The rose petal effect and the modes of superhydrophobicity

• Published in: Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences Vol. 368; no. 1929; pp. 4713 - 4728
• Main Authors: Bhushan, Bharat, Nosonovsky, Michael
• Format: Journal Article
• Language: English
• Published: England The Royal Society 28.10.2010; The Royal Society Publishing
• Subjects: Adhesion; Hysteresis; Liquids; Nanostructures; Petals; Rose Petal; Self-Cleaning; Solid surfaces; Superhydrophobicity; Surface areas; Surface microstructures; Surface roughness; Wetting; Wetting Regimes
• ISSN: 1364-503X; 1471-2962
• DOI: 10.1098/rsta.2010.0203

The wetting of rough surfaces remains a subject of active investigation by scientists. The contact angle (CA) is a traditional parameter used to characterize the hydrophobicity/philicity of a solid surface. However, it was found recently that high CAs can coexist with strong adhesion between water and a solid surface in the case of the so-called 'rose petal effect'. Several additional parameters have been proposed to characterize the interaction of water with a rough solid surface, including the CA hysteresis, the ability of water droplets to bounce off a solid surface, the tilt angle needed to initiate the flow of a droplet, and the normal and shear adhesion. It is clear now that wetting is not characterized by a single parameter, since several modes or regimes of wetting of a rough surface can exist, including the Wenzel, Cassie, lotus and petal. Understanding the wetting of rough surfaces is important in order to design non-adhesive surfaces for various applications.