Hard colloidal rods near a soft wall: wetting, drying, and symmetry breaking

TL;DR

This study uses density functional theory to analyze how hard rod-like colloids interact with a soft wall, revealing transitions like wetting, drying, and symmetry-breaking in the fluid's structure.

Contribution

It introduces a theoretical framework to understand the effects of soft surface interactions on the phase behavior of colloidal rods near a substrate.

Findings

Identification of wetting and drying transitions influenced by soft interaction parameters.

Discovery of a pre-drying line indicating complex phase behavior.

Observation of a symmetry-breaking transition from uniaxial to biaxial in the wetting film.

Abstract

Within an Onsager-like density functional theory we explore the thermodynamic and structural properties of an isotropic and nematic fluid of hard needle-like colloids in contact with a hard substrate coated with a soft short-ranged attractive or repulsive layer. As a function of the range and the strength of the soft interactions we find wetting and drying transitions, a pre-drying line, and a symmetry-breaking transition from uniaxial to biaxial in the wetting and drying film.