Stability of parallel flows in a microchannel after a T junction.

In this work, the flow of immiscible fluids in microchannels is studied. Flow pattern diagrams obtained in microfluidic chips are presented. Monodisperse droplets or parallel flows are obtained depending on the flow rate values of the aqueous phase and the oil phase. Transition from droplet regime to parallel flows cannot be described in terms of capillary numbers. Using confocal microscopy and high speed imaging, it was shown that droplets are formed through a blocking-pinching mechanism ruled by flow rate conservation. Conditions for parallel flow stability are quantified.