1. Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, P.R. China.
2. Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, P.R. China.
3. College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, P.R. China.
4. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China.
5. Department of Automation, Tsinghua University, Beijing 100084, P.R. China.
6. Querrey Simpson Institute for Bioelectronics, Northwestern University, Evanston, IL 60208, USA.
7. Departments of Civil & Environmental Engineering, Mechanical Engineering, and Materials Science & Engineering, Northwestern University, Evanston, IL 60208, USA.