-
-
---------------------------- - 2298 - How to Build a Nanotube Radio?
-
- How to build a radio so small you will need an electron microscope in order to see it. Such a radio was first built in 2007 using a carbon nanotube.
-
- Carbon is an element that can have several different forms. The carbon atoms can be bound together in different manners. Called allotropes, carbon can be in a crystal lattice form called a diamond. It can be in a sheet of hexagons in a lattice form called graphite. Or it can be a fullerene, the atoms in their hexagon lattice can bind together in a single sheet to form a sphere, called a buckyball, or a cylinder called a carbon nanotube.
-
- A lead pencil is really graphite. It works because sheets of graphite come off with friction against the paper. If a single sheet of graphite came off, one atom thick it would be called a graphene. A one-atom thick layer of hexagon lattice carbon atoms is a graphene sheet.
-
- If the sheet is rolled into a cylinder it becomes a carbon nanotube. The length of the nanotubes have been made 132,000,000 times longer than their diameter. The diameter being a few nanometers and the length being several millimeters. The one we will use for our radio is 10 nanometers diameter and 500 nanometers long.
-
- A carbon nanotube is the strongest and stiffest material yet discovered due to the covalent bonds between the individual carbon atoms in a locked lattice. A 1 square millimeter cross section carbon tube would hold 14,000 pounds of weight without breaking. This is 312 times stronger than a high-carbon steel cable.
-
- That is a different application for nanotube. The electrical and mechanical applications using nanotube include batteries, racing bicycles, solar cells, ultra-capacitors, touch screens and flexible displays, body armor and fuel cells. But, let’s get back to radio.
-
- The 4 essential elements of a radio are an antenna, a tuner, and amplifier and a demodulator. Add a power source and a loud speaker and you have a radio. All of the 4 essential elements can be accomplished using a single carbon nanotube.
-
- The carbon nanotube is mounted on one electrode and in close proximity to a second electrode. A battery is connected to the two electrodes. This places a dc voltage bias on the nanotube. This part of the radio is placed in a vacuum. Back to the old vacuum tubes in radios. Only, this vacuum tube is the size of a bacterium.
-
- The batteries negative bias puts negatively charged electrons on the tip of the nanotube. Keep in mind the nanotube is only 10 nanometers in diameters and 500 nanometers long. A single atom is 1/10 of a nanometer. The tip of the nanotube can contain about 200 unbalanced electrons.
-
- The electromagnetic waves from an incoming radio transmission impinges upon the nanotube causing the tip to vibrate back and forth across the other electrode. This vibration only occurs at the mechanical resonance frequency of the nanotube.
-
- Like a tuning fork it starts vibrating at a single frequency. The resonance frequency of the nanotube is inversely proportional to the square of its length. Therefore the nanotube length can be set to be tuned to the frequencies of interest. This is the “coarse tuning” step.
-
- The length of the tube can be shortened by increasing the bias current high enough to burn off the tip. Once the proper frequency range is reached the “fine tuning” is accomplished by the electro-static field adjusted by a lower dc bias voltage. The 500 nanometer nanotube in this example can be tuned over the range of 10 to 400 megahertz. This covers the entire FM broadcast band.
-
- Because the tip of the vibrating nanotube has a negative charge and it is vibrating across the electrode it modulates the field-emission current through the nanotube. The battery is powering this field-emission current and therefore provides the amplification needed. The single nanotube has acted as the antenna , the tuner, and the amplifier for the radio .
-
- The current coming off the nanotube varies only with the modulated informational wave. It therefore acts as a diode detector in this way to separate out the carrier wave from the informational wave. Demodulation happens for free. What is left is to send the amplified emission current to a preamplifier to drive a loud speaker and you have a radio.
-
- The radio is so small it requires an electron microscope to see it operate. The mechanical vibrations of the nanotube works for both AM, amplitude-modulated, and FM, frequency modulated, radio signals. The radio will faithfully reproduce either signal. If you wanted to tune over several different bands of frequencies you could have multiple nanotubes at different lengths to cover a broad range.
-
- Now, think of all the things that you could do with a radio that you can not see. A radio so small it could be sent down your blood stream to encounter a tumor and release a chemical or direct other payloads to that site.
-
- What will this do to espionage? What about sending hundreds of radios in for a search and rescue mission? What could you study if you could put a radio inside a single cell? What could be done with brain and muscle implants?
-
- Once inventions get started using nanotube technology the list staggers the imagination. I thought you should know that. Stay tuned , there is a lot more to learn.
-
- March 8, 2019. 1164
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
--------------------- Friday, March 8, 2019 -------------------------
-----------------------------------------------------------------------------------------
No comments:
Post a Comment