Magnetic sheet-shaped hydrogel robots with multiple motion modes and assembly behavior

Magnetically actuated microrobots have shown promising applications in the biomedical field due to their wireless manipulation, high precision, and ability to perform tasks in narrow environments. However, the limitations in obstacle-crossing capabilities, single-mode locomotion, and biocompatibility of microrobots remain key challenges in current research. Here, a biodegradable magnetic sheet-shaped hydrogel robot (MSHR) was developed using a straightforward extrusion process. The MSHR demonstrates four distinct and stable motion modes: tumbling, rolling, spinning, and walking, with the capability for flexible conversion between these motion modes. The MSHR's multimodal motion endows it with excellent environmental adaptability, allowing it to stably locomote in complex scenarios. Further investigations reveal that magnetic dipole forces can induce the assembly of MSHRs into stable dimeric structures, and the dimer of MSHRs exhibits improved motion performance and obstacle-crossing abilities when compared with the individual MSHR. Additionally, a vision-guided motion control strategy was adopted to actuate the individual and dimeric MSHRs to track the predefined paths. The MSHR proposed in this study demonstrates multimodal locomotion capabilities, stable collective behaviors, and precise motion control, offering innovative solutions and technological support for biomedical applications such as targeted drug delivery and minimally invasive surgery.