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Abstract
Copyright © 2019 American Chemical Society. 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.
Highlights
The use of droplet-based microfluidics has increased in the last decade as it enables the precise handling of minute amounts of fluid, e.g. nano- and picoliter-sized microreactors.These systems possess multiple advantages such as high interfacial areas and short diffusion distances which facilitate mass and heat transfer at the microscale
The goal of the present study is to systematically study the dynamics of ferrofluid droplet generation in an immiscible, non-magnetic Newtonian medium, and the later manipulation when actuated by spatially non-uniform magnetic fields in a millimetersized chamber
Oil-based ferrofluid dispersed phase (DP) was pumped into the inlet 1 at a flow rate of 10 μL·h-1 while an aqueous continuous phase (CP) was pumped into inlet 2 at a range of flow rates between 100 and 500 μL·h-1
Summary
The use of droplet-based microfluidics has increased in the last decade as it enables the precise handling of minute amounts of fluid, e.g. nano- and picoliter-sized microreactors. These systems possess multiple advantages such as high interfacial areas and short diffusion distances which facilitate mass and heat transfer at the microscale. This involves the application of an electrical potential to an array of electrodes patterned on a hydrophobic surface that causes variation in surface wettability.[2] Other actuation mechanisms have been reported as well for digital microfluidics like the magnetic and the surface acoustic wave (SAW) technologies.[3,4]
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