Flexible actuator with optically programmable configuration and function and driving method

Abstract

The invention discloses a flexible actuator with optically programmable configuration and function and a driving method. A driving-variable stiffness composite structure is adopted, wherein a driving layer is a liquid crystal elastomer and can generate reversible deformation under thermal stimulation; the variable stiffness layer is a stiffness-adjustable polymer, is initially soft, is selectively hardened after being irradiated by an ultraviolet region, realizes local stiffness space programming, and can be reversibly adjusted through heating; through the collaborative response of the double-layer material, the actuator realizes the programmable configuration and function; in the local stiffness hardening mode, the variable stiffness layer is subjected to regional curing by utilizing ultraviolet light, and the deformation mode can be accurately controlled; a preset three-dimensional structure can be constructed by combining the integral deformation fixing mode with mold preforming and photocuring; and in cooperation with heating-cooling regulation and control, locking and unlocking of the deformation state can be achieved. According to the method, the functions of configuration customization, regional programming and state locking are integrated, and a high-performance solution is provided for a soft robot, a self-adaptive grabbing system and an intelligent bionic system.

Description

Technical Field

[0001] This invention relates to a flexible actuator in the field of soft robotics, specifically to a flexible actuator and driving method whose configuration and function are optically programmable. Background Technology

[0002] Soft robotics technology, with its inherent flexibility and excellent environmental adaptability, has shown great potential in fields such as grasping fragile objects, medical rehabilitation, and exploration in confined spaces. Its core driving component—the flexible actuator—is typically made of materials such as dielectric elastomers, pneumatic networks, or shape memory polymers, and can produce large deformations in response to external stimuli.

[0003] However, most existing flexible actuators have fixed initial configurations and functions once fabricated, lacking the ability to dynamically reconfigure them according to complex and changing tasks in the application environment. Although some research has attempted to introduce variable stiffness materials to adjust the mechanical properties of actuators, existing solutions either rely on global control and cannot achieve local programming, or lack the means to stably fix flexible materials to complex three-dimensional configurations. Furthermore, how to integrate a multi-functional closed loop of "drive-lock-reconfiguration" into a single actuator to achieve non-contact, programmable customization, and reversible locking of the configuration remains a current technological bottleneck. This severely limits the ability of a single actuator to achieve diverse functions, hindering the further expansion of the intelligence level and application scope of soft robots. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a flexible actuator and driving method with optically programmable configuration and function. Through the synergistic effect of two functional structures and multi-physics response, it solves the problems of existing flexible actuators, such as single deformation, continuous energy consumption to maintain the deformation state, and lack of local programming and complex shape programming capabilities. It provides a technical solution that can realize integrated driving and controllable stiffness characteristics and programmable configuration and function, so as to realize intelligent, energy-saving and controllable complex deformation operation.

[0005] The technical solution for achieving the objective of this invention is as follows: I. A flexible actuator with optically programmable configuration and function Includes: a driving layer composed of a liquid crystal elastomer material, which deforms under thermal stimulation; A variable stiffness layer is stacked and fixedly connected to the driving layer. The variable stiffness layer is made of a stiffness-adjustable polymer material and is divided into two states depending on whether it is exposed to ultraviolet light. The two states of the variable stiffness layer exhibit different stiffnesses at different temperatures.

[0006] The two states are divided into a hardened state without ultraviolet light irradiation and a hardened state with ultraviolet light irradiation: Uncured state without ultraviolet light irradiation: The variable stiffness layer has not been cured by ultraviolet light, the glass transition temperature of the variable stiffness layer is lower than room temperature, the temperature of the variable stiffness layer at room temperature is higher than the glass transition temperature of the variable stiffness layer, and the stiffness of the variable stiffness layer is low, which is a soft state. Ultraviolet light irradiation hardening state: At least one predetermined area of ​​the variable stiffness layer is irradiated with ultraviolet light, and the glass transition temperature of the predetermined area rises to above room temperature. At room temperature, the temperature of the predetermined area is lower than the glass transition temperature of the predetermined area. The stiffness of the stiffness-adjustable polymer material in the predetermined area is increased, thereby achieving the hardening state. When the stiffness-adjustable polymer material is in a hardened state after UV curing, it possesses shape memory characteristics. Its stiffness is reduced by heating it above its glass transition temperature, thereby releasing the hardened state and unlocking it. Subsequently, by cold quenching, its temperature is reduced below the glass transition temperature, significantly increasing its stiffness and thus relocking the state. When the stiffness-adjustable polymer material is in a state without UV curing, it always maintains a low-stiffness flexible state.

