Exploring the use of cost-effective membrane materials for Microbial Fuel Cell based sensors

Microbial fuel cells show great potential as a self-powered, real time and on-site technology for monitoring the labile organic carbon content (e.g. Biochemical Oxygen Demand, BOD) in water systems. By drastically reducing their cost of manufacture, MFCs can become an important tool for water quality monitoring, accessible also in the poorest and most remote areas of the world. To enable this, this study investigates for the first time the use of two low cost membrane materials: a natural polymer (eggshell membrane), and a synthetic polymer (polydimethylsiloxane, PDMS). The energy generation and sensing capability of the resulting devices were compared with a membrane-less device, while the well-known Nafion® membrane was used as a control. For each device, the effect of electrode spacing on performance was also investigated. The use of PDMS led to a power density similar to the case of the much more expensive Nafion® membrane. The electrode spacing affected the output power, but it had a negligible effect on the BOD sensing capability of the devices. In particular, for the case of the eggshell membrane and the membrane-less devices, the higher the electrode spacing the better the power performance. The opposite trend was observed when a synthetic membrane was used. Finally, although more unstable than the other devices, the eggshell membrane devices were associated with the lowest internal resistances and the highest sensitivity. In conclusion, this study not only demonstrates the use of inexpensive membranes in MFCs, but it also provides guidelines on design, in terms of electrode spacing and cross-sectional area, according to the material used.