1. John A. Paulson School of Engineering and Applied Sciences Harvard University 29 Oxford St Cambridge MA 02138 USA
2. Department of Chemistry and Chemical Biology Harvard University 12 Oxford St. Cambridge MA 02138 USA
3. Kavli Institute for Bionano Science and Technology Harvard University 29 Oxford Street Cambridge MA 02138 USA
4. State Key Laboratory for Strength and Vibration of Mechanical Structure School of Aerospace Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China
5. Wyss Institute of Biologically Inspired Engineering 60 Oxford St. Cambridge MA 02138 USA