We know that geckos stick to walls because of the van der Waals force, but these are the first videos that let us see the power of a single “hair” on a gecko’s foot. We can see the fiber stick on, increase its grip, and drag an object.
The van der Waals force appears when an otherwise neutral atom gets a slight imbalance of charge. The electrons pile up on one side, leaving the protons exposed on the other side. When this atom nears another atom, the preponderance of electrons on one side repels the electrons in the second atom. The second atom’s electrons pile up on its far side, leaving its protons exposed, and protons attract electrons. So the first atom’s electron-heavy side is attracted to the second atom’s proton-heavy side, and the atoms stick together.
This is what makes a gecko stick to a surface. Its foot is covered with tiny hairs, all of which use the van der Waals force to stick to a wall. The more hair the gecko exposes, the more it sticks. In the video above we see how a gecko gets a grip. It places its foot, and then pushes, pressing more hairs against the wall to get more van der Waals interactions going.
It’s very impressive to see altogether, but my favorite video of the phenomenon shows us the power of a single fiber. Here we see the a single gecko foot fiber placed against a large metal pin. We can see the fiber adhere, engage, and drag the pin forwards, before finally snapping back.