Geoffrey M. Spinks

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

This highlight summarizes the strategies to improve mechanical and actuation performance of hydrogel actuators, which could broaden their potential applications.

Medical soft robotics constitutes a rapidly developing field in the treatment of cardiovascular diseases, with a promising future for millions of patients suffering from heart failure worldwide. Herein, the present state and future direction of artificial muscle‐based soft robotic biomedical devices in supporting the inotropic function of the heart are reviewed, focusing on the emerging electrothermally artificial heart muscles (AHMs). Artificial muscle powered soft robotic devices can mimic the action of complex biological systems such as heart compression and twisting. These artificial muscles possess the ability to undergo complex deformations, aiding cardiac function while maintaining a limited weight and use of space. Two very promising candidates for artificial muscles are electrothermally actuated AHMs and biohybrid actuators using living cells or tissue embedded with artificial structures. Electrothermally actuated AHMs have demonstrated superior force generation while creating the prospect for fully soft robotic actuated ventricular assist devices. This review will critically analyze the limitations of currently available devices and discuss opportunities and directions for future research. Last, the properties of the cardiac muscle are reviewed and compared with those of different materials suitable for mechanical cardiac compression.