A nanoradio (also called carbon nanotube radio) is a nanotechnology acting as a radio transmitter and receiver by using
carbon nanotubes. One of the first nanoradios was constructed in 2007 by researchers under
Alex Zettl
Alex Zettl is an American professor of experimental condensed-matter physics. His research involving the properties of novel materials has produced significant advances in the field.
Biography
Zettl received a B.A. degree from the University of ...
at the
University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
where they successfully transmitted an audio signal.
Due to the small size, nanoradios can have several possible applications such as radio function in the bloodstream.
History
The first observation of a nanoradio can be accredited to a Japanese physicist
Sumio Iijima
is a Japanese physicist and inventor, often cited as the inventor of carbon nanotubes. Although carbon nanotubes had been observed prior to his "invention", Iijima's 1991 paper generated unprecedented interest in the carbon nanostructures and ...
in 1991 who saw a "a luminous discharge of electricity" coming from a carbon nanotube on a graphite electrode.
On October 31, 2007, a team of researchers under Alex Zettl at the University of California, Berkeley created one of the first nanoradios.
Their experiment consisted of placing a multilayered nanotube placed on a silicon electrode and connecting it to a counter electrode through a wire and a DC battery. Both the electrode and nanotube were also put in a vacuum of about 10
−7 Torr
The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly of a standard atmosphere (). Thus one torr is exactly (≈ ).
Historically, one torr was intended to be the same as one " millimeter of merc ...
.
They then placed the apparatus into a
high-resolution transmission electron microscope to document the movement of the nanotube. They observed the nanoradio vibrating and transmitted a song called "Layla" by Eric Clapton. After some minor adjustments, the team was able to transmit and receive signals from a couple meters across the laboratory;
however, the initial audio receptions from the radio were scratchy which Zettl believed was due to the lack of a better vacuum.
Properties
The small size, roughly 10 nanometers wide and hundreds of nanometers long, and composition of nanoradios provide several distinct properties. The small size of nanoradios enables electrons to pass through without much friction, making nanoradios efficient conductors. Nanoradios can also come in different sizes; they can be double-walled, tripled-walled and multi-walled. Aside from the different sizes, nanoradios can also take different shapes such as bent, straight or
toroid
In mathematics, a toroid is a surface of revolution with a hole in the middle. The axis of revolution passes through the hole and so does not intersect the surface. For example, when a rectangle is rotated around an axis parallel to one of its ...
al. Common among all nanoradios is how relatively strong they are. The resistance can be attributed to the strength of the bonds between carbon atoms.
Function
The fundamental parts of a radio are the antenna, tuner, demodulator and amplifier. Carbon nanotubes are special in that they can function as these parts without the need of extra circuitry.
Antenna
The nanoradio is small enough for electromagnetic signals to mechanically vibrate the nanoradio. The nanoradio essentially acts as an antenna by vibrating with the same frequency as the signal from incoming electromagnetic waves; this is in contrast with traditional radio antennas, which are generally stationary.
The nanotube can vibrate in high frequencies, from "thousands to millions of times per second."
Tuner
The nanoradio can also function as a tuner by extending or reducing the length of the nanotube; doing so changes the resonance frequency at which it vibrates, enabling the radio to tune into specific frequencies. The length of the nanotube can be extended by pulling the tip with a positive electrode and can be shortened by removing atoms off the tip.
Consequently, changing the length is permanent and can't be reversed; however, the method of varying the electric field can also affect the frequency that the nanoradio responds without being permanent.
Amplifier
As a benefit of the microscopic size and needle-like shape, the nanoradio functions naturally as an
amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
. The nanoradio exhibits
field emission
Field electron emission, also known as field emission (FE) and electron field emission, is emission of electrons induced by an electrostatic field. The most common context is field emission from a solid surface into a vacuum. However, field emissio ...
, in which a small voltage emits a flow of electrons; due to this, a small electromagnetic wave would produce a large flow of electrons, amplifying the signal.
Demodulator
Demodulation is essentially the separation of the information signal from the carrier wave. When the nanoradio vibrates in sync with the carrier wave, the nanoradio responds only to the information signal and ignores the
carrier wave
In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has ...
; and so, the nanoradio can act as a demodulator without the need of circuitry.
Medical Application
Currently, chemotherapy uses chemicals that harm not only cancerous cells, but also healthy ones since they are put into the blood stream. Nanoradios can be used to prevent damage to healthy cells by remotely communicating with the radio to release drugs and specifically target cancerous cells. Nanoradios can also be injected into individual cells to release certain chemicals, enabling repair of specific cells.
Nanoradios can also be used to monitor insulin levels of diabetes patients and use that information to release a drug or chemical.
Complications
The implanting of nanoradios in the body are currently not feasible due to power dissipation. The nanoradio radiates about 4.5 x 10
−27 W of electromagnetic power; however, much of this power would be lost when passing through the body. The amount of energy input can be increased, but would generate too much heat in the body, posing a safety risk. Other issues include the difficulty of constructing a nanoradio due to its nanoscale size, requiring quantum models and precision to manufacture.
References
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Nanoelectronics
Radio technology
Radio electronics