Design And Controllable Preparation Of Dielectric Elastomer Materials And Fibrous Actuators

Dielectric elastomer(DE)as next generation artificial muscle,could generate large deformation excited by the external electric field,enabling electric energy and mechanical energy transformation.The dielectric elastomer could be widely used as soft actuators,sensors and energy collection devices in the soft robot,aerospace,medical rehabilitation,and other fields.At present,the widely used DE have been screened from the commercial elastomers,which are not designed for DE.On the other side,the fabrication of DE devices of highly integrated,complex structure with multiple actuators is of challenge in a tailor-made,continuous,automatic and large-scale way,which limits the potential application space of DE.To address these issues,we design and prepare new triblock copolymer dielectric elastomer materials with excellent performance;and develop a 3D printing method of fibrous DE actuators and fabricate integrated structures with multiple actuators.The main innovative achievements are as follows:(1)A series of poly(styrene-b-alkylacrylic-b-styrene)DE materials were well designed and prepared by RAFT emulsion polymerization technology.The influence of side groups of acrylates on the mechanical properties,dielectric properties and actuating properties of the polymers was investigated.It was found that with increasing of side group size,the triblock copolymer should exhibit lower modulus due to lower entanglement density.The maximum actuation strain of polystyrene-poly(2-ethylhexyl acrylate)-polystyrene(25%at 28 kV/mm,without prestretching)and energy density(4.4 kJ/m3)were comparable with those of the mammalian skeletal muscle.(2)The 3D direct ink writing method was developed to fabricate DE fiber actuators.The method features with tailor-making ability and a continuous,automatic and large-scale process.The actuation performance of dielectric elastomer fiber could be compared with the reported optimal value of fibrous actuators.The actuation strain could reach up to 14%and the breakdown field strength was more than 60 V/m with good repeatability.By this method,we,for the first time,fabricate large-scale,multi-specification and multi-size dielectric elastomer fiber bundle drives,which showed the characteristics of fast response,scalability,damage tolerance,addressability,programmability and reconfiguration.This could open a new avenue to prepare more complex and dexterous soft machines.(3)A soft shape-morphing device with highly integrated and complex multi-actuators was able to be fabricated by the digital design and the 3D direct ink writing method.The structure of DE actuators,geometry and electrode design could be spatially programmed,leading to the complex shape-changing,including two-dimensional to three-dimensional,three-dimensional to three-dimensional shape switching.This would greatly expand the structure of dielectric elastomers devices and their applications.(4)Based on the law of energy conservation,the mathematical model of electro-mechanical performance of DE fiber actuator was established,which predicted well the experimental result.This model was able to guide structure design and material selection of DE fiber actuators.