What do geckos, glue have in common?

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iol scitech june 28 gecko REUTERS 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.

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 Th – a practice called biomimicry, technology which has been 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 Peter Niewiarowski, a partner in Hu’s study, to show that a gecko-inspired adhesive that can function under 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 reused 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 as a once-off development.

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 toe pads had originated just once in geckos, twice at the most.

“To discover that geckos evolved sticky toe pads again and again is amazing,” Gamble said.

About 60 percent of the 1 400 gecko species have adhesive toe pads. Those that have them can climb smooth surfaces such as vertical rocks and boulders to reach food sources, such as moths and spiders. This unique ability also helps them avoid predators.

When habitats changed, and sticky feet became a hindrance – for instance, in sand dunes – some geckos lost their sticky feet through natural selection.

Their feet work through a combination of 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 whole 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 had become stuck to his dog’s fur. - Pretoria News

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