A quantitative analysis on the surface roughness and the level of hydrophobicity for superhydrophobic ZnO nanorods grown textiles

This study has identified the quantitative relationship between the level of hydrophobicity and the surface roughness, represented f(1), of superhydrophobic nylon fabrics treated with ZnO nanorods and n-dodecyltrimethoxysilane. With this objective, ZnO nanorods were uniformly grown to give varied particle dimensions on nylon fabrics by a hydrothermal process at a range of solution concentrations. ZnO nanorods, having a unique rod-like hexagonal section structure, were assessed in terms of their dimensions and density to estimate the solid area fraction, f(1), in the Cassie-Baxter model. While the static contact angle did not discriminate between the hydrophobicity of superhydrophobic surfaces, the sliding angle and shedding angle were able to achieve this. The estimated value of f(1) was quantitatively associated with hydrophobicity. The assumption that there was no penetration of into the gaps between nanorods (zero h') appeared to be valid for superhydrophobic surfaces, and this was confirmed by the strong correlation between the increased sliding and shedding angles and the increase in f(1).