Ionic gel with embedding structure and application of ionic gel in flexible sensing

Abstract

The invention discloses a structural design of ionic gel with an embedding structure and application of the ionic gel in flexible sensing, and relates to the technical field of flexible electronic sensing. The ionic gel comprises a copolymer matrix and conductive ionic liquid, the polymer matrix and the ionic liquid are immiscible with each other; the ionic gel ionic liquid is embedded by the polymer matrix; the polymer skeleton and the ionic liquid in the ionic gel are directly connected through hydrogen bonds and ionic bonds to form a composite polymer network. The high-performance ionic gel has the characteristics of high fracture toughness, high sensitivity, fast response and the like, and effectively overcomes the problems that compared with a polymer matrix, the mechanical property of the ionic gel is greatly reduced, ionic liquid leaks and the like. The invention provides an innovative method for manufacturing the flexible sensor, and the potential application field of the ionic gel in sensing is widened.

Description

Technical Field

[0001] The present invention relates to the field of flexible electronic sensing technology, and particularly to a structural design of an ion gel based on phase separation and its application in flexible sensing. Background Art

[0002] Due to the unique mechanical properties (such as high elasticity and stretchability) and functional characteristics (such as conductivity and sensitivity) of flexible conductive materials, they can sense external stress stimuli and convert them into current changes, showing great application potential in the fields of flexible sensors, electronic skin, human-computer interaction, etc. However, most of the existing flexible conductive materials still face many challenges in practical applications, such as environmental stability, movement wear, and processing difficulties. Therefore, developing flexible conductive materials with simple processes, excellent performance, and environmental stability is of great significance in promoting the industrial application of conductive composites, exploring applications in the field of intelligent robots, and promoting the economic development of the flexible sensor field.

[0003] In recent years, ion gels have been widely concerned, studied, and applied in the fields of flexible sensing, electronic skin, and bionic robots due to their high conductivity, low volatility of ionic liquids, and mechanical properties of polymers, and have better stability than hydrogels. However, even so, some ionic liquids are sensitive to humidity and easily absorb moisture in the environment, affecting their performance; at the same time, ion gels are also liquids, and there is also the problem of liquid leakage. Especially for conductive materials, stress is generally required to change the current. Under stress, these liquids are more likely to leak. At the same time, the mechanical properties of ion gels are poor, especially the toughness is low, and they are only suitable for fields that do not require both mechanical properties. These disadvantages have severely limited the application range of ion gels. Therefore, it is necessary to design a new ion gel structure and develop a new preparation strategy for conductive materials. Summary of the Invention

[0004] The purpose of the present invention is to solve the limitations of the existing technology, aiming at the problems of generally low toughness of current ion gel materials, and challenges such as the decline in long-term use performance and insufficient environmental stability caused by ionic liquid leakage. An ion gel based on a two-phase separation structure and its preparation method provided by the present invention, through optimizing the material structure, the ion gel prepared by "one-pot" photopolymerization has excellent mechanical properties while having excellent fracture toughness, anti-crack propagation ability, and environmental stability.

[0005] Another object of the present invention is to provide an ion gel flexible sensor obtained by using the above preparation method. When used as a flexible sensor, it has high sensitivity, fast response, humidity response, and sensing stability, and can be used in the fields of human motion sensing, air / skin humidity monitoring, and circuit safety.

[0006] Another object of the present invention is that the provided preparation strategy of the two-phase separation structured ionic gel can be applicable to a variety of monomers and ionic liquids, providing flexible material design and preparation schemes for different application scenarios.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A structural design of an ionic gel with an embedded structure and its application in flexible sensing, including:

[0009] S1: Add acrylic acid to the hydroxyethyl acrylate solution, and after ultrasonic treatment, disperse it evenly. Add an ionic liquid, and after ultrasonic treatment again, obtain an ionic gel prepolymer.

[0010] S2: Add a photoinitiator to the ionic gel prepolymer, and after ultrasonic treatment, disperse it evenly to obtain a homogeneous mixed solution.

[0011] S3: Transfer the above mixed liquid to a polytetrafluoroethylene mold, and control ultraviolet light to irradiate it to cure and obtain an ionic gel film.

