A lactate/O-2 enzymatic biofuel cell (EBFC) was prepared as a potential power source for wearable microelectronic devices. Mechanically stable and flexible nanoporous gold (NPG) electrodes were prepared using an electrochemical dealloying method consisting of a pre-anodization process and a subsequent electrochemical cleaning step. Bioanodes were prepared by the electrodeposition of an Os polymer and Pediococcus sp. lactate oxidase onto the NPG electrode. The electrocatalytic response to lactate could be tuned by adjusting the deposition time. Bilirubin oxidase from Myrothecium verrucaria was covalently attached to a diazonium-modified NPG surface. A flexible EBFC was prepared by placing the electrodes between two commercially available contact lenses to avoid direct contact with the eye. When tested in air-equilibrated artificial tear solutions (3 mM lactate), a maximum power density of 1.7 +/- 0.1 mu W cm(-2) and an open-circuit voltage of 380 +/- 28 mV were obtained, values slightly lower than those obtained in phosphate buffer solution (2.4 0.2 mu W cm(-2) and 455 +/- 21 mV, respectively). The decrease was mainly attributed to interference from ascorbate. After 5.5 h retained 20% of the initial power output. of operation, the EBFC retained 20% of the initial power output.