1. Institute of Materials Research and Engineering (IMRE); Agency for Science, Technology and Research (A*STAR); 2 Fusionopolis Way, Innovis, #08-03 138634 Singapore
2. School of Electrical and Electronics Engineering; Nanyang Technological University; 50 Nanyang Avenue 639798 Singapore
3. Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences; Nanyang Technological University; 637371 Singapore
4. Department of Mechanical Engineering; National University of Singapore; 21 Lower Kent Ridge Road 119077 Singapore