High Frequency Viscosity Sensing with FBARs

Film bulk acoustic resonators operating in thickness shear mode at a frequency of 720 MHz are used to characterize liquids with different viscosities. Their advantage over QCM devices are higher packaging density, CMOS-compatibility as well as lower production costs. Sensor response corresponds with theoretical models in the low viscosity regime but deviates strongly for higher viscosities. This behavior is analyzed as well as an assessment of the FBAR as a viscosity sensor is made