Highly strong and tough silk by feeding silkworms with rare earth ion-modified diets

Abstract

Nature-derived silk fibers possess excellent biocompatibility, sustainability, and mechanical properties, yet producing strong and tough silk fibers in a facile and large-scale manner remains a significant challenge. Herein, we report a simple method for preparing strong and tough silk fibers by feeding silkworms rare earth ion-modified diets. The resulting silk fibers exhibit significantly increased tensile strength and toughness, with average values of 0.85 ± 0.07 GPa and 156 ± 13 MJ m^-3, respectively, and maximum values of 0.97 ± 0.04 GPa and 188 ± 19 MJ m^-3, approaching those of spider dragline silk. Our findings suggest that the incorporation of rare earth ions (La³⁺ or Eu³⁺) into the silk fibers contributes to this enhancement. Structure analysis reveals a reduction in content and an improvement in orientation of β-sheet nanocrystals in silk fibers. X-ray photoelectron spectroscopy analysis confirms the chemical interaction between rare earth ions with β-sheet nanocrystals. The structural evolution and chemical interactions lead to the simultaneous enhancement in both strength and toughness. This work presents a simple, scalable, and effective strategy for producing ultra-strong and tough silk fibers with potential applications in areas requiring super structural materials, such as personal protection and aerospace.

Keywords: High orientation; Low crystallinity; Rare earth ions; Silkworm silk; Super strong and tough.