Cost‐Effective 3D‐Printed Bionic Hydrogel Evaporator for Stable Solar Desalination

Abstract Solar desalination using hydrogel evaporators is an eco‐friendly, highly efficient means with natural sunlight for sustainable freshwater production. However, it remains challenging to develop a cost‐effective and scalable method to prepare salt‐resistant hydrogel evaporators for stable desalination. Here, inspired by tree transpiration and hierarchical porous structure, a 3D‐printed bionic hydrogel evaporator (3DP‐BHE) is designed for long‐term solar desalination. Commercialized activated carbon (AC) is introduced into biomass starch skeleton as a solar light absorber to build 3DP‐BHE in a cost‐effective fashion ($10.14 m −2 of total materials cost). The bionic tree leaf layer for 94.01% light absorption and timely vapor diffusion. The bionic tree trunk layer with 3D printed bimodal porous structure for water transfer, thermal isolation, and salt ions convection and diffusion. With the unique bionic structure, the 3DP‐BHE achieves a stable evaporation rate of 2.13 kg m −2 h −1 at ≈90.5% energy efficiency under one sun (1 kW m −2 ). During the 7‐day desalination of 10 wt.% brine, a steady evaporation rate of 1.98 kg m −2 h −1 is maintained with a record‐high cost‐effectiveness (195.3 g h −1 $ −1 ) manner. This 3DP‐BHE will open significant opportunities for affordable solar desalination systems on multiple scales, from individual households to off‐grid communities.