[0007] The liquid crystal elastomer material of the driving layer is a main-chain liquid crystal elastomer pre-oriented by a stretching-UV crosslinking process. The raw materials for its preparation, by weight, include: 100 parts of mesocrystalline unit (RM257), 5.5-6.5 parts of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 20-23 parts of 2,2'-(ethylenedioxy)diethylthiol (EDDET), 0.5-0.8 parts of 2-hydroxy-2-methylphenylacetone (HHMP), and 0.2-0.4 parts of catalyst (DPA). The initial state of the driving layer is achieved by heating above its phase transition temperature to form a shrinkage deformation state, which is then cooled below its phase transition temperature to restore the initial state. The stiffness-adjustable polymer material is a UV-curable shape memory polymer system, and its raw materials, by weight, include: 12-18 parts of aliphatic polyurethane acrylic resin (AUD), 30-38 parts of tricyclodecanediethanol diacrylate (TCDDA), 35-40 parts of epoxy resin (E-51), 10-15 parts of polyetheramine (D230), and 0.3-0.8 parts of photoinitiator benzoin dimethyl ether (DMPA). The cooling rate of the quenching process is greater than 40℃ / s.

[0008] The driving layer and the variable stiffness layer are connected by an adhesive to form an initial planar sheet structure. The adhesive is a silicone adhesive. In the case of a variable stiffness layer hardened by ultraviolet light irradiation, the variable stiffness layer of the flexible actuator softens after being heated above its glass transition temperature in the initial state, while the drive layer contracts and deforms after being heated above its phase transition temperature, causing the softened variable stiffness layer to deform as well. The variable stiffness layer is then quenched to below room temperature to form a hardened and locked state, which is released by reheating above its glass transition temperature. During the quenching process, the drive layer cannot recover in time compared to the variable stiffness layer, causing the variable stiffness layer to harden and lock, while the drive layer remains in a contracted and deformed state. Upon cooling in a natural environment, the drive layer recovers, thereby causing the variable stiffness layer to recover to its initial state as well.

[0009] II. A Soft Robot It includes at least one of the aforementioned flexible actuators as its core actuation and structural unit.

[0010] III. A Driving Method for a Flexible Actuator The driving method includes: It is divided into local stiffness hardening mode and overall deformation fixed mode: The local stiffness hardening mode involves using ultraviolet light to irradiate a specific area of ​​the variable stiffness layer in the initial state to achieve hardening of the specific area. The overall deformation fixing mode is that the flexible actuator is constrained by external forces to form a preset three-dimensional configuration, and the preset three-dimensional configuration is hardened and fixed by ultraviolet light irradiation.

[0011] The local stiffness hardening mode is specifically as follows: A mask with a preset pattern is obtained, the pattern corresponding to the geometry and spatial distribution of the preset region on the variable stiffness layer of the flexible actuator. The mask is placed on one side of the variable stiffness layer of the flexible actuator and aligned so that the preset pattern and the preset region match. Then, ultraviolet light is used to irradiate the variable stiffness layer through the mask. After irradiation, the preset region changes from the un-UV-irradiated hardened state to the UV-irradiated hardened state, while the un-irradiated region remains in the un-UV-irradiated hardened state.

[0012] The overall deformation fixing mode is specifically as follows: Mechanical constraints are applied to the flexible actuator in a planar state using a mold with a preset three-dimensional shape or a set of independently controlled jigs, causing it to deform into a preset three-dimensional configuration; While maintaining the mechanical constraints, global or local ultraviolet light irradiation is applied to the variable stiffness layer, causing all or part of its area to change from the un-UV-irradiated hardened state to the UV-irradiated hardened state, thereby removing the mechanical constraints. The flexible actuator maintains the preset complex three-dimensional configuration due to the hardening and locking of the variable stiffness layer.

[0013] The mold is a rigid mold with a target three-dimensional shape; or the fixture array controls each degree of freedom to reproduce a preset spatial surface.

[0014] Both the local stiffness hardening mode and the overall deformation fixing mode achieve the locking and unlocking of the dynamic deformation process through the following steps: Configuration locking step: The flexible actuator is heated in the initial state, and the shrinkage and deformation of the driving layer causes the variable stiffness layer to deform to the preset intermediate configuration. Then, the flexible actuator is subjected to cold quenching treatment, so that the variable stiffness layer in the ultraviolet light irradiation hardening state hardens and locks the intermediate configuration. Configuration unlocking steps: The flexible actuator is heated to reduce the stiffness of the variable stiffness layer to a soft state, and then the flexible actuator is allowed to cool naturally in the environment to restore the actuator to its initial state. Finally, the above steps are repeated to enter a new deformation cycle.

[0015] The beneficial effects of this invention are: The flexible actuator of the present invention has high flexibility and adaptability in its working mode, specifically manifested in: 1. Flexible cooling control methods: The actuator can adopt various cooling methods such as passive natural cooling, active air cooling, water cooling, and semiconductor cooling, depending on the cooling rate requirements of the actual application. This diversified cooling strategy provides an important guarantee for achieving precise deformation control and stiffness adjustment.

