title: The rose petal effect and the modes of superhydrophobicity.
abstract: 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.
authors.affiliation: Nanoprobe Laboratory for Bio- and Nanotechnology and Biomimetics (NLBB), The Ohio State University, 201 West 19th Avenue, Columbus, OH 43210-1142, USA. bhushan.2@osu.edu
authors.forename: Bharat
authors.initials: B
authors.lastname: Bhushan
authors.forename: Michael
authors.initials: M
authors.lastname: Nosonovsky