Preparation And Application Of Thermotropic Liquid Crystal Elastomer Actuator

Liquid crystal elastomer(LCEs)is a shape memory material with stimulus response performance.It combines the orientation of liquid crystal with the entropy elasticity of polymer.Its shape can change reversibly along the alignment direction of liquid crystal unit under external stimulation,and has a high degree of human-computer interaction security.Therefore,the actuator made of this material has great application prospects in artificial muscle,micro software robot,biomedicine and so on.However,due to the properties of its own flexible materials,the shrinkage deformation driving force of LCEs is usually not prominent,which is difficult to be applied to actuators with large driving force requirements.In addition,the device formed by conventional LCEs collimation processing is difficult to realize multi-dimensional motion.In view of the above problems,the preparation and application of thermotropic liquid crystal elastomer materials are studied in this paper.The specific research contents and main conclusions are as follows:(1)Preparation and application of one-dimensional thermally actuated liquid crystal elastomer films.Thermotropic liquid crystalline elastomer films were synthesized by RM257 liquid crystal monomer.The phase transition temperature was 71.4 ℃ and the thermotropic shrinkage was 47 %.Based on the film,the dot matrix structure with cone like protrusions is prepared by one-time molding,and then combined with the stretchable flexible electrothermal layer to realize the controllable expansion of the convex starting point array,with a height shrinkage rate of up to 80 %.Combined with the design of signal transmission module and control module,a multi sensing flexible Braille display and interaction device is prepared.The device can realize the delay free pressing input and height temperature multi sensing output of Braille dot matrix.(2)Preparation and application of multi-dimensional thermally actuated liquid crystal elastomer films.A gradient crosslinked polymer network structure was constructed inside the thermotropic liquid crystal elastomer by solvent treatment,combined with mechanical tensile alignment and secondary light curing crosslinking,as well as the preparation of sheet electromagnetic coil and electric heating layer by enamelled wire,and the thermotropic liquid crystal elastomer film with multi-dimensional movement ability such as bending and rotation was prepared.Based on the film,a crawling soft robot and a flexible gripper are prepared.Through electro-magnetic control,the crawling speed of the crawling soft robot can reach 3 mm / s,and the vertical crawling of a specific metal surface is realized;The flexible gripper can realize the wrapped grasping movement imitating flytrap.(3)Preparation and application of thermally actuated disulfide based liquid crystal elastomer films.By introducing dynamic covalent bond and regulating the crosslinking density,thermotropic liquid crystal elastomer films with different crosslinking States and splicing can be prepared,and multi-dimensional actuation can be realized after splicing.At the same time,combined with the embedded electric heating plate,the liquid crystal elastomer actuator with "sandwich" structure is prepared,which can realize electric control bending.In addition,based on the ability of the actuator to be spliced again,the bending motion can be combined twice,which expands the motion mode of the liquid crystal elastomer actuator.