[0016] 2. Fully reversible working mechanism: Based on the reversible driving characteristics of liquid crystal elastomers and the reversible thermal phase transition of variable stiffness polymers, the deformation generation and stiffness control process of the actuator are both fully reversible, ensuring that the actuator can achieve long-term stable cyclic operation.

[0017] 3. Diverse deformation control modes: Precise Deformation Mode: By adjusting the stimulation mode of the driving layer and the local stiffness of the variable stiffness layer, the actuator can achieve repeated reversible controlled deformation, presenting a rich variety of deformation forms.

[0018] Zero-power holding mode: In shape-locked working mode, the actuator can achieve zero-power holding of the deformed state through the characteristics of the variable stiffness layer, overcoming the technical problem that traditional actuators need to continuously consume energy to maintain deformation.

[0019] Compared with the prior art, the present invention has the following significant advantages: 1. Programmability of Functions and Configurations By selectively curing variable stiffness layers with ultraviolet light using a mask, precise programming of the local stiffness and deformation capabilities of the actuator can be achieved. This local programming capability enables the actuator to achieve shape locking in specific areas after heating and rapid cooling, while maintaining deformation capabilities in other areas. This allows for complex, programmable actuation behaviors (such as multi-stage locking), greatly expanding the functional versatility of the actuator.

[0020] 2. Flexible construction of complex initial configurations By utilizing the flexibility of uncured variable stiffness layers at room temperature, actuators can be pre-fixed into arbitrary complex three-dimensional shapes (such as S-shapes, torsional shapes, etc.) using tools such as jigs, and then permanently cured and set by ultraviolet light irradiation. This method overcomes the limitations of traditional manufacturing processes in preparing soft actuators with complex and irregular initial shapes, providing a wider range of initial configuration options for soft robots and intelligent devices.

[0021] 3. Reversible Deformation Locking Based on Cooling Rate Regulation Based on the different dependence of phase transition kinetics of liquid crystal elastomers (LCEs) and glass transition of variable stiffness polymers on cooling rates, the final state of the actuator can be actively selected by adjusting the cooling rate: whether to restore the initial shape or lock in the deformed state after actuation. This reversible and controllable locking and unlocking capability gives the actuator a function similar to "mechanical memory," enabling advanced applications such as load bearing and state maintenance.

[0022] This invention integrates configuration customization, region programming, and state locking functions, providing a high-performance solution for soft robots, adaptive grasping, and intelligent bionic systems. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the optically programmable flexible actuator with the configuration and function described in this invention. Figure 2 This is an exploded view of the flexible actuator described in this invention; Figure 3 A schematic diagram illustrating the principle of deformation control and shape locking by heating the actuator (a stiffness-adjustable polymer before and after UV curing) and adjusting the cooling rate. Figure 4 A schematic diagram illustrating the use of optical programming to perform local programming of an actuator; Figure 5 A schematic diagram illustrating the use of optical programming to program the complex initial shape of an actuator; Figure 6 Experimental photographs showing deformation control and shape locking achieved by adjusting the cooling rate in thermally driven mode; Figure 7 Experimental photographs showing how local deformation locking is achieved through rapid cold quenching after local programming of the actuator; Figure 8 Experimental photographs showing how deformation control and shape locking are achieved by adjusting the cooling rate after programming the actuator with a complex initial shape.

[0024] In the diagram: Driving layer-1, variable stiffness layer-2. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] To illustrate the technical solution and objectives of this invention, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] like Figure 1 and Figure 2 As shown, a flexible actuator with optically programmable configuration and function includes: A driving layer 1 is composed of a liquid crystal elastomer material configured to produce reversible, anisotropic macroscopic deformation based on the orientation change of liquid crystal molecules under thermal stimulation. A variable stiffness layer 2 is stacked and fixedly connected with a driving layer 1. The variable stiffness layer 2 is made of a stiffness-adjustable polymer material and is divided into two states depending on whether it is exposed to ultraviolet light. The two states of the variable stiffness layer 2 exhibit different stiffnesses at different temperatures.

[0028] The driving layer 1, which serves as the power source for the actuator's motion, is composed of a liquid crystal elastomer material, specifically a liquid crystal elastomer film with a uniaxial orientation structure. During the fabrication process, the liquid crystal molecules within this film achieve a macroscopically ordered arrangement through a stretching-crosslinking process. Its working mechanism is as follows: when subjected to external stimuli such as heating, or when heat is generated by the absorption of specific wavelengths of light through doping with photothermal agents / its inherent properties, the degree of order of the liquid crystal molecules changes, causing the film to undergo significant and reversible contraction along its orientation direction. After the stimulus is removed and the film cools, it returns to its initial length. This reversible contraction-recovery behavior provides the actuator with a core, large-amplitude driving force.

