The magic room where the smartphone recharges itself

How many times do we happen to find ourselves with the smartphone unloaded right on the most beautiful stage? It will have happened to anyone wandering around a restaurant with the magazine in hand, desperately looking for a hold. And if one day, however, there will be no more need for all this? In reality, researchers from the University of Michigan have already thought of it and, in collaboration with the University of Tokyo , have created something truly sensational. For their research, published in Nature Electronics, the scientists built a room for wireless charging of electronic devices.

Wireless charging based on electromagnetic induction

Wireless charging is certainly not a new practice. Indeed, lately there are more and more smartphones equipped with this function. The devices we know, however, are based on induction charging. This system creates a magnetic field inside a coil present in the device. This, in turn, generates a movement of electrons which gives rise to the current. In the case of wireless induction charging, however, the magnetic field is necessarily created thanks to the contact between the charging plate and the device. The University of Tokyo researchers, on the other hand, is a wireless charging system that requires no direct contact between the device and the power source . In other words, they have created a room that allows wireless charging to all the electronic devices inside it.

The room for wireless charging of electronic devices built by researchers from the University of Michigan, in collaboration with the University of Tokyo. Credits: "Michigan News" and The University of Tokyo.
The wireless charging room built by the researchers is located at the University of Tokyo. Credits: “Michigan News” and The University of Tokyo.

The room for wireless charging of electronic devices

Unlike other wireless systems based on microwaves, or on the Beamforming technique , this “magic” room uses an innovative system to generate a magnetic field. The room, 9 square meters in area and 2 meters high , is made entirely of metal: walls, ceiling and floor are huge conductive surfaces. An electromagnetic coil (remember the solenoid of the physics exercises?) Is powered by an alternating current generator with a frequency of 1.34 MHz. In this way, the coil generates a magnetic field that propagates throughout the room, and in the walls . This causes an electric current to circulate along all surfaces of the room, which in turn is responsible for generating another magnetic field.

A magnetic field induced to generate electricity

It is this new magnetic field (called "induced") that makes the environment suitable for wireless charging. To further improve the conductive performance of the room we think of the capacitors positioned inside some cavities of the walls. In this way, unlike other similar wireless power systems, the volume of space traversed by the magnetic field increases, along with the transmitted power. Not only that, the devices can be located in any corner of the room and suffer from wireless charging without problems. All this is not trivial.

Room for wireless charging of electronic devices. Capacitors used inside the cavities of the walls in the "magic" room. Credits: "Michigan News" and The University of Tokyo.
Capacitors used inside the cavities of the walls in the “magic” room. Credits: “Michigan News” and The University of Tokyo.

Two 3D magnetic fields to reach every corner of the room and allow devices to wirelessly charge

Magnetic fields, in fact, tend to arrange themselves on circular lines and this creates uncovered regions (such as, for example, angles). To solve this problem, two separate magnetic fields are generated in this room: the first that starts from the center and the second that propagates between the adjacent walls. This eliminates all dead spots and a device can potentially be anywhere. To receive electricity, the devices in the room need another (receiving) coil to intercept the magnetic field and allow wireless charging . In this way, by exploiting some simple electromagnetic properties, it is possible to supply energy to any electronic device, without the need for cable connections.

Room for wireless charging of electronic devices. LED lamp powered by the receiving coil thanks to the magnetic field generated inside the room. Credits: "Michigan News" and The University of Tokyo.
LED lamp powered by the receiving coil thanks to the magnetic field generated inside the room. Credits: “Michigan News” and The University of Tokyo.

All good, but does it work?

During the tests, the researchers managed to transfer at least 50 Watts of power with an efficiency of 98% . They are also convinced that this technology can be implemented without problems during the construction of new buildings, even if the road is still long. Researchers at the University of Michigan are working on building a building on campus, which they will use to continue their experiments.

The future of electromagnetic induction wireless charging speaks 3D

This system represents the future of wireless charging, overcoming all the limitations of both cable and induction charging techniques . The first, so-called "one-dimensional", refer to those we use every day and require a direct connection between device and charger. Induction charging techniques, also called "two-dimensional" are wireless but still require direct contact between the charging surface and the device. Thanks to wireless charging based on the propagation of a magnetic field throughout the environment, however, the devices can be recharged anywhere in the room.

Harmful? No, useful for improving health

Using anatomical mannequins, the scientists also observed that the limits imposed by the guidelines of the US Federal Communications Commission are not exceeded. This means that the magnetic field generated inside the room is not harmful to humans . Indeed, this technology can even be useful for supplying energy to pacemakers or any other artificial implant used by patients with pathologies . Still, other applications may involve warehouses where mobile robots feed themselves as they perform their duties. In short, Nikola Tesla's dream of wanting to create an electromagnetic wave that travels around the world in the ionosphere, could soon become reality.

The article The magic room where the smartphone charges itself comes from Tech CuE | Close-up Engineering .