In Situ Mineralizing Spinning of Strong and Tough Silk Fibers for Optical Waveguides

Biopolymer-based optical waveguides with low-loss light guiding performance and good biocompatibility are highly desired for applications in biomedical photonic devices. Herein, we report the preparation of silk optical fiber waveguides through bioinspired in situ mineralizing spinning, which possess excellent mechanical properties and low light loss. Natural silk fibroin was used as the main precursor for the wet spinning of the regenerated silk fibroin (RSF) fibers. Calcium carbonate nanocrystals (CaCO3 NCs) were in situ grown in the RSF network and served as nucleation templates for mineralization during the spinning, leading to the formation of strong and tough fibers. CaCO3 NCs can guide the structure transformation of silk fibroin from random coils to beta-sheets, contributing to enhanced mechanical properties. The tensile strength and toughness of the obtained fibers are up to 0.83 +/- 0.15 GPa and 181.98 +/- 52.42 MJ center dot m-3, obviously higher than those of natural silkworm silks and even comparable to spider silks. We further investigated the performance of the fibers as optical waveguides and observed a low light loss of 0.46 dB center dot cm-1, which is much lower than natural silk fibers. We believed that these silk-based fibers with excellent mechanical and light propagation properties are promising for applications in biomedical light imaging and therapy.

Automated summary

Biopolymer-based optical waveguides with excellent mechanical properties and low light loss were prepared through bioinspired in situ mineralizing spinning using silk fibroin as the main precursor. Calcium carbonate nanocrystals were grown in the silk network during spinning, resulting in strong and tough fibers with enhanced mechanical properties. The fibers exhibited low light loss and are promising for applications in biomedical light imaging and therapy.