1. Department of Applied Physics, National Technical University of Athens, 15780 Athens, Greece
2. Department of Biomedical Engineering, The University of West Attica, 12243 Athens, Greece
3. Microelectronics Research Group (MRG), Institute of Electronic Structure and Laser (IESL), Foundation of Research & Technology Hellas (FORTH), 70013 Heraklion, Greece
4. Biomedical Research Foundation of the Academy of Athens, 11527 Athens, Greece