A Miniature Membrane-less Biofuel Cell Operating under Physiological Conditions at 0.5 V

A biofuel cell operating at a power density of 50 μW cm −2 at a 0.5 V cell potential under physiological conditions (air saturated, pH 7.4, 0.14 M NaCl, 37.5°C, 15 mM glucose) is described. The cell had a glucose electro-oxidizing anode and an electroreducing cathode. The anodic electrocatalyst comprised the electrostatic adduct of glucose oxidase (GOx) a polyanion at physiological pH, and the polycationic redox polymer poly ( N -vinyl imidazole), partially quarternized with 2-bromoethylamine and partially complexed with vs. Ag/AgCl). The cathode electrocatalyst was the electrostatic adduct of bilirubin oxidase (BOD) also a polyanion at physiological pH, and the polycationic redox copolymer of polyacrylamide and poly ( N -vinylimidazole), complexed with where vs. Ag/AgCl). The anode and the cathode were 7 μm diam, 2 cm long carbon fibers, on which the catalytic enzyme-redox polymer adducts were cross-linked. When the miniature cell operated at 0.5 V, its 50 μW cm −2 initial power density decreased to 30 μW cm −2 after 2 days of continuous operation at 37.5°C.