Droplet robots have attracted much attention in recent years due to their large-scale deformability and flexible mobility in confined spaces. However, droplet robots are always difficult to maintain rigid shapes, making them difficult to manipulate objects with large inertia. Moreover, their low conductivity makes them unable to complete tasks such as circuit repair. Herein, a millirobot made from magnetorheological liquid metal is proposed to address the problems. Specifically, the magnetorheological liquid metal (MLM) robot is made by engulfing iron particles into gallium-indium alloy, and the mass fraction of the MLM robot is determined by microscopic observation and rheological test. The MLM robot possesses both solid and liquid properties, enabling the robot with plasticity, large-scale deformability, good conductivity, motion flexibility, and good object manipulation. The MLM robot can achieve almost all of the functions of existing droplet robots, including splitting, merging, navigating in narrow channels, and pushing objects. In addition, it can also accomplish some other tasks that are difficult for existing droplet robots, such as pulling large objects, repairing damaged circuits selectively and reversibly, and repairing suspended circuits through plasticity. The demos show that MLM robots can traverse narrow spaces and repair circuit damage selectively and reversibly. It is believed that MLM robots can enrich diverse functionalities in the future.
Keywords: liquid metal; liquid wire; magnetic control; magnetorheological fluid; millirobot; phase transformation.