Photochemically and Photothermally Controllable Liquid Crystalline Network and Soft Walkers.

Abstract

Developing intelligent soft robots capable to perform various responses to different stimulations has been a hot topic in recent years. Liquid crystalline networks (LCNs) have been considered as one of the most promising candidates in the fabrication of soft actuators because of the combination of elasticity of the polymer and anisotropy of the liquid crystals. However, the design and fabrication of advanced LCN materials with outstanding performances and multiple responsivities is highly demanded but still a challenge. In this work, a NIR-UV dual light-responsive LCN actuator was prepared by selectively coating a polydopamine (PDA) layer on an azobenzene-doped LCN film. This actuator presents UV responsivity in the uncoated region because of the photochemical isomerization of azobenzene and NIR sensitivity in the PDA-coated region originated from the striking photothermal effect. Thanks to the reprogrammable PDA coating, this dual-responsive LCN actuator was totally reprogrammable by coating and washing the PDA layer repeatedly. Based on the novel soft actuator, an artificial car that can imitate the switch of the "forward gear" to "neutral gear" of a real car was prepared. In normal mode, the actuator can move forward under NIR irradiation. After UV light excitation, the actuator cannot move under the same NIR irradiation, just like the car with the level in neutral. This novel actuator may provide inspirations for the fabrication of light-driven functional devices and soft actuators.