[0012] S4: Connect both ends of the ionic gel film to the reference electrode and the working electrode of an electrochemical workstation respectively, and a flexible electronic sensor can be obtained. When it is fixed on a human joint, it is a human motion sensor; when it is placed underwater, it is an underwater sensor.

[0013] As a preferred embodiment of the present invention, the ionic liquid is the hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0014] As a preferred embodiment of the present invention, the mass ratio of hydroxyethyl acrylate to acrylic acid is 20:3, and the ratio of the ionic liquid to the total mass of the prepolymer is 22.5%.

[0015] As a preferred embodiment of the present invention, the wavelength range of the ultraviolet light with a preset wavelength is 10 nm to 400 nm, and the illumination time is within 10 min - 15 min.

[0016] As a preferred embodiment of the present invention, the prepared ionic gel has a two-phase separation and a structure of polymer matrix embedding ionic liquid, and can be applied in aspects such as human motion sensing, humidity sensing, and short-time underwater sensing.

[0017] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0018] (1) The preparation method of the ionic gel provided by the present invention forms an ionic gel strategy with a polymer-embedded ionic liquid structure through the principle of phase separation, breaking the inherent strategy of using ionic liquid as a solvent in the preparation of general ionic gels. This unique phase separation structure, with a polymer "sea" embedding ionic liquid "islands", not only retains the excellent mechanical properties of the polymer matrix, but also endows the material with high fracture toughness and resistance to crack propagation, greatly reducing the degree of liquid leakage of the ionic liquid exposed to the environment.

[0019] (2) The ionic gel preparation strategy proposed by the present invention is applicable to a variety of monomers and ionic liquids. For example, when acrylic acid is replaced with N-hydroxyethyl acrylamide and acrylamide, the prepared ionic gel has the same structure and similar mechanical properties.

[0020] (3) The ionic gel with an embedded structure prepared by the present invention has a unique characteristic of enhanced conductivity under stretching, showing high-sensitivity sensing and stable sensing characteristics in humidity detection and easily worn movement scenarios, and can be applied to aspects such as human motion sensing, humidity sensing, and short-time underwater sensing. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is a comparison chart of the tensile strength of Embodiment 1 to Embodiment 5 of the present invention;

[0023] Figure 2 It is a stress-strain curve chart of Embodiment 1, Embodiment 4 and Embodiment 5 of the present invention;

[0024] Figure 3 It is a tensile cycle chart of Embodiment 1 of the present invention;

[0025] Figure 4 It is a comparison chart of the mass change under humid environment of Embodiment 1 and Embodiment 5 of the present invention;

[0026] Figure 5 It is a sensing test chart of the ionic gel film of Embodiment 1 of the present invention. Detailed Embodiments

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] The object of the present invention is to provide a preparation strategy for ionic gels with an embedding structure, which can solve the above technical problems.

[0029] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0030] The present invention provides that the ionic gel includes: a copolymer backbone for regulating mechanical properties, and an ionic liquid monomer without alkenyl groups. The ionic gel is obtained by compounding the ionic liquid monomer without alkenyl groups with the copolymer. Among them, the copolymer uses two monomers with the same hydrophilicity containing C=C double bonds to regulate a copolymer with mechanical properties meeting expectations; the hydrophilicity of the ionic liquid monomer without alkenyl groups should be opposite to that of the copolymer.

[0031] The present invention selects two polymer monomers to better regulate the mechanical properties, but it is not limited to using two monomers for regulation. The only necessary condition for the selected monomers is that they have the same hydrophilicity. The specific types and amounts of monomers can be flexibly designed and the scheme can be prepared according to the performance required in different application scenarios.

[0032] The two monomers selected by the present invention form a copolymer backbone after photocuring; while the mixed ionic liquid does not contain C=C double bonds (alkenyl groups) and still exists in the copolymer backbone in the form of small molecules after photocuring. Because the copolymer and the ionic liquid have different hydrophilicities, the formed system is a two-phase separation system; and because the proportion of the polymer in the system is much larger than that of the ionic liquid, in the ionic gel system, while the copolymer plays a role of a backbone, it embeds the ionic liquid therein; the ionic liquid aggregates in the form of small molecules therein, playing a role of plasticization and conductivity.

