New Scientist: It has long been thought that two primary forces were involved in the ability of geckos to cling to surfaces: van der Waals and capillary. Now researchers at the University of Waterloo in Ontario, Canada, say that a third force—contact electrification—may actually be the main source of gecko adhesion. When they dragged geckos across various surfaces, the researchers noticed that the animals’ toe pads became positively charged while the surfaces became negatively charged, indicating that electrons were shifting from one to the other. Moreover, the strength of the electrostatic force and that of the adhesion between the geckos’ feet and the surfaces were similar. The researchers conclude that electrostatic forces allow geckos to cling to ceilings much the way a balloon rubbed on hair or clothing sticks to walls.
