Non-contaminating camouflage: Multifunctional skin microornamentation in the West African Gaboon viper (Bitis rhinoceros)

Abstract

The West African Gaboon viper (Bitis rhinoceros) has an extraordinary coloration of pale brown and velvety black markings. The velvety black appearance is caused by a unique hierarchical surface structures which was not found on the pale brown scales. In the present study we examined the wettability of the vipers scales by measuring contact angles of water droplets. Velvet black scale surfaces had high static contact angles beyond 160° and low roll-off angles below 20° indicating an outstanding superhydrophobicity. Our calculations showed that the Cassie-Baxter model describes well wettability effects for these surfaces. Self-cleaning capabilities were determined by contaminating the scales with particles and fogging them until droplets formed. Black scales were clean after fogging, while pale scales stayed contaminated. Black scales feature multifunctional structures providing not only water-repellent but also self-cleaning properties. The pattern of nanoridges can be used as a model for surface-active technical surfaces. © 2014 Spinner et al.