Biofilm distribution and performance of microfluidic microbial fuel cells with different microchannel geometries

Laminar-flow controlled microfluidic microbial fuel cells (MMFCs) with three different microchannel geometries, including the converging channel, the straight channel and the diverging channel, are presented and investigated. The biofilm distribution along the microchannel is visualized and compared. The effects of microchannel geometry on the start-up process and cell performance are also evaluated. The results show that the MMFC with the diverging channel (MMFC-D) begins to generate current in the shortest time compared with MFCs with the converging channel (MMFC-C) and the straight channel (MMFC-S). Moreover, the maximum power density (2447.7 ± 38.9 mW m−2) of MMFC-D is 429% and 24% higher than that of MMFC-C (462.7 ± 17.5 mW m−2) and MMFC-S (1980.1 ± 27.5 mW m−2), respectively. The high performance of MMFC-D can be explained by the combined effect of the good and uniform attached biofilm and the low anode resistance, which significantly depends on the microchannel geometry.