This paper reports design, materials, and testing of microfabricated fuel cells that can be applied for small power generation. Multiple co-planar fuel cells in series have been built onto ceramic substrates (as well as silicon and polymer, but not reported here) using thick-film fabrication techniques. Testing of these fuel cells gave power densities in the milliwatt (per square centimeter) range for continuous power and tens of miliwatts tinder pulsing conditions, and have indicated performance limiters and opportunities for higher power densities. These fuel cells are intended to operate on ambient-supplied air, and thus the polymer electrolytes must be capable of operating Under a range of humidity conditions. The target conductivity for these low power devices is > 1 mS cm(-1) at 15% RH. Although novel polymer electrolytes are being pursued at CWRU for this application, we report here Nafion(R) films cast from alternate solvents that have adequate conductivity for this application. Several on-board fuel storage approaches are being pursued. We have demonstrated high fuel utilization by a fuel cell operating with on-board Source of hydrogen front aqueous sodium borohydride, as well from solid metal hydride systems. (C) 2003 Elsevier Ltd. All rights reserved.