Magnetically bistable actuator: Part 2. Fabrication and performance

Abstract

A bistable magnetic MEMS actuator was fabricated using microelectronic processes including a two-substrate flip-chip assembly, multilevel metallization, and sublimation release to avoid stiction. The actuator was found to have excellent correspondence between observed and modeled behavior. The benefits of shape anisotropy are quantified. Lithographic patterning of the magnetic material into long narrow strips along the actuator's length resulted in much greater magnetic torques being developed at reduced external field levels. Low levels of anisotropy led to designs with low levels of magnetization and therefore required higher external magnetic fields, whereas high levels of anisotropy led to designs latching at 10 mT levels with contact forces greater than 5 μN with switching energies less than 100 μJ and a switching speed of less than 5 ms. More moderate levels of anisotropy resulted in a design space where <1 μJ switching energies could be realized. Electrical performance has been demonstrated over 2 million cycles, and mechanical performance to 150 million cycles. Applications include electronics, microfluidics, and cryogenic devices.