1. Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027, China
2. The Solid Mechanics Research Center, Beihang University (BUAA), Beijing 100191, China
3. Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
4. Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, Illinois 60208, USA