Bulk modulus measurement of microfluidics by longitudinal bulk acoustic wave sensors

Abstract

In this paper, we measured bulk modulus of microfluidics using bulk acoustic wave (BAW) MEMS sensors. The 2.5 GHz resonant sensor interacted with fluids by longitudinal bulk acoustic waves. Measurement experiments were carried out on 1 pL glycerol-water sample droplets, and the results were compared with theoretical models. We showed that the longitudinal acoustic wave sensors are sensitive to bulk modulus of microfluidics (sensitivity of 12.42 MHzm2N−1). We also validated that the sensors are insensitive to viscosity, which is another important liquid property usually measured by shear acoustic wave sensors.