Thin-film solid oxide fuel cells (SOFCs) with large (5-mm square) membranes and ultra-thin La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF) cathodes have been fabricated and their electrochemical performance was measured up to 500 degrees C. A grid of plated nickel on the cathode with 5-10 mu m linewidth and 25-50 mu m pitch successfully supported a roughly 200-nm-thick LSCF/yttria-stabilized zirconia/platinum membrane while covering less than 20% of the membrane area. This geometry yielded a maximum performance of 1 mW cm(-2) and 200 mV open-circuit voltage at 500 degrees C. Another approach toward realizing large area fuel cell junctions consists of depositing the membrane on a smooth substrate, covering it with a high-porosity material formed in situ, then removing the Substrate. We have used a composite of silica aerogel and carbon fiber as the support, and show that this material can be created in flow channels etched into the underside of a silicon chip bonded to the top of the SOFC membrane. We anticipate these integrated fuel cell devices and structures to be of relevance to advancing low-temperature SOFCs for portable applications. (C) 2009 Elsevier B.V. All rights reserved.