1. Department of Mechanical EngineeringCollege of EngineeringCity University of Hong Kong Tat Chee Avenue, Kowloon Tong Kowloon Hong Kong SAR China
2. CAS Center for Excellence in NanoscienceBeijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences Beijing 100083 P. R. China
3. School of Nanoscience and TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
4. College of Mechatronics and Control EngineeringShenzhen University Nanhai Avenue 3688 Shenzhen 518060 P. R. China
5. Department of Mechanical Engineering and Materials ScienceYale University New Haven CT 06520 USA
6. Department of Materials Science and EngineeringCollege of EngineeringCity University of Hong Kong Tat Chee Avenue, Kowloon Tong Kowloon Hong Kong SAR China