A High‐Performance Membraneless Microfluidic Microbial Fuel Cell for Stable, Long‐Term Benchtop Operation Under Strong Flow

Abstract

Strong control over experimental conditions in microfluidic channels provides a unique opportunity to study and optimize membraneless microbial fuel cells (MFCs), particularly with respect to the role of flow. However, improved performance and transferability of results to the wider MFC community require improvements to device stability under all applied operational conditions. To address these challenges, we present an easy-to-fabricate membraneless MFC that combines i) O 2 protection via a gas diffusion barrier, ii) integrated graphite electrodes, and iii) optimized electrode placement to avoid cross-contamination under all applied flow rates. Attention to all of these design features in the same platform resulted in the operation of a MFC with a pure-culture anaerobic Geobacter sulfurreducens biofilm for half a year, that is, six times longer than previously reported, without the use of an oxygen scavenger. As a result of higher device stability under high flow rates, power densities were four times higher than reported previously for microfluidic MFCs with the same biofilm.

Mainstreaming microfluidic microbial fuel cells: a biocompatible membrane grown in situ improves performance and versatility

“…A major hurdle for microfluidic MFCs is to prolong operational times. For example, previous studies used a membraneless MFCs with 6 mm electrode separation (the same design as used in this work) to achieve a 6 month operation, 15 which in another work enabled investigation into the problem of a developing power overshoot in mature MFCs. 16 Each new design modification should be evaluated from the perspective of operational longevity.…”

“…More details on electrode integration can be found elsewhere. 15 The final device volume was 10 μL, whereas the volume directly beneath a single electrode (equivalent to the anode chamber volume) was Vol anode = 1.4 μL. In this work special care was taken to limit any change in elevation relative to the PDMS top wall due to a protrusion or recession of the electrode to be less than 15 μm to promote predictable flow patterns during the membrane synthesis (ESI, † Fig.…”

“…However, in practice, anolyte/catholyte solution crossover can arise due to pump instabilities or during solution source replacement and other maintenance operations, especially as microfluidic MFCs have begun to support longer operational times. 15,16 Even under ideal flow conditions, simulations have shown that an electrode spacing of less than 4 mm can result in more than 10% of the inlet acetate concentration diffusing to the cathode. 15 Therefore, while often overlooked, solution crossover may present a major challenge in realizing the potential advantages of microfluidic MFCs, especially relative to devices fabricated with closely spaced electrodes.…”

“…15,16 Even under ideal flow conditions, simulations have shown that an electrode spacing of less than 4 mm can result in more than 10% of the inlet acetate concentration diffusing to the cathode. 15 Therefore, while often overlooked, solution crossover may present a major challenge in realizing the potential advantages of microfluidic MFCs, especially relative to devices fabricated with closely spaced electrodes.…”

Planar co‐laminar flow microbial fuel cell with flow‐through porous electrodes

“…9 Optimal electrode placement and the prevention of oxygen intrusion were proposed to ensure that the membrane-less MFC can operate stably for a long time. 10 One strategy to enhance the performance of microfluidic MFCs is to improve the anode material. 11 Anodes require high conductivity, large surface area, and good compatibility with microorganisms.…”