Magnetic induction micromachine-part II: fabrication and testing

This paper presents the realization of a magnetic induction machine. The development of this machine is part of an ongoing project to create high-power density electric microgenerators for use in portable-power applications. The results reported here focus on testing a first-generation nonlaminated electromagnetic actuator, a metrology device designed for exploring and characterizing the fabrication process and the operating behavior of the magnetic induction micromachine. Achieving high power density requires large electrical currents and magnetic fluxes, which necessitate thick, multilayered microstructures that are difficult to fabricate. The batch-fabrication schemes developed as part of this work are based on low-temperature micromolding that makes extensive use of various ultra-thick photoresists and electroplating of electrical conductors (Cu) and ferromagnetic materials (Ni-Fe 80%-20%), resulting in the successful fabrication of a multilayer two-phase planar stator and a planar rotor. To evaluate the performance of the complete machine (stator plus rotor), a 4-mm-diameter, 500-μm-thick electroplated Ni-Fe rotor is tethered to a series of flexible structures that prevent it from making a complete revolution, but allow accurate torque performance extraction. The tethered induction micromotor studied here exhibits torque production as high as 4.8 μN·m.