[0033] The ionic gel of the present invention belongs to an ionic gel material with a new microstructure. This structure can well retain the excellent mechanical properties of the polymer and confine the ionic liquid inside the polymer to overcome the problem of liquid leakage caused by the easy flow of the ionic liquid at room temperature.

[0034] It should be noted that the present invention does not make any specific restrictions on the ratio of the two monomers in the copolymer and the ratio of the ionic liquid monomer. The polymer monomers can be formed by photocuring at room temperature, which belongs to the prior art, and the polymerization reaction of the monomers will not be further described in detail here.

[0035] Embodiment 2

[0036] By adding ionic liquids with opposite hydrophilicities to two polymer monomers with the same hydrophilicity; wherein, the concentration of the ionic liquids with opposite hydrophilicities is less than that of the two polymer monomers.

[0037] After adding the additive and ultrasonic treatment, it is dispersed evenly to obtain a uniform solution; the additive here is at least one of a photoinitiator, a crosslinking agent, and a plasticizer. Usually, the mass ratio of the additive / ionic liquid is between 1 / 1000 and 20 / 1000. Too high a proportion will lead to an increase in production cost, and too low a proportion will affect the polymerization reaction. Under the above mass ratio, this embodiment selects to use only the photoinitiator.

[0038] Control the ultraviolet light to irradiate and cure the homogeneous solution; as a preferred embodiment of the present invention, the wavelength range of the ultraviolet light with a preset wavelength is 10 nm to 400 nm. Usually, 365 nm can be used. This wavelength range is commonly used in the industry, and the present invention does not limit the selection of the ultraviolet light wavelength range. The reaction temperature can be at room temperature, and the reaction duration can be appropriately adjusted according to the mass ratio of the additive to the ionic liquid containing alkenyl.

[0039] After curing for a predetermined time, the two polymer monomers with the same hydrophilicity are polymerized into a copolymer, and the ionic liquids with opposite hydrophilicities form an aggregated state and are embedded and dispersed in the copolymer skeleton. The predetermined time is determined according to the selection of the monomers and the input amount of the photoinitiator.

[0040] The preparation method of the aforementioned ionic gel proposed by the present invention is to add ionic liquids with opposite hydrophilicities to two polymer monomers with the same hydrophilicity, add a photoinitiator and perform ultrasonic treatment to make it a uniform solution system. After ultraviolet light curing, the polymer monomers with the same hydrophilicity are polymerized to form a copolymer skeleton, and the ionic liquids with opposite hydrophilicities aggregate in the form of small molecules therein, thereby preparing a composite ionic gel material. The ionic gel obtained in this way retains the excellent mechanical properties of the polymer while also retaining high ionic conductivity, so it has broad application prospects.

[0041] Example 1

[0042] This example provides a preparation method of an ionic gel based on phase separation.

[0043] In this example, the polymer monomers with the same hydrophilicity are acrylic acid and 2-hydroxyethyl acrylate, the ionic liquid with opposite hydrophilicity is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the photoinitiator is 1-hydroxycyclohexyl phenyl ketone. The preparation method of the ionic gel with an embedded structure in this example includes the following steps:

[0044] Step 1: weigh 0.3 g of acrylic acid and add it to 2.0 g of hydroxyethyl acrylate. After being evenly dispersed by ultrasonic treatment for 10 minutes, add 0.668 g of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, continue to ultrasonic treatment for 10 minutes to fully mix and obtain an ion gel prepolymer.

[0045] Step 2: Add 0.025 g of photoinitiator, 1-hydroxycyclohexyl phenyl ketone, to the ion gel prepolymer, and then continue ultrasonic treatment for 30 min to fully dissolve and mix. The ultrasonic frequency is 30 KHz.

[0046] Step 3: Transfer the mixed solution to a polytetrafluoroethylene mold and perform photocuring under a UV lamp for 15 minutes.

[0047] Step 4: Peel off the ion gel film. Since the polytetrafluoroethylene mold is a white opaque mold, and the ion gel is also white and opaque due to phase separation, in order to ensure complete polymerization, the side of the ion gel film that contacts the mold is facing up and continues to be illuminated for 10 minutes, and finally an ion gel film with an embedded structure is obtained.

[0048] Embodiment 2

[0049] On the basis of Example 1, Example 2 tests the general applicability of this strategy to other monomers by replacing one of the polymer monomers.

