Perforated wetting layers from periodic patterns of lyophobic surface domains

We investigate, both theoretically and experimentally, the wetting morpholo gy of a liquid which is adsorbed onto a chemically structured substrate con sisting of circular lyophobic domains in a lyophilic matrix. For thick film s, the adsorbate morphology is not affected by the underlying domain patter n but reduction in the film thickness leads to the formation of stable hole s and, thus, to perforated wetting films. These perforated films, which exi st for an intermediate range of volumes, are bounded by surfaces of both co nstant mean curvature and high topological genus. By making use of nodoids, we are able to derive an approximate analytical parametrization of these s urfaces. This "muffin-tin" parametrization captures the essential features of the wetting layer morphology as shown by comparison with direct numerica l minimization of the free energy. Furthermore, the theoretical shapes are in very good agreement with experimental data obtained by atomic force micr oscopy.