Interaction of a Droplet with T-junction of a Microfluidic Bypass Channel

The transition from no droplet breakup to droplet breakup in a bypass channel of a parallel microfluidic system is studied using experiments and 3D numerical simulations. In experimental work, PDMS microchannels are fabricated using standard photolithography, and the high-speed camera is used to record droplet interaction with the bypass channel. 3D numerical simulations are carried out for conditions causing both droplet breakup and non-breakup. The droplet is generated upstream, using standard T Junction geometry. The generated droplet is then made to interact with the bypass channel. The first aspect of our study is a detailed experimental investigation of the transition process by varying width of the bypass channel (w_b) and the capillary number (Ca). There exists a critical value of Ca at a constant value of w_b and a critical value of w_b at constant Ca, at which droplet breakup occurs. Combining numerical and experimental results, we found out that droplet breakup at the entrance to the bypass channel can exhibit squeezing and dripping regimes which are equivalent to those occurring in droplet generation at a T-junction.