Building micro-soccer-balls with evaporating colloidal fakir drops

TL;DR

This paper introduces a novel method for creating micro-structured colloidal spheres by evaporating droplets on superhydrophobic surfaces, allowing control over particle packing and size.

Contribution

The study demonstrates a new technique for fabricating colloidal microstructures with tunable packing fractions using evaporation on specialized superhydrophobic surfaces.

Findings

Final particle packing fraction depends on evaporation dynamics.

Micro-spheres range from tens to hundreds of microns in diameter.

Method enables controlled fabrication of micro-structures.

Abstract

Evaporation-driven particle self-assembly can be used to generate three-dimensional microstructures. We present a new method to create these colloidal microstructures, in which we can control the amount of particles and their packing fraction. To this end, we evaporate colloidal dispersion droplets on a special type of superhydrophobic micro-structured surface, on which the droplet re- mains in Cassie-Baxter state during the entire evaporative process. The remainders of the droplet consist of a massive spherical cluster of the microspheres, with diameters ranging from a few tens up to several hundreds of microns. We present scaling arguments to show how the final particle packing fraction of these balls depends on the dynamics of the droplet evaporation.