Scientists have invented a device that can continuously generate electricity from thin air, offering a glimpse of a possible sustainable energy source that can be made of almost any material and runs on the ambient humidity that surrounds all of us, reports a new study.

The novel “air generator,” or Air-gen, is made from materials with holes that are under 100 nanometers in length, which is a scale thousand times smaller than a human hair. This design can pull electricity from water droplets in the air for much longer periods than previous concepts, the researchers report, suggesting that it could eventually provide a continuous and sustainable source of power. Researchers hope the technique could eventually help to fight climate change by serving as an alternative to fossil fuels.

If you’ve ever seen a bolt of lightning streak across the sky, you’ve already had a sneak peek of the untapped power that is hidden in ambient air. This energy is fueled by the electrical charges of water droplets in the air, a phenomenon that has inspired many attempts to harvest humidity by inducing imbalances in charged waters with special devices. Many of these techniques only work for short periods, or require expensive materials, which presents practical challenges for efficiency and scalability.

Now, researchers at the University of Massachusetts, Amherst, have developed an Air-gen device that yields electricity from contact with water droplets that pass through its porous material. In this way, the Air-gen technology creates “a spontaneous and sustained charging gradient for continuous electric output” that “opens a wide door for the broad exploration of sustainable electricity from ambient air,” according to a study published on Wednesday in Advanced Materials.

“One day we may get clean electricity literally anywhere, anytime by using Air-gen technology (i.e., the concept of ‘ubiquitous powering’), because air humidity is 24/7 continuous and everywhere,” Jun Yao, an assistant professor of electrical and computer engineering at UMass Amherst and senior author of the study, said in an email to Motherboard.

“The basis for broad-scale power is that the air contains a huge amount of electricity,” he added. “So if we make Air-gen bigger, we can get larger-volume power—that volume can certainly extend to usage for daily-life functions.”

Yao and his colleagues initially stumbled upon the potential of the Air-gen effect a few years ago during an experiment with biologically synthesized nanowires. After successfully producing electricity from the tiny wires, the team began to explore the possibility of repeating the same technique with a host of other materials.

“The initial discovery was made back in 2020 and was really a serendipitous one—we found that Air-gen made from a specific material called protein nanowires synthesized by a type of bacterium called Geobacter can continuously produce electricity from air humidity,” Yao said.

“But that time, we considered the effect exclusive to this specific material (although we had some initial intuition/indication that the effect may expand to other materials as well),” he continued. “The current work is based on our initial intuition, which then leads to the discovery of this ‘generic’ Air-gen effect working with literally all kinds of materials. So it turns an initially narrow window to a wide-open door for broad potential/impact.”

Indeed, the results revealed that practically any material could become an Air-gen device provided it was perforated with tiny holes measuring 100 nanometers or fewer. At this scale, the holes are big enough to allow water to pass through an upper chamber into a lower chamber, but are small enough that the droplets make contact with the material as they move down through the holes. As a consequence, a charge imbalance is created in the device because the water droplets increase the charge of the upper layer by soaking it as they move into the lower chamber.

The microscale device was able to produce continuous energy equivalent to several hundred millivolts for a test period of a week, which is much longer than other air generator concepts that had a one-time power output that lasted no more than 48 hours. Its material versatility opens up the possibility of scaling the idea up to meet commercial or industrial energy demands.

“A general understanding is that the energy density is low (which can be intuitively understood that the air is very thin), so a single-layer of Air-gen has no way to compete with other power sources (e.g., solar, wind) for matched power volume,” Yao explained. “However, the beauty is that air is diffusive and filled in the entire vertical space, which means that we can stack many layers of air-gen devices in the vertical space to improve power (without taking up additional space footprint).”

“So in principle, Air-gen can be more space efficient” than other power sources, he continued. “Moreover, they can be engineered into varied form factors and neatly blend into the environment (even without one’s notice)” versus the example of “a solar panel that exclusively takes up space.”

It’s wild to imagine a future where homes, factories, and perhaps whole cities might be powered by the electricity that is concealed in the air. For now, the Air-gen concept remains in a developmental phase, though Yao and his colleagues are already working to scale up the concept and optimize the structure of their materials to boost energy efficiency.

“Importantly, since air humidity is ubiquitous and continuous 24/7, Air-gen can be deployed almost anywhere for continuous energy harvesting, transcending the inherent intermittence of existing harvesters restricted to time or location,” the researchers said in the study.

“The sustainable Air-gen technology holds promising prospects” that make it “a possible ‘greener’ energy technology for the future,” they concluded.