1. Institute for Functional Intelligent Materials, National University of Singapore, Singapore, 117544, Singapore
2. Integrative Sciences and Engineering Programme, National University of Singapore, 119077, Singapore
3. Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, 2 Fusionopolis way, Singapore 138634, Singapore
4. Research Center for Functional Materials, National Institute for Materials, Science, Tsukuba, 305-0044, Japan
5. Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore