Preparation of conductive hydrogel based on two liquid metals

Abstract

The invention discloses a preparation method of conductive hydrogel based on two liquid metals, which comprises the following steps: by taking 2-acryloyloxyethyl trimethyl ammonium chloride (AETAC) as a monomer, N, N '-methylenebisacrylamide (MBA) as a cross-linking agent and 2-hydroxy-2-methyl propiophenone (HMPP) as a photoinitiator, and combining with eutectic gallium indium (EGaIn) and eutectic gallium indium tin (EGaInSn) liquid metals, preparing the conductive hydrogel based on the two liquid metals. Two different conductive hydrogels are prepared through ultrasonic dispersion and ultraviolet-initiated polymerization. The method is simple in process, and the obtained hydrogel has high conductivity, good mechanical property and biocompatibility and can be widely applied to the fields of flexible electronics, biomedical sensing, wearable equipment and the like.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of polymer functional materials and relates to the preparation of a conductive hydrogel based on two kinds of liquid metals.

[0002] Background of Material Research

[0003] Wearable sensors play a key role in personalized healthcare, clinical diagnosis, and body detection. With the growing interest in flexible bioelectronics, flexible wearable sensors with inherent advantages such as portability, high flexibility, excellent compliance, and low cost show great potential in real-time and continuous monitoring of an individual's physiological and biological states. Currently, several conductive materials with excellent electrical and mechanical properties, such as carbon nanotubes, graphene, metal particles, and conductive polymers, have been successfully combined with elastic substrate composites to fabricate several representative flexible sensors. However, in practical applications, these devices often suffer from problems such as unsatisfactory sensitivity and poor biocompatibility.

[0004] Hydrogels are a type of elastic hydrated polymer that can accommodate a high content of water. The mechanical properties (toughness, stretchability, and fluidity) of hydrogels can be adjusted during the synthesis process, enabling the application of hydrogels to wearable sensors. Conductive hydrogels, as a promising type of hydrogel, can be formed by combining a hydrogel network with conductive fillers. Currently, various rigid conductive fillers (including carbon nanotubes, graphene, and metal nanowires) have been used for human activity monitoring, flexible touch displays, and human-machine interfaces. However, the rigid characteristics of the above-mentioned conductive fillers may cause mechanical friction with the hydrogel, resulting in internal stress concentration and damage. Liquid metal (LM) has been successfully applied to biomaterials, soft machinery, and flexible electronics due to its good electrical conductivity, high thermal conductivity, good flexibility, negligible toxicity, and extensibility. Therefore, introducing liquid metal into the hydrogel can effectively solve the problems existing in the above-mentioned conductive hydrogels. Summary of the Invention

[0005] The preparation of a conductive hydrogel based on two kinds of liquid metals, using 2-acryloyloxyethyl trimethylammonium chloride (AETAC) as a monomer, respectively combined with eutectic gallium indium (EGaIn) and eutectic gallium indium tin (EGaInSn) liquid metals, and prepared by photoinitiated polymerization to obtain a functional hydrogel material with high conductivity, good mechanical properties, and biocompatibility. Its conduction principle is that AETAC forms a polymer network as a monomer; the liquid metal fills the cross-linked structure of the polymer network and plays the role of electron transport.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] The first aspect of the present invention provides the preparation of a conductive hydrogel based on two liquid metals. The raw materials used include 2-acryloyloxyethyltrimethylammonium chloride, 2-hydroxy-2-methylpropiophenone, eutectic indium gallium, eutectic gallium indium tin, N,N'-methylenebisacrylamide, and sodium hydroxide.

[0008] The 2-acryloyloxyethyltrimethylammonium chloride provided by the present invention is used as a monomer, 2-hydroxy-2-methylpropiophenone is used as a photoinitiator, eutectic indium gallium and eutectic gallium indium tin are used as conductive fillers, and N,N'-methylenebisacrylamide is used as a crosslinking agent. Based on these raw materials, a conductive hydrogel based on liquid metal is invented.

[0009] The second aspect of the present invention provides a preparation method of a conductive hydrogel based on two liquid metals, including the following steps:

[0010] (1) Add 2-acryloyloxyethyltrimethylammonium chloride (AETAC) to deionized water and perform ultrasonic stirring treatment with water to prepare a mixed solution A with a mass fraction of 20%-40%.

[0011] (2) Then add N,N'-methylenebisacrylamide (MBA) to the mixed solution A, with an addition amount of 0.5%-2% of the mass of AETAC, and perform ultrasonic and stirring treatment to obtain a mixed solution B.

