1. Haptic Intelligence Department Max Planck Institute for Intelligent Systems Heisenbergstr. 3 70569 Stuttgart Germany
2. Robotic Materials Department Max Planck Institute for Intelligent Systems Heisenbergstr. 3 70569 Stuttgart Germany
3. Institute for Control Engineering of Machine Tools and Manufacturing Units University of Stuttgart Seidenstraße 36 70174 Stuttgart Germany
4. Paul M. Rady Department of Mechanical Engineering University of Colorado Boulder, 1111 Engineering Drive Boulder CO 80309 USA
5. Materials Science and Engineering Program University of Colorado Boulder, 1111 Engineering Drive Boulder CO 80309 USA