Dual‐Scale Channels of Hollow Reed Stem Toward Synergistic Thermal and Water Management in Solar Evaporation

ABSTRACT Interfacial solar vapor generation presents a promising avenue for sustainable freshwater production. However, its practical implementation is impeded by high energy cost, salt accumulation, and unstable water supply. Inspiration, drawn from natural reeds, effectively transports water across long distance. The evaporator utilizes the hierarchical and porous vascular bundles as optimal channels for spontaneous water pumping. Various reeds are systematically evaluated before and after delignification. These findings show that the reeds with hollow structure facilitate thermal localization through their internal air gaps while enabling rapid vapor escape via its central cavity. This innovative design yields the superior evaporation performance that significantly exceeds that of solid reeds, exhibiting a distinctive and positive size effect up to a certain scale. Microscopic characterization indicates that the microstructures of hollow reeds, coupled with enhanced hydrophilicity resulting from delignification, collectively ensure rapid capillary water transport. Furthermore, numerical simulations confirm that the evaporation performance can be further optimized by adjusting wall thickness. This work introduces a bio‐inspired structural prototype spanning both micro‐ and macroscales for water evaporation. It demonstrates the substantial potential of engineered natural materials for automatic pumping, structural stability, and resistance to salt fouling within sustainable water purification technologies.