The transverse strain response of electroactive polymer actuators

Abstract

Abstract-Some electroactive polymers show large electric-fieldinduced strain. However, it is difficult to characterize the transverse strain response, especially the dynamic response, under high driving electric fields. In this work, a transverse strain measurement system based on a ZYGO laser Doppler interferometer has been developed. This system can measure transverse strain responses of polymer actuators of different sizes over a wide displacement and frequency range. By using this system, we have investigated the electric-field-induced strains of electroactive polymer actuators fabricated from silicone (Dow Corning HSIII RTV) films. The static and dynamic strains of the actuators have been measured under various driving electric fields and mechanical loads. Our results show that the polymers exhibit a non-linear relationship between strain and driving field. Mechanical loads have a significant effect on transverse strain responses. Transverse strains of 3.25% (static) and 2.08% (dynamic at 1 Hz) have been obtained under a load-free condition. Our experimental results can be understood on the basis of hyperelastic theory. The actuation of an electroactive polymer actuator is not only determined by its material properties, but also by the actuator structure.

The strain response of silicone dielectric elastomer actuators

“…This happens because the electrostatic attraction that causes the Maxwell stress only occurs over the electroded area whereas the elongation is measured over the entire film including the non-electroded inactive areas and so, when the inactive areas are relatively smaller the elongation is larger. Figures 10 and 11 also show that the elongation first increases with pre-strain, reaches a maximum at a pre-strain of around 15% and then decreases as the pre-strain is further increased, which is similar to earlier observations 5,6,7,8 . In Figure 12 the FEA model predictions for the electric-field-induced elongation as a function of pre-strain for the HSIII silicone specimen with the narrow inactive edge are compared with our observed values for various applied electric fields.…”

“…This assumption is fairly good if the film actuator is narrow enough (the ratio of the length to the width is 10:1). Our detailed experimental investigations of the transverse strain response of silicone and polyurethane elastomers 5,6,7,8 suggested that the geometry as well as the material properties determined the measured strains. High transverse strain required not only good material properties, but also optimized actuator geometry.…”