Reprogrammable magnetization pattern and shape morphing of phase-change magnetic soft composites

Magnetic soft composites with programmable magnetization patterns are highly desirable for diverse applications due to their multimodal magnetic response and locomotion. Despite substantial progress achieved in magnetic programming approaches, reprogrammable magnetization using low magnetic fields is still in development and challenging. Here, we report a one-step multi-direction magnetic reorientation strategy capable of reprogramming magnetization patterns in soft composites consisting of an elastomer matrix and magnetized ferromagnetic microparticles encapsulated by a phase-change polymer. Our approach is first based on the overall heating of these soft composites to achieve polymer phase transition, and then use magnet arrays to locally regulate the magnetic field distribution to achieve magnetic reorientation and programmable magnetization. Importantly, this approach allows us to reconstruct the desired magnetization patterns by reheating and redesigning the applied magnetic field. Using this approach, we numerically and experimentally demonstrate that multimodal magnetization and deformation patterns of millimeter-level strip-shaped and multi-arm phase-change soft composites can be achieved without changing the composite structure and the externally applied magnetic field. Furthermore, we demonstrate its functional applications in developing a multistate circuit switching, as well as a flexible magnetic recording that can present a variety of information such as numbers, letters, and face-based patterns.