Light-heat-humidity flexible driver of variable-spacing microstructure and preparation method thereof

Abstract

The invention provides a light-heat-humidity flexible driver of a variable-spacing microstructure and a preparation method thereof.The light-heat-humidity flexible driver of the variable-spacing microstructure comprises an active layer and a passive layer, the active layer is a PDMS / CNTs composite film, the passive layer is a chitosan film, the passive layer is arranged on the upper surface of the active layer, and the active layer is a PDMS / CNTs composite film. The lower surface of the active layer is provided with a groove structure. The groove structure is engraved in the active layer, and the deformation capacity of the actuator can be enhanced by constructing the groove structure. By means of the structural design, deformation is more concentrated, and therefore the working efficiency and the response speed of the driver are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible actuators, and relates to a light-heat-moisture flexible actuator with a variable pitch microstructure and a preparation method thereof. Background Art

[0002] Traditional actuators are based on combining actuating materials with rigid components of simple mechanical design to achieve translation and rotation. However, rigid actuation systems cannot achieve bending, have poor adaptability, and are difficult to apply to complex scenarios in the future. Flexible actuators can convert energy in the form of external stimuli such as humidity, temperature, light, and chemicals into mechanical motion. Among different types of deformation, stretching and torsional actuation are basic deformations that can be used to construct other types of actuation, such as bending, curling, rolling, jumping, etc. Therefore, the inevitable development path is from hard and rigid structures to soft and flexible systems.

[0003] In the early 1990s, MEMS technology developed rapidly, and the manufacturing technology of flexible microactuators also improved. In 1992, researchers at the University of California, Berkeley first proposed the concept of flexible microactuators and successfully manufactured a silicon-based microactuator. In recent years, with the further maturity of MEMS technology, the application scope of flexible microactuators has been expanding. For example, in the medical field, flexible microactuators are widely used in medical devices such as endoscopes and drug delivery devices, making surgical operations easier and more precise. In the field of robotics, flexible microactuators can be used to manufacture bionic robots, simulate the movement of human muscles, and achieve more natural human-computer interaction. Research on flexible actuators, especially flexible actuators that respond to stimuli such as light, heat, and humidity, or flexible actuators with double-layer structures. When the size of the actuator reaches the micron level, the scaling ratio of the actuator is limited, and the perception source of the actuator is single, which is not suitable for actual environments with complex factors. Therefore, a variable spacing microstructure actuator based on multiple responses of light, humidity and heat is developed to meet the needs of flexible mechanical deformation in different environments.

[0004] At present, micro actuators are mainly realized through mechanical, electromagnetic or piezoelectric principles. However, these actuators are not only expensive, but also have problems such as large size and low power density. In recent years, micro flexible actuators based on physical phenomena such as light, water, and heat have gradually attracted people's attention. The material of the actuator can change the shape, stiffness, position, natural frequency, damping or other mechanical properties of the material itself in response to changes in temperature, electric field and magnetic field. At the same time, when the size of the actuator is reduced to less than cubic centimeters, its actuation scaling is greatly limited. At present, high-efficiency micro actuators are still in the early stage of development. Due to the lack of suitable micron-level actuator systems, the further development of micro robotics technology has been greatly restricted. In addition, intelligent systems driven by green energy in nature are a major trend in the efficient use of energy in the future. However, most traditional actuation materials are triggered by a single stimulus, which is not suitable for actual environments with complex factors and cannot meet the needs of future actuation. Therefore, it is necessary to design a micro brake that can respond to stimuli in a complex environment. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a photothermal and moisture flexible actuator with a variable pitch microstructure and a preparation method thereof, which can convert environmental stimuli in the form of light, heat and humidity into mechanical energy in a natural environment, so that the actuator produces mechanical deformation; at the same time, a groove-type structure is prepared on the surface of the active layer, and a bulge will be generated on the top when mechanical deformation occurs. The spacing angle of the groove can be changed, thereby enhancing the deformation effect.

[0006] The technical solution adopted by the present invention is:

[0007] A light-heat-moisture-flexible actuator with a variable pitch microstructure includes an active layer and a passive layer, wherein the active layer is a PDMS / CNTs composite film, the passive layer is a chitosan film, the passive layer is arranged on the upper surface of the active layer, and a groove structure is arranged on the lower surface of the active layer. The present invention depicts a groove structure in the active layer, and by constructing the groove structure, the deformation ability of the actuator can be enhanced. This structural design makes the deformation more concentrated, thereby improving the working efficiency and response speed of the actuator.

