Microfluidic Microbial Fuel Cell Research Articles

Interrelationship of Electric Double Layer Theory and Microfluidic Microbial Fuel Cells: A Review of Theoretical Foundations and Implications for Performance

Microbial fuel cells and their related microfluidic systems have emerged as promising greener energy alternatives for the exploitation of avenues related to combined power and wastewater treatment operations. Moreover, the potential for their application in biosensing technology is large. However, while the fundamental principles of science that govern the design and operation of microbial fuel cells (MFCs) and microfluidic microbial fuel cells (MMFCs) are similar to those found in colloid science, the literature shows that current research lacks sufficient reference to the electrostatic and electrokinetic aspects, focusing mostly on aspects related to the architecture, design, anodes, microbial growth and metabolism, and electron transfer mechanisms. In this regard, research is yet to consider MFCs and MMFCs in the context of electrostatic and electrokinetic aspects. In this extensive review, we show, for the first time, the interrelationship of MFCs and MMFCs with electric double layer theory. Consequently, we show how the analytical solution to the mean field Poisson–Boltzmann theory relates to these systems. Moreover, we show the interrelationship between MFC and MMFCs’ performance and the electric double layer and the associated electrostatic and electrokinetic phenomena. This extensive review will likely motivate research in this direction.

Influence of shear stress on electroactive biofilm characteristics and performance in microbial fuel cells

This study has provided comprehensive insights into the intricate relationship between shear stress and the development, structure, and functionality of electroactive biofilms in Microbial Fuel Cells (MFCs). A multichannel microfluidic MFC reactors that created specific shear stress on the anode, were designed for the simultaneous study of multiple flow conditions using the same medium. Then, the evolution of the biofilm growth under different shear stress conditions (1, 5 and 10 mPa) were compared. The taxonomic and functional structure was studied by 16S rRNA gene and metagenomic sequencing and the physical biofilm characteristics were measured via fluorescence microscopy. The results demonstrate the pivotal role of shear stress in influencing the growth kinetics, electrical performance, and physical structure of anodic biofilms. Notably, the selection of specific EAB was observed to be shear stress-dependent, with a marked increase in specific EAB abundance as shear stress increased. The power density, while not directly correlated with the relative abundance of specific or nonspecific EAB, exhibited a strong linear relationship with biofilm coverage. This suggests that factors beyond the microbial composition, potentially including mass transport or electrochemical conditions, might be instrumental in determining electricity production. The functional metagenomic analysis further highlighted the complexities of extracellular electron transfer (EET) mechanisms in electroactive biofilm. While certain genes associated with EET in known species such as Geobacter and Shewanella were identified, the study also examined the limitations of solely relying on genetic markers to infer EET capabilities, emphasizing the need for complementary metaproteomic analyses. This study demonstrates the multifaceted impact of shear stress on electroactive biofilm and paves the way for future investigations aimed at harnessing the potential of electroactive biofilms in microbial fuel cell applications.

Evaluation and optimization of the Zn-based microfluidic microbial fuel cells to power various electronic devices

As an actual application, Zn-based microfluidic microbial fuel cells (MFCs) were investigated based on microchannel length and substrate flow rate in a straight geometry to power a variety of electronic devices. According to the statistical analysis based on response surface methodology (RSM), these parameters and their interactions are significant contributors to the system power generation. Based on the RSM, the optimum condition was determined to maximize the generated power density. A single optimized microfluidic MFC cell produced an open circuit potential (OCP) of 1.295 V and an output power density and current density of 21111 W m-3 and 140000 A m-3, respectively. In terms of bioelectrical characteristics, these are the highest values yet achieved by microfluidic MFCs. Several series and parallel configurations of the optimized cells were tested to demonstrate that they can provide sufficient power to a mechanical desktop clock, a digital alarm clock thermometer, and a coreless motor without using voltage or current boosters.

Boosting microfluidic microbial fuel cells performance via investigating electron transfer mechanisms, metal-based electrodes, and magnetic field effect.

