Preparation method of liquid crystal elastomer self-sensing driver with sandwich structure

Abstract

The invention discloses a preparation method of a sandwich-structure liquid crystal elastomer self-sensing driver, and belongs to the technical field of liquid crystal elastomer sensing-driving integration. According to the invention, a fiber with a'core-wrapping-shell 'sandwich structure is adopted; a core layer is a stretched single-domain liquid crystal elastomer and can generate rapid and reversible mechanical deformation under external stimulation; the cladding is a highly-oriented silver nanowire array containing a silver-sulfur coordination bond, and has the dual functions of electric sensing and photothermal conversion; and the shell layer is a liquid crystal elastomer with an iron-oxygen coordination bond, and has the functions of geometrical shape memory and mechanical damage prevention. Triple functional gradient distribution is formed from the core to the shell, so that each function is independent and synergetic; the mechanical modulus gradually increased from inside to outside can greatly dissipate internal stress caused by strain mismatch of the inner layer and the outer layer, so that stable performance can be kept under cyclic stimulation response, and the composite material can be applied to the fields of wearable medical equipment, reconfigurable intelligent fabrics and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid crystal elastomer driving-sensing integration, and particularly relates to a preparation method of a sandwich structure liquid crystal elastomer self-sensing driver. BACKGROUND

[0002] In recent years, the development of smart materials has shown a trend of multifunctional integration, which is expected to realize the reception, processing and response of external signals, similar to the "perception-decision-execution" integrated process in the biological nervous system. Therefore, the self-sensing driver integrating "driving-sensing" dual functions in a single material body is considered as an important breakthrough for the next generation of smart material systems. The self-sensing driver uses the changes of electrical, optical or magnetic signals of the material itself to output real-time state feedback while producing macroscopic deformation, realizing the bionic closed loop of "one fiber, two functions". Researchers have achieved driving-sensing integration in soft materials such as liquid crystal elastomers, dielectric elastomers and hydrogels by embedding conductive networks, building ion channels and designing micro-nano crack structures. However, the existing systems still face common bottlenecks such as conductive network fatigue, signal drift and shape memory degradation, which restrict their long-term reliable service in wearable medical, soft robots and meta-universe tactile interfaces.

[0003] Liquid crystal elastomers are formed by moderate cross-linking of liquid crystal polymers, combining the anisotropy of crystals and the soft elasticity of rubber. They can achieve large reversible deformation under stimulation and are ideal substrates for building self-sensing drivers. Fibers, as another important geometric form besides films and blocks, have many advantages worth attention. First, fibers have inherent one-dimensional structure, making them a unit for constructing multifunctional modules in two-dimensional and three-dimensional structures from the bottom up. Second, the high aspect ratio of fibers gives them high flexibility, making them an ideal choice for flexible smart materials. Third, one-dimensional structure has high specific surface area, which can improve the efficiency of receiving stimuli and achieve faster response speed. Finally, the lightness, flexibility, good stability and high sensitivity of liquid crystal elastomer fibers provide an ideal material platform for efficient human-computer interaction. However, in the process of cyclic driving, the destruction of the conductive network and the slippage of the polymer chain together cause the existing liquid crystal elastomer fibers to be difficult to recover to the initial shape after multiple deformations, thereby losing their core function of reversible driving. To solve the above problems, the present application uses chemical bonding to construct a robust multi-level structure fiber composed of a core layer, a cladding layer and a protective layer, each layer having its own unique function corresponding to the driving layer, the sensing layer and the protective layer, respectively, which can effectively solve the problem of poor stability of liquid crystal elastomer fiber drivers and achieve complementary enhancement in function. SUMMARY

[0004] This invention aims to address the shortcomings of existing fiber sensors in terms of cyclic stability and geometric reconfigurability by proposing a method for fabricating a sandwich-structured liquid crystal elastomer self-sensing actuator.

[0005] This invention relates to a sandwich-structured liquid crystal elastomer self-sensing actuator, composed of three layers: a core layer (a stretch-oriented single-domain liquid crystal elastomer), a cladding layer (a highly oriented array of silver nanowires with silver-sulfur coordination bonds), and a shell layer (a liquid crystal elastomer with iron-oxygen coordination bonds). The shell layer can undergo geometric reconstruction under the dynamic and reversible action of these iron-oxygen coordination bonds.

