Gecko feet once blamed on van der Waals now look electrostatic
Nearly two thousand gecko species cling to warm climates on every continent but Antarctica. About sixty percent of them grow adhesive toe pads that walk walls and ceilings without glue. A twenty fourteen study argued contact electrification, not weak van der Waals forces, mainly drives the stick.
Sizes stretch from the sixteen-millimetre Jaragua sphaero, found in two thousand one off Hispaniola, to a stuffed Gigarcanum delcourti about sixty centimetres long, likely from New Caledonia. Most lack eyelids and wipe a transparent brille with the tongue. Night vision can be roughly three hundred fifty times more colour-sensitive than human eyes in dim light, after cones rebuilt what rods had lost. Tokay geckos shout loud mating calls; the English name itself echoes Javanese tokek.
Each square millimetre of pad holds about fourteen thousand setae five micrometres across, each tipped with one hundred to one thousand spatulae. Pads of a typical seventy-gram gecko could theoretically hold about one hundred thirty-three kilograms. Toes hyperextend tip-first like peeling tape, and phospholipids help the foot release before the next step. Humidity usually boosts grip; full underwater immersion weakens it. Pads evolved independently in about eleven lineages and vanished in at least nine.
House geckos earn welcome indoors by eating moths and mosquitoes. Leopard geckos, common pets, lack adhesive pads and cannot climb vivarium glass. Mid-Cretaceous Burmese amber around one hundred million years old already preserves adhesive pads on Cretaceogekko. Skin papillae up to four microns long shed water and can kill gram-negative bacteria on contact. Biomimetic labs chase reusable dry adhesives, but manufacturing synthetic setae remains hard. What looks like magic on a ceiling is layered microstructure, electrostatics, and careful peeling.
Source: Gecko
