Room temperature, open-loop levitation of microdevices using diamagnetic materials

The use of diamagnetic levitation for micromechanical bearings is discussed. The simple system of a magnetic sphere supported by a diamagnetic material has an analytic solution for the vertical force; this solution is used to illustrate the fundamental properties of diamagnetic levitation. Work by previous researchers to diamagnetically levitate magnets with masses as large as tens of grams using external fields, as well as micrometer-scale levitation of diamagnetic materials, is discussed. Calculations presented suggest modern magnets on the order of 100 to 300 mu m will self-levitate over diamagnetic materials without supporting external fields. This suggests a number of noncontact micromechanical bearing applications, such as for microrobotics and highly sensitive sensors. Diamagnetic bearing are typically limited to light-load applications. To alleviate this limitation, a noncontact, hybrid diamagnetic air bearing is proposed for light-load/low-speed to high-load high-speed use without the start-up problems normally associated with self-pumping air bearings. A preliminary analysis of the hybrid bearing concept suggests that squeeze film effects may allow virtually the full drive load to be applied at start-up, provided lateral acceleration is high.<>