Liquid crystal elastomer actuator with multi-stimuli response and self-sensing function, preparation method and application thereof

Abstract

The application provides a preparation method of a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function. The method takes a liquid crystal elastomer film as a substrate, and forms a multi-layer composite structure by screen printing technology to deposit different functional inks on the surface of the liquid crystal elastomer film. The liquid crystal elastomer film can produce shrinkage deformation in response to temperature stimulation; the electrothermal / sensing ink layer not only has excellent joule heating effect to generate driving temperature, but also has the ability to monitor the movement behavior by producing obvious resistance change along with the shrinkage of the liquid crystal elastomer film; the photo-thermal ink layer can effectively convert light energy into heat energy, thereby realizing light-controlled driving behavior. The application effectively combines the screen printing technology and the liquid crystal elastomer film, and realizes the light and electric stimulation driving of the liquid crystal elastomer soft actuator by a simple and efficient method, and further endows the liquid crystal elastomer actuator with the function of self-sensing in the movement process, thereby providing a new scheme for the complex scene application of the liquid crystal elastomer actuator.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal elastomer actuator technology, specifically relating to a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function and its preparation method, and also relating to the application of a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function in the fields of soft robots, wearable electronics and flexible actuators. Background Technology

[0002] Liquid crystal elastomers are a type of stimulus-responsive smart material. Because they can produce large and reversible deformations at transition temperatures, and their contractile stress is similar to that of natural muscles, they have broad application prospects in soft robotics, wearable electronics, and flexible actuators.

[0003] Traditional liquid crystal elastomer (LCE) actuators typically achieve active actuation by directly crosslinking functional materials to the LCE network or depositing them on the LCE surface. This process is complex and the actuators are only affected by a single external stimulus, significantly limiting their applications. Furthermore, endowing LCE actuators with self-sensing capabilities enables real-time monitoring of the motion process, aiding in precise control and motion prediction. However, currently reported LCE actuators with self-sensing capabilities suffer from weak signal strength, making them unsuitable for practical applications.

[0004] Therefore, providing a high-performance self-sensing liquid crystal elastomer actuator with multi-stimulus response prepared by a simple method to meet the usage requirements of liquid crystal elastomer actuators in complex application scenarios is an urgent technical problem to be solved. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for preparing a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function.

[0006] The second objective of this invention is to provide a liquid crystal elastomer actuator product with multi-stimulus response and self-sensing function.

[0007] The third objective of this invention is to provide an application of a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function in the fields of soft robotics, wearable electronics and flexible actuators.

[0008] One of the technical solutions adopted to achieve the objective of this invention is: to provide a method for preparing a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function, comprising the following steps:

[0009] S1. Simultaneously perform uniaxial stretching and curing on multidomain liquid crystal elastomer material to obtain single-domain liquid crystal elastomer material.

[0010] S2. Prepare electrothermal / sensing inks with a solid content of 30wt.%-40wt.% and photothermal inks with a solid content of 3wt.%-5wt.% respectively;

[0011] S3. The electrothermal / sensing ink is deposited on the surface of the single-domain liquid crystal elastomer material by screen printing, with 2 to 4 layers to form an electrothermal / sensing ink layer.

[0012] S4. The photothermal ink is deposited on the surface of the electrothermal / sensing ink layer by screen printing, with 1 to 2 layers deposited to form a photothermal ink layer.

[0013] S5. Remove the solvent from the electrothermal / sensing ink layer and the photothermal ink layer to obtain a liquid crystal elastomer actuator with a multilayer composite structure.

[0014] The overall concept of this invention is as follows: Addressing the shortcomings of existing technologies, this invention provides a method for fabricating a liquid crystal elastomer actuator with multi-stimulus response and self-sensing capabilities. This method utilizes screen printing technology to prepare a multi-layer composite structure. By depositing two functional inks with good printability onto the surface of the liquid crystal elastomer, the actuator acquires multi-stimulus response and self-sensing functions. The multi-layer printed structure with different functions formed by overprinting enables the liquid crystal elastomer soft actuator to generate motion deformation under light / electric stimulation, while simultaneously generating electrical signals for real-time motion monitoring.

