Liquid-phase drawing of LCE/CNT composites for electrothermal actuators

Monodomain liquid crystal elastomers with excellent reversible contraction deformation under a heat stimulus have broad application prospects in artificial muscles, soft robots, and micromechanical systems. Greater control can be achieved in a flexible actuation process through the generation of Joule heat by electricity. Herein, a highly conductive liquid crystal elastomer fibre actuator (c-LCF) was continuously prepared via liquid-phase drawing, with a conductivity of up to 12.5 S/m at 30 ℃. High conductivity is realised by the semi-wrapping combination of the main-chain liquid crystal prepolymer and carbon nanotube/carbon black to achieve a high-concentration dispersion of multi-dimensional conductive carbon nanomaterials. The fabricated c-LCF had a negative temperature coefficient, which is favourable for controllability and fast electrothermal actuation. The c-LCF contracted by approximately 30 % under a load of 1 MPa with a current of 9 mA (28 V/cm, 252 mW/cm). Its output power density reached 0.94 kJ/kg, indicating a better performance than biological muscle fibres; thus, it can be used to construct high-load bio-muscles. The different structures constructed by the c-LCF and fibre bundles can realise different electric actuation modes. In addition, fast driving can be realised using an elastic instability structure. The applications of liquid-crystal elastomers will be significantly broadened by this research.