The presented paper fundamentally investigates the influence of different electron transfer mechanisms, various metal-based electrodes, and a static magnetic field on the overall performance of microfluidic microbial fuel cells (MFCs) for the first time to improve the generated bioelectricity. To do so, as the anode of microfluidic MFCs, zinc, aluminum, tin, copper, and nickel were thoroughly investigated. Two types of bacteria, Escherichia coli and Shewanella oneidensis MR-1, were used as biocatalysts to compare the different electron transfer mechanisms. Interaction between the anode and microorganisms was assessed. Finally, the potential of applying a static magnetic field to maximize the generated power was evaluated. For zinc anode, the maximum open circuit potential, current density, and power density of 1.39 V, 138,181 mA m-2 and 35,294 mW m-2 were obtained, respectively. The produced current density is at least 445% better than the values obtained in previously published studies so far. The microfluidic MFCs were successfully used to power ultraviolet light-emitting diodes (UV-LEDs) for medical and clinical applications to elucidate their application as micro-sized power generators for implantable medical devices.

Co-laminar Microfluidic Microbial Fuel Cell Integrated with Electrophoretically Deposited Carbon Nanotube Flow-Over Electrode

Co-laminar Microfluidic Microbial Fuel Cell Integrated with Electrophoretically Deposited Carbon Nanotube Flow-Over Electrode

Bacteria‐driven Single‐inlet Microfluidic Fuel Cell with Spiral Channel Configuration

AbstractWe present a single inlet, spiral‐shaped microfluidic microbial fuel cell (MFC) with porous Paper@Ni anode and Paper@C cathode for energy generation. In the MFC, the anode with a bacterial component is placed along the microchannel side to provide a larger electrode surface area, reduced internal resistance, and enhances mass transport of the 2 % glucose as a substrate for microbial redox reaction. The large electrode area induced by the spiral channel configuration and passive control of the boundary layer enhances the energy output from the fuel cell and eliminates the need for a two‐chambered system. The fuel cell utilizes bacteria Bacillus stratosphericus isolated from mangrove soil to generate bioenergy with an open‐circuit voltage of 0.3 V within 10 seconds. The fuel cell generates a maximum current density of 7 A m−2 and a power density of ∼ 150 mW m−2.

A comparative study of three types of anode electrodes in a microfluidic microbial fuel cell

Microbial fuel cells (MFCs) are innovative bioelectrochemical approaches for the natural conversion of organic resources into energy based on the metabolic activities of inoculated bacteria that serve as biocatalysts. The main objective of the present study was to examine the effect of zinc foil modified with zinc oxide as a novel anode material to enhance power generation in a microfluidic MFC using oxalate as a substrate. X-ray diffraction and FE-SEM analyses were done for nanostructure confirmation and to understand the morphology of a zinc oxide-coated electrode. The microfluidic MFC performance was investigated and compared with a zinc foil and zinc foil linked stainless steel mesh through an external circuit. The experimental results expressed that the zinc foil, zinc foil externally linked stainless steel, and modified zinc foil as anode electrodes achieved the maximum power density of 2980 W m-3, 1080 W m-3, and 428 W m-3, respectively. The results demonstrated that the zinc oxide nanorods could not act as an effective avenue for improving the microfluidic MFC performance.

Origami Microfluidic Microbial Fuel Cell for Powering Iot Node with Iot Cloud Platform

Microbial fuel cells (MFCs) are bio-electrochemical devices that produce electrical current from the electrochemically active bacteria (EABs). These bacteria generate the electrons from the degraded organic matter and harness renewable and pollution-free energy in a self-sustaining manner. Due to its user-friendly architecture, neutral pH, simple operating conditions and amenability to integrate with the on-chip technology, MFCs are the economical and convenient alternative to conventional power sources. Since the first development of MFC, an ample amount of studies have been reported especially to harness new bacteria types, inoculation protocols, and cell and bioelectrode fabrication methodologies. As a result, several MFCs have been successfully developed as a biosensor and power hub by utilizing various fluid resources, such as domestic and industrial wastewater, urine, and soiled water from sewage. However, in order to be commercially viable, the device architecture and size of the MFCs become the essential parameter for power generation, which decides the potential application. In this context, several micro-scale MFC architectures have been proposed. Among these, the paper-based microfluidic fuel cell technology has drawn remarkable attention due to its inexpensive and inherent fluid flow capillary action properties. In addition, wide array (series/parallel) configurations have been incorporated to further enhance the power output.With these MFCs, a extensive range of applications, such as powering LEDs, digital thermometer, wireless, sensors, radio nodes etc., have been successfully demonstrated. With this flexibility and unique features, paper-based MFCs have the ability to monitor the on-field parameter (temperature, humidity, hazardous gas etc.) using the Internet of Things (IoT) cloud network. Currently, The Internet of Things (IoT) technology is the most popular technology in the field of wireless data transmission with IoT cloud. It connects various devices and their protocols over internet infrastructure which can be monitored, analyzed, and controlled remotely over the internet. It has an immense application in the field of healthcare, agriculture, automotive, and remote sensing sectors.In this study, as a proof of concept, the Shewanella putrefaciens powered stacked origami MFCs have been demonstrated to drive an ultra-low-power (ULP) IoT node to measure the on-field ambient temperature and transmit corresponding data to a mobile phone. The IoT node requires 2.5–3.3 volt for proper operation, therefore a DC-DC booster was used just after the fuel cell to step-up the low voltage. This step-up voltage was further stored in the supercapacitor to supply power to the IoT node in case of a high current requirement. Finally, after powering the IoT node, it sends the temperature data over low-power Bluetooth low energy (BLE) that can be observed by any smartphone supporting Bluetooth 4.0 and nRF connect android app. The detailed stepwise integrated block diagram from MFC to a mobile phone has been displayed in Figure 1. The proposed approach offers autonomous environmental monitoring using paper-based MFC as a viable substitute for conventional power sources. Figure 1: Block diagram of complete setup MFCs powering IoT node which communicates to smartphone and IoT cloud servers Figure 1

