Air-Breathing Microfluidic Fuel Cell Stack Powered by Tequila: Experimental Evaluation and Computational Fluid Dynamics Simulation of Series-Parallel Configurations Effect

Microfluidic fuel cells offer a promising route for portable power generation; however, scaling paper-based systems remains challenging because capillary-driven flow can limit fuel distribution and electrochemical performance. This work investigates the experimental performance and computational fluid dynamics (CFD) behavior of air-breathing paper-based microfluidic fuel cell (μFCs) stacks powered directly by commercial tequila (35 vol.% ethanol). Single cells with electrode areas ranging from 0.5 cm × 0.5 cm to 3 cm × 3 cm were evaluated to determine the optimal design, followed by the construction of 4-cell and 6-cell series-parallel stacks. The smallest electrode (0.5 cm × 0.5 cm) achieved the highest power density (0.142 mW cm−2) and open-circuit voltage (0.92 V). Scaling to a 6-cell stack increased the maximum power density to 3.20 mW cm−2 and the voltage to 1.39 V, outperforming the 4-cell configuration (1.09 mW cm−2 and 1.07 V). Computational Fluid Dynamics simulations revealed that fuel velocity decreased from 2.8 × 10−2 m s−1 near the inlet to approximately 1.0 × 10−6 m s−1 in the final cells because of porous-medium resistance, explaining the observed mass-transport limitations. The results demonstrate that tequila can be directly used as a sustainable fuel source and that optimized stack architectures significantly enhance power generation in paper-based microfluidic fuel cells.