Geckos can run upside-down across a smooth glass ceiling like it’s nothing. Their feet aren’t sticky, aren’t wet, and don’t have suction cups. So what holds them on?
The answer is invisible to your eye. Each gecko toe is covered in millions of tiny hairs called setae. Each seta splits into hundreds of even tinier branches, like the bristles of a brush at the end of every hair. When the gecko presses its foot down, those bristles get so close to the surface that a strange physics effect kicks in: a weak attractive force between the atoms on the surface and the atoms on the gecko, called the van der Waals force.
Individually each tiny hair is sticky with almost no force. But with hundreds of millions of them gripping at the same time, the strength is enormous. Scientists are now copying the design to make tape and gloves that stick to walls without glue.
