1. Department of Biomedical Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, China
2. Division of Engineering in Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA, 02139, USA
3. Strasbourg Institute of Physics and Chemistry of Materials, University of Strasbourg, 67034 Strasbourg cedex, France
4. Biophysics Group, Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
5. UCL Healthcare Biomagnetics and Nanomaterials Laboratories, 21 Albemarle Street, London W1S 4BS, UK