[0006] This invention first involves silver-sulfur coordination bonding between a silver nanowire solution of a certain concentration and a chain extender with thiol-terminated ends on both sides. This solution is then uniformly injected into a 1 mm inner diameter glass capillary. The silver nanowires are oriented into a highly oriented array on the inner wall of the glass tube. After drying, the array is deposited on the inner wall of the glass. A mixture containing acrylate liquid crystal molecules, thiol-type crosslinking / chain extender, initiator, catalyst, and toluene is heated and melted to form precursor solution I. This precursor solution I is injected into the treated capillary, where Michael addition polymerization occurs to obtain liquid crystal elastomer fibers. These fibers are then stretched and oriented before being placed back into the glass capillary as the core layer. The outer layer is infused with precursor solution II containing benzoic acid acrylate liquid crystal molecules, acrylate liquid crystal molecules, thiol-type crosslinking / chain extender, initiator, and toluene. After being removed from the capillary, a sandwich-structured liquid crystal elastomer fiber is obtained. The core layer primarily provides the driving function, the cladding layer combines sensing and photothermal effects, and the outer layer is responsible for geometric shape memory and protection of the internal structure.

[0007] The method for fabricating a high-stability sandwich-structured liquid crystal elastomer self-sensing actuator of the present invention includes the following steps:

[0008] Step 1: Fabrication of highly oriented silver nanowire arrays

[0009] A syringe containing a 5-20 mg / mL silver nanowire solution was connected to an extruder and injected at a uniform rate into a glass capillary with an inner diameter of 1 mm. The silver nanowires were aligned along the direction of shear force. After drying, a glass capillary with a highly oriented array of silver nanowires inside the capillary wall was obtained.

[0010] In step 1, the silver nanowires are prepared by the following method:

[0011] Dissolve 5g of polyvinylpyrrolidone in 200 mL of glycerol, add 2.5g of silver nitrate and 0.15g of sodium chloride, and place in an oven at 180℃ for 16 h. After cooling to room temperature, the resulting silver nanowire solution is centrifuged and washed multiple times to remove excess polyvinylpyrrolidone and glycerol, and the silver nanowires are obtained and dispersed in ethanol for later use.

[0012] In step 1, the silver nanowire solution is prepared as follows:

[0013] Take 50 mL of silver nanowire solution dispersed in ethanol, add 5 mL of mercapto-type chain extender, and stir at room temperature for 6 h to carry out silver-sulfur coordination bonding to obtain a silver nanowire solution with a concentration of 5-20 mg / mL.

[0014] In step 1, the glass capillary is a hydrophilic capillary that has been treated with a plasma cleaner for 5 minutes.

[0015] In step 1, the mercapto-type chain extender is ethylenedithiol diacetate, whose structural formula is shown below:

[0016] .

[0017] Step 2: Polymerization of the core layer liquid crystal elastomer

[0018] A mixture containing acrylate liquid crystal molecules, thiol crosslinking agent, thiol chain extender, photoinitiator, catalyst, and toluene is heated to 80°C to melt and form precursor solution I. One end of the glass capillary obtained in step 1 is immersed in precursor solution I. Precursor solution I enters the glass capillary through capillary force and undergoes a thiol Michael addition reaction. After the reaction is completed, the fiber core is removed, stretched to 1.5-3 times its original length, and then placed back into a glass capillary with an inner diameter of 1 mm.

[0019] In step 2:

[0020] The acrylate liquid crystal molecule is 2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate (RM257), and its structural formula is shown below:

[0021] .

[0022] The thiol-type crosslinking agent is pentaerythritol tetra-3-mercaptopropionate, and its structural formula is shown below:

[0023] .

[0024] In step 2, the molar ratio of acrylate functional groups in the acrylate-based liquid crystal molecule to thiol functional groups in the thiol crosslinking and chain extender is greater than 1:1.

[0025] The catalyst used is di-n-propylamine.

[0026] The photoinitiator is α,α-dimethoxy-α-phenylacetophenone.

[0027] In step 2, the amount of each raw material added is as follows by mass: 50-60 parts by mass of acrylate group liquid crystal molecules, 5-7 parts by mass of mercapto crosslinking agent, 9-11 parts by mass of mercapto chain extender, 3-5 parts by mass of photoinitiator, and 14-16 parts by mass of catalyst.

[0028] In step 2, the reaction temperature is 40-80℃.

