Utilizing femtosecond laser surface processing and xerogel embedment to control surface properties of aluminum 2219

Enhancing surface functionalities through femtosecond laser surface processing (FLSP) combined with xerogel embedment enables advanced control of surface properties. FLSP produces permanent hierarchical scaffold with high surface area and near-surface porosity, which is expected to improve the adherence of functional coatings. In this study, we examined the mechanisms of this two-step process on aluminum 2219, with a focus on confining functional xerogels to tune wettability. Specifically, trimethoxy(3,3,3-trifluoropropyl)silane (SiF3) xerogels were incorporated to achieve superhydrophobicity, while tetraethoxysilane (TEOS) xerogels were used to promote superhydrophilicity. Material characterization confirmed that FLSP generated self-organized mound-like structures with near-surface, porous oxide layers. Importantly, the xerogels were shown to infiltrate and adhere selectively within these porous oxide regions without penetrating the underlying bulk aluminum, demonstrating that the FLSP scaffold effectively confines the coating. The choice of embedment method and drying technique strongly influenced the resulting surface state. Wicking proved to be the most effective embedment approach, producing fewer surface cracks than submersion and preserving the roughness needed for wettability control. Among the hydrophobic samples, the solvent-exchanged, air-dried SiF3 coating achieved the highest contact angle (155.6°). This performance is attributed to solvent exchange reducing capillary stresses, preserving surface roughness and promoting fluorinated group segregation to the exterior surface while maintaining interior silanol bonding. In contrast, TEOS-embedded samples exhibited complete wetting as the surface hydroxyl (-OH) groups promoted rapid spreading of water across the porous network. Overall, this work establishes a controlled two-step fabrication strategy in which FLSP-created scaffolds accommodate and confine xerogel coatings for tuning surface properties.