[0012] (3) Add 2-hydroxy-2-methylpropiophenone (HMPP) to the above mixed solution B, with an addition amount of 0.25%-1% of the mass of AETAC, and perform ultrasonic and stirring treatment to obtain a mixed solution C.

[0013] (4) First, add eutectic gallium indium (EGaIn) / eutectic gallium indium tin (EGaInSn) to a sodium hydroxide solution for treatment, and then disperse EGaIn / EGaInSn into micron- or nano-scale droplets through ultrasonic treatment.

[0014] (5) Add the EGaIn / EGaInSn droplets treated in (4) to solution C to obtain a mixed solution D. Under ice bath conditions, perform ultrasonic treatment on the mixed solution D to uniformly disperse EGaIn / EGaInSn and obtain a mixed solution E.

[0015] (6) Pass nitrogen into solution E to remove the dissolved oxygen in the system and obtain a mixed solution F.

[0016] (7) Inject the mixed solution F into a mold.

[0017] (8) Place the mold filled with the mixed solution F under ultraviolet light irradiation for photopolymerization reaction to obtain a hydrogel.

[0018] (9) Take out the obtained hydrogel from the mold and soak it in deionized water to remove the unreacted monomers and initiators, obtaining the final liquid metal-based conductive hydrogel.

[0019] Further, in the step (1), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of the stirring is 1000 rpm, and the stirring time is 30 minutes.

[0020] Further, in the step (2), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of the stirring is 1000 rpm, and the stirring time is 30 minutes.

[0021] Further, in the step (3), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of the stirring is 1000 rpm, and the stirring time is 30 minutes.

[0022] Further, in the step (4), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 1 hour.

[0023] Further, in the step (5), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 30 minutes.

[0024] Further, in the step (6), the time for introducing nitrogen is 10 - 15 minutes.

[0025] Further, in the step (8), the wavelength of the ultraviolet light irradiated is 365 nm, the power is 30 W / cm 2 , and the photopolymerization reaction time is 20 minutes.

[0026] Further, in the step (9), the soaking time in deionized water is 24 hours. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the hydrogel;

[0028] Figure 2 is the stress-strain curve of the EGaIn-based hydrogel;

[0029] Figure 3 is the stress-strain curve of the EGaInSn-based hydrogel;

[0030] Figure 4 is the physical diagram of the two hydrogels;

[0031] Figure 5 is the test diagram of the length and thickness of the two hydrogels; Detailed Embodiments

[0032] The embodiments of the present invention will be described in detail below. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0033] In the following embodiments, unless otherwise specified for raw materials or processing techniques, it means that they are all conventional commercially available raw materials or conventional processing techniques in the art.

[0034] The sources of each component raw material are shown in Table 1

[0035] Table 1

[0036]

[0037]

[0038] Example 1:

[0039] (1) Add 6 g of 2-acryloyloxyethyltrimethylammonium chloride (AETAC) to 14 mL of deionized water and perform ultrasonic stirring treatment with water to prepare a mixed solution A;

[0040] (2) Then add 0.09 g of N,N'-methylenebisacrylamide (MBA) to the mixed solution A and perform ultrasonic and stirring treatment to obtain a mixed solution B;

[0041] (3) Add 0.03 g of 2-hydroxy-2-methylpropiophenone (HMPP) to the above mixed solution B and perform ultrasonic and stirring treatment to obtain a mixed solution C;

[0042] (4) Weigh 2.5 g of eutectic gallium indium (EGaIn), add it to 1 mL of 0.1 mol sodium hydroxide solution for treatment, and then disperse the EGaIn into micron- or nanoscale droplets through ultrasonic treatment;

[0043] (5) Add the EGaIn droplets treated in (4) to the solution C to obtain a mixed solution D. Under ice bath conditions, perform ultrasonic treatment on the mixed solution D to uniformly disperse the EGaIn and obtain a mixed solution E;

[0044] (6) Pass nitrogen into the solution E to remove the dissolved oxygen in the system and obtain a mixed solution F;

[0045] (7) Inject the mixed solution F into a mold;

[0046] (8) Place the mold filled with the mixed solution F under ultraviolet light irradiation to carry out a photopolymerization reaction to obtain a hydrogel;

[0047] (9) Take out the obtained hydrogel from the mold and soak it in deionized water to remove unreacted monomers and initiators, obtaining the final liquid metal-based conductive hydrogel.

[0048] In Specific Example 1:

[0049] Furthermore, in step (1), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of stirring is 1000 rpm, and the stirring time is 30 minutes.

[0050] Furthermore, in step (2), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of stirring is 1000 rpm, and the stirring time is 30 minutes.

[0051] Furthermore, in step (3), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of stirring is 1000 rpm, and the stirring time is 30 minutes.

