title: Why do pigeon feathers repel water? Hydrophobicity of pennae, Cassie-Baxter wetting hypothesis and Cassie-Wenzel capillarity-induced wetting transition.
abstract: Wetting of pigeon feathers has been studied. It was demonstrated that the Cassie-Baxter wetting regime is inherent for pigeon pennae. The water drop, supported by network formed by barbs and barbules, sits partially on air pockets. Small static apparent angle hysteresis justifies the Cassie-Baxter wetting hypothesis. A twofold structure of a feather favors large contact angles and provides its water repellency. Cassie-Wenzel transition has been observed under drop evaporation, when drop radius becomes small enough for capillarity-induced water penetration into the protrusions, formed by barbules.
authors.affiliation: The College of Judea and Samaria, The Research Institute, 44837, Ariel, Israel. edward@yosh.ac.il
authors.forename: Edward
authors.initials: E
authors.lastname: Bormashenko
authors.forename: Yelena
authors.initials: Y
authors.lastname: Bormashenko
authors.forename: Tamir
authors.initials: T
authors.lastname: Stein
authors.forename: Gene
authors.initials: G
authors.lastname: Whyman
authors.forename: Ester
authors.initials: E
authors.lastname: Bormashenko
mesh_terms: D000818:Animals; D002197:Capillary Action; D010856:Columbidae; D005241:Feathers / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D013499:Surface Properties; D014867:Water / Q000737:chemistry; D017155:Wettability
chemical_list: D014867:Water