Ionic conductive elastomer, preparation method thereof and flexible strain sensor

Abstract

The invention discloses an ionic conductive elastomer, a preparation method thereof and a flexible strain sensor, and belongs to the technical field of flexible sensor materials. The preparation method of the ionic conductive elastomer comprises the following steps: taking a monomer, an auxiliary agent, a cross-linking agent and an electrolyte to prepare a precursor solution; irradiating the precursor solution with ultraviolet light to obtain an ionic conductive elastomer; wherein the monomer is any one of n-alkyl acrylate of which the carbon chain length is C2 to C12, the auxiliary agent is isobornyl acrylate, and the cross-linking agent is tricyclic [5.2. 1.02, 6] decane-1, 5-dimethanol diacrylate. According to the present invention, the specific monomer, the auxiliary agent, the cross-linking agent and the ultraviolet light curing process are adopted to prepare the ionic conductive elastomer with excellent elastic response, such that the energy dissipation is effectively reduced so as to inhibit the retardation effect, and the advantages of effective retardation effect inhibition and improvement of the signal accuracy and the measurement stability of the flexible strain sensor are provided.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor materials technology, and in particular to an ion-conductive elastomer, its preparation method, and a flexible strain sensor. Background Technology

[0002] Flexible strain sensors, with their excellent stretchability, surface adhesion, and high sensitivity, have shown great application potential in cutting-edge fields such as wearable electronic devices, soft robotic systems, and medical health monitoring. These sensors can effectively adapt to dynamically deformable surfaces, such as human skin or flexible robotic joints. Against the backdrop of rapid development in IoT and AI technologies, the demand for real-time, high-precision physiological signal monitoring continues to increase. In specific applications, flexible strain sensors can continuously track physiological parameters such as joint movement, respiratory rate, and pulse waves, providing crucial data support for intelligent prosthetic tactile simulation and chronic disease management (such as tremor monitoring in Parkinson's disease), significantly expanding the sensor's applicability in complex curved surfaces and dynamic environments.

[0003] However, most current mainstream flexible strain sensors are based on viscoelastic material systems, including conductive polymer composites, liquid metals, or carbon-based fillers. During dynamic strain cycling, the viscoelastic properties of these materials lead to internal energy dissipation, resulting in a significant hysteresis effect. This effect manifests as the material's stress response failing to keep pace with changes in external strain in real time, causing phase delay and nonlinear deviation between the sensor's output signal and the actual strain. In practical applications, when the sensor undergoes loading and unloading processes, the signal output at the same strain level is inconsistent, severely weakening the signal-to-noise ratio, measurement stability, and long-term reliability. Especially in high-frequency dynamic scenarios, such as monitoring rapid joint movements or detecting mechanical vibrations, the signal distortion caused by hysteresis is even more pronounced, greatly limiting the sensor's practical value in precision measurement.

[0004] Existing technologies have proposed various improvement schemes to address the hysteresis problem. A common strategy is to enhance the elastic response ratio of materials through surface functionalization of nanofillers (such as carbon nanotubes or silver nanowires). However, since the intrinsic viscoelasticity of the matrix material is difficult to eliminate, the hysteresis effect cannot be fundamentally improved. Another approach employs microfluidic structure design, utilizing conductive fluids to reduce energy dissipation during stretching. However, such schemes involve complex microchannel fabrication processes, are prone to interfacial slippage, and have limited adaptability to high-frequency dynamic loads. Although the above technologies can alleviate the hysteresis phenomenon in a localized area, they are often accompanied by negative issues such as decreased sensitivity or reduced mechanical durability, failing to achieve effective control of hysteresis behavior at the material level. Therefore, developing a novel material system that significantly suppresses the hysteresis effect while maintaining high sensitivity has become a core challenge in the development of flexible sensor technology.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an ion-conductive elastomer, the ion-conductive elastomer, and a flexible strain sensor, which can effectively suppress hysteresis effects and improve the signal accuracy and measurement stability of the flexible strain sensor.

[0007] To achieve the above objectives, the present invention provides an ion-conductive elastomer, a method for preparing the same, and a flexible strain sensor.

[0008] In a first aspect, the present invention provides a method for preparing an ion-conducting elastomer, comprising the following steps:

[0009] S1: Prepare a precursor solution by taking monomers, auxiliaries, crosslinking agents, and electrolytes;

[0010] S2: Ultraviolet light is used to irradiate the precursor solution to obtain an ion-conducting elastomer;

[0011] Among them, the monomers are carbon chains with a length of C2 to C3. 12 The alkyl acrylate is any one of the following, the additive is isobornyl acrylate, and the crosslinking agent is tricyclic [5.2.1.0]. 2,6 Decane-1,5-diethanol diacrylate.

[0012] In one embodiment of the present invention, the electrolyte is lithium bis(trifluoromethanesulfonylimide).

[0013] In one embodiment of the present invention, the molar ratio of monomer to auxiliary is 10:2 to 11:1.

[0014] In one embodiment of the present invention, the ratio of the mass of the electrolyte to the sum of the masses of the monomer and the auxiliaries is 0.83 to 1.

[0015] In one embodiment of the present invention, the molar amount of the crosslinking agent accounts for 1% to 2% of the sum of the molar amounts of the monomer and the auxiliary agent.

[0016] In one embodiment of the present invention, S1 further includes: preparing a precursor solution for the photoinitiator.

[0017] In one embodiment of the present invention, the photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

[0018] In one embodiment of the present invention, S2 further includes: injecting the precursor liquid into a glass mold covered with a polytetrafluoroethylene film and separated by a polydimethylsiloxane sheet, and irradiating the precursor liquid with ultraviolet light.

[0019] Secondly, the present invention provides an ion-conducting elastomer, which is manufactured using the preparation method of an ion-conducting elastomer as described above.

[0020] Thirdly, the present invention provides a flexible strain sensor, comprising a copper wire and an ion-conducting elastomer as described above, wherein the ion-conducting elastomer is provided with a junction electrode region, and the copper wire is connected to the junction electrode region by silver paste.

