Leaf Vein-Inspired Hierarchical Wedge-Shaped Tracks on Flexible Substrate for Enhanced Directional Water Collection.

Water collection has been extensively researched due to its potential for mitigating the water scarcity in arid and semiarid regions. Numerous structures mimicking the fog-harvesting strategy of organisms have been fabricated for improving water-collecting efficiency. In this contribution, we demonstrate four-level wedge-shaped tracks inspired by leaf vein for enhancing directional water collection. Superhydrophilic Cu(OH)2 nanowires are introduced and prepared on flexible hydrophobic polyethylene terephthalate (PET) substrates by alkali-assisted surface oxidation at room temperature. They provide abundant capillary paths for promoting droplet absorption and forming water film tracks. Then, the hierarchical wedge-shaped tracks enable the water to be transported to a certain accumulation region spontaneously owing to the continuous Young-Laplace pressure difference. As a result, the four-level wedge-shaped tracks on PET substrate achieve the highest water-collecting efficiency, increasing by nearly 1150 and 510% compared to the bare PET and Cu(OH)2 nanowires on PET, respectively. After being bent for 105 cycles at a radius of 10 mm, the samples can still preserve high efficiency, indicating that the synthetic structures possess outstanding durability. Our approach provides a novel strategy for water collection and paves ways for directional liquid transportation and microfluidic devices.