For over 2 millennia, humans have watched lizards and bugs scale vertical surfaces in awe. Only recently the attachments mechanisms of these animals have been understood. It is now possible to use similar mechanisms to allow robots to climb in the same manner as these animals.
Robot Geckos ability to climb surfaces, whether wet or dry, smooth or rough, has attracted scientists attention for decades. By means of compliant micro/nano-scale high aspect ratio beta-keratin structures at their feet, geckos manage to adhere to almost any surface with a controlled contact area. It has been shown that adhesion is mainly due to molecular forces such as van der Waals forces.
The Geckos ability to stick to surfaces lies in its feet, specifically the very fine hairs on its toes. There are billions of these tiny fibers which make contact with the surface and create a significant collective surface area of contact. The hairs have physical properties which let them bend and conform to a wide variety of surface roughness, meaning that the adhesion arises from the structure of these hairs themselves.
The structure of the biological Gecko foot-hair is very complicated and miniscule. Each fiber is made from multiple sections. Each fiber consist of a micro hair which is roughly 5 microns in diameter, and atop each of these micro-fibers sit hundreds of nano-fibers which are 200 nanometers in diameter. There are between 100 and 1000 nano-fibers on the end of each micro-hair.
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