Hydrogel flexible electrode based on MXene and preparation method and application thereof

Abstract

The invention relates to a hydrogel flexible electrode based on MXene and a preparation method and application thereof, and belongs to the technical field of conductive hydrogel. According to the hydrogel, acrylamide and a Ti3C2Tx solution cooperate to construct a framework of a dual-network structure, and excellent mechanical strength and conductivity are provided for the hydrogel. Due to the introduction of the liquid metal gallium-indium alloy, the conductivity is remarkably improved, meanwhile, the impedance of the material is reduced, chitosan serves as a dispersion stabilizer in a system, and uniform dispersion of MXene is ensured; acrylic acid further optimizes the crosslinking density by adjusting the pH value in the system, and the comprehensive performance of the hydrogel is improved. The use of the liquid metal gallium indium alloy not only enhances the conductivity, but also brings excellent interface contact performance to the hydrogel, so that the hydrogel has wider application potential in the fields of flexible electronics and sensing.

Description

Technical Field

[0001] The present invention relates to a MXene-based hydrogel flexible electrode and its preparation method and application, belonging to the technical field of conductive hydrogels. Background Art

[0002] With the continuous development of technology, intelligent flexible wearable sensors have shown extremely important application values in many fields, such as in wearable devices, rehabilitation medicine, sports training, and human-computer interaction. By accurately monitoring various motion postures, motion amplitudes, and motion trajectories of the human body, etc., it can provide users with personalized health assessments, sports guidance, and achieve more convenient and intelligent interaction operations.

[0003] In recent years, the motion monitoring of hydrogel-based wearable sensors has gradually emerged. With the advantages of being able to fit well with human skin and deform naturally with the human body, it can more directly and continuously collect various physiological signals and mechanical change information during human movement, providing a very potential solution for people's motion sensing and monitoring needs.

[0004] However, the existing hydrogel sensors still face many challenges in practical applications. On the one hand, the conventional hydrogel preparation process often involves complex and time-consuming cross-linking reactions, which not only makes the preparation efficiency low and difficult to meet the needs of large-scale production and rapid application, but also the cross-linking process has relatively strict requirements for reaction conditions, such as specific temperature, acidity and alkalinity, and a long reaction time, etc., restricting its use in some portable and instant application scenarios. On the other hand, some hydrogel sensors still need to be further improved in terms of sensitivity and use stability, and cannot accurately capture the subtle mechanical changes during human movement, thus affecting the accuracy and comprehensiveness of motion monitoring. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: overcoming the deficiencies of the prior art, and proposing a MXene-based hydrogel flexible electrode and its preparation method and application. This electrode is a hydrogel electrode with high sensitivity and rapid gelation, adopting acrylamide and MXene to form a double-network structure, and having the advantages of high sensitivity, fast gelation speed, excellent conductivity, good use stability, simple structure, and good biocompatibility. It can be used in wearable devices to identify human motion signals by attaching to the skin. Compared with traditional motion monitoring electrodes, the electrode of the present invention is more convenient to apply, more durable in use, has higher sensitivity, lower impedance, and low cost and simple operation.

[0006] The technical solution of the present invention is:

[0007] An MXene-based hydrogel, the raw materials of the hydrogel including acrylamide, acrylic acid, liquid metal gallium-indium alloy, chitosan, deionized water, Ti3C2T x dispersion and initiator;

[0008] This hydrogel constructs a framework with a double-network structure through the synergy of acrylamide and Ti3C2T x dispersion, providing the hydrogel with excellent mechanical strength and electrical conductivity;

[0009] The introduction of the liquid metal gallium-indium alloy significantly improves the electrical conductivity and reduces the material impedance at the same time; the use of the liquid metal gallium-indium alloy not only enhances the electrical conductivity, but also brings excellent interfacial contact performance to the hydrogel, making it have more extensive application potential in the fields of flexible electronics and sensing;

[0010] Chitosan acts as a dispersion stabilizer in the system to ensure the uniform dispersion of MXene;

[0011] Acrylic acid further optimizes the crosslinking density and improves the comprehensive performance of the hydrogel by adjusting the pH value in the system;

[0012] Calculated based on the total mass of the raw materials being 100%, the mass percentage content of each component is:

[0013] Acrylamide 39%-42%

[0014] Acrylic acid 9%-10%

[0015] Liquid metal gallium-indium alloy 25%-31%

[0016] Chitosan 1%-2%

[0017] Ti3C2T x dispersion 18%-20%

[0018] Initiator 1%-2%

[0019] The balance is deionized water

[0020] A preparation method of an MXene-based hydrogel, comprising the following steps:

