Stratification Mechanism in the Bidisperse Colloidal Film Drying Process: Evolution and Decomposition of Normal Stress Correlated with Microstructure

The evolution of the normal stress and microstructure in the drying process of bidisperse colloidal films is studied using the Brownian dynamics simulation. Here, we show that the formation process of small-on-top stratification can be explained by normal stress development. At high Pe L ’s, a stratified layer with small particles is formed near the interface. The accumulated particles near the interface induce the localization of normal stress so that the normal stress at the interface increases from the beginning of drying. We analyze this stress development from two points of view, on the global length scale and particle length scale. On the global length scale, the localization of normal stress is quantified by the scaled normal stress difference between the interface and substrate. For all Pe L ’s tested in this study, the scaled normal stress difference increases until the accumula…