1. Research Institution for Biomimetics and Soft Matter; Fujian Key Provincial Laboratory for Soft Functional Materials Research; Xiamen University; 422 Siming Nan Road Xiamen 361005 P. R. China
2. Key laboratory of Textile Science and Technology; Ministry of Education; College of Textiles; Donghua University; Shanghai 201620 P. R. China
3. Department of Physics; National University of Singapore; 2 Science Drive 3 Singapore 117542