Abstract
Continuous phase plays a crucial role in droplet formation as it significantly influences both the droplet size and the rate of formation. A clear understanding of this relationship is essential for optimizing droplet production and achieving consistent, controlled outcomes in microfiuidic applications. Recent experimental studies on step emulsification have utilized high continuous phase flow rates to expedite droplet detachment and enhance generation rates. However, the precise effects of this flow have not yet been thoroughly investigated. This study presents a comprehensive three-dimensional, time-dependent numerical study of droplet generation in a step-emulsification microdevice, focusing on the effects of the flow rate of the continuous phase. The Level-Set (LS) method was employed to simulate the droplet formation process, modeling both the continuous and dispersed phases in motion to investigate the effects of the continuous phase. The underlying physics of the phenomenon was analyzed using force balance alongside the pressure, velocity, and vorticity fields. Subsequently, the simulations revealed that higher continuous phase flow rates substantially influence droplet size and formation time, resulting in smaller droplets and increased generation rates. Notably, a tenfold increase in flow rates could shorten the necking and pinch-off duration by 50% and reduce droplet sizes by 40% under specific conditions. These effects were studied across different device geometries, contact angles, and continuous phase viscosities, examining the extent of their impact under these variations. This work offers key insights into optimizing the step emulsification devices by examining the continuous phase's impact, paving the way for more efficient and scalable high-throughput designs.
NETL
NSTL
Springer Nature