Purpose-Driven Design and Manufacturing of Hydrogel Sorbents for Efficient Atmospheric Water Harvesting

Hydrogel-based sorption atmospheric water harvesting (H-SAWH) offers a promising solution to water scarcity, particularly in arid regions. Hydrogels, with their three-dimensional (3D) polymer networks, exhibit excellent hygroscopicity, tunable structure, and chemical adaptability, making them strong candidates for next-generation water capture systems. This review introduces a purpose-driven polymer engineering approach that incorporates environmental and application-specific constraints into the molecular design of hydrogels, moving beyond the traditional focus on maximizing water uptake. Diverse H-SAWH applications, from portable devices to agricultural systems, are highlighted, and key material requirements, including responsive water release, mechanical durability, and climate resilience, are identified. Hydrogels are conceptualized as customizable water reservoirs, with tailored porosity, stimuli-responsive features, and hygroscopic additives designed to enhance vapor capture and release cycles. Advances in synthesis methods, including precision crosslinking and salt integration strategies, are reviewed for their role in improving system robustness and performance. Persistent challenges related to salt leakage, water purity, scalability, and environmental durability are critically assessed from a molecular perspective. Finally, the importance of field validation and techno-economic analysis is emphasized to ensure real-world deployment. This review frames the future of H-SAWH as a convergence of smart polymer design and sustainable water technology for decentralized, climate-resilient freshwater access.