If you want to truly understand how something works, you should take it apart and try to put it back together again. That's exactly what scientists from the University of Oxford and Pierre and Marie Curie University did with one of nature's most fascinating materials: Spider silk. In a paper published this week in the Proceedings of the National Academy of Sciences, they report a novel, man-made material that replicates intriguing properties of the stuff spiders use to weave their webs.
It acts as both a solid and a liquid, which is as nuts as it sounds.
When testing the capture spiral of an orb weaver's web, the researchers found that the silk was quite stretchy, which wasn't surprising. But when they slackened the thread, they found that the silk failed to sag in the middle. It just kept adapting to the new length, remaining taut, as if it was shrinking.
By coating a plastic filament with tiny droplets of oil, the researchers were able to create a "liquid wire" that exhibited the same behavior — confirming their hypothesis that it was the interaction between the silk fiber's elasticity and the surface tension of the glue droplets that covered it that made this strange material possible. Instead of sagging, the excess thread is actually looped into the tiny droplets, keeping the overall structure taut. In fact, they were able to replicate the mechanism with pretty much any filament/liquid combo they tried.
"The thousands of tiny droplets of glue that cover the capture spiral of the spider's orb web do much more than make the silk sticky and catch the fly," study author Fritz Vollrath of the Oxford Silk Group said in a statement. "Surprisingly, each drop packs enough punch in its watery skins to reel in loose bits of thread. And this winching behavior is used to excellent effect to keep the threads tight at all times, as we can all observe and test in the webs in our gardens."
These researchers produced liquid wire to confirm their understanding of the mechanism behind spider silk weirdness, but that doesn't mean their artificial version of the stuff won't have applications outside of the lab. After all, spider silk — incredibly thin and strong — is a material that plenty of folks would love to replicate.
"Spider silk has been known to be an extraordinary material for around 40 years, but it continues to amaze us," first author Hervé Elettro said in a statement. "While the web is simply a high-tech trap from the spider's point of view, its properties have a huge amount to offer the worlds of materials, engineering and medicine. Our bio-inspired hybrid threads could be manufactured from virtually any components. These new insights could lead to a wide range of applications, such as microfabrication of complex structures, reversible micro-motors or self-tensioned stretchable systems."