The multimodal motion along a solid-liquid interface of a soft microrobot driven by compound magnetic fields

In recent years, soft microrobots based on flexible materials have received increasing attention. Most of the current studies on soft microrobots have implemented only one motion mode, and because the motion environment is often set inside liquid, the strategies of multimodal motion control near the solid-liquid interface are insufficient. In this study, we present a 4 mm x 1 mm x 0.2 mm sheet-like soft microrobot bent into a ring shape and magnetized so that it can move in multiple modes along the solid-liquid interface and can be driven by different types of magnetic fields. The deformation amplitude and the total magnetic moment of the robot under the external magnetic field were obtained with the help of finite element simulations. Three different periodic magnetic field driving modes along the solid-liquid interface, namely rolling mode, walking mode, and hopping mode, were realized, and the robot's motion speed and direction under various motion modes were adjusted by additional magnetic field strengths and magnetic field gradients. This research can enhance the adaptability of soft microrobots to various motion environments and further expand their application prospects.