Van der Waals force
The bottom surface of a gecko's leg will consist of millions of hairy structures called setae. These setae are 5 mm long and are thinner than a human hair. There are thousands of tiny structures called spatula on every seta. Geckos create Van der Waals force by making contact with the surface of materials using their spatulas. More spatulas implies more surface area. The spatulas have sharp edges, which on application of stress in a specific angle, bends and creates 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 20 mg using Van der Waals force. Totally, with help of millions of setae, a gecko can hold about 300 pounds. The β-keratin bristles are approximately 5 μm in diameter. The end of each seta consists of approximately 1,000 spatulae that are shaped like an isosceles triangle. The spatulae are approximately 200 nm on one side and 10–30 nm on the other two sides. The setae are aligned parallel to each other, but not oriented normal to the toes. When the setae contact another surface, their load is supported by both lateral and vertical components. The lateral load component is limited by the peeling of the spatulae and the vertical load component is limited by shear force.