1. Department of Engineering Mechanics; Center for Flexible Electronics Technology, Applied Mechanics Laboratory, Tsinghua University, Beijing 100084, P. R. China
2. State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, P. R. China
3. College of Civil Engineering and Transportation, South China University of Technology, Guangzhou, P. R. China