Scientists create novel liquid wire material inspired by spiders' capture silk
Date: 18.5.2016
Why doesn't a spider's web sag in the wind or catapult flies back out like a trampoline? The answer, according to new research by an international team of scientists, lies in the physics behind a 'hybrid' material produced by spiders for their webs.
Pulling on a sticky thread in a garden spider's orb web and letting it snap back reveals 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.
This phenomenon is described in the journal PNAS by scientists from the University of Oxford, UK and the Université Pierre et Marie Curie, Paris, France.
The researchers studied the details of this 'liquid wire' technique in spiders' webs and used it to create composite fibres in the laboratory which, just like the spider's capture silk, extend like a solid and compress like a liquid. These novel insights may lead to new bio-inspired technology.
Professor Fritz Vollrath of the Oxford Silk Group in the Department of Zoology at Oxford University said: '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. 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.'
The novel properties observed and analysed by the scientists rely on a subtle balance between fibre elasticity and droplet surface tension. Importantly, the team was also able to recreate this technique in the laboratory using oil droplets on a plastic filament. And 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.
