The Spiral Drainage Slide with Biomimetic Spines Achieves High-Efficiency Fog Collection

The biomimetic cactus cone-shaped spines have reference significance for efficient fog water collection. However, most fog water collection devices focus on the Laplace driving force brought by thorns, but droplets are still subject to pinning forces from the roots of thorns during vertical detachment, which limits the collection rate. Here, we report a 3D biomimetic gradient wetting thorn rod (GWTR) using 2D superhydrophobic spine tape wrapped around superhydrophilic stainless steel wire. Selective spraying of the SiO2 superhydrophobic layer was fabricated on the thorny strip to obtain superhydrophilicity through acid alkali etching of the steel wire. Droplets driven by Laplace pressure difference and surface energy gradient are expelled downward along the superhydrophilic spiral channel upon reaching the surface of the rod, effectively alleviating the pinning phenomenon of droplets (56 mg vs 21 mg) and achieving a high fog water collection efficiency of 4.14 g cm-2 h-1. In addition, a 4 × 4 array composed of thorn rods can collect considerable fog water (∼83 g h-1) in a short period of time. This study used a simple and effective preparation process to design a fog collector with excellent stability and durability under acidic/neutral conditions.