1. Chongqing Key Laboratory of Oral Disease and Biomedical Sciences and Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education and Stomatological Hospital of Chongqing Medical University Chongqing 401174 P. R. China
2. Interdisciplinary Research Centre in Polymer Science and Technology (Polymer IRC) University of Bradford Bradford BD7 1DP UK
3. Biomedical and Electronics Engineering Department School of Engineering University of Bradford Bradford BD7 1DP UK
4. Division of Engineering in Medicine Department of Medicine Brigham and Women's Hospital Harvard Medical School Cambridge MA 02139 USA