1. Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117585, Singapore.
2. Department of Biomedical Engineering, National University of Singapore, Singapore 117583, Singapore.
3. Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore.
4. Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA.