Laser-thermal-induced dual-surface modification of copper: Influence of morphology and oxidation on wettability and water spreading behaviour

Laser-induced thermally engineered copper surfaces provide an effective approach for tailoring surface micro/nanostructures and modifying the surface chemical phases. In this study, four copper specimens (LTCu1–LTCu4; 1 × 1 cm, 0.5 mm thick) were processed using a continuous-wave fiber laser system (MLS F20), and their wettability, morphology, chemical phase composition, and crystallinity were systematically evaluated. A key aspect of this study was the investigation of the reverse (non-irradiated) surface, which exhibited distinct modifications resulting from secondary thermal diffusion through the copper substrate. FE-SEM analysis revealed characteristic microdimples and nanoscale pores on the laser-treated front surfaces, whereas the untreated backside surfaces developed nanoscale clusters attributed to thermally induced oxidation and heat propagation. Water contact angle measurements showed lower contact angles on the laser-treated surfaces (68–73°) than on the untreated backside surfaces (77–82°), confirming the combined influence of direct laser irradiation and indirect thermal diffusion on surface wettability. Elemental and crystallographic analyses (EDS and XRD) indicated the formation of Cu 2 O and CuO phases, which contributed to the enhanced hydrophilicity and moisture affinity. Overall, the results demonstrate that continuous-wave laser processing can simultaneously modify both directly irradiated and indirectly heat-affected copper surfaces, providing new insights into the dual-surface evolution during laser treatment. The laser-modified copper surfaces developed in this study exhibited altered nanoscale morphology, wettability, and water spreading characteristics. These findings enhance the understanding of laser-induced dual-surface modification of copper and may provide a basis for future investigations related to thermal management and water-harvesting systems.