[object Object], [object Object], [object Object]

Biomicrofluidics • 2017

Specially designed microfluidic bioflow cells were used to temporarily trap microbubbles during different inoculation stages of Pseudomonas sp. biofilms. Despite being eliminated many hours before biofilm appearance, templated growth could occur at former bubble positions. Bubble-templated growth was either continuous or in ring patterns, depending on the stage of inoculation when the bubbles were introduced. Templated biofilms were strongly enhanced in terms of their growth kinetics and structural homogeneity. High resolution confocal imaging showed two separate bubble-induced bacterial trapping modes, which were responsible for the altered biofilm development. It is concluded that static bubbles can be exploited for fundamental improvements to bioreactor performance, as well as open new avenues to study isolated bacteria and small colonies.

[object Object], [object Object], [object Object] et al.

Analytical Chemistry • 2018

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Bioelectrochemistry • 2011

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Lab Chip • 2006

We review transport characteristics of pressure-driven, multiphase flows through microchannel networks tens of nanometres to several hundred of micrometres wide with emphasis on conditions resulting in enhanced mixing and reduced axial dispersion. Dimensionless scaling parameters useful in characterizing multiphase flows are summarized along with experimental flow visualization techniques. Static and dynamic stability considerations are also included along with methods for stabilizing multiphase flows through surface modifications. Observed gas-liquid and immiscible liquid-liquid flows are summarized in terms of flow regime diagrams and the different flows are related to applications in chemistry and materials synthesis. Means to completely separate multiphase flows on the microscale and guidelines for design of scalable multiphase systems are also discussed.

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Chemical Engineering Journal • 2021

[object Object], [object Object], [object Object] et al.

Biosensors and Bioelectronics • 2009

[object Object], [object Object], [object Object] et al.

Environmental Microbiology • 2008

Summary It has been previously noted that mixed communities typically produce more power in microbial fuel cells than pure cultures. If true, this has important implications for the design of microbial fuel cells and for studying the process of electron transfer on anode biofilms. To further evaluate this, Geobacter sulfurreducens was grown with acetate as fuel in a continuous flow ‘ministack’ system in which the carbon cloth anode and cathode were positioned in close proximity, and the cation‐selective membrane surface area was maximized in order to overcome some of the electrochemical limitations that were inherent in fuel cells previously employed for the study of pure cultures. Reducing the size of the anode in order to eliminate cathode limitation resulted in maximum current and power densities per m 2 of anode surface of 4.56 A m −2 and 1.88 W m −2 respectively. Electron recovery as current from acetate oxidation was c . 100% when oxygen diffusion into the system was minimized. This performance is comparable to the highest levels previously reported for mixed communities in similar microbial fuel cells and slightly higher than the power output of an anaerobic sludge inoculum in the same ministack system. Minimizing the volume of the anode chamber yielded a volumetric power density of 2.15 kW m −3 , which is the highest power density per volume yet reported for a microbial fuel cell. Geobacter sulfurreducens formed relatively uniform biofilms 3–18 μm thick on the carbon cloth anodes. When graphite sticks served as the anode, the current density (3.10 A m −2 ) was somewhat less than with the carbon cloth anodes, but the biofilms were thicker ( c . 50 μm) with a more complex pillar and channel structure. These results suggest that the previously observed disparity in power production in pure and mixed culture microbial fuel cell systems can be attributed more to differences in the fuel cell designs than to any inherent superior capability of mixed cultures to produce more power than pure cultures.

[object Object], [object Object], [object Object] et al.

Journal of Power Sources • 2016

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Journal of Power Sources • 2011

[object Object], [object Object], [object Object] et al.

Journal of Power Sources • 2021

[object Object], [object Object], [object Object] et al.

Frontiers in Energy Research • 2019

[object Object], [object Object], [object Object] et al.

Biotechnology and Bioengineering • 2011

Abstract Next generation battery technology is rapidly evolving to meet the demand for higher power densities and smaller footprints through novel catalysts and battery architecture. We present a µ‐scale, biological fuel cell which utilizes microbial electricity generation enabled by microfluidic flow control to produce power. The new fuel cell, the smallest of its kind, with a total volume of 0.3 µL, produces scalable and controllable electrical energy from organic matter which is sustained through microbial respiration and laminar flow separation of the electrolytes. Electrical currents are dependent on specific biofilm formation on the anode, the concentration of electron donor, and a diffusion‐limited flow regime. A maximum current density of 18.40 ± 3.48 mA m −2 (92 ± 17 A m −3 ) was produced by Geobacter sulfurreducens , and 25.42 mA m −2 (127 A m −3 ) by Shewanella oneidensis . The µ‐scale biological fuel cell introduces the necessary small size and fuel flexibility for applications in vivo and in situ sensors which may be remotely deployed and self‐powered. Biotechnol. Bioeng. 2011;108:2061–2069. © 2011 Wiley Periodicals, Inc.

