title: Microfluidic separation of magnetic nanoparticles on an ordered array of magnetized micropillars.
abstract: Microfluidic separation of magnetic particles is based on their capture by magnetized microcollectors while the suspending fluid flows past the microcollectors inside a microchannel. Separation of nanoparticles is often challenging because of strong Brownian motion. Low capture efficiency of nanoparticles limits their applications in bioanalysis. However, at some conditions, magnetic nanoparticles may undergo field-induced aggregation that amplifies the magnetic attractive force proportionally to the aggregate volume and considerably increases nanoparticle capture efficiency. In this paper, we have demonstrated the role of such aggregation on an efficient capture of magnetic nanoparticles (about 80 nm in diameter) in a microfluidic channel equipped with a nickel micropillar array. This array was magnetized by an external uniform magnetic field, of intensity as low as 6-10 kA/m, and experiments were carried out at flow rates ranging between 0.3 and 30 μL/min. Nanoparticle capture is shown to be mostly governed by the Mason number Ma, while the dipolar coupling parameter α does not exhibit a clear effect in the studied range, 1.4 < α < 4.5. The capture efficiency Λ shows a strongly decreasing Mason number behavior, Λ∝Ma^{-1.78} within the range 32 ≤ Ma ≤ 3250. We have proposed a simple theoretical model which considers destructible nanoparticle chains and gives the scaling behavior, Λ∝Ma^{-1.7}, close to the experimental findings.
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: G
authors.initials: G
authors.lastname: Orlandi
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: P
authors.initials: P
authors.lastname: Kuzhir
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Izmaylov
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: J
authors.initials: J
authors.lastname: Alves Marins
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.|Laboratory of Physics of Lamellar Materials and Hybrid Nano-Materials, Faculty of Sciences of Bizerte, University of Carthage, 7021 Zarzouna, Tunisia.
authors.forename: H
authors.initials: H
authors.lastname: Ezzaier
authors.affiliation: Franche-Comté Electronique Mécanique Thermique et Optique-Sciences et Technologies, CNRS UMR 6174, 15B avenue des Montboucons, 25030 Besançon, France.
authors.forename: L
authors.initials: L
authors.lastname: Robert
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: F
authors.initials: F
authors.lastname: Doutre
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: X
authors.initials: X
authors.lastname: Noblin
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: C
authors.initials: C
authors.lastname: Lomenech
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: G
authors.initials: G
authors.lastname: Bossis
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, Laboratory of Condensed Matter Physics-UMR 7336, Parc Valrose, 06100 Nice, France.
authors.forename: A
authors.initials: A
authors.lastname: Meunier
authors.affiliation: University of Nice-Sophia Antipolis, CNRS, INSERM, Institut de Biologie de Valrose-UMR 7277, UMR-S 1091, Parc Valrose, 06100 Nice, France.
authors.forename: G
authors.initials: G
authors.lastname: Sandoz
authors.affiliation: Urals Federal University, Lenina Avenue 51, 620083 Ekaterinburg, Russia.
authors.forename: A
authors.initials: A
authors.lastname: Zubarev