Breakup of drops in a microfluidic T junction

We propose a mechanism of droplet breakup in a symmetric microfluidic T junction driven by pressure decrement in a narrow gap between the droplet and the channel wall. This mechanism works in a two-dimensional setting where the capillary Rayleigh–Plateau instability of a cylindrical liquid thread, suggested earlier D. Link, S. Anna, D. Weitz, and H. Stone, Phys. Rev. Lett. 92, 054503 2004 as the cause of breakup, is not operative, but it is likely to be responsible for the breakup also in three dimensions. We derive a dependence of the critical droplet extension on the capillary number Ca by combining a simple geometric construction for the interface shape with lubrication analysis in a narrow gap where the surface tension competes with the viscous drag. The theory, formally valid for Ca1/5 1, shows a very good agreement with numerical results when it is extrapolated to moderate values of Ca. © 2009 American Institute of Physics. DOI: 10.1063/1.3078515