Bio-inspired surfaces via polydimethylsiloxane treated polycarbonate, for durable and cost-efficient atmospheric water harvesting

We propose a cost-efficient method for fabricating bio-inspired wettability patterns on polycarbonate (PC) surfaces. The surface is modified through polydimethylsiloxane (PDMS) treatment and UV-ozone irradiation, achieving water contact angles of 101.3 ± 3.0° (hydrophobic regions) and 34.0 ± 3.0° (hydrophilic regions). Unlike pure PDMS elastomers, the patterned PDMS-treated PC showed no hydrophobic recovery over 3 months in ambient air, making it suitable for large-scale fog collectors and atmospheric water harvesting devices with durable sorbents. We then fabricated multiple wettability patterns and tested them under constant fog flux at inclination angles of 60° and 30°. The five-pointed star pattern provided the best performance, achieving a fog collection rate enhancement of 2.06× (vs. fully hydrophobic) and 1.82× (vs. fully hydrophilic) at 30°, and 2.41× (vs. fully hydrophobic) and 3.07× (vs. fully hydrophilic) at 60°. This pattern and the base hydrophobic surface were then integrated with a LiCl/CaCl₂ hygroscopic hydrogel-matrix device, emulating the collection phase of ambient-air atmospheric water harvesting. The star pattern collector achieved 55% higher water collection than the fully hydrophobic baseline. These results demonstrate the potential of this approach for atmospheric water harvesting applications.