A Numerical Study of Emulsication Process in Microuidic Flow-Focusing Devices

An emulsion is a mixture of two immiscible liquids in which one liquid is dispersed in the form of small drops in the other liquid. The liquid in the form of droplets is called discrete phase whereas the other liquid is termed as a continuous phase. One of the common methods for emulsification is based on using microfluidic devices. Currently, the study of flow in microfluidic devices is highly regarded due to having many applications in various fields including droplet generation in relation with the standard and quality of human life. In this study, the process of droplet generation in microfluidic flow-focusing devices with orthogonal and intersecting flows has been simulated. The effects of viscosity and flow rate of discreted and continuous phases on droplet generation process have been investigated. According to simulation results, with increasing the flow rate of discreted phase (Qd) at a fixed continuous phase leads to the increment of droplet size whereas an increas in the flow rate of continuous phase (Qc) at a fixed discreted phase results in smaller droplet size. Moreover, for a constant Qc/Qd ratio, regardless of whether discrete or continuous phase flow rate is fixed, the equal droplet size is achieved. The higher viscosity of the discrete phase provides a larger droplet size whereas an increase in the viscosity of continuous phase leads to a smaller droplet size. The simulation results in comparison with experimental results show a good agreement confirming the accuracy of the method.