Abstract
This paper describes a microfabrication process that accommodates the design considerations of wirelessly actuated magnetoelastic traveling wave and standing wave motors that are integrated with capacitive position sensors on a silicon substrate. The process—which incorporates AuIn eutectic bonding, multiple deep reactive ion etching steps, and metal electrode deposition and etching—addresses the challenges of magnetoelastic layer attachment, multi-layer structures, and robust electrode isolation. Measurements of successfully fabricated devices show that the typical resonant frequencies of the clockwise and counterclockwise modes for the standing wave stators existed at 12.1 and 22.4 kHz with 0.44 µm and 0.4 µm out-of-plane amplitudes, respectively, when a ≈2 Oe amplitude ac magnetic field and a ≈6.5 Oe dc magnetic bias field were applied. For the as-fabricated traveling wave motors, two desired mode shapes with π/2 spatial phase shift existed at typical frequencies of 28.4 and 29.9 kHz, with typical out-of-plane amplitudes of 74 and 70 nm, respectively, when a ≈6 Oe amplitude ac magnetic field and a ≈3 Oe dc magnetic bias field were applied. The frequencies were tuned with added mass, resulting in a shift to 28.37 and 28.33 kHz with out-of-plane amplitudes of 80 and 60 nm for the two modes, respectively. After tuning, a traveling wave with a continuous direction of propagation was successfully demonstrated. The capacitive position sensing scheme showed a sensitivity of ≈0.5 pF per degree over 8°.
Published Version
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