Preparation method and application of high-mechanical-strength eutectic gel based on polyethyleneimine

Abstract

The application belongs to the technical field of co-crystal gel, and discloses a preparation method and application of a high-mechanical-strength co-crystal gel based on polyethylene imine. The method uses polyethylene imine and glyceryl methacrylate as raw materials, choline chloride-acrylic acid and choline chloride-glycerol as deep eutectic solvents, and adds a photoinitiator and a crosslinking agent, so that a co-crystal gel network with high mechanical strength and ionic conductivity is constructed through multiple covalent chemical reactions and dynamic physical crosslinking. The prepared co-crystal gel can be used for monitoring human motion and temperature.

Description

Technical Field

[0001] This invention belongs to the field of eutectic gel technology, and particularly relates to a method for preparing and applying a high mechanical strength eutectic gel based on polyethyleneimine. Background Technology

[0002] With the rapid development of flexible electronics technology, cutting-edge fields such as wearable smart devices, soft robots, human-computer interaction, and extreme environment monitoring have placed more stringent demands on the mechanical stability, environmental adaptability, and sensing reliability of core functional materials. Eutectic gels, emerging green flexible materials using eutectic solvents as dispersion media, possess significant advantages over traditional hydrogels and ionomers, including low volatility, wide-temperature-range structural stability, excellent biocompatibility, and low preparation cost. They also exhibit excellent intrinsic ionic conductivity and tunable physicochemical properties, making them highly valuable for applications and industrialization in flexible sensing, energy storage devices, and smart flexible terminals.

[0003] However, existing conventional eutectic gel systems still face significant technical bottlenecks, greatly limiting their engineering and industrial applications. Currently, the polymer crosslinking networks of eutectic gels generally suffer from defects such as uneven crosslinking density distribution, insufficient overall mechanical strength, and poor dynamic resistance to deformation. During free radical polymerization, the system is prone to localized areas of excessive or sparse crosslinking, leading to stress concentration and uneven dissipation under stress, forming numerous micro- and nano-scale mechanically weak points. Initial micro-defects generated during material processing and the minor damage caused by repeated stretching, bending, and friction during service can all induce crack initiation and rapid propagation, ultimately leading to gel structure damage, breakage of conductive pathways, and resulting in device sensing performance degradation, signal distortion, or even complete failure.

[0004] In summary, existing eutectic gels generally suffer from poor mechanical toughness, weak fatigue resistance, and insufficient service stability, making it difficult to meet the requirements of flexible sensing applications involving complex deformation and long-term cyclic operation. Therefore, developing a eutectic gel system that combines ultra-high mechanical strength, excellent fatigue resistance, and stable ionic conductivity is a pressing technical challenge and core research direction in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing eutectic gels, such as insufficient mechanical strength, poor fatigue resistance, weak service stability, and limited sensing performance, and to provide a method for preparing a high-mechanical-strength eutectic gel based on polyethyleneimine and its applications. This invention utilizes the nucleophilic ring-opening reaction between the amino groups on the polyethyleneimine molecular chain and the epoxy groups of glycerol methacrylate to construct a stable covalent cross-linked network. Simultaneously, the carboxylate anions formed by the dissociation of acrylic acid can generate strong electrostatic interactions with the protonated amino cations on polyethyleneimine, constructing dynamic non-covalent physical cross-links. Through the synergistic effect of covalent cross-linking and dynamic physical cross-linking, the internal network structure of the gel is effectively optimized, stress is dispersed, and the mechanical strength and structural stability of the eutectic gel are significantly improved. The eutectic gel prepared by this invention possesses both excellent ionic conductivity and low-temperature antifreeze properties, and can be effectively applied in the field of flexible wearable sensing. It can not only accurately monitor the movement behavior of various joints and limbs in the human body, but also achieve stable identification and detection of environmental and human body temperatures.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a method for preparing a high-mechanical-strength eutectic gel based on polyethyleneimine, comprising the following steps: S1. Choline chloride and acrylic acid are mixed and stirred evenly to prepare a choline chloride-acrylic acid deep eutectic solvent; choline chloride and glycerol are mixed and stirred evenly to prepare a choline chloride-glycerol deep eutectic solvent. S2. Polyethyleneimine is added to the choline chloride-glycerol deep eutectic solvent and stirred to obtain a homogeneous mixed solution; then the choline chloride-acrylic acid deep eutectic solvent is added and stirred to mix evenly; then glycerol methacrylate is added and stirred to mix evenly; finally, crosslinking agent and photoinitiator are added and stirred until completely dissolved to obtain a precursor solution; S3. Immediately subject the precursor solution obtained in step S2 to ultrasonic degassing treatment, then inject it into a polytetrafluoroethylene mold and cure it by ultraviolet light to form a gel. S4. Place the gel obtained in step S3 in an oven for constant temperature reaction, and demold after natural cooling to obtain a high mechanical strength eutectic gel based on polyethyleneimine (PEI-GMA).