[0050] In this embodiment, the polymer monomers with the same hydrophilicity are N-hydroxyethyl acrylamide and hydroxyethyl acrylate, the ionic liquid with opposite hydrophilicity is 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt, and the photoinitiator is 1-hydroxycyclohexyl phenyl ketone. The preparation method of the ionic gel with an embedded structure in this embodiment includes the following steps:

[0051] Step 1: weigh 0.3 g of N-hydroxyethyl acrylamide and add it to 2.0 g of hydroxyethyl acrylate. After being evenly dispersed by ultrasonic treatment for 10 minutes, add 0.668 g of 1-ethyl-3-methylimidazole bistrifluoromethanesulfonyl imide salt, continue to ultrasonically treat for 10 minutes and mix thoroughly to obtain an ion gel prepolymer.

[0052] Step 2: Add 0.025 g of photoinitiator, 1-hydroxycyclohexyl phenyl ketone, to the ion gel prepolymer, and then continue ultrasonic treatment for 30 min to fully dissolve and mix. The ultrasonic frequency is 30 KHz.

[0053] Step 3: Transfer the mixed solution to a polytetrafluoroethylene mold and perform photocuring under a UV lamp for 15 minutes.

[0054] Step 4: Peel off the ion gel film. Since the polytetrafluoroethylene mold is a white opaque mold, and the ion gel is also white and opaque due to phase separation, in order to ensure complete polymerization, the side of the ion gel film that contacts the mold is facing up and continues to be illuminated for 10 minutes, and finally an ion gel film with an embedded structure is obtained.

[0055] Embodiment 3

[0056] On the basis of Example 1, Example 3 tests the general applicability of this strategy to other monomers by replacing one of the polymer monomers.

[0057] In this embodiment, the polymer monomers with the same hydrophilicity are acrylamide and hydroxyethyl acrylate, the ionic liquid with opposite hydrophilicity is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and the photoinitiator is 1-hydroxycyclohexylphenyl ketone. The preparation method of the ionic gel with an embedded structure in this embodiment includes the following steps:

[0058] Step 1: weigh 0.3 g of acrylamide and add it to 2.0 g of hydroxyethyl acrylate. After being evenly dispersed by ultrasonic treatment for 10 minutes, 0.668 g of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt was added, and ultrasonic treatment was continued for 10 minutes to fully mix and obtain an ion gel prepolymer.

[0059] Step 2: Add 0.025 g of photoinitiator, 1-hydroxycyclohexyl phenyl ketone, to the ion gel prepolymer, and then continue ultrasonic treatment for 30 min to fully dissolve and mix. The ultrasonic frequency is 30 KHz.

[0060] Step 3: Transfer the mixed solution to a polytetrafluoroethylene mold and perform photocuring under a UV lamp for 15 minutes.

[0061] Step 4: Peel off the ion gel film. Since the polytetrafluoroethylene mold is a white opaque mold, and the ion gel is also white and opaque due to phase separation, in order to ensure complete polymerization, the side of the ion gel film that contacts the mold is facing up and continues to be illuminated for 10 minutes, and finally an ion gel film with an embedded structure is obtained.

[0062] Embodiment 4

[0063] In this example, the copolymer skeleton in Example 1 was prepared to compare the mechanical properties of the ion gel and the polymer matrix.

[0064] In this embodiment, the polymer monomers are hydrophilic acrylic acid and hydroxyethyl acrylate, and the photoinitiator is 1-hydroxycyclohexyl phenyl ketone. The method for preparing a strong and tough copolymer having a stress-strain curve in this embodiment comprises the following steps:

[0065] Step 1: Weigh 0.3 g of acrylic acid and add it to 2.0 g of 2-hydroxyethyl acrylate. After ultrasonic treatment for 10 min to disperse evenly, add 0.025 g of photoinitiator, 1-hydroxycyclohexyl phenyl ketone, to the evenly mixed solution. Finally, continue ultrasonic treatment for 30 min to dissolve and mix evenly. The ultrasonic frequency is 30 KHz.

[0066] Step 2: Transfer the above mixed solution to a polytetrafluoroethylene mold and carry out photocuring under an ultraviolet lamp for 15 min.

