1. Research Center of Smart Wearable TechnologyInstitute of Textiles and ClothingThe Hong Kong Polytechnic University Hong Kong 999077 P. R. China
2. College of Professional and Continuing EducationThe Hong Kong Polytechnic University Hong Kong 999077 P. R. China
3. The Alan G. MacDiarmid NanoTech InstituteThe University of Texas at Dallas Richardson TX 75080 USA