Conductive eutectic gel with high stretchability, ionic conductivity, low temperature resistance and self-repairing performance as well as preparation method and application of conductive eutectic gel

Abstract

The invention belongs to the field of intelligent soft materials, and discloses conductive eutectic gel with high stretchability, ionic conductivity, low temperature resistance and self-repairing performance and a preparation method and application thereof. The eutectic gel is composed of a deep eutectic solvent, a polymer monomer, keratin, PDA (at) Ag, a cross-linking agent, an initiator and pure water. According to strain sensing related tests, the gel has excellent strain sensing performance, and it is proved that the gel has excellent sensitivity and strain sensing performance and has application potential in the fields of high and low temperature severe environment monitoring, human health monitoring and motion detection.

Description

Technical Field

[0001] This invention belongs to the field of smart soft materials, and specifically relates to a conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties, as well as its preparation method and application. Background Technology

[0002] Hydrogels are polymeric materials with a three-dimensional cross-linked network structure. Due to their high water content, excellent flexibility, and mechanical properties similar to biological tissues, they have shown significant application value in fields such as flexible electronics, intelligent sensing, and biomedical engineering. Particularly in the field of wearable health monitoring, conductive hydrogels can detect human physiological signals in real time through ion or electron conduction mechanisms, such as limb movement, pulse, and electromyography, making them ideal flexible sensing materials. However, hydrogels still face a series of key challenges in practical applications. For example, in low-temperature environments, water freezing inevitably damages their network structure, leading to poor or even lost sensing performance, thus hindering the monitoring of highly sensitive signals in complex environments. Secondly, traditional hydrogels often suffer from insufficient mechanical strength, weak self-healing ability, easy detachment, and poor fatigue resistance, limiting their practicality in high-frequency dynamic monitoring and long-term health management. Therefore, there is an urgent need to develop multifunctional conductive gels that simultaneously possess high mechanical strength, excellent adhesion, high and low temperature resistance, and stable sensing performance to achieve medical diagnosis and treatment in rehabilitation exercises. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology and to solve the problems of stability and self-healing performance of wearable devices under extreme environments (low temperature) and large deformation processes, the primary objective of this invention is to provide a method for preparing a conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing performance.

[0004] Another objective of this invention is to provide a conductive eutectic gel with high tensile strength, ionic conductivity, low-temperature resistance, and self-healing properties prepared by the above-mentioned preparation method.

[0005] Another object of the present invention is to provide an application of the above-mentioned conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a conductive eutectic gel with high tensile strength, ionic conductivity, low-temperature resistance, and self-healing properties includes the following steps:

[0008] (1) By solution oxidation, dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution. The pH value of the dopamine hydrochloride ethanol / water mixed solution is adjusted with alkali solution and stirred to react. The dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles. After washing with detergent by centrifugation and freeze-drying, polydopamine lyophilized powder is obtained. The polydopamine lyophilized powder is then prepared into a polydopamine dispersion. Then, silver nitrate, pure water, ammonia water and the above polydopamine dispersion are mixed and stirred to react to form PDA@Ag nanoparticles. After washing with detergent by centrifugation and freeze-drying, PDA@Ag lyophilized powder is obtained.

[0009] (2) According to the molar ratio of ethylene glycol (EG) and conductive agent of 6:1, add conductive agent to ethylene glycol (EG), place in a hot water bath and stir until dissolved to prepare deep eutectic solvent;

[0010] (3) Using a one-pot mixing method, the PDA@Ag lyophilized powder, keratin, polymer monomer, crosslinking agent, initiator and pure water obtained in step (1) are added to the deep eutectic solvent obtained in step (2) and mixed evenly to obtain a prepolymer solution; the gel prepolymer solution is filled into a mold and heated to induce polymerization to obtain a conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties;

[0011] The polymer monomers are [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide (SBMA) and acrylic acid (AA); the crosslinking agent is N,N-methylenebisacrylamide, bisacrylamide, polyethylene glycol diacrylate, or polyethylene glycol dimethacrylate; the conductive agent is lithium chloride, zinc chloride, magnesium chloride, ferric chloride, or aluminum chloride.

[0012] The amount of PDA@Ag is 0.035 wt% of the conductive eutectic gel; the amount of keratin is 4.38 wt% of the conductive eutectic gel; the amount of polymer monomer is 51.62 wt% of the conductive eutectic gel; and the amount of deep eutectic solvent is 29.21% of the multifunctional conductive eutectic gel.

