1. Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University; Beijing 100191 China
2. Department of Civil Engineering-Engineering Mechanics; University of Arizona; Tucson Arizona 85721
3. Key Laboratory of Advanced Materials of Ministry of Education of China, Tsinghua University; Beijing 100084 China
4. Department of Biomedical Materials and Engineering; Graduate School of Dental Medicine, Hokkaido University; Sapporo 060-8586 Japan