Cambridge scientists, including one of Indian origin, have developed super-stretchy and strong artificial spider silk, composed almost entirely of water, which may be used to make eco-friendly textiles and sensors. The fibres, which resemble miniature bungee cords as they can absorb large amounts of energy, are sustainable, non-toxic and can be made at room temperature, researchers said. The fibres are spun from a soupy material called a hydrogel, which is 98 per cent water. The remaining 2 per cent of the hydrogel is made of silica and cellulose, both naturally available materials, held together in a network by barrel-shaped molecular "handcuffs" known as cucurbiturils. The chemical interactions between the different components enable long fibres to be pulled from the gel, said researchers from University of Cambridge in the UK. The fibres are pulled from the hydrogel, forming long, extremely thin threads - a few millionths of a metre in diameter.
After roughly 30 seconds, the water evaporates, leaving a fibre which is both strong and stretchy. "Although our fibres 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. However, our fibres are non-toxic and far less energy-intensive to make," said Darshil Shah, from Cambridge. The fibres are capable of self-assembly at room temperature, and are held together by supramolecular host- guest chemistry, which relies on forces other than covalent bonds, where atoms share electrons. "When you look at these fibres, you can see a range of different forces holding them together at different scales. It's like a hierarchy that results in a complex combination of properties," said Yuchao Wu, a PhD student at Cambridge. The strength of the fibres exceeds that of other synthetic fibres, such as cellulose-based viscose and artificial silks, as well as natural fibres such as human or animal hair. In addition to its strength, the fibres also show very high damping capacity, meaning that they can absorb large amounts of energy, similar to a bungee cord. There are very few synthetic fibres which have this capacity, but high damping is one of the special characteristics of spider silk. Researchers found that the damping capacity in some cases even exceeded that of natural silks. "We think that this method of making fibres could be a sustainable alternative to current manufacturing methods," said Shah. The study was published in the journal Proceedings of the National Academy of Sciences.