1. Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich, Switzerland
2. Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, Boulder, Colorado 80309, USA
3. Department of Information Engineering, University of Florence, Via di S. Marta 3, 50139 Florence, Italy
4. Department of Biomedical Engineering, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands