Thin microstructured polymer films by surface-directed film formation

Evaporated gold films are hydrophilized within well defined areas of several micrometer size by microcontact printing of 11-mercaptoundecanoic acid. The localized hydrophilizing of the surface controls the formation of water microdroplets within these areas due to preferred condensation from a water saturated atmosphere. The preparation of regular well defined condensation patterns of water microdroplets is necessary to obtain structured thin polymer films from ordered liquid/liquid (water/organic polymer solution) two-phase systems by dip-coating. Through incomplete surface wetting of the hydrophobic polymer solution, the polymer is strictly excluded from the hydrophilic surface areas covered by water microdroplets. Different steps of water condensation and subsequent polymer film formation are characterized by microscopic methods. The microstructure of the film generated in this way is compared with predetermined microstructures used for surface heterogenization. It is demonstrated that the replication of well defined micropatterns from a given stamp structure to a polymer film is of high accuracy with respect to the long range order of the periodic features of the transferred structures. The reproducibility of the individual motif is shown to depend on its geometry and the condensation process. Microstructures in micrometer and submicrometer dimension could be prepared by the technique described. (C) 1999 Elsevier Science S.A. All rights reserved.