Magnetofluidic spreading in circular chambers under a uniform magnetic field
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RESEARCH PAPER
Magnetofluidic spreading in circular chambers under a uniform magnetic field Mohammad Amin Maleki1 · Jun Zhang2 · Navid Kashaninejad2 · Madjid Soltani1,3,4 · Nam‑Trung Nguyen2 Received: 8 February 2020 / Accepted: 8 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Elucidating the microscale interaction between magnetism and fluid flow is of great importance for designing micro-magnetofluidic gradient generators, micromixers, and particle sorters. Co-flowing magnetic and non-magnetic fluids can lead to instability at their interface and subsequent rapid mixing. The mismatch in the magnetisation of the fluids leads to instabilities. The present study systematically investigates the magnetofluidic spreading phenomena of both magnetic nanoparticles and non-magnetic fluorescent dye in consecutive circular chambers. Numerical simulations and experimental investigations were conducted to thoroughly evaluate the physics of magnetofluidic spreading. We show that the presence of the consecutive chambers can enhance magnetofluidic spreading by slowing down the flow and increasing the mass transfer rate transversal to the flow direction. The numerical results reveal that the magnetic force, induced by the magnetic susceptibility gradient, generates cross-sectional secondary flows that steer particles toward both the top and bottom walls. The induced secondary flow also enhances the transport of fluorescent dye, thereby leading to a higher mass transfer rate as compared to pure molecular diffusion. The findings provide further insights into the microscale spreading phenomenon of magnetic and nonmagnetic particles in a magnetic field. Keywords Microfluidics · Magnetofluidic spreading · Numerical modelling · Circular chambers · Ferrofluid · Micromagnetofluidic gradient generators
1 Introduction
Mohammad Amin Maleki, Jun Zhang and Navid Kashaninejad contributed equally to this work. * Madjid Soltani [email protected] * Nam‑Trung Nguyen nam‑[email protected] 1
Department of Mechanical Engineering, K. N. Toosi University of Technology, 19697 Tehran, Iran
2
Queensland Micro- and Nanotechnology Centre and School of Natural Science, Griffith University, Nathan Campus, 170 Kessels Road, Brisbane, QLD 4111, Australia
3
Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
4
Centre for Biotechnology and Bioengineering (CBB), University of Waterloo, Waterloo, ON N2L 3G1, Canada
Continuous-flow microfluidics enables manipulation of particles in a fluid. Passive manipulation methods depend merely on hydrodynamic forces (Moghadas et al. 2018), while active methods employ external sources such as acoustic (Marzo et al. 2015), electrical (Tajik et al. 2019), optical (Diekmann et al. 2016), thermal (D’Eramo et al. 2018) and magnetic (Munaz et al. 2018) actuators. Among active methods, magnetic manipulation has attracted considerable attention because of its high efficiency, cost-effectiveness and straightfo
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