1. Research Centre for Smart Wearable TechnologyInstitute of Textiles and ClothingHong Kong Polytechnic University Hong Kong 999077 China
2. School of Electronic and Information EngineeringSouthern China University of Technology Guangzhou 510640 Guangdong China
3. i‐LabSuzhou Institute of Nano‐Tech and Nano‐BionicsChinese Academy of Sciences Suzhou 215123 China
4. Department of Applied PhysicsHong Kong Polytechnic University Hong Kong 999077 China