Controlled Capillary Assembly of Magnetic Janus Particles at Fluid-Fluid Interfaces

TL;DR

This paper explores the controlled assembly of magnetic Janus particles at fluid interfaces using capillary interactions, developing a model and simulations to predict and observe their ordered structures and tunability via magnetic fields.

Contribution

It introduces a pair-interaction model for magnetic Janus particles and demonstrates their ability to form tunable, ordered monolayer structures at fluid interfaces.

Findings

Particles form side-side configurations as predicted by the model.

Magnetic Janus particles assemble into long, straight chains with minimal curvature.

External magnetic fields can dynamically tune the monolayer structures.

Abstract

Capillary interactions can be used to direct assembly of particles adsorbed at fluid-fluid interfaces. Precisely controlling the magnitude and direction of capillary interactions to assemble particles into favoured structures for materials science purposes is desirable but challenging. In this paper, we investigate capillary interactions between magnetic Janus particles adsorbed at fluid-fluid interfaces. We develop a pair-interaction model that predicts that these particles should arrange into a side--side configuration, and carry out simulations that confirm the predictions of our model. Finally, we investigate the monolayer structures that form when many magnetic Janus particles adsorb at the interface. We find that the particles arrange into long, straight chains exhibiting little curvature, in contrast with capillary interactions between ellipsoidal particles. We further find a regime in which highly ordered, lattice-like monolayer structures form, which can be tuned dynamically using an external magnetic field.