Monday, May 07, 2007

THE SCIENCE OF STICKY FEET

The animal world has many surprising things from which scientists are finding a lot of new ideas. Most insects can stay attached to a surface which is facing downwards. Since their weight is so small, insects can stick to the wall or ceiling using many different ways. But some researchers (Dr. Autumn et al.) found that the Gecko (a type of reptile) has a unique way to stick on surfaces with their feet, eventhough they are much bigger and heavier than small insects. Recent studies revealed that it is the physical structure of the Gecko’s feet that allows them to stick to the wall.
The toes of the gecko have attracted a lot of attention, as they adhere to a wide variety of surfaces, without the use of liquids or surface tension. The skin of Gecko’s toes has print like structure and it is formed by almost 500,000 hairs on each foot. (http://en.wikipedia.org/ wiki/Gecko) This hairs are called setae; their width is 1/10 the diameter of human hair and the length is the diameter of two human hairs. The most amazing thing is how these hairs can stick to the surfaces using totally different way than small insects.
The setae is not just a hair, each setae can have 100 to 1000 microscopic branches, like a tree. These branches are called spatulae and every spatulae has a small pad on its tip. Due to being smaller than the wavelength of visible light, the pad must be studied with the electron microscope. Because pads can not be seen by normal optical microscope. Recently, researchers confirmed that the underlying attraction of the pads with a surface is the physics principle of van der Waals force and this process makes Geckos’ feet sticky.

If two molecules touch each other, they can attract each other, and start sharing their electrons. This phenomenon produces a weak attractive force which is called van der Waals force. This term is named after the Dutch physicist van der Waals (1837-1923, Amsterdam). Although the attraction strength of a single pad is relatively weak, when it is multiplied by a billion pads on a Gecko’s feet, the attraction becomes incredibly strong. Geckos may have 6.5 million foot hairs, if all hairs are stuck at the same time, this force can hang a man to the ceiling! When a Gecko steps, it spreads its toes, which are lined with hair. The foot is placed on the surface in a rolling fashion. Otherwise Geckos can’t take off the foot suddenly from the surface. This sticky feet structure has led to many new ideas for how to make sticky materials on hard surfaces like post-it and other type of stickers.

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1 Comments:

At 11:31 PM , Blogger Номио said...

woooow that is just amazing... It is just one of the peculiarities of nature, isn't it?

Amazing thing about nature is that everything is too well organized and too complex to be originated from simple bang.

 

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