We reported a phenomenon that the magnetic field can make up a boundary to restrict motion of the aluminum powered liquid metal motor. For the droplet motors with diameter below 1 mm, such magnetic trap effect will be strong enough to bounce them off the boundary. We attributed the effect to the electromagnetic mechanism. Owing to the Lorentz force, the highmagnetic field will break up the directional running of the motor. The more aluminum added in the metal droplet, the stronger the trap effect. This phenomenon suggests an important way to control behavior of the liquid metal motors.

Applied Physics Letters, 2015

Liquid metal motor under magnetic trap. (a) Schematic for producing many Al-Ga-In motors in a Petri dish. (b) The number of motors along with time in the interior and boundary zone of magnet. (c) Sequential snapshots of tremendous Al-Ga-In motors' motion under magnetic field.