[0021] Compared with the prior art, according to the present invention, an ion-conductive elastomer, its preparation method, and a flexible strain sensor, the monomer selected has a carbon chain length of C2 to C3. 12 Alkyl acrylates are medium- to short-chain aliphatic acrylates. The polymerized side chains are relatively short aliphatic chains. On the one hand, the interaction between side chains composed only of carbon and hydrogen is weak; on the other hand, the appropriate side chain length weakens the interaction of the main chain, contributing to low hysteresis performance. The choice of crosslinking agent plays a significant role in achieving low hysteresis. Appropriate crosslinking of molecular chains to form a polymer network can enhance its elasticity and reduce energy dissipation caused by molecular chain untangling. Tricyclic [5.2.1.0] was selected. 2,6 Decane-1,5-diethanol diacrylate was used as a crosslinking agent. Due to its unique tricyclic structure, the crosslinking agent possessed a large free volume, optimizing the structure of the polymer network and significantly reducing the polymer's hysteresis. However, the increased degree of crosslinking would increase the material's modulus and decrease its stretchability. Therefore, an additive was added, specifically isobornyl acrylate. The large cyclic side chains of isobornyl acrylate, when added to the polymer network, can enhance the molecular chain mobility and optimize the material's stretchability. Adding a small amount of isobornyl acrylate achieved both low hysteresis and high stretchability. The electrolyte ionizes within the polymer network, functionalizing the elastomer with conductivity. Through the synergistic effect of the components, a solvent-free solid ion-conductive elastomer with low hysteresis and high stretchability was obtained. By employing specific monomers, additives, crosslinking agents, and UV curing processes, an ion-conductive elastomer with excellent elastic response was prepared, effectively reducing energy dissipation and thus suppressing the hysteresis effect. This method has the advantages of effectively suppressing the hysteresis effect and improving the signal accuracy and measurement stability of flexible strain sensors. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for preparing an ion-conducting elastomer according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the chemical structure of ethyl acrylate according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the chemical structure of isobornyl acrylate according to an embodiment of the present invention.

[0025] Figure 4 This is a three-ring [5.2.1.0] according to an embodiment of the present invention. 2,6 A schematic diagram of the chemical structure of decane-1,5-diethanol diacrylate;

[0026] Figure 5 This is a schematic diagram of the chemical structure of lithium bis(trifluoromethanesulfonylimide) according to an embodiment of the present invention.

[0027] Figure 6 This is a schematic diagram of the chemical structure of ethyl 2,4,6-trimethylbenzoylphenylphosphonate according to an embodiment of the present invention.

[0028] Figure 7 This is a hysteresis performance curve of ion-conducting elastomers prepared with acrylate monomers of different aliphatic chain lengths according to Examples 1 to 5 of the present invention.

[0029] Figure 8 This is a hysteresis index curve of the ion-conducting elastomer obtained according to Example 2 and Comparative Examples 1 to 3 of the present invention.

[0030] Figure 9 This is a histogram of the hysteresis index of the ion-conducting elastomers obtained according to Examples 2, 6 and Comparative Examples 4 to 8 of the present invention.

[0031] Figure 10 These are fracture strain histograms of ion-conducting elastomers obtained according to Embodiments 2, 6 and Comparative Examples 4 to 8 of the present invention.

[0032] Figure 11 This is a conductivity curve of the ion-conducting elastomer obtained according to Examples 2, 6 and Comparative Examples 4 to 8 of the present invention.

[0033] Figure 12 This is a histogram of the hysteresis index of the ion-conducting elastomers obtained according to Examples 2, 7 and Comparative Examples 9 to 11 of the present invention.

[0034] Figure 13 This is a fracture strain histogram of the ion-conducting elastomer obtained according to Embodiments 2, 7 and Comparative Examples 9 to 11 of the present invention.

[0035] Figure 14 This is a glass transition temperature curve of the ion-conducting elastomers obtained according to Examples 2, 7 and Comparative Examples 9 to 11 of the present invention.

[0036] Figure 15 This is a stress-strain curve of the ion-conducting elastomer obtained according to Embodiment 2 of the present invention;

[0037] Figure 16 This is a stress-strain curve of a commercially available material elastomer according to an embodiment of the present invention.

[0038] Figure 17 This is a stress-strain curve of the ion-conducting elastomer obtained according to Embodiment 2 of the present invention;

[0039] Figure 18 This is a broadband dielectric spectrum of the ion-conducting elastomer obtained according to Example 2 of the present invention;

[0040] Figure 19 This is a linear graph showing the change rate of resistance of a flexible strain sensor prepared from an ion-conductive elastomer obtained according to Example 2 of the present invention as a function of strain.

[0041] Figure 20 This is a linear graph showing the resistance change rate as a function of strain during the comparative loading and unloading processes of a flexible strain sensor prepared from an ion-conductive elastomer obtained in Embodiment 2 of the present invention. Detailed Implementation

[0042] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0043] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0044] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing an ion-conducting elastomer, comprising the following steps:

[0045] S1: Prepare a precursor solution by taking monomers, auxiliaries, crosslinking agents, and electrolytes;

[0046] S2: Ultraviolet light is used to irradiate the precursor solution to obtain an ion-conducting elastomer;

[0047] Among them, the monomers are carbon chains with a length of C2 to C3. 12 The alkyl acrylate is any one of the following, the additive is isobornyl acrylate, and the crosslinking agent is tricyclic [5.2.1.0]. 2,6 Decane-1,5-diethanol diacrylate.

[0048] Specifically, a monomer refers to a compound capable of forming a high molecular weight polymer through a polymerization reaction. In this application, the monomer is selected as having a carbon chain length of C2 to C3. 12 Any one of the n-alkyl acrylates, which serves as the main building block of the polymer backbone, determines the basic flexibility of the elastomer and the interactions between molecular chains. The chemical structural formula of ethyl acrylate with a carbon chain length of C2 is shown below. Figure 2 As shown.

[0049] Additives refer to auxiliary components added during the polymerization process to adjust the properties of the polymer. In this application, the additive is isobornyl acrylate, with the chemical structural formula as shown below. Figure 3 As shown, it affects the mechanical properties of elastomers, such as stiffness and elastic recovery, by introducing specific molecular structures.

[0050] Crosslinking agents are compounds that enable the formation of chemical bonds between polymer molecular chains, thereby constructing a three-dimensional network structure. In this application, the crosslinking agent is a tricyclic [5.2.1.0] 2,6 Decane-1,5-diethanol diacrylate, chemical structural formula as follows Figure 4 As shown, its function is to form a stable cross-linked network to suppress the slippage and viscous response of polymer chains, thereby affecting the overall elasticity and hysteresis properties of the elastomer.

[0051] Electrolytes are substances that can ionize and conduct electricity in a specific medium. In this application, an electrolyte is added to a precursor solution to impart the necessary ionic conductivity to the final ion-conducting elastomer, ensuring its signal transmission function when used as a sensor material.

[0052] A precursor solution is a liquid mixture composed of monomers, auxiliaries, crosslinking agents, electrolytes, and other components, prepared before the polymerization reaction. This precursor solution is the starting material for preparing ion-conducting elastomers, and its component ratios and homogeneity have a decisive influence on the properties of the final product. The preparation of the precursor solution typically involves mixing the aforementioned components uniformly according to a predetermined ratio. For example, this can be achieved by magnetic stirring or mechanical stirring at room temperature or under appropriate heating conditions until a clear and homogeneous solution is formed. The thoroughness of the mixing process affects the uniformity of the subsequent polymerization reaction and the properties of the final elastomer.

