Facile Integration of Bacterial Cellulose with Liquid Crystal Elastomers Enables Robust Biomimetic Helical Yarn Actuators

Inspired from helical structures in nature, liquid crystal elastomer (LCE) fiber actuators are developed for soft robotics and smart wearables. However, the facile development of robust LCE yarn actuators remains challenging due to the lightly cross-linked networks of LCE with the inherently poor mechanical properties. Here, the bionic helical yarn actuator is constructed through integrating the shape-morphing LCE fiber as the actuation phase and the highly ordered orientation biomass bacterial cellulose (BC) macrofibers as the reinforcement phase by a facile twisting and two-step cross-linking strategy. Thanks to the 3D nanofiber network inside BC macrofibers and biomimetic helical structure, the mechanical strength (43.9 MPa) and the creep phenomenon of the resulted yarn have been significantly improved, which are obviously better than the reported LCE fiber actuators (1.4-30.8 MPa). The designed LCE/BC helical yarn actuators demonstrate high work capacity (304.1 J kg^-1) and reliable reusability. As a proof-of-concept, this work constructs micro rolling device with customizable speed, soft gripper for grasping and moving heavy objects and passive micro motor with a speed of 7.7 rad s^-1. The findings of this work are expected to provide insights into the development of high-performance and durable smart yarn actuators through biomimetic engineering strategies.