1. School of Chemical and Biomedical Engineering and Center for Advanced Bionanosystems, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Center for Composite Materials, School of Astronautics, Harbin Institute of Technology, P.O. Box 3010, Harbin 150001, P.R. China, and School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798