An enhanced flexoelectric dielectric elastomer actuator with stretchable electret

Actuation has been applied with dielectric elastomers (DE) in soft robotics and bio-mimic devices due to their ultra-large deformation range, easy patterning, light weight, and they are highly expected for high electro-mechanical efficiency and low stimulating power. Flexoelectricity describes the strain gradient-induced electric polarization, which is strongly related to geometry and deformation ranges. The electro-mechanical coupling effect with flexoelectricity in elastomeric materials are then highly expected. In this work, elastic modulus gradient of a DE actuator is designed for bending motion by flexoelectricity, and electric charge is inserted and immobilized inside the material to further enhance the electro-mechanical capability. Elastic modulus gradient is designed, and electric charges are immobilized to enlarge the electro-mechanical coupling efficiencies of this flexoelectric actuator. The bending angle of the actuator is inversely proportional to the cube of general thickness of actuator, and the immobilized electric charge extensively enlarged the actuation capability. With elastic modulus gradient and electret, the actuating bending angle is enlarged with low stimulating voltage. This work provides an enhanced flexoelectric actuating method with material and mechanical design, and highlights low-voltage actuating approach with piezoelectric-like effect of stretchable electrets.