Soft magnetic wood composites with chain-aligned Fe3O4 nanoparticles for magnetically driven actuators

Abstract

Intelligently responsive wood-derived materials have long been sought due to their sustainability, earth abundance, and low carbon footprint, with promising applications in sensors, flexible electronics, and soft robotics. However, insensitive responsiveness and unsatisfactory mechanical properties have hindered the development of intelligent drive systems. This work reports on soft magnetic wood composite (SMWC) with a sandwich structure consisting of densified wood and polydimethylsiloxane (PDMS) mixed with Fe3O4. We treat natural wood chemically to improve flexibility, especially the lignin partial removal while keeping the wood structure intact. Benefiting from densification and magnetic-assisted techniques, multilayer SMWC with chain-arranged Fe3O4 can be prepared, which exhibits 183.5 MPa mechanical strength along the longitudinal direction, flexible bending capacity, a water contact angle of 100.9° and a saturation magnetization strength of 9.81 emu g−1 for 40 wt% Fe3O4. Importantly, the chain arrangement of Fe3O4 facilitates the sensitive control of SMWC compared to non-chain arranged structures. We have designed a star-shaped actuator that demonstrates controlled magnetic response, which can perform transporting cargo through linear and rotational movements on the water. SMWC with chain-aligned Fe3O4 exhibits good flexibility, excellent mechanical properties, and superior magnetic responsiveness, which is essential for exploring the responsiveness of wireless sensors and soft robots.