Resolving the nanoscale adhesion of individual gecko spatulae by atomic force microscopy

Abstract

Animals that cling to walls and walk on ceilings owe this ability to micron and nanoscale attachment elements. The highest adhesion forces are encountered in geckoes, which have developed intricate hierarchical structures consisting of toes (millimetre dimensions), lamella (400–600 μm size), setae (micron dimensions) and spatulae (∼200 nm size). Adhesion forces of setae on different substrates have previously been measured by a micro-electromechanical system technique. Here we report the first successful experiments in which the force–displacement curves were determined forindividualspatulae by atomic force microscopy. The adhesion force for these smallest elements of the gecko's attachment system is reproducibly found to be about 10 nN. This method sheds new light on the nanomechanisms of attachment and will help in the rational design of artificial attachment systems.