CFD Analysis of the Generation and Manipulation of Ferrofluid Droplets

I.H. Karampelas, J. Gómez-Pastora, V. Amiri, M.D. Tarn, E. Bringas, A. Iles, N. Pamme, E.P. Furlani, I. Ortiz
Flow Science, Inc.,
United States

Keywords: magnetic droplets, multilaminar flow microfluidic systems, CFD modeling, droplet generation, droplet deflection


In recent years, there has been a significant increase of droplet-based microfluidic systems. This is mostly due to the advantages that such systems present such as chemical and bio-compatibility, the ability to perform a variety of “digital fluidic” operations that can be programmed and reconfigured, decreased reaction times because of large interfacial areas, repeatability of operations and others. Nonetheless, with the increased popularity of this technology, more sophisticated and delicate control of the processes governing droplet generation and manipulation is necessary in order to address increasingly complex applications. On the other hand, magnetic separation is a useful and efficient method for manipulating materials that exhibit magnetic properties in microfluidic devices. In this study, we present a numerical CFD model that combines the aforementioned techniques to further understanding of the generation and deflection of ferrofluid droplets through multilaminar flow streams. Various microfluidic system designs are examined and an optimization study on the generation and subsequent manipulation of droplets through permanent magnets is performed. This numerical approach includes the integration of Furlani’s analytical model for permanent magnets within the commercial CFD solver FLOW-3D. The CFD analysis is performed using the volume-of-fluid (VOF) method, which very accurately describes the droplet generation and motion under different magnetic fields and flow conditions in a multi-phase channel. For the implementation of magnetic forces, the flow solver was linked to a FORTRAN subroutine that calculates the magnetic field and the corresponding magnetic force exerted on the droplet. We also examine the impact of different process variables such as flow rate, magnet position etc. on both droplet volume and predicted path. Finally, the CFD model is experimentally validated using oil-based ferrofluid droplets and ink aqueous solutions. Theoretical and experimental results are compared and discussed. Owing to its unique advantages, this magnetic droplet technology has the potential to provide novel solutions to different biomedical engineering challenges for advanced diagnostics and therapeutics.