Single-Layer and Stack Dielectric Elastomer Actuators Using Polysiloxanes Modified with Ethylsulfonyl Groups

Dielectric elastomer actuators (DEAs) are soft transducers well-suited to precise motion applications in robotics and prosthetics. However, low dielectric permittivity or very soft elastomers result in a high operating voltage or low force output. These issues can be mitigated using high dielectric permittivity elastomers in a stack actuator. To optimize electromechanical performance, we synthesized high-permittivity polysiloxanes with varying ratios of ethyl sulfonyl thioether and butane thioether groups. The best material exhibited a dielectric permittivity of 16.2 at 10 kHz and 25 °C, a low conductivity of 1.8 × 10^-10 S cm^-1, and a large lateral actuation strain of 13% at a low electric field of 8.2 V μm^-1 (1 Hz, 900 V), whereas state-of-the-art nitrile- and methyl sulfonyl-functionalized polysiloxane required electric fields exceeding 20 V μm^-1 for the same actuation. A stack of five single-layer actuators using this material as the dielectric exhibited a thickness strain of 4.5% at a low electric field of 14.5 V μm^-1 (1 Hz, 1600 V). The stack actuator showed stable performance at 1200 V over various frequencies, including 5 and 10 Hz, and maintained a reversible actuation over 4000 cycles at 1 Hz.