For a concise demonstration of the optimized designs and the simulation results, we focus only on runs where the ratio of ohmic/kinetic resistance and the Darcy number were fixed as δ = 1.0 and Da = 10 -5 , respectively. For this setup, the visualized topology optimization results are depicted in Fig. , in which the optimal designs are shown in the presence and absence of fluid flow to illustrate its effect. The filtered design variable γ, representing the volume fraction of the solid phase in each RVE, was converted to a variable-porosity field and then mapped into the range of [10%, 90%]. The specified range is an arbitrary value for easier fabrication but should be tailored more precisely based on manufacturing constraints in future studies. Fig. shows a pattern in which the electrolyte phase gets closer to the membrane in cases with higher τ and the amount of the electrolyte phase in this region increases with higher applied current density λ.