Recent advances in soft magnetic nanocomposites have enabled myriads of magnetic
robots with programmable shape transformation, shedding light on various biomedical
applications. However, the complex shape transformation of magnetic hydrogels remains a
challenge because of their ultralow magnetization and simple geometry. Here we
demonstrate an approach to meet this challenge by fabricating composite structures of
magnetic hydrogels and elastomers with extrusion-based 3D printing. Under an alternating …