1. School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue 639798, Singapore
2. Particle Characterization Laboratories, Inc., 845 Olive Ave, Suite A, Novato, California 94945, United States
3. Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive 637553, Singapore
4. School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive 637459, Singapore