Ferrofluid-assisted levitation mechanism for micromotor applications

This paper reports a highly simple and robust levitation method realized by ferrofluid for micromotor applications. A layer of ferrofluid is self-sustained on a permanent magnet to serve as liquid bearing that lifts the magnet up on the substrate, enabling low-friction movements of the magnet. A levitation height of ~500 μm is observed with a 1.6-mm-sized NdFeB magnet. The levitated magnet is electromagnetically driven by microfabricated planar coils to demonstrate a linear micromotor. The dynamic responses of the magnet slider are characterized to show its acceleration level of ~1 m/s2. The actuation force of 388 μN or greater is obtained. Using an array of the planar coils as the rail track, continuous actuations of the slider is achieved with the maximum velocity of 19 mm/s.