Imbibition into a thin porous medium: an experimental and pore-scale modeling study of coated paper

Abstract

The goal of this thesis was to understand water-based liquid transport in thin multi-layer porous materials. Existing imaging techniques were adopted in order to make it possible to image the layers and extract their three-dimensional (3D) geometrical information. The extracted geometry was then used in pore-scale modeling tools to determine main hydraulic properties of the layer. In the next step, fluid flow in porous layer modeling was carried out using open source modeling tool, OpenFOAM. Through the work packages, appropriate suggestions, regarding the digital design of layers and used liquid as liquid phase of interest, were proposed. In addition to that, the developed modeling and experimental tools were adopted in a way that they can be applied and used in a wide range of thin porous layers applications including papers, fuel cells, membranes, and catalyst layers. Inkjet printing is attracting much attention due to its potential in the printing of graphics, 3D objects, medical applications, paper-based diagnostic devices and electronics. The inkjet printing involves ejection of a fixed amount of liquid phase from a nozzle onto a substrate; paper in case of graphics. The ejected droplet falls due to gravity. The impinged droplet spreads and penetrates into paper due to surface tension aided flow. Capillarity is the dominant force drawing ink into the pore structure of the paper. Micro capillary penetration starts typically within 0.1 ms after the droplet arrives. In order to identify and understand the main characteristics of the paper substrates used in inkjet printing, manufacturing process of a certain coated paper sample (Magno Gloss) was described. The chosen coated paper was then used later in modeling and experimental parts of the thesis.