[0015] In the above preparation method, the multi-domain liquid crystal elastomer material is first subjected to uniaxial stretching and photocuring. The single-domain liquid crystal elastomer material obtained after stretching and curing has a smooth and flat surface without obvious pores, cracks and protrusions, so as to facilitate the subsequent deposition of functional inks on the surface of the liquid crystal elastomer film.

[0016] Secondly, to ensure the normal operation of photothermal / electrothermal actuation and actuation sensing, the number of ink layers needs to be controlled to within 6 layers (2-4 layers of electrothermal / sensing ink and 1-2 layers of photothermal ink). Correspondingly, the number of printing layers can be controlled by optimizing the solid content of the ink. For electrothermal / sensing ink, too low a solid content will result in an insignificant Joule heating effect, while too high a solid content will lead to a low binder content and decreased adhesion, making it difficult to achieve tight adhesion with the liquid crystal elastomer film, and easily causing the printed layer to peel off during actuation. For photothermal ink, too little filler makes it difficult to deposit evenly with 1-2 printing layers, while too much filler makes it difficult for the photothermal ink to disperse evenly and results in poor adhesion, easily causing peeling. Through extensive research, this invention sets the solid content of the electrothermal / sensing ink to 30wt.%-40wt.% and the solid content of the photothermal ink to 3wt.%-5wt.% to achieve the fabrication of a high-performance actuator.

[0017] Finally, following the sequence of first printing the electrothermal / sensing ink and then overlaying the photothermal ink, an electrothermal / sensing ink layer and a photothermal ink layer are sequentially formed on the surface of the liquid crystal elastomer film. When the photothermal ink layer on the surface is stimulated by light, the photothermal nanomaterials contained within it can convert light energy into heat energy, thereby improving the photothermal conversion efficiency.

[0018] Further, in step S1, the preparation method of the multi-domain liquid crystal elastomer material includes: dissolving liquid crystal monomers in an organic solvent to obtain a mixed solution; adding chain extender, crosslinking agent, catalyst, and photoinitiator to the mixed solution, mixing well, injecting into a mold, and reacting for a certain time to obtain the multi-domain liquid crystal elastomer material.

[0019] Preferably, the liquid crystal monomer is dissolved in an organic solvent at a temperature of 60-80°C to obtain a mixed solution; at room temperature, a chain extender, a crosslinking agent, a catalyst, and a photoinitiator are added to the mixed solution and stirred continuously to make it uniform; the uniform mixed solution is injected into a mold and placed in a dark environment at room temperature for 12-24 hours, and then placed in a vacuum oven at 70-90°C for 12-24 hours to obtain a multi-domain liquid crystal elastomer material.

[0020] More preferably, in the above preparation method, the mass ratio of liquid crystal monomer to organic solvent is 1:(0.2-0.4); the mass ratio of liquid crystal monomer, chain extender, crosslinking agent, catalyst, and photoinitiator is 1:(0.15-0.35):(0.006-0.06):(0.002-0.4):(0.004-0.008).

[0021] Preferably, the liquid crystal monomer comprises 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and / or 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene.

[0022] Preferably, the organic solvent includes toluene and / or xylene.

[0023] Preferably, the chain extender includes one or more of 1,6-hexanedithiol, 1,8-octanedithiol, 1,3-propanedithiol, and 2,2'-(1,2-ethylenedioxy)bis(ethyl)thiol.

[0024] Preferably, the crosslinking agent in the liquid crystal elastomer material includes trimethylolpropane tris(3-mercaptopropionate) and / or pentaerythritol tetra-3-mercaptopropionate.

[0025] Preferably, the catalyst comprises di-n-butylamine and / or triethylamine.

[0026] Preferably, the photoinitiator includes one or more of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, bisacylphosphine oxide, and 2-hydroxy-2-methylphenylacetone.

[0027] Furthermore, in step S1, the uniaxial stretching speed is 0.2 to 2 mm / s, and the elongation is 80% to 110%; the curing method is ultraviolet light curing.

[0028] Further, in step S2, the electrothermal / sensing ink comprises conductive nanomaterials and a binder, and the photothermal ink comprises photothermal nanomaterials and a binder; the binder comprises a block copolymer and an organic solvent. Preferably, in the binder, the mass ratio of the block copolymer to the organic solvent is 1:(2-4).

