Low-Power Resonant Acceleration Switch for Unattended Sensor Wake-Up

Abstract

We have designed, built, and tested novel low-power (less than 10 nW) resonant acceleration switches. The switches respond to vibration at specifically designed frequencies between 30 and 1000 Hz by resonating with sufficient displacement to close an electrical contact and consume power only while vibration is occurring. A rotational design avoids switch closings from DC acceleration, and the quality factor, adjustable between 102 and 105 by tuning the vacuum level, sets the resonant detection threshold. The design includes electrostatic combs for selftest and frequency tuning (up to several Hz), compliant contacts to reduce squegging and contact damage, and ruthenium-coated contacts for improved reliability. Fabrication is accomplished with deep reactive ion etching at up to 50:1 aspect ratios, HF vapor release, and XeF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> frequency trimming (up to 30% of the as-fabricated frequency). Testing with vibration recordings played back through a shaker table demonstrates that the switches correctly identify a target without any false alarms.