1. School of Materials Science and Engineering, Tongji University, Jiading, Shanghai 201804, P. R. China
2. National Institute of Shenzhen Advanced Medical Devices Co. LTD, Shenzhen 518110, P. R. China
3. Biomaterials R&D Center, Zhuhai Institute of Advanced Technology, Chinese Academy of Sciences, Zhuhai 519003, China
4. Department of Physics and Astronomy, California State University Northridge, Northridge, California 91330-8268, United States