1. Department of Materials Science and Engineering Carnegie Mellon University Pittsburgh PA 15213 USA
2. Department of Mechanical Engineering Carnegie Mellon University Pittsburgh PA 15213 USA
3. Department of Electrical Engineering and Automation Aalto University Helsinki 00076 Finland
4. Department of Biomedical Engineering Carnegie Mellon University Pittsburgh PA 15213 USA
5. Max Planck Institute for Intelligent Systems Stuttgart 70569 Germany