Dynamic wettability of complex fractal isotropic surfaces – Multiscale correlations

The complexity of surface topography can significantly influence the wettability, lubrication, and, in consequence, wear of materials in tribological contact. Therefore, wettability can be an important factor in contact lubrication. This research aims to find a correlation between a fractal, i.e., geometric, complexity of isotropic surfaces and the wettability at different observation scales. Surface wettability can be characterized under static and dynamic conditions by determining the dynamic contact angle hysteresis. Multiscale geometric correlations of topographic complexity and advancing, receding contact angle interactions are used to discover the best observation scales for strong correlation with dynamic surface lubrication. The analytical results confirmed that there is a certain range of scales in which the correlation coefficients between topographic complexity and dynamic wettability are strong (r > 0.9). This paper describes a novel characterization of surface-functionality interactions by dynamic lubrication of isotropic surfaces in a multiscale aspect. • The topographic complexity of the surface depends on the scale of observation • Strong correlations occur between topography and dynamic wettability at specific scales • Area-scale complexity strongly correlates with contact angle hysteresis at certain scales • The increase in topographic complexity reduces the wettability of the surface