Nanotechnology and Carbon Nanotube

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The world-renowned science fiction series ‘Star Trek’ mentions a device called the Replicator, which is capable of producing any type of physical object—be it a cup of steaming tea or any kind of weapon. Although we tend to think that such a machine is impossible to create, some people are starting to believe that it may not be so far-fetched after all. Thanks to a technology called ‘Nanotechnology’, humans are now dreaming of turning science fiction into reality. For the past several years, research and discoveries in this field have been stirring excitement among scientists at various levels. This excitement has now spread to the general public as well.

What is Nanotechnology? To learn about this, we must first understand the meaning of the word ‘nano’. ‘Nano’ is an extremely small unit of measurement. One nanometer is one part of 1,000,000,000 (one hundred crore) of a meter, which is even smaller than the wavelength of visible light. For perspective, the width of a human hair is about 50,000 nanometers. This gives a rough idea of just how tiny a nanometer is! Generally speaking, nanotechnology refers to technology that deals with things measured in nanometers, but it is not so simply defined. While there is some debate in the scientific community about what size range falls under this technology, typically anything from 1 to 100 nanometers is considered part of it. In 1986, Dr. K. Eric Drexler first coined the term ‘Nanotechnology’.

Now, the question is—which branch of science does ‘Nanotechnology’ belong to? The interesting thing is that it cannot be assigned to any one particular field. Biologists, physicists, chemists, technologists—all are connected to this technology. No single group holds sole dominance in this world. However, it is quite challenging for one person to gain deep knowledge in all these areas. Still, Nobel laureate Dr. Horst Störmer has expressed optimism, suggesting that a common language will emerge among the various disciplines involved in nanotechnology, so that any experienced researcher, even without deep expertise in every field, could continue researching in this area simply by knowing that language.

            One of the difficulties in researching this technology is that the normal laws of mechanics do not always apply. Let’s consider a simple example—imagine placing a straw or glass tube in a glass of water. You will see that the water level inside and outside the tube is almost the same, as expected. But if you now dip a much narrower tube, you will see that the water level rises inside the tube, higher than outside. The narrower the tube, the higher the water climbs. In other words, the smaller the diameter, the more the normal behavior is disrupted. At the nanoscale, the failure of mechanical laws is even more pronounced. The characteristics of nano-objects cannot be explained by Classical Mechanics alone, so a new type of mechanics is needed. Fortunately, quantum mechanics emerged a few decades before research into nanotechnology began, which can explain the properties of nanoscale materials. This remarkable branch of mechanics is called quantum mechanics.

We cannot cross over to the other side of a wall without climbing it. But in the world of the nanoscale, an electron can cross barriers and reach the other side without gaining enough energy. This seemingly impossible phenomenon can only be explained by quantum mechanics. In quantum mechanics, this process is called Tunneling. Countless such phenomena are observed in the nanoscale world. In essence, to understand nanotechnology, we must let go of our old knowledge and start anew.

            Recently, scientists are focusing their attention and research continuously on two groundbreaking discoveries in nanotechnology. These two are nanowires and carbon nanotubes. A nanowire is an extremely thin, narrow wire (sometimes even 1 nanometer in diameter). Scientists hope to use these wires to create exceptionally small transistors for computers and other electronics. In recent years, the discovery of carbon nanotubes has outshone nanowires, dominating the field with their extraordinary properties. Although we know very little about carbon nanotubes so far, what we have discovered is enough to astonish us.

            So, what are carbon nanotubes? Carbon nanotubes are graphene sheets rolled into a cylindrical shape. Graphene is a sheet made from carbon atoms with a thickness of just one atom, where the carbon atoms are linked to form a hexagonal pattern. The properties of these tubes change depending on how the graphene sheet is rolled. In 1991, Dr. Sumio Iijima discovered carbon nanotubes. There are two types: SWNT – Single-walled Nanotubes (consisting of a single graphene layer) and MWNT – Multi-walled Nanotubes (consisting of multiple graphene layers). The diameter ranges from 1 nanometer (for SWNTs) to 50 nanometers (for MWNTs), and their length can exceed 1 millimeter. Inside MWNTs, the gap between each layer is about 0.34 to 0.36 nanometers.

Carbon nanotubes possess some unique properties that have aroused tremendous interest among scientists. Tests have shown that SWNTs are 50 to 100 times stronger than steel, yet about six times lighter! Their elasticity is measured at 11.2 terapascal (TPa). Beyond these outstanding structural characteristics, several other remarkable properties have been observed. SWNTs conduct heat twice as efficiently as diamond, which is famous for its high thermal conductivity. Another fascinating feature of SWNTs is their electrical conductivity—10⁹ amps per square centimeter, which is 100 times more than copper! Not only that, but they remain stable up to 2700 degrees Celsius in a vacuum, meaning their structure doesn’t change under this extreme heat.

            Now the question arises—what can carbon nanotubes be used for? Their applications are abundant in semiconductor technology, precision instrumentation, medical science, and even the textile industry. Scientists are highly optimistic about their immense potential in electronics. Notably, these tubes may be used to make nonvolatile memory chips. If the atoms within a carbon nanotube can be arranged properly, it could become an ideal semiconductor material. This would allow us to make extremely tiny transistors, leading to computers and other electronic devices becoming unimaginably small.

Currently, CNT (Carbon Nanotube) based water and air purification systems are being used that can destroy bacteria. These tubes are now found in energy storage cells or batteries as well. They can also be used to make electrically conductive plastics with outstanding elasticity. Thanks to their very high electrical conductivity and ultra-fine tips, carbon nanotubes are utilized in making equipment for electro-magnetic field emission. Aside from these uses, CNTs are employed in various sensors, radio frequency devices, bolometers, nanomixers, membranes, valves, and more for medical applications.

It appears that, although the history of nanotechnology spans only a few decades, its progress and major discoveries have sparked a new chapter in the world of science. This technology has become a vital branch of science. The boundless passion and experimentation of countless scientists are pushing this field forward at a rapid pace. And this technology is paving the way for turning human imagination into reality. Perhaps the day is not too far off when Replicator-like machines will be in every home, and people will no longer only dream through science fiction.

Mahfuz

[email protected]

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