Characterization of rotary magnetic micromotor supported on single droplet

Micromotors are key devices for various micromanipulation systems for potential scientific and industrial applications. In this study, a magnetic micromotor consisting of an 800 μm-diameter plate supported by a single droplet on a hydrophobic substrate is constructed. It is actuated by external uniform magnetic fields generated by three-dimensional electromagnetic coils. Due to the submillimeter-scale size of the top plate, the capillary force from the droplet makes it capable of working in horizontal and tilting orientations. The single droplet, also called liquid bearing, lubricates the micromotor well and improves its flexible workability. The micromotor can rotate at a speed of more than 1000 rpm in a rotating magnetic field. Besides, step motion with a stepping angle of less than 4 can be easily achieved. It is found that reducing the thickness of the liquid bearing could promote the stiffness and anti-interference capability of the micromotor. Due to its simple structure, the micromotor can be easily further miniaturized. The microscale size and flexible working performance make it suitable for wide micropositioning and micromanipulation tasks.