Actuating and Sensing Composites of Liquid Crystal Elastomers and Poly(ionic liquid)s

ABSTRACT Multifunctional composite materials integrating a poly(ionic liquid) (PIL) into a liquid crystal elastomer (LCE) are developed. 3D‐printable inks comprising a liquid crystal oligomer (LCO) and a PIL at various compositions are obtained and their printing results in LCE/PIL actuators, in the form of semi‐interpenetrating polymer networks (semi‐IPN), which preserve a large reversible deformation upon thermally or photothermally induced order‐disorder phase transition of mesogens in the LCE phase and, in the same time, exhibit electrical resistance variation upon temperature change and deformation, due to percolated PIL domains forming ionic conductive paths in the composite material. Under ambient conditions, the printed LCE/PIL filaments, which are mechanically tough, flexible, and stretchable, can have their multiple deformation modes monitored by distinct relative resistance change signals. Moreover, the electrical self‐sensing of photothermally‐driven actuation while excluding the thermal effect is achieved, and an actuation‐enabled increase in temperature sensing function is demonstrated. The method demonstrated using LCO/PIL 3D ink provides a simple, efficient, and scalable approach for designing and fabricating electrically responsive LCE actuators, opening up new prospects for applications such as wearable electronics and soft robotics.