[0008] Furthermore, the groove structures are arranged at equal intervals.

[0009] Alternatively, the groove structures are arranged at unequal intervals.

[0010] Furthermore, the groove structure is arranged to be inclined, and the inclination angle ranges from 15° to 60°.

[0011] Furthermore, the upper surface of the PDMS / CNTs composite film is plasma treated.

[0012] Furthermore, the PDMS / CNTs composite film is a film formed by dissolving the PDMS / CNTs composite in a cyclohexane solution and then curing it.

[0013] Furthermore, the chitosan film is a film formed by curing a chitosan mixed with acetic acid solution.

[0014] A method for preparing a photothermal and wet flexible actuator with a variable pitch microstructure, the specific steps of which are as follows:

[0015] S1, using a laser to micro-process the PET film to form a groove structure on the surface of the PET film;

[0016] S2, add cyclohexane into a beaker, add multi-walled CNTs powder, PDMS solvent, and PDMS curing agent into the cyclohexane in sequence, and stir evenly each time, and evenly apply the prepared solution on the PET film prepared in step S1 and heat to dry and solidify;

[0017] S3, peeling off the heated and dried PDMS-CNT composite film and subjecting the surface without the groove structure to plasma treatment, and placing it in the PET film with a hollow in the middle;

[0018] S4, mixing chitosan powder in acetic acid solution, stirring evenly, applying it on the plasma-treated surface of the PDMS-CNT composite film, and drying and curing it to form a photothermal and wet flexible actuator;

[0019] S5, cutting and micro-machining the prepared photothermal and wet flexible actuator according to the set angle.

[0020] Further, the specific operation of step S2 is as follows: add 1.2ml-3ml of cyclohexane (HPLC, ≥99.9%) into a beaker, weigh 0.012-0.03g of multi-walled CNTs powder, mix, stir evenly, place in an ultrasonic machine for ultrasonication for 1 hour, then add 1.5-2.5ml of PDMS solvent, stir evenly, place in an ultrasonic machine for ultrasonication for 1 hour again, add 0.15-0.25ml of PDMS curing agent (the amount of PDMS to PDMS curing agent is 10:1); use a glass rod to evenly apply the prepared solution on the PET film with a groove structure, and heat at 60°C for four hours.

[0021] Furthermore, the specific operation of step S4 is as follows: 35-45 mg of chitosan powder is mixed in 3.5-4.5 ml of acetic acid solution, stirred evenly, applied on the surface to be treated with plasma, and left to dry overnight.

[0022] The beneficial effects of the present invention are as follows: it can sensitively capture three stimuli, namely light, temperature and humidity, and make efficient bending feedback; it can also make bending feedback in its composite environment, and the required stimulus source can be selected according to actual needs through the different bending performances fed back under different single stimuli and composite stimuli. The groove structure can change the spacing angle of the groove according to different needs while improving the braking performance of the driver, so as to cope with its application in soft robots, flexible grippers, etc., and enable the driver to have complex motion modes. The actuating material can be replaced with other flexible materials, and the actuating characteristics such as material type, actuating structure and material concentration can be adjusted according to different natural environments, braking performance and braking requirements to adapt to different needs, further enhancing the environmental adaptability of the driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the three-dimensional structure with equal spacing of the present invention.

[0024] Figure 2 It is a schematic diagram of the three-dimensional structure with equal spacing of the present invention.

[0025] Figure 3 It is a schematic diagram of the three-dimensional structure with equal spacing of the present invention.

[0026] Figure 4 This is a comparison diagram of the deformation effects of the present invention and the full-filling structure under the same environment.

[0027] Figure 5 This is a schematic diagram of the equal spacing of the groove structure during the production of the present invention.

[0028] Figure 6 This is a schematic diagram of the unequal spacing of the groove structure during the production of the present invention.

[0029] Figure 7 It is a schematic structural diagram of the groove structure with different spacings of the present invention.

[0030] Figure 8 It is a schematic diagram of the structure of different cutting angles of the present invention.

[0031] Fig. 9 It is a schematic diagram of the mechanical deformation of the present invention in a heating environment.

