Progress towards melanin integration in bio-inspired devices.

The integration of biopolymers into hybrid electronics is one of the up to date issues in view of the achievement of fully bio-compatible devices. Among ‘hot topics’ in bio-polymer research, synthetic melanin or, briefly, “melanin”, has been recently recognized as a quite intriguing macromolecule thanks to its multifunctional optoelectronic properties. To date, melanin transport properties have been mainly enlightened on pellets, while optical absorption and conductivity properties have been investigated on melanin layers deposited on quartz and indium tin oxide/glass. The unavailability of suitable procedures to improve or promote adequate self assembling of melanin layer deposition onto substrate of interest in organic and solid state electronics (hybrid) like silicon substrates, prevent interesting studies on such structures. The reason stems basically on the difference between the hydrophilic nature of the melanin and the hydrophobic one of the supports (mostly of silicon). However, our group solved this issue and was able to tailor a melanin based metal/insulator/metal and metal/insulator/silicon structures, where synthetic melanin was embedded as the insulating part. This allowed to disclose interesting features related to data storage capabilities of melanin layers deposited on indium tin oxide/glass and silicon never investigated so far. In this work we show an overview on our recent mentioned results, and particular attention is paid on structures on silicon substrates. The use of pSi and nSi substrates and measurements under different environment conditions has enabled to gain insight into ambipolar electrical transport mechanisms, still unexplored. These results constitute a first important basic insight into melanin-based bio inspired structures and represent a significant step towards their integration in several kinds of hybrid organic polymer-based devices.