[0052] Furthermore, in step (4), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 1 hour.

[0053] Furthermore, in step (5), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 30 minutes.

[0054] Furthermore, in step (6), the time for introducing nitrogen is 10 minutes.

[0055] Furthermore, in step (7), the thickness of the mold is 3 mm.

[0056] Furthermore, in step (8), the wavelength of the ultraviolet light irradiated is 365 nm, the power is 30 W / cm 2 , and the photopolymerization reaction time is 20 minutes.

[0057] Furthermore, in step (9), the soaking time in deionized water is 24 hours.

[0058] The prepared hydrogel presents a uniform gray color, with a thickness of 3 mm and a length of 2 cm.

[0059] Example 2:

[0060] (1) Add 6 g of 2-acryloyloxyethyltrimethylammonium chloride (AETAC) to 14 mL of deionized water and perform ultrasonic stirring treatment with water to prepare a mixed solution A;

[0061] (2) Then add 0.09 g of N,N'-methylenebisacrylamide (MBA) to the mixed solution A and perform ultrasonic and stirring treatments to obtain a mixed solution B;

[0062] (3) Add 0.03 g of 2-hydroxy-2-methylpropiophenone (HMPP) to the above-mentioned mixed solution B, and perform ultrasonic and stirring treatments to obtain a mixed solution C;

[0063] (4) Weigh 2.5 g of eutectic gallium-indium-tin and add it to 1 mL of 0.1 mol sodium hydroxide solution for treatment, and then disperse the eutectic gallium-indium-tin into micron- or nanoscale droplets through ultrasonic treatment;

[0064] (5) Add the eutectic gallium-indium-tin droplets treated in (4) to solution C to obtain a mixed solution D. Under ice bath conditions, perform ultrasonic treatment on the mixed solution D to uniformly disperse the eutectic gallium-indium-tin to obtain a mixed solution E;

[0065] (6) Pass nitrogen into solution E to remove the dissolved oxygen in the system to obtain a mixed solution F;

[0066] (7) Inject the mixed solution F into a mold;

[0067] (8) Place the mold filled with the mixed solution F under ultraviolet light irradiation to carry out a photopolymerization reaction to obtain a hydrogel;

[0068] (9) Take out the obtained hydrogel from the mold and soak it in deionized water to remove the unreacted monomers and initiators to obtain the final liquid metal-based conductive hydrogel.

[0069] In specific embodiment 2:

[0070] Furthermore, in the step (1), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of the stirring is 1000 rpm, and the stirring time is 30 minutes.

[0071] Furthermore, in the step (2), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of the stirring is 1000 rpm, and the stirring time is 30 minutes.

[0072] Furthermore, in the step (3), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of the stirring is 1000 rpm, and the stirring time is 30 minutes.

[0073] Furthermore, in the step (4), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 1 hour.

[0074] Furthermore, in the step (5), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 30 minutes.

[0075] Furthermore, in the step (6), the time for passing nitrogen is 15 minutes.

[0076] Further, in the step (7), the thickness of the mold is 3 mm.

[0077] Further, in the step (8), the wavelength of the irradiated ultraviolet light is 365 nm, the power is 30 W / cm 2 , and the photopolymerization reaction time is 20 minutes.

[0078] Further, in the step (9), the soaking time in deionized water is 24 hours.

[0079] The prepared hydrogel presents a uniform milky white color, with a thickness of 3 mm and a length of 2 cm.

[0080] Experimental Example 1: Use a universal material testing machine to test the stress-strain curve of the hydrogel. The test results of the two hydrogels are respectively as Figure 2 and Figure 3 shown.

[0081] Experimental Example 2: Use a DDG-8508S conductivity tester to test the conductivity of the two hydrogels by the four-electrode method. During the test, insert wires at both ends of the hydrogel as electrodes and encapsulate them with VHB tape to ensure a tight bond between the electrodes and the hydrogel. Use a KCl standard solution (0.1 mol / L, 25 °C) as the calibration solution. The measured conductivity of the conductive hydrogel based on EGaIn liquid metal in Example 1 is 2.8 S / cm, and the conductivity of the conductive hydrogel based on EGaInSn liquid metal in Example 2 is 3.3 S / cm.

[0082] Experimental Example 3: Use a digital display push-pull force gauge to conduct a tensile test on the hydrogel. Hook one end of the hydrogel to one end of the digital display push-pull force gauge and fix the other end. Then, pull the digital display push-pull force gauge uniformly to stretch the hydrogel until it breaks, and record the tensile length at this time. The measured tensile length of the conductive hydrogel based on EGaIn liquid metal in Example 1 is 30 cm, and the tensile length of the conductive hydrogel based on EGaInSn liquid metal in Example 2 is 27 cm.

