Orientation-Aware Classical DFT for Wetting: Fixing Alcohol Outliers at Solid Interfaces

Extend the classical DFT framework of Bursik et al. (2025) by coupling the scalar density field to an orientational field that captures preferred hydrogen-bond orientations near the solid. Borrow the association treatment and weighted densities from the recent 3D molecular DFT for associating fluids by Barthes et al. (2024), but in a computationally light, mean-field way tailored to surface wetting. The proposed model introduces an anisotropic external potential and an orientational association term that vary within a few molecular layers of the interface—enough to capture the “head-group alignment” of alcohols without a full rotationally resolved MDFT. This approach directly tackles a documented deviation (alcohol overestimation) with minimal added complexity, potentially restoring the excellent mixture predictivity for systems that include alcohols and water. It also generalizes to other polar associating fluids at hydrophobic solids. The impact is a practical, fast, and more universal predictor of macroscopic contact angles in formulations, coatings, and microfluidic design—especially for polar/hydrogen-bonding mixtures where current classical DFTs stumble.

References:

1. Static Contact Angles of Mixtures: Classical Density Functional Theory and Experimental Investigation. B. Bursik, N. Karadimitriou, H. Steeb, Joachim Gross (2025).
2. A molecular density functional theory for associating fluids in 3D geometries.. Antoine Barthes, Thomas Bernet, D. Grégoire, C. Miqueu (2024). Journal of Chemical Physics.