[0029] The two states are: hardened state without ultraviolet light irradiation and hardened state with ultraviolet light irradiation. Uncured state without UV irradiation: In this state, the variable stiffness layer 2 has not been cured by UV light, its crosslinking density is at an initial low level, the glass transition temperature of the variable stiffness layer 2 is lower than room temperature, the temperature of the variable stiffness layer 2 at room temperature is higher than the glass transition temperature of the variable stiffness layer 2, the stiffness of the variable stiffness layer 2 is low and it is in a soft state, specifically exhibiting soft and highly elastic characteristics. UV irradiation hardening state: In this state, at least one predetermined region of the variable stiffness layer 2 is hardened by UV irradiation, its crosslinking density increases significantly, the glass transition temperature of the predetermined region rises to a level much higher than room temperature, and the temperature of the predetermined region at room temperature is lower than the glass transition temperature of the predetermined region. The stiffness of the stiffness-adjustable polymer material in the predetermined region is improved, exhibiting rigidity, and possessing shape memory and fixation capabilities, thereby achieving the hardened state. After switching from an uncured state to a cured state under ultraviolet light, the room temperature elastic modulus of the variable stiffness layer 2 is significantly improved, achieving a change spanning orders of magnitude. In the cured state under ultraviolet light, the variable stiffness layer 2 possesses reversible stiffness adjustment capability, responding to temperature changes and switching between a high-stiffness locked state and a low-stiffness unlocked state. This enables locking and unlocking of the flexible actuator after deformation. Specifically, this can be achieved by applying a color-changing ink to the irradiated area to distinguish it from the non-irradiated area, and the ink can also characterize the temperature during heating.

[0030] The stiffness-tunable polymer material in the UV-cured state can reversibly reduce its stiffness by heating it above its glass transition temperature, thus unlocking the hardening process. Subsequently, its temperature is reduced below the glass transition temperature by rapid quenching at a cooling rate greater than 40℃ / s, significantly increasing its stiffness and thus relocking the state. The stiffness-tunable polymer material in the uncured state has a lower glass transition temperature and a very low internal crosslinking density compared to the UV-cured stiffness-tunable polymer material. Even if the temperature is below the glass transition temperature, its stiffness cannot affect the deformation of the driving layer 1, thus it cannot be quenched and locked, i.e., it remains in a soft state with low stiffness.

[0031] Specifically, such as Figure 3 As shown, the stiffness-tunable polymer used in the variable stiffness layer of this invention exhibits significant performance differences before and after curing under ultraviolet light irradiation. This difference allows for the control of the actuator's behavior. The variable stiffness layer 2, located below the drive layer 1 and crucial for the actuator's deformation locking, is composed of a thermally responsive stiffness-tunable polymer and is key to achieving deformation locking. The variable stiffness layer 2 has two states: Uncured state without UV irradiation: In this state, the variable stiffness layer has not been cured by UV light, its crosslinking density is at an initial low level, and its glass transition temperature is below room temperature. The material exhibits soft and highly elastic properties. When the actuator is heated, the liquid crystal elastomer contracts, driving the actuator to bend and deform. Upon cooling, the liquid crystal elastomer recovers, and the actuator returns to its original shape. The cooling rate has no significant effect on the actuator behavior.

[0032] UV-cured state: In this state, at least one predetermined region of the variable stiffness layer 2 is cured by UV irradiation, resulting in a significant increase in crosslinking density and a glass transition temperature far exceeding room temperature. The material exhibits rigidity in this region and possesses shape memory and fixation capabilities. This polymer possesses unique dynamic mechanical properties, with its elastic modulus being extremely sensitive to temperature changes: when heated above its glass transition temperature or phase transition temperature, the polymer chain segments become active, and the material transitions from a rigid to a soft state with a significantly reduced modulus. At this point, even a small stress generated by the driving layer 1 can cause it to undergo compliant deformation. When the temperature is rapidly cooled below the transition temperature, the polymer chain segment movement is frozen, and the material returns to a high-modulus rigid state, effectively resisting the elastic restoring force of the driving layer and other parts, thus "locking" the overall shape of the actuator in its current deformed state. The unlocking process only requires reheating, forming a controllable cycle of "heating-deformation and softening-rapid cooling and locking-reheating and unlocking."

[0033] Specifically, when the actuator is heated, the stiffness-tunable polymer undergoes a glass transition, significantly reducing its modulus and softening. Simultaneously, the liquid crystal elastomer undergoes a first-order phase transition from a nematic to an isotropic phase, resulting in axial contraction and driving the actuator's bending deformation. During the cooling stage, the phase transition kinetics of the two materials exhibit significant differences: the first-order phase transition of the liquid crystal elastomer is distinctly time-dependent, and rapid quenching delays its phase transition process, maintaining its contracted state; while the glass transition of the stiffness-tunable polymer is a kinetically controlled second-order transition, relatively insensitive to the cooling rate, and can rapidly recover its high-modulus state during rapid cooling. Based on this mechanism, after the actuator deforms due to heat: if slow cooling is used, the liquid crystal elastomer gradually recovers, driving the actuator to return to its initial shape; if rapid quenching is implemented, the variable stiffness layer solidifies first and locks the system's mechanical state, while the driving layer remains in a contracted state, thus effectively fixing the bending deformation. The locked state can be released by heating, and the shape can be fully restored through a subsequent slow cooling process.

