Towards bioelectronics: Charge carrier transport properties and structure of eumelanin thin films

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The pigment melanin, which can be found in many plants, animals, human skin, hair, eyes, and brain, has properties similar to a semiconductor. It absorbs strongly visible and UV light, enabling it to protect our body from sunlight. It also conducts charges, whereas its conductivity depends strongly on humidity and temperature. It is still not well understood which type of charge carriers, ions or electrons, is transported and what is the underlying mechanism. We will fabricate the first melanin field-effect transistors to address these questions. This configuration will allow us to determine the dominating charge carriers and to characterize the electrical properties of melanin thin films in detail. Additionally, the growth and structure of melanin films will be studied on a nanometer scale to relate electrical properties to the organization of melanin molecules, another issue disputed in literature. Melanin's semiconducting properties combined with its stability and biological nature make it very interesting for applications like UV-protective films, chemical sensors and solar cells. A better understanding of melanin's physical properties will pave the way for these applications. Research on functional biomolecules like melanin has the potential to result in environmentally friendly, bio-degradable technology and medical devices compatible with the environment of human body.