The interface between adjacent laminar flow streams in the output channel of a Y-shaped confluent microfluidic network is useful for investigating the response of individual living cells to steep chemical gradients. This paper reports the design and performance of an automated pressure-feedback system for accurately and rapidly changing the position of that interface. The device will be employed to investigate the dynamic response of cells to time-varying chemical stimulation. The system works by controlling the pressure difference between the two adjoining inputs of the microfluidic network, altering the relative flow rate of the laminar streams in the output microchannel. Continuity of incompressible fluids dictates that the plane of the interface between the two streams will move from side to side as the flow rates change. The sample-data control system samples a temperature-compensated monolithic piezoresistive pressure sensor at 1 kilohertz, allowing the control of high-bandwidth microfluidic systems. This automated system enables long-duration, high-precision experiments that involve time-varying parameters to be performed simply, rapidly, and inexpensively.

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