Orlandi G, Kuzhir P, Izmaylov Y, Alves Marins J, Ezzaier H, Robert L, Doutre F, Noblin X, Lomenech C, Bossis G, Meunier A, Sandoz G, Zubarev A
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.
Phys Rev E. 2016 Jun;93(6):062604. doi: 10.1103/PhysRevE.93.062604. Epub 2016 Jun 10.
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.
磁性颗粒的微流控分离是基于磁化的微收集器对其进行捕获，同时悬浮液在微通道内从微收集器旁流过。由于强烈的布朗运动，纳米颗粒的分离通常具有挑战性。纳米颗粒的低捕获效率限制了它们在生物分析中的应用。然而，在某些条件下，磁性纳米颗粒可能会发生场诱导聚集，这种聚集会使磁吸引力与聚集体体积成比例放大，并显著提高纳米颗粒的捕获效率。在本文中，我们展示了这种聚集在配备镍微柱阵列的微流控通道中对高效捕获磁性纳米颗粒（直径约80纳米）所起的作用。该阵列由强度低至6 - 10 kA/m的外部均匀磁场磁化，实验在流速为0.3至30 μL/min的范围内进行。结果表明，纳米颗粒的捕获主要受梅森数Ma控制，而偶极耦合参数α在所研究的范围1.4 < α < 4.5内未表现出明显影响。捕获效率Λ呈现出梅森数强烈下降的行为，在32 ≤ Ma ≤ 3250范围内，Λ∝Ma⁻¹·⁷⁸。我们提出了一个简单的理论模型，该模型考虑了可破坏的纳米颗粒链，并给出了标度行为Λ∝Ma⁻¹·⁷，与实验结果相近。