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Sustainable Energy & Fuels • 2019

Geobacter biofilms can be switched into different metabolic activity states and operate efficiently at low concentrations microfluidic three-electrode reactor.

[object Object], [object Object], [object Object] et al.

Langmuir • 2017

[object Object], [object Object], [object Object] et al.

International Journal of Hydrogen Energy • 2013

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Energy & Environmental Science • 2012

[object Object], [object Object], [object Object] et al.

Microbial Cell Factories • 2019

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Applied and Environmental Microbiology • 2003

ABSTRACT Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 μM), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 μmol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (E o ′ =+0.37 V). The production of current in microbial fuel cell (65 mA/m 2 of electrode surface) or poised-potential (163 to 1,143 mA/m 2 ) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.

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Micro & Nano Letters • 2017

This work numerically investigated the effects of various factors on the performance of air‐breathing direct formic acid microfluidic fuel cells. An MFC with a microchannel width of 1.5 mm, depth of 0.05 mm, and electrode spacing of 0.3 mm was used in the simulation. An MFC which was a 1.5‐mm‐wide, 0.05‐mm‐deep microchannel installed with two 0.3‐mm‐apart electrodes was used in the simulation. The mixture of formic acid at concentrations of 0.3, 0.5, and 1.0 M and 0.5‐M sulphuric acid served as fuel, while a 0.5‐M sulphuric acid stream served as the electrolyte introduced at inlet flow rates of 0.05, 0.1, and 0.5 mL/min. First, a three‐dimensional MFC model was built using COMSOL Multiphysics 5.1 to simulate the fuel cell performance. Subsequently, I–V curves obtained from simulations and from published experimental data under similar operating conditions were compared to ensure the validity of the simulation. Transport phenomena were formulated with a continuity equation, momentum equation, species transport equation, and charge equation. Additionally, the flow through porous media in the gas diffusion layer was described using the Brinkman equation, whereas the Butler–Volmer equation was applied to obtain I–V and P–I curves. The current density distribution resulting from internal current loss and reactant concentration on both electrodes was also determined in this work.

[object Object], [object Object], [object Object] et al.

ChemPlusChem • 2020

Abstract A laminar flow reactor was designed that provides constant and reproducible growth conditions for the bioelectrochemical observation of electroactive bacteria (EAB). Experiments were performed using four reactors in parallel to enable the comparison of EAB growth behavior and bioelectrochemical performance under different hydrodynamic conditions while simultaneously keeping biological conditions identical. With regard to the moderate flow conditions found in wastewater treatment applications, the wall shear stress was adjusted to a range between 0.4 mPa to 2.9 mPa. Chronoamperometric data indicate that early stage current densities are improved by a moderate increase of the wall shear stress. In the same way, current onset times were increasing slightly towards higher values of the applied wall shear stress. Long‐term observations of EAB performance showed a decrease in current density and a leveling of the trend observed for the early stages of biofilm growth.

[object Object], [object Object], [object Object] et al.

Electrochimica Acta • 2022

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Journal of The Electrochemical Society • 2015

[object Object], [object Object], [object Object] et al.

Journal of Power Sources • 2022

[object Object], [object Object], [object Object] et al.

Physical Chemistry Chemical Physics • 2019

The electrochemical study of fast catalytic reactions is limited by mass transport using the conventional electrochemical cell with a rotating disk electrode (RDE).

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Journal of Power Sources • 2018

[object Object], [object Object], [object Object] et al.

ChemSusChem • 2012

Abstract We report a laminar flow‐based microfluidic bioelectrochemical system (BES) that was fabricated by using polydimethyl siloxane (PDMS) channels and gold electrodes. The microfluidic BES was operated as a potentiostatically controlled two‐electrode system. A pure culture of Geobacter sulfurreducens strain PCA, which is a model electrode‐respiring bacterium, was grown in the channel and respired with the electrode under strict anaerobic conditions. We took advantage of the short hydraulic retention time (≈2 min) and response times (<21 min) to rapidly test the effect of certain chemical stimuli, such as O 2 and anthraquinone disulfide (AQDS), on electric current production by G. sulfurreducens . The results showed that: i) short‐term (2 min) exposure to O 2 ‐saturated solution did not cause any irreversible toxicity to G. sulfurreducens , and ii) AQDS can be used as a redox mediator by G. sulfurreducens for shuttling electrons between the microbe and the electrode. We, therefore, demonstrate that the microfluidic BES is a promising research tool for gaining insight into microbial electrochemical activity. In our two‐dimensional microfluidic‐based research tool, a well‐defined electrochemical environment can be maintained with the help of laminar flow without a membrane to separate two electrodes.

