Novel multilayer electrostatic solid state actuators with elastic dielectric (Invited Paper)

Abstract

Solid state actuators provide deformation and actuation forces mainly excited by electric fields. Piezoelectric actuators are well established providing high forces at low strain due to their material characteristic. Electrostatic solid-state actuators consist of elastic dielectric layers between compliant electrodes. Applying electric fields of up to 100 V/μm at the electrodes the dielectric contracts due to electrostatic forces and expands in orthogonal direction. We use high elastic silicone elastomers with thin graphite powder electrodes. In order to increase the absolute strain values at limited voltage, we have developed a novel multilayer process technology to fabricate elastomer stack actuators with up to 100 layers. The electromechanical properties of the actuators have been evaluated theoretically and characterised experimentally. Maximum strain values up to 20% for prestressed multilayer films have been achieved. The novel multilayer fabrication technology provides multilayer stack actuators with various electrode patterns like universal linear actuators or matrix arrays for a wide range of applications as tactile displays for telemanipulation or Braille displays. The strain in vertical direction versus driving voltage shows a hysteresis due to viscous friction in the elastomer layers. These measurements correspond to a viscoelastic theoretical model. The mechanical stress versus strain characteristic shows a strong nonlinearity for strains > 30%. The dynamic characteristic has been evaluated by measuring the mechanical impedance in the frequency range of 2 to 1000 Hz.