[0029] In this invention, a block copolymer is dissolved in an organic solvent as a binder, and conductive nanomaterials are mixed with the binder as conductive fillers and stirred continuously to obtain a uniformly dispersed electrothermal / sensing ink; photothermal nanomaterials are mixed with the binder as functional fillers and stirred continuously to obtain a uniformly dispersed photothermal ink. In step S2, an electrothermal / sensing ink with a solid content of 30wt.%-40wt.% refers to an electrothermal / sensing ink in which the mass fraction of conductive nanomaterials is 30wt.%-40wt.%; a photothermal ink with a solid content of 3wt.%-5wt.% refers to a photothermal ink in which the mass fraction of photothermal nanomaterials is 3wt.%-5wt.%.

[0030] Preferably, the conductive nanomaterial includes one or more of the following: silver nanowires, silver nanosheets, silver nanoparticles, dendritic silver, copper nanowires, and gold nanoparticles.

[0031] Preferably, the photothermal nanomaterial includes one or more of graphene, carbon nanotubes, Mxenes, and carbon black.

[0032] Preferably, the block copolymer includes styrene-isoprene-styrene block copolymer and / or hydrogenated styrene-butadiene block copolymer. Adding this type of elastomer to a solvent allows the formulated solvent-based ink to exhibit good adhesion to the substrate and between the two ink layers.

[0033] Preferably, the solvent includes xylene and / or toluene.

[0034] In this invention, the printing thickness of the two ink layers is controlled by controlling the number of printing layers, thereby controlling the deposition amount of functional material on the surface of the elastomer film. Preferably, the mesh count of the screen printing is 200-300 mesh.

[0035] In some preferred embodiments, in step S1, the liquid crystal monomer is preferably 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene, the organic solvent is preferably toluene, the chain extender is preferably 2,2'-(1,2-ethylenedioxy)bis(ethyl mercapto) mercaptoethanol, the crosslinking agent is preferably pentaerythritol tetra-3-mercaptopropionate, the catalyst is preferably di-n-butylamine, and the photoinitiator is preferably 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone. In the preparation of the electrothermal / sensing ink in step S2, the conductive filler is preferably dendritic silver, the block copolymer is preferably styrene-isoprene-styrene block copolymer, and the organic solvent is preferably xylene; in the preparation of the photothermal ink, the photothermal filler is preferably carbon black, the block copolymer is preferably styrene-isoprene-styrene block copolymer, and the organic solvent is preferably xylene.

[0036] Based on the above-preferred materials, a liquid crystal elastomer film and two functional inks were prepared. The liquid crystal elastomer film exhibited reversible shrinkage deformation under high-temperature stimulation, with shrinkage rates of 16.7%, 30.0%, and 36.7% at 80℃, 100℃, and 120℃, respectively. The electrothermal / sensing ink had a contact angle of 56° on the liquid crystal elastomer surface, and the photothermal ink had a contact angle of 49° on the electrothermal / sensing ink layer surface, both less than 90°, demonstrating good surface wettability. Furthermore, at a shear rate of 0.1 s⁻¹... -1 At that time, the viscosities of the electrothermal / sensing ink and the photothermal ink were 261.3 Pa s and 361.6 Pa s, respectively, which met the viscosity requirements for screen printing. With increasing shear rate, the viscosity of both inks decreased significantly, exhibiting shear-thinning properties, which facilitates ink deposition onto the substrate surface through the screen printing stencil.

[0037] Furthermore, in steps S3 and S4, the shape of the printing screen pattern used in screen printing includes a U-shaped pattern; during the printing process, the long side direction of the U-shaped pattern is consistent with the stretching direction of the uniaxial stretching in step S1, which can achieve better driving and sensing effects.

[0038] Further, in step S4, the line width of the printed pattern of the photothermal ink layer is consistent with that of the printed pattern of the electrothermal / sensing ink layer, but the length is shortened by 5-10 mm. During the printing process, the top edges of the printed pattern of the photothermal ink layer and the printed pattern of the electrothermal / sensing ink layer are aligned so that the photothermal ink layer completely covers the electrothermal / sensing ink layer. The photothermal ink layer is shortened in the length direction to provide wiring positions for current input and signal transmission.

[0039] Furthermore, in step S5, the solvent in the electrothermal / sensing ink layer and the photothermal ink layer is removed by drying. The drying temperature is 60-70°C and the time is 30-60 minutes.

