Breakup dynamics of water-in-water droplet generation in a flow-focusing microchannel

Abstract

In ATPS, the ultra-low interfacial tension makes the stable generation of droplets very difficult. In this paper, the stable and homogeneous preparation of ATPS droplets is achieved over a wide range of flow rates, and the self-similarity analysis and formation dynamics of the droplets are studied. Formation of ATPS droplets show good self-similarity. The generation process of ATPS droplets can be divided into slow squeezing, fast squeezing and rapid pinch-off stages. In the slow squeezing stage, the dimensionless minimum neck width wm/wc is linear with the time, and the absolute value of the slope increases with the capillary number of continuous phase Cac. In the rapid squeezing and rapid pinch-off stages, the wm/wc satisfies the power-law relationship with time, and the absolute value of the power-law indexes decrease with increasing Cac, and the pre-exponential factor of pinch-off stage increases with increasing Cac.