Design of control systems for two-phase microfluidic processes

In this work a study for the design of an active control system for two-phase microfluidic processes based on the manipulation of the input flow rates is presented. A wide experimental campaign was performed using two chips with different geometries. The approach proposed takes the advantage of the optical monitoring and the on-line signal processing. Starting from the optical process monitoring, an analysis procedure for the flow characterization (referred as soft sensor), was developed and a control parameter (named delta) identified. Using this parameter it was possible both a classification of two flow regimes in slow and fast dynamics, and a detailed characterization of flow features as, an air/water slug shortened in slow patterns, and a reduction of the slugs inter-distance and an increase of their frequency in fast patterns. Then the control system design was defined and the open loop and closed loop control laws established considering two possible control actions: a jump from one flow regime to the another or a tuning of the input flow to have a desired slugs length or frequency.