[0053] Ion-conducting elastomers are polymer materials that possess both elastic deformation capability and ion-conducting properties. The ion-conducting elastomer obtained in this application through a specific preparation method aims to combine low hysteresis, high elasticity, and conductivity, making it suitable for flexible strain sensors.

[0054] Ultraviolet (UV) irradiation refers to the process of irradiating a precursor solution with ultraviolet light of a specific wavelength to initiate a photopolymerization reaction. This process enables rapid curing and efficiently forms a uniformly cross-linked polymer network, avoiding the structural inhomogeneity that may result from traditional thermosetting. UV irradiation is a highly efficient curing method. For example, mercury lamps, LED UV light sources, and other equipment can be used to irradiate the precursor solution. The wavelength, intensity, and duration of the UV light can all be adjusted according to the specific formulation and the desired degree of curing. Through the polymerization reaction initiated by UV light, a cross-linked network can be rapidly formed, thereby obtaining an ion-conductive elastomer in a short time.

[0055] In this embodiment, the hysteresis of the polymer material mainly originates from the energy dissipation generated during the stretching and release processes due to the interactions between molecular chains. In this embodiment, the carbon chain length of the monomer selected is C2 to C3. 12 Alkyl acrylates are medium- to short-chain aliphatic acrylates. The polymerized side chains are relatively short aliphatic chains. On the one hand, the interaction between side chains composed only of carbon and hydrogen is weak; on the other hand, the appropriate side chain length weakens the interaction of the main chain, contributing to low hysteresis performance. The choice of crosslinking agent plays a significant role in achieving low hysteresis. Appropriate crosslinking of molecular chains to form a polymer network can enhance its elasticity and reduce energy dissipation caused by molecular chain untangling. Tricyclic [5.2.1.0] was selected. 2,6 Decane-1,5-diethanol diacrylate is used as a crosslinking agent. Due to its unique tricyclic structure, the crosslinking agent has a large free volume, which optimizes the structure of the polymer network and significantly reduces the polymer's hysteresis. However, the increase in crosslinking degree will increase the material's modulus and reduce its stretchability. Therefore, an additive is added. The additive chosen isobornyl acrylate. The large cyclic side chains of isobornyl acrylate can enhance the molecular chain mobility and optimize the material's stretchability when added to the polymer network. The addition of a small amount of isobornyl acrylate achieves low hysteresis and high stretchability of the material. The electrolyte ionizes in the polymer network, giving the elastomer ionic conductivity and functionalizing it for conductivity. Through the synergistic effect of the components, a solvent-free solid ionic conductive elastomer with low hysteresis and high stretchability is obtained.

[0056] By employing specific monomers, additives, crosslinking agents, and ultraviolet curing processes, an ion-conductive elastomer with excellent elastic response is prepared, effectively reducing energy dissipation and thus suppressing hysteresis. This has the advantages of effectively suppressing hysteresis and improving the signal accuracy and measurement stability of flexible strain sensors.

[0057] In one embodiment of the present invention, the electrolyte is lithium bis(trifluoromethanesulfonylimide).

[0058] Specifically, the electrolyte is lithium bis(trifluoromethanesulfonylimide), with the chemical structure as follows: Figure 5As shown, the electrolyte is solid under normal conditions, and ionization occurs within the polymer network due to solvation. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is a high-performance lithium salt electrolyte that plays a crucial role in ion-conducting elastomers. Specifically, LiTFSI exhibits excellent chemical and thermal stability, ensuring the long-term reliability of ion-conducting elastomers under various environmental conditions. Its anion (bis(trifluoromethanesulfonyl) ion) has a large volume and weak coordination with lithium ions, which facilitates the dissociation of lithium ions and their rapid migration within the polymer matrix, thereby significantly improving the ionic conductivity of the electrolyte. Furthermore, LiTFSI exhibits good solubility in the selected monomer and additive systems, contributing to the formation of a uniform and efficient ion-conducting network. Compared to other common lithium salts, LiTFSI is less prone to hydrolysis and has lower corrosiveness to the polymer matrix, further enhancing the stability and safety of the material. In terms of viscoelasticity, the introduction of LiTFSI can effectively reduce the glass transition temperature of polymer segments, increase the free volume and mobility of segments, thereby reducing energy dissipation of materials under strain and thus reducing hysteresis.

[0059] In this embodiment, the electrolyte is limited to lithium bis(trifluoromethanesulfonyl)imide, effectively solving the problem of significant hysteresis effects that may occur in materials under dynamic loads if the electrolyte type is not specified. Lithium bis(trifluoromethanesulfonyl)imide, as a high-performance lithium salt, possesses a unique ionic structure and excellent solubility, enabling it to form efficient ion transport channels in the polymer matrix while significantly reducing the viscoelastic dissipation of the polymer chains. This ensures that the ion-conductive elastomer can respond to external deformation more quickly and accurately during strain loading and unloading, thereby greatly improving the signal consistency and reliability of the flexible strain sensor. Especially under dynamic cyclic strain scenarios, it can provide more stable and accurate sensing signals, avoiding signal distortion and nonlinear deviations caused by hysteresis effects.

[0060] In one embodiment of the present invention, the molar ratio of monomer to auxiliary is 10:2 to 11:1.

[0061] Specifically, this molar ratio defines the relative amounts of monomers and additives used in the preparation of the precursor solution. The monomers are those with a carbon chain length of C2 to C3. 12Any of the n-alkyl acrylates used, whose main function is to provide flexibility and stretchability of the polymer chain, such as butyl acrylate or octyl acrylate, can be selected. The additive is isobornyl acrylate, whose main function is to introduce a rigid structure, enhance crosslinking density, and improve the structural stability of the material. Controlling the molar ratio of monomer to additive within the range of 10:2 to 11:1 aims to precisely regulate the proportion of reactive components in the precursor solution, thereby affecting the degree of polymerization, crosslinking network structure, and macroscopic mechanical properties of the final ion-conductive elastomer. For example, at a molar ratio of 10:2, the relatively high content of the additive may lead to a relatively high crosslinking density and increased material hardness, while still maintaining a certain degree of elasticity; at a molar ratio of 11:1, the relatively high content of the monomer may make the material more flexible while maintaining sufficient structural strength. By precisely controlling this ratio, the viscoelastic balance of the material can be optimized, enabling it to maintain flexibility while possessing good elastic recovery ability.

