Enhanced droplet detachment and actual water collection in atmospheric water harvesting via frost-melt regulation and 2D/3D Laplace hybrid structure

Atmospheric water harvesting is regarded as an effective approach to alleviate freshwater scarcity. However, existing condensation–based atmospheric water harvesting methods generally suffer from low condensation efficiency and severe droplet retention on the growth surface, resulting in substantial difficulty in collecting a large fraction of the condensed water. Here, we propose a frost–coupled 2D/3D Laplace strategy for atmospheric water harvesting, in which frosting is used to replace conventional condensation to enhance interfacial water capture, while a 2D/3D hybrid structure enables rapid directional transport and collection of the melted droplets. In this structure, the 3D cones provide a large interfacial area to enhance vapor contact and heat transfer, thereby improving frost accumulation capacity. Meanwhile, a vertically integrated 2D hydrophilic–hydrophobic bamboo–joint wedge surface at the cone root rapidly drains retained droplets, overcoming the drainage limitation of purely 3D structures. The results show that droplet transport on the 3D cone can be achieved within 1.75 s, rapid guiding on the 2D surface can be completed within 3 s, and the hybrid structure enables directional droplet collection within 5 s. Ultimately, the system achieves a specific water harvesting capacity of 725.88 g·kWh⁻¹, which is approximately 5 times higher than that of a conventional condensation surface with the same area. This work provides a new route for improving atmospheric water harvesting performance through the synergy of frost–enabled enrichment and Laplace–driven drainage.