1. Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA
2. Photonics Center, Boston University, Boston, MA 02215, USA
3. Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
4. Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
5. Department of Biomedical Engineering, Polytechnic University of Puerto Rico, San Juan 00918, Puerto Rico
6. Harvard-MIT Program in Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
7. Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215, USA
8. Department of Physics, Boston University, Boston, MA 02215, USA