Tunable particle shells of thermo-responsive liquid marbles under alternating magnetic field

Abstract

Liquid marbles, droplets entrapped in a solid particle shell at the air–liquid interface, can respond to stimuli such as alternating magnetic fields. In this study, we examined liquid marbles composed of the ferrofluid core covered by diverse particles, including thermo-responsive polymer microspheres. The temperature elevation induced by an alternating magnetic field provided the particle surface of the marbles with enhanced properties and broadened the functionality of the entire structure. The thermal response partially rigidified the particle shell, and despite temperature-induced evaporation of the liquid core, the residual shell could be easily refilled with an intended cargo, e.g., an additional portion of ferrofluid or an antibiotic suspension. Due to the presence of magnetic particles inside the droplets, liquid marbles were also responsive to static magnetic fields, enabling control over their position and spatial orientation using magnets. We also obtained patchy and Janus structures employing magneto-coalescence of two or more liquid marbles, underscoring the innovative use of alternating magnetic fields to modulate liquid marble properties potentially serving as delivery agents in various applications.