Gecko feet

These setae are fibrous structural proteins that protrude from the epidermis, which is made of β-keratin,[5] similar to α-keratin being the basic building block of human skin and finger nails.

The bottom surface of a gecko's foot will consist of millions of hairy structures called setae.

Geckos create Van der Waals force by making contact with the surface of materials using their spatulas.

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.

This integral can then be written in cylindrical coordinates with x being the perpendicular distance measured from the surface of B to the infinitesimal volume, and r being the parallel distance: The gecko–wall interaction can be analyzed by approximating the gecko spatula as a long cylinder with radius rs.

The Van der Waals force per spatula, Fs can then be calculated by differentiating with respect to D and we obtain: We can then rearrange this equation to obtain rs as a function of AH: where a typical interatomic distance of 1.7 Å was used for solids in contact and a Fs of 40 μN was used as per a study by Autumn et al.[5] The equation for rs can then be used with calculated Hamaker constants[8] to determine an approximate seta radius.

These values are similar to the actual radius of the setae on a gecko's foot (approx.