This may look like spidery art on a playing card, but it’s actually a tiny array of antennas and a lens. The device can grab waves of 5G energy from the air, focus them, and then turn those waves into electricity.

A few years ago, Aline Eid was sitting in a restaurant sharing popcorn with Jimmy Hester. They weren’t just snacking, though. They were puzzling over a tough problem. How could they tap into the power of invisible signals that send data to cell phones, computers and other devices? If they could manage this, people might someday run their electronics without batteries or cords. As they brainstormed, an idea took shape. That idea has now become a reality.

The heart of their innovation is a special gadget. It helps gather wireless signals sent out by cell-phone towers. Called a Rotman lens, the device looks a bit like a flat metal spider. “We were so excited. I knew it was going to work,” recalls Eid. She’s a PhD student in electrical engineering at the Georgia Institute of Technology in Atlanta.

Hester is the cofounder of the tech company Atheraxon. It’s also in Atlanta. He and Eid shared the idea with their professor, Manos M. Tentzeris. “That was a breakthrough solution,” Tentzeris says. The three described their new device January 12 in Scientific Reports.

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The harvesting of wireless energy doesn’t work well over long distances. It’s a problem that electrical engineer Hina Tabassum also knows well. At York University in Toronto, Canada, she works on this problem, too.

Radio waves and microwaves carry data from cell-phone towers to our phones and other devices. The area each tower covers is called a cell. Your cell phone contacts the nearest tower to exchange data. The first cellular networks used radio waves to send and receive data. Newer 5G networks now use higher frequency microwaves. These waves can carry more data and transmit it faster. While that can help save energy, these waves don’t reach as far. That’s because buildings and other objects block them. Moisture in the atmosphere absorbs them, too, reducing their strength the farther they travel.

When waves of energy wash over a phone or other device, they drop off data and then continue on their way. The energy that had been used to carry those data has no use now. It’s a waste, says Tentzeris — unless the new device transforms it into electricity.

This energy tapping is possible across the electromagnetic spectrum. But “you cannot get a lot of power out of low frequencies,” says Eid. Millimeter-range 5G is exciting because cell towers use much more energy to blast out these high frequencies. So a harvesting antenna could get more electricity out of these signals.

A typical 5G tower sends microwave signals out some 180 meters (590 feet). To gather their energy from the edge of this distance, a receiving antenna must point in the exact same direction from which the waves are coming. Yet to be practical, Eid notes, a 5G-energy harvester should work from anywhere within a 5G cell and no matter which way the receiver is pointing. Eid and Hester had been pondering how to harvest energy from such distance and from lots of different directions.

They solved the problem with that Rotman lens. These have been around for a long time. But engineers had only used them to send signals, not to receive them. Says Tabassum, using them as a receiver is “a new technology, for sure.”

The lens looks a bit like a flattened metal tarantula. Spidery “legs” extend from two sides of a central body. On one side, these legs lead to eight small antennas. On the other side, they lead to six beam ports. The antennas catch microwaves and focus them onto a single point at one of those beam ports — whichever one lines up best with the direction of the incoming waves. Another part in the device transforms the microwaves it receives into electrical power.

The six beam ports are like six of the eight eyes on a real tarantula’s head. With them, Eid says, “our system can also look in six different directions.”

The researchers tested their device in the lab across a distance of 2.8 meters (9 feet). They weren’t able to test it at the same high energies a 5G tower would use. But they gathered enough information to simulate how the device should work in the real world. At 180 meters, they now report, this device could deliver six microwatts of power.

Tabassum worries that this estimate might be too high. Her main concern is that things such as buildings, trees and people would block signals, limiting how much of this energy reaches a device.

Tentzeris says his team accounted for that. The Georgia Tech team is now planning to test the device at even longer distances.

Six microwatts is not much power. Charging the typical battery for one of today’s cell phones needs around 6 million microwatts (6 watts) of power. Still, the new invention would have enough power to run most sensors and microchips.

As the Internet of Things is emerging, sensors and microchips are spreading everywhere. Low-power electronics can measure air or soil quality. They can keep tabs on safety aspects of bridges or buildings. They can manage the heat or lighting in a home and even track someone’s health. But the batteries that power these electronics contain heavy metals that aren’t easy to make or to dispose of safely. Finding a way to power the Internet of Things without batteries would be good for the environment, says Eid.

Her team figured out how to make its new device at low cost, mainly by using an inkjet printer. They hope to start marketing it as a product within the next few years.