[0013] The pH value in step (1) is adjusted to 9-12; the temperature of the stirring reaction is 20-40℃, the reaction time is 12-36h, and the stirring speed is 300-800rpm; the alkaline solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; the detergent is pure water and anhydrous ethanol.

[0014] The molar ratio of dopamine hydrochloride to ammonium persulfate in step (1) is 2:1; the volume ratio of anhydrous ethanol to pure water is 2:7; and the total amount of dopamine hydrochloride and ammonium persulfate is 0.85 wt% of the dopamine hydrochloride ethanol / water mixed solution.

[0015] The temperature of the hot water bath in step (2) is 80°C.

[0016] The initiator in step (3) is potassium persulfate or ammonium persulfate.

[0017] The amount of crosslinking agent used in step (3) is 0.041 wt% of the conductive eutectic gel; the amount of initiator used is 0.583 wt% of the conductive eutectic gel; the heating-induced polymerization is carried out at 75°C for 1 hour.

[0018] The mold in step (3) is a sandwich structure constructed from glass sheets; the thickness of the final conductive eutectic gel is controlled by controlling the distance between the upper and lower glass sheets of the sandwich structure when the prepolymer liquid is filled into the mold.

[0019] A conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties, prepared by the above preparation method.

[0020] The above-mentioned conductive eutectic gel, which has high tensile strength, ionic conductivity, low temperature resistance and self-healing properties, is used as a conductor in sensors.

[0021] The aforementioned conductive eutectic gel, which possesses high tensile strength, ionic conductivity, low-temperature resistance, and self-healing properties, can be used for human motion monitoring in wearable devices, medical and health monitoring devices, or human-computer interaction devices.

[0022] The principle of this invention:

[0023] This method constructs a PDA@Ag / PAA / PSBMA / FK conductive eutectic gel through rational molecular design. The polymer monomers (AA and SBMA) can improve the adhesion performance, PDA in PDA@Ag provides broad light absorption and strong surface adhesion, while Ag nanoparticles greatly enhance the light-harvesting ability and local electromagnetic field due to their surface plasmon resonance effect. After the two are combined, Ag, as an efficient electronic conductor, accelerates charge transfer, while PDA dissipates the light energy captured by Ag through efficient non-radiative transition (heat generation), thereby significantly improving the photothermal conversion efficiency, conductivity and interfacial adhesion performance of the composite material. The abundant amide bonds, hydroxyl groups, and carboxyl groups in the FK (keratin) molecular chain form dense hydrogen bonds and ion-dipole interactions with the PAA segments, PSBMA segments, and functional groups on the surface of PDA@Ag nanoparticles in the polymer network, constructing dynamically reversible physical cross-linking points, thereby effectively dissipating energy. Simultaneously, FK's inherent biocompatible amino acid sequence and extracellular matrix-mimicking structure provide the gel with excellent cell affinity and tissue compatibility, further enhancing its safety as a wearable sensing material in long-term contact with the human body. Deep eutectic solvent (DES), with its strong hydrogen bond network, competitively binds water molecules, effectively inhibiting ice crystal formation and endowing the hydrogel with excellent antifreeze properties. At the same time, DES's extremely low vapor pressure and strong interaction with water molecules significantly slow down water evaporation, enhancing the material's water retention performance. In sensing, DES, as a high-density ion carrier, provides a large number of mobile charges, maintaining stable ionic conductivity over a wide temperature range, thus significantly improving the signal stability and environmental adaptability of the gel sensor.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) The present invention has a conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties. The conductive filler used is a eutectic conductive agent, which has excellent mechanical properties, fatigue resistance and stability. The keratin used is natural keratin, which does not need to be modified. Its inherent biocompatible amino acid sequence and extracellular matrix-like structure provide good cell affinity and tissue compatibility for the gel. It works synergistically with PDA@Ag to make the final eutectic gel have a high tensile strength of 1900% and a wide application temperature range, suitable for low temperature environments.

[0026] (2) The conductive eutectic gel of this invention has high tensile strength, ionic conductivity, low temperature resistance and self-healing properties. When used as a flexible sensor, it has high sensitivity, wide strain monitoring range, wide application temperature range and good cycle stability. The conductive filler is green and non-toxic, the preparation process is simple and the cost is low. It has great potential in the fields of high and low temperature harsh environment monitoring, human health monitoring and motion monitoring. Attached Figure Description

[0027] Figure 1 The images show the infrared spectra of the raw materials and products, where A represents the deep eutectic solvent (DES) and its components, zinc chloride conductive agent (ZnCl2) and ethylene glycol (EG); B represents the eutectic gel of SBMA, AA, FK and PDA@Ag / PAA / PSBMA / FK.

