title: How a Surface Nanodroplet Sits on the Rim of a Microcap.
abstract: The location and morphology of femtoliter nanodroplets that nucleate and grow on a microcap-decorated substrate in contact with a liquid phase were investigated. We experimentally examined four different wetting combinations of the flat area and the microcaps. The results show that depending on the relative wettability, the droplets sit either on the plain surface or on the top of the microcap or on the rim of the microcap. The contact angle and, for the last case, the radial positions of the nanodroplets relative to the microcap center were characterized, in reasonable agreement with our theoretical analysis, which is based on an interfacial energy minimization argument. However, the experimental data show considerable scatter around the theoretical equilibrium curves, reflecting pinning and thus nonequilibrium effects. We also provide the theoretical phase diagram in parameter space of the contact angles, revealing under which conditions the nanodroplet will nucleate on the rim of the microcap.
authors.affiliation: Soft Matter and Interfaces Group, School of Engineering, RMIT University , Melbourne, VIC 3001, Australia.
authors.forename: Shuhua
authors.initials: S
authors.lastname: Peng
authors.affiliation: Physics of Fluids group, Department of Science and Engineering, Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Ivan
authors.initials: I
authors.lastname: Dević
authors.affiliation: Physics of Fluids group, Department of Science and Engineering, Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Huanshu
authors.initials: H
authors.lastname: Tan
authors.affiliation: Physics of Fluids group, Department of Science and Engineering, Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.|Max Planck Institute for Dynamics and Self-Organization , 37077 Goettingen, Germany.
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse
authors.affiliation: Soft Matter and Interfaces Group, School of Engineering, RMIT University , Melbourne, VIC 3001, Australia.|Physics of Fluids group, Department of Science and Engineering, Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Xuehua
authors.initials: X
authors.lastname: Zhang