ZOO-ology column: Geckos have terrific toes
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By Judie Farnsworth
Did you know you have celebrities dining right outside your doors at night?
Their name may be bantered about in discussions of intermolecular forces, atoms, nanoparticles and impressive scientific jargon. They gather near porch lights at night. They cling to almost any surface, even by only one or two toes. Yep - they're unassuming little geckos - in our area, most commonly, the Mediterranean gecko.
They're busy gobbling large numbers of small roaches and other pests. Pest control aside, their agility has been the subject of scientific speculation since the 1800s - all because of their terrific toes.
How do they hold to surfaces with dry feet? Geckos don't have glands on their feet to produce any gummy liquid. How can they support eight times their weight hanging from polished glass with just one toe? Why can their feet stay clean without washing? And, why should we care?
The dry adhesion seen in gecko's feet has the potential for exciting applications if it can be fabricated.
In the 1950s, years of speculation were put to rest with the development of electron microscopy. As imagery sophistication continued to grow and with much research, the secrets of those terrific toes really came to light in 2002.
The footpads of geckos have a series of ridges, covered with millions of hair-like structures called setae (from the Latin, bristle). Each seta separates into a thousand split ends with flat tips called spatulae (because of their shape). The ability to navigate slick surfaces is credited to the huge volumes of setae and spatulae and the weak pull molecules have for one another when they meet (van der Waals force).
Let's just say that gecko feet have tremendously strong, dry adhesive ability. If a typical mature 2.5-ounce gecko had every one of its setae in contact with a surface, it would be capable of holding up a weight of 290 pounds, according to Wikipedia.
Gecko feet self-clean. Dust, sand, pollen - not a problem. It's all pushed out as they move around. Gecko toes bend and peel up in the opposite direction from ours. The setae adhere well in one direction and pull off easily in another without slowing the gecko. Other lizards and some insects have similar abilities, but the humble gecko outshines them all.
So, just what can all this mean for us? A huge range of superior adhesive materials are being studied and developing. Biomedical, industrial, space age and everyday uses are possible.
What happens when you now remove tape? Its adhesiveness is lost. With the properties seen in gecko feet, tape could be reused countless times and never leave residue.
What about tires for your car, footwear for rock climbers or safety gear for high altitude workers? In my reading I saw fumble-free football gloves mentioned (not sure that one will fly).
Take another look at the geckos at your house and think about the phenomenal impact those tiny toes might have.
When you visit The Texas Zoo, concentrate on a completely new and different aspect of a familiar animal. Be sure to look for some wonderful lizards and watch a reptile show (free with zoo admission) from 1-1:30 p.m. Saturdays and Sundays
Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.