Capturing Nutrients and Water from Air

Fog harvesting offers a promising freshwater source, yet its potential remains significantly underexploited. To enhance harvesting efficiency, we designed a three-dimensional biomimetic cactus structure incorporating biphilic surfaces (hydrophilic spots on a hydrophobic substrate), optimized through aerodynamic flow manipulation and surface wettability control. The unique cylindrical hollow structure generates intensified internal vortices promoting fog droplet impaction and coalescence. Concurrently, biphilic surface optimization reduces the critical droplet detachment radius by 25.9% via controlled coalescence-induced jumping, facilitating droplet transport. Theoretical modeling, balancing gravitational and adhesion forces, identifies the optimal surface layout, achieving a water collection rate of 6.8 kg/m²/h—2.3 times higher than conventional mesh systems. Furthermore, we propose an integrated self-sufficient system. This combines the enhanced fog harvester with a spark discharge reactor powered by droplet-based electricity generation. The system passively captures water and synthesizes nitrate-based plant nutrients directly from the air. Proof-of-concept experiments demonstrate nitrogen fertilizer production at 2.38 mg per hour per liter of harvested water. This integrated approach presents a potentially sustainable and self-reliant solution for decentralized agriculture.