Modeling droplet formation in microfluidic flow-focusing devices using the two-phases level set method

Abstract

Droplet-based microfluidics is an emerging field that has found its way in different applications like material science and biotechnology. Knowing how factors like capillary number, surface tension, velocity ratio, viscosity ratio, and contact angle affect droplet formation is of upmost importance for the design of microfluidic platforms. In this study, we evaluate how these factors affect droplet formation by using the two-phase level set method, measuring its length and frequency. Additionally, to assess how channel geometry affects droplet length and frequency, we considered the three most commonly used flow-focusing geometries in microfluidic platforms. As a general conclusion, we found that the droplet length decreases when the capillary number, velocity ratio, and viscosity ratio increase, while it increases when surface tension increases as well. The frequency of droplet formation augments when the capillary number, velocity ratio, and viscosity ratio increase, while it decreases when surface tension increases. We found that geometry influences droplet length, while it has minor effects on droplet formation frequency. Moreover, the contact angle has a low effect on both droplet length and formation frequency in flow focusing devices compared to other studies carried out using different geometries like the T-junction.