A biomembrane grown in situ for improved microfluidic microbial fuel cell performance using a pure culture Geobacter sulfurreducens electroactive biofilm

Microfluidic microbial fuel cells (MFCs) hold great potential to reproduce core functions of bulk MFCs for study and optimization under precise conditions. Unlike most MFC types, those in a microfluidic format typically do not use a membrane to separate anode and cathode compartments, relying instead on the physics of laminar flow to maintain isolation of independent liquid streams. This lowers cost, device complexity, and should reduce internal resistance. However, to avoid solution crossover, which is likely to occur due to inevitable instabilities during long operational times, authors often separate electrodes by distances of several millimeters or more. This reverses benefits on internal resistance, undermining a prime advantage of microfluidic MFCs. This work demonstrates a facile method for the in-situ synthesis of a microscale membrane, supporting sub-milimeter electrode spacing. The membrane added only 68.5 Ω to the cell internal resistance and its synthesis resulted in no measurable changes to Rct at either electrode. However, the method to grow the membrane after device synthesis greatly reduced complexity in device fabrication. Overall, the reduced electrode spacing that was facilitated by the membrane lowered internal resistance from 25 k to 10 k and provide stable operation even under non-ideal flow conditions. Compared to a state-of-the-art membraneless MFC with 6 mm electrode spacing, the membrane MFC provided approximately 45% higher power density, 290% higher current density and 7 times higher acetate conversation efficiency. Membrane-enhanced flow stability also delivered continuous increases to power density with increased flow rate over baseline levels, rising to 30% higher for flow rate increases of 100 times.