Research On Construction And Actuation Behavior Control Of Smart Actuators Based On Nano Composites

Smart actuators that can convert external energy stimuli（e.g.,electric,light,heat,humidity,chemical vapor,etc.）into mechanical work have attracted great attentions due to the considerable potential applications in the fields of artificial muscles,soft robotics,sensors,flexible electronics,and biomimetic devices,etc.With the increasing demand for the performance of smart actuators,traditional smart actautors can not meet people’s needs,so that it is necessary to develop new types of high-performance smart actuators.Nano materials such as carbon nanotubes and MXene can be assembled into various macro structures,and they have been used to develop new types of smart actuators due to their special mechanical,electrical,optical,and thermal properties.However,the improvement of material properties on the performance of smart actuators is still very limited.In this paper,based on the excellent performance of nano materials and combined with cross-scale structure design,we can construct new types of high-performance smart actuators by compounded nano materials with polymers.The driving mechanism of the actuators are also analyzed and described.In addition,the functionality of smart actuators is expanded,and its potential application prospect is explored.The main research contents are as follows:In order to solve the problems of uncontrollable deformation,low output stress,slow response speed,and difficult independent deformation recovery of traditional smart actuators,a carbon nanotube composite yarn actuator with variable stiffness is designed and fabricated.The carbon nanotube spiral yarn with spring-like structure was fabricated by pre-stretched the carbon nanotube spiral yarn and inflated epoxy resin into the spiral yarn.Based on the good electrothermal and photothermal effect of carbon nanotubes,and the temperature-sensitive modulus of epoxy resin,this carbon nanotube composite yarn actuator can realize reversible driving deformation behavior under the condition of applied voltage or light irradiation,and its driving deformation and output stress can be controlled by adjusting the applied voltage or light intensity.The maximum contractive srtain of this carbon nanotube composite yarn actuator can reach to 12%,and the maximum output stress can reach to 12 MPa,which is about 40 times that of human skeletal muscle fiber.Based on the electric-induced and light-induced actuation behavior of this carbon nanotube composite yarn actuator,an electronically controlled clamping device and an optically controlled switch are designed,which show the potential application prospect of the carbon nanotube composite yarn actuator.Most of current smart actuators can only realize simple driving deformation behavior,but can not give real-time feedback to their deformation process.In order to solve this problem,we compounded Ti₃C₂T_x MXene with high conductivity and PDMS with good mechanical property,and fabricated MXene/PDMS bilayer composite film.Due to the difference of thermal expansion coefficient between MXene and PDMS,interfacial thermal stress will be generated between MXene layer and PDMS layer,so that this MXene/PDMS composite film with bilayer structure has a rolled initial shape.Based on the good photothermal effect of Ti₃C₂T_x MXene,the thermal shrinkage of MXene and the large thermal expansion coefficient of PDMS,this MXene/PDMS composite film with bilayer structure can realize the driving deformation behavior from rolled state to flat state under light irradiation.More importantly,due to the good conductivity of MXene,the deformation process of this composite film actuator can be fed back in real time by monitoring the resistance change of MXene layer,so as to realize the integrated function of actuation and sensing.Based on this,the touch sensing function of the MXene/PDMS bilayer composite film actuator is realized.In addition,several bionic applications have been demostrated by using this MXene/PDMS composite film actuator with bilayer structure.For the difficulty of achieving energy storage and release control in most of smart actuators,a MXene-based bilayer composite film actuator with a closed structure has been designed and fabricated by simulating the jumping behavior of gall midge larvae.Due to the existence of the latch structure,this MXene-based bilayer composite film actuator can realize a large amount of energy accumulation and instantaneous release under light irradiation,and the deformation speed of this actuator can reach to 6000°/s.Based on this MXene-based bilayer composite film actuator,an untethered soft jumping robot which can produce jumping motion under light irradiation is designed.The jumping mode（e.g.,horizontal long jump and vertical high jump）of this robot can be controlled by adjusting the light irradiation angle.Its maximum jumping height can reach to 41 mm,which is about 10.3 times that of its own body height.The robot can also jump under the condition of carrying a load about 0.5 times its own weight.In addition,based on this MXene-based bilayer composite film actuator with a closed structure,a rolling robot is also designed and fabricated,which can produce continuous and autonomous rolling motion under continuous light irradiation.