[0032] Fig.10 It is a schematic diagram of the deformation of the present invention in a light-heat coordinated environment.

[0033] Fig.11 It is a deformation schematic diagram of the present invention in a heat and moisture coordinated environment. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more, unless otherwise clearly defined.

[0036] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0038] Explanation of terms

[0039] Flexible actuators are devices that can convert various forms of environmental stimuli such as light, temperature, humidity, pressure, pH value, electricity, magnetism, and chemical effects into mechanical work. Flexible actuators are an important component of soft robots and wearable devices. Flexible actuators are used in soft robots to achieve safe and reliable human-machine interaction. Flexible actuators can simulate the expansion and contraction characteristics of muscles and are used in the design of artificial muscles. Flexible actuators integrate perception, signal transmission and control functions and are used in advanced intelligent systems. They can be used in biomedical devices such as flexible electronic skin. Flexible actuators can also be used to develop energy storage devices such as flexible batteries and supercapacitors. Flexible actuators mainly receive external stimuli and use special structures or materials to produce changes in volume size and shape style to produce reversible movements such as moving or shaping, and achieve functions such as bending, grasping, and moving.

[0040] Inspired by nature, researchers around the world have been trying to develop various types of actuators that can generate driving forces and trigger material deformation through stimulation methods such as temperature, humidity, pH, light, electricity, and magnetism. According to different response factors, actuators can be roughly divided into thermal response actuators, humidity response actuators, light response actuators, electric response actuators, and magnetic response actuators. Some actuators have multiple response sources and can respond to multiple stimulation methods. Therefore, according to the number of response factors, actuators can be divided into single stimulus response actuators and multiple stimulus response actuators. According to the structural type, actuators can also be divided into thin film structure actuators, fibrous structure actuators, and cavity structure actuators. For a special type of hierarchical structure actuator, it can also be divided into single-layer actuators, double-layer actuators, and gradient structure actuators according to the number of layers.

[0041] Carbon nanotube (CNT) was discovered in January 1991 by Sumio Iijima, a physicist at the NEC Laboratory in Tsukuba, Japan, using a high-resolution transmission electron microscope from the product of arc-produced carbon fibers. It is a tubular carbon molecule, in which each carbon atom on the tube adopts sp2 hybridization and is bonded to each other by carbon-carbon σ bonds, forming a honeycomb structure composed of hexagons as the skeleton of the carbon nanotube. A pair of p electrons on each carbon atom that do not participate in hybridization form a conjugated π electron cloud that spans the entire carbon nanotube. According to the number of layers of the tube, it is divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. The radius of the tube is very thin, only nanometers, and tens of thousands of carbon nanotubes are only as wide as a hair, hence the name of carbon nanotubes. In the axial direction, it can be tens to hundreds of microns long. Carbon nanotubes are not always straight, and local bumps may appear, which is due to the mixing of pentagons and heptagons in the hexagonal structure. Where the pentagon appears, the carbon nanotube bulges outward due to tension. If the pentagon appears at the top of the carbon nanotube, it forms a seal for the carbon nanotube. Where the heptagon appears, the carbon nanotube is concave inward. The hardness of carbon nanotubes is comparable to that of diamonds, but they have good flexibility and can be stretched. In the reinforced fibers currently used in industry, a key factor that determines the strength is the aspect ratio, that is, the ratio of length to diameter. At present, material engineers hope to obtain an aspect ratio of at least 20:1, while the aspect ratio of carbon nanotubes is generally above 1000:1, which is an ideal high-strength fiber material. At the same time, it has a very large aspect ratio, so its heat exchange performance along the length direction is very high, and its heat exchange performance in the vertical direction is relatively low. Through appropriate orientation, carbon nanotubes can be synthesized into highly anisotropic thermal conductive materials. In addition, carbon nanotubes have a high thermal conductivity. As long as a trace amount of carbon nanotubes is doped in the composite material, the thermal conductivity of the composite material will be greatly improved. Compared with traditional optoelectronic materials, CNT has excellent light absorption and light response properties. CNT is a multi-subband, direct bandgap semiconductor with adjustable bandgap, which is roughly inversely proportional to the diameter. Therefore, CNT film has a wide spectrum of light absorption characteristics from ultraviolet to infrared. In general, the response factors of CNT are mainly temperature, light and electrical signals, which provides material support for the preparation of actuators with thermal response, photothermal response, electrical response and multiple stimulus response.

