Electromagnetic rotation of a liquid metal sphere or pool within a solution

A liquid metal electric motor including a pair of concentric ring electrodes, permanent magnet and electrolyte solution is demonstrated. A liquid metal galinstan sphere, along with a NaOH solution, is stimulated to rotate centrifugally around the central electrode and the rotating speed increases with the voltage. The NaOH solution serves to rapidly remove the oxide on the liquid metal surface, reduce the motion friction and provide impetus to the liquid metal. As the mass of the liquid metal is increased to 12.16 g to form a kidney-like body, its rotating speed appears more controllable and the effect of the electrolytic action in the NaOH solution becomes weak in the range of 0-1.82 V. As the mass of the liquid metal is increased to 18.20 g to form a circular ring-shaped body, the ideal voltage range for controlling the rotating motion of the liquid metal is 0-0.81 V. The metal fluid rotates at a speed of 1.9 r.p.m., even at an extremely low voltage of 0.03 V. The liquid metal electric motor established here can find important applications in chip cooling, liquid metal pumps, material mixing, soft machine realization, etc.