Silicon ultrasonic horn actuated microprobes based self-calibrating viscosity sensor

We report on a microfabricated silicon ultrasonic horn-driven microprobes with polysilicon strain-gauges and integrated Pt-based immersion depth sensors for fluid viscosity measurement. Non-linear flexural vibration induced in the microprobes by the silicon horn actuated at its longitudinal resonance, is monitored and its damping is used to estimate fluid viscosity. Vibration damping in ethylene glycol solutions of varying viscosities are quantified and modeled, and high sensitivity (~0.13mV/mPa.s) is demonstrated in the normal blood viscosity range. Whole blood coagulation in a ~5¿l sample is measured by monitoring the frequency of the flexural vibration, demonstrating its applicability as a real-time blood viscosity sensor.