Ambient Pressure Drying of Aerogels for Structure Preservation and Multifunctional Applications

Ambient-pressure drying (APD) is attractive for scalable aerogel manufacturing because it avoids the pressure vessels used in supercritical drying and the low-temperature vacuum equipment required for freeze-drying. Its principal limitation is the liquid-gas meniscus generated during evaporation, which couples solvent surface tension, wetting, pore size, drying rate, and skeleton strength to shrinkage and cracking. This review establishes a process-structure-property framework for APD-derived aerogels. After defining the scope of APD and distinguishing it from the broader category of subcritical drying, we quantitatively analyze capillary pressure using the Young-Laplace relationship and discuss the absence of a universal critical contact angle or pore size. Physical, chemical, and hybrid crosslinking are compared in terms of synergistic reinforcement and possible competition caused by densification, brittleness, or blocked mass transport. The structural outcomes of APD are benchmarked against supercritical and freeze-drying, with emphasis on density, porosity, specific surface area, shrinkage, and mechanical integrity. Application sections then connect pore architecture and interfacial chemistry to thermal insulation, adsorption, energy storage, electromagnetic shielding, acoustics, and biomedical functions. Finally, environmental fate, solvent safety, reporting standards, and continuous manufacturing are identified as priorities for translating APD aerogels from laboratory demonstrations to reproducible products.