Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2336 | Acta Biomaterialia | 2008 | 5 Pages |
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 μm 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°, whereas the CA of the flat polymer was about 92°. 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.