[0042] Chitosan is the product of N-deacetylation of chitin. Chitin (chitin), chitosan and cellulose have similar chemical structures. Cellulose has a hydroxyl group at the C2 position, while chitin and chitosan are replaced by an acetylamino group and an amino group at the C2 position, respectively. Chitin and chitosan have many unique properties such as biodegradability, cell affinity and biological effects. In particular, chitosan containing free amino groups is the only alkaline polysaccharide among natural polysaccharides. The amino group in the chitosan molecular structure is more reactive than the acetylamino group in the chitin molecule, which makes the polysaccharide have excellent biological functions and can undergo chemical modification reactions. Therefore, chitosan is considered to be a functional biomaterial with greater application potential than cellulose. After dissolution, chitosan is in a gel state and has a strong adsorption capacity. Chitosan contains polar groups such as hydroxyl and amino groups, and has strong hygroscopicity. The moisture absorption rate of chitin can reach 400%-500%, which is more than twice that of cellulose. The hygroscopicity of chitosan is stronger than that of chitin. Chitosan film can absorb water and swell through the cross-linked structure. Therefore, it is widely used in many fields such as food additives, textiles, agriculture, environmental protection, beauty and health care, cosmetics, antibacterial agents, medical fibers, medical dressings, artificial tissue materials, drug sustained-release materials, gene transduction vectors, biomedical fields, medical absorbable materials, tissue engineering carrier materials, medical and drug development, and other daily chemical industries.

[0043] Embodiment 1

[0044] See also Figure 1 This embodiment provides a light-heat-moisture flexible actuator with a variable pitch microstructure, including an active layer 1 and a passive layer 2, wherein the active layer 1 is a PDMS / CNTs composite film, the passive layer 2 is a chitosan film, the passive layer 2 is arranged on the upper surface of the active layer 1, and a groove structure 3 is arranged on the lower surface of the active layer 1. The present invention depicts the groove structure 3 on the active layer 1, and by constructing the groove structure, the deformation ability of the actuator can be enhanced. This structural design makes the deformation more concentrated, thereby improving the working efficiency and response speed of the actuator.

[0045] See also Figure 4 Compared with the fully filled film, the film with groove structure: by constructing the groove structure to enhance the deformation effect, the driving force of the actuator is enhanced. At the same time, by constructing the groove structure, the deformation ability of the actuator can be significantly enhanced. This structural design makes the deformation more concentrated, thereby improving the working efficiency and response speed of the driver. For example, in the application of multi-legged crawling robots, the two-degree-of-freedom joints composed of the groove structure can greatly enhance the robot's movement energy. In the design of multi-arm grippers, according to the magnetic arrangement design, this gripper can be folded under the magnetic field to realize the function of grasping and releasing objects.

[0046] The groove structures 3 in this embodiment are arranged at equal intervals. Of course, the groove structures 3 can also be arranged at unequal intervals, such as Figure 2 As shown. The ratio of the height to the width of the groove structure is between 0.1-2.0. The groove structure 3 can be set to be inclined according to the needs, such as Figure 3 As shown, the tilt angle range is 15°-60°.

[0047] The upper surface of the PDMS / CNTs composite film described in this embodiment was plasma treated.

[0048] The PDMS / CNTs composite film described in the present embodiment is a film formed by curing after the PDMS / CNTs composite is dissolved by a cyclohexane solution, and the film thickness is about 0.1mm. The PDMS / CNTs film has a good light-to-heat conversion efficiency. At the same time, due to the ultra-high thermal expansion coefficient and strong stretchability of the PDMS material, carbon nanotubes (CNT) are a nano-scale tubular structure material composed of carbon atoms, with excellent mechanical properties, and their elastic modulus and tensile strength can reach 1000GPa and 100GPa or more, respectively. In addition, CNT also has extremely high flexibility and durability. CNT also possesses good optical properties and thermal conductivity at the same time. CNT possesses the absorption capacity of ultraviolet, visible light and infrared bands and excellent light absorption and light response performance.

[0049] The chitosan film described in this embodiment is a film formed by curing chitosan mixed with acetic acid solution, and the film thickness is about 0.1 mm. The chitosan film can absorb water and expand through the cross-linked structure, so the present invention has triple response stimulation of light, heat, temperature and humidity.

