monomers are arranged in a strictly controlled manner and are responsible for the formation of well-defined structure [13].
A range of microscopy methods, including SEM, TEM, and AFM, have been used to investigate the microstructure of silk fiber [14-19].
The results confirmed that silk fibers are composed of well-oriented bundles of nanofibrils.
Generally, the coatings of silk fibers function as glue.
The sericin coating, which occupies 25-30% of the weight of B. mori silk fiber, glues the two core brins together. However, recent studies have provided evidences that the coating may act as a fungicidal or bactericidal agent [20].
It may also have a role in the complex spinning process. Studies have demonstrated the presence of microvoids for both silk fibers [21, 22].