A Micromachined Doubly-Clamped Beam Rheometer for the Measurement of Viscosity and Concentration of Silicon-Dioxide-in-Water Suspensions

In this contribution we demonstrate the feasibility of a sensor system for viscosity and concentration measurement of complex liquids, in particular suspensions of silicon dioxide particles in water. The sensor system is based on a doubly clamped micromachined beam vibrating in the sample liquid, and an optical readout utilizing a DVD player pickup head. The vibrating beam features resonance frequencies in the range of several 10 kHz, and higher mechanical amplitudes than microacoustic sensors, e.g., quartz thickness shear mode (TSM) resonators or surface acoustic wave (SAW) devices. We show that the damping of the beam is dominated by the viscosity of the liquid, and that this relation also holds for the considered complex liquids, whereas a TSM resonator sensor fails to detect the steady state shear viscosity of the suspensions.