[0028] Figure 2 Fracture-tensile curves of PDA@Ag / PAA / PSBMA / FK eutectic gels with different keratin ratios.

[0029] Figure 3 Schematic diagram of the mechanical properties of PDA@Ag / PAA / PSBMA / FK eutectic gels with different proportions of DES; where A is the tensile stress-strain curve of PDA@Ag / PAA / PSBMA / FK eutectic gels with different proportions of DES; B is the elastic modulus and toughness of PDA@Ag / PAA / PSBMA / FK eutectic gels with different proportions of DES.

[0030] Figure 4 The adhesion strength of PDA@Ag / PAA / PSBMA / FK eutectic gel to different substrates.

[0031] Figure 5 This diagram illustrates the self-healing and stability testing of the PDA@Ag / PAA / PSBMA / FK eutectic gel. In the diagram, A shows the tensile changes of the gel after shearing, B shows the conductivity test of the LED bulb before and after self-healing in the PDA@Ag / PAA / PSBMA / FK eutectic gel, and C shows the dynamic strain step test diagram.

[0032] Figure 6 A bar chart showing the wide-temperature conductivity variation of the PDA@Ag / PAA / PSBMA / FK eutectic gel.

[0033] Figure 7 The diagram illustrates the changes in motion resistance at different parts of the body for the PDA@Ag / PAA / PSBMA / FK sensor. In this diagram, A represents the strain sensing sensitivity curve of the PDA@Ag / PAA / PSBMA / FK eutectic gel, B represents the eutectic gel attached to the finger at different bending angles, C represents the eutectic gel attached to the wrist at different bending angles, and D represents the finger joint bending cycle.

[0034] Figure 8The images show thermal images of the PDA@Ag / PAA / PSBMA / FK eutectic gel under NIR irradiation at different times. In the image, A is the photothermal heating curve of the PDA@Ag / PAA / PSBMA / FK conductive eutectic gel, and B is the temperature change curve of the PDA@Ag / PAA / PSBMA / FK conductive eutectic gel under near-infrared light cycling irradiation. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0036] The preparation process of the conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties in the following examples is carried out according to the following operation steps:

[0037] Step 1: Prepare a dopamine hydrochloride ethanol / water mixed solution by solution oxidation, using dopamine hydrochloride, ammonium persulfate, anhydrous ethanol, and pure water. The molar ratio of dopamine hydrochloride to ammonium persulfate is 2:1; the volume ratio of anhydrous ethanol to pure water is 2:7; the total amount of dopamine hydrochloride and ammonium persulfate is 0.85 wt% of the dopamine hydrochloride ethanol / water mixed solution; adjust the pH of the dopamine hydrochloride ethanol / water mixed solution to 9-12 with alkaline solution, and rotate at 300-800 rpm at 20-40℃. After stirring for 12-36 hours, dopamine hydrochloride undergoes oxidative self-polymerization to form polydopamine nanoparticles. These nanoparticles are then washed with detergent by centrifugation and freeze-dried to obtain polydopamine lyophilized powder. The polydopamine lyophilized powder is then formulated into a polydopamine dispersion. Silver nitrate, pure water, ammonia, and the above polydopamine dispersion are then mixed and stirred at 20-40°C and 300-800 rpm for 12-36 hours to form PDA@Ag nanoparticles. These nanoparticles are then washed with pure water and anhydrous ethanol by centrifugation and freeze-dried to obtain PDA@Ag lyophilized powder.

[0038] Step 2: According to the molar ratio of ethylene glycol (EG) to conductive agent of 6:1, add conductive agent to ethylene glycol (EG), place in an 80℃ hot water bath and stir until dissolved to prepare deep eutectic solvent;

[0039] Step 3: Using a one-pot mixing method, the PDA@Ag lyophilized powder, polymer monomers, keratin, crosslinking agent, initiator, and pure water obtained in Step 1 are added to the deep eutectic solvent obtained in Step 2 and mixed evenly to obtain a prepolymer solution; the gel prepolymer solution is filled into a mold and heated to induce polymerization to obtain a conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance, and self-healing properties.

