Filling and wetting transitions at grooved substrates

TL;DR

This study uses microscopic density functional theory to explore how fluid wetting and filling behaviors on grooved substrates depend on geometric parameters, revealing multiple wetting states and transitions influenced by temperature and morphology.

Contribution

It introduces a detailed microscopic analysis of wetting transitions on grooved surfaces, highlighting the impact of geometry on wetting regimes and transition characteristics.

Findings

Four distinct wetting states identified: empty, filled, hemispherical caps, fully wet.

Transition behaviors are highly sensitive to groove geometry and temperature.

Complete wetting occurs at higher temperatures compared to flat surfaces.

Abstract

The wetting and filling properties of a fluid adsorbed on a solid grooved substrate are studied by means of a microscopic density functional theory. The grooved substrates are modelled using a solid slab, interacting with the fluid particles via long-range dispersion forces, to which a one-dimensional array of infinitely long rectangular grooves is sculpted. By investigating the effect of the groove periodicity and the width of the grooves and the ridges, a rich variety of different wetting morphologies is found. In particular, we show that for a saturated ambient gas, the adsorbent can occur in one of four wetting states characterised by i) empty grooves, ii) filled grooves, iii) a formation of mesoscopic hemispherical caps iv) a macroscopically wet surface. The character of the transition between particular regimes, that also extend off-coexistence, sensitively depends on the model geometry. A temperature at which the system becomes completely wet is considerably higher than that for a flat wall.