Wetting between structured surfaces: Liquid bridges and induced forces

Wetting phenomena are theoretically studied for a slab geometry consisting of a wetting phase confined between two chemically patterned substrates. Ea ch of these is decorated by an array of stripes whose composition alternate s between two different surface phases. For a single pair of opposing strip es, the wetting phase may either form a bridge spanning from one surface to the other or it may break up into two separate channels. The bridge state induces an effective interaction between the two substrates. This leads to the bridge itself haring a preferred contact angle and the substrates havin g a preferred separation. In the case of many stripes, one has a whole sequ ence of morphological transitions with the number of bridges decreasing as the surface separation grows.