Planar Multiplexing of Microfluidic Fuel Cells

Microfluidic fuel cells eliminate the membrane by utilizing parallel colaminar flow of electrolyte between the anode and cathode electrodes. When operated on vanadium redox electrolyte, these cells also eliminate the need for catalyst. Hence, microfluidic fuel cells are promising contenders in terms of achieving useful performance levels for commercial applications while being cost-effective on a commercial scale. However, due to the inherent size of these devices the power output is relatively low and scale-up is a major challenge. In the present article, two planar cell multiplexing strategies are introduced, featuring a nonsymmetric unilateral design and a symmetric bilateral device architecture, both of which employ two cells with shared fluidic inlet ports. The fuel cell design is based on flow-through porous carbon electrodes using vanadium redox electrolytes as reactants. In both array architectures, the two cells are fluidically connected in parallel and electrically in series. The main challenge of achieving uniform flow distribution is assessed using laminar flow theory and computational fluid dynamics and validated experimentally. The normalized performance obtained with the two prototype array cells is found to be equivalent to previously reported data for single cells, in this case doubling the device level voltage and power output and reaching 820 and 1200 mW/cm² peak power density for the nonsymmetric unilateral and symmetric bilateral array designs, respectively. It is, thus, demonstrated that both unilateral and bilateral planar multiplexing strategies are feasible for microfluidic fuel cell technologies and are shown to be particularly effective when the flow sharing between different cells is equal.