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October 17th, 2016 at 7:15 am

The future of wearables: Silkworms fed graphene produce ‘super silk’

Graphene just keeps getting better and better. The so-called super material – a one-atom-thick layer of carbon that has proven to be incredibly strong, flexible, light and conductive – has now been fed to larval silkworms which then created “mechanically enhanced silk”.

The find could have huge implications for the future of wearables, considering the conductive material could be weaved into textiles, and our clothing embedded with technology. We would no longer have to wear devices that are so often bulky and conspicuous but would have individualised garments concealing the tech.

Silk is already pretty strong, and also one of the most desirable fabrics in the world, so it was the obvious choice for the experiment carried out by a team from Tsinghua University. They fed the silkworms mulberry leaves coated in a solution made up with 0.2 per cent of carbon nanotubes or graphene, reports the Scientific American.


They then let the worms make their cocoons and collected the silk once it was completed. The team found carbon nanomaterials in both the silk, and the worm’s excrement – suggesting more work needs to be done to find out how much carbon the worms need to be fed to get the optimum silk since not all of it is being transferred to the resulting product. The approach was chosen over coating already made silk with carbon, because this would also involve the introduction of chemicals.

The resulting silk was twice as strong, could cope with 50 per cent more stress before degrading, and after being heated at temperatures of up to 1,050°C was shown to be conductive. The latter means the silk could be a viable option for smart textiles, but also for medical devices embedded in the body.

WIRED spoke to Juan Hinestroza, who heads up Cornell University’s Textile Nanotechnology Laboratory, back in 2013 when the wearables resurgence was kicking off, and he described exactly the kinds of wearable technology this new material could bring to life.

Designs coming out of the lab, which is made up of chemical and biological engineers, fibre scientists, physicists, and designers, included a solar-powered dress that used conductive cotton to charge smartphones, and a nanoparticle-coated outfit that changed colour when light and matter was manipulated in the spaces between those particles. They use nanoparticles to engineer natural fabrics to be conductive, bacteria-resistant and to filter toxic gases.

“The idea is to have these technologies embedded into existing material, so we won’t need to build multimillion dollar factories,” Hinestroza told us. “We’re also developing transistors made of cotton so the electronics will not be attached to the textile – the textile will be the electronic device.”

To embed graphene, with all its incredible properties, into silk, is to bring two of the most desirable products from the world of fashion and science together – something a lab like Cornell’s has been aiming to do with its diverse mix of research disciplines.

Importantly, the team behind this latest silkworm research (published in Nano Letters) claim the technique of feeding graphene to the silkworms “is expected to open up possibilities for the large-scale production of high-strength silk fibres”.

Mass production has been the stumbling block for graphene. It has been used in the lab to create spider silk that could “catch a falling plane” and flexible electronic screens (a precursor of the promised e-paper). Research is underway to 3D print ”super batteries” from graphene ink, engineer the strongest condoms in the world using it, and a team at Nankai University in China wants to build a solar-powered spacecraft from it that flies on starlight.

But none of this will ever be possible unless engineers can find a way to scale up production of the material in a way that maintains its properties and keeps costs low. If you stack sheets of graphene together, it has been shown to ”diminish most of those properties including electronic, photonic and even mechanical aspects”.

In 2014, Samsung released news of a method it believes will help overcome these issues. By repeatedly synthesising single crystals of the substance, it could grow a large area of graphene. This is as opposed to the multi-crystal synthesis that had been trialled in the past. The tech giant called it a “groundbreaking method” that could lead to commercialisation. There have also been other variations of potential mass production techniques that create large sheets of the substance.

However we are very likely to miss predictions made in 2012 that we would be rolling up our e-paper by 2015 – the science has been demonstrated, but we are not close to having this kind of use mass produced.

It’s important to remember that, although we are all keen to have Spider-Man-style capabilities thanks to the material, it was only invented in 2004 by a team at University of Manchester. The substance has proven to be so immensely tough, it can turn spider silk into a net so strong it could catch a falling plane.

It has been proposed as a possible spacecraft shield after experiments where microscopic projectiles fired at it at speeds faster than a bullet from an AK-47 were rapidly slowed down. In short, it’s a ridiculous material that keeps surprising us and we will have to be a little patient for that mass production.

Image credit: Oksana Sufrich/iStock
Article via: Wired


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