1. Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA
2. Institute for Computational and Mathematical Engineering, Stanford University, Stanford, California 94305, USA
3. Department of Physics, Stanford University, Stanford, California 94305, USA
4. Symbolic Systems, Stanford University, Stanford, California 94305, USA
5. U.S. Army Research Lab, 2800 Powder Mill Road, Adelphi, Maryland 20783, USA
6. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA