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how do cresty's feet work?

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how do cresty's feet work?

Post by ginnerone on Sun Jun 20, 2010 1:38 am

The bottoms of gecko's feet are covered with millions of tiny foot hairs on each toe, these foot hairs are called setae, each are about as long as the width of two human hairs (about 100 millionths of a meter). Each seta, is divided at the end into approximately a thousand tiny spatulae (Called this due to their shape) which are about 200 billionths of a meter wide, which is smaller than the wavelength of visible light. Using these setae and spatulae a gecko’s toes can create a large surface contact area. Using such tiny spatulae, they are able to make use of Van-Der Waals force a weak attractive force which is present between molecules, to stick themselves to almost any surface. Geckos' feet are naturally ultra hydrophobic, in this case, hydrophobic referring to a molecule which is repelled by water or is a water repellent and have been tested by sticking them to a GaAs semiconductor, which is also hydrophobic.

The only thing known to make two hydrophobic surfaces adhere in air is Van der Waal's force.






The seta on gecko’s feet is 10 times more adhesive than predicted from prior measurement on whole animals. The adhesive is so strong that a single seta can lift the weight of an ant 200 µN = 20 mg. A million setae could lift the weight of a child (20kg, 45lbs).

A million setae could easily fit onto the area the size of a one pound coin. The combined attraction of a billion spatulae is a thousand times more than a gecko needs to hang from the ceiling. The maximum potential force of 2 million setae on 4 feet of a gecko would be; 2 million x 200 micro Newton = 400 Newton = 40.78 kilograms of force, or about 90 lbs. This is 600 times greater sticking power than friction alone can account for.
Any gecko can hold up its entire body weight with only a single finger. To get such a sticky foot off the surface is as easy to them as putting it on, they simply increase the angle of the foot and it just pops off
. This is helped, of course, by the fact that gecko’s toes are backwards-jointed, meaning that when they flex their toes they curl upward rather than downward, allowing them to peel their toes from the surface to which they are stuck.
Gecko feet are also self cleaning. Because the same force applies between dirt particles and the surfaces the geckos walk on, the dirt prefers to stick to the relatively large and attractive surface rather than the tiny spatulae on the gecko's feet. So when a gecko's feet get dirty, all they have to do is walk a few steps and they are clean again. A geckos adhesive microstructure requires minimal attachment force, leaves no residue, is directional, detaches without measurable forces, is self cleaning, and works underwater, in a vacuum, and on nearly every surface material and profile.
In other words, perfect for synthesis.

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Re: how do cresty's feet work?

Post by xvickyx on Sun Jun 20, 2010 12:31 pm

Cool info

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