[0007] Further, in step S1, the molar ratio of choline chloride to acrylic acid and choline chloride to glycerol is 1:2, the stirring temperature is 60~80℃, and the stirring time is 1~2h.

[0008] Further, in step S2, the mass ratio of polyethyleneimine, choline chloride-glycerol deep eutectic solvent, choline chloride-acrylic acid deep eutectic solvent, glyceryl methacrylate, crosslinking agent, and photoinitiator is 0.1~0.5g:4g:6g:0.05~0.25g:0.05g:0.03g.

[0009] Further, in step S2, the crosslinking agent is polyethylene glycol diacrylate, and the photoinitiator is photoinitiator I2959.

[0010] Furthermore, in step S3, the ultrasonic degassing treatment time is 5~10 minutes.

[0011] Furthermore, in step S3, the wavelength of the ultraviolet lamp used for curing is 365nm, and the curing time is 5min.

[0012] Furthermore, in step S4, the reaction temperature of the isothermal reaction is 100°C and the reaction time is 2 hours.

[0013] A second aspect of this invention provides an application of the high mechanical strength eutectic gel prepared by the above-described method, which can be used to prepare flexible strain sensors or temperature-type flexible sensors. The flexible strain sensor utilizes the change in ion conductivity paths during the tensile deformation of the eutectic gel to output a corresponding resistance change signal, thereby achieving flexible deformation signal detection. The temperature-type flexible sensor utilizes the characteristic of the change in ion conductivity within the eutectic gel with temperature to output a corresponding resistance change signal, thereby achieving temperature detection.

[0014] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. This invention fundamentally solves the technical problems of uneven cross-linking, numerous mechanical weaknesses, easy cracking under stress, and easy dissolution of conductive components in traditional eutectic gels by constructing a synergistic dual-network structure of "covalent cross-linking-dynamic physical cross-linking". Specifically, the amino group of polyethyleneimine undergoes a nucleophilic ring-opening reaction with the epoxy group of glyceryl methacrylate to form a high-strength, high-stability covalent cross-linked backbone; at the same time, acrylic acid and the unsaturated double bond of glyceryl methacrylate undergo random copolymerization, covalently anchoring the conductive components in the deep eutectic solvent to the polymer backbone, completely avoiding the problems of migration, precipitation, and loss of conductive small molecules that are common in traditional ionic gels and eutectic gels, and significantly improving the long-term service stability of the material. Meanwhile, the carboxylate anion in acrylic acid and the protonated amino cation in polyethyleneimine form a strong electrostatic interaction, constructing a dynamic and reversible physical cross-linking network, which can effectively dissipate stress and inhibit crack propagation under external force, significantly improving the overall mechanical strength, toughness, and structural stability of the gel.

[0015] 2. This invention leverages a deep eutectic solvent system to impart excellent intrinsic ionic conductivity to the material, enabling the eutectic gel to possess both high mechanical properties and highly sensitive sensing characteristics. This eutectic gel exhibits excellent sensing sensitivity over a wide strain range, with a strain coefficient reaching 2.06, and demonstrates stable electrical signal response and excellent repeatability during 250 consecutive tensile cycles. Low-temperature testing results show that the material exhibits no significant thermal absorption peak and no ice crystal formation within the temperature range of -70℃ to 20℃, demonstrating excellent low-temperature resistance and wide-temperature-range operational stability, making it adaptable to complex, low-temperature, and extreme environmental conditions.

