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Nanotubes |Carbon Nanotubes
The properties of carbon nanotubes have caused researchers and companies to consider using them in several fields. The following survey of carbon nanotube applications introduces many of these uses.
Carbon Nanotubes and Energy
Researchers at Rice University have developed electrodes made from carbon nanotubes grown on graphene with very high surface area and very low electrical resistance. The researchers first grow graphene on a metal substrate then grow carbon nanotubes on the graphene sheet. Because the base of each nanotube is bonded, atom to atom, to the graphene sheet the nanotube-graphene structure is essentially one molecule with a huge surface area.
Researchers have built a solar cell that uses graphene as a electrode while using buckyballs and carbon nanotubes to absorb light and generate electrons. This process produces a solar cell composed only of carbon. The intent is to eliminate the need for higher cost materials and the complicated manufacturing techniques required to build conventional solar cells.
Using carbon nanotubes in the cathode layer of a battery that can be produced on almost any surface. The battery can be formed by simply spraying layers of paint containing the components needed for each part of the battery.
Carbon nanotubes can perform as a catalyst in a fuel cell, avoiding the use of expensive platinum on which most catalysts are based. Researchers have found that incorporating nitrogen and iron atoms into the carbon lattice of nanotubes results in nanotubes with catalytic properties.
Other applications in this area include:
- Combining carbon nanotubes, bucky-balls, and polymers to produce inexpensive solar cells that can be created by simply painting a surface.
- Producing ultracapacitors using nanotubes that may store much more energy than batteries in hybrid cars.
- Using nanotube electodes in thermocells that generate electricity from waste heat.
Carbon Nanotubes In Healthcare
Researchers have demonstrated artificial muscles composed of yarn woven with carbon nanotubes and filled with wax. Tests have shown that the artificial muscles can lift weights that are 200 times heavier than natural muscles of the same size.
Nanotubes bound to an antibody that is produced by chickens have been shown to be useful in lab tests to destroy breast cancer tumors. The antibody-carrying nanotubes are attracted to proteins produced by one type of breast cancer cell. Once attached to these cells, the nanotubes absorb light from an infrared laser, incinerating the nanotubes and the attached tumor.
Researchers at the University of Connecticut have developed a sensor that uses nanotubes and gold nanoparticles to detect proteins that indicate the presence of oral cancer. Tests have shown this sensor to be accurate and it provides results in less than an hour.
Medical implants made of porous plastic, coated with carbon nanotubes are being used for drug delivery. Therapeutic drugs, which are attached to the nanotubes can be released into the bloodstream, for example, when a change in the blood chemistry signals a problem. NASA is developing such an implant, called a "biocapsule", to protect astronauts from the effects of radiation. The implants may also be useful for releasing insulin in diabetic patients and for delivering chemotherapy drugs directly to tumors.
Other applications in this area include:
- Improving the healing process for broken bones by providing a carbon nanotube scaffold that new bone material can grow around.
- Using nanotubes as a cellular scale needle to deliver quantum dots and proteins into cancer cells.
Carbon Nanotubes and the Environment
Carbon nanotubes are being developed to clean up oil spills. Researchers have found that adding boron atoms during the growth of carbon nanotubes causes the nanotubes to grow into a sponge like material that can absorb many times it's weight in oil. These nanotube sponges are made to be magnetic, which should make retrieval of them easier once they are filled with oil.
Carbon nanotubes can be used as the pores in membranes to run reverse osmosis desalination plants. Water molecules pass through the smoother walls of carbon nanotubes more easily than through other types of nanopores, which requires less power.
Sensors using carbon nanotube detection elements are capable of detecting a range of chemical vapors. These sensors work by reacting to the changes in the resistance of a carbon nanotube in the presence of a chemical vapor.
An inexpensive nanotube-based sensor can detect bacteria in drinking water. Antibodies sensitive to a particular bacteria are bound to the nanotubes, which are then deposited onto a paper strip. When the bacteria is present it attaches to the antibodies, changing the spacing between the nanotubes and the resistance of the paper strip containing the nanotubes.
Carbon nanotubes tipped with gold nanoparticles can be used to trap oil drops polluting water. Since the gold end is attracted to water while the carbon end is attracted to oil. Therefore the nanotubes form spheres surrounding oil droplets with the carbon end pointed in, toward the oil, and the gold end pointing out, toward the water.
Carbon Nanotubes Effecting Materials
Researchers are developing materials, such as a carbon nanotube-based composite developed by NASA that bends when a voltage is applied. Applications include the application of an electrical voltage to change the shape (morph) of aircraft wings and other structures. This video from NASA gives you an idea of what a futuristic morphing aircraft might look like.
Researchers have found that carbon nanotubes can fill the voids that occur in conventional concrete. These voids allow water to penetrate concrete causing cracks, but including nanotubes in the mix stops the cracks from forming.
Other applications in this area include:
- Aircraft using carbon nanotubes to increase strength and flexibility in highly stressed components.
- A lightweight, low power anti-icing system using carbon nanotubes in a layer coated onto aircraft wing surfaces.
- Static dissipative plastic molding compounds containing nanotubes that can be used to make parts such as automobile fenders that can be electrostatically painted.
- Strong, lightweight composites of carbon nanotubes and other materials that can be used to build lightweight spacecraft.
- Cables made from carbon nanotubes strong enough to be used in building the Space Elevator to drastically reduce the cost of lifting people and materials into orbit.
Carbon Nanotubes and Electronics
Building transistors from carbon nanotubes enables minimum transistor dimensions of a few nanometers and the development of techniques to manufacture integrated circuits built with nanotube transistors.
Other applications in this area include:
- Carbon nanotubes used to direct electrons to illuminate pixels, resulting in a lightweight, millimeter thick "nanoemissive" display panel.
- Printable electronic devices using nanotube "ink" in inkjet printers
- Transparent, flexible electronic devices using arrays of nanotubes.
Carbon Nanotube Company Directory
| Company | Products |
| Nano-Proprietary, Inc | Sensor based upon enzyme coated carbon nanotubes for analyzing chemicals in liquid samples. |
| ZinRay Systems | Nanotube based X-ray systems |
| Zyvex Preformance Materials | Epoxy resins strengthened with carbon nanotubes |
| Hyperion | Nanotube based plastic mold compounds |
| Nano Lab | Functionalizied nanotubes and nanotube arrays |
| Bayer Material Science | Carbon nanotubes |
| Cheap Tubes | Carbon nanotubes |
| Catalytic Materials | Carbon nanotubes and graphite nanofibers |
More Nanotube Companies
Compiled by Earl Boysen of Hawk's Perch Technical Writing, LLC and UnderstandingNano.com. You can find him on Google+.
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