Optimal biofilm formation and power generation in a micro-sized microbial fuel cell (MFC)

Microbial fuel cells (MFCs) represent an emerging technology for generating electricity from renewable biomass. Micro-sized MFCs show promising applications in certain niche applications. However, existing micro-sized MFCs are generally limited by their low power density, rendering them insufficient for practical applications. Here, we report a micro-sized MFC having optimal biofilm formation and minimal oxygen invasion into its anode chamber to generate high power density. The biofilm formed by exoelectrogen, Geobacter sulfurreducens, was studied by using four different thicknesses of photo-definable polydimethylsiloxane (PDMS) spacer; 10, 20, 55, and 155 μm. Both current and power densities were significantly limited when the PDMS spacer was less than 55 μm thick. The maximum power density of our MFC was 95 μW/cm2, the highest value among previously reported micro-sized MFCs and even comparable to that of macro-scale counterparts.