Lizard, lizard on the wall, why is it you do not fall?
Scientists have been asking that question of the limber little gecko for at least 75 years. These scaly climbers can scuttle nimbly across a polished glass ceiling. In a pinch, they can hang by one toe.
Over the decades, experiments and observations have ruled out suction, electrostatic forces, and glue as possible explanations. Now, a West Coast team of scientists and engineers has discovered that a surprisingly large sticking force arises when tiny hairs, or setae, on gecko feet rub up against surfaces.
From each seta sprout even tinier stalks, called spatulae. When a gecko gloms a foot onto a surface, the billion-or-so spatulae that carpet its sole snuggle so close to the surface that intermolecular forces such as van der Waals bonds may come int