Nanocomposite Actuators with Dielectric Fluids

Electrically actuated dielectric elastomers are promising materials for applications in soft robotics due to their ability to produce controllable strains in a variety of configurations. Recent research has investigated macroscale actuation in commercially available elastomeric films, with the primary focus being on the effects of actuator geometry and electrode materials. The pursuit of greater displacements in these elastomers has often come through increased compliance at the expense of dielectric strength. The inclusion of a secondary dielectric fluid phase in an elastomeric matrix could allow for more compliant actuators without a drastic decrease in breakdown strength. This second phase could also be used to optimize the viscoelastic and electromagnetic properties of the composite material, effectively allowing one to tune its actuation response. In this work, multiphase elastomer films were fabricated by polymerizing nanoemulsions comprised of monomer, dielectric fluids, and emulsion-stabilizing nanoparticles. Elastomer composite films were applied to metallized polymer substrates using conductive pastes or PVD films as the opposing electrode. Film thickness and structure were characterized via optical profilometry and variable-pressure scanning electron microscopy. Actuation for cantilever configurations was measured using a laser triangulation displacement, with some displacements visible to the naked eye. Composite actuators exhibited significantly improved cantilever displacement performance and a lower elastic modulus compared to their homogeneous counterparts, where the magnitude of actuation increased with both voltage and second phase volume fraction. These actuators were also able to withstand high operating voltages, with an average dielectric strength of 20 kV/mm.