Review of Electrohydraulic Actuators inspired by the HASEL Actuator

Abstract

The muscle-like movement and speed of the electrohydraulic actuator have granted it much at-tention in soft robotics. Our aim is to review the advancements in electrohydraulic actuators in-spired by the Hydraulically Amplified Self-healing Electrostatic (HASEL) actuator. With this paper we focus on the performance of 21 electrohydraulic actuator designs developed across five Uni-versities, ranging from the earliest HASEL designs to the latest electrohydraulic designs. These actuators reported up to 60 N forces and contracting strains of up to 99%. The actuator with the best overall performance so far, has been the HEXEL actuator, developed at the University of Colorado Boulder. However, notable is also the HALVE actuator (produced by ETH Zürich, Switzerland), that by using a 5µm PVDF-TrFE-CTFE film with a relative permittivity 40, produced 100 times the electrostatic force of any of the electrohydraulic actuators under review. The latter shows that there is room for improvements as low force and displacement still limit the viability of the soft actuators in real-life applications.