Preparation and characterization of hydrophobic nano silver film on butterfly wings as bio-template

Abstract

Hydrophobic nano silver films were fabricated on butterfly wings as bio-template. The micrometric/nano structures and hydrophobicity of the surfaces were investigated with the help of scanning electron microscope(SEM) and video-based contact angle meter. The hydrophobic mechanism of silver film was analyzed with the aid of Cassie’s formula. On the nano silver films of various thicknesses(5, 10, 20, 40, 60, 80, 100 nm), all the contact angles( CAs) of water were bigger than 120°. When the silver film was 5 nm, the CAs of water on it on the wing surfaces of Mimathyma nycteis and Speyeria aglaja were 143.2° and 139.2°, respectively. Coated with the sliver film of the same thickness, butterfly wing surface exhibited the CA remarkably bigger than glass slide surface, exhibiting its high hydrophobicity. With the increase of silver film thickness on butterfly wing surface, the hydrophobicity kept decreasing. The micrometric/nano hierarchical structures on butterfly wing surface result in the transition of metal silver from hydrophilicity to hydrophobicity.