1. Materials Science and Engineering Program, University of California San Diego, La Jolla, CA 92093–0418, USA.
2. Department of Structural Engineering, University of California San Diego, La Jolla, CA 92161, USA.
3. Department of NanoEngineering, University of California San Diego, La Jolla, CA 92093–0448, USA.
4. Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA.
5. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, P. R. China.
6. Department of Ophthalmology and Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
7. The Key Laboratory of Materials Processing and Mold of Ministry of Education, School of Materials Science and Engineering, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450001, P. R. China.
8. Department of Mathematics, University of California San Diego, La Jolla, CA 92093, USA.
9. Department of Physics, University of California San Diego, La Jolla, CA 92093, USA.