[0016] 3. The eutectic gel prepared in this invention can be used to construct high-performance multimodal flexible sensors, possessing both strain sensing and temperature sensing capabilities. This sensor can accurately acquire deformation signals through dynamic changes in ion conductivity paths, enabling the identification of flexible deformations at different scales and human movement behaviors. Simultaneously, it can achieve high-precision temperature detection by relying on the mechanism of temperature-controlled ion migration rates, achieving a temperature coefficient of -4.6% / ℃ within the 25–80℃ range, exhibiting excellent temperature sensitivity. This invention effectively solves the technical defects of existing flexible sensing materials, such as poor mechanical stability, weak fatigue resistance, insufficient environmental adaptability, low sensing accuracy, and easy performance degradation, and has broad application prospects in flexible electronics, wearable monitoring, intelligent sensing, and human-computer interaction. Attached Figure Description

[0017] Figure 1 This is the reaction equation for polyethyleneimine (PEI) and glyceryl methacrylate (GMA) in this invention.

[0018] Figure 2 Glyceryl methacrylate (GMA) and PEI obtained in Example 1 0.5 -GMA 0.1 and the PEI obtained from Comparative Example 1 0.5 The Fourier transform infrared (FTIR) spectra are shown in the comparison diagram, with the inset being a magnified view of a portion of the spectrum.

[0019] Figure 3 Differential scanning calorimetry (DSC) curves of the eutectic gel prepared in Example 1.

[0020] Figure 4 The mechanical properties and fatigue durability of the eutectic gels obtained in each embodiment and comparative example are shown in the figure. (a) is the tensile stress-strain curve of comparative example 1; (b) is the tensile stress-strain curve of each embodiment; (c) is the cyclic loading-unloading curve of example 1 at different strains of 50%, 100%, and 150%; (d) is the comparison of dissipation energy of example 1 at different strains; (e) is the continuous cyclic loading-unloading curve of example 1 at 150% strain (without interruption); (f) is the change of dissipation energy during the cyclic tensile process of example 1.

[0021] Figure 5 The rheological properties of the eutectic gel obtained in Example 1 are shown in the following figures: (a) shows the curves of storage modulus (G') and loss modulus (G'') as a function of strain; (b) shows the curves of storage modulus (G') and loss modulus (G'') as a function of frequency.

[0022] Figure 6 A photograph demonstrating the circuit conductivity of the eutectic gel obtained in Example 1. Figure 6 (a) and a schematic diagram of the change in bulb brightness during the stretching process. Figure 6 (b) in the middle.

[0023] Figure 7 The following are the electrical performance test results of the eutectic gel obtained in Example 1, wherein: (a) is the real-time tensile sensing response curve of Example 1 under different strains of 25%, 50%, and 75%; (b) is the fitting curve of relative resistance change and strain coefficient (GF) of Example 1 in the strain range of 0%-75%; (c) is the dynamic response curve of Example 1 at different tensile rates under 50% strain; and (d) is the stability test curve of Example 1 under continuous cyclic tensile stress at 50% strain. The inset in the figure is a partial magnified view.

[0024] Figure 8 The following is an example of the application of the eutectic gel obtained in Example 1 in human motion monitoring in wearable strain sensing, wherein: (a) is the electrical signal response curve under different finger bending angles; (b) is the electrical signal response curve under wrist bending action; (c) is the electrical signal response curve under elbow bending action; (d) is the electrical signal response curve under leg bending action; (e) is the electrical signal response curve under the volunteer's mouth opening action; and (f) is the electrical signal response curve under the volunteer's swallowing action.