[0062] In this embodiment, by precisely limiting the molar ratio of monomers and auxiliaries to the range of 10:2 to 11:1, this application can effectively control the structure and crosslinking density of the polymer network inside the ion-conductive elastomer. At this specific ratio, the carbon chain length, which serves as the source of the flexible segments, is C2 to C4. 12 An optimized balance was achieved between the alkyl acrylate monomer and the isobornyl acrylate additive, which serves as a rigid structural reinforcing agent. This balance allows the prepared ion-conductive elastomer to maintain necessary flexibility while significantly reducing the material's viscoelasticity, thereby minimizing internal energy dissipation under dynamic loads. Specifically, this optimized molar ratio avoids insufficient crosslinking and excessive viscosity due to too little additive, or excessive hardness and insufficient elasticity due to too much additive. By precisely controlling the relative content of monomer and additive, a polymer network with moderate crosslinking and good elasticity can be formed, enabling the material to respond and recover quickly under external strain, effectively suppressing the hysteresis effect commonly found in traditional flexible strain sensors. Therefore, the ion-conductive elastomer prepared using this molar ratio can significantly improve the signal stability, response speed, and measurement accuracy of flexible strain sensors, especially in dynamic cyclic strain scenarios, providing more reliable sensing data and overcoming the hysteresis problem caused by high viscoelasticity in existing technologies.

[0063] In one embodiment of the present invention, the ratio of the mass of the electrolyte to the sum of the masses of the monomer and the auxiliaries is 0.83 to 1.

[0064] Specifically, this ratio defines the relative content of key components—electrolytes and polymer matrix precursors (monomers and additives)—in the preparation of ion-conductive elastomers. The electrolyte is the core component providing ion conductivity, and its content directly affects the electrical properties of the material. Monomers (carbon chain length from C2 to C4)12 The electrolyte (any one of the n-alkyl acrylates) and the additive (isobornyl acrylate) together form the polymer skeleton of the elastomer, giving the material mechanical strength and elasticity. This ratio is designed to achieve a delicate balance between ionic conductivity and mechanical properties. For example, when preparing a precursor solution, the mass ratio can be ensured to fall within the range of 0.83 to 1 by accurately weighing the electrolyte, monomer, and additive, and performing calculations. Alternatively, after determining the total mass of the monomer and additive, the required mass of the electrolyte can be deduced from the target ratio, thus precisely controlling the formulation.

[0065] In this embodiment, the ratio of the electrolyte mass to the sum of the monomer and additive masses is precisely controlled within the range of 0.83 to 1. This optimized ratio ensures that the electrolyte provides efficient ion transport capabilities without excessively softening the polymer matrix or introducing excessively high viscous resistance. Specifically, when the ratio is within this range, the molecular chains within the ion-conductive elastomer can respond more rapidly and completely to external strain, reducing internal friction and energy dissipation caused by improper electrolyte content. This effectively suppresses hysteresis in the material during dynamic load loading / unloading, significantly improving the consistency and stability of the flexible strain sensor's output signal. Therefore, the ion-conductive elastomer prepared in this application can provide more accurate and reliable signal feedback for flexible strain sensors, and is particularly suitable for applications requiring high-precision dynamic monitoring.

[0066] In one embodiment of the present invention, the molar amount of the crosslinking agent accounts for 1% to 2% of the sum of the molar amounts of the monomer and the auxiliary agent.

[0067] Specifically, the molar amount of the crosslinking agent is 1% to 2% of the sum of the molar amounts of the monomer and the auxiliaries. This refers to precisely controlling the amount of crosslinking agent added during the preparation of the precursor solution to maintain it within this specific ratio range relative to the total molar amount of the monomer and the auxiliaries. Determining this ratio aims to optimize the crosslinking density of the polymer network. Methods to achieve this ratio may include: one approach is to determine the crosslinking density based on the selected monomer (carbon chain length C2 to C4). 12 Any one of the n-alkyl acrylates), additives (isobornyl acrylate), and crosslinking agents (tricyclic [5.2.1.0]). 2,6 The molecular weight of decane-1,5-diethanol diacrylate is determined by accurately weighing each component and calculating and adjusting it to the required molar ratio. Alternatively, if each component exists in solution form, its volume is calculated and measured based on its known concentration and molecular weight to ensure that the molar ratio of each component in the final mixture meets the requirements.

[0068] This embodiment effectively addresses the hysteresis problem that may occur in ion-conductive elastomers under dynamic loads. The specific ratio ensures the formation of a moderate and uniform cross-linked network structure during ultraviolet irradiation. When the molar amount of the cross-linking agent is less than 1%, insufficient cross-linking leads to a loose polymer network with high chain segment mobility, increasing the material's viscoelasticity and resulting in increased energy dissipation and significant hysteresis during strain loading / unloading. Conversely, when the molar amount of the cross-linking agent is greater than 2%, excessive cross-linking makes the polymer network too dense and rigid, increasing material brittleness and decreasing flexibility and durability. Excessive internal stress may also cause the material to exhibit undesirable responses during dynamic deformation, even affecting its applicability as a flexible strain sensor. Therefore, precisely controlling the molar amount of the cross-linking agent within the range of 1% to 2% of the sum of the monomer and additive molar amounts achieves an optimal balance between cross-linking density and flexibility. This optimized cross-linked network structure significantly reduces the viscoelastic contribution of the material, enabling the ion-conductive elastomer to respond quickly under external strain, reducing the phase delay and nonlinear deviation between the signal output and the actual strain, thereby effectively reducing hysteresis. This plays a crucial role in improving the dynamic response performance, signal stability, and long-term reliability of flexible strain sensors, enabling them to exhibit superior performance in applications requiring high-precision dynamic monitoring.

[0069] In one embodiment of the present invention, S1 further includes: preparing a precursor solution for the photoinitiator.

[0070] Specifically, a photoinitiator is a substance that absorbs light energy and generates reactive intermediates (such as free radicals or cations) under illumination of specific wavelengths of light. These reactive intermediates can initiate the polymerization reaction of monomers and crosslinking agents. Its main function is to improve the utilization efficiency of ultraviolet light energy, ensuring that the polymerization reaction can be started and carried out quickly and effectively. In practical applications, free radical photoinitiators can be selected, such as ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, benzophenone, etc. Alternatively, cationic photoinitiators, such as iodonium salts or thionium salts, can also be used, but the selection must be based on the specific monomer system.

[0071] The preparation of the precursor solution aims to uniformly disperse or dissolve the photoinitiator in the precursor solution, ensuring that the polymerization reaction can occur synchronously and efficiently throughout the system during subsequent ultraviolet irradiation. This preparation process can be carried out by mechanical stirring, such as using a magnetic stirrer or electric stirrer, stirring for a preset time at a specific temperature and speed to achieve uniform mixing. Alternatively, ultrasonic dispersion can be used, utilizing the cavitation effect and mechanical vibration of ultrasound to promote the dispersion of the photoinitiator in the liquid, which is particularly suitable for photoinitiators with poor solubility.

[0072] In this embodiment, a photoinitiator is introduced into the precursor solution in step S1, effectively solving the problems of low initiation efficiency and incomplete reaction that may occur when the precursor solution is irradiated with ultraviolet light. The photoinitiator can efficiently absorb ultraviolet light energy and rapidly generate active free radicals, thereby quickly initiating the polymerization reaction of monomers and crosslinking agents. This not only significantly improves the polymerization rate and conversion rate, ensuring the full curing and formation of the ion-conductive elastomer, but also avoids material performance defects caused by incomplete reaction. This ensures that the prepared ion-conductive elastomer has superior mechanical and ion conductivity properties, providing a high-quality elastomer substrate for the subsequent fabrication of flexible strain sensors.

