Plasma treatment induced wetting transitions on biological tissue (pigeon feathers).

We report first the wetting transition from superhydrophobicity to superhydrophilicity observed on nitrogen and air plasma irradiated biological tissue (pigeon feathers). Non-irradiated feathers demonstrate pronounced Cassie-Baxter ("fakir") wetting characterized by high apparent contact angles and low sliding angles. Plasma-irradiated feathers are superhydrophilic. Plasma treatment does not affect the barbs/barbules keratin-built network constituting pigeon pennae, but it changes the Young, advancing and receding angles of the tissue. The mechanism of wetting transition is discussed.