| The soft actuator is a kind of stimulus response device based on smart materials.It can transform various types of energy（sound wave,light,heat,electricity,chemical,humidity,magnetic field）into its own deformation,displacement and other mechanical changes through the stimulation of surrounding environmental signals,and then realize the scheduled actuation function.The soft stimulus response actuators have great application potential in medical care,sensing,military,post-disaster search and rescue,human-machine interface systems and other fields.According to the response type of soft actuators to the changes of the surrounding environment,there are many driving modes of soft actuators,such as:light field,temperature field,electric field,chemical field,humidity field,magnetic field,etc.Among them,the electrothermal actuator has the advantages of simple operation,high controllability and large shape variable.With the development of materials science,various new smart materials,such as hydrogels,dielectric elastomer,graphene and its derivatives,MXene,and liquid crystal elastomer,have been successfully used in the research and development of electrothermal actuator actuators.Among them,the new two-dimensional material MXene（Ti3C2Tx）has become an ideal material for the preparation of electric heating actuators due to its anisotropic conductivity,large response range,good thermal conductivity,fast absorption and desorption speed with water molecules,and good mechanical stability.However,the common MXene electrothermal actuator is mainly based on a simple double-layer structure,using the difference in thermal expansion produced by joule heat to achieve simple deformation,but it is difficult to integrate its own deformation feedback mechanism,which brings difficulties to the precise control of electric heating actuator,making the actuator still face many problems to be solved in the application of intelligent systems:（1）How to achieve interactive precision control of the action of the actuator,which depends on the structural design of the actuator itself and the advanced sensing and feedback mechanism;（2）How to realize the autonomous decision-making and rapid response execution of the actuator through the system design,which is related to the performance and application scenarios of the actuator;（3）How to make the actuator more intelligent and realize self-adaptation and autonomous response to the environment.The above difficulties seriously limit the application of electric heating actuators in complex environments and specific scenarios.Therefore,the research on the development of the new MXene electric heating actuator and its advanced control mode is crucial for its future application.In view of the above challenges and problems of MXene electrothermal actuator,this paper use laser processing,this kind of soft lithography method without mask,to assist the preparation of MXene electrothermal actuator.On this basis,we have prepared:（1）the integrated actuating and sensing mechanical actuator,and use the closed-loop HMI system to control it;（2）Then,in order to further explore the faster control mode,the autonomous decision-making control system of electrothermal actuator is proposed;（3）Then,in order to enrich the functions of the electrothermal actuator,the color-changing actuator was prepared.In order to further explore the control mode of the multifunctional actuator,the language and color modules,which do not require the participation of limbs,were further proposed.（4）Finally,in order to improve the speed of the actuator movement,we propose the Marangoni robot controlled by the actuator.A series of flexible robot systems are successfully prepared by using the above actuators,respectively:1.Fabrication of MXene electrothermal actuator with integrating actuating and sensing properties and its closed-loop human-machine interface controlA femtosecond laser amplifier was used to fabricate a multi-layer electrothermal actuator with electrothermal response and temperature and pressure sensing functions by treating a composite film coated with double-sided silver gel polyvinylidene difluoride（PVDF）,which has thermal expansion properties,and then coated with thermally contracted MXene.Together with the structural material,the soft manipulator is formed.At the same time,the ion gel adapted to it was prepared as a stretch sensor to identify the bending changes of the user’s finger.After processing by MCU,the bending signal of the finger was converted into an electrical signal to control the movement of the soft manipulator,and the spatio-temporal mapping relationship between the human hand and the soft manipulator was established to form the human-machine interface between the human hand and the manipulator.The mechanical finger can transform its deformation process into a capacitive signal and transmit it to the MCU in real time to adjust its posture to correspond to the spatio-temporal mapping generated by the human hand,and realize the closed-loop control of the soft manipulator.In addition to having executive functions,the soft manipulator can also act as a sensor to recognize the temperature and pressure in the environment.In order to transmit two environmental changes to the user,the Polydimethylsiloxane（PDMS）airbag and heating wire were fabricated with the assistance of carbon dioxide laser and fiber laser to form a feedback device for human hand sensing.Through the above three