Will they name it “The Tarantula”? Probably not. But Eid does say it has one more thing in common with spiders. “A tarantula can climb anywhere,” says Eid. The device is lightweight and bendable. You can put it anywhere you want, like a sticker — a very special playing-card-sized sticker that grabs energy from the air!

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

5G: The 5 gigahertz frequency band used to transmit a newer generation of cellular (phone) network signals.

antenna: (in physics) Devices for picking up (receiving) electromagnetic energy.

cell: (in telecommunications) A technology that relies on a large number of base stations to relay signals. Each base station covers only a small area, which is known as a cell. Phones that rely on this system are typically referred to as cell phones.

component: Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).

data: Facts and/or statistics collected together for analysis but not necessarily organized in a way that gives them meaning. For digital information (the type stored by computers), those data typically are numbers stored in a binary code, portrayed as strings of zeros and ones.

electrical engineer: An engineer who designs, builds or analyzes electrical equipment.

electricity: A flow of charge, usually from the movement of negatively charged particles, called electrons.

electronics: Devices that are powered by electricity but whose properties are controlled by the semiconductors or other circuitry that channel or gate the movement of electric charges.

engineer: A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need. (v.) To perform these tasks, or the name for a person who performs such tasks.

engineering: The field of research that uses math and science to solve practical problems.

environment: The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

information: (as opposed to data) Facts provided or trends learned about something or someone, often as a result of studying data.

internet: An electronic communications network. It allows computers anywhere in the world to link into other networks to find information, download files and share data (including pictures).

Internet of Things: The network of physical objects that have been equipped with electronic devices to let them gather and share information. This allows these objects to observe and interact with their environment.

lens: (in physics) A transparent material that can either focus or spread out parallel rays of light as they pass through it. (in optics) A curved piece of transparent material (such as glass) that bends incoming light in such a way as to focus it at a particular point in space.

marketing: The strategy for getting people to adopt a new policy or buy new products. In many cases, the marketing may rely on advertising or getting celebrities and other trendsetters to endorse a policy or product.

matter: Something that occupies space and has mass. Anything on Earth with matter will have a property described as "weight."

metal: Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure). 

microchip: A tiny wafer of semiconducting material (the chip), often silicon, which holds tiny electronic parts and the "wiring" needed to connect them to an electric circuit. Or a small computer chip that is implanted in goods or animals and acts like a tag. It holds information that can be retrieved as needed (such as an animal's name or the inventory lot for commercial products.

microwaves: An electromagnetic wave with a wavelength shorter than that of normal radio waves but longer than those of infrared radiation (heat) and of visible light.

PhD: (also known as a doctorate) A type of advanced degree offered by universities — typically after five or six years of study — for work that creates new knowledge. People qualify to begin this type of graduate study only after having first completed a college degree (a program that typically takes four years of study).

sensor: A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.

simulation: (v. simulate) An analysis, often made using a computer, of some conditions, functions or appearance of a physical system. A computer program would do this by using mathematical operations that can describe the system and how it might change over time or in response to different anticipated situations.

spectrum: (plural: spectra) A range of related things that appear in some order. (in light and energy) The range of electromagnetic radiation types; they span from gamma rays to X rays, ultraviolet light, visible light, infrared energy, microwaves and radio waves.

spider: A type of arthropod with four pairs of legs that usually spin threads of silk that they can use to create webs or other structures.

tarantula: A hairy spider, some of which grow large enough to catch small lizards, frogs and birds.

technology: The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.

watt: A measure of the rate of energy use, flux (or flow) or production. It is equivalent to one joule per second. It describes the rate of energy converted from one form to another — or moved — per unit of time. For instance, a kilowatt is 1,000 watts, and household energy use is typically measured and quantified in terms of kilowatt-hours, or the number of kilowatts used per hour.

wave: A disturbance or variation that travels through space and matter in a regular, oscillating fashion.

wireless: (in telecommunications) An adjective that describes the ability of certain devices to send and receive radio signals over the air. It often refers to Wi-Fi networks and the networks operated by cell-phone companies to transmit data called up by phone users.

Journal: A. Eid et al. 5G as a wireless power grid. Scientific Reports. Vol. 11, January 12, 2021, article 636. doi: 10.1038/s41598-020-79500-x.

Kathryn Hulick is a freelance science writer and the author of Strange But True: 10 of the World's Greatest Mysteries Explained, a book about the science of ghosts, aliens and more. She loves hiking, gardening and robots.

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