Cambridge scientists spin hydrogel into synthetic spider silk
Peter Parker take note, architects and chemists at the University of Cambridge have come up with an artificial spider silk that is strong, super-stretchy, non-toxic and sustainable, yet is made from a material that is 98 percent water. The new artificial fiber is spun from hydrogel at room temperature and is less expensive to produce that current alternatives while possessing many of the properties of real spider silk.
Spider silk had been recognized for centuries as a potential wonder material. Best known as a sticky substance used by spiders to catch prey and fictional superheroes to catch baddies, the various types of silk combine high-tensile strength comparable to high-alloy steel with stretchiness, resilience, and toughness. It can also be spun into very thin threads and can be woven into a fine, smooth cloth with a feel and durability that puts traditional worm silk to shame.
The problem is that spider silk as it comes out of the spider is so difficult to obtain in quantity that it isn't used for much beyond making cross hairs in telescopes and rifle sights. Unlike silkworms, spiders are notorious cannibals, so they can't be farmed. The silk itself is a mind-bogglingly complex structure of various proteins mixed with sugars and lipids, and duplicating it in a laboratory is extremely difficult.
Various attempts have been made to create fibers that mimic spider silk, but these often involve high temperatures and toxic solvents. The Cambridge team's approach is to start with hydrogel, which is a substance made of 98 percent water that is bound together by molecular handcuffs, called cucurbiturils, consisting of silica and cellulose.
Due to the way the compounds that make up the hydrogel interact, it's possible to pull very long supramolecular polymer fibers from the gel that self-assemble at room temperature as the molecules bond together by sharing electrons.
According to the team, within 30 seconds of being spun, the water evaporates from the fibers only a few millionths of a meter in diameter that become strong and stretchy with a complex range of properties similar to those of real spider silk. For example, the hydrogel silk has a similar very high damping capacity, which means it can absorb large amounts of energy by stretching like a bungee cord. In fact, its capacity even exceeds that of some natural silks.
The team believes that this method could not only useful for manufacturing textiles, sensors and other materials, but could also be used to create other synthetic fibers that currently rely on toxic, high-energy processes.
"Although our fibers are not as strong as the strongest spider silks, they can support stresses in the range of 100 to 150 megapascals, which is similar to other synthetic and natural silks," says Darshil Shah from Cambridge's Department of Architecture. "However, our fibers are non-toxic and far less energy-intensive to make."
The research was published in the Proceedings of the National Academy of Sciences.
The video below shows the new silk undergoing a stress test.
Source: University of Cambridge