MEMS-based air turbine with radial-inflow type journal bearing

A microelectromechanical-systems (MEMS)-based air turbine with a new bearing system was designed, fabricated, and evaluated. The bearing system uses a radial-inflow type journal bearing and a single-sided hydroinertia thrust bearing. To fabricate the radial-inflow type journal bearing, cavity-through deep reactive ion etching (DRIE) in conjunction with silicon-to-silicon direct bonding was used. Two etched silicon substrates were directly bonded, and then the bonded silicon substrates were etched by DRIE through the inside cavities. A maximum rotation speed of 95 000 rpm was achieved. The measured and calculated frequency responses of the rotor-bearing system suggest that the maximum rotation speed was probably limited by the pitching mode resonance.