1. Institut für Theoretische Physik II: Soft Matter, Heinrich Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
2. Department of Physics, University of Bío-Bío, Av. Collao 1202, P.O. Box 5C, Concepción, Chile
3. Chemical Engineering Department and Surface Analysis Laboratory (ASIF), University of Concepción, P.O. Box 160-C, Correo 3, Concepción, Chile