In-Liquid Quality Factor Improvement for Film Bulk Acoustic Resonators by Integration of Microfluidic Channels

We demonstrate a significant improvement in the quality factor $(Q)$ of film bulk acoustic resonators (FBARs) in liquid environments via the integration of microfluidic channels. Our device consists of a longitudinal-mode excited zinc oxide (ZnO) FBAR and parylene-encapsulated microfluidic channels. Considerable enhancement in the $Q$ of the resonant system is obtained by confining the liquid in the microfluidic channels of thickness comparable to the acoustic wavelength. The improved FBAR achieves $Q$ values of up to 120, which represents an improvement of a factor of eight over those of current state-of-the-art devices.