Numerical simulation of droplet breakup, splitting and sorting in microfluidic device

Droplet generation in flow focusing configuration, splitting and sorting were investigated numerically by using the VOF (Volume of Fluid) commercial code FLUENT. Various parameters which affect the generation of the droplets, including capillary number, geometry of configuration, surface tension and contact angle are systematically analyzed. It shows that the droplet brealup depends on fluid properties such as capillary number, surface tension and the main channel width. We also find that the flow focusing configuration with the smaller main channel width likely to generate stable droplet. The capillary number is an important parameter to define the droplet length and droplet generation frequency. The increase of this parameter leads to the increase of droplet frequency, while it conducts to small droplet length. The numerical simulations of droplet breakup also showed that the obstacle configuration is effective for droplet splitting and sorting, where, daughter split droplet are sorted into smaller droplet that passed through small sub-channel and the bigger passed the bigger sub-channel. We hope this numerical study helps understanding the underlying physics on the droplet dynamics as well as designing the complicated flows in future microfluidic applications. (author)