Preparation method of a novel dual-network self-healing hydrogel sensor

Abstract

The invention discloses a method for preparing a novel double-network self-healing hydrogel sensor. The first network of the double-network hydrogel is copolymerized by a free radical initiator using acrylic acid and vinyl ionic liquid as monomers. Meanwhile, carboxymethyl guar gum is used as the second network of the hydrogel. In addition, the introduction of aluminum chloride improves the mechanical strength and conductive sensing performance of the hydrogel, and the self-healing performance of the hydrogel is enhanced because the trivalent aluminum ions can form metal dynamic coordination bonds with the carboxyl groups on the double network. The hydrogel has good mechanical properties, can heal itself after being damaged by the outside world, and has excellent sensing performance and high strain sensitivity, and can be applied to strain sensing related fields.

Description

Technical Field

[0001] The invention relates to the field of functional biopolymer materials, in particular to a method for preparing a novel double-network self-healing hydrogel sensor. Background Art

[0002] With the rapid development of high-performance smart materials, smart homes and the Internet of Things, sensor technology has gradually entered people's lives, setting off a wave of research on sensors. Strain sensors can convert deformation caused by external forces into recordable electrical signals, such as capacitance, current and resistance, and play an irreplaceable and important role in soft robots, artificial intelligence, human motion and health monitoring, etc.

[0003] Currently, the strain sensors that are widely used include flexible thin metal substrates with integrated conductive materials, liquid metal sensors, and conductive elastomers, but their poor stretchability limits their application in detecting human movement. In contrast, hydrogels with adjustable stretchability have greater application potential. As we all know, sensors will inevitably be damaged to a certain extent in practical applications, and their in-situ repair is very challenging and practical. Smart sensors with self-healing properties have become a current research hotspot. Therefore, preparing flexible hydrogel sensors with self-healing properties is an effective strategy to achieve in-situ repair of strain sensors and extend their service life.

[0004] The hydrogels with excellent mechanical properties currently developed include composite hydrogels, topological hydrogels, double network structure hydrogels, hydrophobic association hydrogels, etc. Among them, the double network structure hydrogel is a promising hydrogel material in the field of self-healing flexible sensors. The reason is that the double network structure, on the one hand, provides a matrix with adjustable mechanical properties for the hydrogel, and on the other hand, enables the hydrogel to have good energy dissipation capabilities.

[0005] Composite hydrogels prepared from polyacrylic acid have been widely used. In order to improve the mechanical properties and self-healing properties of polyacrylic acid hydrogels and expand their application range, polyacrylic acid is often compounded with other materials to prepare new hydrogels. Carboxymethyl guar gum is a modified natural biomacromolecule. Introducing it into hydrogels can not only be used as a second network, but also facilitate the formation of non-covalent bonds and improve energy dissipation, thereby improving the ability of self-healing hydrogels to resist deformation or damage. Summary of the invention

[0006] Purpose of the invention: In view of the above situation, the present invention provides a method for preparing a dual-network self-healing hydrogel sensor to solve the problems of traditional sensors such as lack of flexibility, inability to heal in situ, and short service life. In addition, this hydrogel strain sensor can monitor the movement of the human body in real time.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0008] 1) Add a certain volume of acrylic acid into deionized water and mix well, then add a certain amount of carboxymethyl guar gum and stir thoroughly;

[0009] 2) adding a certain amount of vinyl ionic liquid, aluminum chloride, N′N-methylene-bis-acrylamide and an alkaline solution of a certain concentration and volume to the above solution in sequence and stirring for a certain time;

[0010] 3) In an ice water bath environment, a free radical initiator of a certain concentration and volume is added to the above solution, and after stirring evenly, the mixed solution is poured into a polytetrafluoroethylene mold, and allowed to react at a certain temperature for a certain time to obtain a double network self-healing hydrogel.

[0011] In the step 1), the volume of acrylic acid is 2.5-3.5 ml, the amount of deionized water is 3.5-4.5 ml, and the amount of carboxymethyl guar gum is 0.15-0.25 g.

