For several decades, biological fuel cells have drawn significant attention as alternative power sources since they are environmentally friendly and less expensive, compared to the conventional noble metal-based fuel cells. Some enzymatic biocatalysts such as glucose dehydrogenase and glucose oxidase consume glucose as fuel, generating electric currents if paired with an oxygen reduction electrode. While microbial biofuel cells inevitably require a physical barrier or proton exchange membrane between anode and cathode, enzyme-based biofuel cells allow a membraneless or single compartment design, since enzymes are very selective on redox species. For example, glucose dehydrogenase oxidizes the glucose fuel only, while it does not react with oxygen.

Strongly inspired by “Revolutionary Science” by Thoma Kuhn¹, this research presents a novel application of enzymatic, membraneless biofuel cell, which is an in vivo glucose sensor. The anode consisted of glucose dehydrogenase with co-immobilized NAD⁺ on a carbon paper substrate. For oxygen reduction catalyst at the cathode, laccase was coimmobilized with the redox mediator 2, 2-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS), on the same substrate. Firstly, for a proof of concept as a biofuel cell, the two electrodes were immersed in an open pool environment to achieve electrochemical result. Open circuit voltages (OCV) were monitored in parallel with polarization curves by potential sweep techniques. Secondly, half-cell experiments were performed to understand kinetics of anode and cathode, separately