A dynamic buildup growth model for magnetic particle accumulation on single wires in high‐gradient magnetic separation

Abstract

in Wiley Online Library (wileyonlinelibrary.com).Magnetic fluids containing nano or submicron magnetic particles and their applications to food, biological, and pharmaceutical systems have recently attracted considerable attention. Magnetic particles can be collected efficiently in magnetizable matrices (e.g., iron wires) in high-gradient magnetic separation processes. However, capture efficiencies based on results for clean, particle-free, wires may be seriously in error because the particle accumulation on the wire distorts the flow and the magnetic fields, and thus influences the capture efficiency. A model is developed here in which the dynamic growth process is treated as a moving boundary problem, with the growing front tracked explicitly by marker points distributed evenly over its surface. The flow field and magnetic field are calculated using a finite element method, and a particle trajectory model is used to calculate the deposition flux on the surface. The marker point distribution and the buildup shape are updated at each simulation step. Simulation results show that, for weakly magnetic particles, the accumulation exhibits a smoothly growing front, whereas for strongly magnetic particles, an instability occurs, leading to dendritic growth. The capture efficiency decreases dramatically as particle accumulation increases; and this trend is more prominent for the transverse configuration than it is for the longitudinal configuration. The simulation results show good agreement with experimental results from the literature.

Magnetic microreactors for efficient and reliable magnetic nanoparticle surface functionalization

“…Simulation of magnetic separation units has a long history 20,33,[35][36][37][38][39][40] . A great deal of modeling work has been carried out in the eighties and in the nineties, with the objective to quantify the performances of high gradient magnetic separation (HGMS) units, as they are commonly referred to.…”

“…The equilibrium is more complex in the presence of convection. A comprehensive description of the accumulation kinetics of NPs around an isolated wire requires the solution of a two-dimensional convection-diffusion equation including all the above mentioned mechanisms 39,40 . The detailed equation is reported in the Supplementary Information.…”

Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields

“…However, the steady-state size and shape of the nanoparticle clouds were only found in the limits of flow-dominated (infinite Péclet number) and diffusion-dominated (zero Péclet number) regimes [13,[19][20][21]. Recently, a quite rigorous approach has been proposed by Chen et al [22] who have considered the dynamic growth of the nanoparticle clouds as a moving boundary problem, with the field and the flow fields computed numerically. However, this model as well as most existing theories, did not take into account interactions between magnetic nanoparticles that might lead to underestimation of the capture efficiency and even to unphysical results like particle concentrations above the limit of the maximum packing fraction.…”

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

“…[681] The implant is magnetically energized by the external magnetic field and generates a short ranged local force to positively affect any MDCP in the vicinity of its surroundings [682] due to increase in both magnitude and gradient of the magnetic field. [672,673b] These gradients can be produced by magnetizable implants in the form of stents, [671,683] wires, [683,684] needles or seeds. [685] However, despite the promising potential of IA-MDT, its wide clinical application is encumbered by the cost and risk of surgery.…”