Effect of self-affine fractal characteristics of surfaces on wetting

TL;DR

This study experimentally demonstrates how the wetting properties of self-affine fractal surfaces depend on morphological parameters, showing that contact angles can be tuned by adjusting surface roughness and correlation length.

Contribution

It provides new insights into how specific self-affine surface parameters influence wetting behavior, enabling control over hydrophobicity or hydrophilicity.

Findings

Contact angle decreases with increasing local surface slope.

Surface wettability can be tuned by adjusting roughness parameters.

Wetting properties depend on self-affine morphological parameters.

Abstract

The relation between the contact angle of a liquid drop and the morphological parameters of self-affine solid surfaces have been investigated. We show experimentally that the wetting property of a solid surface crucially depends on the surface morphological parameters such as: (1) root mean square (rms) roughness $\sigma$, (2) in-plane roughness correlation length $\xi$ and (3) roughness exponent $\alpha$ of the self-affine surface. We have shown that the contact angle monotonically decreases with the increase in the rms local surface slope $\rho$ ($\propto \sigma/\xi^\alpha$) for the cases where the liquid wets the crevices of the surface upon contact. We have shown that the same solid surface can be made hydrophobic or hydrophilic by merely tuning these self-affine surface morphological parameters.