Systematic experimental study of pure shear type dielectric elastomer membranes with different electrode and film thicknesses

An approach to reduce the voltage required for dielectric elastomer actuators is to reduce film thickness. However, if the electrode thickness is not similarly reduced, the electrode's mechanical behavior can increasingly and negatively impact the overall actuator behavior. This effect is yet to be studied and quantified for pure shear type specimens; a type recommended in a recent DE standardization journal publication. Therefore, in this work, using pure shear specimens, a comparative study of membrane actuators of different film thickness (20, 50 and 100 μ m) is performed. Electrodes of different thicknesses are screen printed and tested in a uniaxial test device. The stiffening effect due to the solid-state electrodes is demonstrated by performing force-elongation tests for specimens with and without electrodes. Additionally the importance of thin electrodes (relative to film thickness) was demonstrated through a number of electromechanical tests. Isotonic tests revealed a lower electro-mechanical sensitivity for the 20 μ m film when compared with the 50 and 100 μ m films. This was attributed to the relatively thick electrodes. Best actuation results were achieved when the total electrode thickness was at least 15x thinner than the dielectric membrane thickness. (paper)