Optothermo-hydroelastic driver of variable pitch microstructure and method of making same

Abstract

The application provides a variable-pitch microstructure photothermal wet flexible driver and a preparation method thereof, wherein the variable-pitch microstructure photothermal wet flexible driver 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 lower surface of the active layer is provided with a groove structure. The groove structure is engraved on the active layer, and the deformation capacity of the actuator can be enhanced by constructing the groove structure. The structure design makes the deformation more concentrated, and thus the working efficiency and response speed of the driver are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flexible actuators, and relates to a photo-thermal-humidity flexible actuator with variable pitch microstructure and a preparation method thereof. BACKGROUND

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

[0003] In the early 1990s, MEMS technology developed rapidly, and flexible micro-actuator manufacturing technology also improved. In 1992, researchers at the University of California, Berkeley, first proposed the concept of flexible micro-actuators and successfully manufactured a silicon-based micro-actuator. In recent years, with the further maturity of MEMS technology, the application range of flexible micro-actuators has also been expanding. For example, in the medical field, flexible micro-actuators are widely used in medical equipment such as endoscopes and drug delivery devices, making surgical operations more convenient and accurate. In the field of robotics, flexible micro-actuators can be used in the manufacture of bionic robots to simulate the movement of human muscles and achieve more natural human-machine interaction. The research on flexible actuators, especially on flexible actuators or double-layer structure flexible actuator devices responding to light, heat, humidity, etc. stimuli. When the size of the actuator reaches microns, the actuator scaling is limited, and the actuator's perception source is single, which is not suitable for actual environments with complex factors. Therefore, a variable pitch microstructure actuator based on light, humidity and heat multi-response is developed to meet the needs of flexible mechanical deformation in different environments.

[0004] Current micro-actuators are mainly realized by mechanical, electromagnetic or piezoelectric principles. However, these actuators not only have high cost, but also have problems of 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 centimeter, the actuation scaling ratio is greatly limited. At present, high-efficiency micro-actuators are still in the initial development stage. For a long time, due to the lack of suitable micro-actuator systems, the further development of micro-robot technology has been greatly limited. In addition, intelligent systems driven by green energy in nature are a major trend in future energy-efficient utilization. However, most traditional actuation materials are single-stimulus triggered, 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-actuator that can respond to stimuli in a complex environment. SUMMARY

[0005] To solve the above technical problems, the present application provides a light-thermal-humidity flexible driver with 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 as to produce mechanical deformation of the driver. Meanwhile, a groove type structure is prepared on the surface of the active layer, which will produce a protrusion on the top when mechanical deformation occurs. The pitch angle of the groove can be changed, which can enhance the deformation effect.

[0006] The technical scheme adopted by the present application is:

[0007] A light-thermal-humidity flexible driver with variable pitch microstructure comprises an active layer and a passive layer. The active layer is a PDMS / CNTs composite film, and the passive layer is a chitosan film. The passive layer is arranged on the upper surface of the active layer, and the lower surface of the active layer is provided with a groove structure. The present application carves a groove structure on the active layer, which can enhance the deformation ability of the actuator. This structure design makes the deformation more concentrated, thereby improving the working efficiency and response speed of the driver.

[0008] Further, the groove structure is arranged at equal intervals.

[0009] Alternatively, the groove structure is arranged at unequal intervals.

[0010] Further, the groove structure is arranged at an inclination, and the inclination angle ranges from 15° to 60°.

[0011] Further, the upper surface of the PDMS / CNTs composite film is subjected to plasma treatment.

[0012] Further, the PDMS / CNTs composite film is a film formed by dissolving the PDMS / CNTs composite through a cyclohexane solution and then solidifying.

[0013] Further, the chitosan film is a film formed by solidifying a chitosan mixed acetic acid solution.

[0014] A preparation method of a variable-pitch microstructure photothermal-hydroflexible driver, and the specific steps are as follows:

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

[0016] S2, adding cyclohexane in a beaker, and sequentially adding multi-walled CNTs powder, PDMS solvent, and PDMS curing agent into the cyclohexane, and stirring uniformly each time, uniformly applying the prepared solution to the PET film prepared in step S1, and heating, drying, and solidifying;

[0017] S3, peeling off the PDMS-CNT composite film that has been heated, dried, and solidified, and performing plasma treatment on the surface without the groove structure, and placing it in the hollow PET film in the middle;

[0018] S4, mixing chitosan powder in an acetic acid solution, stirring uniformly, applying to the surface of the PDMS-CNT composite film that has been plasma treated, and drying and solidifying to form a photothermal-hydroflexible driver;

[0019] S5, cutting and micro-machining the prepared photothermal-hydroflexible driver according to the set angle.

