A team of architects and chemists from the University of Cambridge in the UK has designed super-stretchy and strong fibers that are almost entirely composed of water, and could be used to make textiles, sensors and other materials. The fibers, which resemble miniature bungee cords and so can absorb large amounts of energy, are sustainable, non-toxic and can be made at room temperature.
Not only does this new method improve upon earlier methods for making synthetic spider silk, as it does not require high energy procedures or extensive use of harmful solvents. But it could also substantially improve methods for making synthetic fibers of all kinds, as other types of synthetic fibers also rely on high-energy, toxic production methods. The results are reported in a paper in Proceedings of the National Academy of Sciences.
Spider silk is one of nature's strongest materials, and scientists have been attempting to mimic its properties for a range of applications, with varying degrees of success. "We have yet to fully recreate the elegance with which spiders spin silk," said co-author Darshil Shah in Cambridge's Department of Architecture.
The fibers designed by the Cambridge team are ‘spun’ from a soupy material called a hydrogel, which is 98% water. The remaining 2% 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 allow long fibers to be pulled from the gel. These fibers comprise extremely thin threads – a few millionths of a meter in diameter. After roughly 30 seconds, the water evaporates, leaving a fiber that is both strong and stretchy.
"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. However, our fibers are non-toxic and far less energy-intensive to make."Darshil Shah, University of Cambridge
"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," said Shah. "However, our fibers are non-toxic and far less energy-intensive to make."
The fibers 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 fibers, you can see a range of different forces holding them together at different scales," said Yuchao Wu, a PhD student in Cambridge's Department of Chemistry, and the paper's lead author. "It's like a hierarchy that results in a complex combination of properties."
The strength of the fibers exceeds that of other synthetic fibers, such as cellulose-based viscose and artificial silks, as well as natural fibers such as human or animal hair.
In addition to their strength, the fibers also show very high damping capacity, meaning they can absorb large amounts of energy, similar to a bungee cord. High damping is one of the special characteristics of spider silk, but there are very few synthetic fibers with this capacity. The researchers found that the damping capacity in some cases even exceeded that of natural silks.
"We think that this method of making fibers could be a sustainable alternative to current manufacturing methods," said Shah. The researchers plan to explore the chemistry of the fibers further, including making yarns and braided fibers.
This story is adapted from material from the University of Cambridge, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.