Low-loss light-guiding, strong silk generated by a bioinspired microfluidic chip

The necessity of optical waveguides with low-loss light guiding of biomedical devices is driving increasing demands for development of biocompatible photonic components. Spider silks have extraordinary mechanical properties; thus, the design of high-performance artificial silk fibers as optical waveguides for low-loss light guiding has been one of the focuses of researches in the field of biomimetic fibers. In this study, regenerated silk fibroin (RSF)/cellulose nanofibers (CNF) hybrid fibers were wet-spun through a microfluidic channel that mimics the shape of spider's major ampullate gland. The generated RSF/CNF fibers with high crystallinity, high mesophase content and small crystallite size, thus showed a low light loss of 1.0 dB/cm, which was much lower than that of degummed-silk and most commercial waveguides. Additionally, the fibers had high sound velocity and was knittable. The break strength of the RSF/CNF fiber containing 5 wt% CNF was as high as 710 ± 33 MPa, which was significantly higher than that of silkworm silk fiber. The developed optical waveguides had high performance, biocompatibility, biodegradability, flexibility, and toughness, thus may be suitably applied in biological media, biophotonics and brain-machine interfaces.