In situ visualization of biofilm formation in a microchannel for a microfluidic microbial fuel cell anode

A novel in situ approach is proposed to visualize biofilm formation in the microchannel for the microfluidic microbial fuel cell (MMFC) anode, which could reflect a more precise biofilm formation during start-up process in real-time. A microchannel reactor was designed and fabricated based on a transparent indium-tin-oxide (ITO) conductive membrane. In situ visualization of biofilm formation under various anolyte flow rates was captured by a phase contrast microscope combined with a custom long working distance objective. The results show that no steady biofilm is formed on the surface of anode under low flow rate of 50 mL min-1 because of the insufficient nutrient supply. With increasing the anolyte flow rate, more attached bacteria on the anode surface and denser biofilm are observed in the microchannel. Less bacteria are attached on the surface of anode along flow direction due to the entrance effect. However, denser biofilm leads to larger mass transfer resistance of the anolyte and product in biofilm. Therefore, a superior bioelectrochemical performance is yielded for the biofilm formed under a moderate flow rate during start-up process. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.