[0021] Step 1, prepare an acrylamide precursor solution. The specific method is: add acrylamide, acrylic acid, liquid metal gallium-indium alloy and chitosan to deionized water, and perform ultrasonic fragmentation to fully dissolve them to obtain an acrylamide precursor solution;

[0022] Step 2, prepare an AM-MXene precursor solution. The specific method is: add Ti3C2T xThe dispersion liquid was added to the acrylamide precursor solution obtained in Step 1, stirred thoroughly and then allowed to stand to obtain the AM-MXene precursor solution;

[0023] Step 3: The AM-MXene precursor solution obtained in Step 2 was added with an initiator and stirred, and then poured into a mold or dropped in the middle of metal electrode clips, and allowed to stand until the product solidified into a gel to obtain a hydrogel;

[0024] In the said Step 1, the mass ratio of acrylamide to acrylic acid was 1:3 - 5;

[0025] The proportional relationship between acrylamide and deionized water was 2.4 - 2.5 g:10 ml;

[0026] The proportional relationship between chitosan and deionized water was 0.1 - 0.12 g:10 ml;

[0027] The proportional relationship between liquid metal gallium-indium alloy and deionized water was 1.5 g - 2 g:10 ml;

[0028] The temperature during mixing was 20 - 30 °C, and the ultrasonic crushing time was 3 min;

[0029] In the said Step 2, Ti3C2T x The concentration of the dispersion liquid was 10 mg / ml;

[0030] Ti3C2T x The volume ratio of the dispersion liquid to the acrylamide precursor solution was 1:20 - 21 ml;

[0031] In the said Step 3, the initiator was any one of benzoyl peroxide, ammonium persulfate, and potassium persulfate; the proportional relationship between the initiator and the AM-MXene precursor solution was 5 mg - 10 mg:1 ml;

[0032] In the said Step 3, the stirring time was 3 - 5 s, and the time for solidifying into a gel was 15 s - 45 s.

[0033] An application of a hydrogel: The hydrogel obtained by the preparation method of the present invention was made into a sensor with zinc sheets and attached to the skin or joints, and both ends of the electrode were connected to a circuit. Relevant resistance changes caused by related movements could be measured by using corresponding equipment.

[0034] The measurement sites for preparing it into a MXene hydrogel sensor were finger joints, wrist joints, elbow joints, knee joints, abdomen and larynx, and the measurement data was the resistance change rate of the MXene hydrogel.

[0035] The present invention provides an MXene hydrogel with high sensitivity and rapid gelation, as well as its preparation method and application, belonging to the technical field of conductive hydrogels. The MXene hydrogel of the present invention uses acrylamide, acrylic acid, chitosan, liquid metal gallium-indium alloy, and Ti3C2T x dispersion as the main raw materials. MXene and liquid metal gallium-indium alloy are added to the hydrogel system to increase its conductivity. At the same time, the acrylamide crosslinking network serves as the structural framework of the hydrogel to ensure its mechanical properties. The finally prepared MXene hydrogel has the ability of rapid crosslinking, can achieve rapid gelation within 15 - 45 s, and has extremely high sensitivity, good adhesion, and excellent electrical conductivity. The hydrogel electrode prepared by the present invention can be used in wearable devices to identify various minute movements of the human body by attaching to the skin or joints, and continuously collect human motion signals such as finger bending, joint movement, and breathing movement. Compared with traditional electrodes, the hydrogel of the present invention has rapid gelation, can be used immediately, has higher sensitivity, better stability, low cost, and simple operation, and has good application prospects.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) In the present invention, MXene is introduced to prepare the hydrogel. The introduction of MXene promotes the formation of a large number of hydrogen bonds between MXene,

[0038] water and the polymer network. At the same time, chitosan is added to enable MXene to form a stable dispersion, effectively preventing the precipitation of MXene. While ensuring the stability and mechanical properties of the hydrogel, the electrical conductivity of the hydrogel is further improved.

[0039] (2) The present invention utilizes the electrointeraction between acrylamide and the abundant functional groups (-OH, -COOH, etc.) on the surface of MXene to promote the rapid gelation of the hydrogel. At the same time, MXene acts as a crosslinking agent and rapidly forms a crosslinking network under the action of an initiator, achieving rapid gelation within 15 - 45 s.

[0040] (3) Using acrylamide and MXene as raw materials, the hydrogel prepared by the present invention has excellent sensitivity, good mechanical strength and biocompatibility, can closely adhere to the skin, and will not cause skin irritation. When the hydrogel acts directly on the skin surface, it will not cause irritation to the skin and is easy to peel off after use.

