1. Center for Nanofibers and Nanotechnology Lab; Department of Mechanical Engineering; National University of Singapore; 9 Engineering Drive 1 Singapore 117581 Singapore
2. Current Address: Institute of Chemical and Engineering Sciences (A*STAR); 1 Pesek Road; Jurong Island Singapore 627833 Singapore
3. Current Address: Technology Development Centre; Institute of Technical Education; ITE College East 10 Simei Avenue, Singapore 486047 Singapore
4. National University of Singapore; Nanoscience and Nanotechnology Initiative (NUSNNI); 2 Engineering Drive 3 Singapore 117576 Singapore