How Do Gecko Lizards Walk on Ceilings?
Geckos have the ability to walk on walls and ceilings due to special adhesive pads on their feet. These small lizards live in warm climates. They have wide-spreading toes. Each toe ends in a pad and a hidden claw. These toe pads, made up of thousands of tiny suction cups, enable the gecko to cling to any smooth surface-even glass.
The claws can be moved out like those of a cat, and are used on rough surfaces. The gecko’s grip is so good that it can scamper easily over walls, ceilings, and windowpanes while searching for insects and other prey.
The foot of a gecko is covered with about a billion tiny hairs called spatulae. Each is some 200 nanometers in length and width. A human hair is roughly 100,000 nanometers wide. The hairs work like Velcro. They are so small they wedge between the atoms of a surface and form molecular bonds with the wall or ceiling, putting the gecko in direct contact with its environment.
Up to 1,000 spatulae are arranged into groups called setae that are about one-tenth the diameter of a human hair. Setae are in turn arranged in rows, which are visible to the naked eye.
Researchers at the Max Planck Institute for Metals Research in Germany usually study the physics of entire setae, but when they tried to isolate one of the super tiny spatulae, they noticed that a little humidity went a long way.
Now scientists have learned the hairs get even stickier with an increase in humidity. While trying to attach the hairs to various glass plates and wafer surfaces, they found that the more hydrophilic – water-loving – the surface was, the better the hair stuck to it.