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Scientists Created a Synthetic Muscle Fiber That's Stronger Than Kevlar

And it's made with tiny microbes.

A new synthetic fiber made from muscle has just been developed that appears to be tougher than Kevlar. Created by researchers at the McKelvey School of Engineering at Washington University in St. Louis, the muscle fibers are created by specially designed microbes, rather than being derived from living tissue sources. 

Their research findings were first published on August 30 in the Journal Nature Communications.

These new fibers could conceivably be woven in a very strong fabric that could be used for many applications from shoelaces to belts or even whole items of clothing. Such fibers should say the researchers behind the development, be able to endure more rough and tumble before failing than more traditional materials like cotton, silk, nylon, or, even, kevlar. 

Not only that, but once scaled up, the fiber production should be relatively cheap. 

“Its production can be cheap and scalable. It may enable many applications that people had previously thought about, but with natural muscle fibers,” said Fuzhong Zhang, professor in the Department of Energy, Environmental & Chemical Engineering.

The fibers are made using specially engineered bacteria

The fibers are made from a substance called titin, which is one of the three main protein components in muscle. Titin is a relatively large molecule which is the key to its mechanical properties.

In fact, it is, as far as we know, the largest known protein in nature. 

Finding ways to synthesize protein fibers like titan have been the subject of keen interest for years. For example, research teams have been investigating developing materials similar to muscle to build things like soft robots.

“We wondered, ‘Why don’t we just directly make synthetic muscles?’” Zhang said. “But we’re not going to harvest them from animals — we’ll use microbes to do it.”

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The fibers could also make long-lasting shoelaces or belts. Source: sand dragon/Flickr

However, this approach has historically proven to be very difficult as microbes, specifically bacteria, tend to not really be coaxed into making such large protein structures. To get around this, Zhang and his team specially engineered bacteria to piece together small segments of the protein into ultra-high molecular weight polymers around two megadaltons in size — about 50 times the size of an average bacterial protein.

Post-bacteria-production, the proteins were then wet-spun to convert them into fibers that were around 10 microns in diameter, or a tenth the thickness of human hair.

Once created, the team then collaborated with other researchers to test the strength and durability of the new fibers. The results were very surprising indeed. 

Working with Young-Shin Jun, professor in the Department of Energy, Environmental & Chemical Engineering, and Sinan Keten, professor in the Department of Mechanical Engineering at Northwestern University, the new fibers were shown to be potentially stronger than kevlar -- under certain circumstances. 

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They were so strong that the team quickly realized that they could easily be used to make special clothing or even protective armor. Not only that, but they may have potential applications in biomedicine too. 

For example, being made from a common protein in nature, it is not inconceivable that the fibers could be used for suturing of wounds, tissue engineering, or other applications. After all, they should be biocompatible in most circumstances. 

The research team doesn’t plan on stopping there. It is hoped that the future will likely hold more unique materials enabled by their microbial synthesis strategy. They are so confident with their findings that the team has recently filed for a patent based on their research. 

“The beauty of the system is that it’s really a platform that can be applied anywhere,” says Cameron Sargent, a Ph.D. student in the Division of Biological and Biomedical Sciences and a first author on the paper along with Christopher Bowen, a recent Ph.D. graduate of the Department of Energy, Environmental & Chemical Engineering.

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We can take proteins from different natural contexts, then put them into this platform for polymerization and create larger, longer proteins for various material applications with greater sustainability,” he added.

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