Dynamic Characterization of Passive Flow-Rate Regulator Using Pressure-Dependent Autonomous Deflection of Parallel Membrane Valves

We performed a dynamic characterization of passive flow-rate regulators, which compensate for inlet pressure variation and maintain a constant flow rate for precise liquid control in microfluidic systems. To measure the flow rate for a short time, much less than the period of the dynamic inlet pressure, we use the particle image velocimetry (PIV) method. DI water containing fluorescent beads with a 0.7-mu m diameter was supplied to the flow-rate regulators, and two successive images of the particles were taken by a pulse laser and a fluorescent microscope to measure the flow velocity. For a dynamic inlet pressure of frequency 60 Hz, the flow velocity was constant with an average of 0.194 +/- 0.014 m/s as the inlet pressure varied between 20 kPa to 50 kPa. The flow-rate regulators provided a constant flow rate of 5.82+0.29 mu l/s in the frequency range of the inlet pressure from 1 Hz to 60 Hz.