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

Abstract

Recent trends in microfluidic microbial fuel cells (MFCs) is to exclude a separation membrane, instead relying on the physics of laminar flow to maintain isolation between anode and cathode compartments....

Microfluidic membraneless microbial fuel cells: new protocols for record power densities

“…After 75 days of total operation (approximately one month under the R ext = 15 kΩ external load), the continuous power at Q T = 1.0 mL h −1 had increased to 2.47 W m −2 . This value is significantly higher than that from the previously highest performing microfluidic MFC containing a pure-culture G. sulfurreducens EAB 25 and matched the highest reported power density from the best performing graphite-electrode microfluidic MFC (2.45 W m −2 ), even though the previous work used higher flow rates ( Q T = 20 mL h −1 ) and a mixed species–species (EAB). 5 We refer the reader to previous work where a mature biofilm was imaged by scanning electron microscopy after 6 months in an unmodified membraneless MFC.…”

Optimized design and protocols eliminate power density gap between microbial fuel cells at different scales

“…After 75 days of total operation (approximately one month under the Rext=15 kΩ external load), the continuous power at QT=1.0 mL h -1 had increased to 2.47 W m -2 . This value is significantly higher than that from the previously highest performing microfluidic MFC containing a pure-culture G. sulfurreducens EAB 25 and matched the highest reported power density from the best performing graphite-electrode microfluidic MFC (2.45 W m -2 ), even though the previous work used higher flow rates (QT=20 mL h -1 ) and a mixed species-species (EAB). 5 To test the upper limits of the output of our new design, we collected polarization curves under increasing flow rates.…”

“…The inverse relationship between PVCR and QT in opposition to areal power densities because improvements to raw power at high flow rates provide diminishing returns after de-acidification and mass transport are maximized. Considering that the results from a previous report were collected at a wider range of flow rates, 25 it is apparent that PVRC and IVCR improve at lower flow rates, in that case reaching PVCR=2.12 mW L -1 d (NER=0.051 kWh m -3 ) and Δ[Ac]=1.5 mM at QT=0.1 mL h -1 . We compared this previous PVCR value with that from the present study by extrapolation to QT=0.1 mL h -1 with an empirical fitting function (see Figure 6) and found that the VCR-normalized power in our study could have been as high as PVCR=8.71 mW L -1 d (NER=0.209 kWh m -3 ), which is close to the average value for larger acetatefed mixed-species MFCs, i.e., PVCR=10.42 mW L -1 (NER=0.250 kWh m -3 ).…”

“…[18][19][20][21] While certain elements of this experimental design philosophy is shared with previously developed bioelectrochemical systems (BES) using three-electrodes, 15,[22][23][24] the challenges in two-electrode membraneless MFCs are more pronounced due to the requirement for stable laminar co-flow and the related electrode design. 2,11,25 Moreover, compared to other microfluidic applications, the sensitive nature of electroactive biofilms (EABs) at the heart of MFC technology place stronger demands on device reliability.…”

Recent progress in microbial fuel cells using substrates from diverse sources

“…We anticipate the incorporation of more micro-scale MFC features will be an avenue to future development. For now, fully microfluidic systems have been the subject of significant development as tools for better understand fundamental aspects of electroactive biofilms [ 74 , 290 , 291 , 292 ] as well as toward practical considerations including fine-tuning of electrode spacing, hydrodynamic effects, and the associated resistance distribution [ 293 , 294 , 295 , 296 ]. Moreover, it is anticipated that certain micro- and milli-fluidic elements can be integrated into otherwise large-scale MFC systems.…”