A micromechanical flow sensor for microfluidic applications

We fabricated a microfluidic flow meter and measured its response to fluid flow in a microfluidic channel. The flow meter consisted of a micromechanical plate, coupled to a laser deflection system to measure the deflection of the plate during fluid flow. The 100 μm square plate was clamped on three sides and elevated 3 μm above the bottom surface of the channel. The response of the flow meter was measured for flow rates, ranging from 2.1 to 41.7 μL/min. Several fluids, with dynamic viscosities ranging from 0.8 to 4.5×10^-3 N/m, were flowed through the channels. Flow was established in the microfluidic channel by means of a syringe pump, and the angular deflection of the plate monitored. The response of the plate to flow of a fluid with a viscosity of 4.5×10^-3 N/m was linear for all flow rates, while the plate responded linearly to flow rates less than 4.2 μL/min of solutions with lower dynamic viscosities. The sensitivity of the deflection of the plate to fluid flow was 12.5±0.2 μrad/(μL/min), for a fluid with a viscosity of 4.5×10^-3 N/m. The encapsulated plate provided local flow information along the length of a microfluidic channel.