Magnetically-assisted digital light processing 4D printing of flexible anisotropic soft-Magnetic composites

Flexible anisotropic soft-magnetic composite (FASMC) presents superior magnetic properties in one or more specified directions, showing great potential in the application of microwave absorption, soft robots, and other smart sensors/actuators. However, the fabrication of FASMC using additive manufacturing is challenging due to a trade-off between magnetic properties of the composites enhanced by iron particles and printability during printing. Here, we developed a 4D printing scheme using flexible soft-magnetic photosensitive resin consisting of flexible long-chin acrylic resin monomer and soft magnetic iron particles. Multiple complex structures with good spatial resolution of ∼170 μm were fabricated using magnetic field-assisted digital light processing (MF-DLP). Directional magnetic field was applied during printing, enabling the fabrication of FASMC with strong anisotropic magnetic properties. FASMC with high CIP (carbonyl iron powder, CIP) concentration of up to 45 wt.% was fabricated with excellent tensile strength and elongation up to 460%. Strong anisotropic magnetic properties were demonstrated through a series of stimuli-response testing such as large deformation, anti-deflection, controlled motion, variable stiffness metamaterial, and array assembly, under external magnetic field. This study demonstrates the feasibility and potential of MF-DLP technique for fabrication of FASMC, shedding light on the design and fabrication of next-generation sensors and actuators.