[0040] Example 1

[0041] This embodiment provides a method for preparing PDA@Ag / PAA / PSBMA / FK eutectic gel, including the following specific steps:

[0042] Step 1: Mix dopamine hydrochloride (225 mg), ammonium persulfate (139.5 mg), anhydrous ethanol (10 mL), and pure water (35 mL) thoroughly. Adjust the pH to 9-12 by adding ammonia. Stir at 500 rpm at 20-40°C for 24 h. After centrifugation and washing with pure water and anhydrous ethanol, and freeze-drying, obtain polydopamine lyophilized powder. Stir AgNO3 (606.3 mg) and pure water (140 mL) vigorously for 0.5 h. Add ammonia dropwise (1 mL) until the solution changes from brown to transparent to obtain AgNO3 mixed solution. Disperse the prepared polydopamine lyophilized powder (147 mg) in 10 mL of pure water and slowly add it to the AgNO3 mixed solution. Stir slowly at 500 rpm at 20-40°C in the dark for 0.5 h. After centrifugation and washing with pure water and anhydrous ethanol, and freeze-drying, obtain PDA@Ag lyophilized powder.

[0043] Step 2: Add zinc chloride (0.67g) to ethylene glycol (1.83g), stir in an 80℃ hot water bath until dissolved, and prepare a deep eutectic solvent with a molar ratio of EG to ZnCl2 of 6:1;

[0044] Step 3: Add the PDA@Ag lyophilized powder (3mg), keratin (0.375g, keratin amount is 4.38wt% of conductive eutectic gel) obtained in Step 2, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) (0.5g), acrylic acid (2.5mL), N,N-methylenebisacrylamide (0.0035g), ammonium persulfate (0.0499g), and pure water (2.5mL) obtained in Step 2 to the deep eutectic solvent, and mix evenly to obtain PDA@Ag / PAA / PSBMA / FK prepolymer solution; fill the PDA@Ag / PAA / PSBMA / FK prepolymer solution into the sandwich structure mold, and control the thickness of the final gel by controlling the distance between the upper and lower glass plates of the sandwich. After heating at 75℃ for 1h, PDA@Ag / PAA / PSBMA / FK eutectic gel is obtained. By simply changing the amount of keratin to 2.96 wt%, 4.38 wt%, 5.76 wt%, 7.10 wt%, and 8.39 wt% of the conductive eutectic gel, PDA@Ag / PAA / PSBMA / FK-2.96%, PDA@Ag / PAA / PSBMA / FK-4.38%, PDA@Ag / PAA / PSBMA / FK-5.76%, PDA@Ag / PAA / PSBMA / FK-7.10%, and PDA@Ag / PAA / PSBMA / FK-8.39% conductive eutectic gels, respectively, can be prepared.

[0045] Experimental Results: The FT-IR spectrum of PDA@Ag / PAA / PSBMA / FK-4.38% conductive eutectic gel was analyzed, such as... Figure 1 As shown in A, for pure EG, at 3351 cm -1 The absorption peak at 883 cm⁻¹ is attributed to the -OH stretching vibration. -1 The absorption peak at 3351 cm⁻¹ is attributed to the -CH₂ bending vibration. When EG and ZnCl₂ are mixed in a certain molar ratio to form DES, the absorption peak in EG at 3351 cm⁻¹ is... -1 The -OH stretching band at that location widens and shifts to 3332 cm. -1 This spectral shift is likely a result of electron-electron transfer from oxygen to hydrogen bonds in EG, leading to changes in vibrational properties and indicating the formation of a hydrogen bond network between EG and ZnCl2. Furthermore, the -CH2 bending vibration shifts from 883 cm⁻¹ -1 Offset to 873cm -1 This further confirms the existence of hydrogen bonds between EG and ZnCl2. The FTIR spectra of the monomer and the conductive eutectic gel are as follows: Figure 1 As shown in B. In the SBMA spectrum, the peak appears at 1638 cm⁻¹. -1 Attributable to the stretching vibration of C=O on the ester carbonyl group, the peak occurs at 1218 cm⁻¹.-1 and 611cm -1 These vibrations are attributed to the stretching vibrations of the sulfonic acid groups S=O and SO, respectively. In the AA spectrum, the peak appears at 3442 cm⁻¹. -1 This vibration is attributed to the stretching vibration of -OH. The peak value appears at 1638 cm⁻¹. -1 It belongs to the C=C vibration. In the FK spectrum, the peak appears at 1630 cm⁻¹. -1 Attributable to the stretching vibration of C=O, the peak value appears at 663 cm. -1 This is attributed to the stretching vibration of CS. A 686 cm⁻¹ pattern appears in the spectrum of PDA@Ag / PAA / PSBMA / FK. -1 CS stretching vibration peak and 605cm -1 The SO bending vibration peak. Furthermore, at 1638 cm⁻¹. -1 The C=C double bond peak almost disappeared, indicating that the C=C bond had undergone a polymerization reaction. The gel simultaneously possessed the characteristic groups of each monomer, proving that SBMA and AA had been successfully copolymerized.

