Depletion potentials near geometrically structured substrates

TL;DR

This paper uses advanced density functional theory to calculate how colloidal particles interact with structured surfaces like wedges and edges, revealing strong attractions and barriers that influence suspension behavior.

Contribution

It applies the White Bear version of Rosenfeld's Fundamental Measure Theory to quantify depletion potentials near complex geometries, a novel approach for such structured substrates.

Findings

Strong attraction of particles in wedge geometries.

Presence of a free energy barrier near edges.

Results align with experimental observations.

Abstract

Using the recently developed so-called White Bear version of Rosenfeld's Fundamental Measure Theory we calculate the depletion potentials between a hard-sphere colloidal particle in a solvent of small hard spheres and simple models of geometrically structured substrates: a right-angled wedge or edge. In the wedge geometry, there is a strong attraction beyond the corresponding one near a planar wall that significantly influences the structure of colloidal suspensions in wedges. In accordance with an experimental study, for the edge geometry we find a free energy barrier of the order of several $k_B T$ which repels a big colloidal particle from the edge.