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22/3/09: Nominee in Wildlife, 3rd Photography Masters Cup, International Color Awards
Moorish Gecko (Tarentola mauritanica), clinging to the other side of the office window.
Best viewed Large, On Black.
If you've ever seen a gecko, then you must have admired their ability to scurry up walls and stick to ceilings. People had been baffled for years at how geckos manage to adhere to even the most polished surfaces. They don't use claws (otherwise they wouldn't be able to hold on to a glass window like in this photo). Suction was regarded as an unlikely explanation since geckos can cling on to a wall even in a vacuum. That astonishing trick of walking upside down on the ceiling would seem to rule out friction. Furthermore, without any glands on their feet, it would be hard for geckos to produce their own natural glue. So how do they do it?
Scientists found out that that the attractive forces that hold geckos to surfaces are van der Waals interactions, intermolecular forces so weak they are normally swamped by the many stronger forces in nature. Geckos have millions of densely packed, fine hairs, or setae, on their toes. The end of each seta is further subdivided into hundreds to thousands of structures called spatulae. Each such spatula interacts with the surface's molecules and the cumulative effect from the billions of tiny spatulae is a force strong enough to hold many times the weight of the small reptile. Geckos have developed an amazing way of walking, that rolls these hairs onto the surface, and then peels them off again, just like adhesive tape, only better. Because, unlike adhesive tape, the setae on the feet of geckos are also self cleaning and will usually remove any clogging dirt within a few steps! Imagine the possibilities... Synthetic Gecko, Gecko Tape, Carbon Nanotubes, these are some examples of the kind of research going on...