Computational fluid dynamics analysis of droplet generation in microfluidic multi-cell coupled systems

Multi-cell coupled droplet generator systems have been used for high-throughput production of microdroplets. However, the coupling effects of intercellular geometry and flow parameters can produce complex hydrodynamic phenomena that affect droplet generation processes and properties. In this study, a computational model of droplet generation in a multi-cell parallel geometry was developed based on the phase field method, and the droplet formation process and hydrodynamic properties in a multi-cell coupled droplet generator were investigated. The coupling effects of flow parameters (e.g., capillary number, continuous and dispersed phase flow rates and flow ratios) on the droplet generation process were systematically analyzed to investigate droplet characteristics and mechanisms in the multi-cell coupled droplet generator system. The causes of synchronous and asynchronous droplet generation patterns in multi-cell coupled systems are also analyzed over a range of capillary numbers. It is found that the droplet generation frequency increases with increasing continuous-phase flow velocity while the size decreases; the droplet size is smaller and the frequency is larger in multi-cell coupled systems than in stand-alone systems at the same flow velocity ratio; the difference between synchronous and asynchronous droplet generation patterns is closely related to the geometric coupling of continuous-phase flow channels and the uneven flow field distribution. This work will provide useful insights into droplet generation in multi-cell coupled systems and provide useful guidance for the structural design of multi-cell coupled systems.