It may be the birth of a new supermaterial – not long ago, spider silk materials were considered science fiction. Despite being a bio-material and basically a protein, spider silk has some amazing properties: it is by weight five times stronger than steel and three times tougher than Kevlar. Just so we’re clear, strength is defined as the weight a material can bear, and toughness is the amount of kinetic energy it can absorb without breaking.
A new wonder material
Researchers referenced a scene from “Spider-Man 2” where Spider-Man prevents a train full of people from crashing by holding it back with nothing more than a few sets of spider webs. According to them, that scene may not be entirely fantasy.
“We calculated roughly how thick the fibers were, how many of them he had attached to the walls, how much the locomotive and people weighed, and how fast it appeared to be going,” says Randy Lewis, a professor of biology and biological engineering at Utah State University. “Spider-Man would have been able to stop that train,” says Lewis, a molecular biologist, materials scientist, and chemist who for 25 years has been striving to synthesize spider silk.
There are a myriad of potential applications. The first things that come to mind are cables, bullet-proof vests, parachutes and airbags – but there’s no reason to limit to that; it can help in virtually any area which requires strength and toughness. But spider silk also has antimicrobial properties, and when you take into consideration that silk is not rejected by the human body, the applications in medicine also become evident: wound patches, artificial tendons, you name it. Hold on, things get even better: spider silk has about the same thermal conductivity as copper, but its density is 7 times smaller than that of copper, so it is also an excellent heat management material. All these amazing properties in one single material, one can only wonder why we haven’t been using it yet already?
Obtaining spider silk
Well, it may be a bio-material, and it may be “just” a protein, but it’s extremely hard to obtain. Researchers have tried numerous ways to obtain the valuable substance; for example, in 2010, University of Wyoming biologists mutated genes of silk producing spiders onto goats, so that they will produce the protein only in their milk, from where it can be extracted. The company was called Nexia and the spider silk was copyrighted under the name BioSteel, but after a run that lasted from 1993 to 2005, the company was sold to Pharmatene, and it went bankrupt in 2009. However, today, there are still about 30 spider goats at a university-run farm.
Gathering the protein from spiders is unrealistic – the spiders are extremely territorial, cannibalistic, and typically produce low amounts of silk.
Producing the material remained a challenging in feat, as in recent years, several firms have tried to make spider silk synthetically have copied relevant genes from spiders and inserted them into organisms, such as Escherichia coli, that can express the protein.
Recently, several small companies have reported major progress, and the German firm AMSilk has begun selling spider silk protein – believe it or not, to cosmetics producers, namely producers of shampoos and cosmetics. Although the commercial efforts are still incipient and are arguably not used for any complicated or spectacular products, it’s still remarkable.
AMSilk sell a number of products, including Spidersilk fibers. They are using genetically engineered E. coli to express the protein in a fermentation process. The firm is incorporating four silk varieties into its initial products. The four are derived from the DNA sequence of the European garden cross spider, but AMSilk has engineered specific versions of E.coli to generate about 20 different silk grades at its labs near Munich. Interestingly enough, the company also wants to outsource and scale the production.
“This is scalable technology,” Managing Director Axel H. Leimer says. “If someone ordered 1 ton, we could make it. We have already made a half a ton,” he says. For the first time, a company is producing recombinant spider silk that is as tough and strong as the silk from a spider, Leimer claims.
Lewis and his team are working on making fibers, films, and gels. Lewis says he is talking with producers of sutures, tires, textiles, automobile air bags, and medical implants. He has also been asked if the company could provide a replacement for the Kevlar vests used in sails for the America’s Cup race. It’s definitely a good time to be working in material science. So what do you think, with graphene, and snow spider silk, are we heading towards a new material revolution?
Via C&En.