[0046] Example 2

[0047] This embodiment provides a method for evaluating the fracture tensile strength of PDA@Ag / PAA / PSBMA / FK eutectic gel, including the following steps:

[0048] The tensile properties of the five PDA@Ag / PAA / PSBMA / FK eutectic gels obtained in Example 1 were tested using a universal testing machine. The two ends of the eutectic gel were neatly clamped on the tensile testing machine, the tensile speed was set to 50 mm / min, and the stress-strain curves were recorded in real time until the eutectic gel broke.

[0049] Experimental results: such as Figure 2 As shown, the prepared PDA@Ag / PAA / PSBMA / FK conductive eutectic gels exhibit the following tensile strengths: 2.96% PDA@Ag / PAA / PSBMA / FK-2.96% has a tensile strength of 0.102 MPa and an elongation at break of 1716.7%; 4.38% PDA@Ag / PAA / PSBMA / FK-4.38% has a tensile strength of 0.124 MPa and an elongation at break of 1907%; 5.76% PDA@Ag / PAA / PSBMA / FK-5.76% has a tensile strength of 0.113 MPa and an elongation at break of 1780%; 7.10% PDA@Ag / PAA / PSBMA / FK-7.10% has a tensile strength of 0.107 MPa and an elongation at break of 1717.3%; and 8.39% PDA@Ag / PAA / PSBMA / FK-8.39% has a tensile strength of 0.094 MPa and an elongation at break of 1515%.

[0050] Example 3

[0051] This embodiment provides a method for evaluating the fracture tensile strength of PDA@Ag / PAA / PSBMA / FK eutectic gel, including the following steps:

[0052] Step 1: Add zinc chloride (0.67g) to ethylene glycol (1.83g), stir in an 80℃ hot water bath until dissolved, and prepare a deep eutectic solvent with a molar ratio of EG to ZnCl2 of 6:1. Change the amount of ethylene glycol and zinc chloride to prepare deep eutectic solvents with different molar ratios, that is, add 0.45g and 0.34g of zinc chloride to 2.05g and 2.16g of ethylene glycol respectively, stir in an 80℃ hot water bath until dissolved, and prepare deep eutectic solvents with a molar ratio of EG to ZnCl2 of 10:1 and 14:1 respectively.

[0053] Step 2: Fix the amount of keratin (0.375g, keratin amount is 4.38wt% of conductive eutectic gel), keep the amounts of other substances unchanged, only change the ratio of DES, use the three ratios of DES prepared in Step 1 (1:6, 1:10, 1:14) and operate as in Step 1 to prepare PDA@Ag / PAA / PSBMA / FK eutectic gels with different ratios of DES, respectively to prepare PDA@Ag / PAA / PSBMA / FK-①, PDA@Ag / PAA / PSBMA / FK-②, PDA@Ag / PAA / PSBMA / FK-③.

[0054] Step 3: Use a universal testing machine to test the tensile fracture properties of the three PDA@Ag / PAA / PSBMA / FK eutectic gels obtained in Example 3. The two ends of the eutectic gel are neatly clamped on a tensile testing machine, the tensile speed is set to 50 mm / min, and the stress-strain curves are recorded in real time until the eutectic gel breaks.

[0055] Experimental results: such as Figure 3 As shown in Figure A, the prepared PDA@Ag / PAA / PSBMA / FK conductive eutectic gel has a tensile strength of 0.113 MPa and an elongation at break of 1768%. Figure 3 As shown in Figure B, the elastic modulus of the PDA@Ag / PAA / PSBMA / FK-① eutectic gel is 6.32 kPa, and the toughness is 811.08 kJ / m. 3 The results indicate that the eutectic gel exhibits optimal mechanical properties when the DES ratio is 1:6. The mechanical properties of the eutectic gel increase with increasing ZnCl2 content. This is because ZnCl2 forms coordination bonds with polymer molecules, which, within a certain range, helps maintain a certain level of rigidity while allowing for high ductility. The addition of EG improves the toughness of the eutectic gel, and the synergistic effect of both significantly enhances the mechanical properties of the material.

[0056] Example 4

[0057] This embodiment provides a method for evaluating the adhesion performance of PDA@Ag / PAA / PSBMA / FK eutectic gel to different materials, including the following steps:

[0058] Step A: Prepare PDA@Ag / PAA / PSBMA / FK-4.38% eutectic gel. The steps are exactly the same as in Example 1. A PDA@Ag / PAA / PSBMA / FK conductive eutectic gel with a length (50 mm) * width (10 mm) * thickness (2 mm) is prepared.

