1. Institute
of Sensor and Actuator Systems, Vienna University of Technology, Gusshausstrasse
27-29, A-1040 Vienna, Austria
2. Austrian Center of Competence for Tribology, Viktor Kaplan-Strasse 2, A-2700 Wiener Neustadt, Austria
3. Institute for Microsensors, -Actuators & -Systems, University of Bremen, MCB, Otto-Hahn-Allee 1, D-28359 Bremen, Germany