PrefaceThis book contains the abstracts and full papers presented at the IEEE 4th Portuguese Meeting on Bioengineering (ENBENG) organized by the IEEE Engineering in Medicine & Biology Society (EMBS) Chapter of the IEEE Portugal Section that was held in "Atmosfera m", in the city of Porto, between 26th and 28th, February of 2015.The Portuguese Meeting on Bioengineering is one of most important meetings organized in Portugal related with the Bioengineering field and where students and researchers present and discuss the preeminent work developed in Portugal in the field. The meeting has been organized since 2011: the first was held in Lisbon, in 2011; the second in Coimbra, in 2012; and the third occurred in Braga, in 2013.ENBENG2015 had 107 works submitted, from which 52 were accepted for oral presentations distributed by 10 sessions, and 31 as posters. The submissions involved authors from several Portuguese Institutions, which shows the importance of the Bioengineering and Biomedical Engineering in Portugal nowadays. Additionally, 9 submissions were from foreign countries. The received contributions address several topics related to Bioengineering, including Biomaterials, Nanobiotechnology,