In situ visualization of biofilm formation in a microchannel for a microfluidic microbial fuel cell anode

A novel in situ approach is proposed to visualize biofilm formation in the microchannel for the microfluidic microbial fuel cell (MMFC) anode, which could reflect a more precise biofilm formation during start-up process in real-time. A microchannel reactor was designed and fabricated based on a transparent indium-tin-oxide (ITO) conductive membrane. In situ visualization of biofilm formation under various anolyte flow rates was captured by a phase contrast microscope combined with a custom long working distance objective. The results show that no steady biofilm is formed on the surface of anode under low flow rate of 50 μL min−1 because of the insufficient nutrient supply. With increasing the anolyte flow rate, more attached bacteria on the anode surface and denser biofilm are observed in the microchannel. Less bacteria are attached on the surface of anode along flow direction due to the entrance effect. However, denser biofilm leads to larger mass transfer resistance of the anolyte and product in biofilm. Therefore, a superior bioelectrochemical performance is yielded for the biofilm formed under a moderate flow rate during start-up process.

Front Cover: A High‐Performance Membraneless Microfluidic Microbial Fuel Cell for Stable, Long‐Term Benchtop Operation Under Strong Flow (ChemElectroChem 10/2020)

The Front Cover shows a real microfluidic microbial fuel cell (MFC) used in this study. Three graphical elements are superimposed to highlight critical design enhancements over previous literature examples. These include an oxygen protection barrier, embedded graphite electrodes for robust operation and faster redox kinetics, as well as computer simulations to reduce anolyte/catholyte cross-over to the opposite electrode. Bringing these improvements together into the same platform offers new opportunities to bridge the gap between the micro- and macro-MFC studies. More information can be found in the Article by M. A. Amirdehi et al.

The coupled microfluidic microbial electrochemical cell as a self-powered biohydrogen generator

Due to the importance of hydrogen as an effective antioxidant for its applications in therapy, this research reports the fabrication of a coupled microfluidic microbial electrochemical cell (MXC), including microfluidic microbial fuel cells (MFCs) and a microfluidic microbial electrolysis cell (MEC) series in order to perform it as a self-powered biohydrogen generator. Being able to be a platform of implantable medical devices, utilization a non-phatogenic strain of Escherichia coli as the biocatalyst in order to exploit the embodied energy from human blood and excrement and finally the use of cheap and facile materials (<$2 per device) are the exceptional features of the system. The sustainable potential difference for a series of three microfluidic MFCs is 1.97 V, and is high and sufficient for hydrolyzing an organic substrate. The single cell has a capability for producing the maximum power density of 20 W m−3 and the three cells series connection achieve as 38.2 W m−3 as the highest collective power. The maximum hydrogen production rate of 46 and 28 ppm h−1 obtain for glucose and urea-based substrates, respectively. The coupled microfluidic MXC performance characterize based on its substrate type, concentration, flow rate as well as comparison with other conventional MECs.

