Microfluidic devices have shown considerable promise in a wide range of applications from medical screening to portable energy sources. Leveraging the successes of microfluidic technology, Micro fuel cells (μFCs) have been attracting much attention as a leading candidate for prospective portable power sources and battery replacements. Their ability to create an efficient and clean source of energy combined with the ease of portability makes μFCs available to meet the needs of various portable electronic applications in the future. To this purpose, making more efficient devices with cost effective processes and materials is crucial.
Many efforts on fuel cell miniaturization are focused on silicon-based techniques as silicon is the most common substrate in MEMS technology. However, combining silicon devices with polymeric fuel cells at mm or sub-mm scale presents many challenges, none of which have been solved in a completely satisfactory manner. Furthermore, in recent years due to material property issues associated with PDMS such as bulk absorption of small molecules and evaporation through the device, there has been a tendency towards the employment of thermoplastics for microfluidic systems. The importance of micro-structures of polymers for micro fuel cell fabrication is enormous, particularly when considered as a low-cost alternative to the silicon- or glass-based MEMS technologies, for disposable small electronic gadgets.
In this study, an air-breathing micro fuel cell with direct hydrogen flow through porous anode electrode is realized and reported. The performance of the microdevice with embedded flow channels and electrodes is characterized in ambient conditions. To achieve this goal, we implement a SU-8 microchannel stamp to transfer a pattern into a Nafion 1110 membrane by hot embossing. Nafion 212 thermally seals the whole device as a blanket top layer. The fabrication process of microchannels and micro fuel cell construction is evaluated with optical and scanning electron microscopy (SEM) step by step. Variations of hydrogen feed rate on performance were investigated. The shared-anode characteristic design of the double-sided cell is further studied by separate polarization and electrochemical impedance spectroscopy (EIS) measurements taken from each side and compared with data for the complete cell. The maximum power density per superficial (footprint) area is 68.4 mWcm-2 for the shared anode stack. In the present micro fuel cell architecture, the external package is constructed of Nafion polymer, which offers a thin, light and flexible energy source with low cost of manufacturing. The device performance offers a high volumetric and gravimetric energy density for portable applications.