1. Instituto de Engenharia de Sistemas E Computadores-Microsistemas e Nanotecnologias (INESC MN) and IN-Institute of Nanoscience and Nanotechnology, Rua Alves Redol, 9, 1000-029 Lisbon, Portugal
2. Department of Bioengineering, Instituto Superior Técnico, University of Lisbon, Lisbon 1049-001, Portugal