devices,the MCU connects the three together to realize the closed-loop control of the soft manipulator through the closed-loop interface of human-machine interaction.Finally,the actuator is assembled into the endoscope,and on this basis,the human throat sampling and the pig lung bronchial foreign body sampling are realized,and the human throat sampling samples are tested for influenza A/B virus antigen.It provides a new idea for the practical application scenario of electrothermal actuators.2.The autonomous decision-making control system of MXene electrothermal actuatorBased on the actuator of 1,in order to reduce the time consumed in the control process,a rapid response PDMS@MWCNTS（Multi-walled carbon nanotube）porous pressure sensor was prepared.Inspired by the knee hop reflex,a control mode bypassing MCU was designed to control the electrothermal actuator by adjusting the size of the reference resistance.When the pressure sensor receives the external pressure,the pressure signal is generally converted into the electric signal of the control actuator after processing by MCU.In this paper,through the design of the circuit,the pressure signal is directly converted into the electric signal of the control of the electric actuator,so that it can respond quickly.This control mode gives the electric actuator the ability to make independent decisions.In addition,by adjusting the size of the reference resistance,it is designed to prevent the user from jitter and excessive force,which will cause disturbance to the movement process of the electric heating actuator and damage to the target contacted by the electrothermal actuator.3.Color-changing MXene electrothermal actuator control by voice and environment adaptive color changeIn work 1,2,the function of MXene electrothermal actuator is relatively single.Facing the lack of adaptability in complex environment,in order to improve the adaptability of MXene electrothermal actuator,inspired by the phenomenon that tree frogs change their body color in response to changes in environmental color to blend in with the natural environment,a color-changing actuator was prepared.Based on the actuator of 1,and heat sensitive pigment is coated on the other side as the color change layer.The bionic soft actuator is composed of 5 layers of main materials.MXene has good infrared shielding effect under the condition of no heating,so the actuator coated with MXene has good infrared shielding function.The Joule heat generated by MXene during the power-on process causes the expansion of PVDF and the contraction of MXene,resulting in a mismatch between the two layers,resulting in a bending toward the MXene side to achieve the actuation function.Due to the heat generated by MXene,the thermal effect on the heat sensitive pigment leads to its color change and endows the actuator with the function of color change;And the heating process can produce heating in the direction of the target object,so the actuator has the heating function.In order to control the actuator better,The color recognition module is used to realize the adaptive color change of artificial flowers based on the actuator,and the voice recognition module to control the array of 1*5actuators;a multi-function actuator as a single actuation unit to integrate into the fabric to form intelligence fabric,which realizes the control of the fabric’s air permeability,the heating of the fabric on the human body,the infrared shielding of the fabric on the human body,and the fabric can change the color change,the cloth can change the color,which can become white in the alpine snow field and reduce the air permeability and heating function of the clothing,and turn green in the jungle in summer to increase the conversion of air permeability and infrared shielding characteristics.It provides a new idea for the practical application of soft actuators in smart clothing.4.Electrothermal/photothermal MXene actuators and their application in bionic insect robotsIn order to solve the problem of insufficient movement speed of the bionic insect robots,the laser soft lithography technology was used to obtain an actuator controlled by electric and photothermal MXene.Through the design of the air bag inside the actuator,when its temperature changes,the air in the designed chamber inside the robot will expand to drive the fuel movement and realize the control of fuel release inside the robot.The surface tension difference between chemical substance and water and the force generated by the fuel diffusion process in water are used to actuate the robot movement,and the switch control of chemical Malangani robot is solved.In order to further realize better control of the robot,a T-type microfluidic junction is designed to realize programmed release of the fuel and air segments.The Tesla valve is used to solve the problem of fuel reflux when the light is stopped,and the control efficiency of the optical switch is enhanced.The surface of the flexible actuator is treated with a laser modified scheme,and a super hydrophobic surface is obtained,which reduces the movement resistance of the bionic flexible actuator on the water surface.The bionic flexible actuator designed by laser assisted machining is integrated,and the miniature camera is assembled.The application of the bionic Marangoni robot in the natural environment is realized for the first time,which provides a new idea for the practical application of Marangoni robot. |