[0059] Step B: Select five different adhesive substrates, including glass, metal, wood, plastic, and pigskin, and cut them all to a length (70mm) * width (30mm) size. Then, lay the eutectic gel prepared in Step A flat on one of the cut substrates, along the wide edge and length-to-length and width-to-width. Next, cover the other side of the eutectic gel with the same substrate, starting from the other wide edge, avoiding air bubbles between the adhesive surfaces. Then, clamp the protruding ends of the bonded substrates on a tensile testing machine, set the tensile speed to 100mm / min, and record the mechanical curves in real time until the two substrates completely separate. Perform three parallel tests for each substrate type.

[0060] Experimental results: such as Figure 4 As shown, the PDA@Ag / PAA / PSBMA / FK eutectic gel exhibits adhesion strengths of 17.04, 15.52, 20.58, 4.71, and 5.14 kPa to five substrates: glass, metal, wood, plastic, and pigskin, respectively. The prepared hydrogel can adhere to the surfaces of various substrates at room temperature and withstand a certain weight without peeling off. This is due to the abundant presence of quinone, catechol, amino, and carboxyl groups on the hydrogel surface, which facilitates hydrophobic, electrostatic, hydrogen bonding, ionic, and cation interactions at the interface, resulting in excellent adhesion. This superior adhesion performance ensures its stability during the assembly and testing of flexible strain sensors, which is beneficial for the accurate acquisition of electrical signals by the flexible strain sensors.

[0061] Example 5

[0062] Using the PDA@Ag / PAA / PSBMA / FK-4.38% eutectic gel obtained in Example 1 as the test sample, this example provides a method for evaluating the self-healing properties of the PDA@Ag / PAA / PSBMA / FK eutectic gel, including the following steps:

[0063] First, the strip of eutectic gel was cut in half lengthwise with scissors. Then, the cut surfaces of the two halves were gently pressed together and left to stand for 5–10 minutes to allow them to self-heal and adhere. Next, copper foil electrodes were attached to both ends of the gel and a circuit and a light bulb were connected. The bulb was observed to verify the initial conductivity before the gel was cut. Subsequently, the gel was cut, causing the bulb to go out. After the gel self-healed, the circuit was reconnected, and the bulb was observed to verify the restoration of conductivity after self-healing. Finally, the PDA@Ag / PAA / PSBMA / FK eutectic gel was subjected to repeated dynamic step strain tests (y = 1% and 3200%) at room temperature (25°C).

[0064] Experimental results: such as Figure 5 As shown in Figure A, the PDA@Ag / PAA / PSBMA / FK eutectic gel can self-heal after being cut and bonded together, and can still withstand a considerable degree of stretching. Figure 5 As shown in Figure B, when the eutectic gel is normal, the LED remains lit. When the hydrogel is cut, the LED immediately turns off, and its brightness is restored after reconnection. This indicates that the eutectic gel has electro-self-healing properties. Figure 5 As shown in Figure C, at a shear strain y = 1%, the storage modulus G' of the PDA@Ag / PAA / PSBMA / FK eutectic gel in its typical gel state is higher than the loss modulus G" (G' > G"). Once a shear strain y = 3200% is applied, the loss modulus G' of the PDA@Ag / PAA / PSBMA / FK eutectic gel becomes less than the storage modulus G" (G' > G"), indicating that the internal structure of the PDA@Ag / PAA / PSBMA / FK eutectic gel collapses, and the hydrogel is now in a sol state. However, when the strain is switched from 3200% to 1%, both the storage modulus G' and the loss modulus G" immediately recover to near their initial values. This recovery behavior is reversible in cyclic testing, indicating that the PDA@Ag / PAA / PSBMA / FK eutectic hydrogel possesses self-healing properties.

[0065] Example 6

[0066] A digital display cryogenic chamber and an electrochemical workstation were used together to test the wide-temperature conductivity of the PDA@Ag / PAA / PSBMA / FK-4.38% eutectic gel sensor obtained in Example 1. A 5mm wide conductive copper tape was neatly attached to both ends of the PDA@Ag / PAA / PSBMA / FK-4.38% eutectic gel, with the tape extended slightly. The PDA@Ag / PAA / PSBMA / FK eutectic gel with the conductive copper tape was then placed in the digital display cryogenic chamber, with the extended portion of the conductive copper tape outside the chamber. The sensor was then connected to the electrochemical workstation using the conductive copper tape. After the temperature dropped to the required level, it was held at that temperature for 15 minutes, and the impedance curves during this process were recorded in real time.