[0067] Step 3: Peel off the ion gel film. Since the polytetrafluoroethylene mold is a white opaque mold, even though the 2-hydroxyethyl acrylate-acrylic acid copolymer is a transparent copolymer, in order to ensure complete polymerization, the side of the polymer film in contact with the mold is still facing up, and continue light irradiation for 10 min to finally obtain the polymer film.

[0068] Example 5

[0069] On the basis of Example 1, in this Example 5, ionic liquids with different hydrophilicities are replaced by ionic liquids with the same hydrophilicity to test the stability comparison of the ion gels prepared by the present invention and other strategies.

[0070] In this example, the polymer monomers with the same hydrophilicity are acrylic acid and 2-hydroxyethyl acrylate, the ionic liquid with the same hydrophilicity is 1-ethyl-3-methylimidazolium ethyl sulfate, and the photoinitiator is 1-hydroxycyclohexyl phenyl ketone. Because the hydrophilicities of the copolymer and the ionic liquid are the same in this example, in this system, the ionic liquid and the polymer backbone can be well mixed evenly. After ultraviolet light irradiation, the monomers polymerize to form a copolymer, and the ionic liquid acts as a dispersant in the system and is evenly dispersed under the action of hydrogen bonds and ionic bonds. The general preparation method of the ion gel in this example includes the following steps:

[0071] Step 1: Weigh 0.3 g of acrylic acid and add it to 2.0 g of 2-hydroxyethyl acrylate. After ultrasonic treatment for 10 min to disperse evenly, add 0.668 g of 1-ethyl-3-methylimidazolium ethyl sulfate, and continue ultrasonic treatment for 10 min to mix evenly to obtain an ion gel prepolymer.

[0072] Step 2: Add 0.025 g of photoinitiator, 1-hydroxycyclohexyl phenyl ketone, to the ion gel prepolymer, and finally continue ultrasonic treatment for 30 min to dissolve and mix evenly. The ultrasonic frequency is 30 KHz.

[0073] Step 3: Transfer the above mixed solution to a polytetrafluoroethylene mold and carry out photocuring under an ultraviolet lamp for 15 min.

[0074] Step 4: Peel off the ionic gel film. Since the PTFE mold is a white opaque mold, even if the prepared ionic gel is a transparent ionic gel, in order to ensure complete polymerization, the side of the ionic gel film in contact with the mold is still facing up, and light is continued to irradiate for 10 min, and finally a polymer film is obtained.

[0075] Ionic gel performance test:

[0076] Take the ionic gels and polymers of Examples 1 to 5 and conduct stress-strain tests.

[0077] The tensile strength comparison diagrams of Examples 1 to 5 are as Figure 1 shown.

[0078] Figure 2 It is a schematic diagram of the uniaxial stress-strain curve of the material films provided in Examples 1, 4, and 5.

[0079] Take the ionic gel of Example 1 and conduct cyclic tensile tests. The results are as Figure 3 shown, Figure 3 It is a schematic diagram of the cyclic tensile curve of the ionic gel provided in Example 1 under different strains.

[0080] Take the ionic gels of Examples 1 and 5 and conduct humidity environment stability tests. The results are as Figure 4 shown. Figure 4 It is a diagram of the stability test results of the ionic gels of Examples 1 and 5 in a humid environment.

[0081] Take the ionic gel film of Example 1, prepare it into a rectangle of 3 cm × 1 cm, and conduct sensing tests with an electrochemical workstation. The results of the relative resistance change with strain are as Figure 5 shown.

[0082] As Figure 1 shown, for the ionic gels with an embedded structure prepared in Examples 1 to 3 of the present invention, the tensile strength is all above 2.5 MPa. As a polymer, the tensile strength of Example 4 is significantly higher than that of Examples 1 and 5; while the tensile strength of the general ionic gel of Example 5 is significantly lower than that of other materials.

[0083] Figure 2 It is a uniaxial tensile comparison diagram of Examples 1, 4, and 5, and is a tensile comparison of the ionic gel with an embedded structure, the polymer matrix, and the general ionic gel prepared from the same polymer backbone prepared in the present invention. Compared with the general ionic gel, the ionic gel with an embedded structure obviously has better mechanical properties, because the embedded structure of the present invention retains the intermolecular interaction of the polymer, thus retaining the excellent mechanical properties of the polymer.

