A microfluidic glucose biofuel cell to generate micropower from enzymes at ambient temperature

doi:10.1016/j.elecom.2008.12.036

Electrochemistry Communications

Volume 11, Issue 3, March 2009, Pages 592-595

https://doi.org/10.1016/j.elecom.2008.12.036 Get rights and content

Abstract

A Y-shaped microfluidic channel is applied for the first time to the construction of a glucose/O₂ biofuel cell, based on both laminar flow and biological enzyme strategies. During operation, the fuel and oxidant streams flow parallel at gold electrode surfaces without convective mixing. At the anode, the glucose oxidation is performed by the enzyme glucose oxidase whereas at the cathode, the oxygen is reduced by the enzyme laccase, in the presence of specific redox mediators. Such cell design protects the anode from an interfering parasite reaction of O₂ at the anode and offers the advantage of using different streams of oxidant and fuel for optimal performance of the enzymes. Electrochemical characterizations of the device show the influence of the flow rate on the output potential and current density. The maximum power density delivered by the assembled biofuel cell reached 110 μW cm⁻² at 0.3 V with 10 mM glucose at 23 °C. The microfluidic approach reported here demonstrates the feasibility of advanced microfabrication techniques to build an efficient microfluidic glucose/O₂ biofuel cell device.

Introduction

Microfluidic fuel cells can provide an alternative pathway towards miniaturized power supplies. These devices confine all the fundamental components of a fuel cell within a single microstructured network exploiting laminar flow of fluids at a low Reynolds number that to limit convective mixing [1], [2], [3]. In such systems, streams of fuel and oxidant flow in parallel within the microchannel eliminating the need for a membrane. The electrochemical reactions take place at the anode and cathode located within the respective streams. Various microfluidic fuel cells working with hydrogen, methanol or formic acid as fuel have recently attracted significant attention [4], [5], [6], [7]. The microfluidic approach offers several advantages over macro-scale systems including the use of less reagents and space and less time consumption. Interesting theoretical and experimental works have been published previously describing the effect of flow rate, microchannel geometry, and location of electrodes within microfluidic systems on their performance [8], [9], [10].

Enzymatic BioFuel Cells (BFC) convert chemical energy into electrical energy via specific enzymes acting as catalysts, and are strong candidates for the supply of power to miniature portable electronic [11] or biomedical devices [12]. Microfluidic enzyme biofuel cells have been developed based on both laminar flow within a microchannel and biological enzyme strategies. Palmore et al. [13] developed a microfluidic fuel cell working from a laccase cathode in the presence of the 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS). A transport model was developed to describe the optimal conditions for maximizing both the average current density and the percentage of fuel utilized. The maximum power value reached 26 μW cm⁻² at 0.4 V at a flow rate of 100 μL min⁻¹. Another device has been developed that generated electrical power from glucose oxidation with a glucose dehydrogenase anode and a bilirubin oxidase-adsorbed O₂ cathode [14]. The originality of this work lay in the electrode-arrangement in a single flow channel. Dissolved O₂ was pre-reduced at an upstream cathode to protect the downstream anode from the oxidative environment. The maximum cell current was 160 μA cm⁻² at a flow rate of 300 μL min⁻¹.

The objective of this work is to apply advanced microfabrication techniques to build a functional microfluidic glucose/O₂ biofuel cell. At the anode, the glucose is oxidized by the enzyme glucose oxidase (GOD), whereas at the cathode the oxygen is reduced by the enzyme laccase, in the presence of redox mediators. The device is based on a Y-shaped microfluidic channel exploiting the laminar flow of the streams both to protect the anode from interfering parasite reactions of O₂ and to use different media for optimal operation of the enzymes. The dimensions and the operating conditions of this microfluidic device are such that fluid flow is pressure driven and characterized by a Reynolds’ number varying from 3.3 to 33.3 [1] in the flow rate range 100–1000 μL min⁻¹. The significant performance of the power output is demonstrated by electrochemical characterizations of the device as a function of the flow rate through the microchannel.

Section snippets

Chemicals

ABTS, $K_{3} Fe (CN)_{6}$ , GOD from Aspergillus Niger (198,000 U mg⁻¹ solid) and laccase from Trametes Versicolor (20 U mg⁻¹ solid) were purchased from Sigma–Aldrich and used without further purification. Buffers were prepared with sodium dihydrogen phosphate monohydrate (NaH₂PO₄ · H₂O) and di-sodium hydrogen phosphate (Na₂HPO₄) salts (pH 7.0) from Merck, and with citric acid (Prolabo) and NaH₂PO₄· H₂O salt (pH 3.0). β-d-glucose (Prolabo) was prepared in phosphate buffer 0.1 M pH 7.0 at least 24 h before its use.

Physicochemical analysis

In the BFC, the redox reactions are the electro-oxidation of glucose in gluconolactone by the glucose oxidase with $Fe (CN)_{6}^{3 -}$ at the anode, and the electro-reduction of dioxygen in water by the laccase with ABTS at the cathode. The cell voltage is partially controlled by the formal potential of the mediators $Fe (CN)_{6}^{3 -}$ (E′° = 0.12 V vs. SCE) and ABTS^.− (E′° = 0.46 V vs. SCE) chosen with a formal potential close to that of GOD (E′° = − 0.34 V vs. SCE [17]) and laccase (E′° = 0.535 V vs. SCE [18]), respectively.

Conclusion

This work has demonstrated the feasibility of advanced microfabrication techniques to build an efficient microfluidic glucose/O₂ biofuel cell device as compared to standard miniaturization techniques of glucose biofuel cell. This device operated with laminar flow of different streams of oxidant and fuel for optimal performance of the enzymes. The biofuel cell delivered current densities of 690 μA cm⁻² and a power density of 110 μW cm⁻² at 0.3 V with 10 mM glucose at ambient temperature.

Better fuel

Acknowledgment

This work was supported by a CNRS postdoctoral fellowship.

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A microfluidic glucose biofuel cell to generate micropower from enzymes at ambient temperature

Abstract

Introduction

Section snippets

Chemicals

Physicochemical analysis

Conclusion

Acknowledgment

J. Power Sources

J. Power Sources

J. Power Sources

J. Power Sources

Microelectron. Eng.

Electrochim. Acta

Biosens. Bioelectron.

J. Power Sources

J. Power Sources

Appl. Phys. Lett.