Crack-resistant and tissue-like artificial muscles with low temperature activation and high power density.

Constructing soft robotics with safe human-machine interactions requires low-modulus, high-power-density artificial muscles that are sensitive to gentle stimuli. In addition, the ability to resist crack propagation during long-term actuation cycles is essential for a long service life. Herein, for the first time, we propose a material design to combine all these desirable attributes in a single artificial muscle platform. Our design involves the molecular engineering of a liquid crystalline network with crystallizable segments and an ethylene glycol flexible spacer. A high degree of crystallinity could be afforded by utilizing aza-Michael chemistry to produce a low covalent crosslinking density, resulting in crack-insensitivity with a high fracture energy of 33720 J m -2 and a high fatigue threshold of 2250 J m -2 . Such crack-resistant artificial muscle with tissue-matched modulus of 0.7 MPa can generate a high power density of 450 W kg -1 at a low temperature of 40 °C. Notably, because of the presence of crystalline domains in the actuated state, no crack propagation was observed after 500 heating-cooling actuation cycles under a static load of 220 kPa. This study points to a pathway for the creation of artificial muscles merging seemingly disparate, but desirable properties, broadening their application potential in smart devices. This article is protected by copyright. All rights reserved.