Design, Fabrication and Testing of a Millimeter-Level Magnetically Suspended Micromotor

A magnetically suspended micromotor with 5 mm stator diameter and 1.5 mm rotor diameter, 0.1 mm air gap and 0.5 mm thickness has been built and tested. The stator and rotor are made by the UD LIGA process to achieve high dimensional accuracy. The micromotor is actively controlled using a four-quadrant photodiode to measure radial displacement. The system with UD LIGA rotor is successfully spun up to 600 rpm. A micro inductive sensor is proposed to integrate into the micromotor in the future. The micro inductive sensor designed for the first micromotor prototype has eight 15-turn single-layer coils with 10 µm line width, 10 µm line space and 6 µm thickness. The coils are fabricated using thick photoresist lithography and electroplating process. The sensor has a sensitivity of 44 mV/µm and error of 1.2 µm within 400 µm range.