Natural biopolymers silk fibroin

Biopolymers electrospun from natural materials usually fall into two categories proteins (e.g., collagen, gelatin and silk fibroin) and polysaccharides (e.g., cellulose and its derivatives, chitin/chitosan and hyaluronic acid). 

Another popular crystalline structure for protein is the structure formed by extended protein molecules. A pleated sheet structure is formed by hydrogen bonds between adjacent extended molecules aligned in parallel. Piezoelectricily in B-form protein was first observed by Fukada in 1956 for silk fibroin [3]. Since there is no intrinsic pt -zation in the B structure, pyroelectricity and ten piezoelectricity are not observed. However, the piezoelectricity due to shear is observed. If the shear is applied such as to cause slip between oriented molecules, polarizatioo is induced in the direction perpendicular to the plane of the shear. Shear piezoelectricity is observed for most natural biopolymers, not only keratin but abo trumy other proteins. 

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