Microfluidic technology has become a most impacting and innovative research platform in recent times due to its potential applications in many areas of engineering and biomedical fields like emulsions, coatings, paints, mixing reactions, dispersions, DNA analysis, and protein encapsulation. Using the conservative level set method, we numerically investigated the effect of contact angle ranging from 30ο-180ο on droplet formation in a cross-flow microfluidic system. The dimensionless numbers capillary number (5×10-5≤Ca≤1), and Reynolds number (Re=1) are used to understand the interplay of the forces during the droplet breakup. The results compare well with the existing experimental literature. The classification of the flow regimes has been discussed based on the capillary number and contact angle. Furthermore, the evolution of the pressure profiles is analyzed in-depth to explain the droplet breakup mechanism. At low capillary numbers (Ca≤10-2), pressure plays an active role in droplet formation. However, at higher values of Ca, it has been observed that the droplets are not uniform in size due to the dominance of shear stress. The results are presented in terms of phase composition, droplet length, and evolution of the pressure profiles. These insights would help design the microfluidic devices more precisely and guide fundamental understanding of wettability in-depth.

Effect of surface wettability on droplet formation in a cross-flow microfluidic system

ACS Spring 2022

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