1. Division of Materials Science, Nara Institute of Science and Technology 1 , 8916-5 Takayamacho, Ikoma, Nara 630-0192, Japan
2. Department of Biomedical Engineering, National University of Singapore 2 , 4 Engineering Drive 3, Singapore 117583, Singapore
3. Center for Biosystems Dynamics Research (BDR), RIKEN 3 , 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan