Geckos are lizards with an impressive capacity to walk upside down on almost any surface, using just the attractive forces created by their feet to hold on. Borrowing the miraculous mechanism of the creature's feet, CAS researchers have succeeded in producing superhydrophobic nanotube films noted for their high adhesion. How can geckos run upside down on polished glass? Some think that the creature has suction cups on their feet, others say it is due to electrostatic attraction, and still others believe that they use hooks or claws or secrete glue on their feet. The question kept puzzling people for years until 2000, when a study published in Nature found that the amazing climbing ability of geckos can be attributed to their nearly five hundred thousand tiny elastic hairs called setae, each of which branches at the end into up to 1,000 even tinier fibers called spatulas. The research shows that the fine structure enables the contact between the setae and surface close enough to effect van der Waals forces-the weak attraction that molecules have for one another when they are brought very, very close together. Although each hair exerts a tiny force on the surface, when being added together, they enable geckos to hang off surfaces at any angle.
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