[0041] (4) In the MXene hydrogel prepared by the preparation method of the present invention, acrylamide formed by crosslinking is non-toxic and harmless. Silver, as a common wearable jewelry material, has been in direct contact with the skin for a long time without harm. Other materials are all non-hazardous chemicals, ensuring the biocompatibility of the sensor. Chitosan in the raw materials is naturally easy to obtain and has a low price, and has good application prospects.

[0042] (5) The present invention provides a method for preparing an MXene hydrogel with high sensitivity and rapid gelation, belonging to the scope of conductive hydrogels. The present invention uses acrylamide, acrylic acid, chitosan, liquid metal, and Ti3C2T x dispersion liquid as the main raw materials. MXene and liquid metal gallium-indium alloy are added to the hydrogel system to increase its conductivity. At the same time, acrylamide is used as the main framework to ensure its mechanical properties. The use of liquid metal gallium-indium alloy not only enhances the conductivity but also brings excellent interfacial contact performance to the hydrogel, making it have more extensive application potential in the fields of flexible electronics and sensing. The finally prepared MXene hydrogel has the ability of rapid crosslinking, can achieve rapid gelation within 15 - 45 s, and has good adhesion, stable and excellent conductive performance, and high sensitivity. The hydrogel sensor prepared by the present invention can be used in wearable devices, and can identify human motion signals by attaching to the skin or joints, and continuously collect human motion signals such as finger bending, joint movement, and breathing movement. Compared with traditional electrodes, the hydrogel of the present invention has rapid gelation, can be used immediately, has higher sensitivity, better stability, low cost, and simple operation, and has good application prospects. Brief Description of the Drawings

[0043] Figure 1 is a schematic diagram of the process for the method of preparing the MXene hydrogel of the present invention;

[0044] Figure 2 a is a physical photo of the MXene hydrogel of the present invention, Figure 2 b is a physical photo of the MXene hydrogel sensor of the present invention;

[0045] Figure 3 a and Figure 3 b are electron microscope structure photos of the MXene hydrogel of the present invention;

[0046] Figure 4 is the thermal imaging temperature change of the rapid gelation of the MXene hydrogel of the present invention;

[0047] Figure 5 is the graph of the change in tensile resistance sensitivity of the MXene hydrogel of the present invention;

[0048] Figure 6 is the graph of the change in resistance when the MXene hydrogel sensor of the present invention detects the movement of the index finger bending at 30°, 60°, and 90°;

[0049] Figure 7 a and Figure 7 b are respectively the graphs of the change in resistance when the MXene hydrogel sensor of the present invention detects the movement of breathing and deep breathing;

[0050] Figure 8 It is the resistance change diagram of the MXene hydrogel sensor of the present invention when detecting the movements of the wrist joint, elbow joint, and knee joint;

[0051] Figure 9 It is the schematic diagram of the use stability of the MXene hydrogel sensor of the present invention within one week;

[0052] Figure 10 It is the adhesion performance diagram of different materials of the MXene hydrogel of the present invention. Detailed implementation manners

[0053] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The experimental methods adopted in the present invention are all conventional methods. The materials, reagents, and instruments used, without special instructions, are all conventional materials, reagents, and instruments in the art, and those skilled in the art can obtain them through commercial channels.

[0054] As Figure 1 shown, a preparation method of a hydrogel based on MXene includes the following steps:

[0055] Step 1, prepare an acrylamide precursor solution. The specific method is: add acrylamide, acrylic acid, liquid metal gallium-indium alloy, and chitosan to ionic water, and perform ultrasonic fragmentation to dissolve them fully to obtain an acrylamide precursor solution;

[0056] Step 2, prepare an AM-MXene precursor solution. The specific method is: add the Ti3C2T x dispersion liquid to the acrylamide precursor solution obtained in Step 1, stir well and then let it stand to obtain an AM-MXene precursor solution;

[0057] Step 3, add potassium persulfate as an initiator to the AM-MXene precursor solution obtained in Step 2, stir appropriately, and immediately pour it into a mold or drop it between the metal electrode clips, and let it stand until the product solidifies into a gel to obtain MXene hydrogel.

[0058] Attach zinc sheets to both ends of the obtained MXene hydrogel as electrodes, and connect the circuit to obtain a resistive sensor. The sensor of the present invention can be attached to the human skin or joint part to accurately measure the resistance value change caused by the micro-movements of the human body.