[0073] In one embodiment of the present invention, the photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

[0074] Specifically, photoinitiators are key components in polymerization reactions. Their role is to absorb light energy of specific wavelengths, which then decomposes to generate free radicals. These free radicals can initiate the polymerization reaction of monomers, auxiliaries, and crosslinking agents, thereby forming a polymer network. In this application, the photoinitiator is specifically ethyl 2,4,6-trimethylbenzoylphenylphosphonate, with the chemical structural formula shown below. Figure 6 As shown, this compound belongs to the acylphosphine oxide class of photoinitiators, renowned for its highly efficient photosensitivity and excellent initiation efficiency. Under ultraviolet light irradiation, ethyl 2,4,6-trimethylbenzoylphenylphosphonate rapidly cleaves, generating highly reactive free radicals. These free radicals can quickly and uniformly initiate the polymerization reaction in the precursor solution, ensuring the thoroughness and uniformity of the polymerization process. Compared to other types of photoinitiators, ethyl 2,4,6-trimethylbenzoylphenylphosphonate provides rapid curing even at lower addition levels and exhibits good deep curing ability, contributing to the formation of ion-conductive elastomers with uniform structure and few internal defects.

[0075] In this embodiment, by using ethyl 2,4,6-trimethylbenzoylphenylphosphonate as a photoinitiator, this application effectively solves the problems of insufficient photoinitiation efficiency, slow reaction rate, or excessive byproduct formation. Specifically, the highly efficient photosensitivity of ethyl 2,4,6-trimethylbenzoylphenylphosphonate ensures that free radicals can be generated rapidly and uniformly under ultraviolet light irradiation, thereby efficiently initiating the polymerization reaction of monomers, auxiliaries, and crosslinking agents. This allows the polymerization reaction to proceed fully, avoiding material defects such as structural inhomogeneity or unstable mechanical properties caused by uneven reaction rates or incomplete polymerization. Ultimately, the prepared ion-conductive elastomer has superior formation quality, uniform structure, and stable mechanical properties. Given that the uniformity and mechanical stability of ion-conductive elastomers are key factors affecting the hysteresis phenomenon of flexible strain sensors, by optimizing the photoinitiator, this application can significantly reduce the hysteresis effect of flexible strain sensors during dynamic load loading / unloading processes, improve the signal-to-noise ratio, stability, and reliability of the sensor, thereby expanding its application in precision measurement scenarios.

[0076] In one embodiment of the present invention, S2 further includes: injecting the precursor liquid into a glass mold covered with a polytetrafluoroethylene film and separated by a polydimethylsiloxane sheet, and irradiating the precursor liquid with ultraviolet light.

[0077] Specifically, the glass mold, serving as the container for the curing reaction, provides a stable and precisely shaped support structure. Its transparency allows for uniform UV light penetration, ensuring complete polymerization of the precursor liquid. Besides glass, other materials with good UV transmittance, dimensional stability, and chemical inertness can be used to prepare the mold, such as quartz molds or certain transparent polymer molds. Polytetrafluoroethylene (PTFE) film possesses excellent non-adhesive and low surface energy properties, effectively preventing the precursor liquid from adhering to the mold surface during curing, thus facilitating elastomer demolding and ensuring a smooth, defect-free elastomer surface. In addition to PTFE film, other materials with similar non-adhesive properties can be used, such as fluorinated ethylene propylene (FEP) film, perfluoroalkoxy (PFA) film, or specially surface-treated silicone film. Polydimethylsiloxane (PDMS) sheets, acting as an isolation layer, not only allow for precise control of the elastomer thickness, but their inherent flexibility also buffers potential internal stresses during polymerization, preventing stress concentration that could degrade elastomer performance. Simultaneously, their chemical inertness ensures no adverse reactions with the precursor liquid. Besides polydimethylsiloxane sheets, other materials with good flexibility, chemical inertness, and precise thickness control can be used, such as other types of silicone rubber sheets, polyurethane sheets, or certain elastomer composite sheets. Ultraviolet (UV) irradiation is a key step in initiating the monomer polymerization reaction in the precursor liquid. Through the action of a photoinitiator, the liquid precursor liquid rapidly solidifies to form an ion-conducting elastomer. UV irradiation within the aforementioned mold structure ensures uniform illumination and controllable curing process. UV irradiation can be achieved using various light sources, such as high-pressure mercury lamps, LED UV lamps, or xenon lamps. The wavelength and intensity can be adjusted according to the absorption spectrum of the selected photoinitiator to optimize curing efficiency and elastomer properties.

[0078] In this embodiment, the precursor liquid is injected into a glass mold coated with a polytetrafluoroethylene (PTFE) film and separated by a polydimethylsiloxane (PDMS) sheet, and then irradiated with ultraviolet light. This effectively solves the problems of adhesion and uneven curing that may occur during the curing process of the precursor liquid. Specifically, the glass mold provides a stable and rigid support environment, ensuring the macroscopic shape and dimensional accuracy of the elastomer. The PTFE film, with its excellent non-adhesive properties, prevents the precursor liquid from sticking to the mold, making the cured elastomer easy to demold and obtaining a smooth, defect-free surface, thereby reducing stress concentration and hysteresis effects caused by surface roughness. The PMS sheet precisely controls the thickness of the elastomer and uses its flexibility to buffer the internal stress that may be generated during polymerization, avoiding stress concentration and further improving the uniformity and mechanical integrity of the elastomer. These measures work synergistically to ensure efficient and uniform curing of the ion-conductive elastomer during the preparation process, significantly improving the surface quality and internal structural uniformity of the elastomer, thereby effectively reducing its hysteresis rate in flexible strain sensor applications and improving the signal stability and reliability of the sensor.

[0079] Another embodiment of the present invention provides an ion-conducting elastomer, which is prepared by the method for preparing ion-conducting elastomers as described above.

[0080] Specifically, ion-conducting elastomers are materials that combine high elasticity, stretchability, and excellent ion conductivity. They typically consist of a polymer matrix and ion-conducting components. The polymer matrix provides mechanical support and elasticity, while the ion-conducting components impart charge transport capabilities to the material. One approach is to uniformly disperse or dissolve ionic liquids or ionic salts within an elastic polymer network, forming ion transport channels. Another approach is to polymerize monomers containing ionic groups, enabling them to possess ion conductivity while simultaneously forming an elastic polymer network.

