Shape deformation of magnetically levitated fluid droplets

TL;DR

This paper investigates the shape deformation of magnetically levitated fluid droplets through experiments and simulations, revealing potential applications in high-resolution magnetic gradiometry.

Contribution

It introduces a combined experimental and simulation approach to analyze droplet shape deformation and demonstrates its use in magnetic field gradient measurements.

Findings

Good agreement between experiments and simulations on droplet shape.

Eccentricity of droplets can be used for magnetic gradiometry.

Potential resolution of $S\sim 8\,\mathrm{nT/cm}$ in magnetic measurements.

Abstract

Diamagnetic levitation can provide a completely passive method to support materials against the pull of gravity, and researchers have levitated both solids and fluids. Such levitation can be assisted by increasing the magnetic susceptibility contrast by using a surrounding paramagnetic medium and through buoyancy forces, known as magneto-Archimedean levitation. The magneto-Archimedean levitation of solids has proved useful in chemistry and biology. However, the levitation of fluid droplets has an additional interest because the fluid droplet's shape can deform. We perform experiments and simulations to gauge the squashing or eccentricity of the static magnetically levitated fluid droplet. By carefully characterizing all the parameters affecting the droplet's levitation, using image analysis to estimate the droplet's eccentricity, and using finite element adaptive simulations to find the lowest energy droplet shape, we find good agreement between the simulations and experimental results. As a potential application, we show that the droplet's eccentricity can be used to perform magnetic gradiometry with a potential resolution of $S\sim 8\,{\rm nT/cm}$, over a volume of 10 mm$^3$, which is competitive with other room-temperature magnetic gradiometer techniques.