Breaking one into three: Surface-tension-driven droplet breakup in T-junctions

We report a novel droplet breakup regime in the microfluidics T-junction, where new droplet interfaces are created in the two arm channels, rather than at the center of the junction. We show that there is a different hydrodynamic root for this new regime, and propose a simple geometric rule which enables this regime compared to the classical T-junction. A dynamic model for lower capillary number (Ca) is developed to predict the breakup process. We also show that at higher Ca the classical regime of central breakup is recovered in the same T-junction.