Microfluidic‐Directed Photothermal Gel‐Granule Ensembles with Highly Programmable Structures and Functionalities

ABSTRACT Solar‐driven interfacial evaporation by gel‐based materials stands as a promising strategy to alleviate freshwater scarcity. However, the conventional monolithic gel constituted with randomly oriented polymeric walls significantly increases the diffusion/transfer resistance of water and contained matters. Here, we demonstrate a gel‐granule ensemble evaporator, featuring programmatically assembled structures and functionalities, for enhanced solar evaporation and synergistic applications. Unlike the nano‐microchannels inherent in monolithic gels, the microfluidic‐directed ensemble of photothermal gel‐granules, assembled through self‐healing forces, creates unique interconnected gaps that facilitate efficient light absorption, thermal management, and mass transfer, leading to a higher content of intermediate water and a reduced evaporation enthalpy. A 3D ensemble evaporator attains an evaporation rate of 3.2 kg m −2 h −1 under 1 sun, and demonstrates exceptional salt resistance thanks to powerful capillary action and compensatory flows driven by the Marangoni effect. By substituting photothermal components with functional materials, photocatalysis, fluorescence, and structural colors are readily customized, expanding the in situ practical application of solar evaporators. This work not only brings new inspiration for the design of high‐performance solar evaporators, but also fosters the advancements of microfluidic techniques in efficiently constructing multifunctional, sustainable energy conversion materials.