[0081] Ion-conducting elastomers are prepared using specific methods. This statement emphasizes that their unique properties are not achieved by chance, but rather through a series of precisely controlled preparation steps and the synergistic effect of components. Their core function is to ensure that the prepared elastomer can form a specific microstructure, thereby exhibiting a comprehensive advantage of low hysteresis, high elasticity, and good ionic conductivity on a macroscopic scale. One approach is to precisely control the proportions of each component in the precursor solution and perform in-situ polymerization under specific polymerization conditions, resulting in a uniform polymer network structure with moderate crosslinking. This maintains good elasticity while providing an efficient and stable channel for ion transport. Another approach is to optimize polymerization process parameters, such as the intensity, time, and temperature of ultraviolet irradiation, to ensure the polymerization reaction proceeds fully, forming a stable three-dimensional network structure. This minimizes the free movement of polymer chain segments and viscoelastic dissipation, thereby fundamentally suppressing the hysteresis effect.

[0082] In this embodiment, the ion-conductive elastomer prepared using a specific method, through the synergistic effect of unique component selection and precise polymerization process, effectively constructs a polymer network structure with high uniformity and stability. Specifically, through a combination of specific monomers, additives, and crosslinking agents, and a UV-initiated polymerization process, the polymer chains within the elastomer can form a tight and ordered three-dimensional crosslinked network. This structure significantly reduces the viscoelastic dissipation of the polymer chains under dynamic strain, thereby suppressing hysteresis at the intrinsic material level. When external strain is applied or unloaded, the elastomer can respond rapidly and accurately, maintaining a high degree of synchronization and linearity between the sensor output signal and the actual strain, effectively avoiding the phase delay and nonlinear deviation problems commonly found in traditional flexible strain sensors. Furthermore, while maintaining excellent elasticity, this ion-conductive elastomer also provides a stable ion transport path, ensuring that the sensor's conductivity remains continuous and reliable during deformation. Therefore, this ion-conductive elastomer can significantly improve the signal-to-noise ratio, stability, and reliability of flexible strain sensors, especially in dynamic cyclic strain scenarios, providing more accurate and reliable sensing data, thereby expanding its application potential in precision measurement and real-time monitoring.

[0083] Another embodiment of the present invention provides a flexible strain sensor, including a copper wire and an ion-conducting elastomer as described above. The ion-conducting elastomer is provided with a junction electrode area, and the copper wire is connected to the junction electrode area through silver paste.

[0084] Specifically, copper wire, as the electrical signal transmission medium of the sensor, primarily functions to effectively extract or introduce the electrical signals generated by the ion-conductive elastomer. Copper wire can take various forms; for example, it can be bare copper wire with good conductivity, directly contacting the subsequent conductive material; or it can be enameled wire with an outer insulating layer, requiring the insulation layer at the ends to expose the conductive portion during use. Furthermore, depending on the specific application scenario of the flexible sensor and the requirements for mechanical flexibility, the copper wire can be a single strand to provide higher mechanical strength, or a multi-strand stranded wire to enhance its bending and tensile properties.

[0085] Ion-conducting elastomers are the core sensing materials of flexible strain sensors, and their fabrication method can refer to the method described above. This elastomer, through its internal ion-conducting mechanism, changes its ion channels or ion concentration distribution when subjected to external strain, thereby altering its conductivity and enabling the sensing of strain signals. Its inherent low hysteresis characteristic is key to achieving high-precision and high-stability sensing.

[0086] The electrode contact area is a region on an ion-conductive elastomer specifically designed for electrical connection with an external electrode. This area is designed to provide an optimized and stable connection interface, avoiding poor contact or stress concentration problems that can occur with connections made arbitrarily at any location on the elastomer. Specifically, the electrode contact area can be a region on the elastomer surface that has undergone specific treatment, such as improving surface roughness and adhesion through physical etching, chemical modification, or pre-coating with a conductive layer; or it can be a region with a specific geometry (such as rectangular, circular, or strip-shaped) reserved during the molding process of the elastomer to ensure the precision and consistency of the electrode connection.

[0087] Copper wires are connected to the electrode area via silver paste. Silver paste is a paste-like material containing highly conductive silver particles, which, upon curing, forms a conductive layer with excellent conductivity and good adhesion. Various types of silver paste are available; for example, epoxy resin-based silver paste can be used, which exhibits high mechanical strength and environmental resistance after curing; thermoplastic silver paste can also be used, forming a conductive path through heat curing; or UV-curable silver paste can be used, which cures rapidly through ultraviolet light irradiation, improving production efficiency. Using silver paste for connection ensures extremely low electrical contact resistance between the copper wire and the ion-conductive elastomer, thereby minimizing signal loss and interference during transmission. Simultaneously, the excellent adhesion of the silver paste guarantees the mechanical stability of the connection, ensuring the connection interface remains intact and reliable even under dynamic strain conditions such as repeated bending and stretching of the sensor.

[0088] This embodiment effectively solves the problems of unstable connection between external electrodes and sensing materials, low signal transmission efficiency, and excessively high interface resistance in flexible strain sensors. Specifically, by setting a dedicated electrode area on the ion-conductive elastomer and using silver paste to precisely and firmly connect copper wires to this area, a low-resistance, high-stability electrical connection interface is constructed. The high conductivity of the silver paste ensures that electrical signals can be transmitted efficiently and without loss from the ion-conductive elastomer to the copper wires, avoiding signal attenuation and distortion. At the same time, the excellent adhesion of the silver paste provides a reliable mechanical fixation between the copper wires and the elastomer, effectively preventing connection detachment or poor contact that may occur during the dynamic deformation of the sensor, thereby significantly improving the signal output stability, signal-to-noise ratio, and overall reliability of the sensor. This optimized connection method allows the inherent ultra-low hysteresis and high sensitivity characteristics of the ion-conductive elastomer to be fully utilized, ensuring that the flexible strain sensor can provide accurate and stable strain monitoring data in complex dynamic application scenarios, such as wearable devices or soft robots.

[0089] Example 1, a method for preparing an ion-conducting elastomer, includes the following steps:

[0090] 1. Take 11 mol of monomer methyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate, 1155 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0091] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0092] Example 2, a method for preparing an ion-conducting elastomer, includes the following steps:

[0093] 1. Take 11 mol of monomer ethyl acrylate (EA), 1 mol of auxiliary agent isobornyl acrylate (IBOA), and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 1310 g of electrolyte lithium bis(trifluoromethanesulfonylimide) (LiTFSI), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0094] The ratio of the mass of the electrolyte to the sum of the masses of the monomer and the auxiliaries is 1.

