THE NANO ”TECHNOLOGY”

“The next big thing is really small”
-Jack Uldrich

THE NANO ”TECHNOLOGY”

Nano as the prefix implies a scale of 10^-9 and nanotechnology is the manipulation of matter at the atomic or molecular scale and building materials with at least one dimension under 100 nanometers. Although the first reference towards nanotechnology was given by legendary Richard Feynman in 1959, carbon nanotubes were only introduced in 1991 and since then have become the focal point of the scientific community. From supercomputers to space elevators, their use have been envisioned in everything.

If you peer down with a good microscope you'll observe, that at the atomic level, carbon nanotubes resemble your nylon clothing line. Only instead of nylon, the tube is made from hexagonal lattice of carbon atoms. The tubes are in the order of nanometers in diameter. Their structural strength makes them an ideal composite material, while its electrical conductivity makes it suitable for deployment as a semiconductor alternative.

CURRENT APPLICATION

1. COPPER REPLACEMENT (LONG FIBERS)

Today nanotubes are commonly produced in segments about 10,000 nanometers long, forming a black powder. Nanocomp Technologies of Concord manufacture lightweight antennas, cables, and electromagnetic interference shields using this material for the military and aerospace markets.

The heart of Nanocomp Technologies’ manufacturing process is a long, cylindrical furnace. A reaction gas comprising carbon- based feedstock which is raw material is fed into the furnace. The gas is swept along the furnace until it meets a heated, porous block coated with a catalyst.

As it through the pores, the gas is forced to be in contact with the catalyst, and carbon nanotubes are formed. A temperature gradient between the porous block and the open end of the furnace supports the tubes as they grow, absorbing material from the reaction gas. Eventually, nanotubes leave the cylindrical furnace, looking like a black mass of tube-shaped cotton candy. A conveyer belt captures the nanotubes as they emerge, turning them into yarn and sheets.

They are also producing sheets of carbon nanotubes that measures 3X6 feet and have announced plans to produce slabs with an area of 100 square feet. These sheets will be used primarily in as electrical conductors in planes and satellites to replace copper wire and reduce weight hence increase fuel efficiency. The resulting material can be a valuable addition to such applications such as electromagnetic interference (EMI) shielding, electrical conductors, thermal dissipation solutions, lightning protection and advanced structural composites. Another interesting use due to structural strength of the material is as a substitute for Kevlar as body armor.

2. AGRICULTURE

Carbon nanotubes are being used to accelerate the growth in size, quantity and speed of vegetables like tomatoes. In September 2009, at the Little Rock Nanotechnology Center, housed at the University of Arkansas, used carbon nanotubes to increase the germination rate of tomatoes. Exposure to carbon nanotubes caused the seedlings to become stronger and grow more quickly. Carbon nanotubes become a part of the seed by penetrating through the thick outer shell and bonding with the plant structure that enables the plants to take in more water and also retain it, creating a plant that could possibly survive longer spells of drought after long rain fall.

FUTURE APPLICATIONS

Although current application may be limited by the prohibitive cost of $95 per gram at present. Probably with time, it would become more affordable.

1. HYDROGEN STORAGE

Carbon nanotubes have, for long, been championed as a strong contender for storing hydrogen in fuel cells.

2. IMPROVED TRANSISTORS

Semi conducting Carbon nanotubes have been used to fabricate field effect transistors (CNTFETs), which show promise due to their superior electrical characteristics over silicon based MOSFETs. Since the electron mean free path in SWCarbon nanotubes can exceed 1 micrometer, long channel CNTFETs exhibit near-ballistic transport characteristics, resulting in high speed devices. CNT devices are projected to operate in the frequency range of hundreds of Gigahertz. Recent work detailing the advantages and disadvantages of various forms of CNTFETs have also shown that tunneling CNTFET offers better characteristics compared to other CNTFET structures. This device has been found to be superior in terms of sub threshold slope - a very important property for low power applications.

3. WATER FILTER

Researchers at the Bhabha Atomic Research Center in India are investigating the hollow carbon fibers as a potential water filter. They believe the unique chemical properties of nanotubes mean that only water molecules can pass through their interiors, while toxic metal ions, viruses, and bacteria cannot.

Additionally, the smooth, water-repellent interior of the nanotubes means that a filter made from the technology would have a high flow rate of water without fouling—so it would be very efficient.

But there’s still plenty of work to be done before carbon nanotubes are a viable option for filtering. The Indian research team is currently trying to engineer nanoscale structures to form arrangements that can efficiently decontaminate water.

With the rapid rise of contaminated drinking water around the world, solutions are desperately needed. Since poor countries are more likely to lack access to drinking water, a carbon nanotube filter will be most useful if it is both simple and cheap to operate and maintain. And if that massive hurdle is surpassed, developing nations may suddenly be a lot better off.

4. BREAST CANCER RESEARCH

Single-walled carbon nanotubes have been highly touted for their potential as novel delivery agents for cancer detection and therapeutic agents. Now, a team of investigators from six institutions have created multifunctional carbon nanotubes that can detect and destroy an aggressive form of breast cancer.

HER2 is one of a family of genes that help regulate the growth and proliferation of human cells. Normal cells have two copies of HER2, but about 20 to 25 percent of breast cancers consist of cells have multiple copies of the gene, resulting in the overproduction of a HER2-encoded protein that is associated with particularly fast growing and difficult to treat tumors

In a paper published in the journal BMC Cancer, the team led by Huixin He, Ph.D., of Rutgers University, and Yan Xiao, Ph.D., of the National Institute of Standards and Technology (NIST), described how it created the new dual-purpose nanostructure by attaching an anti-HER2 antibody to short carbon nanotubes. The investigators then took advantage of two unique optical properties of carbon nanotubes to detect and then destroy HER2 breast cancer cells. Near-infrared laser light at a wavelength of 785 nanometers reflects intensely off the nanotubes, and this strong signal is easily detected by a technique called Raman spectroscopy. Increase the laser light’s wavelength to 808 nanometers and it will be absorbed by the nanotubes, incinerating them and anything to which they’re attached—in this case, the HER2 tumor cells.

5. BATTERY

Flower-shaped nanoparticles, or “nanoflowers”, might lead to superior batteries in the near future. Chemist Gaoping Cao and colleagues report in the latest issue of Nano Letters that they are working on developing nanoflowers which could lead to longer battery life for cell phones, laptops, and more.

While nanoflowers are not new, Cao claims that previously discovered forms of the nanoparticle weren’t able to provide the longer battery life that will be necessary for electronics of the future.

In Cao’s study, scientists grew clusters of carbon nanotubes—each 50,000 times smaller than a strand of human hair—that have strong electrical conductivity. They then put manganese oxide on top of the nanotubes. The process resulted in dandelion-shaped nanoclusters that will ultimately lead to a battery system with a higher energy storage capacity, longer life, and greater efficiency that current batteries.

And while I would be happy to have a more self-sustaining laptop, perhaps the nanoflowers will have even more important uses— like keeping future plug-in hybrid vehicles running for longer.