[0034] The liquid crystal elastomer material used in the driving layer 1 is a main-chain liquid crystal elastomer pre-oriented by a stretching-UV crosslinking process. The raw materials for its preparation include, by weight, 100 parts of mesocrystalline unit (RM257), 5.5~6.5 parts of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 20~23 parts of 2,2'-(ethylenedioxy)diethylthiol (EDDET), 0.5~0.8 parts of 2-hydroxy-2-methylphenylacetone (HHMP), and 0.2~0.4 parts of catalyst (DPA). The initial state of the driving layer 1 is formed by heating above its phase transition temperature to a shrinkage deformation state along its molecular orientation direction. The shrinkage deformation state is restored to its initial state by natural cooling in the environment to below its phase transition temperature. The reversible shrinkage strain range is between 40% and 50%. The stiffness-adjustable polymer 2 material is a UV-curable shape memory polymer system. Its raw materials, by weight, include: 12-18 parts of aliphatic polyurethane acrylic resin (AUD), 30-38 parts of tricyclodecanediethanol diacrylate (TCDDA), 35-40 parts of epoxy resin (E-51), 10-15 parts of polyetheramine (D230), and 0.3-0.8 parts of photoinitiator benzoin dimethyl ether (DMPA).

[0035] The driving layer 1 and the variable stiffness layer 2 are bonded together at the interface by an adhesive to form the initial planar sheet structure. The adhesive is a silicone adhesive Sil-Poxy, whose Young's modulus matches the modulus of the driving layer 1 and the variable stiffness layer 2 in the uncured state to ensure effective strain transfer. The preparation method of the liquid crystal elastomer is as follows: 5.75g of RM257 and 1.28g of toluene are mixed in a beaker and heated in an oven at 85°C for about 20 minutes. Then, 0.037g of HHMP is added to the beaker. After the mixture clarifies, 0.342g of PETMP and 1.238g of EDDET are mixed together and then added to the above mixture. Subsequently, 0.018g of PDA is poured into the beaker. The solution is stirred for about 1 minute, degassed in a vacuum chamber for about 5 minutes, and poured into a 60mm*10mm*1mm mold. Next, the mold is placed in a dark environment for 24 hours. In a subsequent step, the cured film-like LCE is placed in an oven at 85°C for 12 hours to evaporate the solvent. Finally, the LCE film is stretched to three times its original length and irradiated with ultraviolet light at 365nm and 10mW / cm2 for 10 minutes.

[0036] The stiffness-tunable polymer was prepared as follows: 1.5g AUD, 3.45g TCDDA, 3.75g E-51, and 0.05g DMPA were mixed in a beaker and heated at 80℃ for 5 minutes. Then, 1.25g D230 was added to the beaker. After stirring the mixture for 1 minute, it was degassed in a vacuum chamber for approximately 5 minutes to obtain a prepolymer of the stiffness-tunable polymer. Next, the obtained prepolymer was poured into a 60mm*10mm*1mm mold. It was thermocured at 80℃ for 4 hours, followed by post-curing at 120℃ for 4 hours. Finally, a stiffness-tunable polymer without UV curing was obtained.

[0037] A sheet-like composite material is formed by bonding a liquid crystal elastomer film with a stiffness-adjustable polymer using Sil-Poxy adhesive, which can then be used for local programming or three-dimensional complex shape configurations.

[0038] The variable stiffness layer 2 in the hardened state is irradiated with ultraviolet light. In the initial state, the variable stiffness layer 2 of the flexible actuator softens after being heated to a temperature exceeding its glass transition temperature, while the drive layer 1 shrinks and deforms after being heated to a temperature exceeding its phase transition temperature, causing the softened variable stiffness layer 2 to deform together. The variable stiffness layer 2 is then rapidly quenched to a temperature below room temperature to form a hardened and locked state. The hardened and locked state is released by reheating to a temperature exceeding its glass transition temperature. The nematic phase transition characteristics allow the drive layer 1 to return to its original state before heating during the natural and slow cooling process after heating. In rapid cold quenching, the glass transition dynamics of the variable stiffness layer 2 takes precedence over the nematic phase transition of the driving layer 1, which makes the driving layer 1 unable to recover in time compared to the variable stiffness layer 2, resulting in the variable stiffness layer 2 hardening and locking, while the driving layer 1 is still in a state of shrinkage deformation. As the material cools slowly in the natural environment, the driving layer 1 has enough time to recover, thereby causing the variable stiffness layer 2 to recover to its initial state as well.

[0039] A soft robot comprising at least one flexible actuator as its core actuation and structural unit.