[0095] The molar ratio of the adjuvant to the monomer is 1:11, that is, n(IBOA):n(EA) is 1:11;

[0096] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0097] Example 3, a method for preparing an ion-conducting elastomer, includes the following steps:

[0098] 1. Take 11 mol of monomer n-propyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate, 1464 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0099] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0100] Example 4, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0101] 1. Take 11 mol of monomer n-butyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate, 1618 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0102] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0103] Example 5, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0104] 1. Take 11 mol of the monomer dodecyl acrylate, 1 mol of the auxiliary agent isobornyl acrylate, and 0.12 mol of the crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate, 2852 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0105] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0106] Example 1: The ion-conductive elastomers obtained in Examples 1 to 5 were cut into dumbbell-shaped samples using a Type 4 cutter according to GBT528 standard. Uniaxial tensile tests were performed on the ion-conductive elastomers obtained in Examples 1 to 5 using a multi-functional mechanical testing machine. The tensile strength was 10%... -1 The strain rate was applied at 100% strain and then unloaded. Data was recorded and the stress-strain curve of the sample was calculated. The hysteresis of the material was calculated using the evaluation criteria defined in the scheme, such as... Figure 7As shown in the figure. Experimental results indicate that, except for methyl acrylate, the elastomers synthesized from other medium- and short-chain acrylate monomers all exhibit low hysteresis and can be used as experimental monomers for further research. The side chains of methyl acrylate are too short, and the spacing between the polymer backbones is too small, resulting in strong interactions and thus significant hysteresis.

[0107] Comparative Example 1, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0108] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, 0.12 mol of crosslinking agent polyethylene glycol diacrylate (PEGDA-200) with a molecular weight of 200, 1310 g of electrolyte lithium bis(trifluoromethanesulfonyl)imide, and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and mix thoroughly to obtain a transparent and homogeneous solution, which is the precursor solution;

[0109] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0110] Comparative Example 2, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0111] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, 0.12 mol of crosslinking agent triethylene glycol divinyl ether (TDVE), 1310 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and mix thoroughly to obtain a transparent and homogeneous solution, which is the precursor solution;

[0112] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0113] Comparative Example 3, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0114] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, 0.12 mol of crosslinking agent 1,4-butanediol vinyl ether (BVB), 1310 g of electrolyte lithium bis(trifluoromethanesulfonyl)imide, and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and mix thoroughly to obtain a transparent and homogeneous solution, which is the precursor solution;

[0115] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0116] Example 2: The ion-conducting elastomers obtained in Example 2 and Comparative Examples 1 to 3 were cut into dumbbell-shaped samples using a Type 4 cutter according to GBT528 standard. Uniaxial tensile tests were performed on the ion-conducting elastomers obtained in Example 2 and Comparative Examples 1 to 3 using a multi-functional mechanical testing machine. (The last sentence appears to be incomplete and requires further context.) -1 The strain rate was applied at 100% strain and then unloaded. Data was recorded and the stress-strain curve of the sample was calculated. The hysteresis of the material was calculated using the evaluation criteria defined in the scheme, such as... Figure 8 As shown. Experimental results show that the crosslinking agent tricyclic [5.2.1.0] in Example 2... 2,6 The elastomer synthesized from decane-1,5-diethanol diacrylate (TCDDA) exhibits low hysteresis.

[0117] Example 6, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0118] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 1087 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0119] The ratio of the mass of the electrolyte to the sum of the masses of the monomers and auxiliaries is 0.83.

[0120] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0121] Comparative Example 4, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0122] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6Decane-1,5-dimethylethanol diacrylate (TCDDA), 865 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0123] The ratio of the mass of the electrolyte to the sum of the masses of the monomer and the auxiliaries is 0.66, i.e., m(LiTFSI):m(EA+IBOA) is 0.66.

[0124] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0125] Comparative Example 5, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0126] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 655 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0127] The ratio of the mass of the electrolyte to the sum of the masses of the monomers and auxiliaries is 0.50.

[0128] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0129] Comparative Example 6, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0130] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 432 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0131] The ratio of the mass of the electrolyte to the sum of the masses of the monomers and auxiliaries is 0.33.

[0132] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0133] Comparative Example 7, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0134] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 216 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0135] The ratio of the mass of the electrolyte to the sum of the masses of the monomers and auxiliaries is 0.16.

[0136] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0137] Comparative Example 8, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0138] 1. Take 11 mol of monomer ethyl acrylate, 1 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA) and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0139] In this comparative example, no electrolyte was added;

[0140] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0141] Example 3 compares the changes in material conductivity and fracture strain after adding different amounts of electrolyte. The hysteresis properties of the ion-conducting elastomers obtained in Examples 2, 6, and Comparative Examples 4 to 8 are calculated using the method of Example 1. Figure 9 As shown. The elastomers synthesized in Examples 2 and 6 exhibit low hysteresis.

[0142] The tensile properties of the ion-conducting elastomers obtained in Examples 2, 6, and Comparative Examples 4 to 8 were tested using a mechanical testing machine at 10% s -1 The strain rate was increased until the sample fractured, the data were recorded, and the stress-strain curve was calculated. The maximum elongation of the material was then calculated. Figure 10 As shown. The ion-conductive elastomers obtained in Examples 2, 6, and Comparative Examples 4 to 8 were cut into circles with a diameter of 1 cm using a mold. The conductivity of the materials was measured using a wide-screen dielectric spectrometer. Figure 11 As shown. Figures 9 to 11 It is evident that adding more electrolyte increases the conductivity of the material, maintains a low hysteresis level, but continuously reduces the fracture strain. This is likely because the electrolyte in the precursor solution affects the polymerization process of the material; adding more electrolyte may prevent polymerization. Using an optimal ratio is beneficial for achieving low hysteresis and high conductivity in the material.

[0143] Example 7, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0144] 1. Take 11 mol of monomer ethyl acrylate (EA), 2.2 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 1310 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0145] The molar ratio of the auxiliaries to the monomers is 2:10.

[0146] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0147] Comparative Example 9, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0148] 1. Take 11 mol of monomer ethyl acrylate (EA), 3.67 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6Decane-1,5-dimethylethanol diacrylate (TCDDA), 1310 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0149] The molar ratio of the auxiliaries to the monomers is 3:9;

[0150] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0151] Comparative Example 10, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0152] 1. Take 11 mol of monomer ethyl acrylate (EA), 5.5 mol of auxiliary agent isobornyl acrylate, and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 1310 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0153] The molar ratio of the auxiliaries to the monomers is 4:8;

[0154] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0155] Comparative Example 11, a method for preparing an ion-conducting elastomer, comprising the following steps:

[0156] 1. Take 11 mol of monomer ethyl acrylate (EA) and 0.12 mol of crosslinking agent tricyclo[5.2.1.0]. 2,6 Decane-1,5-dimethylethanol diacrylate (TCDDA), 1310 g of electrolyte lithium bis(trifluoromethanesulfonylimide), and 0.0012 mol of photoinitiator ethyl 2,4,6-trimethylbenzoylphenylphosphonate were thoroughly mixed to obtain a transparent and homogeneous solution, which is the precursor solution.

[0157] In this comparative example, isoborneol acrylate was not added, i.e. Figures 12 to 14 Middle Pure Group;

[0158] 2. The precursor liquid is injected into a glass mold that is covered with a 0.1 mm thick polytetrafluoroethylene film and separated by a 0.3 mm thick polydimethylsiloxane film. The precursor liquid is irradiated with 365 mm ultraviolet light for 10 minutes to obtain an ion-conductive elastomer.

