How to charge your cell phone via WiFi?

The launch of a smart phone self-charging phone case in the market has won everyone’s attention. Before this product was released in the market, usually the mobile phone had to be charged beforehand and used. The same method is often seen today. Otherwise, the method of obtaining direct current from solar energy through solar panels is used.

But considering the second version to be released now, it can be inferred that a different method can be reached beyond the commonly used methods mentioned above. Imagine: a smart phone case that can absorb the energy released by a WiFi router. Because WiFi emitting devices such as routers produce Tetrahertz waves or T rays, it is theoretically possible to use those electromagnetic waves to create the energy needed to charge your cell phone.

A research group at the Massachusetts Institute of Technology has discovered a method that can change the behavior of graphene and thereby obtain a direct energy current. This method is ideal for a passive charger that only needs to be placed near a router. Their findings were published in the journal “Science Advances”.

“We are surrounded by electromagnetic waves in the terahertz range,” said lead author Hiroki Isobe, a postdoctoral researcher at MIT’s Materials Research Laboratory. “If we can convert that energy into a source of energy that can be used in everyday life, it will help us to face the energy challenges we are facing now,” he added.

From alternating current to simple current

Scientists have a long history of trying to make more practical use of environmental energy. Non-use is a huge waste of renewable energy. Light energy from the sun, which can be collected and converted into electrical energy through solar panels, is the most obvious renewable energy currently available.

To control non-conventional energy sources, researchers usually use rectifiers, or devices designed to convert alternating current into direct current of oscillating electromagnetic waves in all directions. Basically, it ensures that current flows in machines in one direction only.

Rectifiers typically convert low-frequency electromagnetic waves, such as radio waves, through an electrical circuit equipped with diodes or semiconductor devices that allow current to flow in only one direction. This generates an electric field that carries waves through the circuit as a direct current. But since rectifiers are stable only up to a limited frequency, they cannot respond to waves in the tetrahertz range.

Quality direct current to charge the phone

To convert transparent T-ray energy into something more predictable and usable, Isobe and his fellow researchers envisioned interacting with a material’s atomic structure to force electrons to flow in one direction instead of relying on rectifiers to create a direct current. Is it possible? Their focus is on the atomic behavior of graphene, a material widely used in electronics, solar panels and asphalt.

Graphene is intrinsically symmetric under normal conditions. It means that the electrons feel the same force among themselves and that force scatters the electrons equally in all directions. Isobe and his team began looking for ways to make this scattering asymmetric.

The scientists discovered that graphene was combined with another material, boron nitride. This forces the graphene electrons to move in a common direction. That means the incoming terahertz waves combine the graphene electrons into a direct current in one direction. This overall effect is called “skew scattering”.

However, there is a special point that should be paid attention to. That is, since graphene is made of a single layer of carbon atoms, there is a risk of losing some of its properties, such as conductivity, if there are too many impurities in it. Impurities can act as shields in electron clouds, allowing electrons to scatter.

“By having too many impurities, this induced motion ends up oscillating, and any incoming terahertz energy is lost through this oscillation,” Isobe said. “So we want to use a pure sample and get an effective induced motion.” Isobe added.

Terahertz Rectifier

With this discovery, Isobe and company created a blueprint for a terahertz rectifier. They have applied for a patent for what they call a “high frequency rectification” device.

Imagine an antenna that collects and concentrates terahertz radiation from the environment. The researchers found that the stronger the terahertz energy, the better the device can convert it into simple current. Inside the antenna, a small amount of graphene is embedded on a layer of boron nitride.

“This would work like a solar cell, except using a different frequency range to passively collect and convert ambient energy,” says Lian Fu, assistant professor of physics at MIT.

The team is currently working with experimental physicists at MIT to come up with a physical prototype. It is designed to work at room temperature. Isobe believes that terahertz rectifiers could soon be used to supercharge energy in the human body.

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