[0012] In the step 2), the amount of vinyl ionic liquid is 0.8-1.5 g, the amount of aluminum chloride is 0.15-0.25 g, the amount of N'N-methylene-bis-acrylamide is 0.003-0.007 g, the concentration of the alkaline solution is 2.3-2.7 mg / ml, and the volume is 1.8-2.2 ml.

[0013] In the step 3), the concentration of the free radical initiator is 5-15 mg / ml, the volume is 0.8-1.2 ml, the reaction temperature is 50-60 degrees Celsius, and the reaction time is 5-7 hours.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0015] 1) The novel double-network self-healing hydrogel sensor prepared by the present invention has good flexibility;

[0016] 2) The novel dual-network self-healing hydrogel sensor prepared by the present invention has excellent self-healing performance, that is, after being cut into two sections, it can be self-healed in situ to form a whole;

[0017] 3) The novel dual-network self-healing hydrogel sensor prepared by the present invention can identify human joint movements when used as a strain sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The novel dual-network self-healing hydrogel sensor prepared in Example 1 of the present invention can be stretched into a thin film and an elongated image.

[0019] Figure 2This is a picture of the in-situ self-healing of the novel dual-network self-healing hydrogel sensor prepared in Example 1 of the present invention after being cut into two pieces.

[0020] Figure 3 This is a time-resistance change rate diagram of the novel dual-network self-healing hydrogel sensor prepared in Example 1 of the present invention when used as a tensile strain sensor. DETAILED DESCRIPTION

[0021] Example 1

[0022] 1) 3 ml of acrylic acid and 4 ml of deionized water were mixed evenly, and then 0.2 g of carboxymethyl guar gum with a viscosity of 3600 mPa·s and a degree of substitution of 0.68 was added and stirred thoroughly.

[0023] 2) 1 g of 1-vinyl-3-butylimidazolium bromide, 0.2 g of aluminum chloride, 0.004 g of N′N-methylene-bis-acrylamide, and 2 ml of 2.5 mg / ml potassium hydroxide solution were added to the above solution in sequence and stirred for 12 hours.

[0024] 3) In an ice water bath, 1 ml of 10 mg / ml ammonium persulfate was added to the above solution, stirred evenly, and then the solution was poured into a polytetrafluoroethylene mold and allowed to react at 50 degrees Celsius for 5.5 hours to obtain a double network self-healing hydrogel sensor.

[0025] The performance test of the novel dual-network self-healing hydrogel sensor prepared in Example 1 was carried out as follows:

[0026] 1) Small hydrogel sensors can be easily stretched into thin films and elongated, such as Figure 1 As shown, it proves that the hydrogel has good flexibility.

[0027] 2) After the hydrogel sensor is cut into two pieces, it can self-heal into a whole in situ, e.g. Figure 2 As shown, it proves that the hydrogel has good self-healing properties.

[0028] 3) Connect the hydrogel sensor to the circuit through the LCR bridge electrode clip. The hydrogel sensor can be used as a sensor to sense the frowning and finger bending movements of a person, such as Figure 3 As shown, it is demonstrated that the hydrogel sensor can accurately monitor tiny movements of the human body.

[0029] Example 2

[0030] 1) 2.5 ml of acrylic acid and 4.5 ml of deionized water were mixed evenly, and then 0.15 g of carboxymethyl guar gum with a viscosity of 3000 mPa·s and a degree of substitution of 0.6 was added and stirred thoroughly.

[0031] 2) 0.8 g of 1-allyl-3-vinylimidazolium bromide, 0.25 g of aluminum chloride, 0.003 g of N′N-methylene-bis-acrylamide and 1.8 ml of 2.3 mg / ml sodium hydroxide solution were added to the above solution in sequence and stirred for 13 hours.

[0032] 3) In an ice water bath, 0.8 ml of 15 mg / ml potassium persulfate was added to the above solution, and after stirring evenly, the solution was poured into a polytetrafluoroethylene mold and allowed to react at 50 degrees Celsius for 6.5 hours to obtain a double-network self-healing hydrogel sensor.

[0033] Example 3

[0034] 1) 2.7 ml of acrylic acid and 4.3 ml of deionized water were mixed evenly, and then 0.18 g of carboxymethyl guar gum with a viscosity of 3400 mPa·s and a degree of substitution of 0.5 was added and stirred thoroughly.

