Nanotechnology

Nanopores are the secret to making electricity out of thin air

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May 24, 2023

(Nanowerk News) A team of engineers at the University of Massachusetts Amherst recently demonstrated that almost any material can be turned into a device that continuously harvests electricity from moisture in the air. The secret lies in the ability to flavor materials with nanopores less than 100 nanometers in diameter. The research appears in the journal Advanced Materials (“Generic Effects of Air-gen in Nanoporous Materials for Sustainable Energy Harvesting from Moisture Air”).

“This is very exciting,” said Xiaomeng Liu, a graduate student in electrical and computer engineering at the UMass Amherst School of Engineering and lead author of the paper. “We opened the door wide to harvesting clean electricity out of thin air.” An illustration shows a nanopore harvesting electricity from moisture An illustration shows a nanopore harvesting electricity from moisture. (Image: Derek Lovley, Studio Ella Maru)

“Air contains a tremendous amount of electricity,” said Jun Yao, assistant professor of electrical and computer engineering in the College of Engineering at UMass Amherst, and senior author of the paper. “Imagine a cloud, which is nothing more than a mass of water droplets. Each of those droplets carries a charge, and when conditions are right, clouds can generate lightning strikes—but we don’t know how to reliably capture electricity from lightning. What we have done is created a small man-made cloud that generates electricity for us in a predictable and continuous manner so that we can harvest it.”

The core of man-made clouds relies on what Yao and his colleagues call the “Generic Air-gene effect”, and it builds on the work previously completed by Yao and co-author Derek Lovley, Distinguished Professor of Microbiology at UMass Amherst. in 2020 demonstrated that electricity can be continuously harvested from the air using a special material made of protein nanowires grown from the bacterium Geobacter sulfurreducens.

“What we realized after making the discovery of Geobacter,” says Yao, “is that the ability to generate electricity from the air—which we later called the ‘Air-gene effect’—is surprisingly general: literally any type of material can harvest electricity from the air, provided it has certain properties.

That property? “It should have a hole smaller than 100 nanometers (nm), or less than one-thousandth the width of a human hair.”

This is due to a parameter known as the “mean free path”, the distance that a single molecule of a substance, in this case water in air, travels before colliding with another single molecule of the same substance. When water molecules are suspended in air, their average free path is about 100 nm.

Yao and his colleagues realized they could design a power harvester based on these numbers. This harvester will be made of a thin layer of material filled with nanopores smaller than 100 nm which allow water molecules to flow from the top to the bottom of the material. But because each pore is very small, water molecules will easily bump into the edges of the pore as they pass through the thin layer. This means that the top of the layer will be bombarded with more charge-carrying water molecules than the bottom, creating a charge imbalance, like in a cloud, because the top increases its charge relative to the bottom. This would effectively create a battery — a battery that runs as long as there is moisture in the air.

“The idea is simple,” said Yao, “but it has never been invented before, and it opens up all kinds of possibilities.” Harvesters can be designed from all types of materials, offering a broad choice for cost-effective and environmentally adaptable fabrications. “You can imagine harvesters being made of one type of material for a rainforest environment, and another for more arid areas.”

And because moisture is always present, the harvester will operate 24/7, rain or shine, at night and whether the wind blows or not, which solves one of the major problems of technology like wind or sun, which only work under certain conditions. .

Finally, because air moisture diffuses in three-dimensional space and the thickness of the Air-gen device is only a fraction of the width of a human hair, thousands of them can be stacked on top of one another, efficiently increasing their number. energy without increasing the footprint of the device. Such an Air-gen device would be capable of providing kilowatt-level power for general electric utility use.

“Imagine a future world where clean electricity is available wherever you go,” said Yao. “The general effect of Air-gen means that this future world can become a reality.”



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