Modeling of droplet generation at shallow microfluidic T-junction*

Generation of droplets at the T-junction is one of the unit operations of droplet-based microfluidics. As was previously demonstrated in [1] the droplet generation at the T-junction formed from square cross-section microchannels is a purely geometric process controlled by the single dimensionless parameter – the flow rate ratio of the continuous and disperse phases. However, when the microfluidic T-junction and the channels are made shallow, the droplet generation is no longer geometrically mediated and it exhibits various (squeezing, tearing and jetting) regimes depending on the capillary number, Ca. In this talk, we present a robust numerical approach for modelling this process. Quasi-2D Hele-Shaw hydrodynamics is employed using single-fluid formulation combined with interface capturing scheme based on Coupled level-set and Volume-of-Fluid methods. The numerical results show excellent agreement with in-house experiments on droplet generation at the microfluidic Hele-Shaw T-junction, confirming the Ca^-1/3 dependence of the droplet volume in “tearing” regime.

[1] Garstecki et al., Lab Chip, 6, 437 (2006)