Digital light processing of liquid crystal elastomers for self-sensing artificial muscles.

Li, Shuo; Bai, Hedan; Liu, Zheng; Zhang, Xinyue; Huang, Chuqi; Wiesner, Lennard W; Silberstein, Meredith; Shepherd, Robert F · Sci Adv · 2021

basic_science · Level V

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Abstract

Artificial muscles based on stimuli-responsive polymers usually exhibit mechanical compliance, versatility, and high power-to-weight ratio, showing great promise to potentially replace conventional rigid motors for next-generation soft robots, wearable electronics, and biomedical devices. In particular, thermomechanical liquid crystal elastomers (LCEs) constitute artificial muscle-like actuators that can be remotely triggered for large stroke, fast response, and highly repeatable actuations. Here, we introduce a digital light processing (DLP)-based additive manufacturing approach that automatically shear aligns mesogenic oligomers, layer-by-layer, to achieve high orientational order in the photocrosslinked structures; this ordering yields high specific work capacity (63 J kg<sup>-1</sup>) and energy density (0.18 MJ m<sup>-3</sup>). We demonstrate actuators composed of these DLP printed LCEs' applications in soft robotics, such as reversible grasping, untethered crawling, and weightlifting. Furthermore, we present an LCE self-sensing system that exploits thermally induced optical transition as an intrinsic option toward feedback control.