Droplets profiles and wetting transitions in electric fields

This paper presents current work in electrowetting. In the first part, we discuss experimental measurements of curvature of a conductive liquid drop in an electrical field. A recent theoretical and numerical study [8] predicts that diverging electric fields give rise to deviations close to the contact line from the usual spherical cap shape. We present here the first experimental measurements, compared to numerical simulations. In the second part, we recall how electrowetting is likely to induce wetting transitions, and describe the experimental setup designed to this purpose. Ellipsometry monitoring of film thickness is intended to follow total towards pseudo-partial wetting transition, allowing to reconstruct the effective interface potential of the system, acting like the electrostatic counterpart to the mechanical Surface Force Apparatus. (C) 2004 Elsevier B.V. All rights reserved.