Fig. 1: The different modes of droplet breakup at the double T junction.

Upon decreasing the flow rate of the dispersed phase, Q_w, the droplet generation mode changes from the (a, b) out-of-phase synchronization mode to the (c, d) transition mode, and then to the (e, f) in-phase synchronization mode, under the condition of a fixed continuous-phase flow rate, Q_o. Snapshots of movies recorded from a microscope are shown with a given time interval (a, c, e). The plots show how the scaled volume V^* of the dispersed phase from each branch changes according to the time (b, d, f); the volume is scaled by the volume of the junction w_cw_dh, where w_c, w_d, h are the widths of the main channel and branch, and the height of the channel, respectively. The time-varying V^* from two branches exactly overlap in (f). All scale bars indicate 200 μm.