Robust and Fast‐Transforming Soft Microrobots Driven by Low Magnetic Field

Magnetically driven soft microrobots, characterized by their small size, soft structure, and responsiveness to magnetic fields, offer unique advantages such as high maneuverability, biocompatibility, and remote control, making them suitable for a variety of applications across multiple fields. Achieving low-power actuation for microrobots is more accessible, safer, and cost-effective, dependent on the precise quality and arrangement of their magnetic domains. However, traditional approaches integrating multi-domain magnetic microstructures often introduce trade-offs between mechanical stability and responsiveness. Here, a magnetic domain assembly method is presented for the fabrication of robust soft microrobots with fast transforming behaviors powered by low magnetic fields (3-15 mT). By developing a composite ink containing polyacrylamide chains grafted onto magnetizable single-domain ferromagnetic NdFeB nanostructures, precise control over domain orientation within ultrafine filaments (80 µm) is achieved by magnetic field-assisted 3D printing process, allowing complex and rapid shape morphing in under 1 s, even with less than 2 wt.% NdFeB. This uniform magnetic alignment results in a tenfold increase in mechanical toughness and impressive stretchability (1600%). With top-performing actuation performance at low magnetic fields, the microrobots demonstrate multimodal locomotion and robust tasking capabilities, showcasing their transformative potential for next-generation soft robotics.