1. Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, #04-08, Singapore 117583, Singapore;
2. Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, #07-08, Singapore 117575, Singapore e-mail:
3. Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, #04-08, Singapore 117583, Singapore e-mail: