Design, modeling, and testing of high performance RF bistable magnetic actuators

In this work, electrostatic and magnetic actuation mechanisms were investigated for providing continuous and discrete control of MEMS components. The project goal was to design and fabricate high performance RF compatible switch and tuning elements for use in a cryogenic filter system.; Due to the limitations of electrostatic RF actuators, magnetic actuation was also investigated, and the optimal design space for a bistable magnetic actuator with ultra-low actuation energy and large actuation distance (100 mum) has been modeled. Attention was paid to minimizing the energy expended to minimize heat dissipation and power consumption so that the device could be used over a wide temperature range, including cryogenic environments. A more desirable switching regime existing for low magnetic fields (10 mT) was found that requires shorter pulses (mus vs ms) and lower actuation energy (<5 muJ vs 100 muJ) than designs outside of this space. The device was modeled to latch in two states, based on the interaction of the magnetic actuator with an external magnetic field.; Based on this model, 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 greater magnetic torques developed at reduced external field levels. Low levels of anisotropy led to designs with low levels of magnetization and required higher external magnetic fields, whereas high levels of anisotropy led to designs latching at 10 mT levels with contact forces greater than 15 muN, switching energies less than 100 muJ, and a switching speed faster than 5 ms. More moderate levels of anisotropy resulted in a design space where <1 muJ 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.