[0040] The second objective of this invention is to provide a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function, wherein the liquid crystal elastomer actuator is prepared by the preparation method described in one of the objectives of this invention.

[0041] This invention utilizes a combination of liquid crystal elastomer and screen printing technology to fabricate a soft actuator with a multilayer structure possessing different functions. The actuator comprises a liquid crystal elastomer film, an electrothermal / sensing ink layer, and a photothermal ink layer. The liquid crystal elastomer film, when stimulated by temperature, contracts and deforms, forming the basis for the actuator's actuation. The electrothermal / sensing ink layer efficiently converts electrical energy into heat energy, achieving electrothermal actuation. Due to the good adhesion between the electrothermal / sensing ink layer and the liquid crystal elastomer, the ink layer contracts along with the liquid crystal elastomer when heated, increasing the number of contact sites for the conductive fillers and thus increasing the conductive pathways and reducing resistance. When the power is turned off, the liquid crystal elastomer film cools and returns to its initial state, and the resistance of the electrothermal / sensing ink layer also returns to its initial value. The electrothermal / sensing ink layer is crucial for realizing the actuator's electrothermal actuation and self-sensing functions. The photothermal ink layer effectively converts light energy into heat energy, stimulating the liquid crystal elastomer film to contract and actuate; this ink layer is an important component in achieving the actuator's photothermal actuation.

[0042] This invention cleverly utilizes the characteristic of liquid crystal elastomers to contract along the mechanical stretching direction during thermal deformation. The contraction of the liquid crystal elastomer drives the contraction of the printed layer, thereby generating a change in resistance. The generation and control of temperature are the basis for the actuator's driving and sensing functions. The two types of inks used in the printing process are capable of directly converting electricity and light into controllable heat, generating an adjustable stimulation temperature, enabling the liquid crystal elastomer to contract in a controlled manner. Simultaneously, the magnitude and stability of the contraction are fed back through the printed layer in the form of electrical signals.

[0043] In some preferred embodiments, the liquid crystal elastomer actuator can be heated to 64–91°C under different currents, producing a bending angle change of 42–102°, with a relative resistance change of -12.6%–-55.0% during movement; when subjected to near-infrared light of different intensities, it can be heated to 60–88°C, producing a bending angle change of 35–81°, with a relative resistance change of -9.9%–-31.1% during movement.

[0044] The third objective of this invention is to provide an application of a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function as described in the second objective of this invention in the fields of soft robots, wearable electronics and flexible actuators.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] (1) This invention provides a method for fabricating a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function. The method uses a single-domain liquid crystal elastomer film obtained by uniaxial stretching as a substrate. An electrothermal / sensing ink layer and a photothermal ink layer are sequentially deposited on the substrate surface using screen printing. By adjusting the solid content of the electrothermal / sensing ink and the photothermal ink, the total number of printed ink layers is adjusted to ensure the normal operation of electrothermal actuation and actuation sensing, thereby achieving the fabrication of a high-performance actuator. This invention employs a simple and efficient screen printing technique, using different types of functional inks to prepare a multi-layer printed structure. This method can not only quickly fabricate multi-stimulus response self-sensing actuators, but also conveniently fabricate soft actuators of different specifications.

[0047] (2) The liquid crystal elastomer actuator with multi-stimulus response and self-sensing function provided by the present invention, while not affecting the flexibility of the liquid crystal elastomer soft actuator, integrates optical and electrical stimulation response driving and highly sensitive self-sensing function. Under different current loading, it can be heated to 64-91°C, producing a bending angle change of 42-102°, and the relative resistance change during the movement is -12.6% to -55.0%; when loaded with different intensities of near-infrared light, it can be heated to 60-88°C, producing a bending angle change of 35-81°, and the relative resistance change during the movement is -9.9% to -31.1%. It has broad prospects for promotion and application in the fields of soft robots, wearable electronics and flexible actuators. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of the liquid crystal elastomer actuator with multi-stimulus response and self-sensing function prepared in Embodiment 1 of the present invention.

[0049] Figure 2 The images show the current, temperature, bending angle and relative resistance changes of the liquid crystal elastomer actuator prepared in Embodiment 1 of the present invention during the electric drive process (a), thermal infrared image (b), and photograph (c).

