Superhydrophobic light-driven actuator based on self-densified wood film with a sandwich-like structure

Response actuators based on different stimuli such as light, humidity and temperature have attracted extensive attention due to their advantages in various environments. In this work, a facile top-down strategy is proposed to prepare a light stimuli-responsive self-densified wood film. We constructed a sandwich-like structure by in-situ co-precipitation of Fe3O4, spraying CNT, self-densification and chemical vapor deposition methyltrimethoxysilane (MTMS) on TEMPO-oxidized delignified wood. The CNT/Fe3O4/MTMS wood film exhibits excellent strength (56 Mpa along the fiber direction), superhydrophobicity (water contact angle of 151°) and photothermal conversion performance. The Fe3O4 in the film plays a good role of photothermal conversion, which makes the photothermal conversion effect of the film double that of the wood film sprayed only with CNT. Under near-infrared (NIR) light irradiation and focused sunlight, the film exhibits a light-driven response of linear motion on the water surface. Based on the excellent electrical conductivity and light stimulus responsiveness of the film under NIR irradiation, an electrical switch is successfully designed and can be remotely controlled. Moreover, the film is easy to recycle due to magnetism, it is also very stable under moisture environment due to the protection of the superhydrophobic coating and the dense structure created by self-densification.