Bio-fuel cells are suitable power sources to implement in electronic contact lenses. The power needed for smart lenses is generated by converting in situ available chemical energy from different biofuels presented in human tears into electric energy. Here we show different approaches that our group has developed to design high performing and transparent conventional enzymatic fuel cells  and self-charging chemical biosupercapacitors [2, 3] for contact lens application (Fig. 1A).
Bio-solar cells, i.e. devices based on biocatalysts, which can directly transform solar energy into electric energy, are in the spotlight nowadays. Here we show the very first solar biosupercapacitor (Fig. 1B), which is built from transparent and nanostructured, i.e. highly capacitive, indium tin oxide based electrodes . The biodevice is able to convert solar energy into electric energy, which is capacitively stored within the same volume used for conversion. The solar biosupercapacitor, consisting of thylakoid membrane modified anode and bilirubin oxidase modified cathode ionically coupled in a closed system at neutral pH, is charged by the ambient daylight. Because of the materials used, the resulting biodevice is a simple to build, inexpensive, and sustainable power source for low-power low-voltage electronics.
Fig. 1. Transparent biological power sources.
(A) Charge-storing glucose/oxygen fuel cell. (B) Self-charging solar biosupercapacitor.
This work has been financially supported by the European Commission (PEOPLE-2013-ITN-607793).
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