1. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, China
2. Institute for Advanced Materials & Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
3. Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
4. Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
5. Department of Advanced Design and Systems Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China