1. Department of Medical Sciences, Graduate School of Medicine, Korea University, Seoul, South Korea
2. Department of Mechanical Engineering, Hanbat National University, Daejeon, South Korea
3. Department of Mechanical Engineering and Engineering Science, Department of Biological Sciences, Center for Biomedical Engineering and Science, Nanoscale Science Program, University of North Carolina at Charlotte, North Carolina 28223, USA
4. Department of Neurosurgery, Guro Hospital, College of Medicine, Korea University, Seoul, South Korea