Tuning surface wettability using single layered and hierarchically ordered arrays of spherical colloidal particles

A control over wetting properties of a surface can be achieved by tuning surface roughness and surface chemistry. In this study, we formed single layer roughness and dual levels of hierarchical roughness with hexagonal non-contiguously close packed (HNCP) patterns of spherical particles using colloidal lithography. Surface chemistry was controlled using plasma-enhanced chemical vapour deposition (PECVD). A hexagonal unit cell model, which is representative of the HNCP pattern, was used to predict the contact angles. The predictions of this model were in good agreement with experimentally measured contact angles and also provided thermodynamic stability of different wetting state. The systematic thermodynamic analysis of wetting properties is important when using structured surfaces at different hydrostatic pressures, relative humidity, temperature fluctuations or prolonged exposure to water.