An integrated electromagnetic micro-turbo-generator supported on encapsulated microball bearings

The development and characterization of the first integrated electromagnetic micro-turbo-generator supported on encapsulated microball bearings are reported. The device presents a novel integration of encapsulated microballs that provide a simple operation and actuation scheme, a silicon microturbine rotor with thick magnetic components for high magnetic flux density, and wafer-thick copper coils for optimum magnetic flux linkage and low coil resistance. Spin-down testing of the microturbine demonstrated dynamic friction torques of up to 33 μNm at the rotational speed of 16 krpm, corresponding to 6% turbine efficiency. A maximum perphase AC open circuit voltage of 0.1 V and power of 5.6 μW on a 220 Ω resistive load were measured; in full-agreement with theoretical estimations.