title: Morphology and phase behavior of ethanol nanodrops condensed on chemically patterned surfaces.
abstract: Equilibrium wetting of ethanol onto chemically patterned nanostripes has been investigated using environmental atomic force microscopy (AFM) in noncontact mode. The chemical patterns are composed of COOH-terminated "wetting" regions and CH3-terminated "nonwetting" regions. A specially designed environmental AFM chamber allowed for accurate measurements of droplet height as a function of the temperature offset between the substrate and a macroscopic ethanol reservoir. At saturation, the height dependence scales with droplet width according to w1/2, in excellent agreement with the augmented Young equation (AYE) modeled with dispersive, nonretarded surface potentials. At small under- and oversaturations, the AYE model accurately fits the data if an effective DeltaT is used as a fitting parameter. There is a systematic difference between the measured DeltaT and the values extracted from the fits to the data. In addition to static measurements, we present time-resolved measurements of the droplet height which enable the study of condensation-evaporation dynamics of nanometer-scale drops.
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA. checco@bnl.gov
authors.forename: Antonio
authors.initials: A
authors.lastname: Checco
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Ocko