1. Nanofabrication Department, Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, 138634 Singapore
2. Department of Mechanical Engineering, Faculty of Engineering, National University of Singapore, 117575 Singapore
3. Pillar of Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
4. Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, China