Nano Lett. 16, 6695–6700 (2016)

Silkworm silk is popular because it is strong, easy to mass produce and is attractive in textiles. Many of the current methods to enhance the performance of silk through incorporation of metals, conductive polymers and other materials require toxic chemicals and complex procedures. Now, researchers in China show a simple way to produce silk fibres reinforced with carbon nanotubes or graphene.

Yingying Zhang and co-workers at Tsinghua University fed the larvae of Bombyx mori silkworms with mulberry leaves that had been sprayed with different concentrations of either single-walled carbon nanotubes (SWNTs) or graphene. The silk fibres obtained from these silkworms were tougher than control silkworms (as measured by fracture strength and elongation at break). Raman spectroscopy showed that some of the SWNTs were incorporated into the silk fibres while others were excreted. Using infrared spectroscopy, the researchers found that the modified silk contained more α-helix and random coil structures and fewer β-sheets than the control silk. This suggests that the SWNTs and graphene may hinder the transition from α-helices to β-sheets, a process that naturally occurs in the silk-spinning process of silkworms. Furthermore, this compositional difference is thought to contribute to the observed toughness. This feeding strategy offers a scalable approach for the production of tough silk fibres for both research and the textile industry.