[0025] Figure 9 The following is an example of the application of the eutectic gel obtained in Example 1 in temperature sensing, wherein: (a) is the temperature response sensitivity curve of the eutectic gel; (b) is the resistance step response curve of the eutectic gel during the process of temperature rising from 25℃ to 80℃; (c) and (d) are the real-time response test results of the eutectic gel to temperature changes. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The raw materials used in the following examples include: polyethyleneimine (weight average molecular weight Mw=25000), glyceryl methacrylate (purity 97%), choline chloride (purity 99%), acrylic acid (purity ≥99%), glycerol (purity ≥99%), polyethylene glycol diacrylate (Mw=200), photoinitiator I2959, and deionized water; the above raw materials, UV box, and PTFE mold were all purchased from the market and used directly.

[0028] Example 1 In this embodiment, a high mechanical strength eutectic gel based on polyethyleneimine was prepared according to the following steps: S1. Preparation of deep eutectic solvent: Choline chloride and glycerol were mixed in a molar ratio of 1:2 and stirred and heated in a water bath at 75°C for 1 hour to obtain choline chloride-glycerol deep eutectic solvent; choline chloride and acrylic acid were mixed in a molar ratio of 1:2 and stirred and heated in a water bath at 75°C for 1 hour to obtain choline chloride-acrylic acid deep eutectic solvent.

[0029] S2. Preparation of precursor solution: Take 4g of the choline chloride-glycerol deep eutectic solvent prepared above, add 0.5g of polyethyleneimine, stir at room temperature until completely dissolved to obtain a homogeneous mixed solution; continue to add 6g of choline chloride-acrylic acid deep eutectic solvent to the system, and stir thoroughly until the system is homogeneous; then add 0.1g of glyceryl methacrylate, and stir until the solution is homogeneous; finally, add 0.03g of photoinitiator I2959 and 0.05g of polyethylene glycol diacrylate in sequence, and continue stirring until all additives are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0030] S3. UV curing: Immediately after preparing the precursor solution, ultrasonically degas it for 5 minutes, then quickly inject it into a polytetrafluoroethylene mold and cure it with a 365nm UV lamp for 5 minutes to form a gel.

[0031] S4. High-Temperature Post-treatment Molding: The UV-cured gel is placed in a 100℃ oven for a constant temperature reaction for 2 hours. After removal, it is allowed to cool naturally to room temperature. Demolding yields a high-mechanical-strength eutectic gel, named PEI. 0.5 -GMA 0.1 .

[0032] Example 2 This embodiment prepares a high-mechanical-strength eutectic gel based on polyethyleneimine using the same process steps and conditions as in Example 1, the only difference being that the amount of glyceryl methacrylate added is 0.05 g. The resulting eutectic gel is named PEI. 0.5 -GMA 0.05 .

[0033] Example 3 This embodiment prepares a high-mechanical-strength eutectic gel based on polyethyleneimine using the same process steps and conditions as in Example 1, the only difference being the addition of glyceryl methacrylate at a rate of 0.15 g. The resulting eutectic gel is named PEI. 0.5 -GMA 0.15 .

[0034] Example 4 This embodiment prepares a high-mechanical-strength eutectic gel based on polyethyleneimine using the same process steps and conditions as in Example 1, the only difference being the addition of glyceryl methacrylate at a rate of 0.2 g. The resulting eutectic gel is named PEI. 0.5 -GMA 0.2 .

[0035] Example 5 This embodiment prepares a high-mechanical-strength eutectic gel based on polyethyleneimine using the same process steps and conditions as in Example 1, the only difference being the addition of glyceryl methacrylate at a rate of 0.25 g. The resulting eutectic gel is named PEI. 0.5 -GMA 0.25 .

[0036] Comparative Example 1 This comparative example prepared a polyethyleneimine-based cocrystalline gel using the same process steps and conditions as in Example 1, except that the amount of glyceryl methacrylate added was 0, and the cocrystalline gel was obtained immediately after UV curing, eliminating the need for the high-temperature post-treatment molding step S4. Changing the amount of polyethyleneimine to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g, the resulting cocrystalline gels were named PEI. x x represents the amount of polyethyleneimine used.