Improvement of the microfluidic microbial fuel cell using a nickel nanostructured electrode and microchannel modifications

In this study, the effect of utilization of a nanostructured nickel based material as a negative electrode on the performance of microfluidic microbial fuel cell (MFC) with Escherichia coli as biocatalyst has been investigated. Designing the microfluidic MFC with nickel nanostructure resulted in a higher volumetric power density of 343 W m−3 compared to the previously published results. The assessment of effective parameters on the electrochemical performance of cell was investigated. The investigation of the hydraulic diameter impact on the power generation proves that reducing the microchannel hydraulic diameter from 1000 to 350 μm minimized the internal mass-transfer resistance, and consequently 32% increase in the maximum surface power density is observed. Replacing the nickel foil with nickel nanostructures resulted in an additional improvement of 67% in the maximum surface power density. The maximum volumetric power density of 343 W m−3 has been obtained for the fabricated MFC with 350 μm hydraulic diameter associating nanostructured morphology. To assess the capability of the microfluidic MFC as a power source of the energy storage devices, the obtained results show that the microfluidic MFC with nickel nanostructure is able to provide about 76% of the total power needed for manganese rechargeable lithium battery.

Interpretation of the electrochemical response of a multi-population biofilm in a microfluidic microbial fuel cell using a comprehensive model

The present study investigates the diversification and dynamic behavior of a multi-population microfluidic microbial fuel cell (MFC) as a biosensor. The cost effective microfluidic MFC coupled to a comprehensive model, presents a novel platform for monitoring chemical and biological phenomena. The importance of competition among different microbial groups, hierarchical biochemical processes, bacterial chemotaxis and different mechanisms of electron transfer were significant considerations in the present model. The validation of the model using experimental data from a microfluidic MFC shows an appropriate match with the hierarchal biodegradation processes of a complex substrate as well as development of bacterial chemotaxis during multi-population biofilm formation under real conditions. Microfluidic MFC performance, including temporal and spatial distribution of different microbial group concentrations in the biofilm and anolyte bulk, the competitive behavior of different species, bacterial transport parameters and bioelectrochemical characteristics are also assessed.

Paper Based Microfluidic Microbial Fuel Cell to Harvest Energy from Urine

Paper Based Microfluidic Microbial Fuel Cell to Harvest Energy from Urine

Fast Start-Up Microfluidic Microbial Fuel Cells With Serpentine Microchannel.

Microfluidic microbial fuel cells (MMFCs) are promising green power sources for future ultra-small electronic devices. The MMFCs with co-laminar microfluidic structure are superior to other MMFCs according to their low internal resistance and relative high power density. However, the area for interfacial electron transfer between the bacteria and the anode is quite limited in the typical Y-shaped device, which apparently restricts the current generation performance. In this study, we developed a membraneless MMFC with serpentine microchannel to enhance the interfacial electron transfer and promote the power generation of the device. Owing to the merit of laminar flow, the proposed MMFC was working well without any proton exchange membrane (PEM). At the same time, the serpentine microchannel greatly increased the power density. The S-MMFC catalyzed by Shewanella putrefaciens CN32 achieves a peak power density of 360 mW/m2 with the optimal channel configuration and the flow rate of 5 ml/h. Meanwhile, this device possesses much shorter start-up time and much longer duration time at high current plateau than the previous reported MMFCs. The presented MMFC appears promising for biochip technology and extends the scope of microfluidic energy.

A laminar-flow based microbial fuel cell array

We created a novel laminar-flow based microbial fuel cell (MFC) array to be an integrable and scalable power source for portable lab-on-a-chip (LOC) devices. The microfluidic MFC enabled the laminar flow of anolyte and catholyte streams in a microchannel without any physical membranes while the device harvested electricity by utilizing ion transfers through the laminar interface which acts as a virtual membrane. The array prototype incorporated four series-connected fuel cells and was operated with two common inlets for the continuous introduction of the anolyte and catholyte. In the anodic flow region, microorganisms oxidized organic media and completed respiration by transferring the electrons to the anodes. The protons generated by the anodic reactions passed through the liquid-liquid interfaces and traveled to the cathodic streams. The electrons then moved across the external resistors to the cathodes where they combined with the protons and reduced oxidant (i.e. catholyte). The array generated a maximum power output of 60.5μW/cm2 using a 100kΩ load, which outperformed a single laminar flow MFC unit by a factor of approximately 4. The series or parallel application of this array structure, using microfluidic MFCs integrated into a single LOC device, can offer the potential for on-chip power generation.

