Multiscale geometric analysis of dynamic wettability on complex, fractal-like, anisotropic surfaces

TL;DR

This paper presents a multiscale analysis of dynamic wettability on complex anisotropic surfaces, revealing how surface microgeometry at specific scales influences droplet behavior and advancing measurement techniques for surface wettability characterization.

Contribution

It introduces a novel multiscale measurement approach to analyze the relationship between surface topography and dynamic wettability on anisotropic surfaces.

Findings

Identified key length- and area-scales (6.9 um and 28 um²) that correlate with wettability.

Demonstrated the influence of micro- and macro-scale surface features on droplet pinning.

Provided insights into how material hydrophilicity/hydrophobicity affects wettability at different scales.

Abstract

This study introduces novel insights into the development of procedures for identifying the most relevant scales for observing the interactions of dynamic wettability and surface complexities. The experimental procedures presented for measuring dynamic contact angle hysteresis in multiscale correlation with the geometric characteristics of anisotropic surfaces contribute to a new perspective on measurement practice. In this study, microtexturing with a pyramidal structured abrasive belt is applied for precisely forming area- and length-scale anisotropic surface complexities, and consequently, topographically dependent functional features. The significant role of anisotropic topographies in modeling dynamic wettability behavior is highlighted through multiscale measurement-based analysis. These studies verify the relationship between dynamic wettability and the finest surface microgeometry (microroughness) and also the coarsest texture components (waviness). The size of topographic features, ranging from microroughness to waviness, significantly influences droplet pinning and liquid entrapment. Furthermore, the influence of material hydrophilicity and hydrophobicity on the calculated multiscale relationships is assessed. The results indicated specific scales that best correlate with dynamic wettability, with length- and area-scale complexities of 6.9 um and 28 um2, respectively. A novel measurement-based approach to scale-dependent surface-functionality interactions offers new insights for designing dynamic wettability on anisotropic surfaces.