[0037] The samples obtained from the above embodiments and comparative examples were characterized and tested as follows: 1. Fourier transform infrared spectroscopy Figure 2 For GMA, PEI 0.5 and PEI 0.5 -GMA 0.1 The Fourier transform infrared (FTIR) spectroscopy comparison confirmed the successful epoxy ring-opening reaction between polyethyleneimine (PEI) and glyceryl methacrylate (GMA). Compared with pure GMA, PEI... 0.5 -GMA 0.1 In the sample, epoxy groups are located at approximately 908 cm⁻¹ -1 The characteristic absorption peak (C-O bond stretching vibration) at approximately 3300 cm⁻¹ significantly weakened and essentially disappeared, indicating that the epoxy ring in GMA had been opened by the amino group of PEI; simultaneously, at approximately 3300 cm⁻¹... -1The absorption peak intensity of the nearby -OH stretching vibration is significantly enhanced, which is due to the formation of a large number of hydroxyl groups after the epoxy ring-opening, further confirming the occurrence of the ring-opening reaction. These changes indicate that a stable covalent cross-linked network has been formed between PEI and GMA. The presence of a large number of hydroxyl groups in the network can further enhance intermolecular interactions through hydrogen bonding, making a significant contribution to improving the mechanical strength and structural stability of the material.

[0038] 2. Freeze resistance test The PEI eutectic gel prepared in Example 1 was analyzed using a differential scanning calorimeter (DSC2500, TA Instruments, USA). 0.5 -GMA 0.1 The antifreeze properties were characterized. The test conditions were a nitrogen atmosphere, a heating rate of 5℃ / min, and a temperature scan range of -70℃ to 20℃.

[0039] Figure 3 The figure shows the DSC curve of the eutectic gel. As can be seen from the figure, no obvious endothermic peaks appeared in the entire temperature range of -70℃ to 20℃, indicating that there was no ice crystal melting phenomenon in the gel system and that water did not crystallize. This shows that the eutectic gel prepared by this invention has excellent antifreeze properties, can maintain structural stability and functional integrity in low-temperature environments, and can work normally under cold conditions.

[0040] 3. Mechanical performance testing The mechanical properties of each sample were tested using an Instron 5967 universal testing machine (USA). The test conditions were: ambient temperature 25℃, relative humidity 40%, sample size 80mm × 10mm × 5mm, and tensile rate 50mm / min. To optimize the mechanical properties of the PEI-GMA eutectic gel, [further testing was conducted]. Figure 4 (a) and Figure 4 The uniaxial tensile test in (b) systematically investigated the effects of polyethyleneimine (PEI) and glyceryl methacrylate (GMA) content on the mechanical properties of gel.

[0041] Figure 4 Figure (a) shows the stress-strain curves of eutectic gels with different PEI contents (0.1-0.5 g). With increasing PEI content, the abundant amino groups on its molecular chains can form high-density hydrogen bonds and physical cross-linking points, while simultaneously promoting chain entanglement and ion-dipole interactions, effectively dissipating stress and significantly improving the mechanical strength and ductility of the gel. When the PEI content is 0.5 g, PEI... 0.5 Eutectic gel exhibits the best mechanical properties, with a tensile strength of 0.92 MPa and an elongation at break of 564%. When the amount of PEI exceeds 0.5 g (e.g., 0.6 g), the system concentration becomes too high, making it impossible to form a homogeneous solution and thus compromising the feasibility of the process.

[0042] Figure 4 (b) shows the stress-strain curves of PEI-GMA eutectic gels with different GMA contents (0.05-0.25 g). After introducing GMA, Example 1 (PEI...) 0.5 -GMA 0.1 The tensile strength of the gel was increased to 4.02 MPa, demonstrating a significant reinforcing effect. The mechanism is as follows: the amino groups of PEI and the epoxy groups of GMA undergo a nucleophilic ring-opening reaction, constructing a stable covalent chemical cross-linking network; simultaneously, the carboxylate anions dissociated from acrylic acid and the protonated amino cations of PEI form a dynamic physical cross-linking through strong electrostatic interaction. These two components synergistically construct a dual-network structure, optimizing the cross-linking density and improving mechanical properties. When the amount of GMA further increases, the tensile strength and elongation at break of the gel show a decreasing trend. This is because excessive GMA leads to over-cross-linking of the network, introducing structural defects and weakening the material's toughness and mechanical stability.

