Single-chamber solid oxide fuel cells with coplanar microelectrodes were operated in methane-air mixtures (R-mix = 2) at 700 degrees C. The performance of cells with one pair of NiO-YSZ (yttria stabilized zirconia) anode and (La0.8Sr0.2)(0.98)MnO3-YSZ cathode, arranged parallel on a YSZ electrolyte substrate, was found to be significantly dependent on the electrode width. For an interelectrode gap of similar to 250 mu m, cells with average electrode widths exceeding similar to 850 mu m could establisha stable open circuit voltage (OCV) of similar to 0.8 V, while those with widths less than similar to 550 mu m could not establish any OCV. In the intermediate range, the cells exhibited significant fluctuations in voltage and power under our testing conditions. This behavior suggests that a lower limit to electrode dimensions exists for cells with single electrode pairs, below which neither a stable difference in oxygen partial pressure, nor an OCV, can be established. Conversely, increasing the electrode width imposes a penalty in the form of an increase in the cell resistance. However, both size limits can be circumvented by employing multiple pairs of microscale electrodes in an interdigitated configuration. (C) 2009 Elsevier B.V. All rights reserved.