Modular microbial fuel cells with all graphite microchannels for low internal resistance and high conversion efficiency

We present a new microbial fuel cell (MFC) design in which the microchannels are fabricated entirely from graphite. The microfluidic all-graphite MFC (μG-MFC) supports pure-culture Geobacter sulfurreducens electroactive biofilms (EABs). Iterative design reduced internal resistance and produced architecture-dependent performance gains. Narrow, unstructured channels yielded relatively high power and current densities, whereas a wide, micropillar-structured channel achieved the highest raw outputs, enabled by one of the lowest internal resistances reported for any microfluidic MFC (1.2 kΩ). This low resistance also produced record acetate conversion efficiency (82 %) and normalized energy recovery (0.83 kWh m −3 ), among microscale MFCs. To demonstrate modularity and system-level benefits, we ran multiple modules as stacks. This further reduced internal resistance to 480 Ω and enabled power and current increases to 700 μW and 1.5 mA, sufficient to power an environmental multi-sensor. We discuss scaling stacks up to thousands of modules as a means to provide a viable platform for low-cost remediation, with projected operating costs that are competitive with state-of-the-art wastewater treatment systems. • Designed and fabricated all-graphite μG-MFCs with varied microfluidic architectures. • Achieved the internal resistance (1.2 kΩ)—among the lowest for any microfluidic MFC. • Record efficiency and normalized energy recovery for a microfluidic MFC. • A three-unit μG-MFC stack delivered 700 μW power at 480 Ω internal resistance. • Sensor powered by stacked μG-MFC shows scalable, low-cost potential for remediation.