[0040] A driving method using a flexible actuator includes: It is divided into local stiffness hardening mode and overall deformation fixed mode: The local stiffness hardening mode is to use ultraviolet light to irradiate a specific area of ​​the variable stiffness layer 2 in the initial state to achieve hardening of the specific area; Specifically, the local stiffness hardening mode is that the flexible actuator uses ultraviolet light to irradiate a specific area of ​​the variable stiffness layer 2 in the initial state, which increases the glass transition temperature of the stiffness-adjustable polymer material in the specific area, thereby increasing its stiffness until the specific area of ​​the variable stiffness layer 2 achieves a hardened state, which is in the ultraviolet light irradiation hardened state, and the specific area is in the hardened state at room temperature. The overall deformation fixing mode is that external constraints cause the flexible actuator to form a preset complex three-dimensional configuration, and the preset complex three-dimensional configuration is hardened and fixed by ultraviolet light irradiation.

[0041] The overall deformation fixing mode involves using external constraints to position the flexible actuator into a preset complex three-dimensional configuration, and then applying global or local ultraviolet light irradiation to the variable stiffness layer 2. The cross-linking density of the irradiated area increases and the glass transition temperature rises, causing all or part of the area to change from a state of hardening without ultraviolet light irradiation to a state of hardening under ultraviolet light irradiation. At room temperature, all or part of the area is in a hardened state. After removing the external constraints, the flexible actuator permanently maintains the preset complex three-dimensional configuration due to the curing of the variable stiffness layer 2, which serves as its new and stable initial shape.

[0042] like Figure 4 As shown, the locally stiffened mode is specifically as follows: Obtain a mask with a preset pattern, the pattern corresponding to the geometry and spatial distribution of a preset area on the variable stiffness layer 2 of the flexible actuator to be programmed. Place the mask on one side of the variable stiffness layer of the flexible actuator and perform precise alignment so that the preset pattern and the preset area match. Then, use ultraviolet light to irradiate the variable stiffness layer through the mask. After irradiation, the preset area changes from a state of hardening without ultraviolet light irradiation to a state of hardening with ultraviolet light irradiation, thereby permanently defining a region with high stiffness and deformation lock by adjusting the cooling rate on the flexible actuator, while the unirradiated area remains in the state of hardening without ultraviolet light irradiation, that is, it maintains the characteristics of being soft and deformable.

[0043] like Figure 5 As shown, the overall deformation fixing mode is specifically as follows: Mechanical constraints are applied to a flexible actuator in a planar state by using a mold with a preset three-dimensional shape or a set of independently controllable fixture arrays, causing it to elastically deform into a preset complex three-dimensional configuration. While maintaining mechanical constraints, global or local ultraviolet light irradiation is applied to the variable stiffness layer, causing all or part of its area to change from a state of hardening without ultraviolet light irradiation to a state of hardening with ultraviolet light irradiation. The mechanical constraints are removed, and the flexible actuator permanently maintains the preset complex three-dimensional configuration due to the hardening and locking of the variable stiffness layer 2, which serves as its new and stable initial shape.

[0044] The mold is a rigid mold with a negative three-dimensional shape of the target; or a jig array can precisely control each degree of freedom to reproduce a complex preset spatial surface.

[0045] Both the local stiffness hardening mode and the overall deformation fixation mode achieve locking and unlocking of the dynamic deformation process through the following steps: Configuration locking step: The flexible actuator is heated in the initial state and the flexible variable stiffness layer 2 is deformed to the preset intermediate configuration by the shrinkage deformation of the driving layer 1. Then, the flexible actuator is rapidly quenched until the temperature is below room temperature, so that the variable stiffness layer 2 region in the UV irradiation hardening state hardens and locks the intermediate configuration due to the sharp increase in its modulus. Configuration unlocking steps: When a configuration change is required, the flexible actuator is heated to a temperature higher than the phase transition temperature of the driving layer 1 and the glass transition temperature of the variable stiffness layer 2, thereby reducing the stiffness of the variable stiffness layer 2 to a soft state. Then, the flexible actuator is allowed to cool naturally and slowly in the environment to a temperature lower than the phase transition temperature of the driving layer 1 and the glass transition temperature of the variable stiffness layer 2, thereby restoring the driving layer 1 from a contracted deformation state to its initial state and the actuator to its initial state. Finally, the above steps are repeated to enter a new deformation cycle. This invention achieves multi-dimensional programmable control of the actuator from local performance to overall configuration by using light-controlled regional selective curing of the variable stiffness layer 2.

[0046] Heating methods include hot air convection heating and infrared radiation heating; quenching methods include ice water bath immersion cooling, vortex tube cryogenic airflow cooling, and cryogenic spray cooling.