[0020] Further, the specific operation of step S2 is as follows: adding 1.2-3 ml of cyclohexane (HPLC, ≥99.9%) in a beaker, and weighing 0.012-0.03 g of multi-walled CNTs powder, stirring uniformly, placing in an ultrasonic machine for 1 hour, then adding 1.5-2.5 ml of PDMS solvent, stirring uniformly, again placing in an ultrasonic machine for 1 hour, and adding 0.15-0.25 ml of PDMS curing agent (the amount of PDMS to PDMS curing agent is 10:1); uniformly applying the prepared solution to the PET film with the groove structure using a glass rod, and heating at a temperature of 60°C for four hours.

[0021] Further, the specific operation of step S4 is as follows: mixing 35-45 mg of chitosan powder in 3.5-4.5 ml of acetic acid solution, stirring uniformly, applying to the surface that has been plasma treated, and placing to dry overnight.

[0022] The beneficial effects of this invention are: it can sensitively capture three stimuli—light, temperature, and humidity—and provide efficient bending feedback; it can also provide bending feedback in combined environments. By observing the different bending performance under different single and combined stimuli, the required stimulus source can be selected according to actual needs. The groove structure improves the braking performance of the actuator while allowing the spacing and angle of the grooves to be changed according to different needs, adapting to applications in soft robots, flexible grippers, etc., enabling the actuator to possess complex motion modes. The actuation material can be replaced with other flexible materials, and the actuation characteristics, such as material type, actuation 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 actuator's environmental adaptability. Attached Figure Description

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

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

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

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

[0027] Figure 5 This is a schematic diagram of the mold with equal spacing of the groove structure during the manufacturing process of this invention.

[0028] Figure 6 This is a schematic diagram of the mold with unequal spacing of the groove structure during the manufacturing of this invention.

[0029] Figure 7 This is a schematic diagram of the groove structure with different spacings according to the present invention.

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

[0031] Figure 9 This is a schematic diagram of the mechanical deformation of the present invention under a heating environment.

[0032] Figure 10 This is a schematic diagram of the deformation of the present invention under a photothermal coordinated environment.

[0033] Figure 11 This is a schematic diagram of the deformation of the present invention under a temperature and humidity controlled environment. Detailed Implementation

[0034] The present application will be further described with reference to the following examples. It will be apparent to those skilled in the art that the application is not limited to these specific embodiments, and that many modifications, changes, alternatives and equivalents will be apparent to one skilled in the art from the present disclosure.

[0035] In the description of the present application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements indicated thereby must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated thereby. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more, unless otherwise explicitly limited.

[0036] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] In the present application, unless otherwise explicitly specified and limited, "above" or "below" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "above", "over" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. "Below", "under" and "under" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0038] Terminology

[0039] A flexible actuator is a device that can convert various environmental stimuli such as light, temperature, humidity, pressure, pH, electricity, magnetism, and chemical action 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 stretching and contracting properties of muscles and are used in the design of artificial muscles. Flexible actuators integrate sensing, 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 actuator devices mainly receive external stimuli and use special structures or materials to produce changes in volume size and shape pattern to produce reversible movements such as bending, grabbing, and moving to achieve functions such as bending, grabbing, and moving.

[0040] Inspired by nature, researchers around the world have been trying to develop various types of actuator devices that can generate driving force through temperature, humidity, pH, light, electricity, and magnetism, etc. stimuli to trigger material deformation. According to the 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, etc. Some actuators have multiple response sources and can respond to multiple stimuli. Therefore, according to the number of response factors, actuators can be classified into single-stimulus response actuators and multiple-stimulus response actuators. According to the structure type, actuators can also be divided into thin film structure actuators, fiber structure actuators, and cavity structure actuators, etc. A special class of hierarchical structure actuators can also be classified according to the number of layers into single-layer actuators, double-layer actuators, and gradient structure actuators.

