This study is led by Dr. Yingying Zhang (Department of Chemistry, Tsinghua University). The team devised a scheme utilizing silkworms to produce highly strong and tough silk through feeding them with rare earth ion-modified diets. The rare earth ions can be incorporated into silk fibroin through feeding. And the incorporated ions are capable of forming ion-dipole and cation-π interactions with silk fibroin (see below). These interactions are promising to tune the structures of silk to enhance its mechanical performance.
Spectra analysis confirmed the successful incorporation of rare earth ions into silk fibers, and their chemical interactions. Morphological and structural analysis demonstrated that rare earth ions reduced the diameter of silkworm silk fibers, increased the amorphous component content and crystalline orientation.
These chemical interactions and structural evolutions contributed to the mechanical improvement of silk fibers. The average values for tensile strength, Young's modulus, and toughness reached 0.85 ± 0.07 GPa, 18.0 ± 1.5 GPa, and 156 ± 13 MJ m−3, respectively, and maximum values reached 0.97 ± 0.04 GPa, 19.0 ± 1.5 GPa, and 188 ± 19 MJ m−3. The comprehensive mechanical performance of this silk is comparable to spider dragline silk, and superior to that of silk modified by other functional materials (see below).
This work provides a simple, efficient, and scalable strategy to prepare super strong and tough silkworm silk fibers. And the as-obtained silk fiber are potential candidates for individual sports, medical treatment, and aerospace.
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Highly strong and tough silk by feeding silkworms with rare earth ion-modified diets