Serially-linked serpentine flow channels for PEM fuel cell

In a PEM fuel cell comprising (1) a proton exchange membrane having opposing cathode and anode faces on opposite sides of said membrane, (2) a gas-permeable, electrically conductive cathode current collector engaging said cathode face, (3) a gas-permeable, electrically-conductive anode current collector engaging said anode face, and (4) a current-collecting plate engaging at least one of said gas-permeable cathode and anode current collectors and defining a gas flow field confronting said one gas-permeable collector, said flow field comprising a plurality of lands engaging said one current collector and defining a plurality of substantially equal-length serpentine gas flow channels, the improvement wherein each of said channels comprises (a) a plurality of serially-linked serpentine segments that lie in a first general direction extending between a gas supply manifold and a gas exhaust manifold, said segments each having an inlet leg for receiving gas into the segment at a first pressure, an exit leg for exhausting said gas from said segment at a second pressure less than said first pressure, at least one medial leg intermediate said inlet and exit legs, said inlet, exit and medial legs for each channel at least in part bordering at least one other leg of the same channel, and a reverse turn at each end of said medial leg connecting said medial leg to adjacent legs of the same channel, and (b) a bridging section coupling the exit leg of one segment to the inlet leg of the next adjacent segment downstream of said one segment in the same channel.