Dielectric elastomer film actuators: characterization, experiment and analysis

Silicone is a common dielectric elastomer material. Actuators made from it show excellent activation properties including large strains (up to 380%), high energy densities (up to 3.4 J g(-1)), high efficiency, high responsive speed, good reliability and durability, etc. When a voltage is applied on the compliant electrodes of the dielectric elastomers, the polymer shrinks along the electric field and expands in the transverse plane. In this paper, a silicone dielectric elastomer is synthesized and the area strains are tested under different electric fields. Pre-strain and a certain driving electric field are applied to the film and the induced large strain by the Maxwell stress is measured. Barium titanate (BaTiO3) was incorporated into the silicone to fabricate a new dielectric elastomer: the experimental results show that the elastic modulus and dielectric constant were significantly improved. The experimental results coincide well with those of finite element analysis at a large deformation. Also, a theoretical analysis is performed on the coupling effects of the mechanical and electric fields. A nonlinear field theory of deformable dielectrics and hyperelastic theory are adopted to analyze the electromechanical field behavior of these actuators. Also the mechanical behavior of the dielectric elastomer undergoing large free deformation is studied. Finally, the constitutive model of a dielectric elastomer composite under free deformation and restrained deformation is derived.