[0050] Figure 3 The images show the light intensity, temperature, bending angle, and relative resistance changes of the liquid crystal elastomer actuator prepared in Example 1 of this invention during the light driving process (a), thermal infrared image (b), and photograph (c). Detailed Implementation

[0051] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0053] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0054] Example 1

[0055] A method for fabricating a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function includes the following steps:

[0056] Step 1: Weigh 6g of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and add it to 1.86g of toluene solution. Heat to 80℃ and stir continuously until completely dissolved. Then, add 0.036g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, 1.44g of 2,2'-(1,2-ethylenedioxy)diethylthiol, 0.268g of pentaerythritol tetra-3-mercaptopropionate, and 0.864g of di-n-butylamine diluent (di-n-butylamine to toluene mass ratio 1:100). After uniform mixing, pour the mixture into a mold and place it in a dark environment at room temperature for 24 hours. Then, place it in a vacuum oven at 80℃ for 24 hours to obtain a multi-domain liquid crystal elastomer film. The multi-domain liquid crystal elastomer is uniaxially stretched (elongation 80%) and simultaneously cured under ultraviolet light for 30 minutes to obtain a single-domain liquid crystal elastomer film.

[0057] Step 2: First, prepare uniformly morphological dendritic silver. Dissolve 1.02 g of silver nitrate and 1.45 mL of hydroxylamine solution separately in 75 mL of deionized water. Add both solutions simultaneously to a three-necked flask using a double-headed peristaltic pump (40 rpm) while stirring. This will yield dendritic silver. Wash the flask three times with deionized water and anhydrous ethanol to obtain pure dendritic silver. Place the prepared dendritic silver in a vacuum oven at 60°C for 720 min to obtain dried dendritic silver for later use.

[0058] Step 3: Weigh 5g of styrene-isoprene-styrene block copolymer and dissolve it in 15g of xylene. Continue stirring until it is completely dissolved to form a styrene-isoprene-styrene block copolymer solution for later use.

[0059] Step 4: Weigh 1g of dendritic silver and 1.5g of styrene-isoprene-styrene block copolymer solution and stir continuously for 20min to prepare an electrothermal / sensing ink based on dendritic silver (solid content of 40wt.%).

[0060] Step 5: Weigh 0.05g of carbon black and 0.95g of styrene-isoprene-styrene block copolymer solution and stir continuously for 15min to prepare carbon black-based photothermal ink (solid content is 5wt.%).

[0061] Step 6: Using a 300-mesh screen printing plate, first deposit electrothermal / sensing ink onto the liquid crystal elastomer film substrate, then deposit photothermal ink onto the surface of the electrothermal / sensing ink layer. The electrothermal / sensing ink has 3 deposition layers, and the photothermal ink has 1 deposition layer. During screen printing, the long side of the U-shaped pattern is aligned with the stretching direction of the uniaxial stretching in step S1; the linewidth of the printed pattern in the photothermal ink layer is consistent with the linewidth of the printed pattern in the electrothermal / sensing ink layer, but the length of the photothermal ink printed pattern is slightly shorter than the electrothermal / sensing ink printed pattern by 5 mm to provide wiring positions for current input and signal transmission. The printed electronic device is dried at 70°C for 45 minutes to obtain a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function.

[0062] Figure 1 This is a schematic diagram of the structure of the liquid crystal elastomer actuator with multi-stimulus response and self-sensing function prepared in Embodiment 1 of the present invention. Figure 1 It can be seen that the liquid crystal elastomer actuator comprises, from bottom to top, a liquid crystal elastomer film, an electrothermal / sensing ink layer, and a photothermal ink layer.

[0063] Figure 2 The images show (a), thermal infrared image (b), and photograph (c) of the liquid crystal elastomer actuator prepared in Embodiment 1 of the present invention, illustrating the changes in current, temperature, bending angle, and relative resistance during electrical driving. Figure 2 It can be seen that the actuator obtained in this embodiment can achieve saturation temperatures of 64°C, 81°C and 91°C when 100mA, 150mA and 200mA currents are applied, respectively, and the maximum bending angles are 42°, 82° and 102°, respectively. The corresponding maximum relative resistance changes generated during the motion process can reach -12.6%, -36.3% and -55.0%, respectively.

