Graphene, atom-thick sheets of carbon, has incredible conduction and strength properties. Carbon nanotubes, tubes created from carbon atoms at the billionth-of-a-meter scale, astound engineers in much the same way. These synthetic materials and those like them are starting to get a one-up on anything nature can produce, even something like spider silk. But what if you combine the two?
Last month, a team of Italian scientists sprayed 15 silk-slinging spiders down with water/carbon nanotube and water/graphene mixes to see if the super-materials could infiltrate the silk. They did. Some spiders had a 3.5x increase in the strength of their silk, the team reported in arXiv. The spider that saw this improvement was a giant Darwin’s bark spider, which are capable of creating webs spanning whole rivers. It was sprayed down with the carbon nanotube mix.
Not all of the spiders saw strength increases. Some of the arachnids produced silk that was worse than their own brew, and four of the tested spiders died shortly after being sprayed. This suggests that the strength increases and decreases in the spiders’ silk came not from the graphene or nanotubes coating the outside of the silk, but from being incorporated into the silk itself after somehow entering the spiders.
A) Spider selection. B) Spider capture into individual boxes. C) Single-wall carbon nanotube spraying. D) Graphene spraying. E) Collection of silk after 2-12 days. F) Silk cut and placed for testing. G) Silk placed in tension (pulling) test. H) Testing. I) Silk under scanning electron microscope.
Though the researchers aren’t sure how the materials were incorporated into the silk, how the silk could increase in strength and toughness is better understood. Composite materials, or materials crafted to have properties distinct from the materials that create it, typically consist of two or more synthetic materials that shore up each others’ weaknesses. For example, concrete can withstand an amazing amount of compression but very little tension, which is why metal rebar is inserted to add additional strength.
The spider silk in this study may be getting stronger in the same way. Incredibly strong carbon nanotubes embedded in already strong silk, even in the “wrong” orientation, could feasibly act like rebar in concrete and give the silk additional strength and toughness.
This isn’t the first time Nicola Pugno and his team have found a super-material either. Last February Pugno reported that the only natural material stronger than spider silk was the teeth of the little limpet.
But the real question given this new research is whether or not Spider-Man could use it to his advantage. Probably. Peter was a smart kid with access to some pretty advanced science. If he could get his hands on a way to cheaply produce carbon nanotubes, he could mix it into his web shooter formula and hope for the best (or drink billions of them and hope for the best, if the web is organic like the first movies). What’s the worst that could happen? Oh, right…
IMAGE: Emiliano Lepore, et al.