[0047] Specifically, such as Figure 6 As shown, the stiffness-adjustable polymer of the flexible actuator of the present invention, after being hardened by ultraviolet light irradiation, can be deformed and locked by adjusting the cooling rate. At room temperature, the actuator is in a vertical initial state. After heating, the stiffness-adjustable polymer softens, the liquid crystal elastomer contracts, and drives the actuator to produce bending deformation.

[0048] If slow environmental cooling is used after deformation, the actuator will gradually return to its initial vertical state. If rapid cold quenching is performed after deformation, such as transferring it to an ice-water bath, the variable stiffness layer will solidify rapidly, locking the bending shape. At this time, the actuator can bear a certain mass load, exhibiting good shape retention and load-bearing capacity.

[0049] By reheating the locked actuator, the stiffness-adjustable polymer softens, releasing the lock and allowing the elastic potential energy stored in the liquid crystal elastomer to be released, causing the actuator to relax significantly. Continued heating will drive the actuator to bend and deform further. If slow cooling is then applied, the actuator can return to its initial shape.

[0050] like Figure 7 As shown, the actuator can be locally programmed via optical programming, giving the area cured by ultraviolet light a deformation-locking function. After the stiffness-adjustable polymer of the actuator head is hardened, the actuator is heated, and the unhardened area begins to deform. When the actuator temperature exceeds the glass transition temperature, the area hardened by ultraviolet light also begins to deform. Continued heating further increases the degree of bending of the actuator. Subsequently, by transferring the sample to an ice-water bath for rapid quenching, the area of ​​the actuator head that has been hardened by ultraviolet light is locked in the bent shape, while the unhardened areas of the actuator return to their original shape. Similarly, the middle, tail, or multiple sections of the actuator can be locally hardened to give these sections a locking function. By slowly cooling the actuator to the environment after heating, the actuator can return to its initial shape.

[0051] like Figure 8As shown, the actuator can be programmed with complex initial shapes via optical programming, giving it complex three-dimensional configurations. When the actuator's initial shape is edited to an S-shape, it bends and deforms after heating, and returns to its original shape after slow cooling. This process of reheating and cooling allows for repeated deformation and recovery. When the actuator's initial shape is edited to a torsion shape, the degree of torsion increases significantly after heating, and it returns to its original shape after slow cooling. After reheating, the torsional shape is locked by transferring the sample to an ice-water bath for rapid quenching. Furthermore, bending and torsion can be combined in a single actuator. By heating and then slowly cooling, the actuator can return to its initial shape.

[0052] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of this invention should be included within the scope of protection of the claims of this invention. The scope of protection of this invention should be determined by the claims.

Claims

1. A flexible actuator with optically programmable configuration and function, characterized in that, include: A driving layer (1) is made of a liquid crystal elastomer material, which deforms under thermal stimulation; A variable stiffness layer (2) and the driving layer (1) are stacked and fixedly connected. The variable stiffness layer (2) is made of a stiffness-adjustable polymer material and is divided into two states depending on whether it is exposed to ultraviolet light. The two states of the variable stiffness layer (2) exhibit different stiffnesses at different temperatures.

2. The flexible actuator with optically programmable configuration and function according to claim 1, characterized in that, The two states are divided into a hardened state without ultraviolet light irradiation and a hardened state with ultraviolet light irradiation: Uncured state without ultraviolet light irradiation: The variable stiffness layer (2) has not been cured by ultraviolet light. The glass transition temperature of the variable stiffness layer (2) is lower than the room temperature. At room temperature, the temperature of the variable stiffness layer (2) is higher than the glass transition temperature of the variable stiffness layer (2). The variable stiffness layer (2) has low stiffness and is in a soft state. Ultraviolet light irradiation hardening state: At least one predetermined region of the variable stiffness layer (2) is irradiated with ultraviolet light, and the glass transition temperature of the predetermined region rises to above room temperature. At room temperature, the temperature of the predetermined region is lower than the glass transition temperature of the predetermined region, and the stiffness of the stiffness-adjustable polymer material in the predetermined region is increased, thereby achieving the hardening state. When the stiffness-adjustable polymer material is in a hardened state after UV curing, it possesses shape memory characteristics. Its stiffness is reduced by heating it above its glass transition temperature, thereby releasing the hardened state and unlocking it. Subsequently, by cold quenching, its temperature is reduced below the glass transition temperature, significantly increasing its stiffness and thus relocking the state. When the stiffness-adjustable polymer material is in a state without UV curing, it always maintains a low-stiffness flexible state.

