Computer simulations of colloidal transport on a patterned magnetic substrate

TL;DR

This study uses computer simulations to analyze how paramagnetic colloidal particles move on patterned magnetic substrates under oscillating magnetic fields, revealing control mechanisms for particle transport based on substrate pattern and field parameters.

Contribution

It introduces a combined simulation approach to investigate magnetic field-controlled colloidal transport on patterned substrates, highlighting new control strategies and transport limitations.

Findings

Particle current controlled by magnetic field tilt angle.

Transport occurs only above a critical oscillation period.

High density causes jamming, hindering transport.

Abstract

We study the transport of paramagnetic colloidal particles on a patterned magnetic substrate with kinetic Monte Carlo and Brownian dynamics computer simulations. The planar substrate is decorated with point dipoles in either parallel or zigzag stripe arrangements and exposed to an additional external magnetic field that oscillates in time. For the case of parallel stripes we find that the magnitude and direction of the particle current is controlled by the tilt angle of the external magnetic field. The effect is reliably obtained in a wide range of ratios between temperature and magnetic permeability. Particle transport is achieved only when the period of oscillation of the external field is greater than a critical value. For the case of zigzag stripes a current is obtained using an oscillating external field normal to the substrate. In this case, transport is only possible in the vertex of the zigzag, giving rise to a narrow stream of particles. The magnitude and direction of the particle current are found to be controlled by a combination of the zigzag angle and the distance of the colloids from the substrate. Metropolis Monte Carlo and Brownian dynamics simulations predict results that are in good agreement with each other. Using kinetic Monte Carlo we find that at high density the particle transport is hindered by jamming.