Electroactive Artificial Muscle with Macroscopic Stroke Enabled by Liquid Crystal Plasticizing

Abstract

Electroactive artificial muscles, represented by dielectric elastomer actuators, provide advantages such as flexibility, adaptability, and lightweight properties, enabling applications in soft electronics, soft robotics, and bionic machinery. However, dielectric elastomer actuators are limited by a constrained driving stroke of less than 0.2 mm despite achieving an area strain that exceeds 200%. The restricted stroke necessitates a complex structural design for actuators, often involving multilayer configurations and rolled elastomer designs, making it difficult to achieve macroscopic strokes like biological muscles. Additionally, dielectric elastomers typically exhibit considerable hysteresis (1 kJ m–3 to 2 MJ m–3). Inspired by biological muscles, which possess a significant amount of sarcoplasm that reduces hysteresis performance, we propose a strategy using a polyacrylate elastomer plasticized with the electroactive liquid 5CB. By adding 70% 5CB, the liquid fillers effectively lower polymer chains friction and incorporate dipole groups, which reduces hysteresis by 3 orders of magnitude and improves the electrical-mechanical coupling signals. Consequently, our PTMCHA/5CB gel muscle demonstrates an impressive stroke of 3.06 mm under a low electric field of 1.3 kV mm–1, which is 20 times greater than the stroke achieved by the current state-of-the-art single-layer dielectric elastomer. This gel presents promising opportunities for soft actuators and intelligent sensing systems.