[0043] To evaluate the fatigue resistance of the samples obtained in Example 1, continuous loading-unloading cycle tests were conducted under different strains: Figure 4 (c) shows the loading-unloading curves at 50%, 100%, and 150% strain. As strain increases, the hysteresis loop area expands significantly, indicating that the energy dissipation capacity of the gel increases with increasing strain (corresponding to...). Figure 4 The trend of dissipated energy change in (d) of the figure.

[0044] Figure 4 (e) in the figure represents the loading-unloading curves of 10 consecutive cycles under 150% strain. The curves show a clear hysteresis loop, indicating that the physical cross-linking (electrostatic interaction, hydrogen bonding) inside the gel undergoes reversible breakage and recombination during the stretching process, achieving efficient energy dissipation.

[0045] Depend on Figure 4 As can be seen from (f), the dissipation energy of the first cycle is significantly higher than that of the subsequent cycles. The dissipation energy of the subsequent 9 cycles tends to be stable, indicating that the eutectic gel of Example 1 enters a stable state of mechanical response after experiencing initial stress relaxation, and has excellent structural durability and fatigue resistance.

[0046] 4. Rheological property testing Rheological properties were tested using an Anton Paar MCR 702 rotational rheometer. The test fixture employed a plate-to-plate geometry, and the test temperature was maintained at room temperature (25°C) by the instrument's built-in temperature control unit. Tests were conducted in oscillation / dynamic mode, and the relationship between storage modulus (G') and loss modulus (G") as a function of load was obtained through stress / strain scanning. Frequency scanning tests were performed at 1% strain, with a frequency range of 0.1–100 rad / s; dynamic strain scanning tests were performed at a frequency of 6.28 rad / s, with a strain range of 0.01%–1000%. The linear viscoelastic range and initial storage modulus of the sample were determined using data from the low-stress region, while the yielding and failure behavior of the network structure was observed using data from the high-stress region. This was used to evaluate the solid-like characteristics of the conductive eutectic gel under small deformations and the network stability under external forces. Figure 5 The PEI obtained in Example 1 0.5 -GMA 0.1 Rheological property test curves of the samples: Figure 5 (a) shows the strain scan curve of the sample at a frequency of 6.28 rad / s. Within the strain range of 0.01%-200%, the storage modulus G' remains stable and is significantly higher than the loss modulus G", indicating that the material has a wide linear viscoelastic range and the three-dimensional network structure can remain stable under large deformation. When the strain exceeds 200%, G' decreases significantly, marking the beginning of irreversible structural damage to the gel network.

[0047] Figure 5 (b) shows the frequency sweep curve of the sample in the linear viscoelastic region (1% strain). G' and G'' both remain at 10 rad / s across the full frequency range of 0.1–100 rad / s. 5 The Pa value was always greater than G'', indicating a weak frequency dependence, which confirmed the successful construction of the high-strength covalently cross-linked network.

[0048] The above rheological results show that Example 1 has both excellent resistance to deformation and dynamic mechanical stability, and can adapt to application scenarios such as flexible sensors that need to withstand large deformations and dynamic loads.

[0049] 5. Electrical performance testing Figure 6 A photograph demonstrating the circuit conductivity of the eutectic gel obtained in Example 1. Figure 6 (a) and the change in bulb brightness during the stretching process (Figure 1) Figure 6(b)). When the eutectic gel is connected to the circuit, the light bulb lights up normally; however, when the gel is stretched, the brightness of the bulb decreases significantly. This phenomenon is due to the fact that tensile strain elongates and alters the ion conduction path within the gel, increasing ion migration resistance and reducing the ion conductivity of the system, thereby reducing the circuit current. This clearly demonstrates that the eutectic gel prepared in this invention possesses excellent strain response characteristics and can be used as a flexible strain sensing material.