[0064] Figure 3 The images show (a), thermal infrared image (b), and photograph (c) of the liquid crystal elastomer actuator prepared in Example 1 of this invention, illustrating the changes in light intensity, temperature, bending angle, and relative resistance during light-driven operation. Figure 3 It can be seen that applying 1.12 W / cm to the obtained actuator 2 1.22W / cm 2 1.33W / cm 2 and 1.43W / cm 2 The saturation temperatures of the 808nm near-infrared light reached 60℃, 71℃, 81℃ and 88℃, respectively, and the maximum bending angles were 35°, 49°, 67° and 81°, respectively. The corresponding maximum relative resistance changes during the motion were -9.9%, -15.6%, -27.7% and -31.1%, respectively.

[0065] Example 2

[0066] A method for fabricating a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function includes the following steps:

[0067] Step 1: Weigh 11.5g of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene and add it to 3.57g of toluene solution. Heat to 80℃ and stir continuously until completely dissolved. Then, add 0.074g of 2-hydroxy-2-methylphenylacetone, 2.477g of 2,2'-(1,2-ethylenedioxy)diethylthiol, 0.083g of pentaerythritol tetra-3-mercaptopropionate, and 0.036g of di-n-butylamine diluent (di-n-butylamine to toluene mass ratio 1:100). After uniform mixing, pour the mixture into a mold and place it in a dark environment at room temperature for 24 hours. Then, place it in a vacuum oven at 85℃ for 12 hours to obtain a multi-domain liquid crystal elastomer film. The multi-domain liquid crystal elastomer is uniaxially stretched (elongation 110%) and simultaneously cured under ultraviolet light for 30 minutes to obtain a single-domain liquid crystal elastomer film.

[0068] Step 2: Weigh 5g of styrene-isoprene-styrene block copolymer and dissolve it in 15g of xylene. Continue stirring until it is completely dissolved to form a styrene-isoprene-styrene block copolymer solution for later use.

[0069] Step 3: Weigh 1.5g of silver nanosheets and 3.5g of styrene-isoprene-styrene block copolymer solution and stir continuously for 20min to prepare an electrothermal / sensing ink based on silver nanosheets (solid content of 30wt.%).

[0070] Step 4: Weigh 0.05g of carbon nanotubes and 0.95g of styrene-isoprene-styrene block copolymer solution and stir continuously for 15min to prepare a photothermal ink based on carbon nanotubes (solid content is 5wt.%).

[0071] Step 5: Using a 300-mesh screen printing plate, first deposit electrothermal / sensing ink onto the liquid crystal elastomer film substrate, then deposit photothermal ink onto the surface of the electrothermal / sensing ink layer. The electrothermal / sensing ink has 4 deposition layers, and the photothermal ink has 1 deposition layer. During screen printing, the long side of the U-shaped pattern is aligned with the stretching direction of the uniaxial stretching in step S1; the linewidth of the printed pattern in the photothermal ink layer is consistent with the linewidth of the printed pattern in the electrothermal / sensing ink layer, but the length of the photothermal ink printed pattern is slightly shorter than the electrothermal / sensing ink printed pattern by 5 mm to provide wiring positions for current input and signal transmission. The printed electronic device is dried at 60°C for 60 minutes to obtain a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function.

[0072] Example 3

[0073] A method for fabricating a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function includes the following steps:

[0074] Step 1: Weigh 1g of 1,4-bis-[4-(3-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene and add it to 0.31g of toluene solution. Heat to 80℃ and stir continuously until completely dissolved. Then, add 0.006g of bisacylphosphine oxide, 0.24g of 2,2'-(1,2-ethylenedioxy)diethylthiol, 0.048g of pentaerythritol tetra-3-mercaptopropionate, and 0.144g of di-n-butylamine diluent (di-n-butylamine to toluene mass ratio 1:100) sequentially. After uniform mixing, pour the mixture into a mold and place it in a dark environment at room temperature for 24 hours. Then, place it in a vacuum oven at 80℃ for 24 hours to obtain a multi-domain liquid crystal elastomer film. The multi-domain liquid crystal elastomer is uniaxially stretched (100% elongation) and simultaneously cured under ultraviolet light for 30 minutes to obtain a single-domain liquid crystal elastomer film.

[0075] Step 2: Weigh 5g of styrene-isoprene-styrene block copolymer and dissolve it in 15g of xylene. Continue stirring until it is completely dissolved to form a styrene-isoprene-styrene block copolymer solution for later use.

