Materials for Microfluidic Fuel Cells

No smart solution is available to store the gaseous hydrogen used in miniature fuel cell (PEMFC) and hence DMFC is receiving enormous interest due to system simplicity. However, specialised air-breathing DMFC components have to be developed. New materials have to be developed in addition to optimisation of structure and operating conditions to take care of performance decay modes. New membrane/electrode assemblies appropriate for the microscale to be developed exploiting the enhanced heat and mass transfer on the microscale for improved performance, and developing microfluidic components for micro fuel cells. 

Polymethylmethacrylate (PMMA) is another polymeric material frequently employed for microfluidics and micro fuel cells [4]. PMMA is one of the thermoplastic polymers that is usually linearly linked and can be softened by applying heat at above the glass transition temperature [8]. PMMA has a noncrystalUne structure with 92% light transmittance in the visible spectrum. This material also has other excellent properties such as low frictional coefficient, high chemical resistance, and good electrical insulation. All these features and properties make PMMA a good substrate for microfluidic devices, especially for those involved in chemical applications [8]. 

Chan et al. (2005), have realised micro fuel cells through an approach that combines thin film materials with MEMS (micro-electro-mechanical system) technology. The membrane electrode assembly was embedded in a polymeric substrate (PMMA) which was micromachined through laser ablation to form gas flow channels. The micro gas channels were sputtered with gold to serve as current collectors. This cell utilized the water generated by the reaction for the humidification of dry reactants (H2 and O2). The peak power density achieved was 315 mW cm (901 mA cm" at 0.35 V) for the H2-O2 system with 20 ml min" O2 supply and H2 at 10 psi in dead ended mode of operation. A Y shaped microfluidic channel is depicted in Fig. 21. 

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