Inspired by the ‘liquid wire’ technique in spider webs, scientists have created novel composite fibres which extend like a solid and compress like a liquid. Pulling on a sticky thread in a spider’s web and letting it snap back shows that the thread never sags but always stays taut - even when stretched to many times its original length.
This is because any loose thread is immediately spooled inside the tiny droplets of watery glue that coat and surround the core gossamer fibres of the web’s capture spiral.
“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,” said Fritz Vollrath from the Oxford University in UK.
“Surprisingly, each drop packs enough punch in its watery skins to reel in loose bits of thread. And this winching behaviour 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,” Vollrath said.
The novel properties observed and analysed by the scientists rely on a subtle balance between fibre elasticity and droplet surface tension. The team was also able to recreate this technique in the laboratory using oil droplets on a plastic filament.
This artificial system behaved just like the spider’s natural winch silk, with spools of filament reeling and unreeling inside the oil droplets as the thread extended and contracted.
“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,” said Herve Elettro, a doctoral researcher at the Universite Pierre et Marie Curie in France.
“Our bio-inspired hybrid threads could be manufactured from virtually any components,” Elettro. “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,” he said. The study was published in the journal PNAS.