The prospects for producing stronger silk fibers like carbon-reinforced silk on a mass basis have brightened.

This follows the success reported by Chinese researchers in producing carbon-reinforced silk by feeding silkworms with mulberry leaves that were dipped in a solution containing the wonder material: graphene.

The tests for making carbon-reinforced silk were conducted by Yingying Zhang and her colleagues at Tsinghua University. They fed single-walled carbon nanotubes and graphene to Bombyx mori larval silkworms.

"We report mechanically enhanced silk directly collected by feeding ... silkworms with single-walled carbon nanotubes and graphene. We found that parts of the fed carbon nanomaterials were incorporated into the as-spun silk fibers," wrote the authors in their research published in the journal Nano Letters.

According to industry experts, the material produced has amazing applications including biodegradable medical implants and wearable electronics.

Silk is already a lustrous clothing material and very tough too. The graphene experiment has proved that there is a smarter way to make the gossamer threads stronger by graphene infusion in the feed.

To test the properties, the team heated the silk fibers at 1,050 °C to carbonize the silk and examined the conductivity. It was found that the modified silks can conduct electricity. Detailed spectroscopy and microscopy imaging showed that the carbon-enhanced silk fibers possessed an ordered crystal structure thanks to the incorporation of nanomaterials.

Pyrolysis of modified silk confirmed a highly developed graphitic structure with higher conductivity of electricity.

Detailed spectroscopy showed the changes. Nano-carbon infusion was seen blocking transition of silk fibroin from a random coil, α-helix to β-sheet. This further facilitated greater elongation.

Impressive Properties

Compared to regular silk, the carbon-reinforced silk had a higher endurance of more than 50 percent for stress and breakage with better conductivity for electricity after heating to a range of 1,050 °C.

Materials scientist Yaopeng Zhang of Donghua University hailed the method as the "easy way to produce high-strength silk fibers on a large scale."

Zhang has been a veteran in the silkworms sector and he also once fed titanium dioxide nanoparticles to make silkworms' threads resistant to ultraviolet degradation. He said carbon-reinforced silk would prove apt for sensors in smart textiles to trace nerve signals.

Some Challenges

While highlighting the potential of carbon-reinforced silk, researcher Zhang pointed to the challenges as well. There is the issue of carbon materials not showing up in the cross sections of the silk threads because of the low volume of the nanoparticle content.

However, there is a consensus that this method is lucrative, unlike treating spun silk in nanomaterials by using toxic chemical solvents. The feeding method is surely simpler and environmentally friendly.

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