Hydrogel Fiber Evaporator with Vertical Channels Integrated with Dual Heat Supply/Insulation Model for Continuous Solar Desalination

Abstract Hydrogel-based evaporators offer unique advantages for seawater desalination, yet the high verticalization of water transport channels remains significantly constrained by the random arrangement of polymers. Herein, a versatile and scalable “wet-spinning hydrogel fibers assisted with constrained alignment (HFCA)” strategy is proposed to fabricate hierarchically porous hydrogel fiber evaporator, achieving the perfectly vertical, large-scale spaces between adjacent fibers and small-scale pores within the hydrogel itself. The synergistic role of multiscale pores significantly enhances the siphon effect between fibers and the water transport capacity, while improving thermal localization, light absorption, and salt flux. Moreover, rather than employing the popular “heat isolation model”, a dual “heat supply/insulation model” is introduced for the first time in a three-dimensional evaporator, where a novel heating layer providing additional heat to the bulk water, along with an insulation layer minimizing heat loss. Together, these components create a positive net energy balance, transforming the single cold into a combined cold/hot evaporation manner on the side surface. Using this model, the HFCA evaporator exhibits the high evaporation rate (8.09 kg m −2 h −1 , 1 KW m −2 ) among the reported hydrogel-based evaporators and achieves exceptional outdoor evaporation (64.74 kg m −2 for 9 h), accompanied with salt tolerance, anti-oil fouling, and self-cleaning capacities.