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