[0041] Carbon nanotube (abbreviated as CNT) was discovered by Japanese physicist Sumio Iijima in NEC Laboratory in Tsukuba in January 1991 using high-resolution transmission electron microscopy from the product of arc method production of carbon fiber. It is a tubular carbon molecule, each carbon atom on the tube adopts sp2 hybridization, and is combined with carbon-carbon sigma bond between each other, forming a honeycomb structure composed of hexagons as the skeleton of carbon nanotube. Each carbon atom on the tube does not participate in hybridization of a pair of p electrons between each other to form a conjugated pi electron cloud across 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 direction of the tube is very thin, only nanometer scale, and several tens of thousands of carbon nanotubes together are only a hair wide, and the name of carbon nanotube is also derived from this. In the axial direction, it can be as long as tens to hundreds of microns. Carbon nanotubes are not always straight, and local concave-convex phenomenon may occur, which is due to the mixing of pentagons and heptagons in the hexagonal structure. The place where the pentagon appears, due to the relationship of tension, causes the carbon nanotube to protrude outward. If the pentagon happens to be at the top end of the carbon nanotube, it forms the closure of the carbon nanotube. The place where the heptagon appears, the carbon nanotube is concave inward. The hardness of carbon nanotube is equivalent to that of diamond, but it has good flexibility and can be stretched. At present, in the commonly used reinforced fibers in industry, a key factor that determines the strength is the aspect ratio, that is, the ratio of length to diameter. The aspect ratio that material engineers hope to get is at least 20:1, and the aspect ratio of carbon nanotube 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 high, and its heat exchange performance in the vertical direction is relatively low. Through appropriate orientation, carbon nanotube can synthesize high anisotropic thermal conduction material. In addition, carbon nanotube has high thermal conductivity. As long as a small amount of carbon nanotube is doped in the composite material, the thermal conductivity of the composite material will be greatly improved. Compared with traditional photoelectric materials, CNT has excellent light absorption and light response performance. CNT is a multi-subband, direct bandgap semiconductor, and its bandgap is inversely proportional to the diameter, so CNT thin film has wide spectrum light absorption characteristics from ultraviolet to infrared. In general, the response factors of CNT are mainly temperature, light and electric signal, which provide material support for preparing thermal response, photo-thermal response, electric response and multiple stimulus response actuators.

[0042] Chitosan is a product of N-deacetylation of chitin. Chitin, chitosan and cellulose have similar chemical structures. Cellulose has a hydroxyl group at C2 position, while chitin and chitosan have an acetyl amino group and an amino group at 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 molecular structure of chitosan is more reactive than the acetyl amino group in the molecular structure of chitin, which makes the polysaccharide have excellent biological functions and can undergo chemical modification reactions. Therefore, chitosan is considered to have greater application potential than cellulose as a functional biomaterial. After being dissolved, chitosan in gel state has 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 swell by absorbing water through cross-linked structure. Therefore, chitosan is widely used in food additives, textiles, agriculture, environmental protection, beauty and health care, cosmetics, antibacterial agents, medical fibers, medical dressings, artificial tissue materials, drug release materials, gene transduction vectors, biomedical fields, medical absorbable materials, tissue engineering carrier materials, medical treatment and drug development and many other fields and other daily chemical industry.

[0043] Example 1

[0044] Referring to Figure 1 The present embodiment provides a light-heat-wet flexible driver with variable pitch microstructure, which comprises an active layer 1 and a passive layer 2. The active layer 1 is a PDMS / CNTs composite film, and the passive layer 2 is a chitosan film. The passive layer 2 is arranged on the upper surface of the active layer 1, and the lower surface of the active layer 1 is provided with a groove structure 3. The groove structure 3 is engraved on the active layer 1, and the deformation ability of the actuator can be enhanced by constructing the groove structure. This structure design makes the deformation more concentrated, thereby improving the working efficiency and response speed of the driver.

