MULTILAYERED PANCAKES OF NONVOLATILE LIQUIDS CLOSE TO A WETTING TRANSITION

We report experimental studies of systems where a wetting transition occurs as the result of a competition between a long-range attractive interaction promoting spreading and a short-range repulsive interaction opposing it. The wetting behavior is monitored from the shape of tiny nonvolatile microdroplets spreading on smooth surfaces. A step grows at the bottom of the droplet, the thickness of which is a monolayer far from transition, then increases when transition is approached, and ultimately diverges when the liquid becomes nonwetting. At long times, the droplet takes the ''pancake'' shape first predicted by de Gennes.1