[0067] Experimental results: such as Figure 6 As shown, when the eutectic gel is placed at low temperatures, the thermal motion and diffusivity of water molecules slow down, leading to reduced mobility of charge carriers within the gel and increased internal resistance. Therefore, the conductivity decreases with decreasing temperature. Conversely, at high temperatures, the thermal motion and diffusivity of water molecules increase, resulting in faster charge carrier migration. The conductivity of the PDA@Ag / PAA / PSBMA / FK eutectic gel increases with increasing temperature. These results indicate that the eutectic gel maintains a certain conductivity from -20℃ to 60℃, meeting the requirements for monitoring applications in various harsh environments from high to low temperatures.

[0068] Example 7

[0069] This embodiment provides a method for evaluating strain sensing in PDA@Ag / PAA / PSBMA / FK eutectic gel, including the following steps:

[0070] Step A1: A universal testing machine and a multimeter were used together to test the strain sensing performance of the PDA@Ag / PAA / PSBMA / FK-4.38% conductive eutectic gel obtained in Example 1. A 5mm wide conductive copper tape was neatly attached to both ends of the conductive eutectic gel. The gel, along with the attached conductive copper tape, was then clamped onto a tensile testing machine, with the conductive copper tape extended. The conductive eutectic gel was then connected to the multimeter using the conductive copper tape. The tensile testing machine was then used to stretch / release the conductive eutectic gel under different strains, and the resistance change signal of the sensor was recorded in real time during the process.

[0071] Step B1: Use a multimeter to test the strain sensing performance of the PDA@Ag / PAA / PSBMA / FK eutectic gel sensor obtained in Example 1 at different human joints. Neatly attach 5mm wide conductive copper tape to both ends of the eutectic gel, then attach it to different human joints. Connect the sensor to the multimeter using the extended conductive copper tape, and record the resistance change signal of the sensor in real time during different bending angles of the joints.

[0072] Experimental results: such as Figure 7 As shown in Figure A, when the eutectic gel sensor was subjected to tensile / release stresses at different strains using a universal testing machine, the sensing sensitivity (GF) of the eutectic gel sensor reached 0.67 (0-100%), 1.76 (100-400%), and 19.23 (400-1000%), respectively. This indicates that the PDA@Ag / PAA / PSBMA / FK eutectic gel strain sensor has high sensitivity and a wide detection range, enabling it to monitor changes in electrical signals related to various human movements. Figure 7As shown in Figure B, the strain sensor mounted on the wrist can clearly distinguish the forward and backward flexion states of the wrist joint and the flexion angle, maintaining a stable and repetitive relative resistance response. Figure 7 As shown in Figure C, the relative change in resistance gradually increases with the increase of the finger bending angle. When the finger bending angle is fixed at a certain value, the relative change in resistance remains synchronized with the movement state, maintaining its original value. This confirms that the PDA@Ag / PAA / PSBMA / FK eutectic gel sensor can monitor changes in electrical signals during human movement. Figure 7 As shown in D, the electrical signals of the finger cyclically bending at 30°, 60° and 90° are almost consistent, and the relative resistance remains stable accordingly.

[0073] Example 8

[0074] This embodiment provides a method for evaluating the photothermal properties of PDA@Ag / PAA / PSBMA / FK conductive eutectic gel, including the following steps:

[0075] Step A2: Prepare PDA@Ag / PAA / PSBMA / FK-4.38% conductive eutectic gel. The steps are exactly the same as in Example 1. A PSBMA / PNIPAM / PAA / PDA@Ag conductive eutectic gel with a length (25mm) * width (25mm) * thickness (1mm) is prepared.

[0076] Step B2: Irradiate the conductive eutectic gel sample using an 808nm near-infrared laser and record the temperature change of the conductive eutectic gel sample during infrared light irradiation using an infrared imager. The power density of the near-infrared light is 0.3W / cm². -2 .

[0077] Experimental results: such as Figure 8 As shown in Figure A, the temperature of the conductive eutectic gel increased from 28℃ to 70℃ with increasing illumination time (0-4 min). This demonstrates its excellent photothermal properties. Figure 8 As shown in Figure B, in five consecutive irradiation-cooling cycles, the conductive eutectic gel recovered to ambient temperature within 7 minutes after each 4-minute near-infrared irradiation. The temperature curves were almost identical in each cycle, indicating that the PDA@Ag / PAA / PSBMA / FK eutectic gel has excellent photothermal stability and is suitable for near-infrared light-triggered thermotherapy.

