A passive flow regulator with low threshold pressure for high-throughput inertial isolation of microbeads

In this work, we present a novel passive flow regulator fabricated by stacking five functional layers. To understand the flow-rate regulation characteristics, a series of prototype devices with different structural dimensions are investigated. The experimental results show that our regulator can exhibit a constant delivery flow rate of up to 4.38 +/- 0.1 ml min(-1) with variations less than 5%, and the minimum threshold pressure for achieving a constant flow rate is only 10 kPa. As compared with previously reported regulators, our regulator offers a much wider flow-rate regulation range under lower threshold pressures. To validate the practical function of our regulator, a low pressure gas-driven flow system integrated with two passive flow regulators and a Dean flow fractionation chip is constructed to achieve high-throughput inertial isolation of differently sized microbeads. The isolation performance is found to be totally independent of the inlet pressure, which permits the use of portable and low-cost flow-driving apparatus for accurate flow control. Therefore, the passive flow regulator proposed in our work is potentially useful for the steady injection and accurate control of the sample fluid in low cost, miniaturized microfluidic systems.