Size-Insensitive Vapor Diffusion Enabled by Additive Freeze-Printed Aerogels for Scalable Desalination

Porous materials are widely used as photothermal evaporators for solar-powered desalination. However, conventional evaporators suffer a significant performance decline as size increases, limiting the scalability from laboratory to practical scales. This work addresses the fundamental limitation behind the size-performance trade-off through modeling-guided design and additive manufacturing. A coupled heat and vapor transport model reveals that vapor diffusion resistance increases with evaporator size due to thickened boundary layers. A hierarchical porous aerogel fabricated by using an additive freeze-printing technique decouples the boundary layer thickness from overall device dimension, achieving size-insensitive vapor diffusion. Unlike conventional evaporators that suffer over 40% reduction in evaporation performance with increasing size, the resulting aerogel maintains an evaporation rate above 2 kg m^-2 h^-1 and energy efficiency over 80%, with less than 5% reduction. Our findings provide new insights into the vapor diffusion mechanism in porous evaporators and offer a practical solution for scalable solar-driven desalination.