1. Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
2. Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
3. Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 101400, People's Republic of China
4. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA