Precursor Film Profiles of Spreading Liquid Drops

Abstract

We present the first precise characterization of the profile of the precursor films which progressively develop ahead of the macroscopic edge of a spreading liquid drop. Experiments are performed on a model system (nonvolatile high-molecular-weight polydimethylsiloxane on smooth silicon wafers), using an ellipsometer with a high spatial resolution. Both the film profile and its evolution with time are in good qualitative agreement with recent models which include long-range force effects. Clear quantitative discrepancies may reveal specific polymeric effects.