Abstract
In this paper, we study the parameters that affect the generation of droplets in a microfluidic flow-focusing junction. Droplets are evaluated based on the size and frequency of generation. Droplet size control is essential for microfluidic lab-on-a-chip applications in biology, chemistry, and medicine. We developed a three-dimensional numerical model that can emulate the performance of the physical system. A numerical model can help design droplet-generation chips with new junction geometries, different dispersed and continuous phase types, and different flow rates. Our model uses a conservative level-set method (LSM) to track the interface between two immiscible fluids using a fixed mesh. Water was used for the dispersed phase and mineral oil for the continuous phase. The effects of the continuous-to-dispersed flow rate ratio () and the surfactant concentration on the droplet generation were studied both using the numerical model and experimentally. The numerical model was found to render results that are in good agreement with the experimental ones, which validates the LSM model. The validated numerical model was used to study the time effect of changing on the generated droplet size. Properly timing when the flow rates are changed enables control over the size of the next generated droplet, which is useful for single-droplet size modulation applications.
Highlights
Published: 21 May 2021Over the last two decades, droplet-based microfluidics has become a rapidly growing area of research due to its wide range of applications
The process of droplet formation in microfluidic junctions depends on numerous parameters including the junction geometry, the wetting properties of the microchannel, and the flow rates and viscosities of the dispersed and continuous phases, in addition to the interfacial tension between the two fluids [11]
We used a conservative two-phase level-set method to create a three-dimensional numerical model that simulates the generation of water-in-oil droplets in a microfluidic flow-focusing cross-junction
Summary
Over the last two decades, droplet-based microfluidics has become a rapidly growing area of research due to its wide range of applications. The process of droplet formation in microfluidic junctions depends on numerous parameters including the junction geometry, the wetting properties of the microchannel, and the flow rates and viscosities of the dispersed and continuous phases, in addition to the interfacial tension between the two fluids [11]. The LBM model results reveal that both the size of the generated droplets and the flow regimes in microfluidic flow-focusing cross-junctions are affected by the junction geometry, the flow rates of dispersed and continuous phases, and the capillary number [19]. We use a conservative level-set method (LSM) to create a three-dimensional numerical model for the generation of droplets in a microfluidic device with a flow-focusing junction. The model is used to study the transient effect of the change in the continuous phase flow rate on the generated droplet size
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