The research aims were to construct an air-breathing paper-based microfluidic fuel cell (paper-based $\mu$ 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 $\mu$ FC was constructed, PtRu/C and platinum on carbon (Pt/C) were used as anode and cathode, the performance of this $\mu$ 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 ${}^{\circledR }$ , Pepsi ${}^{\circledR }$ , Dr. Pepper ${}^{\circledR }$ , and 7up ${}^{\circledR }$ , respectively. Interestingly, when the soft drinks were cooled, the performance was increased up to 85%. Furthermore, a four-cell stack $\mu$ 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 ${}^{\circledR }$ as fuel and air as oxidant. Together, the results of the present study indicate an alternative application of an $\mu$ FC using soft drinks as a backup source of energy in emergencies.

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.