An exemplary fuel cell device assembly includes: (i) an electrolyte sheet; (ii) a plurality of cathodes disposed on one side of the electrolyte sheet; (iii) a plurality of anodes disposed on another side of the electrolyte sheet; and (iv) a frame supporting the electrolyte sheet, the frame having a plurality of channels. Preferably the cross-sectional area of the frame has channel density of at least 20/in2 and channel wall thickness of 50 mils or less.