Biological fuel cell miniature

Extensive review literature exists in the area of biological fuel cells. Notably, Palmore and Whitesides summarized biological fuel cell concepts and performance up to 1992." More recently, Katz and Willner discussed recent progress in novel electrode chemistries for both microbial and enzymatic fuel cells,and Heller reviewed advances in miniature cells.This article does not duplicate these valuable contributions. Instead, we focus on the strengths and weak-... 

Heller A, Mano N, Kim H-H, Zhang Y, Mao F, Chen T, Calabrese Barton S. Miniature biological fuel cell that is operational uruler physiological conditions, and associated devices and methods. WIPO Pub No. WO/2003/106966, 2003 (to TheraSense, Inc.). 

Electrochemistry is the basis of many important and modem applications and scientific developments such as nanoscale machining (fabrication of miniature devices with three dimensional control in the nanometer scale), electrochemistry at the atomic scale, scanning tunneling microscopy, transformation of energy in biological cells, selective electrodes for the determination of ions, and new kinds of electrochemical cells, batteries and fuel cells. 

Many potential applications are under study. Miniature chemical reactors could be used for portable applications in which they provide advantages of rapid startup and shutdown and of increased safety (intensification by requiring only small quantities of hazardous materials). The development of chip-scale chemical and biological analysis systems has the potential to reduce the time and cost associated with conventional laboratory methods. These devices could be used as portable analysis systems for detection of hazardous chemicals in air and water. There is considerable interest in using a microreactor to provide in situ production of hydrogen for small-scale fuel-cell power applications by conducting a reformation reaction from some liquid hydrocarbon raw material (e.g., methanol). 

An EFC consists of two electrodes, anode and cathode, connected by an external load (shown schematically in Figure 5.1). In place of traditional nonselective metal catalysts, such as platinum, biological catalysts (enzymes) are used for fuel oxidation at the anode and oxidant reduction at the cathode. J udicious choice of enzymes allows such reactions to occur under relatively mild conditions (neutral pH, ambient temperature) compared to conventional fuel cells. In addition, the specificity of the enzyme reactions at the anode and cathode can eliminate the need for other components required for conventional fuel cells, such as a case and membrane. Due to the exclusion of such components, enzymatic fuel cells have the capacity to be miniaturized, and consequently micrometer-dimension membraneless EFCs have been developed [7]. In the simplest form, the difference between the formal redox potential (F ) of the active site of the enzymes utilized for the anode and cathode determines the maximum voltage (A ) of the EFC. Ideally enzymes should possess the following qualities. 

Miniaturized fuel cells are an attractive candidate for next-generation portable power sources. A microfluidic fuel cell is defined as a fuel cell with smaU-scale channels, typically submiUimeter in height, in which reactant delivery/removal and electrochemical energy conversion take place. This type of fuel cell can be incorporated with both metalhc and biological catalysts and normally operates without a physical barrier between anode and cathode compartments. Micromachined fuel cells employing ion-conducting membranes are not covered in this entry. 

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