[0059] Example 1

[0060] A preparation method of a hydrogel based on MXene specifically includes the following steps:

[0061] Step 1: Add 2.5 g (25 wt%) acrylamide, 0.625 g (6.25 wt%) acrylic acid, 0.1 g (1 wt%) chitosan, and 1.5 g (15 wt%) liquid metal gallium-indium alloy into 10 ml of deionized water, and perform ultrasonic fragmentation to fully dissolve them to obtain an acrylamide precursor solution;

[0062] Step 2: Take 1 ml (8.5 wt%) of Ti3C2T x (concentration 10 mg / ml) dispersion liquid and add it to the acrylamide precursor solution obtained in Step 1. After fully stirring at room temperature, let it stand to obtain an AM-MXene precursor solution;

[0063] Step 3: Add 0.1 g of initiator potassium persulfate to the AM-MXene precursor solution obtained in Step 2, stir appropriately for 5 s, and then immediately pour it into a mold or drop it between the metal electrode clips. Let it stand until the product solidifies into a gel, and name it PAM 2.5 -MXene 10mg -LM 1.5g hydrogel.

[0064] Example 2

[0065] The difference from Example 1 is that the mass of the liquid metal gallium-indium alloy added in Step 1 is 2 g (20 wt%), and the obtained product is PAM 2.5 -MXene 10mg -LM 2.0g hydrogel.

[0066] Comparative Example

[0067] The difference from Example 1 is that the 1.5 g of liquid metal gallium-indium alloy added in Step 1 is replaced with 1 g (10 wt%) of sodium chloride, and the obtained product is PAM 2.5 -MXene 10mg -Nacl hydrogel.

[0068] To test the electrical properties of the MXene hydrogel, use a CHI760E electrochemical workstation from Shanghai Chenhua Co., Ltd. Connect the MXene hydrogel electrodes (10 mm × 10 mm × 2 mm) to form an electrode pair. The reference electrode and the counter electrode are short-circuited and connected to one end of the electrode, and the working electrode is connected to the other end of the electrode to measure the impedance frequency curve and impedance diagram of the electrode pair.

[0069] Figure 1 This is the preparation method process schematic diagram of the PAM 2.5 -MXene 10mg -LM 1.5g hydrogel in Example 1.

[0070] Figure 2a is the PAM in Example 1 2.5 -MXene 10mg -LM 1.5g Schematic diagram of the physical photo of the hydrogel; Figure 2 b is the PAM in Example 1 2.5 -MXene 10mg -LM 1.5g Schematic diagram of the physical photo of the hydrogel sensor attached to the finger.

[0071] Figure 3 a and Figure 3 b illustrate the PAM in Example 1 of the present invention 2.5 -MXene 10mg Scanning electron microscope image (SEM) of the -Nacl hydrogel. It can be seen from the figure that the hydrogel has a uniform porous structure and good internal crosslinking.

[0072] Figure 4 is the PAM in Example 1 2.5 -MXene 10mg -LM 1.5g The hydrogel and the PAM in the comparative example 2.5 -MXene 10mg Thermal imaging temperature change of the -Nacl hydrogel with rapid gelation, indicating that the hydrogel of the present invention can rapidly react to form a gel after adding the crosslinking agent, and the maximum temperature range is 50 - 60 °C, which is lower than the heat loss threshold of the skin.

[0073] Figure 5 is the PAM in Example 1 2.5 -MXene 10mg -LM 1.5g The hydrogel and the PAM in the comparative example 2.5 -MXene 10mg Tensile resistance sensitivity change diagram of the -Nacl hydrogel; indicating that the hydrogel of the present invention has a high resistance change sensitivity when subjected to tensile deformation and has a good feedback to the force.

[0074] Figure 6 is the PAM in Example 1 2.5 -MXene 10mg -LM 1.5g Resistance change diagram of the hydrogel sensor when detecting finger bending at 30°, 60°, and 90° angles, indicating that the hydrogel of the present invention can accurately monitor human micro-movements and has a certain repeatability.

[0075] Figure 7 a and Figure 7 b are the PAM in Example 1 2.5 -MXene 10mg -LM 1.5gThe resistance change diagram of the hydrogel sensor during exercise breathing and deep breathing movements shows that the hydrogel of the present invention can accurately monitor different types of breathing actions of the human body and can be used to evaluate the daily physiological indicators of the human body.

[0076] Figure 8 It is PAM in Example 1 2.5 -MXene 10mg -LM 1.5g The resistance change diagram of the hydrogel sensor during the movement of the wrist joint, elbow joint, and knee joint; it shows that the hydrogel of the present invention has good monitoring and feedback for large-amplitude joint movements during exercise and has good application prospects in the field of whole-body movement monitoring.

