Computational Fluid Dynamics Models for the Rational Design of Magnetic Microseparators – In Memory of Dr. Ed Furlani

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In this work, we report a numerical flow-focused study of bead magnetophoresis inside a continuous-flow microchannel in order to provide a detailed analysis of bead motion and its effect on fluid flow. Different Computational Fluid Dynamics (CFD) models are introduced and a screening process is carried out. All the models involve a Lagrangian approach and predicts the bead separation from blood and their collection into a flowing buffer by the application of a magnetic field generated by a permanent magnet. The following scenarios are modelled: i) one-way coupling wherein momentum is transferred from the fluid to beads, which are treated as point particles, ii) two-way coupling wherein the beads are treated as point particles and momentum is transferred from the bead to the fluid and vice versa, and iii) two-way coupling taking into account the effects of bead volume in fluid displacement. The results indicate that although there is little difference in the bead trajectories for the three scenarios, there is significant variation in the flow fields, especially when high magnetic forces are applied on the beads. Therefore, an accurate full flow-focused model that takes into account the effects of the bead motion and volume on the flow field should be solved when high magnetic forces are employed. Nonetheless, when the beads are subjected to medium or low magnetic forces, computationally inexpensive models can be safely employed to model magnetophoresis. The model that provided the best trade-off between computational cost and accuracy was experimentally validated via application to a prototype device employing human whole blood. The impact of a wide range of flow rates on bead recovery was theoretically and experimentally quantified. The performance of the prototype device was characterized using fluorescence microscopy and the experimental results are found to match theoretical predictions within an absolute error of 10%. Overall, it is concluded that the modeling effort presented in this contribution enables understanding of the fundamental physical phenomena involved in magnetophoresis, while offering an ideal parametric analysis and optimization platform. Finally, I would like to express my most sincere gratitude to Dr. Ed Furlani for his invaluable contributions to this work, to whom I will be eternally grateful.

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Journal: TechConnect Briefs
Volume: TechConnect Briefs 2019
Published: June 17, 2019
Pages: 314 - 317
Industry sector: Sensors, MEMS, Electronics
Topicss: Nanoelectronics, Sensors - Chemical, Physical & Bio
ISBN: 978-0-9988782-8-7