[0050] Figure 7 Electrical performance test results of the eutectic gel prepared in Example 1: Figure 7 Figure (a) shows the real-time relative resistance change curves under different strains (25%, 50%, 75%). The results show that the relative resistance change rate (ΔR / R0) of the eutectic gel is significantly positively correlated with the tensile strain, and the signal is stable under constant strain conditions without obvious drift, indicating that the sensor has good signal stability. In the figure, R0 is the initial resistance and ΔR is the resistance change.

[0051] Figure 7 Figure (b) shows the linear fitting curve of the eutectic gel in the strain range of 0%-75%, with a strain coefficient (GF) of 2.06 and a linear correlation coefficient R. 2 The accuracy rate reached 99.99%, demonstrating that the sensor has excellent sensitivity and linear response capabilities within this strain range.

[0052] Figure 7 (c) shows the dynamic response curves of the eutectic gel at different stretching rates (slow, medium, and fast). Under 50% strain conditions, the stretch-release process at different rates can generate stable and repeatable resistance change signals, demonstrating excellent dynamic response and repeatability.

[0053] Figure 7 Figure (d) shows the stability test curve of the eutectic gel after 250 cycles of continuous tensile stress at 50% strain. After multiple cycles of loading, the resistance response signal of the eutectic gel showed no significant attenuation, indicating that it has excellent fatigue resistance and long-term stability.

[0054] The above results show that the eutectic gel prepared by the present invention has excellent ionic conductivity, high strain sensitivity, good linearity and cyclic stability, which can meet the application requirements of flexible wearable strain sensors.

[0055] 6. Application of eutectic gel in human motion monitoring The eutectic gel prepared in Example 1 was attached to different body parts of volunteers, with electrodes connected to both ends. An electrochemical workstation was used to collect and record resistance changes under different movements in real time to verify its human motion monitoring performance. The test results are as follows: Figure 8 As shown.

[0056] Figure 8 (a) shows the electrical response curves of the finger at different bending angles. As the finger bending angle increases, the relative resistance change rate (ΔR / R0) of the sensor increases synchronously, and the signal is stable with a clear step response, which can realize quantitative monitoring of the joint bending amplitude.

[0057] Figure 8 Figures (b)-(d) show the real-time response curves for wrist flexion, elbow flexion, and knee flexion, respectively. The sensor outputs repeatable and stable resistance change signals during the periodic flexion-extension process of the limb joints, indicating its excellent dynamic response capability to large-amplitude limb movements.

[0058] Figure 8 In the figure, (e)-(f) represent the response curves for mouth opening and swallowing actions, respectively. The sensor can capture the minute deformations caused by facial muscle movements and subtle throat movements, and output characteristic electrical signal responses to achieve precise monitoring of subtle physiological movements.

[0059] The above results indicate that the eutectic gel patch prepared by the present invention can be used as a flexible strain sensor to stably and sensitively monitor various movement states of the human body, from large-amplitude limb movements to subtle physiological activities in real time, and has broad application prospects in wearable health monitoring, human-computer interaction and other fields.

[0060] 7. Application of eutectic gel in temperature monitoring The eutectic gel prepared in this invention possesses excellent temperature response characteristics based on the intrinsic ionic conductivity of deep eutectic solvents, and can be used to construct high-sensitivity temperature sensors. Its working principle is as follows: temperature changes significantly affect the migration rate of ions within the system. As the temperature increases, the ion velocity in the conductive path accelerates, increasing conductivity and thus achieving a real-time temperature response. To optimize the linear relationship between temperature and the response signal, the response range of the temperature sensor prepared in Example 1 is divided into three segments for analysis: Figure 9 Figure (a) shows the temperature-resistance response curve of the sensor in the range of 25~80℃. In the 25~35℃ range, the temperature coefficient (TCR) reaches -4.6% / ℃; in the 35~45℃ range, it is -2.2% / ℃; and in the 45~80℃ range, it is -0.8% / ℃. The linear correlation coefficient (R0) for each range is... 2 The values ​​were 99%, 98.9%, and 96.8% respectively, indicating that the sensor has good temperature response linearity and sensitivity over a wide temperature range.

