1. Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, Massachusetts 02155, United States
2. Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, Massachusetts 02155, United States
3. Department of Physics, Tufts University, 4 Colby Street, Medford, Massachusetts 02155, United States
4. Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, N.W., Atlanta, Georgia 30332, United States
5. Air Force Research Laboratory, Materials and Manufacturing Directorate, Biotechnology Group, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States