1. Center for Biomedical Engineering, Brown University, Providence, Rhode Island 02912, USA
2. Draper, Cambridge, Massachusetts 02139, USA
3. Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island 02912, USA
4. Department of Orthopaedics, Brown University, Providence, Rhode Island 02912, USA
5. School of Engineering, Brown University, Providence, Rhode Island 02912, USA