Pure Liquid Metal Phase‐Transition Robot With Multimodal Motion Actuated by a High‐Frequency Magnetic Field

ABSTRACT Magnetic liquid metal robots suffer from inherent trade‐offs: magnetic particle doping for actuation degrades material homogeneity and triggers corrosion, while conventional dual‐field systems substantially increase system complexity. Here, we report a pure liquid metal (BiInSn, ∼62°C melting point) phase‐transition robot (LMPT robot) actuated solely by a 500 kHz high‐frequency magnetic field (HFMF). Under HFMF actuation, induced eddy currents within the robot generate Joule heating for rapid, reversible solid–liquid phase transitions while simultaneously producing Lorentz forces for its untethered cross‐phase multimodal motion (including vertical propulsion, dynamic levitation, oscillatory deformation, and directional translation), thereby eliminating magnetic dopants and auxiliary temperature control. The LMPT robot exhibits enhanced environmental stability and competitive mechanical/fluidic performance relative to representative magnetic particle‐doped LM robots under the tested conditions, featuring a six‐order‐of‐magnitude reversible stiffness switch (4.4 GPa solid to 4.7 kPa liquid). It achieves adaptive navigation in unstructured environments, acts as a wireless mobile heat source for on‐demand material/circuit damage and repair, and functions as reconfigurable microfluidic components (pumps, valves, reaction accelerators). This work establishes a robust paradigm for multifunctional liquid metal robotics, enabling promising applications in reconfigurable electronics, soft robotics, microfluidic systems, and beyond.