1. Institute of Sensor and Actuator Systems, Vienna University of Technology, Floragasse 7, 1040 Vienna, Austria
2. Austrian Centre of Competence for Tribology, AC2T research GmbH, Viktor-Kaplan-Straße 2, 2700 Wr. Neustadt, Austria
3. Group of Microsystems, Actuators and Sensors, E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain