A Hydrogel Evaporator with Adjustable Internal Water Content Distribution for Seawater Desalination

Interfacial solar evaporation represents a promising strategy to address global water scarcity. However, designing evaporators capable of maintaining optimal surface wettability to minimize heat loss while achieving high-efficiency clean water production remains a critical challenge. Here, we design a temperature-responsive hydrogel evaporator based on N-isopropylacrylamide (NIPAm), with a Lower Critical Solution Temperature (LCST), acrylamide (Am), and in situ polymerized polypyrrole (Ppy). The evaporator dynamically regulates water distribution via hydrophilic-lower hydrophilicity transition: the sunlight-exposed region becomes lower hydrophilicity (>LCST) to reduce heat loss, while the submerged region stays hydrophilic (