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

• Published in: Microfluidics and nanofluidics 2017-05, Vol.21 (5), p.1, Article 94
• Main Authors: Nishimura, Akio, Schmit, Alexandre, Salkin, Louis, Courbin, Laurent, Panizza, Pascal
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Barriers; Biomedical Engineering and Bioengineering; Capillary flow; Condensed Matter; Continuity (mathematics); Drop size; Droplets; Engineering; Engineering Fluid Dynamics; Fluid dynamics; Fluids; Mathematical analysis; Mathematical models; Microfluidics; Nanotechnology and Microengineering; Physics; Research Paper; Size distribution; Soft Condensed Matter; Viscosity ratio
• ISSN: 1613-4982; 1613-4990
• DOI: 10.1007/s10404-017-1930-7

A 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.