Viscosity and density values from excitation level response of piezoelectric-excited cantilever sensors

In this paper, we show for the first time that excitation level of piezoelectric-excited millimeter-sized cantilever (PEMC) sensors can be used as an experimental variable for determining both density and viscosity of liquids. PEMC of dimensions 3.8 mm × 2.6 mm × 0.287 mm were fabricated, characterized, and used to determine the densities and viscous damping coefficients of water, 5%, 10%, 15%, and 20% glycerol solutions by resonant frequency responses at applied voltages ranging from 0.01 V to 1 V. The second mode resonant frequency (38.52 kHz in air, 39.02 kHz in vacuum) was used. The resonant frequency decreased with increasing glycerol concentration and applied excitation voltages. The density of the solutions was determined from decrease in resonance frequency and was in good agreement with previously published theory. Dissipative losses due to liquid viscosity were observed in the broadening of the resonant peaks and were characterized by peak shape factor (Q-value). The viscous damping coefficients determined from the Q-values were used in calculating viscosity. A calibration curve for viscosity determination showed good accuracy of viscosity up to 30% glycerol.