1. Department of Mechanical Engineering, Massachusetts Institute of Technology, 500 Technology Square, Room NE47-321, Cambridge, MA 02139, USA.
2. Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138, USA.
3. John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
4. Department of Biological Engineering, Massachusetts Institute of Technology, 500 Technology Square, Room NE47-321, Cambridge, MA 02139, USA.
5. BioSystems and Micromechanics (BioSyM) IRG, Singapore-MIT Alliance for Research and Technology, Singapore, Singapore.