Migration and sorting of droplets at fluid-fluid interface

Migration of droplets across a flat fluid-fluid interface formed between two immiscible coflowing oils (primary continuous phase CP1 and secondary continuous phase CP2) at low Re is studied. The droplets in CP1 are subjected to lift-induced migration toward the zone of zero shear stress, which occurs in the CP2 and thus come in contact with the interface. The interplay between the competing lift (Fl) and interfacial tension (Fi) forces decides the interfacial migration of droplets. Based on the physical understanding, we demonstrate passive sorting of droplets based on droplet size and viscosity.