Self-feeding paper based biofuel cell/self-powered hybrid μ-supercapacitor integrated system

For the first time, a paper based enzymatic fuel cell is used as self-recharged supercapacitor. In this supercapacitive enzymatic fuel cell (SC-EFC), the supercapacitive features of the electrodes are exploited to demonstrate high power output under pulse operation. Glucose dehydrogenase-based anode and bilirubin oxidase-based cathode were assembled to a quasi-2D capillary-driven microfluidic system. Capillary flow guarantees the continuous supply of glucose, cofactor and electrolytes to the anodic enzyme and the gas-diffusional cathode design provides the passive supply of oxygen to the catalytic layer of the electrode. The paper-based cell was self-recharged under rest and discharged by high current pulses up to 4 mA cm⁻². The supercapacitive behavior and low equivalent series resistance of the cell permitted to achieve up to a maximum power of 0.87 mW cm⁻² (10.6 mW) for pulses of 0.01 s at 4 mA cm⁻². This operation mode allowed the system to achieve at least one order of magnitude higher current/power generation compared to the steady state operation.