Mapping nanostructural variations in silk by secondary electron hyperspectral imaging

Nanostructures underpin the excellent properties of silk. Although the bulk nanocomposition of silks has been well studied, direct evidence of the spatial variation of nanocrystalline (ordered) and amorphous (disordered) structures has remained elusive. Here we demonstrate that secondary electron hyperspectral imaging, can be exploited for direct imaging of hierarchical structures in carbon based materials which cannot be revealed by any other standard characterization methods. Applying this technique to silks from domesticated (Bombyx mori) and wild (Antheraea mylitta) silkworms, we report a variety of previously unseen features which highlight the local interplay between ordered and disordered structures. We conclude that our technique is able to differentiate composition on the nanoscale and enables in-depth studies into the relationship between morphology and performance of these complex biopolymer systems.