Integrated Microfluidic Flow-Through Microbial Fuel Cells

Abstract

This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm3 and a surface power density of 89.4 μW/cm2 using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time.

Overview of porous media/metal foam application in fuel cells and solar power systems

“…The feasibility of using graphene foam as an anode was also investigated. It was found that a graphene foam anode has increased electrochemical interactions and results in reducing bio-convertible substrate consumption, while maintaining a short response time [68].…”

Enhancement of the Start-Up Time for Microliter-Scale Microbial Fuel Cells (µMFCs) via the Surface Modification of Gold Electrodes

“…These structures help the mass transport by forming water channels. These cracks were also observed with the Shewanella oneidensis MR-1 biofilm grown on gold by Qian et al [ 8 ] and on graphene foam by Jiang et al [ 45 ]. These voids also lead to imperfect contact between the bacteria and the gold surface, causing a decrease in the electrical conductivity of the biofilm matrixes, which lowers the performance of the fuel cell, as suggested by other studies [ 49 , 50 , 51 ].…”

“…Bacteria usually prefer to adhere to carbon-based materials, but they are difficult to integrate in MEMS processes compared to gold as an electrode material. There are studies being conducted to adapt carbon-based electrodes to micro-scale MFCs [ 45 ], but their fabrication is not yet compatible with mass production solutions.…”

Electricity generation of a laminar-flow microbial fuel cell without any additional power supply

“…11 Jiang et al proposed a ow-through mMFC using 3D graphene foam as an anode, which had an estimated internal resistance of 7.3 kU. 12 Recently, micro MFCs without membranes, also called laminar-ow microbial fuel cells (LFMFCs), have attracted much attention, which contain a virtual barrier controlled by the co-laminar ow to separate the anolyte and catholyte. [13][14][15][16][17] The membrane-less structure can reduce both the fabrication cost and the internal resistance of the fuel cell.…”