1. Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
2. Silklab, Tufts University, 200 Boston Avenue, Medford, MA 02155, USA.
3. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA.
4. Department of Physics, Tufts University, 4 Colby Street, Medford, MA 02155, USA.