Peng, Hsuan-YiHsuan-YiPengYeh, Kuan-YuKuan-YuYehLiu, Bang-YanBang-YanLiuLI-JEN CHEN2026-02-092026-02-092026-04-1500219797https://www.scopus.com/record/display.uri?eid=2-s2.0-105027340719&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/735870Hypothesis: The wetting behavior of a liquid drop on surfaces with varying hydrophilicity and hydrophobicity is crucial for fundamental research and practical applications. The conventional 90° contact angle threshold for distinguishing hydrophilic and hydrophobic surfaces has been debated. Experiments: This study systematically investigates advancing contact angles and wetting transitions on polydopamine-coated NOA81 substrates patterned with regular arrays of square micro-pillars. By controlling both the intrinsic surface wettability and microstructured roughness, we explore how these factors influence wetting behavior. Findings: The intrinsic advancing contact angles of the flat polydopamine-coated substrates (θAf) was tuned from 36.1° to 80.7°. Introducing square-pillar roughness substantially broadened the advancing contact angle (22° to 158°), revealing distinct roughness-dependent wetting behaviors for each θAf. Two transition-capability regimes were identified: when θAf > 80°, roughening enables a hydrophobic Wenzel-to-Cassie transition; while θAf < 55°, increasing roughness induces a hydrophilic Wenzel-to-hemiwicking (penetrating) transition. These results demonstrate that the characteristic θAf governs whether roughening activates hydrophobic or hydrophilic wetting pathways on square-pillar microstructured surfaces. The framework established here refines our understanding of roughness-mediated wetting transitions and provides practical guidance for designing microstructured surfaces with tailored wetting properties.falseadvancing contact anglehemiwicking statehydrophilichydrophobicmicrostructured surface roughnesspolydopamine coatingjournal article10.1016/j.jcis.2025.1398012-s2.0-105027340719