Piezoelectric MEMS for audio signal transduction, microfluidic management, resonant mass sensing, and movable surface micromachined structures

This paper describes piezoelectric MEMS that offer competitive advantages over existing commercial technologies in audio, ultrasonic, air borne, microfluidic and RF applications. Specifically, a piezoelectric microphone requires a much simpler fabrication process than a condenser microphone, while a piezoelectric microspeaker is both planar and amenable to MEMS process for mass production unlike an electrodynamic speaker. Micromachined self-focusing acoustic transducers can eject picoliter liquid droplet in any oblique angle, without any clog-prone nozzle. Resonant mass sensors based on film bulk-acoustic resonators (FBAR) offer inherently higher sensitivity and smaller active area than a quartz microbalance. Piezoelectrically actuated cantilever can be moved in both directions (i.e., into and away-from a stationary electrode) unlike an electrostatically actuated cantilever, and provides a wide tuning ratio for a tunable capacitor.