Facile approach for modulating wetting of hierarchically structured metallic surface

In this study, the authors fabricated a hierarchically structured aluminum surface through facile hot-water treatment and abrasive machining. The developed surfaces were composed of nanoflakes exhibiting extreme wetting states, superhydrophilicity (θ s less than 5°) and superhydrophobicity (θ s greater than 150°) following salinization. The engendered surface morphologies composed of different length scales showed a significant influence on the wetting and durability characteristics. The stability of the observed Cassie state showed a direct correlation with the geometric parameters, particularly the interspatial distance. The critical surface tension for the transition from the Cassie to the Wenzel state increased with the interspatial distance. The surfaces structured with a smaller interspatial distance also exhibited high wetting resilience under dynamic conditions involving single-droplet impacts corresponding to We = 585 owing to a high negative capillary pressure. Further, the fine-structured hierarchical surfaces also exhibited appreciable antifogging and anticorrosion characteristics. Under simulated rain testing, the fine-structured hierarchical surfaces showed better durability than the coarser counterpart, enduring low contact angle hysteresis (CAH) (<10°) even after multiple cycles. Further, weathering tests performed on these samples showed an insignificant influence on their de-wettability. The present study highlights the fabrication of durable metallic surfaces through facile and sustainable fabrication method for multifunctional applications.