In Situ Programmable Electrothermal Actuation of Liquid Crystal Elastomer Fibers Assisted by Microfluidics

Electrothermal liquid crystal elastomer (LCE) fibers have attracted much attention with the development of soft robots and smart fabrics. However, for currently reported electrothermal LCEs, their driven circuits are fixed and not rewritable, limiting their potential of adapting to various applications. In this study, we propose an electrothermal actuation method based on microfluids for LCE fibers. In this method, two types of liquid metals (LMs), namely, Hg and Ga, are injected into an LCE hollow fiber to form a driven circuit. The distribution of LMs is programmed using a microfluidic pump by controlling the injection. Owing to the different electrothermal effects of the two LMs, the fiber section comprising Hg with a higher resistivity can be designed to contract more than Ga with a lower resistivity. Therefore, a specific driven circuit inside the fiber results in a corresponding deformation mode upon electricity. Owing to the fluidity of LMs, the driven circuit can be easily re-expressed by injecting fresh LMs, enabling a single LCE fiber to realize diverse deformation modes. The proposed method can enhance the functionality of LCE and pave the way for the development of other electrothermal-actuated materials and actuators.