Imagine a world where you simply walk into your home or your office and the phone in your pocket starts charging. This is a world in which electricity is delivered over the air, and it’s done so seamlessly and safely that you never have to use a charging cable again.
This world actually already exists, or at least the technology for it does. A team of researchers has built an entire wireless charging room that can power a lamp, a fan, and a smartphone, no matter where in the room these appliances are located or how they’re oriented.
Detailed in a recent study in Nature Electronics, the technology was tested in a room specifically built for that purpose, but the researchers say it likely could work in retrofitted buildings, too. Of course, this means you’d never have to utter the words “my phone died” ever again. But on a more transformational level, the technology could open new possibilities for powering medical implants, robotics, or even manufacturing facilities.
The secret lies in electromagnetic fields. The prototype room measures 100 square feet and can be found at the University of Tokyo. It consists of a floor, ceiling, and walls made of aluminum sheets. Inside those walls, researchers have hidden a series of capacitors (devices that store electric charge), which generate a magnetic field that reverberates within the room.
The walls are clad in drywall, though any material could work. “Magnetic fields don’t care; they can pass through drywall or wood or whatever material you put on,” says Alanson Sample, a professor of computer science and engineering at the University of Michigan who authored the study along with Takuya Sasatani, a researcher at the University of Tokyo.
Right now, the room can deliver 50 watts of power without exceeding safety guidelines set out by the U.S. Federal Communications Commission and the Institute of Electrical and Electronics Engineers. Sample says that’s enough to charge 10 phones simultaneously, though that level of efficiency is defined by what he calls “battery chemistry,” which varies from model to model. (The experiment was done with an unidentified Chinese smartphone.)
The concept is in its early stages, so there are still a number of challenges to overcome before this goes mainstream. For one, appliances can charge only if they’re equipped with a custom wire coil receiver. For phones, that could take the shape of a simple case. For lamps, it’s a copper ring of sorts that’s looped around a light bulb. These coils act as an “interface” for the magnetic fields. “You have a field that’s swirling and you need a net to catch it, like a butterfly,” Sample says.
Another challenge is ensuring that the energy is evenly distributed throughout the room. Magnetic fields tend to travel in circular patterns, creating dead spots in a square room. To guarantee that the magnetic field reaches every corner—and therefore allows you to charge your device anywhere—capacitors inside the walls actually generate two separate magnetic fields. The first travels in a circle around a conductive copper pole at the center of the room; the other swirls in the corners. A pole in the middle of a room can be very obtrusive, of course, and while it isn’t indispensable to the setup, it helps eliminate dead spots.
Wireless charging technology isn’t entirely new. In 2017, Disney Research designed a similar wireless charging room—leading the research was none other than Sample, then the executive lab director of Disney Research, a network of research labs at the Walt Disney Co. But where Sample’s research goes next largely depends on the funding he receives.
Sample says the technology could work really well in warehouses, which already have structural pillars. They could be retrofitted with a conductive material along with other surfaces in the space. “You see people that spray textures on walls—you could add conductive elements to the spray texture,” he says. By making electricity as ubiquitous as Wi-Fi, the technology could increase mobility when charging electronics and make it easier to power devices anywhere in a large room. It could also facilitate a larger number of devices: “Maybe you have 10,000 little robots and you’re not going to plug them all in,” Sample says.
As long as the room has four walls and a ceiling, the technology could work at any scale, except maybe “Astrodome size,” Sample says with a laugh. And while larger-scale applications make sense, the team is also trying to figure out a way to implement the technology in much smaller spaces, like a toolbox that could charge power tools stored inside it.
Perhaps most important, wireless charging could bring life-changing innovation to the medical field. For example, medical implants like ventricular assist devices—which help pump blood from the heart to the rest of the body—need a cable that is inserted through the skin and connects the heart pump to the control unit and battery pack outside the body. “The problem is that wire leads right to your heart, so it’s a leading cause of infection, and people are hospitalized within a year,” he says. “In that application, wireless medical implants can give someone the freedom to walk around and take a shower again.”
As researchers and engineers, Sample and his team are looking to partner with material scientists to help them work out conductive wall textures. They need drywall manufacturers to figure out how to put conductors in the wall in cost-effective ways, and, of course, they need designers and architects to help integrate the technology (hide or integrate the poles, design better coils for lamps) and bring it all together in a graceful, functional way.
In a world not too far from now, then, will we even need plugs? Sample says wireless technology mostly makes sense for mobile objects, not sturdy appliances like a stove or a fridge that chugs along in the background without you even noticing it. “This allows for electronics to become invisible,” Sample says, “so you can forget about them.”