J Low Temp Phys (2009) 157: 277–295 DOI 10.1007/s10909-009-9907-x Coarse-Grained Interaction of a Fluid with a Physically-Patterned Solid Surface: Application to Nanodroplet Wetting Hongfei Wu · Ali Borhan · Kristen A. Fichthorn Received: 16 May 2009 / Accepted: 16 June 2009 / Published online: 15 July 2009 © Springer Science+Business Media, LLC 2009 Abstract We derive coarse-grained potentials to describe the interaction of a phys- ically adsorbed, ﬂuid-phase atom with a solid surface that is patterned with an array of rectangular or cylindrical pillars. The coarse-grained potentials are used in molec- ular dynamics simulations to probe the wetting of a Lennard-Jones liquid droplet on various patterned solid surfaces. Our results, which indicate that surface patterning can signiﬁcantly inﬂuence wetting, are in agreement with previous studies. Keywords Coarse-grained potential · Patterned surface · Apparent contact angle · Wettability · Molecular dynamics PACS 68.08.-p · 68.08.Bc 1 Introduction The interaction between ﬂuids and physically-patterned solid surfaces is important in a variety of applications, including the design of solid surfaces with controlled wet- tability. Interestingly, the wettability of a solid surface can be linked to its structure. There is much evidence in nature and laboratory experiments that patterned or rough surfaces can exhibit superhydrophobicity [1–6], which means that they can support water droplets with contact angles greater than 150 ◦ . From a theoretical perspective, it is of interest to predict how a given surface morphology will inﬂuence wettabil- ity. The patterned surfaces that exhibit superhydrophobicity in experimental studies typically exhibit roughness over μm length scales and droplets on these surfaces can range from μm to mm in diameter. These are the length scales over which continuum This work was sponsored by Grant CBET 0730987 from the National Science Foundation. H. Wu · A. Borhan · K.A. Fichthorn ( ) Dept. of Chemical Engineering, Penn State University, University Park, PA 16802, USA e-mail: ﬁchthorn@psu.edu