Research

Published on October 13th, 2016 | by Tina Casey

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Spiderman Would Envy This Graphene-Enhanced Silkworm Thread

October 13th, 2016 by  

Spidey is notoriously close-lipped about the formula of his webbing, and it looks like the folks over at China’s Tsinghua University have a silkworm version of the mystery on their hands. A research team at the school has been doping their silkworms’ meals with graphene and carbon nanotubes to engineer amped-up silk threads that are twice as strong as ordinary silk — and yet, neither the graphene nor the nanotubes show up when the threads are examined.

spiderman-graphene-silkworms

Graphene-Enhanced Silkworms

According to our friends over at Chemical and Engineering News, the idea of modding out silkworm threads at the source is not new:

Researchers have previously added dyes, antimicrobial agents, conductive polymers, and nanoparticles to silk — either by treating spun silk with the additives or, in some cases, by directly feeding the additives to silkworms.

A couple of years ago, a research team at Donghua University also reported good results with silkworms that digested carbon nanotubes.

The new Tsinghua University research fine-tunes that effort by using graphene and smaller, single-walled nanotubes of 1-2 nanometers wide (the Donghua team used 30-nm wide, multi-walled nanotubes).

Here’s the rundown from C&E News:

In contrast to regular silk, the carbon-enhanced silks are twice as tough and can withstand at least 50% higher stress before breaking.

[snip]

The modified silks conduct electricity, unlike regular silk. Raman spectroscopy and electron microscopy imaging showed that the carbon-enhanced silk fibers had a more ordered crystal structure due to the incorporated nanomaterials.

The study, published in the journal Nano Letters, explains the effect of the nano-bits of carbon on the formation of silk:

Spectroscopy study indicated that nanocarbon additions hindered the conformation transition of silk fibroin from random coil and α-helix to β-sheet, which may contribute to increased elongation at break and toughness modules.

The carbon does not show up in the silk. However, it does come out in the silkworms’ excretions, so go figure.

If you would like to DIY this at home, order up some Bombyx mori larval silkworms  and mulberry leaves and have a go at it.

Don’t over-stuff your little charges on carbon, though. To get the silkworms to digest their enhancers, the team used a solution containing no more than 0.2 percent graphene or carbon nanotubes, which they sprayed onto the leaves.

More Graphene News

Meanwhile, a research team over here in the US has come up with a graphene angle that could dovetail with the silkworm study.

Working with Lockheed Martin Space Systems, researchers at Oak Ridge National Laboratory in Tennessee have hit upon a method for controlling defects in graphene and other 2-D materials (for those of you new to the topic, graphene is an atom-thin but super-strong (and weirdly electronic) form of carbon with a structure that resembles chickenwire).

So, imagine if you could feed graphene to silkworms that is precisely engineered to achieve certain desirable effects in silk.

What those might be, we don’t know. If you have an idea, drop us a note in the comment thread.

For now, the Oak Ridge research team is looking at deploying fine-tuned graphene and other 2-D materials for energy storage and water desalination, among other uses. Here’s corresponding author Adri van Duin, cited by Oak Ridge:

As long as you can control defects, you might be able to synthesize in whatever response the graphene will give you. But that does require that you have very good control over defect structure and defect behavior.

As van Duin notes, this is just the first step. The potential for controlling defects in graphene was revealed by a modeling technique that he co-invented, called ReaxFF:

[It] is capable of predicting the interactions of thousands of atoms when they are perturbed by an external force, in this case the bombardment of graphene by atoms of a noble gas.

If you’re wondering what that looks like in graphene, here’s an snippet of an illustration from van Duin’s page at the Penn State College of Engineering:

reaxff-graphene

Here’s the explainer from Penn State:

A simulation shows the path for the collision of a krypton ion (blue) with a defected graphene sheet and subsequent formation of a carbon vacancy (red). Red shades indicate local strain in the graphene.

And, here’s how the folks at Oak Ridge depict it:

graphene-ornl

As for Spiderman’s silk envy, hold on to your hats. Marvel introduced the character Silk into its universe just a couple of years ago, and it looks like she’s already heading for the big screen.

Follow me on Twitter and Google+.

Images: Top by Clara Jordan via flickr.com, creative commons license; middle (cropped) by Kichel Yoon via Penn State College of Engineering; bottom via Oak Ridge National Laboratory.


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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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