| The lithographic printing process has been the method of choice for the production of printed mass media for the past fifty years. In the critical step of the lithographic printing process, fresh ink is transferred through a thin barrier film of water to hydrophobic regions of a chemically patterned printing plate, which may already bear a thin layer of residual ink. The mechanisms behind this liquid displacement event are not well understood and are investigated within this thesis.; A series of lubrication-theory-based models was developed in order to analyze the early stages of displacement in simplified geometries. First, we model a system consisting of two thin liquid films, representing water and ink, bounded by parallel solid surfaces and subject to van der Waals forces which drive dewetting. It is found that the nucleation of water-film breakup is strongly dependent on the length scale of chemical patterns. Second, the steady behavior of the interface between two immiscible liquid layers flowing in a channel where one wall is flat and the other exhibits isolated or periodic step-changes in surface topography is considered. Here we find that interfacial behavior depends strongly on density, viscosity, and thickness ratios, as well as the periodicity of the topography. Third, we examine the instability of a system in which three stratified thin liquid films are confined in a channel with parallel walls and the interior film (representing water between ink layers) is subject to van der Waals-driven breakup. It is found that this breakup occurs with length and time scales appropriate for the lithographic printing process, making it a particularly relevant model for emulsification in the printing nip.; Two sets of visualization experiments were also performed in order to analyze the later stages of displacement. The first employs a two-layer geometry in which the water layer retracts directly from the surface of a hydrophobic patch, and the second explores the retraction of a water layer between two ink layers. Both sets of experiments show that the structure of the final ink-water emulsion is strongly dependent on the initial distribution of nucleation points. |
