Eumelanin-Based Organic Bioelectronics: Myth or Reality?

Eumelanins, the black insol. pigments of human skin, eyes and substantia nigra (neuromelanin)​, stand today as a unique source of inspiration for the design and implementation of soft biocompatible multifunctional materials for bio-​optoelectronic devices. Interest in eumelanins stems from bioavailability, biocompatibility and a peculiar set of physicochem. properties, i.e. broadband absorption in the UV-​visible range, intrinsic free radical character, water-​dependent hybrid ionic-​electronic conductor behavior, supporting optimistic feelings about a possible rise of eumelanin-​mimics as innovative bioinspired solns. for org. bioelectronics. However, a no. of conceptual and technol. gaps still hinder a rapid progress of melanin-​based org. electronics and bioelectronics, including in particular the limited contribution of electronic cond. and current decay with time under biasing. Herein, we provide a concise overview of the structural and optoelectronic properties of melanins with a view to bringing to focus main issues and challenges en route to bioelectronic applications.