Breakup dynamics of gas-liquid interface during Taylor bubble formation in a microchannel flow-focusing device

Abstract This work aims to investigate the breakup dynamics of the gas-liquid interface during bubble formation in a microchannel flow-focusing device. An interface tracking method is developed to capture the profiles of the gaseous thread evolution. The results show that the pinch-off period can be further divided into a liquid squeezing stage and a free pinch-off stage in both the radial and axial directions. The time domain criterion between these two stages in a low viscous liquid, with Ohnesorge numbers Oh ≪ 1 , is proved to be shorter than the capillary time. The effects of surface tension, viscosity and gas inertial force exerting on the interface during the free pinch-off stage are proved similar to those in a quiescent liquid pool. The power law of the minimum diameter at the gaseous thread to the pinch-off remaining time in the present experiments agrees with previous studies in both ranges (1/3 to 1/2) and tendency.