Geckos can stick to surfaces because their bulbous toes are covered in hundreds of tiny microscopic hairs called setae. Each seta splits off into hundreds of even smaller bristles called spatulae. Scientists already knew that the tufts of tiny hairs get so close to the contours in walls and ceilings that the van der Waals force kicks in. This type of physical bond happens when electrons from the gecko hair molecules and electrons from the wall molecules interact with each other and create an electromagnetic attraction...Additional explanation at LiveScience. Photo via.
A gecko by definition is not sticky — he has to do something to make himself sticky," study lead author Alex Greaney, a professor of engineering at Oregon State University in Corvallis, told Live Science. "It's this incredible synergy of the flexibility, angle and extensibility of the hairs that makes it possible."
Greaney and a team of researchers created a mathematical model that shows how the setae angle and the forces that act on a gecko as it climbs interact to create a delicate but powerful sticking system.