[0077] Figure 9 It is the PAM in Example 2 2.5 -MXene 10mg -LM 2g After being made into a pressure sensor, the schematic diagram of the resistance signal change is collected after being placed at room temperature for 1 day, 3 days, and 7 days respectively. During a period of up to one week, the resistance signal of the sensor basically remained highly consistent, without obvious attenuation or fluctuation, indicating that the sensor has excellent long-term stability in a room-temperature environment. This stability ensures that the sensor can make accurate and reliable responses to forces (such as pressing) within one week.

[0078] Figure 10 It is the PAM in Example 1 2.5 -MXene 10mg The adhesion diagram of the hydrogel to different materials and human skin. From the figure, it can be seen that the hydrogel of the present invention has excellent adhesion to common materials in life and human skin, can produce good adhesion with the human epidermis under various material surfaces, and is applicable to a variety of scenarios.

[0079] In summary, the present invention has developed a highly sensitive MXene hydrogel sensor that can quickly form a gel. The hydrogel electrode prepared by the present invention can be used in wearable devices to identify human movement signals by attaching to the skin or joints, and continuously collect human action signals such as finger bending, joint movement, and breathing movement. Compared with traditional electrodes, the sensor of the present invention can quickly form a gel and be used immediately, has higher sensitivity, good stability, low cost, and simple operation, and has good application prospects.

[0080] In summary, the above is only the preferred embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A MXene-based hydrogel, characterized in that: The raw materials of the hydrogel include acrylamide, acrylic acid, liquid metal gallium-indium alloy, chitosan, deionized water, Ti3C2T x dispersion liquid and initiator; Calculated based on the total mass of the raw materials of the MXene hydrogel being 100%, the mass percentage content of each component is: Acrylamide 39%-42% Acrylic acid 9%-10% Liquid metal gallium-indium alloy 25%-31% Chitosan 1%-2% Ti3C2T x Dispersion liquid 18%-20% Initiator 1%-2% The balance is deionized water.

2. The MXene-based hydrogel according to claim 1, characterized in that: The initiator is any one of benzoyl peroxide, ammonium persulfate, and potassium persulfate.

3. A preparation method of an MXene-based hydrogel, characterized in that It includes the following steps: Step 1, prepare an acrylamide precursor solution. The specific method is: add acrylamide, acrylic acid, liquid metal gallium-indium alloy, and chitosan to deionized water, and perform ultrasonic fragmentation to dissolve them fully to obtain an acrylamide precursor solution; Step 2, configure the AM-MXene precursor solution. The specific method is as follows: Add the Ti3C2T x dispersion to the acrylamide precursor solution obtained in Step 1, stir well and then let it stand to obtain the AM-MXene precursor solution; Step 3, add an initiator to the AM-MXene precursor solution obtained in step 2, stir, and then let it stand until the product solidifies into a gel to obtain a hydrogel.

4. The method for preparing a MXene-based hydrogel according to claim 3, characterized in that: In step 1, the mass ratio of acrylamide to acrylic acid is 1:3-5; The proportional relationship between acrylamide and deionized water is 2.4-2.5 g:10 ml; The proportional relationship between chitosan and deionized water is 0.1-0.12 g:10 ml; The proportional relationship between liquid metal gallium-indium alloy and deionized water is 1.5 g-2 g:10 ml.

5. The method for preparing a MXene-based hydrogel according to claim 3, characterized in that: In step 1, the temperature during mixing is 20-30°C, and the ultrasonic fragmentation time is 3 min.

6. The method for preparing a MXene-based hydrogel according to claim 3, characterized in that: In the said step 2, the concentration of the Ti3C2T x dispersion is 10 mg / ml; Ti3C2T x The volume ratio of the dispersion liquid to the acrylamide precursor solution is 1:20 - 21 ml.

7. The method for preparing a MXene-based hydrogel according to claim 3, characterized in that: In step 3, the initiator is any one of benzoyl peroxide, ammonium persulfate, and potassium persulfate; the proportional relationship between the initiator and the AM-MXene precursor solution is 5 mg-10 mg:1 ml.

8. The method for preparing a MXene-based hydrogel according to claim 3, characterized in that: In step 3, the stirring time is 3-5 s, and the gel solidification time is 15 s-45 s.

9. The application of a MXene-based hydrogel, characterized in that: The obtained hydrogel is used to prepare a sensor with a zinc sheet and attached to the skin or joint. Both ends of the electrode are connected to a circuit, and the resistance change caused by movement is measured.

10. The application of a MXene-based hydrogel according to claim 9, characterized in that: During measurement, the measurement site is finger joint, wrist joint, elbow joint, knee joint, abdomen or throat, and the measurement data is the resistance change rate of the MXene hydrogel.

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