Numerical Analysis of Controlled Droplet Formation Surrounded by a Shear-Thinning Fluid in a Coflow Microfluidic Device

In this work, we used a coupled level set and volume of fluid (CLSVOF) computational method for studying the generation of microdroplets in a two-dimensional circular coflow microfluidic device. The fundamental understanding of shear-thinning behavior on controlled droplet formation in a microchannel is systematically investigated. Droplet generation and dynamics are controlled by altering the operating conditions and fluid properties, such as CMC solution concentration, both fluids’ flow rates, and interfacial tension. The droplet length, velocity, liquid film thickness, and formation frequency are quantitatively analyzed and presented in a non-dimensional form. The droplet length decreased with the flow rate and concentration of the CMC solution. However, the length of the droplet increased with the dispersed phase flow rate and interfacial tension. From the set of simulation data, flow regime maps and scaling relations are developed over a range of operating conditions. This work provides critical insights into the uniform and controlled droplet formation in shear-thinning fluids within a circular coflow microchannel, offering guidance for future innovations in the design and optimization of microfluidic systems for specific applications.