Magnetic microactuators based on polymer magnets

Abstract

Integrated permanent magnet microactuators have been fabricated using micromachined polymer magnets. The hard magnetic material utilized is a polymer composite, consisting of magnetically hard ceramic ferrite powder imbedded in a commercial epoxy resin to a volume loading of 80%. The magnets have the form of thin disks approximately 4 mm in diameter and 90 μm in thickness. These disks have been magnetized in the thickness direction, and even in this geometrically unfavorable direction showed typical permanent magnet behavior with an intrinsic coercivity H ci of 4000 Oe (320 kA/m) and a residual induction B r of 600 Gauss (60 mT). Cantilever beam-type magnetic actuators carrying a screen-printed disk magnet on their free ends have been fabricated on an epoxy board. A planar coil on the opposite side of the substrate is used to drive the beams vertically. The actuators exhibit hard magnetic behavior allowing both attraction and repulsion by reversing the current direction. Static and dynamic testing of the magnetic actuators have been performed. The experimental data are compared with theoretical results obtained from both finite element simulations and analytical models. Good agreement is obtained between simulation and experiment. © 1999 IEEE.