1. Department of Mechanical and Aerospace Engineering; The Hong Kong University of Science and Technology; Clear Water Bay, Kowloon Hong Kong China
2. Key Lab of Advanced Technologies of Materials; Ministry of Education; School of Materials Science and Engineering; Southwest Jiaotong University; Chengdu 610031 China
3. Department of Materials Science and Engineering; University of Illinois at Urbana-Champaign; Urbana Illinois 61801
4. National Engineering Research Center for Biomaterials, Sichuan University; Chengdu 610064 China