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

## TL;DR

This paper introduces a new type of soft actuator material that requires lower voltage and performs better than existing options.

## Contribution

A novel high-permittivity polysiloxane material with ethylsulfonyl groups is developed for efficient dielectric elastomer actuators.

## Key findings

- The new material achieved a dielectric permittivity of 16.2 at 10 kHz and 25 °C.
- It enabled a lateral actuation strain of 13% at a low electric field of 8.2 V μm–1.
- A stack of five actuators showed stable performance over 4000 cycles at 1 Hz.

## Abstract

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.