1. Silklab, Department of Biomedical Engineering, Tufts University, Medford, Massachusetts 02155, United States
2. Department of Physics, Tufts University, Medford, Massachusetts 02155, United States
3. Laboratory for Living Devices, Tufts University, Medford, Massachusetts 02155, United States
4. Department of Electrical and Computer Engineering, Tufts University, Medford, Massachusetts 02155, United States