Investigation of Factors that Control Droplet Formation in Microfluidic Cross-Junctions Using the Lattice Boltzmann Method

Abstract

Microfluidics could potentially provide a cheaper and more effective alternative to current industrial and laboratory fluid management techniques due to the large surface area-to-volume ratios; however, optimization of the flow conditions necessary for precise droplet generation is required for any segmented flow application. The Shan-Chen multicomponent multiphase Lattice Boltzmann method was used to simulate droplet formation conditions and provide insight about the conditions for different flow regimes like streaming, threading, and stable droplet generation. For the range of numerically stable flow conditions tested, the combined effects of the Capillary number and velocity ratio were demonstrated to be the process drivers for the cross-junction droplet size while the other dimensionless numbers had a less significant effect. Future studies include the analysis of other multiphase models to improve the numerical stability and reduce spurious velocities. In addition, there has already been some success in incorporating tracer particles into cross-junction droplets to quantify mixing during droplet coalescence. Further improvements will incorporate suspended magnetic particles to simulate the afforded mixing and separation capabilities.