MULTILAYERED PANCAKES OF NONVOLATILE LIQUIDS CLOSE TO A WETTING TRANSITION

We report experimental studies of systems where a wetting transition o ccurs as the result of a competition between a long-range attractive i nteraction 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 fa r from transition, then increases when transition is approached, and u ltimately diverges when the liquid becomes nonwetting. At long times, the droplet takes the ''pancake'' shape first predicted by de Gennes.1