Humidity in the air is a vast water and energy resource available in any location. Air in the atmosphere contains six times more freshwater than that of all rivers and lakes. This moisture also carries over a thousand times more power than the global electricity demand. For over two centuries, numerous water sorbent materials have attempted to harness these resources. However, their performance, scalability, and durability have severely limited their potential. In this talk, I will discuss the material-level to application-level development of hydrogel-salt composites that capture record amounts of water from the air with low-cost (<$0.1/kg of material) and high durability.

I first developed physics-based models elucidating the key thermodynamic interactions and transport mechanisms in hydrogel-salt composites. Through comprehensive synthesis and characterization, I demonstrated that these models accurately predict the key sorption performance metrics (uptake, enthalpy, and kinetics) of hydrogel-salt composites from their composition. I then used these insights to 1) synthesize hydrogels with the highest capability ever demonstrated of any material to capture and store water from the air (~2 kg of water/kg of material), even in arid conditions (30% relative humidity), 2) design and demonstrate a device capable of producing >1 L/m2/day of water from humidity, and 3) develop a heat exchanger that converts moisture capture into heat. Beyond performance, I studied the hydrogel degradation mechanisms, probing an unexplored, yet critical parameter. Specifically, by preventing metal ion-mediated hydrogel degradation, I demonstrated >8-month material durability, exceeding previous state-of-the-art works and providing a path towards <$0.01/L water production from the air.

My rational, physics-based development of hydrogel-salt composites represents a significant step towards the utilization of ambient moisture and its energy for a wide range of applications. These results also open exciting scientific opportunities for leveraging the unconventional transport properties of hydrogels to address grand humanity challenges in the water-food-energy nexus.