First Look

For super-strong silk threads, feed graphene to silkworms

Researchers at Tsinghua University in Beijing fed the one-atom-thick, tremendously tough material to silkworms in one of the first applications of graphene that could become mainstream.

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    The University of Manchester, the home of graphene, explains what the material is and how it was isolated
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Researchers from Tsinghua University in Beijing sparked international interest recently with what may become one of the first large-scale applications of graphene.

Chemist Yingying Zhang and her colleagues fed the tremendously strong yet flexible, carbon allotrope to silkworms by dissolving it in water, then spraying the solution (0.2 percent graphene by weight) on mulberry leaves. The experiment yielded a silk that is twice as tough as ordinary silk and can cope with 50 percent more stress. It also conducts electricity, meaning it could be used to produce wearable electronics.

The double-strength silk is one of the first signs of the graphene revolution that scientists have been hoping for. They say that graphene may someday be used in everything from water purification to energy storage and lightweight planes.

What is graphene? Considered a “wonder material” by some, it is a one-atom-thick material formed of carbon atoms. The atoms are arranged in a hexagonal lattice and linked by covalent bonds, meaning graphene can be stretched a long way before breaking. The material’s website at the University of Manchester describes it as “the world’s first 2D material.” It is transparent and can conduct electricity.

Researchers have been speculating about graphene’s potential since the 1940s. For a long time, however, it was unclear whether graphene could be isolated as a material. Crystalline substances like graphene and diamonds typically grow at high temperatures, and many scientists believed that the heat would prevent graphene from growing as a two-dimensional crystal.

In 2004, Andre Geim and Konstantin Novoselov at the University of Manchester proved that it could be done. The achievement won them the 2010 Nobel Prize in Physics and sparked a wave of research into the applications of graphene.

Graphene “has all the potential to change your life in the same way that plastics did,” Dr. Geim told the Associated Press after the Nobel Prize was announced. “It is really exciting.”

The research with silkworms may become one of the first applications for graphene to go mainstream. Beyond wearable electronics, it could also be used in protective fabrics and biodegradable medical implants.

And other scientists are optimistic that the experiment will scale upward. This work provides an “easy way to produce high-strength silk fibers on a large scale,” Yaopeng Zhang, a materials scientist at Donghua University in Shanghai also working on reinforcing silk, told Chemical and Engineering News. Feeding graphene to the silkworms is far more efficient than treating the silk after it is produced.

How exactly the silkworms process the graphene and incorporate it into their silk remains unclear. It’s also uncertain how much of the graphene they consume is actually being used, which means there could be a way to produce even stronger silk by getting the silkworms to transmit a higher proportion of graphene into the silk. The carbon materials are not visible in the cross sections of the silk threads, Donghua's Dr. Zhang told Chemical and Engineering News, and further investigation of the process may be a task for biologists.

“For many years people have been looking for graphene applications that will make it into mainstream use,” Ravi Silva, a professor and graphene researcher at the University of Surrey, told Newsweek earlier in the year. “We are finally now getting to the point where these applications are going to happen.”

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