Dielectric elastomer actuators using Slide-Ring Material^® with increased permittivity

The inclusion of high permittivity nanoparticles in elastomeric materials for dielectric elastomer actuators (DEAs) is one promising method to achieve large strain at relatively low applied voltages. However, the addition of these nanoparticles tends to increase the stiffness of the elastomer and disturbs the actuation of the DEA. This is attributed to restriction of the chain motion in the elastomer by the nanoparticles. Slide-Ring Material^® (SRM) is a cross-linked polymeric material with freely movable cross-linking sites. The internal stresses in this structure are dramatically homogenized by the pulley effect; therefore, the restriction of chain motion due to the nanoparticles is expected to be significantly reduced. We have employed SRM as a host elastomer for a DEA with the addition of ferroelectric BaTiO₃ (BT) nanoparticles. The effects of BT addition on the permittivity, stiffness and viscosity of the SRM–BT nanocomposites, and the actuation strain of DEAs using SRM were evaluated. The permittivity of the nanocomposites increased linearly with the concentration of BT and reached 3.6 times that for pure SRM at 50 wt%. The elastic modulus and the viscosity remained almost constant up to 20 wt% and then decreased above this concentration. The actuation strain of a planar actuator using SRM and 50 wt% BT was four times larger than that of the DEA with pure SRM. (paper)