[object Object], [object Object], [object Object] et al.

Lab on a Chip • 2011

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Frontiers in Microbiology • 2018

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/m 2 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.

[object Object], [object Object], [object Object] et al.

International Journal of Hydrogen Energy • 2015

[object Object], [object Object], [object Object] et al.

Biosensors and Bioelectronics • 2016

[object Object], [object Object], [object Object] et al.

Physical Chemistry Chemical Physics • 2014

The integration of Microbial Fuel Cells (MFCs) in a microfluidic geometry can significantly enhance the power density of these cells, which would have more active bacteria per unit volume. Moreover, microfluidic MFCs can be operated in a continuous mode as opposed to the traditional batch-fed mode. Here we investigate the effect of fluid flow on the performance of microfluidic MFCs. The growth and the structure of the bacterial biofilm depend to a large extent on the shear stress of the flow. We report the existence of a range of flow rates for which MFCs can achieve maximum voltage output. When operated under these optimal conditions, the power density of our microfluidic MFC is about 15 times that of a similar-size batch MFC. Furthermore, this optimum suggests a correlation between the behaviour of bacteria and fluid flow.

[object Object], [object Object], [object Object] et al.

Electrochimica Acta • 2022

Carlo Santoro, Alexey Serov, Lydia Stariha et al.

Energy & Environmental Science • 2020

Development of low-cost iron-based catalysts for MFC cathodes.

Bradley R. Ringeisen, Emily Henderson, Peter K. Wu et al.

Environmental Science & Technology • 2006

Miniature MFC achieves high power density with Shewanella oneidensis.

Shaoan Cheng, Hong Liu, Bruce E. Logan

Environmental Science & Technology • 2006

Improved cathode design increases power density in single-chamber MFCs.

Doo Hyun Park, J. Gregory Zeikus

Applied and Environmental Microbiology • 2000

ABSTRACT Neutral red (NR) was utilized as an electron mediator in microbial fuel cells consuming glucose to study both its efficiency during electricity generation and its role in altering anaerobic growth and metabolism of Escherichia coli and Actinobacillus succinogenes . A study of chemical fuel cells in which NADH, NR, and ferricyanide were the electron donor, the electronophore, and the electron acceptor, respectively, showed that electrical current produced from NADH was proportional to the concentration of NADH. Fourfold more current was produced from NADH in chemical fuel cells when NR was the electron mediator than when thionin was the electron mediator. In microbial fuel cells in which E. coli resting cells were used the amount of current produced from glucose when NR was the electron mediator (3.5 mA) was 10-fold more than the amount produced when thionin was the electron mediator (0.4 mA). The amount of electrical energy generated (expressed in joules per mole of substrate) and the amount of current produced from glucose (expressed in milliamperes) in NR-mediated microbial fuel cells containing either E. coli or A. succinogenes were about 10- and 2-fold greater, respectively, when resting cells were used than when growing cells were used. Cell growth was inhibited substantially when these microbial fuel cells were making current, and more oxidized end products were formed under these conditions. When sewage sludge (i.e., a mixed culture of anaerobic bacteria) was used in the fuel cell, stable (for 120 h) and equivalent levels of current were obtained with glucose, as observed in the pure-culture experiments. These results suggest that NR is better than other electron mediators used in microbial fuel cells and that sludge production can be decreased while electricity is produced in fuel cells. Our results are discussed in relation to factors that may improve the relatively low electrical efficiencies (1.2 kJ/mol) obtained with microbial fuel cells.

Min-soo Hyun, Sang-Kyung Kim, Doohwan Jung et al.

Journal of Power Sources • 2006

Hyung Joo Kim, Hyung Soo Park, Moon Sik Hyun et al.

Enzyme and Microbial Technology • 2002

Shaoan Cheng, Bruce E. Logan

Electrochemistry Communications • 2007

César I. Torres, Andrew Kato Marcus, Hyung-Sool Lee et al.

FEMS Microbiology Reviews • 2010