Micromachined polymer magnets

Micromachinable magnetic polymer composites have been prepared using commercial polyimide (Dupont PI-2555), and ferrite magnetic powders with different concentration levels (85-95 wt%). Magnetic, processability, and mechanical properties of these composites were measured. The B-H curve was measured using a vibrating sample magnetometer and showed typical permanent magnet behavior, with coercivity of 4000 Oe and residual induction approaching 3000 Gauss. In order to demonstrate the application of this material to micromachining, a simple permanent magnet microactuator has been fabricated. This actuator consists of a surface micromachined polyimide platform flexibly supported by tether arms. The composite material is deposited on the platform using screen printing. A 20 turn circular coil is integrated under the platform to complete the integrated microactuator. When driving the coil with 300 mA DC current, deflections of the platform in the range of +/-30 μm have been achieved. By reversing the direction of the current, both attraction and repulsion of the actuator occurred which confirms the permanent magnet character of the material