The supporting capacity of ferrofluids bearing: From the liquid ring to droplet

In this paper, a simple ferrofluids (FFs) bearing, which consists of a rotor, a stator embedded with a cylinder magnet, and FFs is proposed. By controlling the volume of FFs, two types of liquid structures of the ring and droplet shapes are formed on the stator surface. Models of the bearing for the static supporting force are established and validated by experiments. The multicycle loading-unloading of the FFs bearings as well as the dynamic supporting force are performed. Results show that the static supporting force of the bearings can be predicted approximately by the theoretical model. Multicycle loading-unloading tests indicate that force values with excellent repeated accuracy can be achieved only within a limited range of oscillation in gap height. Compared with the FFs droplet bearing, the rotation speed manifests more significant impact on the dynamic supporting force of the ring structured bearing. Such design presents a new thought for micro-electro-mechanical system (MEMS) that requires precision supporting or frictionless bearing.