Rollable and Ventilated Net‐Based Solar Thermal Water Evaporator for Casting on Water Surface

The solar‐thermal evaporator provides a sustainable freshwater production strategy, of which the large‐scale floating applications on river or sea still confront the challenge of the highly efficient flexible evaporator. However, existing flexible evaporators often use porous gel to load solar‐thermal materials, which only allow water to evaporate out from outermost surface but waste heat by dissipating into bulky water. Herein, a rollable and ventilated flexible solar‐thermal evaporator based on dendritic net substrate is presented, which can be cast in a scalable way on waving water surface. Compared to that of the porous gel, the dendritic structure can not only capture photons efficiently, but also enlarge the ratio of water evaporation area to heat dissipation area by over 109 times, with efficient water transfer path of merely 0.3 cm length in average for even 1 m² water evaporation area. The flexible evaporator can achieve a photothermal evaporation temperature of 108 °C and an evaporation rate of >1.46 kg m⁻² h⁻¹@1 sun illumination. A sustainable ecological circulation evaporation system is demonstrated to show its potential for scalable floating‐on‐sea applications.