V. Amiri Roodan, J. Gómez-Pastora, I.H. Karampelas, M.T. Swihart
University at Buffalo,
Keywords: Ferrofluid droplets, Magnetically enabled microfluidics, Fully magnetic coupling, CFD modeling
Summary:The studies about droplet generation and manipulation in microfluidic devices have received a dramatic increase in recent decades. Due to their accurate handling of miniscule amounts of fluid which leads them to have numerous advantages and multiple applications. Their miniaturized analysis system makes them capable to outperform in chemical and biological research. These operations can be optimized and reconfigured using droplet-based microfluidics. However, as demand of using such precise devices rise in different areas, more sophisticated and delicate control of the processes governing droplet generation and their actuation is necessary to address complex applications. Therefore, in this paper, we present numerical models to control and manipulate ferrofluid droplets under an inhomogeneous external magnetic field in microfluidics. The developed model can investigate droplet manipulation in a flow focusing and T-junction microfluidics. The numerical study presents a CFD analysis for optimizing continuous flow processing of generated ferrofluid droplets. The model includes fully coupled magnetic fluid analysis and can predict critical details of the process including droplet size, shape, trajectories, dispensing rate, and the perturbation of the fluid co-flow for five different flow rates. A CFD model is established to explore the dynamics of oil-based ferrofluid droplets within an aqueous continuous phase. The analytical studies were used to model permanent magnet and further combined with CFD analysis using the volume-of-fluid (VOF) method to accurately describe ferrofluid droplet generation. 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. Our results show that the effect of these factors can be optimized through various chip designs, depth of the channel, and hydrodynamics of the both oil and aqueous phases. This model includes the integration of the magnetic analysis with CFD-based models that precisely describe the droplet generation and motion under different flow conditions. Overall, the developed model enables better understanding of physical phenomena involved in the continuous droplet processing and serves as an efficient parametric analysis and optimization platform. Furthermore, this magnetic droplet technology has the potential to provide novel solutions to different point-of-care and biomedical engineering challenges for advanced diagnostics.