[0029] Step 3: Fabrication of sandwich-structured liquid crystal elastomer fiber actuators

[0030] A mixture containing benzoic acid acrylate liquid crystal molecules, acrylate liquid crystal molecules, thiol crosslinking agent, thiol chain extender, photoinitiator, polymerization inhibitor, and toluene is heated to melt to form precursor liquid II. Precursor liquid II is injected into a capillary using a syringe, and free radical polymerization is completed under ultraviolet light. After polymerization, the intact fiber is taken out and immersed in sodium hydroxide solution and ferric chloride solution in sequence to complete the set geometric shape memory.

[0031] In step 3:

[0032] The benzoic acid acrylate liquid crystal molecule is (4-(6-acryloyloxyhexyloxy)benzoic acid) (6OBA), and its structural formula is shown below:

[0033] .

[0034] The acrylate liquid crystal molecules, thiol crosslinking agents, and thiol chain extenders are the same as in step 2.

[0035] In step 3, the molar ratio of acrylate functional groups in the acrylate-based liquid crystal molecule to the total mercapto functional groups in the mercapto-type crosslinker and mercapto-type chain extender is greater than 1:1.

[0036] The photoinitiator is diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide.

[0037] The polymerization inhibitor is tert-butylhydroquinone.

[0038] In step 3, the amount of each raw material added is as follows by mass: 35-40 parts by mass of acrylate group liquid crystal, 25-30 parts by mass of benzoic acid acrylate group liquid crystal molecule, 5-7 parts by mass of mercapto crosslinking agent, 9-11 parts by mass of mercapto chain extender, 3-5 parts by mass of photoinitiator, and 3-5 parts by mass of polymerization inhibitor.

[0039] The power of the ultraviolet light is 0.3 W / cm². 2 .

[0040] The concentrations of the sodium hydroxide solution and the ferric chloride solution are both 1 mol / L.

[0041] The sandwich-structured liquid crystal elastomer self-sensing actuator is placed in a 0.5-1 mol / L ethylenediaminetetraacetic acid aqueous solution and subjected to iron-oxygen coordination deactivation at 25-40℃ for 5-60 min. It is then re-treated in a ferric chloride solution to form new iron-oxygen coordination bonds, enabling multiple cycles of geometric reconstruction. The reconstruction cycle count is ≥ 100 times, the shape fixation rate is ≥ 95%, and the recovery rate is ≥ 95%.

[0042] The sandwich-structured liquid crystal elastomer self-sensing actuator of this invention deforms within 10 s under 808 nm near-infrared light illumination, and the synchronous resistance change is ≥ 1.3, which can be used for self-sensing actuation and wearable health monitoring.

[0043] This invention provides a method for fabricating a sandwich-structured liquid crystal elastomer self-sensing actuator. First, a single-domain liquid crystal elastomer core undergoes dual orientation via silver nanowire induction and stretching, providing a foundation for large-scale deformation. Second, a large-scale, highly oriented array of silver nanowires, after shear force-induced silver-sulfur coordination, is assembled as a substrate. This substrate possesses four key functions: 1) improving the directional alignment of liquid crystal molecules through parallel grooves between nanowires; 2) laying the foundation for electrosensing through a percolation network formed between nanowires; 3) endowing the substrate with excellent photothermal properties based on the plasmon resonance effect of silver nanowires; and 4) silver-sulfur coordination making the silver nanowires a giant crosslinking agent, significantly enhancing the interfacial interaction between organic and inorganic phases. Finally, the protective layer on the outer side of the constructed sandwich structure effectively protects the cladding from damage, and the excess acrylate groups generated during core polymerization can further undergo free radical polymerization with the thiol groups of the outer layer, thereby improving the interfacial problem between the organic phases. This allows the protective layer to act as an exoskeleton, further preventing irreversible deformation caused by slippage of the core liquid crystal elastomer chains, thus significantly improving its actuation and sensing stability.

