Background
Water scarcity remains a pressing global challenge, and conventional atmospheric water harvesting methods often struggle to balance efficiency with environmental sustainability. Existing technologies frequently rely on synthetic polymers or saltâpolymer hybrids that exhibit issues such as limited water uptake under low relative humidity, high energy requirements for water release, and undesired salt leakage, which compromise their long-term viability and scalability. Academic studies have highlighted these limitations, revealing that while some materials show promise in controlled settings, their performance drops under variable outdoor conditions and they can pose environmental risks. Moreover, the integration of naturally abundant, renewable resources into these systems has been hampered by difficulties in achieving consistent, energy-efficient operation, prompting ongoing research into more adaptive and sustainable approaches.
Technology overview
A two-step molecular engineering process modifies natural polysaccharides such as cellulose, starch, and chitosan to create hydrogels that both capture and release water efficiently. Initially, an alkylation to graft thermoresponsive groups modifies the biomass to facilitate water uptake and stabilize hygroscopic salts even at low relative humidity, while subsequent zwitterionic functionalization further enhances absorption and prevents salt leakage. The thermoresponsive component enables the stored water to be released at moderate temperatures (50-60°C), reducing energy consumption compared to conventional methods. This method yields a generalizable and sustainable platform for producing atmospheric water harvesting sorbents with demonstrated outdoor performance.
Benefits
- Eco-friendly sustainability: The invention uses natural biomass (cellulose, starch, and chitosan) instead of petroleum-based synthetic polymers, reducing environmental impact and material costs compared to conventional sorbents.
- Broad relative humidity operability: It efficiently captures atmospheric water across a wide range of humidity levels (10-100% RH), outperforming traditional approaches that require higher humidity conditions for effective performance.
- Energy-efficient regeneration: The thermoresponsive property enables water release at moderate temperatures (50-60°C), significantly lowering energy consumption compared to existing methods that demand high energy input for water desorption.
- Salt leakage prevention: The zwitterionic functionalization stabilizes hygroscopic salts within the hydrogel matrix, addressing the common issue of salt leakage found in traditional salt-polymer hybrid sorbents as highlighted in prior studies (e.g., Hanikel et al., Science 2021).
- Versatility and customizability: The generalizable two-step molecular engineering strategy can be applied to multiple natural polysaccharides, offering a platform for developing tailored sorbents for diverse applications such as humidity control, passive cooling, and sustainable agriculture.
Applications
- Atmospheric water harvesting systems: This use case leverages the energy-efficient, scalable water capture and release properties of the hydrogel to generate potable water in arid regions, remote areas, and disaster relief scenarios.
- Industrial humidity control and passive cooling solutions: This application utilizes the material’s moisture regulation and low-energy water release capabilities to maintain optimal humidity and support passive cooling in industrial and architectural environments.
- Specialized moisture-control packaging: This line of business applies the customizable hydrogel technology to control humidity within packaging, thereby preserving the quality of moisture-sensitive pharmaceuticals and food products.
Publication
“Molecularly Functionalized Biomass Hydrogels for Sustainable Atmospheric Water Harvesting,” Weixin Guan, Yaxuan Zhao, Chuxin Lei, Yuyang Wang, Kai Wu, and Guihua Yu, Advanced Materials, early view, Feb. 13, 2025 (https://doi.org/10.1002/adma.202420319).
