TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The continuous conductive fibers comprise material selected from carbon, graphite, metals, metal alloys, and/or composites (preferably carbon fibers). The carbon fibers has a cross-sectional diameter of 0.1 - 100 mu or a tensile modulus of 10 - 140 msi; tensile strength of 200 - 900 ksi; an electrical resistivity of 2 - 30 muOmegam; thermal conductivity of 5 - 700 W/m.K. The electrocatalyst material comprises material selected from platinum, gold, ruthenium, iridium, palladium, rhodium, nickel, iron, molybdenum, tungsten, niobium, and/or their alloys. The platinum or its platinum alloy selected from platinum-ruthenium alloy, platinum-ruthenium-iron alloy, platinum-molybdenum alloy, platinum-chromium alloy, platinum-tin alloy, and platinum-nickel alloy. The removable carrier material comprises Y2O3.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The first and second fluid passages are separated from and sealed against each other in a leak-tight manner.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The continuous conductive fibers comprise material selected from carbon, graphite, metals, metal alloys, and/or composites (preferably carbon fibers). The carbon fibers has a cross-sectional diameter of 0.1 - 100 mu or a tensile modulus of 10 - 140 msi; tensile strength of 200 - 900 ksi; an electrical resistivity of 2 - 30 muOmegam; thermal conductivity of 5 - 700 W/m.K. The electrocatalyst material comprises material selected from platinum, gold, ruthenium, iridium, palladium, rhodium, nickel, iron, molybdenum, tungsten, niobium, and/or their alloys. The platinum or its platinum alloy selected from platinum-ruthenium alloy, platinum-ruthenium-iron alloy, platinum-molybdenum alloy, platinum-chromium alloy, platinum-tin alloy, and platinum-nickel alloy. The removable carrier material comprises Y2O3.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The continuous conductive fibers comprise material selected from conductive polymers. The carbon fibers are formed by carbonization of polyacrylonitrile (PAN) fibers, pitch fibers, rayon fibers, cellulose fibers, phenolic fibers, epoxy fibers, phthalonitrile fibers, and fibers formed of aromatic acetylene-derived polymers. The membrane separator comprises a solid electrolyte medium; an ion-exchange ceramic material or an ion-exchange polymeric material. The ion-exchange polymer is selected from perflurocarbon-sulfonic-acid-based polymers, polysulfone-based polymers, perfluorocarboxylic-acid-based polymers, styrene-vinyl-benzene-sulfonic-acid-based polymers, and styrene-butadiene-based polymers (preferably perflurocarbon-sulfonic-acid-based polymer). The hydrophobicity-imparting material is selected from polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), hydrophobic fluoropolymers, and hydrophobic fused silica (preferably PTFE). The fibrous substrate comprises a microfibrous inner current collector; microfibrous membrane separator. In (M1) and (M2), the fiber network is formed by binding multiple continuous conductive fibers with a binding composition containing a binding material, optionally, an electrically conductive material, and optionally, a removable carrier material. The binding material comprises an ion-exchange polymer; or perflurocarbon-sulfonic-acid-based polymer. The adhesion layer comprises an ion-exchange polymer containing perflurocarbon-sulfonic-acid-based polymer. The microfibrous inner current collector provided in step a1) contains a coating of a removable substrate material, which is subsequently removed in step a8) to provide the fluid passage between the inner current collector and the inner electrocatalyst layer. The removable substrate material comprises water-soluble polymeric material selected from polyvinyl pyrrolidones (PVP), polyvinyl alcohols (PVA), and polyethylene glycols (PEG). The membrane-forming material used in step a4) comprises a swellable polymeric membrane-forming material, which forms a swellable membrane separator (where the swellable membrane separator is subsequently contacted with a swelling agent in step a7) to provide the fluid passage between the inner current collector and the inner electrocatalyst layer). The swellable polymeric membrane-forming material comprises a perfluorocarbon-sulfonic-acid-based polymer. The first adhesion material in step a2) comprises material selected from polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), and glycerol. The second adhesion material in step a6) comprises a perflurocarbon-sulfonic-acid-based polymer. The microfibrous fuel cell is formed in a continuous manner. Preferred Composition: The binding composition comprises a mixture of a perflurocarbon-sulfonic-acid-based polymer with carbon particles; polytetrafluoroethylene (PTFE) and further comprises at least one of polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), or glycerol; at least one hydrophobicity-imparting material. The adhesion composition comprises an adhesion material selected polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), and glycerol. Preferred Structures: In (M1), the catalytic precursor structures are formed by forming a fiber network containing multiple continuous conductive fibers extending in parallel directions; and impregnating such fiber network with an electrocatalyst material. The catalytic precursor structures and catalyst structure are involved by a ribbon conformation. The ribbon-shaped catalytic precursor structures and catalyst structure has a thickness of 5 - 100 mu. The ribbon-shaped catalytic precursor structures and catalyst structure comprises multiple layers of continuous conductive fibers. The ribbon-shaped catalytic precursor structures are incorporated into the microfibrous fuel cell element by attaching the ribbon-shaped catalytic precursor structures to a fibrous substrate that comprises either a microfibrous inner current collector or a microfibrous membrane separator. An adhesion composition is applied to a surface of the fibrous substrate for enhancing adhesion between the ribbon-shaped catalytic precursor structures and the fibrous substrate. The ribbon-shaped catalytic precursor structures are attached to the fibrous substrate by concurrently passing the ribbon-shaped catalytic precursor structures and the fibrous substrate through an applicator die. The applicator die is sized to force conformation of the ribbon-shaped catalytic precursor structures to the contour of the fibrous substrate. In (M3), the substrate is fibrous contour, the catalyst structure is involved by a ribbon conformation and catalyst structure is attached to the substrate by concurrently passing the catalyst structure and the substrate through an applicator die. In (M3), the applicator die is sized to force conformation of the catalyst structure to the fibrous contour of the substrate.