1. Department of Biomedical Engineering, National University of Singapore, 28 Medical Drive, #05-COR, Singapore 117456, Singapore.
2. Department of Electrical Engineering and Information Systems, The University of Tokyo, Tokyo 113-8656, Japan.
3. Department of Electrical and Computer Engineering, Faculty of Engineering, National University of Singapore, 4 Engineering Drive 3, #05-45, Singapore 117583, Singapore.
4. Thin-Film Device Laboratory, RIKEN, Saitama 351-0198, Japan.
5. Department of Biomedical Engineering, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA.