Droplets pinned at chemically inhomogenous substrates: A simulation study of the two-dimensional Ising case.
As a simplified model of a liquid nanostripe adsorbed on a chemically structured substrate surface, a two-dimensional Ising system with two boundaries at which surface fields act is studied. At the upper boundary, the surface field is uniformly negative, while at the lower boundary (a distance L apart), the surface field is negative only outside a range of extension b, where a positive surface stabilizes a droplet of the phase with positive magnetization for temperatures T exceeding the critical temperature T_{w} of the wetting transition of this model. We investigate the local order parameter profiles across the droplet, both in the directions parallel and perpendicular to the substrate, varying both b and T. Also, precursor effects to droplet formation as T approaches T_{w} from below are studied. In accord with theoretical predictions, for T>T_{w} the droplet is found to have the shape of a semiellipse, where the width (distance of the interface from the substrate) scale is proportional to b (b^{1/2}). So, the area of the droplet is proportional to b^{3/2}, and the temperature dependence of the corresponding prefactor, which also involves the interfacial stiffness, is studied.
Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CCT-CONICET La Plata, UNLP, Calle 59 Nro. 789, (1900) La Plata, Argentina and Departamento de Ciencias Básicas, Facultad de Ingeniería, Universidad Nacional de La Plata, Argentina.
Marta L
ML
Trobo
Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CCT-CONICET La Plata, UNLP, Calle 59 Nro. 789, (1900) La Plata, Argentina, and Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Argentina.
Ezequiel V
EV
Albano
Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany.
Kurt
K
Binder