Self-assembly of Colloidal Superballs Under Spherical Confinement of a Drying Droplet

TL;DR

This study investigates how colloidal superballs self-assemble under spherical confinement during drying, revealing four drying regimes and the formation of shape-dependent paracrystalline structures, advancing understanding of shape-driven self-assembly.

Contribution

It demonstrates the shape-dependent assembly of colloidal superballs into ordered structures under spherical confinement, using SAXS to track structural development during drying.

Findings

Four distinct drying regimes identified during evaporation.

Superballs assemble into shape-dependent paracrystalline lattices.

Internal structure varies with particle shape.

Abstract

Understanding the relationship between colloidal building block shape and self-assembled material structure is important for the development of novel materials by self-assembly. In this regard, colloidal superballs are unique building blocks because their shape can smoothly transition between spherical and cubic. Assembly of colloidal superballs under spherical confinement results in macroscopic clusters with ordered internal structure. By utilizing Small Angle X-Ray Scattering (SAXS), we probe the internal structure of colloidal superball dispersion droplets during confinement. We observe and identify four distinct drying regimes that arise during compression via evaporating droplets, and we track the development of the assembled macrostructure. As the superballs assemble, we found that they arrange into the predicted paracrystalline, rhombohedral C1-lattice that varies by the constituent superballs' shape. This provides insights in the behavior between confinement and particle shape that can be applied in the development of new functional materials.