Breakup of confined drops against a micro-obstacle: an analytical model for the drop size distribution

Abstract

International audienceA confined drop flowing against a rectangular obstacle placed off-center in a microfluidic conduct may break into two daughter droplets of different volumes when the capillary number at play C, the ratio between viscous and capillary effects, exceeds a threshold C-b. We study the influence of the viscosity ratio p between dispersed and continuous phases on that process by discussing the experimental variations of the volume fraction of the daughter droplets with C and p. A single free parameter model that yields an analytical formula for the volume of the daughter droplets as a function of the variables at play is introduced. Using this model that well describes our experiments, we accurately determine C-b for different p. Our findings underline the key role of confinement on drop breakup showing that C-b is three orders of magnitude smaller than the value found in bulk experiments under shear flow and that C-b decreases with p in our study

Droplets generation under different flow rates in T‐junction microchannel with a neck

“…Meanwhile, in the side view, we take half a circle with a radius h /2 to describe the shape of the droplet as shown in the inset with green edges of Figure 1a. Then the droplet volume can be calculated from the formula of volume for a single direction confined droplet studied in this work as Equation ), 39 …”