Stacked all-graphite microfluidic microbial fuel cells

In this work, three high-surface-area graphite plates were structured by micromilling and incorporated directly microfluidic microbial fuel cells. All MFCs were run individually to verify their high-power outputs and substrate conversion efficiencies. Then the MFCs grew electroactive biofilms with an average 35 µm thickness. They were connected in different stacked configurations to increase raw outputs. In a parallel configuration, the internal resistance was as low as 480 Ω, resulting in outputs in power (595 µW) and current (1.4 mA), which are impressive by microfluidic standards. Adjusting the flow conditions enabled the parallel stack to reach over 70% acetate utilization. A series stack was used to successfully power an environmental multisensor (temperature, humidity) and a wristwatch. We discuss staked systems that could reproduce the results of an 850 L pilot MFC system.