Investigation of the Effect of Substrate Molecular Roughness on Surface Phase Behavior Jeffrey R. Errington, Department of Chemical & Biological Engineering, University at Buffalo, The State University of New York The goal of this project is to enhance our understanding of the effect of molecular disorder (roughness) within a substrate’s surface on the behavior of a fluid in contact with it. We have initiated a project aimed at determining how a fluid’s wetting behavior evolves with molecular surface roughness. The first step in this project involved the development of a robust method for determining the contact angle a liquid lens forms on a surface. The figure below provides an example of a surface free energy curve that is extracted from one of our Monte Carlo simulations. Such information provides the spreading coefficient of a droplet. Our most recent efforts have focused on understanding the role of substrate molecular roughness on wetting behavior. The key aspect of this work is to probe how the organization of molecules within a substrate influences surface properties, such as the contact angle. The figure above shows the contact angle a Lennard-Jones fluid adopts when adsorbed to various substrates as a function of the geometric roughness of the substrate-fluid interface.