The Gecko Grip

In warmer climates lives a small creature that has amazed and bewildered human observers for thousands of years, even inspiring engineers at NASA. Let's take a look at the "Gecko."

The Gecko's most amazing characteristic is its ability to walk effortlessly on vertical or even overhead surfaces, despite the fact that its feet are not sticky nor do they possess any form of suction cups.

Consider also that a gecko can move at a rate of 20 body lengths per second. Meaning that the gecko's foot must somehow adhere to the surface, and yet be released just as quickly as it initially stuck to that surface. This is quite a unique characteristic which man has yet to replicate as the Oxford Journals reports: "...repeated and rapid detachment without significant detachment forces is beyond the capability of any current synthetic adhesive" (Mechanisms of Adhesion in Geckos, Oxford Journals, Vol 42, Issue 6, p 1082). So how does the gecko do it?

It appears the secret of gecko movement is in the design of its foot. The five toes on each gecko foot are covered with several rows of microscopic bundles of "hairs" called setae. Each of these bundles can split into hundreds of very tiny endings called septulae. It has been learned that the length and design of these hair-like structures enables each of them to create an electrostatic force (known as van der Waals force), which develops as soon as the toes touch a surface.

A gecko weighs approximately 50 g (2 oz.), yet the average gecko would require up to 286 pounds of force to be dislodged, if fully attached with all four feet (Robson, D., "Gecko's gravity-defying trick explained", New Scientist Live, June 2007).

But why does the gecko not become stuck in a position, given that the force developed is so strong? When the angle of the septulae is at 30 degrees, the force appears to be at a maximum. As the gecko moves the foot forward the angle increases and the force rapidly grows weaker, allowing for quick movement. It even works on Teflon.

Oregon State University engineer, P. Alex Greaney, puts it this way: "These are really fascinating nanoscale systems and forces at work... "(Rachel Feltman, "New Research Investigates the Physics of Sticky Gecko Feet", Washington Post, Aug 12, 2014). Kellar Autumn, a biologist at Lewis and Clarke College in Oregon, in observing this phenomenon stated: "Geckos are vastly over-engineered." This is due to the fact that a 50-gram gecko need only use 3% of its setae to be secure as it climbs.

The Gecko's power of adhesion is far superior to anything man has been able to design. Thus British Aerospace and NASA, are now working to perfect synthetic gecko grippers. They hope to be able to use them to enable robotic spacecraft to grab space debris; for high-end braking systems, and closing wounds without stiches.

Thus equipped, these superheroes of the lizard world more than rival the fictional Spiderman.

Geckos are one of many Small but fantastically complex life forms which stand as reminders of the obvious engineering that has been built into the fabric of life.

I am Stuart Wachowicz for Tomorrow's World Viewpoint.

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