“What we have invented, you can imagine it’s like a small-scale, man-made cloud,” said Jun Yao, a professor of engineering at the University of Massachusetts at Amherst and the senior author of the study. “This is really a very easily accessible, enormous source of continuous clean electricity. Imagine having clean electricity available wherever you go.”

That could include a forest, while hiking on a mountain, in a desert, in a rural village or on the road.

The air-powered generator, known as an “Air-gen,” would offer continuous clean electricity since it uses the energy from humidity, which is always present, rather than depending on the sun or wind. Unlike solar panels or wind turbines, which need specific environments to thrive, Air-gens could conceivably go anywhere, Yao said.

Less humidity, though, would mean less energy could be harvested, he added. Winters, with dryer air, would produce less energy than summers.

The device, the size of a fingernail and thinner than a single hair, is dotted with tiny holes known as nanopores. The holes have a diameter smaller than 100 nanometers, or less than a thousandth of the width of a strand of human hair.

The tiny holes allow the water in the air to pass through in a way that would create a charge imbalance in the upper and lower parts of the device, effectively creating a battery that runs continuously.

“We are opening up a wide door for harvesting clean electricity from thin air,” Xiaomeng Liu, another author and a UMass engineering graduate student, said in a statement.

While one prototype only produces a small amount of energy — almost enough to power a dot of light on a big screen — because of its size, Yao said Air-gens can be stacked on top of each other, potentially with spaces of air in between. Storing the electricity is a separate issue, he added.

Yao estimated that roughly 1 billion Air-gens, stacked to be roughly the size of a refrigerator, could produce a kilowatt and partly power a home in ideal conditions. The team hopes to lower both the number of devices needed and the space they take up by making the tool more efficient. Doing that could be a challenge.

The scientists first must work out which material would be most efficient to use in different climates. Eventually, Yao said he hopes to develop a strategy to make the device bigger without blocking the humidity that can be captured. He also wants to figure out how to stack the devices on top of each other effectively and how to engineer the Air-gen so the same size device captures more energy.

It’s not clear how long that will take.

“Once we optimize this, you can put it anywhere,” Yao said.

It could be embedded in wall paint in a home, made at a larger scale in unused space in a city or littered throughout an office’s hard-to-get-to spaces. And because it can use nearly any material, it could extract less from the environment than other renewable forms of energy.

“The entire earth is covered with a thick layer of humidity,” Yao said. “It’s an enormous source of clean energy. This is just the beginning in making use of that.”