1. Mechanical Engineering Department Massachusetts Institute of Technology Cambridge MA 02139 USA
2. Department of Mechanical Engineering The University of Tokyo Tokyo 113‐8654 Japan
3. United States Air Force Research Lab Wright‐Patterson Air Force Base Wright‐Patterson AFB OH 45433 USA
4. Center for Surgery and Public Health Brigham and Women's Hospital‐Harvard Medical School Boston MA 02115 USA
5. John A. Paulson School of Engineering and Applied Science Harvard University Cambridge MA 02138 USA