Quality factor and vibration amplitude based viscosity measurements using suspended microchannel resonators

In this paper, we report precision viscosity measurements using suspended microchannel resonators (SMRs). Two different methods are developed and applied to glycerol-water binary mixtures having various weight ratios. First, open loop frequency sweep and harmonic oscillator fitting is employed to extract the quality factor (Q-factor) of an SMR. Second, closed loop feedback operation is employed while the vibration amplitude is continuously monitored. Both the Q-factor and vibration amplitude increase with increasing viscosity for the tested SMR and they agree well after rescaling. Viscosity measurements using the Q-factor change are compared with measurements using a bench-top tuning fork viscometer. While the bench-top tuning fork viscometer measures static viscosity thus always requires density correction, the SMR Q-factor measurement provides dynamic viscosity directly. In addition, SMR measurements require sample volume of ~50 μL while the bench-top viscometer requires ~10 mL per each measurement.