Silkworms spin super-strong silk after eating carbon nanomaterials

After researchers at Tsinghua University fed silkworms graphene or single-walled carbon nanotubes, the "silk" they spun was stronger and tougher. According to a report on the website of Scientific American magazine on the 10th, this carbon-reinforced silk can be used in durable protective fabrics, biodegradable medical implants and eco-friendly wearable electronic devices.

To make carbon-reinforced silk, Zhang Yingying of Tsinghua University and her colleagues directly sprayed an aqueous solution containing carbon nanotubes or graphene (0.2% of total weight) onto the mulberry leaves eaten by silkworm larvae, and then collected the silk after the larvae spun cocoons.

The report said that this direct feeding of a carbon-containing aqueous solution is simpler and more environmentally friendly than directly treating silk that has already been spun into cocoons. More importantly, the carbon-reinforced silk doubled in toughness against external destructive forces and withstood at least 50% more stress. The research team heated this silk to 1050°C and further studied the electrical conductivity and structure of the carbonized silk protein fibers. Raman spectroscopy and electron microscope imaging showed that the crystal structure of the carbon-reinforced silk incorporated with nanomaterials was arranged in a more orderly manner.

Shen Qing, a polymer chemist at Donghua University in Shanghai, who in 2014 used 30-nanometer multi-walled carbon nanotubes to create a new type of silk fiber, believes that the 1-2 nanometer single-walled carbon nanotube material used by Zhang Yingying's team is "more suitable for incorporating into the crystal structure of silk protein."

Zhang Yaopeng, a materials scientist who once produced silk resistant to ultraviolet degradation by feeding silkworm larvae nano titanium dioxide, said that the Tsinghua team "provided a simple method for large-scale production of high-strength silk fibers, and its excellent electrical conductivity makes it more suitable for use in embedded smart textiles and sensors that can read neural signals." (Reporter Fang Linlin)