Demonstration of a Microfabricated High-Speed Turbine Supported on Gas Bearings

A single-crystal silicon air turbine supported on gas lubricated bearings has been operated in a controlled and sustained manner at rotational speeds greater then 1 million rpm and power levels approaching 5 W. The device is a second-generation version of the microbearing rig first reported by Lin et al. (1), and is the first micromachine to operate at circumferential tip speeds of hundreds of meters per second, comparable to conventional scale turbomachinery. To achieve this level of peripheral speed, microfabricated rotors must withstand large induced stresses, need a sufficient power source to drive them, and require stable, low friction bearings for support. This paper focuses on process improvements in the microbearing device fabrication and on the advances in operating micro-gas bearings and micro- turbomachinery. The successful operation of this device motivates the use of this technology for high-power density MEMS.