[0083] The performance comparison chart of the two hydrogels is shown in Table 2

[0084] Table 2

[0085] Hydrogels with different conductive media EGaIn EGaInSn Conductivity S / cm 2.8 3.3 Tensile length cm 30 27

[0086] The conductive hydrogels based on two liquid metals provided by the present invention have the following beneficial effects:

[0087] 1. High electrical conductivity: Using liquid metals (EGaIn or EGaInSn) as conductive fillers enables the hydrogel to have excellent electrical conductivity, with conductivities of 2.8 and 3.3 S / cm respectively, far higher than traditional conductive hydrogels;

[0088] 2. Excellent mechanical properties: The hydrogel network formed by AETAC as the main monomer has good mechanical strength and elasticity. Combining with the fluidity characteristics of liquid metals, the conductive hydrogel has good tensile properties and self-healing properties;

[0089] 3. Simple and controllable process: Using the method of ultrasonic emulsification combined with photopolymerization, the operation is simple, the reaction conditions are mild, and the preparation process is controllable;

[0090] 4. Good structural stability: By optimizing the preparation process and component ratio, the uniform dispersion and stable existence of liquid metals in the hydrogel network are achieved, avoiding the aggregation and leakage of liquid metals.

[0091] The above-described embodiments are for the convenience of those of ordinary skill in the art to understand and use the invention, and do not impose any form of limitation on this application. Any person skilled in the art, without departing from the scope of the technical solution of this application, any changes or modifications made using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. Preparation method of conductive hydrogel based on two kinds of liquid metals, characterized in that, It includes the following steps: (1) Add 2-acryloyloxyethyltrimethylammonium chloride (AETAC) to deionized water and perform ultrasonic stirring treatment with water to prepare a mixed solution A with a mass fraction of 20%-40%; (2) Then add N,N'-methylenebisacrylamide (MBA) to the mixed solution A, and the addition amount is 0.5%-2% of the mass of AETAC, and perform ultrasonic and stirring treatment to obtain a mixed solution B; (3) Add 2-hydroxy-2-methylpropiophenone (HMPP) to the above mixed solution B, and the addition amount is 0.25%-1% of the mass of AETAC, and perform ultrasonic and stirring treatment to obtain a mixed solution C; (4) First, add eutectic gallium indium (EGaIn) / eutectic gallium indium tin (EGaInSn) to a sodium hydroxide solution for treatment, and then disperse EGaIn / EGaInSn into micron- or nano-scale droplets through ultrasonic treatment; (5) Add the EGaIn / EGaInSn droplets treated in (4) to solution C to obtain a mixed solution D. Under ice bath conditions, perform ultrasonic treatment on the mixed solution D to uniformly disperse EGaIn / EGaInSn to obtain a mixed solution E; (6) Pass nitrogen into solution E to remove the dissolved oxygen in the system to obtain a mixed solution F; (7) Inject the mixed solution F into a mold; (8) Place the mold filled with the mixed solution F under ultraviolet light irradiation for photopolymerization reaction to obtain a hydrogel; (9) Take out the obtained hydrogel from the mold and soak it in deionized water to remove unreacted monomers and initiators to obtain the final liquid metal-based conductive hydrogel.

2. According to claim 1, in step (1), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of stirring is 1000 rpm, and the stirring time is 30 minutes.

3. According to claim 1, in step (2), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of stirring is 1000 rpm, and the stirring time is 30 minutes.

4. According to claim 1, in step (3), the power of the ultrasonic wave is set to 1000 W, the ultrasonic time is 30 minutes, the rotation speed of stirring is 1000 rpm, and the stirring time is 30 minutes.

5. According to claim 1, in step (4), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 1 hour.

6. According to claim 1, in step (5), the power of the ultrasonic wave is set to 1000 W, and the ultrasonic time is 30 minutes.

7. According to claim 1, in step (6), the time for passing nitrogen is 10-15 minutes.

8. According to claim 1, in step (viii), the wavelength of the ultraviolet light irradiated is 365 nm, the power is 30 W / cm 2 , and the photopolymerization reaction time is 20 minutes.

9. According to claim 1, in step (9), the soaking time in deionized water is 24 hours.

10. The conductive hydrogel based on two kinds of liquid metals is prepared by the method described in claims 1-9, and is characterized in that: Both of these two hydrogels are prepared into rod shapes with slightly wider ends and a narrower middle. Stretch test these two hydrogels using a tensile tester, and test the conductivity of these two hydrogels using a four-point probe tester.

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