Nanocellulose reinforced silkworm silk fibers for application to biodegradable polymers

In addition to its use in the conventional textile industry, Bombyx Mori silk has attracted significant attention in the materials science and biomedical engineering disciplines. Recently, the possibility of drawing silk fibers with superior toughness has gained particular research interest. Cellulose nanofiber (CNF) is widely studied as a reinforcement material owing to its excellent mechanical properties combined with relatively low density and promising biocompatibility. This paper reports silkworm silk fibers dispersed with CNF that present outstanding tensile properties compared with conventional silk fibers. The silkworm diet was modified by including CNFs, and tensile tests were carried out for the drawn silk fibers. Tensile testing of the drawn silk showed improved Young's modulus and tensile strength when the diet included CNFs at 5 wt% concentration. Fourier transform infrared spectroscopy and atomic force microscopy studies were also conducted to determine the reason for the observed improvement in properties. Morphological studies revealed that the individual fibrils or fibril bundles are aligned in the longitudinal direction of the silk fibers and are uniformly dispersed. Moreover, finite element analysis was performed to estimate the volume fraction of CNF in the silkworm silk fiber. This work opens the door for development of renewable and sustainable bio-composites.