A microfluidic glucose biofuel cell to generate micropower from enzymes at ambient temperature
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, , 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 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 (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.
References (20)
- et al.
J. Power Sources
(2007) - et al.
J. Power Sources
(2004) - et al.
J. Power Sources
(2005) - et al.
J. Power Sources
(2005) - et al.
Microelectron. Eng.
(2007) - et al.
Electrochim. Acta
(2007) - et al.
Biosens. Bioelectron.
(2007) - et al.
J. Power Sources
(2008) - et al.
J. Power Sources
(2008) - et al.
Appl. Phys. Lett.
(2000)
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