Unifying Physics, Structure, and Function in Solar Interfacial Evaporation: A Multiscale Perspective

Solar interfacial evaporation (SIE) has emerged as a low-carbon, sustainable route for seawater desalination and water purification, yet its development remains constrained by intrinsic heat loss, vapor-diffusion resistance, and insufficient interfacial energy management. Furthermore, advances in materials and architectures necessitate a unified theoretical foundation. This review establishes a multiscale theoretical framework that integrates thermodynamics, transport phenomena, material-fluid interactions, and system-level functionality to bridge these gaps. The coupled roles of thermal regulation and vapor-diffusion kinetics are analyzed across diverse evaporator architectures, from planar and sandwich structures to multisurface and volumetric 3D designs. Key intrinsic design elements, including photothermal materials, interfacial wettability, water-transport channels, and salt-removal mechanisms, are systematically examined, alongside multi-field synergistic strategies incorporating optical, thermal, aerodynamic, and electrical assistance for enhanced and all-weather operation. Emerging multifunctional systems that couple evaporation with condensation, catalysis, and selective ion recovery are further discussed. By unifying physical principles with structural and functional design strategies, this review offers a conceptual roadmap for standardized performance evaluation, multifunctional integration, and the rational development of next-generation solar-driven water and water-energy-resource systems.