[0044] In summary, this invention provides a method for fabricating a sandwich-structured liquid crystal elastomer fiber actuator. The main advantage lies in constructing a sandwich-structure actuator to achieve functional partitioning, with each component working synergistically without interference. The crosslinking density gradually increases from the fiber core to the fiber shell, forming a dual gradient of mechanical modulus and function, which helps solve interface problems caused by uneven stress during actuation deformation. This design employs a sandwich structure, where the core, middle, and shell layers respectively simulate the biomimetic functions of muscle (actuation), nerve (signal conversion / sensing), and skeleton (protection and reconstruction). This functional decoupling and synergistic design enables highly stable cyclic actuation and synchronous sensing under reconfigured geometry. This invention provides a new approach for highly actuated cyclically stable liquid crystal elastomers and a new method for constructing novel self-sensing actuators for liquid crystal elastomers. Attached Figure Description

[0045] Figure 1These are scanning electron microscope images of the silver nanowire array prepared according to this invention. From... Figure 1 As can be seen, the silver nanowires are highly oriented and overlap each other to form a percolation network.

[0046] Figure 2 These are scanning images of the liquid crystal elastomer fibers prepared according to this invention. Figure 2 As can be seen, the fibers have a layered structure.

[0047] Figure 3 This is the tensile strain-resistance relationship of the liquid crystal elastomer fiber prepared by this invention.

[0048] Figure 4 This is the driving cycle data of the liquid crystal elastomer fiber prepared by this invention.

[0049] Figure 5 The liquid crystal elastomer fiber prepared by this invention is subject to 1 W / cm 2 The electrical resistance changes under near-infrared light stimulation. Figure a is an optical photograph of the near-infrared light stimulation; Figure b is the electrical resistance at 1 W / cm². 2 Cyclic data on resistance changes under near-infrared light stimulation.

[0050] Figure 6 This is a photograph (scale bar is 1cm) showing how the liquid crystal elastomer fibers prepared by this invention can be reshaped into different geometric shapes. Detailed Implementation

[0051] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0052] Example 1: Complete fabrication of a sandwich-structured liquid crystal elastomer fiber sensor

[0053] 1. Synthesis of silver nanowires

[0054] 5 g of polyvinylpyrrolidone was dissolved in 200 mL of glycerol. To accelerate the dissolution rate, this process was carried out in an oven at 120 °C. After the solution cooled, silver nitrate solution (2.5 g of silver nitrate dissolved in 1.5 mL of deionized water) and sodium chloride solution (0.15 g of sodium chloride dissolved in 1 mL of water) were added, and the solution was placed in an oven at 180 °C for 16 h. After cooling to room temperature, the resulting silver nanowire solution was centrifuged and washed multiple times to remove excess polyvinylpyrrolidone and glycerol. Finally, the resulting silver nanowires were dispersed in ethanol for later use.

[0055] 2. Silver-sulfur coordination modification

[0056] Take 50 ml of silver nanowire solution dispersed in ethanol, add 5 ml of 2,2-(ethylenedioxy)diethylthiol, stir at 25℃ and 300 rpm for 6 h; centrifuge and wash to remove free organic matter, then redisperse with anhydrous ethanol to obtain a 10 mg / mL silver nanowire solution.

[0057] 3. Construction of highly oriented silver nanowire arrays

[0058] Borosilicate glass capillaries with an inner diameter of 1 mm were hydrophilized by oxygen plasma treatment for 5 min. An ethanol solution of silver nanowires was loaded into a syringe and injected into the capillary at a constant rate of 30-50 mL / h using a micro-injection pump. Immediately after injection, the capillary was placed in an 80℃ oven for vertical drying to evaporate the solvent. The resulting shear force caused the silver nanowires to align tightly along the axial direction, forming a continuous conductive layer.

[0059] 4. Preparation of the core layer liquid crystal elastomer precursor solution (precursor solution I)

[0060] First, 56 parts by mass of RM82 liquid crystal monomer were dissolved in 10 parts by mass of toluene. After stirring at 60°C for 10 min, 10 parts by mass of thiol crosslinking agent, 6 parts by mass of thiol chain extender, 4 parts by mass of photoinitiator and 14 parts by mass of di-n-propylamine catalyst were added sequentially. The mixture was stirred at room temperature in the dark to form a homogeneous solution, thus obtaining precursor solution I.

[0061] 5. In-situ polymerization of the core layer

[0062] One end of the silver nanowire capillary obtained in step 3 was immersed in precursor solution I, and the entire tube was filled by capillary force. It was then placed in an oven to carry out a Michael addition reaction of mercapto-acrylate to obtain a transparent pale yellow solid. The core rod with a diameter of about 0.9 mm was removed, washed with deionized water, and dried.

