Bioinspired superhydrophobic light-driven actuators via in situ growth of copper sulfide nanoparticle on cellulose nanofiber

Among stimuli-responsive actuators, light-driven hydroplaning actuators have attracted significant attention because of their controllable and contactless nature. However, manufacturing actuators with rapid dynamic responses to a single stimulus remains challenging. Herein, inspired by rove beetles and water striders, we developed superhydrophobic light-driven actuators based on the in situ growth of copper sulfide on cellulose nanofiber and subsequent modification with octadecyltrimethoxysilane. The actuators exhibited excellent superhydrophobicity (water contact angle of 160.6 degrees) and the water contact angle was maintained above 150 degrees under various harsh conditions (acid/base immersion, ultraviolet irradiation, heat treatment, and sandpaper abrasion). Under near-infrared (NIR) irradiation (808 nm, 1.4 W cm-2), excellent photothermal performance was achieved, with a photothermal-induced temperature change of 81.0 degrees C. Based on the mechanisms of superhydrophobicity, the Marangoni effect, and vapor jet flow, the light-driven actuators exhibited a rapid dynamic response (response time of 0.5 +/- 0.2 s), ensuring fast linear motion (velocity of 8.7 +/- 0.7 mm s-1) and flexible rotation (angular speed of 2.4 rad s-1) under NIR irradiation. Moreover, complex motions such as S-shaped, triangular, and circular motions were achieved by combining linear motion and rotation, which could facilitate obstacle avoidance, smart transportation, and contactless delivery.