Advanced Dielectric Elastomer Actuators Based On Thermoplastic Polyurethane Blends

As an advanced flexible actuator,the dielectric elastomer actuators(DEAs)have a bright future in the field of artificial muscles,flexible intelligent robots,and other applications.How to design and prepare a new type of elastomer material,which could produce a substantial shape deformation under a small electric field,is a frontier research topic in the field of dielectric elastomers.This thesis mainly investigates on thermoplastic polyurethane dielectric elastomer actuators.The goal is to establish a kind of polyurethane elastomer with improved and controlled electromechanical actuation performance,and in-depth understanding of the underlying principle.This thesis uses the method of solution assisted casting to prepare elastomer films.A series of modified polyurethane films were prepared,and further processed into thin film diaphragm actuators.From the material structure design,the mechanical properties,the dielectric properties,and two aspects of the boundaries some guiding principles was set up for improving the performance of electric field driven polyurethane actuators.The electromechanical properties of the elastomer are positively correlated with the electromechanical sensitivity(i.e.,the ratio of the dielectric constant to the young's modulus).In order to improve the performance in electric field induced strain of polyurethane elastomer,we tried several ideas:one is the introduction of polar azo dye molecule to improve its dielectric constant,the second is by adding plasticizer to decrease the young's modulus,and the last is a composite,through building blends with bicontinuous structure obtained with a silicone rubber elastomer material which has a better electromechanical sensitivity than the polyurethane.These three kinds of elastomer materials can be applied to a certain extent,which can be used to improve the performance of thermoplastic polyurethane.Among them,the blend with the bicontinuous structure reached the best results in practical condition with an areal strain of 3.8%at 40V/?m stable even after at least 50 cycles.In addition,we also focus on the influence of the size of the device and the rising rate of the driving electric field on the electromechanical performance of the plasticized thermoplastic elastomer,and found experimentally and theoretically that the current leakage,the viscoelasticity,the electrostatic forces and its corresponding mechanical work could be modulated by the control of these two parameters to further control the electric field driven response of the actuators.