They initially looked at spider silk (as it is known to be 10 times tougher than Kevlar) but soon reached the conclusion that it would be too expensive and difficult. Instead, they turned to silk from silkworms, produced for thousands of years through sericulture. But while it is much easier to produce, it is not as tough as spider silk. To improve this, they added graphene.
The team decided to set up a company - Synbiosys - to explore this idea further, and received project funding from The Defence Science and Security Accelerator (DASA). The project has so far focused on successfully combining the two materials into a composite. “Incorporating carbon nanostructures, like graphene, into silk has been attempted before, but not effectively.” explained the team. “One research group tried spraying carbon nanotubes onto mulberry leaves, before feeding them to silkworms, and another research group sprayed graphene flakes directly onto spiders.”
The Imperial College team instead focused on applying the graphene to the silk, rather than the animal, and showed this technique can be used to make thin, composite films. They then tested the film by shooting it with tiny pieces of metal, using a special laboratory device, and measuring the effect of the impact.
The tests showed that adding the graphene increased the strength of the composite - the amount of force required to stretch the material - compared to the silk on its own. Strength is important as stronger materials will stop faster bullets, and this test validated their idea of graphene increasing the strength of silk. “It’s a good start, and we are already seeing improvements on our original designs.” said the researchers.
The silk-graphene composite is transparent and lightweight, properties that make the material suitable for applications beyond body armor. The team are working to expand on this, and have already seen interest from manufacturers of bullet-resistant glass.