With a little help from a South African gecko, a University of Calgary professor has shed light on how these tiny lizards get themselves both into and out of sticky situations.
Geckos have long fascinated biologists with their mysterious ability to attach to nearly any surface without the use of a sticky secretion. However, for Dr. Anthony Russell, a gekkotan adhesion expert, it was not the attaching but the detaching that first drew his attention.
"Sticking to a surface is not difficult." said Russell. "Getting something off the surface and not damaging it is difficult. So what geckos have is this sort of magical mechanism that can be created or destroyed without damage to the material."
Together with graduate student Megan Johnson, Russell sought to clarify how geckos make contact with such a wide variety of surfaces. Their findings were recently published in the Dec. '07 issue of the Canadian Journal of Zoology.
"Geckos have a huge amount of bristles on their fingers and toes that make contact with the surface." explained Russell. "They create a sort of electrostatic type bond but also frictional interaction. It's a reversible system so if you pull in one direction, the bond sticks. If you push in the other direction, it comes off."
A single gecko toe may contain over a million of these bristles, each measuring about one micron in length, Russell noted. The abundance of these bristles lends geckos two to three thousand times the adhesive strength normally required to hold them ups.
"We asked ourselves, 'how come nature has produced something that is a thousand times more sticky than it needs to be?'" said Russell. "What are these animals really doing in nature as opposed to what we can make them do in the lab?"
To answer these questions, Russell and Johnson looked to a species of diurnal--or daytime active--gecko inhabiting rocky regions of Namibia. Using electron microscopy, the research team created a 3D topographical map of the gecko's contact surfaces.
"What we were looking at was how much of the rocky surface would be available for the geckos to attach to." Johnson said.
Russel explained the amount of surface area the gecko uses to stick to surfaces is only one per cent of the total "equipment" they have.
"Their toes are built in such a way that anytime they put their foot down, they'll make enough contact to support them but it will be very little of the total capabilities that they have," said Russel.
Russell's findings add to the growing body of research conducted since the discovery of the lizards' adhesive abilities in 2000. What has since developed is a heated race to adapt gekkotan technology for use in the military, robotics and other possible human applications.
However, Russell's next step will be to answer a few lingering questions.
"What we've done is reported on only one species," he said. "I want to see how closely related species in the same [location] have adjusted their adhesive structure to suit the particular rock types that they're moving on. Is the gecko system microengineered to particular types of surface? Or is it one-size-fits all?"