1. Institute of Physics, University of Freiburg, Herrmann-Herder-Strasse 3, D-79104 Freiburg, Germany
2. FIT Freiburg Centre for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
3. Fraunhofer IWM, MikroTribologie Centrum μTC, Wöhlerstrasse 11, D-79108 Freiburg, Germany