People have long wondered how geckos manage to stick to the sides of structures without falling off. The short answer is that they have sticky feet. But did you know geckos turn off sticky feet when they need to run faster?
How do geckos turn off sticky feet?
Geckos use toe hairs to turn the stickiness of their feet on and off. Oregon State University (OSU) discovered the details of this mechanism in 2014. They published their results in an article that appears in the Journal of Applied Physics.
The researchers noted that the geckos’ “adhesion system mechanism” has long been a curiosity. According to Science Daily (cited below):
“‘Since the time of the ancient Greeks, people have wondered how geckos are able to stick to walls — even Archimedes is known to have pondered this problem,’ said Alex Greaney, co-author and an assistant professor of engineering at OSU. ‘It was only very recently, in 2000, that Kellar Autumn and colleagues proved unequivocally that geckos stick using van der Waals forces.'”
Geckos have a system of hairs called “seta” on their toes. The seta can bend when they come into contact with rough surfaces in order to provide points of contact that keep the sticky surface of the gecko’s toe pads from adhering. Those hairs provide millions of points of contact to allow the creatures to maneuver over terrain without sticking.
Other insects and spiders also have this adhesion system. That’s why they can stick sideways to walls, seeming to defy gravity.
The stickiness system
Greany told Science Direct: “Understanding the subtleties of the process for switching stickiness on and off is groundbreaking. By using mathematical modeling, we’ve found a simple, but ingenious, mechanism allows the gecko to switch back and forth between being sticky or not. Geckos’ feet are by default nonsticky, and this stickiness is activated through application of a small shear force. Gecko adhesion can be thought of as the opposite of friction.”
The stickiness of geckos’ feet has long fascinated scientists seeking to produce material for use in adhesives. The ability of geckos to turn off sticky feet is yet another piece of the materials science puzzle that may come in handy someday in fields like construction and robotics. — WTF fun facts