Water harvesting from air using patterned wettability-contrast surfaces

• Main Author: Chen, Xingyu
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/175792
• Institution: Nanyang Technological University

The imminent global water shortage crisis, with a projected two-thirds of the world’s population facing water shortages by 2025, has intensified the need for innovative freshwater collection methods. This study investigates water condensation behaviors through a combination of lab experiments and simulations conducted on surfaces with single and patterned wettabilities. Glass slide surfaces were functionalized by a cost-effective, vacuum-free, and scalable sol-gel process with different wettabilities and roughness to lay a foundation for this research. Atmospheric water harvesting (AWH) efficiency was quantified using a Peltier cooling stage and an analytical weighing balance. To gain a deeper understanding of the condensation findings, the water contact angles (WCA) were measured using a goniometer, while the morphologies of diverse surfaces were characterized by FESEM and AFM. Surface chemical composition was identified by XPS. Observations of trade-offs in single surfaces between droplet transportation (preferably on hydrophobic surfaces) and growth (preferably on hydrophilic surfaces) highlighted the importance of surface patterning. To delve deeper into the working mechanisms, a multi-faceted approach was employed, integrating experiments with Molecular Dynamics (MD) and Python simulations. MD unveiled water vapor nucleation behaviors on different wetting surfaces. The integration of MD data into Python facilitated the visualization of condensation at the micron level and enabled precise calculations of harvesting efficiency on diverse patterned surfaces. Validation through the fabrication of patterned surfaces, using pure oxygen plasma treatment covered by 3D-printed photomasks with various sizes and shapes, affirmed the practicality of our findings. This study provides valuable scientific insights for designing future surface patterns for AWH.