[0050] The variable spacing microstructure light-heat-moisture flexible actuator of the present invention is an inorganic composite double-layer structure based on PDMS / CNTs and chitosan, with a diameter of 1 cm, a width of 0.1 mm, a thickness of 0.2 mm, and a total volume of 0.2 mm. 3 of the drive.

[0051] In the present invention, when there is no light and only heating stimulation, the actuator is in a bent state, such as Fig. 9 As shown; when light stimulation is performed under the same temperature environment, the bending angle gradually increases, as shown Fig.10 As shown; Under the same temperature environment, when wet stimulation is given at the same time, it is found that the bending angle is getting smaller. This is because the chitosan film located on the upper layer can respond to humidity stimulation, while the PDMS / CNTs film located on the lower layer is an inert layer that cannot respond to humidity stimulation, so it will cause the film to bend. However, since the bending performance of the film under thermal stimulation is much greater than that under wet stimulation, the bending angle becomes smaller, as shown in Fig.11 When the actuator is taken out of the stimulating environment, it will stretch back to its initial state.

[0052] The present invention can make the driver suitable for deformation requirements in different natural environments. Due to the characteristics of the selected materials, the driver can produce mechanical deformation in three environments of light, moisture and heat respectively. It can also produce mechanical deformation requirements under the stimulation of light-heat, light-humidity, heat-humidity, light-heat-humidity and other composite environments. At the same time, it can also fit the corresponding environment according to its different deformation properties. The groove structure depicted can meet the needs of realizing complex motion modes. In the design of the multi-arm gripper, according to the magnetic arrangement design, this gripper can be folded under the magnetic field to realize the function of grasping and releasing objects. At the same time, its structural size is only 0.2mm 3 , with the advantages of small size and light weight.

[0053] Embodiment 2

[0054] This embodiment provides a method for preparing a light-heat-moisture-flexible actuator with a variable pitch microstructure, and the specific steps are as follows:

[0055] S1, using LPKF laser to micro-process PET film with a thickness of 0.1 mm, forming a groove structure on the surface of the PET film; the PET film mold with equal spacing is shown in Figure 5 As shown, the unequal spacing PET film mold is shown Figure 6 As shown;

[0056] S2, add cyclohexane into a beaker, add multi-walled CNTs powder, PDMS solvent, and PDMS curing agent into the cyclohexane in sequence, and stir evenly each time, and evenly apply the prepared solution on the PET film prepared in step S1 and heat to dry and solidify;

[0057] Specifically, 1.2 ml to 3 ml of cyclohexane (HPLC, ≥99.9%) is added to a beaker, and 0.012-0.03 g of multi-walled CNTs powder is weighed and mixed, stirred evenly, and placed in an ultrasonic machine for ultrasonication for 1 hour, then 1.5-2.5 ml of PDMS solvent is added, stirred evenly, and placed in an ultrasonic machine for ultrasonication for 1 hour, and 0.15-0.25 ml of PDMS curing agent is added (the amount of PDMS to PDMS curing agent is 10:1); the prepared solution is evenly applied to the grooved PET film using a glass rod, and heated at 60°C for four hours.

[0058] Preferably, in this embodiment, 1.65 ml of cyclohexane is added to a beaker, and 0.016 g of multi-walled CNTs powder is weighed and mixed, stirred evenly, placed in an ultrasonic machine for ultrasonication for 1 hour, and then 1.875 ml of PDMS solvent is added, stirred evenly, placed in an ultrasonic machine for ultrasonication for 1 hour again, and 0.1875 ml of PDMS curing agent is added; the prepared solution is evenly applied to the PET film with a groove structure using a glass rod, and heated at 60°C for four hours.

[0059] S3, peeling off the heated and dried PDMS-CNT composite film and subjecting the surface without the groove structure to plasma treatment for 60 seconds, and placing it in a PET film with a hollow center and a thickness of 0.2 mm;

[0060] S4, chitosan powder is mixed in acetic acid solution, stirred evenly, applied on the plasma-treated surface of the PDMS-CNT composite film, and dried and cured to form a photothermal and wet flexible actuator; see Figure 7 shown.

[0061] Specifically, 35-45 mg of chitosan powder is mixed in 3.5-4.5 ml of acetic acid solution, stirred evenly, applied to the surface to be treated with plasma, and left to dry overnight.

