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
6. McGowan Institute of Regenerative Medicine; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA