A micro electromagnetic actuator with high force density

Abstract In this paper, we propose a planar type micro electromagnetic actuator with high force density. The actuator is composed of a mover (8 mm*8 mm*0.5 mm) and a stator (14mm*10mm*0.2 mm). As the mover, a thick NdFeB permanent magnet film (300 μm) with a chessboard pattern (unit size is 0.8 mm*0.8 mm) is attached with a ferromagnetic back yoke to provide enhanced magnetic flux density. In the stator, 3D mesh type micro coil with multi-turn configuration is designed accordingly. The micro coil has a novel connection between adjacent mesh units, which enables easy fabrication. The thick film magnet with chessboard pattern as well as the multi-turn micro coil with novel connection constitute the originality of this actuator. The mover and the stator can be produced by batch fabrication. The magnetic flux density (B) generated by the magnet are simulated and experimentally measured. The magnitude of B at vertical direction attains around 40 m T at 770 μm plane above the surface. Due to delicate design, the MEMS-based micro coil can withstand as high as 0.4A constant current input for over 60 min on a thermal isolated ceramic plate. The long-time duration experiment testifies the practicality of this micro actuator. Both repulsive and attractive electromagnetic force can be generated on the mover by altering the current direction in the stator. The measured force is around 4.3 mN at 20 μm gap with 0.1A stable current input in the stator and the force density attains as high as 0.96 mN/A/mm3.