Control of microfluidic separation processes governed by the Zweifach-Fung effect

This paper addresses several control problems for a prototypical microfluidic process designed for the separation operations of a fluid containing particles. The device is composed of one or several cascaded bifurcations that are traveled by the fluid. The volume fraction of particles in the flow is modified at each bifurcation. Fractionation is caused by the Zweifach-Fung effect, which governs the fluid dynamics in this device. It is a nonlinear effect that solely depends on the ratio of the flow rates in the branches. Propagation through the dead-volumes of the device and its capillary tubings generate input-varying delays of hydraulic type. These hydraulic delays strongly contribute to the complexity of the input-output dynamics to be controlled. The paper presents a model of the device and formulates some concise control problem statements for future research, along with illustrative simulation results. The case of single and dual bifurcation are presented.