Polydopamine-Coated Gold Nanorods for Liquid Crystal Actuators Driven by Near-Infrared Light

Utilizing the photothermal effect to fabricate light-driven liquid crystal elastomer (LCE) actuators is an effective approach. Gold nanorods (GNRs) are considered as one of the ideal materials for preparing light-driven LCE actuators due to their outstanding photothermal conversion capabilities induced by localized surface plasmon resonance. However, the poor miscibility of pristine GNRs with liquid crystals has limited the performance of the actuators. Here, we report the organic molecule-mediated formation of GNR-dopamine hybrids, which enables a polydopamine (PDA) layer on the surface of GNRs. PDA coating not only serves as a robust polymeric surfactant for the underlying GNRs but also exhibits a broadband absorption, resulting in enhanced photothermal effect. Our results show that the PDA-coated GNRs (G-P) exhibit superior photothermal performance compared with the pristine GNRs. Under the irradiation of 880 nm near-infrared (NIR) light with intensity of 0.8 W cm(-2), the G-P-doped composite LCE film can achieve contraction to lift an object of 0.2 g to a height of 2 mm in 2 s, which is twice as fast as the time required for pristine GNR-doped LCE. Furthermore, we have demonstrated a light-driven LCE actuator based on a bilayer membrane by combining the G-P-doped composite LCE film with a polypropylene film. The LCE actuator can be bent rapidly under the NIR light illumination. This PDA-enabled strategy affords a rational design for fast-responsive light-driven LCE actuators and provides more opportunities for other types of light-stimulated responsive devices based on the photothermal effect.