[0035] 2) 1.2 g of 1-vinyl-3-octylimidazolium bromide, 0.18 g of aluminum chloride, 0.007 g of N′N-methylene-bis-acrylamide, and 2.1 ml of 2.4 mg / ml calcium hydroxide solution were added to the above solution in sequence and stirred for 14 hours.

[0036] 3) In an ice water bath, 0.9 ml of 13 mg / ml sodium persulfate was added to the above solution, and after stirring evenly, the solution was poured into a polytetrafluoroethylene mold and allowed to react at 60 degrees Celsius for 6 hours to obtain a double-network self-healing hydrogel sensor.

[0037] Example 4

[0038] 1) 3.5 ml of acrylic acid and 3.5 ml of deionized water were mixed evenly, and then 0.23 g of carboxymethyl guar gum with a viscosity of 4000 mPa·s and a degree of substitution of 0.65 was added and stirred thoroughly.

[0039] 2) 1.5 g of 1-vinyl-3-butylimidazolium bromide, 0.22 g of aluminum chloride, 0.006 g of N′N-methylene-bis-acrylamide, and 1.9 ml of 2.6 mg / ml potassium hydroxide solution were added to the above solution in sequence and stirred for 15 hours.

[0040] 3) In an ice water bath, 1.1 ml of 15 mg / ml potassium persulfate was added to the above solution, stirred evenly, and then the solution was poured into a polyacrylic acid mold and allowed to react at 57 degrees Celsius for 5 hours to obtain a double network self-healing hydrogel sensor.

[0041] The above embodiments are only some specific examples of implementing the invention, and the description is only for the purpose of illustration rather than limiting the scope of the invention.

Claims

1. A method for preparing a double network self-healing hydrogel, characterized in that: The hydrogel has a dual network structure, in which the first network is formed by copolymerization of acrylic acid and vinyl ionic liquid through free radical initiation, and the second network is carboxymethyl guar gum. The introduction of aluminum chloride enhances the mechanical properties, sensing properties and self-healing properties of the gel, which specifically includes the following steps: 1) Add a certain volume of acrylic acid into deionized water and mix well, then add a certain amount of carboxymethyl guar gum and stir thoroughly; 2) adding a certain amount of vinyl ionic liquid, aluminum chloride, N'N-methylene-bis-acrylamide and a certain concentration and volume of alkaline solution to the above solution in sequence and stirring for a certain time, wherein the vinyl ionic liquid is one of 1-vinyl-3-butyl imidazolium bromide, 1-vinyl-3-ethyl imidazolium bromide, 1-allyl-3-vinyl imidazolium bromide and 1-vinyl-3-octylimidazolium bromide, and the alkaline solution is one of potassium hydroxide, sodium hydroxide and calcium hydroxide solution; 3) In an ice water bath environment, a free radical initiator of a certain concentration and volume is added to the above solution, and after stirring evenly, the mixed solution is poured into a polytetrafluoroethylene mold, and allowed to react at a certain temperature for a certain time to obtain a double network self-healing hydrogel, wherein the free radical initiator is one of ammonium persulfate, potassium persulfate, and sodium persulfate.

2. The preparation method according to claim 1, characterized in that: In the step 1), the volume of acrylic acid is 2.5-3.5 ml, the amount of deionized water is 3.5-4.5 ml, and the amount of carboxymethyl guar gum is 0.15-0.25 g.

3. The preparation method according to claim 1, characterized in that: In the step 2), the amount of vinyl ionic liquid used is 0.8-1.5 g, the amount of aluminum chloride used is 0.15-0.25 g, the amount of N'N-methylene-bis-acrylamide used is 0.003-0.007 g, the concentration of the alkaline solution is 2.3-2.7 mg / ml, and the volume is 1.8-2.2 ml.

4. The preparation method according to claim 1, characterized in that: In the step 3), the concentration of the free radical initiator solution is 5-15 mg / ml, the volume is 0.8-1.2 ml, the reaction temperature is 50-60 degrees Celsius, and the reaction time is 5-7 hours.

5. The double-network self-healing hydrogel obtained by the preparation method according to claim 1.

6. Application of the double network self-healing hydrogel according to claim 5 in the field of flexible strain sensors.

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