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.
Researchers at North Carolina State University have demonstrated the use of silicon coated carbon nanotubes in anodes for Li-ion batteries. They are predicting that the use of silicon can increase the capacity of Li-ion batteries by up to 10 times. However silicon expands during a batteries discharge cycle, which can damage silicon based anodes. By depositing silicon on nanotubes aligned parallel to each other the researchers hope to prevent damage to the anode when the silicon expands.
Researchers at Los Alamos National Laboratory have demonstrated a catalyst made from nitrogen-doped carbon-nanotubes, instead of platinum. The researchers believe this type of catalyst could be used in Lithium-air batteries, which can store up to 10 times as much energy as lithium-ion batteries.
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.
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Reseachers at MIT have developed a sensor using carbon nanotubes embedded in a gel; that can be injected under the skin to monitor the level of nitric oxide in the bloodstream. The level of nitric oxide is important because it indicates inflamation, allowing easy monitoring of imflammatory diseases. In tests with laboratory mice the sensor remained functional for over a year.
Researchers are improving dental implants by adding nanotubes to the surface of the implant material. They have shown that bone adheres better to titanium dioxide nanotubes than to the surface of standard titanium implants. As well they have demonstrated to the ability to load the nanotubes with anti-inflammatory drugs that can be applied directly to the area around the implant.
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:
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. Other researchers are using carbon nanotubes to develope small, inexpensive water purification devices needed in developing countries.
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.
Researchers at the Technische Universität München have demonstrated a method of spraying carbon nanotubes onto flexible plastic surfaces to produce sensors. The researchers believe that this method could produce low cost sensors on surfaces such as the plastic film wrapping food, so that the sensor could detect spoiled food.
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.
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.
Researchers at MIT have developed a method to add carbon nanotubes aligned perpendicular to the carbon fibers, called nanostiching. They believe that having the nanotubes perpendicular to the carbon fibers help hold the fibers together, rather than depending upon epoxy, and significanly improve the properties of the composite.
Avalon Aviation incorporated carbon nanotubes in a carbon fiber composite engine cowling on an aerobatic aircraft to increase the strength to weight ratio. The engine cowling is highly stressed components in this aircraft, adding carbon nanotubes to the composite allowed them to reduce the weight without weakening the component.
More about Carbon Nanotubes in Materials
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.
Researchers at Stanford University have demonstrated a method to make functioning integrated circuits using carbon nanotubes. In order to make the circuit work they developed methods to remove metallic nanotubes, leaving only semiconducting nanotubes, as well as an algorithm to deal with misaligned nanotubes. The demonstration circuit they fabricated in the university labs contains 178 functioning transistors.
Other applications in this area include:
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|Bayer Material Science||Carbon nanotubes|
|Cheap Tubes||Carbon nanotubes|
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Compiled by Earl Boysen of Hawk's Perch Technical Writing, LLC and UnderstandingNano.com. You can find him on Google+.