The breakup dynamics and mechanism of viscous droplets in Y-shaped microchannels

The breakup process of viscous droplets in Y-shaped microchannel was visually investigated. The dynamics of droplet breakup with partial obstruction was primarily studied due to its wide operating range and applicability. The rupture process of droplet could be divided into squeezing, transition and rapid pinch-off stages. In the squeezing stage, the minimum neck width displays a power-law relation with time, and the power-law index alpha decreases with increasing two-phase viscosity ratio lambda. The effect of the capillary number of continuous phase Ca-c and the length of the mother droplet l(0) on alpha is nearly negligible. In the transition stage, the minimum neck width varies linearly with time, and the slope increases with decreasing lambda, increasing Ca-c and l(0). In the rapid pinch-off stage, the minimum neck width declines exponentially with time, and the power-law index beta decreases with increasing lambda and decreasing l(0), however, it is almost independent of Ca-c. (C) 2020 Elsevier Ltd. All rights reserved.