TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The enzyme immobilization materials comprises the electron mediator optionally with an electrocatalyst, where the enzyme immobilization material is capable of immobilizing and stabilizing the enzyme, the material is permeable to the oxidant, an oxidized form of the electron mediator is capable of gaining electrons from the electron conductor to produce a reduced form of the electron mediator, and the electron mediator is present in a concentration sufficient to make the enzyme immobilization material conduct electrons. The oxidized form of the electrocatalyst is capable of gaining electrons from the electron conductor to produce a reduced form of the electrocatalyst that is capable of reacting with an oxidized form of the electron mediator to produce a reduced form of the electron mediator and an oxidized form of the electrocatalyst. The enzyme immobilization material comprises a micellar or inverted micellar structure. The enzyme immobilization material comprises a modified perfluoro sulfonic acid-PTFE copolymer. The electron conductor comprises a carbon-based material, a metallic conductor, a semiconductor, a metal oxide or a modified conductor. The electron conductor comprises a carbon-based material. The electron conductor comprises 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+. 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+. The modified perfluoro sulfonic acid-PTFE copolymer is modified with trimethyldodecylammonium halide or preferably triethylhexylammonium halide or tetrabutylammonium halide. The enzyme comprises an oxidoreductase. The enzyme comprises a glucose oxidase, alcohol-based oxidase or cholesterol-based oxidase. The enzyme comprises laccase, cytochrome C oxidase, bilirubin oxidase or peroxidase. The enzyme comprises an oxygen oxidoreductase having an optimum activity at a pH of about 6.5-7.5. The enzyme comprises bilirubin oxidase. 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). The electrocatalyst for the electron mediator comprises organometallic cations with standard reduction potentials greater than +0.4 volts. The electrocatalyst for the electron mediator 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, Os(bpy)3+2, Os(terpy)3+2 or preferably Ru(bpy)3+2. The concentration of the electrocatalyst is about 100 mM to about 3M (preferably about 1 M to about 1.5M). The oxidant comprises peroxide or preferably oxygen. 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, NADH, NADH2, NADPH, NADPH2 or hydrogen (preferably ethanol). The anode is a bio anode comprising a modified perfluoro sulfonic acid-PTFE copolymer (modified with tetrabutylammonium halide, trimethyldodecylammonium halide or preferably triethylhexylammonium halide). The bioanode comprises a PQQ-dependent alcohol dehydrogenase, which has a PQQ molecule electrostatically associated with it. The bioanode and biocathode are not separated by a salt bridge or a polymer electrolyte membrane. The cathode enzyme is an oxygen oxidoreductase (preferably a bilirubin oxidase or a laccase). The electron transport mediator is immobilized within the buffered internal compartment of the membrane. The electron transport mediator is a transitional metal compound comprising ruthenium (preferably Ru(bpy)3+2). The membrane is a modified ion exchange polymer membrane. The membrane is a quaternary ammonium salt treated perfluoro sulfonic acid-PTFE copolymer. The membrane is a tetrabutylammonium bromide treated Nafion (RTM) membrane. The electron conductor is carbon felt. The bioanode comprises an electron conductor, a redox polymer film, a modified ion exchange polymer membrane and an anode enzyme that is immobilized within a buffered internal compartment of the modified ion exchange polymer membrane. The redox polymer film is a polymethylene green. The modified ion exchange membrane is a quaternary ammonium salt treated perfluoro sulfonic acid-PTFE copolymer. The anode enzyme is an oxidoreductase enzyme having an organic compound substrate; preferably an alcohol dehydrogenase. The bioanode comprises a second bioanode enzyme (preferably an aldehyde dehydrogenase). The fuel cell comprises a polymer electrolyte membrane to separate an anode compartment from a cathode compartment. The fuel cell does not comprise a salt bridge nor a polymer electrolyte membrane to separate an anode compartment from a cathode compartment. The oxygen oxidoreductase is a bilirubin oxidase and the substrate is oxygen. The anode oxidoreductase enzyme is an alcohol reductase and the organic fuel is an alcohol. The redox polymer is a polymethylene green. The modified anode/cathode ion exchange polymer is a quaternary ammonium bromide treated Nation (RTM) polymer. The electron transport mediator (preferably Ru(bpy)3+2) comprises a transition metal and aromatic ligand complex. The anode is a bioanode, which comprises a modified anode ion exchange membrane and at least one anode oxidoreductase enzyme, which is immobilized within a buffered compartment of the modified anode ion exchange membrane. The bioanode comprises a first anode oxidoreductase enzyme and a second anode oxidoreductase enzyme, which are immobilized within the buffered compartment of the modified anode ion exchange membrane, where the first anode oxidoreductase enzyme is an alcohol dehydrogenase and the second anode oxidoreductase enzyme is an aldehyde dehydrogenase. The modified ion exchange membrane is a quaternary ammonium salt treated perfluoro sulfonic acid-PTFE copolymer. The modified ion exchange membrane is a tetrabutylammonium bromide treated Nation (RTM) membrane. The cathode enzyme is immobilized within a buffered micelle of the modified ion exchange membrane and an oxygen oxidoreductase enzyme. The cathode enzyme is a bilirubin oxidase. The electron transport mediator comprises a transition metal and an aromatic ligand together as a complex. The hydrophobic cation comprises a quaternary ammonium cation of formula R4-N+(R1)(R3)-R2.R1-R4 = H, hydrocarbyl, substituted hydrocarbyl or heterocyclo (where at least one of R1-R4 is other than H); preferably H, CH3, CH3CH2, propyl, butyl, pentyl or hexyl (where at least one of R1-R4 is other than H).