Superhydrophobicity and superhydrophilicity of regular nanopatterns.

Martines, Elena; Seunarine, Kris; Morgan, Hywel; Gadegaard, Nikolaj; Wilkinson, Chris D W; Riehle, Mathis O · Nano Lett · 2005

basic_science · Level V

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Abstract

The hydrophilicity, hydrophobicity, and sliding behavior of water droplets on nanoasperities of controlled dimensions were investigated experimentally. We show that the "hemi-wicking" theory for hydrophilic SiO(2) samples successfully predicts the experimental advancing angles and that the same patterns, after silanization, become superhydrophobic in agreement with the Cassie-Baxter and Wenzel theories. Our model topographies have the same dimensional scale of some naturally occurring structures that exhibit similar wetting properties. Our results confirm that a forest of hydrophilic/hydrophobic slender pillars is the most effective superwettable/water-repellent configuration. It is shown that the shape and curvature of the edges of the asperities play an important role in determining the advancing angles.