3. A flexible actuator with optically programmable configuration and function according to claim 1, characterized in that: The liquid crystal elastomer material of the driving layer (1) is a main-chain liquid crystal elastomer pre-oriented by a stretching-ultraviolet crosslinking process. The raw materials for its preparation include, by weight, 100 parts of mesocrystalline unit (RM257), 5.5~6.5 parts of pentaerythritol tetra(3-mercaptopropionate) (PETMP), 20~23 parts of 2,2'-(ethylenedioxy)diethylthiol (EDDET), 0.5~0.8 parts of 2-hydroxy-2-methylphenylacetone (HHMP), and 0.2~0.4 parts of catalyst (DPA). The initial state of the driving layer (1) is formed by heating above its phase transition temperature to form a shrinkage deformation state. The shrinkage deformation state is cooled to below its phase transition temperature to restore the initial state. The stiffness-adjustable polymer (2) material is a UV-curable shape memory polymer system, and its raw materials include, by weight, 12-18 parts of aliphatic polyurethane acrylic resin (AUD), 30-38 parts of tricyclodecanediethanol diacrylate (TCDDA), 35-40 parts of epoxy resin (E-51), 10-15 parts of polyetheramine (D230), and 0.3-0.8 parts of photoinitiator benzoin dimethyl ether (DMPA); The cooling rate of the quenching process is greater than 40℃ / s.

4. A flexible actuator with optically programmable configuration and function according to claim 1, characterized in that: The driving layer (1) and the variable stiffness layer (2) are connected by an adhesive to form a planar sheet structure. The adhesive is a silicone adhesive. The variable stiffness layer (2) in the hardened state is irradiated with ultraviolet light. In the initial state, the variable stiffness layer (2) of the flexible actuator softens after being heated to a temperature exceeding its glass transition temperature, while the drive layer (1) shrinks and deforms after being heated to a temperature exceeding its phase transition temperature, causing the softened variable stiffness layer (2) to deform together. The variable stiffness layer (2) is then quenched to a temperature below room temperature to form a hardened and locked state. The hardened and locked state is released by reheating to a temperature exceeding its glass transition temperature. During the quenching process, the drive layer (1) cannot recover in time compared to the variable stiffness layer (2), causing the variable stiffness layer (2) to harden and lock, while the drive layer (1) is still in a state of shrinkage and deformation. When cooled in a natural environment, the drive layer (1) recovers, thereby causing the variable stiffness layer (2) to recover to the initial state together.

5. A soft robot, characterized in that, It includes at least one flexible actuator as described in any one of claims 1 to 4 as its core actuation and structural unit.

6. A driving method employing a flexible actuator as described in any one of claims 1-4, characterized in that, The driving method includes: It is divided into local stiffness hardening mode and overall deformation fixed mode: The local stiffness hardening mode is to use ultraviolet light to irradiate a specific area of ​​the variable stiffness layer (2) in the initial state to achieve hardening of the specific area; The overall deformation fixing mode is that the flexible actuator is constrained by external forces to form a preset three-dimensional configuration, and the preset three-dimensional configuration is hardened and fixed by ultraviolet light irradiation.

7. The driving method for a flexible actuator according to claim 6, characterized in that, The local stiffness hardening mode is specifically as follows: Obtain a mask with a preset pattern, the pattern corresponding to the geometry and spatial distribution of the preset area on the variable stiffness layer (2) of the flexible actuator. Place the mask on one side of the variable stiffness layer of the flexible actuator and align it so that the preset pattern and the preset area match. Then, use ultraviolet light to irradiate the variable stiffness layer through the mask. After irradiation, the preset area changes from the un-irradiated hardened state to the irradiated hardened state, while the unirradiated area remains in the unirradiated hardened state.

8. The driving method for a flexible actuator according to claim 6, characterized in that, The overall deformation fixing mode is specifically as follows: Mechanical constraints are applied to the flexible actuator in a planar state using a mold with a preset three-dimensional shape or a set of independently controlled jigs, causing it to deform into a preset three-dimensional configuration; While maintaining the mechanical constraints, global or local ultraviolet light irradiation is applied to the variable stiffness layer, causing all or part of its area to change from the un-ultraviolet-irradiated hardened state to the ultraviolet-irradiated hardened state, thereby removing the mechanical constraints. The flexible actuator maintains the preset complex three-dimensional configuration due to the hardening and locking of the variable stiffness layer (2).

9. The driving method for a flexible actuator according to claim 8, characterized in that: The mold is a rigid mold with a target three-dimensional shape; or the fixture array controls each degree of freedom to reproduce a preset spatial surface.

10. A driving method for a flexible actuator according to claim 6, characterized in that: Both the local stiffness hardening mode and the overall deformation fixing mode achieve the locking and unlocking of the dynamic deformation process through the following steps: Configuration locking step: The flexible actuator is heated in the initial state and the shrinkage and deformation of the driving layer (1) drives the variable stiffness layer (2) to deform to the preset intermediate configuration. Then the flexible actuator is subjected to cold quenching treatment so that the variable stiffness layer (2) in the ultraviolet light irradiation hardening state hardens and locks the intermediate configuration. Configuration unlocking steps: Heat the flexible actuator to reduce the stiffness of the variable stiffness layer (2) to a soft state, then let the flexible actuator cool naturally in the environment to restore the actuator to its initial state, and finally repeat the above steps to enter a new deformation cycle.

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