Geckos’ sticky toes inspire engineers
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GECKOS scuttling up walls and across ceilings are a common sight to most South Africans, who probably know that the big-eyed lizards owe this ability to their sticky feet.
What they probably do not know is that this amazing clinging ability of the gecko’s toes has inspired engineers to mimic this in human technology – a practice called biomimicry, technology inspired by nature.
A study published this month by University of Akron researcher Shihao Hu shows that the tiny bristles on geckos’ feet are “self-cleaning”.
The rolling motion by which they attach and detach to and from surfaces causes dirt particles to be released as the creature moves.
This led a partner in Hu’s study, Peter Niewiarowski, to show that a gecko-inspired adhesive can function in conditions where others cannot: in a vacuum, in outer space or under water.
“A gecko-inspired adhesive would be able to bind materials together very strongly, yet also release very easily. Imagine a tape that binds things together securely like duct tape, yet can also be removed and re-used over and over again like a Post-it note,” he said.
Other research published yesterday in the open access journal PLoS ONE shows that geckos did not evolve sticky feet once and keep them. It turns out that geckos have independently evolved sticky feet 11 times, and lost them nine times. Post-doctoral researcher Tony Gamble, of the University of Minnesota, said in a EurekAlert! press release that scientists had long thought adhesive toepads had originated just once in geckos, twice at the most.
“To discover that geckos evolved sticky toepads again and again is amazing,” Gamble said. About 60 percent of the 1 400 gecko species have adhesive toepads. Those that have them can climb smooth surfaces like vertical rocks and boulders to reach food sources such as moths and spiders. The ability also helps them avoid predators.
When habitats changed and sticky feet became a hindrance some geckos lost their sticky feet through natural selection. Their feet work through frictional adhesion and weak intermolecular forces, called Van der Waal forces. Hundreds or even hundreds of thousands of tiny hair-like bristles, called setae, line the underside of a gecko’s toes. The large surface area created by all these bristles generates enough weak intermolecular forces to support the animal.
l The most famous example of biomimicry is Velcro, invented in 1941 by Swiss engineer George di Mestral, who took the idea from burrs that stuck to his dog’s hair.