title: Superhydrophobic hierarchically structured surfaces in biology: evolution, structural principles and biomimetic applications.
abstract: A comprehensive survey of the construction principles and occurrences of superhydrophobic surfaces in plants, animals and other organisms is provided and is based on our own scanning electron microscopic examinations of almost 20 000 different species and the existing literature. Properties such as self-cleaning (lotus effect), fluid drag reduction (Salvinia effect) and the introduction of new functions (air layers as sensory systems) are described and biomimetic applications are discussed: self-cleaning is established, drag reduction becomes increasingly important, and novel air-retaining grid technology is introduced. Surprisingly, no evidence for lasting superhydrophobicity in non-biological surfaces exists (except technical materials). Phylogenetic trees indicate that superhydrophobicity evolved as a consequence of the conquest of land about 450 million years ago and may be a key innovation in the evolution of terrestrial life. The approximate 10 million extant species exhibit a stunning diversity of materials and structures, many of which are formed by self-assembly, and are solely based on a limited number of molecules. A short historical survey shows that bionics (today often called biomimetics) dates back more than 100 years. Statistical data illustrate that the interest in biomimetic surfaces is much younger still. Superhydrophobicity caught the attention of scientists only after the extreme superhydrophobicity of lotus leaves was published in 1997. Regrettably, parabionic products play an increasing role in marketing.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'.
authors.affiliation: Nees Institute for Biodiversity of Plants, University of Bonn, Venusbergweg 22, Bonn 53115, Germany barthlott@uni-bonn.de.
authors.forename: W
authors.identifier: http://orcid.org/0000-0002-1990-1912
authors.initials: W
authors.lastname: Barthlott
authors.affiliation: Nees Institute for Biodiversity of Plants, University of Bonn, Venusbergweg 22, Bonn 53115, Germany Institute of Crop Science and Resource Conservation (INRES)-Horticultural Science, University of Bonn, Auf dem Hügel 6, Bonn 53121, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Mail
authors.affiliation: Institute of Botany, Technische Universität Dresden, Zellescher Weg 20b, Dresden 01217, Germany B CUBE Innovation Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, Dresden 01217, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Neinhuis
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001688:Biological Products / Q000737:chemistry*; D040761:Biomimetic Materials / Q000138:chemical synthesis*; D057927:Hydrophobic and Hydrophilic Interactions; D010944:Plants / Q000737:chemistry* / Q000235:genetics; D013499:Surface Properties
chemical_list: D001688:Biological Products
keywords: Notonecta; Salvinia effect; air-retaining grids; bionics; evolution; lotus