1. Department of Mechanical Engineering, National University of Singapore, Engineering Drive 3, Singapore 117576, Singapore
2. Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608, Singapore
3. Department of Electrical and Computer Engineering, National University of Singapore, Engineering Drive 3, Singapore 117576, Singapore
4. Nanoscience and Nanotechnology Initiative, National University of Singapore, Engineering Drive 3, Singapore 117576, Singapore