Nanoliter-droplet breakup in confined T-shaped junctions

Nanoliter-droplet breakup in either symmetrically or asymmetrically confined T-shaped junctions is experimentally studied. The critical condition with which nanoliter droplets will break equally is theoretically analyzed based on the pressure-driven mechanism. The scaling analysis is experimentally confirmed, implying that the droplet breakup in a confined T-shaped junction is a pressure-driven process when the capillary number is less than ~0.1. A semi-empirical correlation is obtained for predicting the equal breakup in symmetric T-shaped junctions. The critical condition is found to be dependent on the initial droplet length, channel depth and capillary number. Besides the equal breakup of nanoliter droplets, a new droplet breakup pattern, unequal breakup, is observed in the symmetric T-shaped junction. In asymmetric T-shaped junctions the nanoliter-droplet breakup is found to be very difficult.