Now the Wasted Energy Will Charge Your Mobile Phones and Laptops – A Sustainable Approach for Future Prosperity:
The physicists at MIT
(Massachusetts Institute of Technology) came up with a potential alternative
energy source for charging household electronic gadgets with the help of T (Terahertz)
waves. T waves are electromagnetic waves with high frequency produced by human
bodies, WI-FI signals and all other inanimate object around us. These rays were
earlier considered to be a waste of energy as there was no way to capture and
convert them for charging purposes.
The researchers at MIT
initiated a visionary plan to convert these T waves into a form of electricity for
powering household electronics. Graphene an allotrope of carbon was mixed with
Boron Nitride, to understand the atomic behavior. The incoming T waves scatter
the electrons inside the graphene, skewing their motion in a single direction,
as a direct current (DC). The researchers have published their practical
observation in the journal Science
Advances and have teamed up with the experimentalists to turn this into a
physical device.
Hiroki Isobe, a leading
author and a postdoc in MIT’s Materials Research Laboratory states that “We are
surrounded by electromagnetic waves in the terahertz range. 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”. His research works was
collaborated along with various assistant professors of physics at MIT and a
chemistry postdoc of Harvard University.
Over the last few years
energy harvesting designs were a major concern for scientists. To convert T
waves into DC current was only possible at very cold temperature, which is
indeed of no use in the practical world. Moreover the rectifiers which are
responsible for the conversion into DC, only work up to a certain frequency and
wasn’t able to accommodate T wave range. Hence a remedy for this problem was
considerably needed.
Isobe argued with
evidences that at quantum mechanical level, a materials own electrons could be
induced to flow in one direction, in order to steer incoming T waves into DC
current. He found graphene as a perfect antidote for this theory. He mentions
that the material must be clean and impure-free in order to move the electrons
without scattering off irregularities in the material. Physicists had to carry
out a process called “inversion” where they would have to break the materials
inherent symmetry. With this observations Isobe developed a systematic approach
to induce an asymmetric flow of electrons in response to incoming waves.
Graphene was placed
over the top layer of Boron Nitride, resulting in molecular action of boron and
nitrogen. The forces between graphene electrons were displaced from their
balance and it was noted that the electrons were in close proximity towards
boron rather than nitrogen. Hence this process was called “skew scattering”, in
which the cloud of electrons skew in one direction.
Isobe recorded the fact
that too many impurities in graphene will act as obstacles in the path of
electron cloud, leading to scattering of electrons in multiple directions. He
explains “With many impurities, this skewed motion just ends up oscillating,
and any incoming terahertz energy is lost through oscillation. So we want a
clean sample to effectively get a skewed motion”.
Hence they came up with
a blue print device called “Terahertz Rectifier” which consists of a small
square of graphene embedded on the top layer of the Boron Nitride sandwiched
with an antenna. The antenna would aid in boosting and collecting terahertz
radiation needed for conversion into DC current.
Liang Fu, one of the
co-authors of Isobe’s work condemns that “This would work very much like solar
cell, except for a different frequency range, to passively and convert ambient
energy”. The team has also filed a patent for the new “high-frequency
rectification” design and are working along with other experimentalists of MIT
to develop a physical device, which works at room temperature. He also added “We
are taking a quantum material with some symmetry at the atomic scale, that can
now be utilized, which opens up a lot of possibilities.”
Isobe also added that
“If a device works at room temperature, we can use it for many portable
applications”. The terahertz rectifiers have many other great applications such
as wireless power implantation in patient’s body, charging mobile phones,
laptops and all other household electronic gadgets. This research was funded
collaboratively by the U.S. Army Research Laboratory and the U.S. Army Research
Office through the Institute for Soldier Nanotechnologies (ISN).
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