Long‐Term Immersion Study for Durability of Interconnected Micropatterned Surfaces with Sustained Water Repellency

Abstract The sustained water repellency of interconnected micropatterned surfaces is explored over an extended duration, with a focus on their resilience during a 90‐day water‐immersion test. Initially, the microstructure surfaces exhibit high water repellency, a characteristic of the Cassie–Baxter state. However, subsequent detailed temporal analyses reveal varying responses depending on the structural topology. The interconnected micropatterned surfaces exhibit remarkable long‐term resistance to water; this is attributed to the formation of large and stable air pockets enabled by their unique microcavity structures. In comparison, hierarchical microcavity surfaces with micropillars exhibit a notable decrease in water repellency, as evidenced by reduced contact angles, suggesting a transition to a wetting state owing to the emergence of surface hydrophilicity during long‐term water exposure. This study demonstrates the importance of stable air‐pocket effects, particularly in applications where the long‐term stability of liquid repellency is critical, and suggests the role of interconnected structures in maintaining water repellency over time.