title: Moulding technique demonstrates the contribution of surface geometry to the super-hydrophobic properties of the surface of a water strider.
abstract: Water striders (Insecta, Heteroptera, Gerridae) have a complex three-dimensional waterproof hairy cover which renders them super-hydrophobic. This paper experimentally demonstrates for the first time the mechanism of the super-hydrophobicity of the cuticle of water striders. The complex two-level microstructure of the surface, including the smallest microtrichia (200-300 nm wide, 7-9 microm long), was successfully replicated using a two-step moulding technique. The mould surface exhibited super-hydrophobic properties similar to the original insect surface. The average water contact angle (CA) of the mould was 164.7 degrees , whereas the CA of the flat polymer was about 92 degrees . These results show that (i) in water striders, the topography of the surface plays a dominant role in super-hydrophobicity, (ii) very low surface energy bulk material (typically smaller than 0.020 N m(-1)) is not necessary to achieve super-hydrophobicity; and (3) the two-step moulding technique may be used to mimic quite complex biological functional surfaces.
authors.affiliation: Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, 606-8414 Kyoto, Japan.
authors.forename: Pablo Perez
authors.initials: PP
authors.lastname: Goodwyn
authors.forename: Emerson
authors.initials: E
authors.lastname: De Souza
authors.forename: Kenji
authors.initials: K
authors.lastname: Fujisaki
authors.forename: Stanislav
authors.initials: S
authors.lastname: Gorb
mesh_terms: D000005:Abdomen; D000818:Animals; D001696:Biomechanical Phenomena / Q000379:methods*; D020062:Heteroptera / Q000378:metabolism* / Q000648:ultrastructure; D057927:Hydrophobic and Hydrophilic Interactions; D013499:Surface Properties; D014867:Water
chemical_list: D014867:Water