Dynamics of bubble breakup in a microfluidic Y-bifurcation

A highspeed camera was used to investigate experimentally the bubble breakup and dynamics in a symmetric microfluidic Y-junction divergence. N2 and deionized water with 0.3% surfactant sodium dodecyl sulfate (SDS)-glycerol were adopted as dispersed and continuous phases, respectively. The symmetric breaking with permanent obstruction, symmetric breaking with gaps and non-breaking regimes were observed in experiments. Experimental results showed that: whether bubbles breakup or not depends primarily on both bubble initial lengths and capillary number. And the higher the viscosity of the fluid is, the higher is the capillary number needed to break bubbles. Dynamics of bubbles breakup were investigated under different regimes. The breakup with permanent obstruction included two stages: squeezing stage and rapid breakup stage. In squeezing stage, the breakup process was only controlled by the augmented pressure. The rapid breakup stage was affected by surface tension. The breakup with gaps consisted of three stages: squeezing stage, squeezing-stretching stage and rapid breakup stage. The squeezing stage and the rapid breakup stage were similar to the stage of the breakup with permanent obstruction. The squeezing-stretching was commonly controlled by the viscous force, inertia force and the augment pressure.