Magnetic Nanoparticle Dynamics and Assembly Phenomena in External Magnetic Fields

X. Xue, E.P. Furlani
SUNY-Buffalo, US

Keywords: magnetophoresis, magnetic nanoparticle self-assembly, magnetic dipole-dipole interactions, high-gradient magnetic field, assembly of magnetic particle chains, magnetic particle chain dynamics in a time-varying magnetic field


The interest in magnetic nanoparticles and ferrofluids has grown substantially in recent years as their applications continue to proliferate. Current applications are diverse and include the transport of biomolecules and therapeutic drugs [1], gene transfection [2], bioseparation [3], ferrofluidic seals and pumps, microfluidic mixers and magnetoresistive-based sensors, among others. However, despite the widespread and growing use of magnetic nanoparticles, there are many fundamental aspects of their collective behavior that remain unknown. Of particular interest is the self-assembly of the particles in a gradient field and the response of assembled particle-based microstructures in a time-varying field. In this presentation, a computational model is introduced for predicting the field-directed assembly of colloidal magnetic particles under the influence of a high-gradient magnetic field and the manipulation of extended particle chain microstructures in a time-varying field. The model is based on a modified discrete element method and take into account several competitive effects including the applied-magnetic force, induced magnetic dipole-dipole interactions, Brownian dynamics, viscous damping and hydrodynamic interactions among the particles. A dynamic time-stepping approach is used to stabilize and accelerate the computation. The model is demonstrated via application to various nanoparticle systems.