1. Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027, China
2. Key Laboratory of Applied Mechanics, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
3. Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China
4. Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA