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SUMMARYThis paper presents a review and discussion of micro-fuel cell technologies, providing insight into the innovations that have been made to date. Discussion of concepts and results leading towards increased levels of integration and performance for micro-fuel cell systems will elucidate the potential of thin film and microfabrication methods in meeting the challenges and requirements necessary for consumer applications. While the amount of literature in this area is substantial, a representative sampling of key developments will be presented in this paper, in order to gain a sense of the design methodologies being implemented for micro-fuel cell power sources.

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Fuel cells have gained renewed interest for applications in portable power since the energy is stored in a separate reservoir of fuel rather than as an integral part of the power source, as is the case with batteries. While miniaturized fuel cells have been demonstrated for the low power regime (1-20 Watts), numerous issues still must be resolved prior to deployment for applications as a replacement for batteries. As traditional fuel cell designs are scaled down in both power output and physical footprint, several issues impact the operation, efficiency, and overall performance of the fuel cell system. These issues include fuel storage, fuel delivery, system startup, peak power requirements, cell stacking, and thermal management. The combination of thin-film deposition and micro-machining materials offers potential advantages with respect to stack size and weight, flow field and manifold structures, fuel storage, and thermal management. The micro-fabrication technologies that enable material and fuel flexibility through a modular fuel cell platform will be described along with experimental results from both solid oxide and proton exchange membrane, thin-film fuel cells.

Thin-film, proton exchange membrane fuel cells are developed using photolithographic patterning, physical vapor deposition, and spin-cast deposition techniques. In this study, micrometer-thick layers of nickel (Ni) and platinum (Pt) electrodes, as well as the proton conducting electrolyte layer of perfluoronated sulfonic acid, are synthesized. The anode layer is conductive to pass the electric current and provides mechanical support to the electrolyte and cathode layer that enables combination of the reactive gases. The morphology desired for both the anode and cathode layers facilitates generation of maximum current density from the fuel cell. For these purposes, the parameters of the deposition process and post-deposition patterning are optimized for continuous porosity across both electrode layers. The power output generated through current–voltage measurement is characterized at various temperatures in the range of 60–90 °C using dilute (4%) hydrogen fuel.