Interfaces and Charge Transport in Melanin Thin Films and Devices

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The need to limit the waste electrical and electronic equipment (WEEE) worldwide, the interest in developing a "ubiquitous sensor network", the requirement for an improved biocompatibility between medical implants and living tissues call for a thorough study of natural materials, environmentally and human friendly, abundant and available at low-cost. Within this context, the pigment melanin is an attractive candidate. Melanin is ubiquitous in flora and fauna. As an example, it can be found in human skin, hair, eyes, inner ear and brain. Eumelanin, the most studied of all classes of melanin, has numerous functions that include photoprotection, metal chelation, antioxidant behavior and free radical scavenging. Eumelanin is also involved in the development of melanoma skin cancer and Parkinson's disease. Apart from its importance in biology and medicine, eumelanin has been investigated by physicists and materials scientists because of its physicochemical properties, e.g. photoconductivity and hydration-dependent conductivity. These properties, together with biocompatibility, biodegradability and extraordinary thermal and photostability, indicate the great potential of eumelanin for technological applications. Despite impressive progress done in the processing of eumelanin - notoriously poorly soluble in all solvents - in film form, major hurdles have to be overcome to advance the understanding of the eumelanin functional properties and to exploit its technological potential. Aspects pertaining to the ill-defined macro and supramolecular structure of the pigment as well as to charge transfer and transport properties are yet to be fully understood. The research program I propose in this Discovery grant aims at advancing the knowledge on electronic and ionic transport in eumelanin films as related to their structure. I will adopt a holistic approach, including chemical, structural, redox, electronic and ionic contributions, which I believe it is the ideal platform to study complex natural materials whose behavior is dramatically influenced by external factors (e.g. composition of the atmosphere or presence of salts). The interdisciplinarity of the research will permit to train versatile highly qualified personnel, real "problem solvers" capable of facing the grand challenges of our modern times. My research will generate guidelines to build extended structure-property relationships in melanin and other classes of natural materials for environmentally benign electronics and bioelectronics, e.g. biocompatible and biodegradable supercapacitors for energy storage, chemo- and biosensors, implantable neurological electrodes with improved biocompatibility and will advance the understanding of the functional properties of eumelanin in biological systems.