1. Department of Mechanical Engineering; College of Engineering, Ibaraki University; 1-12-1 Nakanarusawa Hitachi Ibaraki Japan
2. Department of Material-based Medical Engineering; Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University; 2-3-10 Kanda-Surugadai Chiyoda-ku Tokyo 101-0062 Japan