A three-lane microfluidic system, where the central fluid stream is confined between two outer streams is well suited for delivering solutes selectively to regions of samples located in the outlet channel. We present a model for the control of the interfaces where the position of the central stream in this microfluidic channel is manipulated by regulating pressure at the two outer inlets. To allow the use of reservoirs of arbitrary size, we decouple the pressure modulation mechanism from the reservoirs. The mechanism simultaneously modulates a variable fluidic resistance mechanically coupled to squeeze pump located in the fluid network between the reservoir and the channel. We show that the linearized dynamics of our nonlinear mechanism explains the high bandwidth in our system. We use the linearized model to design a linear controller and demonstrate its effectiveness for the full nonlinear dynamics in simulation. We present experimental results short-term and long-term pressure regulation at the channel inlets for stable control of laminar flow interfaces. We envision that this approach will be useful for flow cytometry, chemical synthesis, drug delivery, and investigation of spatiotemporally integrated biological responses at molecular, cellular, and tissue levels.

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