title: Self-removal of condensed water on the legs of water striders.
abstract: The ability to control drops and their movements on phobic surfaces is important in printing or patterning, microfluidic devices, and water-repellent materials. These materials are always micro-/nanotextured, and a natural limitation of repellency occurs when drops are small enough (as in a dew) to get trapped in the texture. This leads to sticky Wenzel states and destroys the superhydrophobicity of the material. Here, we show that droplets of volume ranging from femtoliter (fL) to microliter (μL) can be self-removed from the legs of water striders. These legs consist of arrays of inclined tapered setae decorated by quasi-helical nanogrooves. The different characteristics of this unique texture are successively exploited as water condenses, starting from self-penetration and sweeping effect along individual cones, to elastic expulsion between flexible setae, followed by removal at the anisotropic leg surface. We envision that this antifogging effect at a very small scale could inspire the design of novel applicable robust water-repellent materials for many practical applications.
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing 100191, People's Republic of China;
authors.forename: Qianbin
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Biological Sciences, City University of Hong Kong, Hong Kong;
authors.forename: Xi
authors.initials: X
authors.lastname: Yao
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing 100191, People's Republic of China; International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, People's Republic of China;
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.affiliation: Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, École Supérieure de Physique et Chimie Industrielles, 75005 Paris, France; david.quere@espci.fr jianglei@iccas.ac.cn.
authors.forename: David
authors.initials: D
authors.lastname: Quéré
authors.affiliation: Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Beijing 100191, People's Republic of China; Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China david.quere@espci.fr jianglei@iccas.ac.cn.
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
mesh_terms: D000818:Animals; D005121:Extremities / Q000502:physiology*; D020062:Heteroptera / Q000502:physiology*; D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D009038:Motion; D013499:Surface Properties; D014057:Tomography, X-Ray Computed; D014741:Video Recording; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water
keywords: antifogging; breath figure; self-propulsion; water repellency; water strider