[0063] 6. Core layer stretching and single-domain formation

[0064] The core rod is stretched to twice its original length, at which point the liquid crystal cells are oriented along the stretching direction. A glass capillary with an inner diameter of 1 mm is then used to insert the stretched core fiber.

[0065] 7. Preparation of cladding / protective layer precursor solution (precursor solution II)

[0066] 30 parts by mass of 6OBA and 37 parts by mass of RM82 were co-dissolved in 11 parts by mass of toluene. After stirring at 60 °C for 10 min, 6 parts by mass of thiol crosslinking agent, 9 parts by mass of thiol chain extender, 3 parts by mass of photoinitiator, and 4 parts by mass of polymerization inhibitor were added sequentially. The mixture was stirred at room temperature in the dark to form a homogeneous solution, thus obtaining precursor solution II.

[0067] 8. UV curing of coating and integral molding

[0068] Precursor liquid II was injected into the annulus using a microsyringe until it was full; it was then exposed to 365 nm ultraviolet light, and free radical polymerization was completed to obtain sandwich-structured liquid crystal elastomer fibers with a diameter of 1 mm.

[0069] Example 2: Photoelectric-thermal driven and sensing performance test

[0070] 1. Resistance-strain calibration: The ends of the fiber in Example 1 were bonded with copper foil using conductive silver paste, and then stretched at 5 mm / min under a stretching machine, while the resistance change was recorded simultaneously.

[0071] 2. Photothermal driven test: using an 808 nm NIR laser (1 W / cm²). 2 When the fiber is vertically irradiated for 2 seconds, the surface temperature rises from 25℃ to 195℃ (infrared thermal imager), causing bending strain; after the light source is turned off and the fiber is allowed to cool naturally for 2 seconds, it returns to its original length, and the shrinkage amplitude decreases by less than 3% after 2000 cycles.

[0072] 3. Demonstration of driver-sensor synchronization

[0073] The fiber is connected to clamps at both ends, at 1 W / cm 2 Deformation was achieved under stimulation by a near-infrared light source, and resistance signals were collected simultaneously, proving that the self-sensing drive function was stable.

[0074] Example 3: Demonstration of Geometric Reconfigurability

[0075] 1. Sample preparation

[0076] The sandwich-structured liquid crystal elastomer fiber obtained in Example 1 was taken as the initial state and denoted as S0.

[0077] 2. Temporary shaping and fixing

[0078] After treatment with sodium hydroxide, the material is fixed into a specific shape and immersed in a ferric chloride solution. Abundant iron-oxygen coordination crosslinking sites form in the shell, locking the shape and yielding a temporary helical configuration S1. After removal, it is rinsed with deionized water at 25°C for 10 seconds and then dried. (Helical pitch = 2.1 mm, shape fixation rate = 98.7%).

[0079] 3. Shape restoration

[0080] The S1 helix was immersed entirely in a 1 mol / L disodium ethylenediaminetetraacetate (pH = 8.0) solution and gently shaken. EDTA forms a stable complex with iron ions, disrupting the iron-oxygen coordination crosslinking in the system and releasing stored elastic potential energy. The helix automatically unwinds under gravity, completely recovering its linear configuration (S2) within 20 minutes. After rinsing with deionized water and drying, the shape recovery rate was calculated to be 97.4%.

[0081] 4. Cyclic Reliability Testing

[0082] Repeat the entire "shaping-restoration" process 100 times, and take samples every 10 times: the shape memory rate remained at 96.8-98.7%, and the shape restoration rate remained at 95.9-97.4%, with no downward trend.

[0083] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for fabricating a sandwich-structured liquid crystal elastomer self-sensing actuator, characterized in that: First, a silver nanowire solution and a chain extender with thiol-terminated ends are coordinated and bonded using a silver-sulfur method. The solution is then uniformly injected into a 1 mm inner diameter glass capillary. The silver nanowires are oriented and arranged into a highly oriented array on the inner wall of the glass tube. After drying, the array is deposited on the inner wall of the glass. Next, a mixture containing acrylate liquid crystal molecules, a thiol-type crosslinking agent, a thiol-type chain extender, an initiator, a catalyst, and toluene is heated and melted to form precursor solution I. This precursor solution I is injected into the treated capillary, where Michael addition polymerization occurs to obtain liquid crystal elastomer fibers. These fibers are then stretched and oriented before being placed back into the glass capillary as the core layer. Finally, precursor solution II, containing benzoic acid acrylate liquid crystal molecules, acrylate liquid crystal molecules, a thiol-type crosslinking agent, a thiol-type chain extender, an initiator, and toluene, is injected into the outer layer. After being removed from the capillary, the sandwich-structured liquid crystal elastomer fibers are obtained.

