution, and stir the carboxymethyl cellulose (CMC) until it dissolves at room temperature.

[0037] 3. Then add 1.6 ml of acrylic acid (AA), 400 mg of 1-vinylimidazole (1-VI), 16 mg of ammonium persulfate (APS), 10 μl of N,N,N',N'-tetramethylethylenediamine (TEMED), and 10 mg of N,N'-methylenebisacrylamide (MBA) respectively, and mix well.

[0038] 4. Pour the above solution into a mold, ultrasonically remove all air bubbles, heat it in a constant temperature oven at 60 °C for 1.5 h, then demold, wash it 3 times with deionized water to remove unreacted substances, and obtain a conductive hydrogel. Stick the hydrogel on the measured parts of the body with anti-allergy tape, such as fingers, wrists, elbows and knees. Connect the conductive hydrogel to a digital multimeter. Along with joint movement, the conductive hydrogel is stretched, and the resistance change generated by the hydrogel during the process can be used as sensor data.

[0039] Example 4

[0040] 1. Disperse 43.6 mg of MXene nanosheets into 3 ml of deionized water solution, and use an ultrasonic machine to disperse them evenly.

[0041] 2. Add 0.1 g of carboxymethyl cellulose (CMC) to the dispersed solution, and stir the carboxymethyl cellulose (CMC) until it dissolves at room temperature.

[0042] 3. Then add 1.6 ml of acrylic acid (AA), 400 mg of 1-vinylimidazole (1-VI), 16 mg of ammonium persulfate (APS), 10 μl of N,N,N',N'-tetramethylethylenediamine (TEMED), and 10 mg of N,N'-methylenebisacrylamide (MBA) respectively, and mix well.

[0043] 5. Pour the above solution into a mold, ultrasonically remove all air bubbles, and heat it in a constant temperature oven at 60 °C for 1.5 h

[0044] After demolding, wash it 3 times with deionized water to remove unreacted substances, and obtain a conductive hydrogel.

[0045] Performance test:

[0046] The target product was made into cylindrical specimens with a diameter of 4 mm and a height of 20 mm, and a universal testing machine with a 500 N sensor was used to test the stress-strain of the target product. As Figure 2 shown, the tensile stresses of the target products obtained in Examples 1-4 were 270 kPa, 384 kPa, 453 kPa, and 296 kPa respectively. The target product was made into button-shaped with a diameter of 13 mm and a thickness of 3 mm, clamped between two copper sheets, and its electrochemical impedance was tested using an electrochemical workstation. During the test, the voltage was set to 0.1 V and the frequency was 0.1 - 105 Hz. As Figure 3 shown, the conductivities of the target products obtained in Examples 1-4 were 0.26 S / m, 0.94 S / m, 1.1 S / m, and 2.5 S / m respectively. As Figure 4 shown, taking Escherichia coli (E.coil) as an example, the antibacterial properties of Examples 1 and 3 were evaluated. Figure 5 For the detection signal of the vibrating human movement by the strain sensor composed of the target product in Example 3, it can be seen from the figure that the strain sensor is sensitive to deformation and can detect subtle human movement signals, and thus can be applied to the field of strain sensors.

Claims

1. A carboxymethyl cellulose conductive hydrogel flexible strain sensor, characterized in that, The raw materials for preparing the conductive hydrogel flexible strain sensor include acrylic acid, 1-vinylimidazole, carboxymethyl cellulose, and MXene.

2. The preparation method of the carboxymethyl cellulose-based conductive hydrogel according to claim 1, characterized in that, At room temperature, weigh MXene, carboxymethyl cellulose, acrylic acid, and 1-vinylimidazole to prepare a mixed solution, and stir magnetically to dissolve to form a solution; after stirring and dissolving, continue to add an initiator, a co-initiator, and a cross-linking agent; pour it into a mold, ultrasonically remove all bubbles, and heat in a constant temperature oven; demold the polymerized gel and wash to remove unreacted substances.

3. According to claim 2, the deionized water required for preparing the solution is 3-4 ml, the mass range of carboxymethyl cellulose is 80-120 mg, the volume range of acrylic acid is 1.4-1.8 ml, the mass range of 1-vinylimidazole is 250-450 mg, and the mass range of MXene is 0.5-2% of the total mass of the monomers.

4. According to claim 2, the initiator is ammonium persulfate (APS), the co-initiator is tetramethylethylenediamine (TEMED), and the cross-linking agent is N,N′-methylenebisacrylamide (MBA).

5. According to claim 2, the mass range of ammonium persulfate is 12-20 mg, the volume range of tetramethylethylenediamine is 10-15 μL, and the mass range of N,N′-methylenebisacrylamide is 8-12 mg.

6. According to claim 2, the ultrasonic time is 5-10 min; the oven heating time is 60-90 min, the heating temperature is 60-70 °C, the washing material is deionized water, and the washing times are 2-3 times.

7. The conductive hydrogel strain sensor according to claim 1, wherein Stick the hydrogel on the body parts to be measured with anti-allergy tape, such as the fingers, wrists, elbows, and knees. Connect both ends of the conductive hydrogel with a digital multimeter. As the joint moves, the conductive hydrogel is stretched, and the resistance change generated by the hydrogel during the process can be used as sensor data.

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