[0045] Referring to Figure 4 Compared with the full-filling film with groove structure: the deformation effect is strengthened by constructing the groove structure, and the driving force of the actuator is enhanced. At the same time, the deformation ability of the actuator can be significantly enhanced by constructing the groove structure. This structure 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 robot, the two-degree-of-freedom joint composed of groove structure can greatly strengthen the motion energy of the robot. In the design of multi-arm gripper, according to the magnetic arrangement design, the gripper can be folded under the magnetic field to realize the function of grabbing and releasing objects.

[0046] The groove structure 3 in the embodiment is arranged at equal intervals. Of course, the groove structure 3 can also be arranged at unequal intervals, as shown in Figure 2 The height-to-width ratio of the groove structure is between 0.1 and 2.0. The groove structure 3 can be arranged to be inclined according to requirements, as shown in Figure 3 The inclination angle ranges from 15° to 60°.

[0047] The upper surface of the PDMS / CNTs composite film in the embodiment is subjected to plasma treatment.

[0048] The PDMS / CNTs composite film in the embodiment is a film formed by dissolving PDMS / CNTs composite in a cyclohexane solution and then solidifying. The film has a thickness of about 0.1 mm. The PDMS / CNTs film has good light-heat conversion efficiency. In addition, the PDMS material has a very high thermal expansion coefficient and strong tensile property. Carbon nanotubes (CNT) are a nanoscale tubular structure material composed of carbon atoms, which has excellent mechanical properties, with an elastic modulus and tensile strength of more than 1000 GPa and 100 GPa, respectively. In addition, CNT also has very high flexibility and durability. In addition, CNT also has good optical properties and thermal conductivity. CNT has the ability to absorb ultraviolet, visible and infrared waves and excellent light absorption and light response performance.

[0049] The chitosan film in the embodiment is a film formed by solidifying a chitosan mixed acetic acid solution. The film has a thickness of about 0.1 mm. The chitosan film can swell by absorbing water through a cross-linked structure, so the present application has a triple response to light, heat and humidity.

[0050] The light-heat-humidity flexible driver with variable spacing microstructure of the present application is based on a double-layer structure of PDMS / CNTs and chitosan inorganic composite mechanism, with a length of 1 cm, a width of 0.1 mm and a thickness of 0.2 mm, and a total volume of 0.2 mm 3 .

[0051] When the present application is only stimulated by heat without light, the driver is in a bent state, as shown in Figure 9 When the same temperature environment is subjected to light stimulation, the bending angle gradually increases, as shown in Figure 10 When the same temperature environment is subjected to wet stimulation, it is found that the bending angle is decreasing. This is because the chitosan film located in the upper layer can respond to humidity stimulation, while the PDMS / CNTs film located in the lower layer is an inert layer that cannot respond to humidity stimulation, so the film will bend. However, the bending performance of the film under heat stimulation is much greater than that under wet stimulation, so the bending angle decreases, as shown in Figure 11 When the driver is taken out of the stimulation environment, the driver will relax to the initial state.

[0052] The present application can make the driver suitable for deformation demand in different natural environment. Due to the characteristics of the selected material, the driver can generate mechanical deformation in light, wet and heat environments respectively, and can also generate mechanical deformation demand under the stimulation of light-heat, light-wet, heat-wet, light-heat-wet and other composite environments. At the same time, it can also be fitted according to its different deformation performance to the corresponding environment. The groove structure described can meet the realization of complex motion mode. In the design of multi-arm gripper, according to the magnetic arrangement design, the gripper can be folded under the magnetic field to realize the function of grabbing and releasing objects. At the same time, its structure size is only 0.2mm 3 , with the advantages of small volume and light weight.

[0053] Example two

[0054] The present application provides a preparation method of a variable-pitch microstructure photo-thermal-humidity flexible driver, and the specific steps are as follows:

[0055] S1, using LPKF laser to micro-machine the PET film with a thickness of 0.1mm, forming a groove structure on the surface of the PET film; the equidistant PET film mold is shown in Figure 5 , and the non-equidistant PET film mold is shown in Figure 6 ;

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

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

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

[0059] S3, the heated and dried PDMS-CNT composite film is peeled off, and the surface without the groove structure is subjected to plasma treatment for 60 s, and is placed in a PET film with a hollow in the middle and a thickness of 0.2 mm;

[0060] S4, chitosan powder is mixed in an acetic acid solution, stirred uniformly, applied to the surface of the PDMS-CNT composite film subjected to plasma treatment, and dried and solidified to form a photo-thermal-hygroscopic flexible driver; see Figure 7 .

