Investigation of the Effect of 3-dimensional Meniscus Geometry on Fluid Dynamics and Crystallization Via in Situ optical microscopy-assisted Mathematical Modeling.

Solution-based thin-film solidification is a complex process involving various transport phenomena that are intricately dependent on multiple experimental parameters. The difficulty of analyzing this process experimentally or conducting exact numerical simulation make it challenging to understand, predict, and control the solidification process. In this work, we propose a simple and effective technique to analyze the thin-film solidification process during solution shearing, based on 3D geometrical model of the meniscus. The 3D meniscus geometry, which changes depending on the experimental parameters, was attained using high-speed side-view and top-view in situ microscopy. Thereafter, mass and momentum transport mathematical models were applied to obtain numerical solutions of transport phenomena within the meniscus. Utilizing these results, the underlying mechanism of dendritic growth of small molecule organic semiconductor was elucidated, which has previously been unknown. The 3D meniscus modeling was particularly important for this analysis, as dendrite formation is strongly dependent on the meniscus geometry near the contact line and mass transport variation perpendicular to the coating direction. Our technique enables the study of complex relationship between experimental parameters and solidification process, which is widely applicable to various materials and coating systems; whereby, better understanding of thin-film growth and device performance optimization is possible. This article is protected by copyright. All rights reserved.