Two-Step Numerical Approach to Predict Ferrofluid Droplet Generation and Manipulation inside Multilaminar Flow Chambers

In this study, a computational fluid dynamics approach is implemented to investigate the dynamic behavior of continuous-flow droplet microfluidics. The developed approach predicts both droplet generation and manipulation in a two-step process. First, droplet formation was studied in a flow-focusing junction through an Eulerian-Eulerian approach. Surface tension and wall adhesion were used in the model. The effect of flow rates and geometrical characteristics of the device on droplet size and dispensing rate was investigated. Second, post-generation, droplets were treated as point-like particles, and their deflection across a millimeter, multilaminar flow chamber with five parallel streams was modeled using an Eulerian-Lagrangian approach, thus improving computational efficiency. Flow rates and magnet location were optimized. Our simulated droplet trajectory inside the chamber was contrasted against experimental data, and a good agreement was found between them. This two-step computational model enables the rational optimization of continuous-flow droplet processing, and it can be readily adapted to a broad range of magnetically enabled microfluidic applications.