Geckos are reptiles that inhabit temperate and tropical regions, members of the family Gekkonidae. There are over 1,000 different species of geckos, that can be a variety of colours.
Most gecko species can climb walls and other surfaces thanks to their particular feet, the surface of which can adhere to any type of material with the exception of Teflon (PTFE). This phenomenon can be explained due to the physical structure of the gecko’s feet. Indeed, the bottom surface of a gecko’s leg consists of millions of hairy structures called setae. These setae are 5mm (0.2in) long and are thinner than human hair. There are thousands of tiny structures called spatula on every seta. Geckos create Van der Waals force (ie a distance-dependent interaction between atoms or molecules) by making contact with the surface of materials using their spatulas: more spatulas implies more surface area. The spatulas have sharp edges, which on the application of stress at a specific angle, bend and create more contact with the surface in order to climb on them vertically. Thus, more contact with the surface creates more Van der Waals force to support the whole body of the creature. One seta can hold weights up to 20mg (0.0007oz) using Van der Waals force. In total, with the help of millions of setae, a gecko can hold about 135kg (300lb).