CFD study of droplet formation in a cross-Junction microfluidic device: investigating the impact of outflow channel design and viscosity ratio

Abstract

This study employed computational fluid dynamics (CFD) to investigate various regimes of droplet formation in a square microfluidic cross-junction device. The first part of the study focused on investigating the impact of viscosity ratios ranging from 0.1 to 5 on droplet characteristics under different flow rate ratios. The transition regime between the dripping and jetting exhibited particularly interesting behavior, with droplet volume being proportional to viscosity ratio. However, when conditions were far from the transition regime, the volume of droplets did not vary significantly with respect to viscosity ratios greater than one. The results of the study indicate the feasibility of reducing droplet volume to the appropriate level while minimizing the impact on the continuous phase's flow rate and the risk of transitioning to jetting. Moreover, in the final part of the study, we investigated the potential of shifting the transition boundary between the squeezing and jetting regimes. Our findings indicate that modifying the outflow channel's design can increase the frequency of droplet generation without altering the operating conditions for both the continuous and dispersed phases.