High-Permittivity Polysiloxanes for Solvent-Free Fabrication of Dielectric Elastomer Actuators

Abstract

Dielectric elastomer actuators (DEAs) are a class of soft transducers with broad potential applications in soft robotics. DEAs consist of two stretchable electrodes on a dielectric elastomer, which deform and generate force when charged. The generated force is increased by placing many DEAs on top of one another to form a stack actuator. Next-generation stack actuators require high permittivity inks that are solvent-free processable and cross-linkable into thin elastic films. Here, a process toward elastomers with tuneable permittivity that can be prepared solvent-free is reported. Polycondensation of chlorosilanes yields polymers with vinyl end-groups and cross-linkers with multiple hydrosilane groups that both carry polar chloromethyl groups. Their dielectric permittivity and mechanical properties are tuned by changing the polar group content and the molar mass of the vinyl-terminated polymer, respectively. Solvent-free doctor blading provides thin films, which are cross-linked by heating. DEAs prepared from the films reach a lateral actuation of promising 4.6% at a low electric field of 11.2 V µm-1 and can be operated at frequencies up to 5 Hz. The high-permittivity polymer ink is used in a solvent-free layer-by-layer stack actuator fabrication, which yields an actuator with three active layers that gives a thickness strain of 1.0% at 12.4 V µm-1.