Vertically aligned carbon nanotubes (VACNT) surfaces coated with polyethylene for enhanced dew harvesting

In this work we prepared vertically aligned carbon nanotubes (VACNT) based super-hydrophobic surfaces with enhanced dew condensation. Coating these VACNT with a nanometric polyethylene (PE) layer preserved morphology, but normalized surface energy increasing its super-hydrophobicity. Samples of as grown VACNT with the PE coating (VACNT-PE samples) and VACNT samples treated by CO2 laser and with PE coating (VACNT/laser-PE samples) show a much higher condensation for low surface temperatures (TS < 288 K). At this low temperature, it changes from a low adhesion Cassie Baxter wetting state to a more adhesive one. Despite this larger adhesion, water collection enlarges instead of decreasing. Hierarchical condensation is the most likely effect contributing for this further increase. The cage-like morphology left by laser tracks on VACNT/laser-PE sustain larger droplets that removes all water underneath and neighbor regions while moving. In these conditions the volume collection is over 30 times larger than at dew point, with a high volumetric efficiency.