[0078] The above embodiments are suitable implementations of the present invention. The implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a conductive eutectic gel with high stretchability, ionic conductivity, low-temperature resistance and self-repairing performance, characterized in that The following steps are included: (1) By solution oxidation, dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution. The pH value of the dopamine hydrochloride ethanol / water mixed solution is adjusted with alkali solution and stirred to react. The dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles. After washing with detergent by centrifugation and freeze-drying, polydopamine lyophilized powder is obtained. The polydopamine lyophilized powder is then prepared into a polydopamine dispersion. Then, silver nitrate, pure water, ammonia water and the above polydopamine dispersion are mixed and stirred to react to form PDA@Ag nanoparticles. After washing with detergent by centrifugation and freeze-drying, PDA@Ag lyophilized powder is obtained. (2) According to the molar ratio of ethylene glycol to conductive agent of 6:1, add conductive agent to ethylene glycol, place in an 80°C hot water bath and stir until dissolved to prepare deep eutectic solvent; (3) Using a one-pot mixing method, the PDA@Ag lyophilized powder, keratin, polymer monomer, crosslinking agent, initiator and pure water obtained in step (1) are added to the deep eutectic solvent obtained in step (2) and mixed evenly to obtain a prepolymer solution; the gel prepolymer solution is filled into a mold and heated to induce polymerization to obtain a conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties; The polymer monomers are [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide and acrylic acid; the crosslinking agent is N,N-methylenebisacrylamide, bisacrylamide, polyethylene glycol diacrylate or polyethylene glycol dimethacrylate; the conductive agent is lithium chloride, zinc chloride, magnesium chloride, ferric chloride or aluminum chloride. The amount of PDA@Ag is 0.035 wt% of the conductive eutectic gel; the amount of keratin is 4.38 wt% of the conductive eutectic gel; the amount of polymer monomer is 51.62 wt% of the conductive eutectic gel; and the amount of deep eutectic solvent is 29.21% of the multifunctional conductive eutectic gel.

2. The preparation method of the conductive eutectic gel with high stretchability, ion conductivity, low-temperature resistance and self-repairing performance according to claim 1, characterized in that: The pH value in step (1) is adjusted to 9-12; the temperature of the stirring reaction is 20-40℃, the reaction time is 12-36h, and the stirring speed is 300-800rpm; the alkaline solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; the detergent is pure water and anhydrous ethanol.

3. The preparation method of the conductive eutectic gel with high stretchability, ion conductivity, low-temperature resistance and self-repairing performance according to claim 1, characterized in that: The molar ratio of dopamine hydrochloride to ammonium persulfate in step (1) is 2:1; the volume ratio of anhydrous ethanol to pure water is 2:7; and the total amount of dopamine hydrochloride and ammonium persulfate is 0.85 wt% of the dopamine hydrochloride ethanol / water mixed solution.

4. The preparation method of the conductive eutectic gel with high stretchability, ion conductivity, low-temperature resistance and self-repairing performance according to claim 1, characterized in that: The temperature of the hot water bath in step (2) is 80°C.

5. The method for preparing a conductive eutectic gel with high tensile strength, ionic conductivity, low-temperature resistance, and self-healing properties according to claim 1, characterized in that: The initiator in step (3) is potassium persulfate or ammonium persulfate.

6. The method for preparing a conductive eutectic gel with high tensile strength, ionic conductivity, low-temperature resistance and self-healing properties according to claim 1, characterized in that: The amount of crosslinking agent used in step (3) is 0.041 wt% of the conductive eutectic gel; the amount of initiator used is 0.583 wt% of the conductive eutectic gel; the heating-induced polymerization is carried out at 75°C for 1 hour.

7. The method for preparing a conductive eutectic gel with high tensile strength, ionic conductivity, low-temperature resistance, and self-healing properties according to claim 1, characterized in that: The mold in step (3) is a sandwich structure constructed from glass sheets; the thickness of the final conductive eutectic gel is controlled by controlling the distance between the upper and lower glass sheets of the sandwich structure when the prepolymer liquid is filled into the mold.

8. A conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties, prepared by the preparation method according to any one of claims 1-7.

9. The application of the conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties as a conductor in a sensor, as described in claim 8.

10. The conductive eutectic gel with high tensile strength, ionic conductivity, low temperature resistance and self-healing properties as described in claim 8 is used in wearable devices, medical and health monitoring devices or human-computer interaction devices for human motion monitoring.

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