Spiders sprayed with graphene - carbon sheets just one atom thick - have spun silk containing the material to create webs that proved more than three times stronger than those made of natural spider silk, researchers report.
Combining graphene particles and carbon nanotubes with water and then spraying the resulting solution on 15 common spiders from the Pholcidae family had startling effects on the silk they then wove, scientists at the University of Trento in Italy found.
While some of the spiders produced silk of reduced strength, a significant number of them produced a form of "super silk," the researchers report in the journal Materials Science.
"We find that the resulting silk has improved mechanical properties," writes study leader Nicola Pugno, a professor of solid and structural mechanics.
Normal spider silk is stronger than almost any man-made fiber, and the carbon-infused "super silk" is stronger still.
The researchers collected the silk spun by the spiders sprayed with graphene and nanotubes and placed strands of it in a device that measured the loads it could withstand.
What they found was "the highest toughness modulus for a fiber, surpassing synthetic polymeric high-performance fibers (e.g., Kelvar49) and even the current toughest knotted fibers," they report.
Exactly how the spiders are managing to incorporate graphene or carbon nanotubes into their silk isn't clear, they say. The team use spectroscopic methods to show that the carbon-based materials are present in the fiber but are unable to show exactly how.
If the silk is simply being coated on its outside with the carbon-based material the resulting structure would not have the strength measured, they note.
"Such external coating on the fiber surface is not expected to significantly contribute to the observed mechanical strengthening," they say.
It's more likely the spiders are ingesting both the carbon materials and the water it is applied with and incorporating both into their silk as they spin it so the carbon material ends up in the core of the fibers.
This would have the greatest impact on its strength, they say.
Possible uses for such a material would present challenges, the researchers acknowledge; for instance, there has never been a successful and efficient method for harvesting spider silk.
Still, the potential uses for any material based on graphene have designers pursuing applications for building materials, batteries and fabrics. The research was published in a paper "Silk reinforced with graphene or carbon nanotubes spun by spiders."
And because the technique is so simple, the researchers suggest a similar approach could be used on other organisms. "This new reinforcing procedure could also be applied to other animals and plants, leading to a new class of bionic materials," they say.
