New Class Of Materials Passively Harvest Water From Air

Researchers at Penn Engineering have discovered a new class of nanostructured materials that can pull water from the air, which could enable new ways to collect water in arid regions and devices that cool electronics or buildings using the power of evaporation.

Aserendipitous observation in a chemical engineering lab at Penn’s School of Engineering and Applied Science has led to a surprising discovery: a new class of nanostructured materials that can pull water from the air, collect it in pores and release it onto surfaces without the need for any external energy.

The research, published in Science Advances, is conducted by an interdisciplinary team including Daeyeon Lee, Russell Pearce and Elizabeth Crimian Heuer Professor in Chemical and Biomolecular Engineering (CBE), Amish Patel, professor in CBE, Baekmin Kim, a postdoctoral scholar in Lee’s lab and first author, and others. Their work describes a material that could open the door to new ways to collect water from the air in arid regions and devices that cool electronics or buildings using the power of evaporation.

“We weren’t even trying to collect water,” says Lee. “We were working on another project testing the combination of hydrophilic nanopores and hydrophobic polymers when R Bharath Venkatesh, a former Ph.D. student in our lab, noticed water droplets appearing on a material we were testing. It didn’t make sense. That’s when we started asking questions.”

Those questions led to an in-depth study of a new type of amphiphilic nanoporous material: one that blends water-loving (hydrophilic) and water-repelling (hydrophobic) components in a unique nanoscale structure. The result is a material that both captures moisture from air and simultaneously pushes that moisture out as droplets.

The researchers first thought that water was simply condensing onto the surface of the material due to an artifact of their experimental setup, such as a temperature gradient in the lab. But the total amount of water collected increased as the film’s thickness increased, proving that the water droplets forming on the surface came from inside the material; even more surprising, the droplets didn’t evaporate quickly, as thermodynamics would predict.

It turns out that they had created a material with just the right balance of water-attracting nanoparticles and water-repelling plastic—polyethylene—to create a nanoparticle film with this special property.

“We accidentally hit the sweet spot,” says Lee. “The droplets are connected to hidden reservoirs in the pores below. These reservoirs are continuously replenished from water vapor in the air, creating a feedback loop made possible by this perfect balance of water-loving and water-repelling materials.”

Beyond the physics-defying behavior, the materials’ simplicity is part of what makes them so promising. Made from common polymers and nanoparticles using scalable fabrication methods, these films could be integrated into passive water harvesting devices for arid regions, surfaces for cooling electronics or smart coatings that respond to ambient humidity.

“We’re still uncovering the mechanisms at play,” says Patel. “But the potential is exciting. We’re learning from biology—how cells and proteins manage water in complex environments—and applying that to design better materials.”

Read more at Penn Engineering Today.