Enhanced biofilm distribution and cell performance of microfluidic microbial fuel cells with multiple anolyte inlets

A laminar-flow controlled microfluidic microbial fuel cell (MMFC) is considered as a promising approach to be a bio-electrochemical system (BES). But poor bacterial colonization and low power generation are two severe bottlenecks to restrict its development. In this study, we reported a MMFC with multiple anolyte inlets (MMFC-MI) to enhance the biofilm formation and promote the power density of MMFCs. Voltage profiles during the inoculation process demonstrated MMFC-MI had a faster start-up process than the conventional microfluidic microbial fuel cell with one inlet (MMFC-OI). Meanwhile, benefited from the periodical replenishment of boundary layer near the electrode, a more densely-packed bacterial aggregation was observed along the flow direction and also the substantially low internal resistance for MMFC-MI. Most importantly, the output power density of MMFC-MI was the highest value among the reported µl-scale MFCs to our best knowledge. The presented MMFC-MI appears promising for bio-chip technology and extends the scope of microfluidic energy.

Characterization of a microfluidic microbial fuel cell as a power generator based on a nickel electrode

This study reports the fabrication of a microfluidic microbial fuel cell (MFC) using nickel as a novel alternative for conventional electrodes and a non-phatogenic strain of Escherichia coli as the biocatalyst. The feasibility of a microfluidic MFC as an efficient power generator for production of bioelectricity from glucose and urea as organic substrates in human blood and urine for implantable medical devices (IMDs) was investigated. A maximum open circuit potential of 459mV was achieved for the batch-fed microfluidic MFC. During continuous mode operation, a maximum power density of 104Wm−3 was obtained with nutrient broth. For the glucose-fed microfluidic MFC, the maximum power density of 5.2μWcm−2 obtained in this study is significantly greater than the power densities reported previously for microsized MFCs and glucose fuel cells. The maximum power density of 14Wm−3 obtained using urea indicates the successful performance of a microfluidic MFC using human excreta. It features high power density, self-regeneration, waste management and a low production cost (<$1), which suggest it as a promising alternative to conventional power supplies for IMDs. The performance of the microfluidic MFC as a power supply was characterized based on polarization behavior and cell potential in different substrates, operational modes, and concentrations.

Biofilm distribution and performance of microfluidic microbial fuel cells with different microchannel geometries

Laminar-flow controlled microfluidic microbial fuel cells (MMFCs) with three different microchannel geometries, including the converging channel, the straight channel and the diverging channel, are presented and investigated. The biofilm distribution along the microchannel is visualized and compared. The effects of microchannel geometry on the start-up process and cell performance are also evaluated. The results show that the MMFC with the diverging channel (MMFC-D) begins to generate current in the shortest time compared with MFCs with the converging channel (MMFC-C) and the straight channel (MMFC-S). Moreover, the maximum power density (2447.7 ± 38.9 mW m−2) of MMFC-D is 429% and 24% higher than that of MMFC-C (462.7 ± 17.5 mW m−2) and MMFC-S (1980.1 ± 27.5 mW m−2), respectively. The high performance of MMFC-D can be explained by the combined effect of the good and uniform attached biofilm and the low anode resistance, which significantly depends on the microchannel geometry.

Fabrication of Conductive Microparticles as Anodal Electrode in Microfluidic Microbial Fuel Cell

Microbial fuel cell (MFC) is developed as a renewable energy source, which can simultaneously carries out wastewater treatment. The ability of microorganism in generating extractable electricity highly affects the performance of a MFC; therefore, it is critical to construct a high throughput analysis platform for microorganism screening. Microfluidic MFCs are recently developed for the rapid analysis; however, several challenges remained to be overcome to construct straightforward techniques. This study presents an innovative anode composed of conductive microparticles for encapsulating electricity-generating microbes in microfluidic MFCs. The conductive polymer microparticles (Diallyldimethylammonium chloride, DADMAC) encapsulating microorganisms were generated by a T-junction microchannel. The surface area per volume of the pDADMAC micro-particle was 2.17x106 cm-1 and it can provide extensive surface area for electron transfer. We first examined the electricity generated from these particles using a batch-type operation. Microparticles containing microbes generated open circuit voltage (OCV) of 8mV in the first hour and the OCV gradually decreased to 0mV in 6hours, indicating the depletion of substrate. Particles without microbes had relatively stable OCV around 1mV throughout the operation except for the first 10min. The conductive microparticles were also applied in an air-cathode batch-type MFC and they increased the OCV from ∼0V to ∼20mV compared with freely suspended microorganisms. These results show the great potential of utilizing the conductive microparticles as anodal electrode in microfluidic microbial fuel cells.