Artificial superstrong silkworm silk surpasses natural spider silks

Silks are protein-based biopolymers with unique combinations of different physical properties. Silkworm silk is the most well studied due to its abundance and good mechanical behaviors. However, silkworm silk exhibits a weaker strength than the strongest natural silk, spider dragline silk, which is difficult to be produced on a large scale. Here, a facile strategy is developed for spinning superstrong silk fibers in a metal-ion coagulation bath using regenerated silkworm fibroins. The tensile strength of the artificial silk reaches ∼2.0 GPa, more than 70% higher than the average tenacity of dragline silks. It also exhibits an average Young’s modulus of ∼43 GPa, significantly higher than any known natural silks. Structural investigation indicates that the extraordinary strength may be ascribed to high crystallinity and small nano-crystallites formed in the artificial fiber. Incorporation of Zn2+ ions into the fiber during spinning and post-spinning drawing processes may also contribute to its excellent mechanical properties.