Dew Water Harvesting by Functionalized Aluminum Surfaces: The Role of Surface Roughness and Wettability Properties on the Condensation Process and Water Collection Ability

• Aluminum surfaces with tailored topography and wettability are fabricated. • Droplet nucleation, growth, and harvesting are resolved under slow-condensation (low subcooling and undersaturation). • Smooth hydrophilic surfaces show the highest water collection performance. • Surface performance is governed by collection rate and condensation onset delay. Atmospheric water harvesting is emerging as a promising strategy to complement conventional freshwater resources. Significant efforts are devoted to the development of functional surfaces capable of, actively or passively, collecting water from the atmosphere through dew condensation. Surface roughness and wettability may enhance dew condensation and water removal. However, many previous studies have been conducted under supersaturated conditions, which can mask the influence of surface properties on the water harvesting process. In this work, the role of surface topography and wettability on dew water harvesting is investigated under realistic atmospheric conditions: low supersaturation and low subcooling. Aluminum surfaces with markedly different roughness and wetting characteristics were fabricated and tested under controlled subcooling. The complete condensation process, including droplet nucleation, growth, coalescence, and drainage, was systematically analyzed. Quantitative descriptors of droplet morphology, surface water coverage, and their temporal evolution were extracted. The results reveal a strong dependence of dew water harvesting performance on surface properties. Under low-saturation conditions, smooth surfaces with high surface energy and noticeable droplet adhesion exhibit the highest water harvesting efficiency. In addition, surface roughness does not enhance water collection for the surfaces used in this study. We observed that atmospheric water harvesting is mainly governed by two interrelated parameters: the onset of the drainage/collection process and the water harvesting rate. Optimal performance was achieved for surfaces providing an effective compromise between these two factors.