Piezoelectirc rotational mode disk resonators for liquid viscosity monitoring

Abstract

This work reports on piezoelectric rotational mode disk resonators capable of operation in liquid and their performance as viscosity sensors. Piezoelecrically transduced rotational mode silicon disk resonators with resonant frequencies in the 1.0-4.0MHz range were fabricated and operated in five different liquid alcohols (Methyl, Ethyl, Allyl, Isopropyl and Butyl). A quality factor of up to ∼54 was measured for such devices when immersed in liquid. It is shown through measurements that, as expected by fluid mechanics and vibrations theoretical analysis, both resonant frequency and quality factor of the resonators decrease as the viscosity of surrounding liquid increases. Frequency-viscosity sensitivity in the order of 40KHz/cP has been measured for such devices.