[0084] Figure 3 Figure 1 shows the continuous multiple cyclic loading and unloading curves of the ionic gel in Example 1 under different strains. It can be seen from the cyclic curves that the ionic gel in Example 1 has a closed hysteresis loop within the applied strain range, indicating significant energy dissipation. As the deformation increases from 50% to 300%, the energy dissipation increases from 6.24 kJ / m2 to 176.76 kJ / m2. The high energy dissipation ability exhibited by the ionic gel in Example 1 during cyclic loading directly reflects its excellent impact resistance and toughness.

[0085] As Figure 4 shown, the high hygroscopicity and leakage risk of ionic liquids have long been pain points that plague and affect the application stability of ionic gels. No obvious leakage of ionic liquids was observed within 4 hours after the successful preparation of the ionic gels in Example 1 and Example 5. We placed the ionic gels in Example 1 and Example 5 in a normal room temperature environment and observed and recorded the weight changes within one week. As the exposure time in the humid environment increased, the weights of the ionic gels in Example 1 and Example 5 both showed an overall increasing trend. The specific weight would change with the change of environmental humidity, but the increase in Example 5 was more significant, and the weight changes in the following four days were also much larger than those in Example 1, indicating that Example 1 is more stable than Example 5 in a humid environment.

[0086] Figure 5 Figure 2 shows the relative resistance change (ΔR / R0) of the ionic gel in Example 1 as a sensor under different strain amplitudes (3%, 10%, 20%, 30%, 40%). As the strain increases, the resistance change rate of the ionic gel in Example 1 also increases.

[0087] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0088] Specific examples are used in this article to elaborate on the principles and implementation methods of the present invention. The descriptions of the above embodiments are only used to help understand the core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. Structural design of an ion gel with an embedded structure and its application in flexible sensing, characterized in that, The ionic gel includes: one or more polymer monomers with the same hydrophilicity and an ionic liquid with the opposite hydrophilicity. The ionic gel is obtained by compounding the polymer monomers and the ionic liquid. Among them, the compatible monomers polymerize to form a backbone, and the incompatible ionic liquid aggregates in the form of free small molecules therein, playing a role in plasticization and conduction. The preparation method includes: S1: Add one or more polymer monomers with the same hydrophilicity and an ionic liquid with the opposite hydrophilicity, and add a certain amount of additives, then perform ultrasonic treatment after blending to obtain a uniformly dispersed mixed solution. Among them, the concentration of the ionic liquid with the opposite hydrophilicity is less than that of the two polymer monomers. The additives here are at least one of a photoinitiator, a crosslinking agent, and a plasticizer; S2: Take a predetermined amount of the mixed solution and place it in a polytetrafluoroethylene template, and cure it with ultraviolet light of a preset wavelength until the monomers polymerize to obtain an ionic gel film. S3: Cut the ionic gel film into a suitable size, fix it on a human joint, and connect both ends to electrodes to obtain a human motion sensor; place it on the human skin to obtain a human humidity sensor.

2. The ionic gel according to claim 1, wherein, A two-phase separation structure is formed between the ionic liquid and the copolymer backbone, and the ionic liquid is embedded inside the material by the polymer backbone.

3. The ionic gel according to claim 1, wherein The two polymer monomers with the same hydrophilicity include acrylic acid and 2-hydroxyethyl acrylate, and the ionic liquid with the opposite hydrophilicity is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

4. The ionic gel according to claim 1, characterized in that, The mass ratio of 2-hydroxyethyl acrylate to acrylic acid is 20:3, and the ionic liquid accounts for 22.5% of the total mass of the prepolymer.

5. The ionic gel according to claim 4, wherein The wavelength range of the ultraviolet light is 10 nm to 400 nm, and the illumination time is 10 min to 15 min.

6. The ionic gel according to claim 1, characterized in that, The ionic gel is used to prepare a flexible sensor. The flexible sensor has high sensitivity, fast response, and sensing stability. The flexible sensor is suitable for human motion sensing, humidity sensing, and short-time underwater sensing. The above claims cover the core technical features, specific implementation manners, and application fields of the invention, ensuring the clarity and integrity of the patent protection scope.

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