[0061] Figure 9Figure (b) shows the sensor's temperature response curves in the range of 25~80℃ with a gradient of 5℃. The sensor can output stable and repeatable electrical signals between each temperature step without significant hysteresis, demonstrating excellent temperature response stability.

[0062] Figure 9 (c) and Figure 9 (d) in the figure represents the real-time monitoring results of the sensor on the simulated human body temperature changes on the heating platform. The sensor can accurately capture minute temperature changes and output a stable current signal response, verifying its practicality in human health monitoring scenarios.

[0063] The above results indicate that the eutectic gel temperature sensor prepared by this invention has high sensitivity, wide temperature range response and good stability, and has broad application prospects in wearable health monitoring, intelligent temperature control devices and other fields.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-mechanical-strength eutectic gel based on polyethyleneimine, characterized in that, Includes the following steps: S1. Choline chloride and acrylic acid are mixed and stirred evenly to prepare a choline chloride-acrylic acid deep eutectic solvent; choline chloride and glycerol are mixed and stirred evenly to prepare a choline chloride-glycerol deep eutectic solvent. S2. Polyethyleneimine is added to the choline chloride-glycerol deep eutectic solvent and stirred to obtain a homogeneous mixed solution; then the choline chloride-acrylic acid deep eutectic solvent is added and stirred to mix evenly; then glycerol methacrylate is added and stirred to mix evenly; finally, crosslinking agent and photoinitiator are added and stirred until completely dissolved to obtain a precursor solution; S3. Immediately subject the precursor solution obtained in step S2 to ultrasonic degassing treatment, then inject it into a polytetrafluoroethylene mold and cure it by ultraviolet light to form a gel. S4. Place the gel obtained in step S3 in an oven for constant temperature reaction, and demold it after natural cooling to obtain a high mechanical strength eutectic gel based on polyethyleneimine.

2. The method for preparing a high-mechanical-strength eutectic gel based on polyethyleneimine according to claim 1, characterized in that, In step S1, the molar ratio of choline chloride to acrylic acid and choline chloride to glycerol is 1:2, the stirring temperature is 60~80℃, and the stirring time is 1~2h.

3. The method for preparing a high mechanical strength eutectic gel based on polyethyleneimine according to claim 1, characterized in that, In step S2, the mass ratio of polyethyleneimine, choline chloride-glycerol deep eutectic solvent, choline chloride-acrylic acid deep eutectic solvent, glyceryl methacrylate, crosslinking agent, and photoinitiator is 0.1~0.5g:4g:6g:0.05~0.25g:0.05g:0.03g.

4. The method for preparing a high mechanical strength eutectic gel based on polyethyleneimine according to claim 1, characterized in that, In step S2, the crosslinking agent is polyethylene glycol diacrylate, and the photoinitiator is photoinitiator I2959.

5. The method for preparing a high-mechanical-strength eutectic gel based on polyethyleneimine according to claim 1, characterized in that, In step S3, the ultrasonic degassing treatment time is 5~10 minutes.

6. The method for preparing a high mechanical strength eutectic gel based on polyethyleneimine according to claim 1, characterized in that, In step S3, the wavelength of the ultraviolet lamp used for curing is 365nm, and the curing time is 5min.

7. The method for preparing a high mechanical strength eutectic gel based on polyethyleneimine according to claim 1, characterized in that, In step S4, the reaction temperature of the isothermal reaction is 100°C and the reaction time is 2 hours.

8. A high mechanical strength eutectic gel based on polyethyleneimine, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. An application of the high mechanical strength eutectic gel based on polyethyleneimine according to claim 8, characterized in that, The eutectic gel is used to prepare flexible strain sensors or temperature-type flexible sensors.

10. The application according to claim 9, characterized in that: The flexible strain sensor utilizes the change in ion conductivity path during the tensile deformation of the eutectic gel to output a corresponding resistance change signal, thereby realizing flexible deformation signal detection; the temperature-type flexible sensor utilizes the characteristic of the change in ion conductivity inside the eutectic gel with temperature to output a corresponding resistance change signal, thereby realizing temperature detection.

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