1. Department of Mechanical Engineering, University of California, Merced, California 95343, United States
2. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
3. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
4. Department of Chemical and Materials Engineering, New Jersey Institute of Technology, Newark 07102, United States
5. Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States