MIT scientists say that any device that sends out Wi-Fi signals also emits terahertz waves. A terahertz wave, or T-Ray, is an electromagnetic wave with a frequency between microwaves and infrared light. T-Rays are produced by almost anything that registers a temperature, including the human body and objects around us, making them pervasive in daily life. According to the scientists, if these waves were harnessed, the concentrated power could potentially serve as an alternate energy source.
One example the team uses is a smartphone able to passively soak up T-rays and use that energy to charge the phone. Fortunately, so far, this sort of wave is wasted energy as there’s been no practical way to capture the T-ray and turn it into a usable form of energy. Physicists at MIT have come up with a blueprint for a device that they think could potentially lead to a practical way to capture and convert a T-ray into a direct-current.
The design the MIT scientists came up with takes advantage of the quantum mechanical behavior of a substance called graphene. When graphene is combined with another material, in this instance boron nitride, the electrons in the graphene skew their motion towards a common direction. Any incoming terahertz waves should “shuttle” the electrons in graphene to flow through the material in a single direction as a direct-current.
The researchers needed a material that was very clean and free of impurities to get the electrons of the material to flow through without scattering off irregularities in the material. They found that graphene was the ideal starting material for the project. Scientists in this research will draw on research by other scientists that had discovered graphene placed atop a layer boron nitride skewed electrons in one direction.
While researching that combination of material, the team found that the electrons are different by incoming terahertz waves in one direction and that that skew motion generated a DC current. The team also found the stronger the incoming terahertz energy, the more energy device that will convert to DC power. The team came up with a blueprint for a terahertz rectifier that uses a small square of graphene sitting atop a layer boron nitride sandwich within an antenna that could collect and concentrate ambient terahertz radiation and boost the signal left enough to convert it into DC power.