[0076] Step 3: Weigh 1.8g of copper nanowires and 3.2g of styrene-isoprene-styrene block copolymer solution and stir continuously for 20min to prepare an electrothermal / sensing ink based on copper nanowires (solid content of 36wt.%).

[0077] Step 4: Weigh 0.04g of carbon black and 0.96g of styrene-isoprene-styrene block copolymer solution and stir continuously for 15min to prepare carbon black-based photothermal ink (solid content is 4wt.%).

[0078] Step 5: Using a 250-mesh screen printing plate, first deposit electrothermal / sensing ink onto the liquid crystal elastomer film substrate, then deposit photothermal ink onto the surface of the electrothermal / sensing ink layer. The electrothermal / sensing ink has 3 deposition layers, and the photothermal ink has 2 deposition layers. During screen printing, the long side of the U-shaped pattern is aligned with the stretching direction of the uniaxial stretching in step S1; the linewidth of the printed pattern in the photothermal ink layer is consistent with the linewidth of the printed pattern in the electrothermal / sensing ink layer, but the length of the photothermal ink printed pattern is slightly shorter than the electrothermal / sensing ink printed pattern by 5 mm to provide wiring positions for current input and signal transmission. The printed electronic device is dried at 65°C for 50 minutes to obtain a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function.

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for preparing a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function, characterized in that, Includes the following steps: S1. A multi-domain liquid crystal elastomer film is simultaneously subjected to uniaxial stretching and curing to obtain a single-domain liquid crystal elastomer film; the uniaxial stretching speed is 0.2-2 mm / s, and the elongation is 80%-110%; the curing method is ultraviolet light curing. S2. Prepare electrothermal / sensing inks with a solid content of 30 wt.%-40 wt.% and photothermal inks with a solid content of 3 wt.%-5 wt.% respectively; the electrothermal / sensing inks include conductive nanomaterials and binders, and the photothermal inks include photothermal nanomaterials and binders; the binders include block copolymers and organic solvents; the block copolymers include styrene-isoprene-styrene block copolymers and / or hydrogenated styrene-butadiene block copolymers; the organic solvents include xylene and / or toluene; S3. The electrothermal / sensing ink is deposited on the surface of the single-domain liquid crystal elastomer film by screen printing, with 2-4 layers deposited to form an electrothermal / sensing ink layer. S4. The photothermal ink is deposited on the surface of the electrothermal / sensing ink layer by screen printing, with 1-2 layers deposited to form a photothermal ink layer; in the screen printing of steps S3 and S4, the printing screen pattern includes a U-shaped pattern, and the long side direction of the U-shaped pattern is consistent with the stretching direction of the uniaxial stretching in step S1; the line width of the printed pattern of the photothermal ink layer is consistent with that of the printed pattern of the electrothermal / sensing ink layer, and the length is shortened by 5-10mm; S5. Remove the solvent from the electrothermal / sensing ink layer and the photothermal ink layer to obtain a liquid crystal elastomer actuator with a multilayer composite structure.

2. The preparation method according to claim 1, characterized in that, In step S1, the preparation method of the multi-domain liquid crystal elastomer film includes: dissolving liquid crystal monomers in an organic solvent to obtain a mixed solution; adding chain extender, crosslinking agent, catalyst, and photoinitiator to the mixed solution, mixing well, injecting into a mold, and reacting for a certain time to obtain a multi-domain liquid crystal elastomer film.

3. The preparation method according to claim 1, characterized in that, The conductive nanomaterials include one or more of silver nanowires, silver nanosheets, silver nanoparticles, dendritic silver, copper nanowires, and gold nanoparticles; the photothermal nanomaterials include one or more of graphene, carbon nanotubes, Mxenes, and carbon black.

4. The preparation method according to claim 1, characterized in that, In step S5, the solvent in the electrothermal / sensing ink layer and the photothermal ink layer is removed by drying. The drying temperature is 60-70℃ and the time is 30-60min.

5. A liquid crystal elastomer actuator with multi-stimulus response and self-sensing function, characterized in that, The liquid crystal elastomer actuator is prepared by the preparation method according to any one of claims 1-4.

6. The application of a liquid crystal elastomer actuator with multi-stimulus response and self-sensing function as described in claim 5 in the fields of soft robotics, wearable electronics and flexible actuators.

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