2. The preparation method according to claim 1, characterized in that... Includes the following steps: Step 1: Fabrication of highly oriented silver nanowire arrays A syringe containing a 5-20 mg / mL silver nanowire solution was connected to an extruder and injected at a uniform rate into a glass capillary with an inner diameter of 1 mm. The silver nanowires were aligned along the direction of shear force. After drying, a glass capillary with a highly oriented array of silver nanowires inside the tube wall was obtained. Step 2: Polymerization of the core layer liquid crystal elastomer A mixture containing acrylate liquid crystal molecules, thiol crosslinking agent, thiol chain extender, photoinitiator, catalyst, and toluene is heated to 80°C to melt and form precursor solution I. One end of the glass capillary obtained in step 1 is immersed in precursor solution I. Precursor solution I enters the glass capillary through capillary force and undergoes a thiol Michael addition reaction. After the reaction is completed, the fiber core is removed, stretched to 1.5-3 times its original length, and then placed back into a glass capillary with an inner diameter of 1 mm. Step 3: Fabrication of sandwich-structured liquid crystal elastomer fiber actuators A mixture containing benzoic acid acrylate liquid crystal molecules, acrylate liquid crystal molecules, thiol crosslinking agent, thiol chain extender, photoinitiator, polymerization inhibitor, and toluene is heated to melt to form precursor liquid II. Precursor liquid II is injected into a capillary using a syringe, and free radical polymerization is completed under ultraviolet light. After polymerization, the intact fiber is taken out and immersed in sodium hydroxide solution and ferric chloride solution in sequence to complete the set geometric shape memory.

3. The preparation method according to claim 2, characterized in that: In step 1, the silver nanowire solution is prepared as follows: Take 50 mL of silver nanowire solution dispersed in ethanol, add 5 mL of mercapto-type chain extender, stir at room temperature for 6 h to carry out silver-sulfur coordination bonding, and obtain a silver nanowire solution with a concentration of 5-20 mg / mL. The mercapto-type chain extender is ethylenedithiol diacetate.

4. The preparation method according to claim 2, characterized in that: In step 2: the acrylate liquid crystal molecule is 2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate, and its structural formula is shown below: ； The thiol-type crosslinking agent is pentaerythritol tetra-3-mercaptopropionate, and its structural formula is shown below: 。 5. The preparation method according to claim 2, characterized in that: In step 2, the amount of each raw material added is as follows by mass: 50-60 parts by mass of acrylate group liquid crystal molecules, 5-7 parts by mass of mercapto crosslinking agent, 9-11 parts by mass of mercapto chain extender, 3-5 parts by mass of photoinitiator, and 14-16 parts by mass of catalyst.

6. The preparation method according to claim 2, characterized in that: In step 2, the reaction temperature is 40-80℃.

7. The preparation method according to claim 2, characterized in that: In step 3: The benzoic acid acrylate liquid crystal molecule is (4-(6-acryloyloxyhexyloxy)benzoic acid), and its structural formula is shown below: 。 8. The preparation method according to claim 2, characterized in that: In step 3, the amount of each raw material added is as follows by mass: 35-40 parts by mass of acrylate group liquid crystal, 25-30 parts by mass of benzoic acid acrylate group liquid crystal molecule, 5-7 parts by mass of mercapto crosslinking agent, 9-11 parts by mass of mercapto chain extender, 3-5 parts by mass of photoinitiator, and 3-5 parts by mass of polymerization inhibitor.

9. The preparation method according to claim 2, characterized in that: In step 3, the concentrations of both the sodium hydroxide solution and the ferric chloride solution are 1 mol / L.

10. The preparation method according to claim 2, characterized in that: The sandwich-structured liquid crystal elastomer self-sensing actuator is placed in a 0.5-1 mol / L ethylenediaminetetraacetic acid aqueous solution and the iron-oxygen coordination is released within 5-60 min at 25-40℃. Then, it is placed in a ferric chloride solution to form new iron-oxygen coordination bonds, thereby achieving multiple cycles of geometric reconstruction.

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