Two papers on spider silk have coincidentally come out within a week. One announced an environmentally friendly way to replicate its remarkable features, while the other reveals one of its secrets. Together, the research could take us into a world of stronger, lighter, and more flexible wires with a multitude of uses.
The capacity of spider silk to capture prey and transport the spiders remarkable places has been celebrated in legend and popular culture. Until recently, it was something of a mystery to scientists. Although efforts have been made to replicate the remarkable combination of properties of this material, they have been expensive, consumed plenty of energy, and produced toxic by-products.
In the Proceedings of the National Academy of Sciences, Cambridge University chemists and architects announce a hydrogel whose polymers are cross-linked to provide great strength, while also having spaces that keep it light. The product, they claim, “exhibits better tensile and damping properties than conventional regenerated fibers, such as viscose, artificial silks, and hair.” Best of all, it can be spun at room temperature, a feat spiders developed tens of millions of years ago, but we have struggled to match.
The team created a hydrogel, which as its name suggests is mostly water – 98 percent in fact. The rest is silica and cellulose, widely available from rocks and plants respectively. When fibers are drawn from the hydrogel, they form threads just a few microns across – much thinner than human hairs. The water evaporates slowly when in a container, but disappears within 30 seconds from the thin strands, leaving the strong but stretchy fiber behind.
“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,” co-author Dr Darshil Shah said in a statement. “However, our fibers are non-toxic and far less energy-intensive to make.”
Shah admits the team has yet to produce something as good as real spider silk, but he regards what has been produced as suitable for cases where strength to weight ratios are important, such as climbing ropes or aerospace.