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The direct integration of paper-based microfluidic fuel cells (μFC's) toward creating autonomous lateral flow assays has attracted attention. Here, we show that an air-breathing paper-based μFC could be used as a power supply in pregnancy tests by oxidizing the human urine used for the diagnosis. We present an air-breathing paper-based μFC connected to a pregnancy test, and for the first time, as far as we know, it is powered by human urine without needing any external electrolyte. It uses TiO 2 -Ni as anode and Pt/C as cathode; the performance shows a maximum value of voltage and current and power densities of ∼0.96 V, 1.00 mA cm − 2 , and 0.23 mW cm − 2 , respectively. Furthermore, we present a simple design of a paper-based μFC's stack powered with urine that shows a maximum voltage and maximum current and power densities of ∼1.89 V, 2.77 mA cm − 2 and 1.38 mW cm − 2 , respectively, which powers the display of a pregnancy test allowing to see the analysis results. [ABSTRACT FROM AUTHOR]

The research aims were to construct an air-breathing paper-based microfluidic fuel cell (paper-based μ FC) and to evaluated it with different soft drinks to provide energy for their prospective use in portable devices as an emergency power source. First, in a half-cell configuration, cyclic voltammetry showed that glucose, maltose, and fructose had specific oxidation zones in the presence of platinum-ruthenium on carbon (PtRu/C) when they were individual. Still, when they were mixed, glucose was observed to be oxidized to a greater extent than fructose and maltose. After, when a paper-based μ FC was constructed, PtRu/C and platinum on carbon (Pt/C) were used as anode and cathode, the performance of this μ FC was mostly influenced by the concentration of glucose present in each soft drink, obtaining maximum power densities at room temperature of 0.061, 0.063, 0.060, and 0.073 mW cm − 2 for Coca Cola ® , Pepsi ® , Dr. Pepper ® , and 7up ® , respectively. Interestingly, when the soft drinks were cooled, the performance was increased up to 85%. Furthermore, a four-cell stack μ FC was constructed to demonstrate its usefulness as a possible power supply, obtaining a power density of 0.4 mW cm − 2 , using Coca Cola ® as fuel and air as oxidant. Together, the results of the present study indicate an alternative application of an μ FC using soft drinks as a backup source of energy in emergencies. [ABSTRACT FROM AUTHOR]