Analytical and experimental study of micromachined graphite rotor based on diamagnetic levitation

A levitation system, which is composed of a highly oriented pyrolytic graphite (HOPG) rotor and NdFeB permanent magnets, is proposed in this paper. The diamagnetic force between the HOPG rotor and the NdFeB magnets contributes to between the HOPG rotor and the NdFeB magnets contributes to the levitation and friction-free rotation of the rotor. The rotor is first designed as a disc with four blades. Force analysis and levitation characteristics are carried out in finite element software COMSOL™. The highly oriented pyrolytic graphite (HOPG) rotor was successfully fabricated with μEDM (micro-electro-discharge machining) system. A laser displacement sensor and a mass flow controller are used to characterize the levitation height and rotation speed of the rotor. The levitation height of 130 □m observed with the rotor matches well with the simulation result. The revolution of the rotor is demonstrated by applying gas flow, showing stable, continuous actuation with the maximum rate of 500 rpm. These promising results suggest potential applications of the mechanism toward frictionless microsensors and micromotors.