Liquid microstructures at solid interfaces

The propensity of liquid films to bead off poorly wettable substrates leads to a wide variety of liquid structures via mechanisms which are far from b eing fully understood. In particular, dewetting via unstable surface waves may be driven at least by dispersion forces, electrostatic forces, or by Ma rangoni-type transport. A hierarchy of dynamical instabilities finally tran sforms the initial homogeneous film into the final state, consisting of an ensemble of individual, isolated droplets. While these processes of self-or ganized structure formation are interesting in themselves, it may also be d esirable to generate liquid structures in a more well-defined and predictab le way. We have therefore investigated experimentally the behaviour of vari ous liquids on substrates, the wettability of which has been laterally stru ctured. The resulting artificial liquid objects display several remarkable properties, both statically and dynamically. Aside from potential applicati ons as 'liquid microchips', it is shown how fundamental quantities can be e xtracted from the shapes of the liquid surfaces, as determined by scanning force microscopy. The three-phase contact line tensions obtained in this wa y are in fair agreement with theoretical predictions and might help to reso lve long-standing debates on the role of wetting forces on the nanometre sc ale.