[Zurück]

S. Pabisch, S. Puchegger, H. Kirchner, I. Weiss, H. Peterlik:
"The structure of keratin in the tail feathers of peacocks - an X-ray diffraction study";
Vortrag: EUROMAT 2011, Montpellier; 12.09.2011 - 15.09.2011; in: "EUROMAT 2011 - European Congress on Advanced Materials and Processes", (2011), 1 S.

X-ray diffraction studies successfully clarified the structure of avian feathers: Each filament has a helical structure with four repeating units per turn [1]. The structure of avian feathers is very stable though their relative density is low. The purpose is to check how the mechanical constancy is based on structural constancy. In this work, peacock feathers were scanned along their whole length (from the origin, the zone of growth, to the end, the zone of splitting) and analysed by X-ray diffraction. It changes considerably over the first 5 cm close to the calamus and remains constant for about 1 m along the length of the feather. Close to the tip, the structure loses its high degree of order. We attribute the X-ray patterns to a shrinkage of a cylindrical arrangement of beta-sheets, which is not fully formed initially. In the final structure, the crystalline beta-cores are fixed by the rest of the keratin molecule. The hydrophobic residues of the beta-core are locked into a zip-like arrangement. The advantage of the molecular mechanism in nature is that no temperature is required, as the soft molecular precursor is stabilized by the forming of covalent bonds, which then result in a very stable configuration. The development of similar materials in polymeric materials used in extrusion dies is a possible future application for bio-inspired materials. In addition, tensile and compression tests are performed in-situ to follow the structural change as consequence of varying load.