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. Dipartimento di Fisica Università degli Studi di Pavia via A. Bassi 6 27100 Pavia Italy
4. Department of Physics Tufts University 4 Colby Street Medford MA 02155 USA