P1I-7 Silicon Ultrasonic Horn Driven Microprobe Viscometer

We report on a microfabricated silicon microprobe (100mum times 140mum times 5mm) integrated with a silicon ultrasonic horn actuator, and piezoresistive strain gauges for viscosity measurement. The silicon horn is ultrasonically actuated at its lambda/2 longitudinal resonance by 2 PZTs bonded at its longitudinal mode node. The vibrational strain amplitude of the microprobe is quantified by the thin-film strain gauges for closed loop control. The microprobes were immersed in aqueous solutions of ethylene glycol (a Newtonian fluid) with varying bulk viscosities and from the amplitude of vibration measured by the strain gauge, we were able to quantify the damping in the fluid which is proportional to the viscosity. By varying the PZT actuation amplitude, the horn can vibrate longitudinally at a wide range of speeds. This could be used to quantify viscosity of non-Newtonian fluids such as blood, at different shear rates