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

[0062] In this embodiment, 40 mg of chitosan powder is mixed in 4 ml of an acetic acid solution, stirred uniformly, applied to the surface subjected to plasma treatment, and left to dry overnight.

[0063] S5, the prepared photo-thermal-hygroscopic flexible driver is cut and micromachined according to a set angle, and different structures of micro photo-thermal-hygroscopic flexible drivers can be obtained, see Figure 8 .

[0064] The present application can sensitively capture light, temperature and humidity and make efficient bending feedback; at the same time, it can also make bending feedback in its composite environment, and the different bending properties under different single stimuli and composite stimuli can be selected according to actual needs. The groove structure can improve the braking performance of the driver, and the pitch and angle of the groove can be changed according to different needs to cope with its application in soft robots, flexible grippers, etc., so that the driver has complex motion modes. The actuating material can be replaced by other flexible materials, and the 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 and further enhance the environmental adaptability of the driver.

Claims

1. A variable pitch microstructure opto-thermal hygro-flexible driver 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 the lower surface of the active layer is provided with a groove structure; the preparation method of the variable-pitch microstructure photothermal-hygroscopic flexible driver is as follows: S1, using a laser to micro-machine a PET film to form a groove structure on the surface of the PET film; S2, adding cyclohexane in a beaker, and sequentially adding multi-walled CNTs powder, PDMS solvent and PDMS curing agent into the cyclohexane, and stirring uniformly each time, uniformly applying the prepared solution to the PET film prepared in step S1 and heating, drying and curing; S3, peeling off the PDMS-CNTs composite film after heating and drying and performing plasma treatment on the surface without the groove structure, and placing it in the hollow PET film; S4, mixing chitosan powder in an acetic acid solution, stirring uniformly, applying to the surface of the PDMS-CNTs composite film after plasma treatment, and drying and curing to form a photothermal-hygroscopic flexible driver; S5, cutting and micro-machining the prepared photothermal-hygroscopic flexible driver according to the set angle.

2. The opto-thermal hygro-flexible driver of variable-pitch microstructure according to claim 1, characterized in that: The groove structure is arranged at equal intervals.

3. The opto-thermal hygro-flexible driver of variable-pitch microstructure of claim 1, wherein: The groove structure is arranged at unequal intervals.

4. The opto-thermal hygro-flexible driver of variable-pitch microstructure of claim 1, wherein: The groove structure is arranged at an inclination, and the inclination angle ranges from 15° to 60°.

5. A preparation method of a variable-pitch microstructure photothermal-hygroscopic flexible driver, which comprises the following specific steps: S1, using a laser to micro-machine a PET film to form a groove structure on the surface of the PET film; S2, adding cyclohexane in a beaker, and sequentially adding multi-walled CNTs powder, PDMS solvent and PDMS curing agent into the cyclohexane, and stirring uniformly each time, uniformly applying the prepared solution to the PET film prepared in step S1 and heating, drying and curing; S3, peeling off the PDMS-CNTs composite film after heating and drying and performing plasma treatment on the surface without the groove structure, and placing it in the hollow PET film; S4, mixing chitosan powder in an acetic acid solution, stirring uniformly, applying to the surface of the PDMS-CNTs composite film after plasma treatment, and drying and curing to form a photothermal-hygroscopic flexible driver; S5, cutting and micro-machining the prepared photothermal-hygroscopic flexible driver according to the set angle.

6. The method of claim 5, wherein the method further comprises: The specific operation of step S2 is as follows: 1.2-3 ml of cyclohexane is added in a beaker, 0.012-0.03 g of multi-walled CNTs powder is weighed and mixed, stirred uniformly, placed in an ultrasonic machine for 1 hour, then 1.5-2.5 ml of PDMS solvent is added, stirred uniformly, again placed in an ultrasonic machine for 1 hour, and 0.15-0.25 ml of PDMS curing agent is added; the prepared solution is uniformly applied to the PET film with a groove structure by using a glass rod, and heated at a temperature of 60°C for four hours.

7. The method of claim 6, wherein the method further comprises: 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 uniformly, spread on the surface subjected to plasma treatment, and left to dry overnight.

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