TECHNOLOGY FOCUS - BIOTECHNOLOGY - The enzyme comprises an oxidoreductase. The anode enzyme comprises a glucose oxidase, alcohol-based oxidase or cholesterol-based oxidase. The cathode enzyme comprises laccase, cytochrome C oxidase, bilirubin oxidase or peroxidase. The anode enzyme comprises oxygen oxidoreductase having an optimum activity at a pH of 6.5-7.5. The cathode enzyme comprises bilirubin oxidase. The anode enzyme comprises oxygen oxidoreductase having an optimum activity at pH of 6.5-7.5. The electron mediator comprises a metalloprotein, a conjugated organic compound, a sugar, a sterol, a fatty acid, or a coenzyme or substrate of an oxidase. The oxidized form of the electron mediator comprises stellacyanin, bilirubin, glucose or cholesterol (preferably bilirubin).    TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Components: The enzyme immobilization material further comprises an oxidized form of electrocatalyst which gains electrons from the electron conductor to produce a reduced form of electrocatalyst that can react with oxidized form of the electron mediator to produce a reduced form of the electron mediator and an oxidized form of the electrocatalyst. The non-planar shape of the biocathode or bioanode is alternating, bent, arcuate, folded, zigzag, spiral, coiled, or wound. The porous insulating material has a hole size of 0.06-0.75 cm, a thickness of 0.1-0.75 cm, and a nominal open area of 15-70%. The enzyme immobilization material can immobilize and stabilize the enzyme. The electron mediator (M1) is present in a concentration to make the enzyme immobilization material conduct electrons. The enzyme immobilization material comprises a micellar or inverted micellar structure comprising a modified perfluoro sulfonic acid-polytetrafluoroethylene (PTFE) copolymer. The bioanode comprises a pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase. The PQQ-dependent alcohol dehydrogenase has a PQQ molecule electrostatically associated with it. The bioanode and biocathode are not separated by a salt bridge or a polymer electrolyte membrane.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The electron conductor comprises a carbon-based material, a metallic conductor, a semiconductor, a metal oxide or a modified conductor (preferably a carbon-based material). The carbon-based material is selected from carbon cloth, carbon paper, carbon screen printed electrodes, carbon black, carbon powder, carbon fiber, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanotube arrays, diamond-coated conductors, glass carbon, mesoporous carbon, graphite, uncompressed graphite worms, delaminated purified flake graphite, high performance graphite, highly ordered pyrolytic graphite, pyrolytic graphite or polycrystalline graphite. The enzyme immobilization material is modified with a hydrophobic cation larger than NH4+ ion. The hydrophobic cation comprises an ammonium-based cation, quaternary ammonium cation, alkyltrimethylammonium cation, organic cation, phosphonium cation, triphenylphosphonium, pyridinium cation, imidazolium cation, hexdecylpyridinium, ethidium, viologen, methyl viologen, benzyl viologen, bis(triphenylphosphine)iminium metal complex, bipyridyl metal complex, phenanthroline-based metal complex, (Ru(bipyridine)3)2+, or (Fe(phenanthroline)3)3+. Or the the hydrophobic cation comprises a quaternary ammonium cation represented by formula (NR1R2R3R4)+. The modified perfluoro sulfonic acid-PTFE copolymer is modified with tetrabutylammonium halide, triethylhexylammonium halide or trimethyldodecylammonium halide (preferably triethylhexylammonium halide). The concentration of the electrocatalyst is from about 10 mM to 3 M (preferably 250 mM to 2.25 M, more preferably 500 mM to 2 M, most preferably 1-1.5 M). The oxidant is oxygen or peroxide (preferably oxygen), or air.R1-R4=H, hydrocarbyl (optionally substituted), or heterocyclyl (preferably H, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl or tetradecyl, more preferably methyl, ethyl, propyl, butyl, pentyl or hexyl).Provided that at least one of R1-R4 is other than H.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The electrocatalyst for the electron mediator comprises organometallic cations with standard reduction potentials greater than +0.4 volts. The electrocatalyst comprises osmium, ruthenium, iron, nickel, rhodium, rhenium, or cobalt complexes. The reduced form of the electrocatalyst for the electron mediator comprises Ru(phen)3+2, Fe(phen)3+2, Ru(bpy)3+2, Os(bpy)3+2, or Os(terpy)3+2 (preferably Ru(bpy)3+2). The fuel fluid comprises ammonia, methanol, ethanol, propanol, isobutanol, butanol and isopropanol, allyl alcohols, aryl alcohols, glycerol, propanediol, mannitol, glucuronate, aldehyde, carbohydrates, glucose, glucose-1, D-glucose, L-glucose, glucose-6-phosphate, lactate, lactate-6-phosphate, D-lactate, L-lactate, fructose, galactose-1, galactose, aldose, sorbose, mannose, glycerate, coenzyme A, acetyl Co-A, malate, isocitrate, formaldehyde, acetaldehyde, acetate, citrate, L-gluconate, beta-hydroxysteroid, alpha-hydroxysteroid, lactaldehyde, testosterone, gluconate, fatty acids, lipids, phosphoglycerate, retinal, estradiol, cyclopentanol, hexadecanol, long-chain alcohols, coniferyl-alcohol, cinnamyl-alcohol, formate, long-chain aldehydes, pyruvate, butanal, acyl-CoA, steroids, amino acids, flavin, hydrogenated nicotinamide adenine dinucleotide (NADH), NADH2, NADPH, NADPH2 or hydrogen (preferably methanol, ethanol or propanol, especially ethanol).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The porous insulating material is selected from a mesh fabricated from polypropylene, polyethylene, nylon, polyvinyl chloride, polytetrafluoroethylene, polyester, ethylene vinyl acetate, thermoplastic polymers, and/or styrenic block copolymers. EXAMPLE - No suitable example given.