Geckos are able to stick to ceilings and walls, in addition to other surfaces using tiny hairs in their feet, a new study reveals. Insects and some spiders are also able to seemingly defy gravity as they easily hang upside down, or on vertical surfaces.

Oregon State University (OSU) researchers found seta, branched hairs on the feet of geckos, can instantly become sticky - or not - at the will of the animal.

"These are really fascinating nanoscale systems and forces at work. It's based not just on the nature of the seta but the canted angles and flexibility they have," Alex Greaney, assistant professor at the OSU College of Engineering, said.

Gecko feet are not traditionally sticky, and scientists and philosophers have studied the animals since ancient days trying to uncover secrets of how they travel. In 2000, biologists recognized, for the first time, that the species take advantage of van der Waal forces, a form of weak attraction between atoms and molecules. This attraction between particles is formed from interactions between negatively-charged electrons, existing in clouds around protons, having a positive charge. This can create temporary attractions between the atomic bodies.

By applying a slight shear force to the hairs, the animals can turn adhesion on and off between their feet and surfaces. This attraction is great enough to hold 50 times the weight of the lizard. The creatures are able to race upside down at 20 body lengths a second by constantly turning the adhesion on and off.

Geckos use their rare ability to avoid predators, as well as to capture small prey. They have five toes on each foot, each of which is covered in the spatula-shaped setae.

Further research of setae could help engineers develop new generations of robots capable of crawling up walls and across ceilings. Adhesives could also be manufactured from a similar structure of a variety of purposes.

Researchers from Linköping University recently discovered that geckos and spiders are unable to remain upside down for long periods of time. Eventually, the attraction acting between the setae and the surface on which the gecko is attached eventually releases, due to subatomic forces.

"At the nano level, conditions are a bit different. The movement of the molecules is negligible in our macroscopic world, but it's not in the nano world," Stefan Lindström of Linköping University, who worked on the earlier research, said.

Investigation of seta and the ability of geckos to easily move upside down or along vertical surfaces was profiled in the Journal of Applied Physics.