Case study: The mechanical properties of primary feathers - a PhD thesis from the University of Southampton

Christian investigated the orientation and thickness of cortical layers in the shafts of feathers and considered how this related to their mechanical properties which permit avian flight. Raman spectroscopy was used as it provides a high-precision analysis of the proteins contained within flight feathers to elucidate their secondary structures. Analysis was made on feathers from four different bird species (gull, kestrel, mallard and swan), specifically targeting variations in the amide I band. The Renishaw Raman inVia confocal microscope was chosen for the work because of its unparalleled precision and reliability, as well as its ability to handle a diverse range of samples without causing damage.

Dr Christian Laurent commented "The high signal to noise ratio offered by inVia allowed me to obtain high quality data in a single pass. As the system was already fitted with the required wavelength laser, this saved time and meant that my research could hit the ground running [...] Using Raman spectroscopy for the first time, I found the Renishaw software easy to use and I could be sufficiently trained in a single session."

To compare proteins in the inner and outer cortical layers of the feather shaft, Christian fitted six curves to the amide I band and compared the ratio between the β-sheet protein peak at 1668 cm^-1 and the 1613 cm^-1 polypeptide side chain peak. This revealed that across the four investigated bird species, the concentration of protein with β-sheet conformation was greater in the inner layer compared to the outer layer. This finding supported Christian's additional work, where he identified for the first time that the Young's modulus value, E, a measure of bending stiffness, was higher in the inner layer than the outer layer. This suggested that the inner layer is more resistant to bending, whilst the outer layer is more resistant to torsion.