[0062] In this embodiment, 40 mg of chitosan powder was mixed in 4 ml of acetic acid solution, stirred evenly, applied to the surface to be treated with plasma, and left to dry overnight.

[0063] S5, the prepared photothermal and wet flexible actuator is cut and micro-processed according to the set angle to obtain micro photothermal and wet flexible actuators with different structures, see Figure 8 shown.

[0064] The present invention can sensitively capture three stimuli, namely light, temperature and humidity, and make efficient bending feedback; it can also make bending feedback in its composite environment, and can select the required stimulus source according to actual needs through the different bending performances fed back under different single stimuli and composite stimuli. The groove structure can change the spacing angle of the groove according to different needs while improving the braking performance of the driver, so as to cope with its application in soft robots, flexible grippers, etc., and enable the driver to have complex motion modes. The actuating material can be replaced with other flexible materials, and the actuating characteristics such as material type, actuating structure and material concentration can be adjusted according to different natural environments, braking performance and braking requirements to adapt to different needs, further enhancing the environmental adaptability of the driver.

Claims

1. A light-heat-moisture-flexible actuator with a variable pitch microstructure, comprising an active layer and a passive layer, characterized in that: The active layer is a PDMS / CNTs composite film, the passive layer is a chitosan film, the passive layer is arranged on the upper surface of the active layer, and a groove structure is arranged on the lower surface of the active layer.

2. The optical-thermal-wet flexible actuator with variable pitch microstructure according to claim 1, characterized in that: The groove structures are arranged at equal intervals.

3. The optical-thermal-wet flexible actuator with variable pitch microstructure according to claim 1, characterized in that: The groove structures are arranged at unequal intervals.

4. The optical-thermal-wet flexible actuator with variable pitch microstructure according to claim 1, characterized in that: The groove structure is arranged to be inclined, and the inclination angle ranges from 15° to 60°.

5. The optical-thermal-wet flexible actuator with variable pitch microstructure according to claim 1, characterized in that: The upper surface of the PDMS / CNTs composite film is plasma treated.

6. The optical-thermal-wet flexible actuator with variable pitch microstructure according to claim 1, characterized in that: The PDMS / CNTs composite film is a film formed by curing the PDMS / CNTs composite after it is dissolved in a cyclohexane solution.

7. The optical-thermal-wet flexible actuator with variable pitch microstructure according to claim 1, characterized in that: The chitosan film is a film formed by curing a chitosan mixed with acetic acid solution.

8. A method for preparing a photothermal and wet flexible actuator with a variable pitch microstructure, the specific steps of which are as follows: S1, using a laser to micro-process the PET film to form a groove structure on the surface of the PET film; S2, add cyclohexane into a beaker, add multi-walled CNTs powder, PDMS solvent, and PDMS curing agent into the cyclohexane in sequence, and stir evenly each time, and evenly apply the prepared solution on the PET film prepared in step S1 and heat to dry and solidify; S3, peeling off the heated and dried PDMS-CNT composite film and subjecting the surface without the groove structure to plasma treatment, and placing it in the PET film with a hollow in the middle; S4, mixing chitosan powder in acetic acid solution, stirring evenly, applying it on the plasma-treated surface of the PDMS-CNT composite film, and drying and curing it to form a photothermal and wet flexible actuator; S5, cutting and micro-machining the prepared photothermal and wet flexible actuator according to the set angle.

9. The method for preparing a light-heat-moisture-flexible actuator with a variable pitch microstructure according to claim 8, characterized in that: The specific operation of step S2 is as follows: add 1.2ml-3ml of cyclohexane to a beaker, weigh 0.012-0.03g of multi-walled CNTs powder, mix, stir evenly, place in an ultrasonic machine for ultrasonication for 1 hour, then add 1.5-2.5ml of PDMS solvent, stir evenly, place in an ultrasonic machine for ultrasonication for 1 hour again, add 0.15-0.25ml of PDMS curing agent; use a glass rod to evenly apply the prepared solution on the PET film with the groove structure, and heat at 60°C for four hours.

10. The method for preparing a light-heat-moisture-flexible actuator with a variable pitch microstructure according to claim 8, characterized in that: The specific operation of step S4 is as follows: 35-45 mg of chitosan powder is mixed in 3.5-4.5 ml of acetic acid solution, stirred evenly, applied on the surface to be treated with plasma, and left to dry overnight.

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