Droplet breakup in a parallel microchannel with asymmetrical geometric constraints

Abstract

Here we demonstrate the influence of downstream geometric constraints on droplet breakup and subsequent distribution dynamics in a microdevice containing constricted and parallel microchannels. The microfluidic configuration consists of a sequential connection of T-junction, branching-junction, and two parallel arms with different converging-straight-diverging (CSD) sections at the downstream. Geometric asymmetry was incorporated by only varying the CSD section in terms of converging-diverging angle, throat-width, and throat-length. We observed two distinct breakup regimes, namely obstructed and tunnel for all three microdevices. We found the degree of breakup asymmetry resulting from downstream feedback to increase with increasing continuous phase Reynolds number and dispersed phase capillary number. Our results show that the droplet split asymmetry and the influence of geometric constraints are more discerning for tunnel regime than the obstructed breakup. It highlights the significance of downstream feedback in a constricted and parallel microchannel network.