[0159] Example 4 compares the changes in hysteresis and fracture strain of materials after adding different proportions of the additive isobornyl acrylate. The hysteresis properties of the ion-conducting elastomers obtained in Examples 2, 7, and Comparative Examples 9 to 11 were calculated using the method of Example 1. Figure 12 As shown. The fracture strain properties of the ion-conducting elastomers obtained in Examples 2, 7, and Comparative Examples 9 to 11 were calculated using the method of Example 3, as shown. Figure 13 As shown. The glass transition temperatures (Tg) of the ion-conducting elastomers obtained in Examples 2, 7, and Comparative Examples 9 to 11 were measured using differential scanning calorimetry (DSC) to evaluate the molecular chain mobility of the materials. The results are as follows. Figure 14 As shown. From Figures 12 to 14 The experimental results show that with the increase of isobornyl acrylate content, the hysteresis, fracture strain, and glass transition temperature of the material increase. Adding a small amount of isobornyl acrylate as an additive according to the preferred ratio can improve the tensile properties of the material.

[0160] Example 5: The ion-conductive elastomer obtained in Example 2 was subjected to a uniaxial tensile test using a multi-functional mechanical testing machine. Different strains were applied and unloaded at a strain rate of 10% s⁻¹, and the data were recorded and the stress-strain curve of the sample was calculated. Figure 15 As shown, the hysteresis of the ion-conducting elastomer obtained in Example 2 was calculated using the evaluation criteria of Example 1, as shown in Table 1. Several commercially available materials commonly used as flexible substrates were tested and compared using the same method, such as... Figure 16 As shown in Table 2, the hysteresis of the materials was calculated using the evaluation criteria of Example 1. PDMS184 is Dow Corning 184 PDMS, and Ecoflex 00-10, Ecoflex 00-30, and Ecoflex 00-50 were all manufactured by Smooth-On, Inc. It was found that the ion-conductive elastomer prepared in Example 2 had a lower modulus and lower hysteresis.

[0161] Table 1. Material hysteresis of the ion-conducting elastomers obtained in Example 2 under different strains.

[0162] strain hysteresis 50% 1.27% 100% 0.72% 150% 0.73% 200% 0.77%

[0163] Table 2. Material hysteresis of commercial ion-conducting elastomers under different strains

[0164] Material hysteresis PDMS184 16.69% Ecoflex 00-10 27.30% Ecoflex 00-30 6.10% Ecoflex 00-50 15.71%

[0165] The ion-conducting elastomer obtained in Example 2, with 10% s -1 The strain rate was increased until the material fractured. Data were recorded and the stress-strain curve of the sample was calculated, as shown in the figure. Figure 17 As shown, the maximum elongation of the ion-conducting elastomer was obtained. (From...) Figure 17 It can be seen that the ion-conductive elastomer prepared in Example 2 has high stretchability.

[0166] The ion-conductive elastomer obtained in Example 2 was cut into circles with a diameter of 1 cm using a mold. The conductivity of the material was measured using a wide-screen dielectric spectrometer. The broadband dielectric spectrum of the obtained ion-conductive elastomer is shown below. Figure 18 As shown, it has excellent electrical properties.

[0167] The ion-conductive elastomer obtained in Example 2 was applied to a flexible strain sensor. Strain loads were applied using a mechanical testing machine, and the resistance changes of the device were recorded using an LCR meter to characterize its electrical hysteresis and sensitivity. The resistance changes are described in [reference needed]. Figure 19 and Figure 20 . Figure 19 visible, The (resistance change rate) shows a clear linear relationship with the change of strain, and the strain-electrical response linearity of the sensor is good. Figure 20 It can be seen that comparing the processes of "loading" (increased strain) and "unloading" (decreased strain) The two curves do not completely overlap, indicating an "electrical hysteresis" of 1.06%. This suggests a slight hysteresis deviation in the resistance response of the flexible strain sensor during strain loading and unloading cycles. However, a hysteresis rate of 1.06% is relatively low and has minimal impact on practical applications. This flexible strain sensor exhibits excellent strain-resistance response linearity and low electrical hysteresis, demonstrating good sensing performance.

[0168] The purpose of this invention is to provide an ion-conductive elastomer with low hysteresis and high stretchability for high-performance flexible strain sensing. By designing the material to achieve excellent mechanical and electrical properties, its application in flexible strain sensors is expected to enable real-time, high-sensitivity, multi-dimensional sensing, and accurate and stable monitoring of high-frequency signals. Applications of this hysteresis-free, high-performance flexible strain sensor include smart prostheses, wearable devices, and human-computer interaction.

[0169] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing an ion-conducting elastomer, characterized in that, Includes the following steps: S1: Prepare a precursor solution by taking monomers, auxiliaries, crosslinking agents, and electrolytes; S2: Irradiate the precursor liquid with ultraviolet light to obtain an ion-conductive elastomer; The monomer has a carbon chain length of C2 to C3. 12 The alkyl acrylate is any one of the following, wherein the auxiliary agent is isobornyl acrylate, and the crosslinking agent is tricyclic [5.2.1.0]. 2,6 Decane-1,5-diethanol diacrylate.

2. The method for preparing the ion-conductive elastomer according to claim 1, characterized in that, The electrolyte is lithium bis(trifluoromethanesulfonylimide).

3. The method for preparing the ion-conductive elastomer according to claim 1, characterized in that, The molar ratio of the monomer to the auxiliary is 10:2 to 11:

1.

4. The method for preparing the ion-conductive elastomer as described in claim 1, characterized in that, The ratio of the mass of the electrolyte to the combined mass of the monomer and the auxiliary is 0.83 to 1.

5. The method for preparing the ion-conductive elastomer according to claim 1, characterized in that, The molar amount of the crosslinking agent accounts for 1% to 2% of the sum of the molar amounts of the monomer and the auxiliary agent.

6. The method for preparing the ion-conducting elastomer according to claim 1, characterized in that, S1 further includes: preparing the precursor solution by taking a photoinitiator.

7. The method for preparing the ion-conductive elastomer according to claim 6, characterized in that, The photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

8. The method for preparing the ion-conductive elastomer as described in claim 6, characterized in that, S2 further includes: injecting the precursor liquid into a glass mold covered with a polytetrafluoroethylene film and separated by a polydimethylsiloxane sheet, and irradiating the precursor liquid with ultraviolet light.

9. An ion-conducting elastomer, characterized in that, It is prepared by the method for preparing ion-conductive elastomer as described in any one of claims 1-8.

10. A flexible strain sensor, characterized in that, It includes a copper wire and an ion-conducting elastomer as described in claim 9, wherein the ion-conducting elastomer is provided with a electrode region, and the copper wire is connected to the electrode region by silver paste.

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