The device could capture terahertz waves and convert it to DC current, which could power-up electronic devices. (Image Credit: José-Luis Olivares, MIT)
Physicists at MIT have achieved a new scientific breakthrough that could one day allow household devices to be powered-up by direct current produced from terahertz waves. A terahertz wave, which is emitted by any device that sends out Wi-Fi signals, is an electromagnetic wave with a frequency between microwaves and infrared light. These terahertz waves, or T-Rays, are created by almost anything that registers a temperature, including a human body and inanimate objects in our surroundings. Scientists have created a blueprint for a device that can convert terahertz waves into a direct current. The team published their findings in Science Advances journal.
T-Rays are common in our everyday lives, and if harnessed, they could be used as an alternative source of energy. This could be applied to a cell phone add on that gathers terahertz waves and uses their energy to charge up a mobile device. T-Rays are basically wasted energy since there hasn’t been an effective method to collect and convert them for use.
This technology takes advantage of the atomic behavior of graphene. The team discovered that when graphene is combined with boron nitride, the electrons in graphene skew their motion in the same direction. Incoming terahertz waves should shuttle the electrons in graphene to move through the material in one direction as a direct current. The current can then be used as a form of energy to power electronics.
“We are surrounded by electromagnetic waves in the terahertz range,” says lead author Hiroki Isobe, a postdoc in MIT’s Materials Research Laboratory. “If we can convert that energy into an energy source, we can use for daily life, that would help to address the energy challenges we are facing right now.”
To get the electrons to flow without scattering off irregularities, the team needed to use an extremely clean and impurity-free material. They discovered that graphene was the most suitable material for this project. Scientists who participated in this project made use of research by other scientists that found graphene placed on top of a boron nitride layer skewed electrons in one direction.
The team also discovered that the electrons were guided by incoming terahertz waves in one direction, and the motion produced a DC current if the graphene was pure. If there were too many impurities in graphene, then this would cause the electron clouds to scatter in every direction. It seems obvious, but scientists also noticed that the stronger the incoming terahertz energy, the more energy the device converts to DC power. So they designed a blueprint for a terahertz rectifier that makes use of a small piece of graphene placed on top of a boron nitride layer in the center of an antenna. This could then gather terahertz radiation and increase the signal to transform it into DC power.
Experimental technologies carried out in the past were able to transform terahertz waves to DC current, but they usually required ultracold temperature setups that weren’t very efficient. This new technology could make a positive impact on a global level, mainly because most energy is produced from fossil fuels and depleting natural resources.
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