The polymer electrolyte membrane fuel cell (PEMFC) generates electrical energy through electrochemical reactions and is a key technology for sustainable energy. The electrolyte membrane significantly affects performance under varying conditions. This study examines the impact of membrane thickness and relative humidity (RH) on PEMFC performance using j-V curves and electrochemical impedance spectroscopy (EIS). Experiments were conducted with membrane thicknesses of 30, 15, and 5 μm under RH conditions of 100%-100% and 100%-0%. Under RH 100%-100%, performance improved as the membrane thickness decreased, with values of 954, 1050, and 1235 mW/cm² for the 30, 15, and 5 μm membranes, respectively. The 5 μm membrane demonstrated a 23% performance improvement over the 30 μm membrane. Under RH 100%-0%, performances were 422, 642, and 852 mW/cm², with degradation rates of 55.8%, 39.0%, and 32.1%. The 5 μm membrane exhibited the lowest degradation rate, indicating superior performance under low humidity. These results suggest that thinner membranes generally enhance performance and maintain efficiency even in dry conditions.
In this paper, we propose a novel method for controlling the anisotropic sliding behavior of droplets using multiscale hierarchical structures. First, we employed a silicon wafer mold containing micro-pillars and directional micro-line structures to induce the directional sliding of droplets. Additionally, we fabricated micro-cone patterns and integrated them into the structures to precisely control droplet movement. These two structures were replicated in polymer and subsequently fused into a single multiscale hierarchical mold through a partial curing process. The completed multiscale hierarchical surface was then replicated with PDMS to create anisotropy that governs the direction of droplet movement. We experimentally confirmed that the degree of sliding is influenced by the cone pattern. Our proposed structural design demonstrates that anisotropic wettability control is achievable even on surfaces made from a single material, indicating potential applications in various fields such as microfluidics, sensors, and functional surfaces.
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