Sensing Viscosity and Density with a Micromachined Suspended Plate Resonator

Abstract

We present a novel micromachined sensor for the viscosity of liquids. The sensor operates at frequencies in the kHz range and consequently its measured values are better comparable to conventional laboratory equipment as those of microacoustic sensors vibrating at several MHz. The sensor utilizes Lorentz force excitation and piezoresistive readout. The first mode of vibration is an in-plane mode with low damping, whereas the overall mass is high. The sensor design is intended to achieve higher quality factors than, e.g., clamped-clamped beams.For the interpretation of the measurement results we take a simple phenomenological model that allows the simultaneous measurement of both viscosity and mass density of liquids.