Microfabricated fuel cell systems are a promising alternative to batteries for manportable power generation. These devices are potential consumer products that constitute a more or less complex chemical process, and can therefore be considered chemical products. A great variety of potential devices are being considered in various research institutions and thus there is a need for a systematic product design methodology, including comparison of alternatives and examination of the influence of technological parameters. The design of these product/process hybrids is inherently different from macroscale process design because of the differing design specifications, objectives, and constraints, as well as the relative importance of the underlying physico-chemical phenomena. Heat losses substantially influence the process performance, so the processes are highly spatially integrated. Consequently, flowsheet design and layout need to be considered simultaneously. In this paper we present our methodology and perform a number of case studies, including studies of scaling of the processes and effects of layout options and relevant technological parameters. (c) 2005 American Institute of Chemical Engineers