Wobbling and Migrating Ferrofluid Droplets

TL;DR

This paper demonstrates that millimeter-sized ferrofluid droplets can be remotely actuated by rotating magnetic fields to wobble, migrate, clean surfaces, and transport cargo, with migration speed controlled by field parameters.

Contribution

It introduces a novel method for controlling ferrofluid droplet motion and functions using rotating magnetic fields, including surface cleaning and cargo transport capabilities.

Findings

Droplets migrate under rotating magnetic fields due to interface wobbling.

Migration speed increases with magnetic field amplitude and frequency.

Droplets can clean surfaces and transport cargo effectively.

Abstract

Active components incorporated in materials generate motion by inducing conformational changes in response to external fields. Magnetic fields are particularly interesting as they can actuate materials remotely. Millimeter-sized ferrofluid droplets placed on a solid surface, surrounded by an ambient gas phase, are shown here to migrate under a rotating magnetic field due to the periodic deformation of the liquid-gas interface. This interface wobbling leads to droplet migration with speeds that increase as the amplitude and frequency of the magnetic field increase. In addition to migrating in a controlled manner, we demonstrate the ability of magnetic droplets to clean surface impurities and transport cargo.