Self-Assembly of Gradient Concentric Rings via Solvent Evaporation from a Capillary Bridge
Jun Xu, Jianfeng Xia, Suck Won Hong, Zhiqun Lin, Feng Qiu and Yuliang Yang, Self-Assembly of Gradient Concentric Rings via Solvent Evaporation from a Capillary Bridge, PRL 96 066104 (2006) 
The dewetting of a liquid forming a capillary bridge between a plane and a sphere is studied. The evaporating liquid carries MEH-PVV (a non-volatile polymer with optical applications) which in a sense acts to record the drying dynamics of the carrier liquid (toluene). In fact, the polymers also perturb the dewetting process via a ``slip-stick" mechanism similar to the effect observed when a drop dries off of an unclean surface. The evaporation process produces a pattern concentric rings of polymer on the Si substrate, with a non-trivial radial scaling of ring spacing: an artifact of the drying geometry.
When the toluene (containing MEH-PVV) evaporates from the capillary bridge (see figure 1), the footprint of the liquid on the Si wafer is determined by a competition between pinning and capillary forces.