A floor heating system powered by a 12V battery? Why not-just use a carpet with carbon nanotubes.

Heating systems with nanotubes can be sprayed onto the floor covering, or nanotubes can be added to polymers used in the carpet production process. The plastic or fabric modified in this way can be connected to a source of low-voltage electricity, and that is enough to heat up a floor of almost any size.

This is no fiction. The prototype of such a heating surface has already been produced and patented. It is a fabric with modified carbon nanotubes. The inventor, Jerzy Peszke, Ph.D., from the Institute of Chemistry and Environmental Protection of the Jan Długosz Academy in Częstochowa, has developed several ways of using carbon nanotubes for heating various surfaces.

The heating surface may be either a floor covering or a wall covered with paint that includes nanotubes. Peszke and the patent's owner, the Nanoco company from the city of Tarnowskie Góry in southern Poland, are talking to implement the technology in industry. Other inventions resulting from Peszke's work with Nanoco have already attracted the interest of several industrial plants. For example, a floor covering factory in Lubliniec will soon start producing a kind of linoleum modified with nanosilver to provide the floor with bactericidal properties.

Invisible but all-important

The industrial revolution of the 19th century is usually attributed to the steam engine, while silicon takes credit for the technological progress of the 20th century. 21st-century science will certainly be based on nanotechnology. "In 10 years, the prefix 'nano' will be used in any field you can think of," says Peszke. Actually, nano-molecules have always been present in our life; it's just that we weren't aware of this. All nature is based on "nanotechnology," its processes taking place at the level of cells, molecules and atoms. Contemporary research aims to discover the mechanisms that govern nature, and then to develop ways of controlling individual atoms and atom structures/molecules in order to obtain materials with new properties. Nanotechnology takes advantage of the fact that many materials display different properties on the nano and macro scales.

This offers great opportunities, but also creates difficulties. After all, you have to learn to control something you cannot see. Peszke has focused his research on carbon nanotubes. These are carbon structures that can be as thin as 1 nanometer in diameter (1 nanometer is one millionth of a millimeter). They are more durable than steel and their bonds are stronger than those in a diamond. They are extremely resistant to stretching and have unique electrical properties. Depending on the method of synthesis and subsequent modification, they can be used as conductors, semi-conductors or insulators. The prototypical heating surface uses their thermal properties-the fact that they are excellent heat conductors.

Researchers expect that carbon nanotubes will be able to transmit up to 6,000 W/m•K (watts per meter-kelvin) at room temperature, W/m•K being a unit of heat conductivity. In comparison, copper, considered an excellent heat conductor, only transmits 385 W/m•K. Nanotubes can withstand a temperature of up to 2,800 degrees Celsius in vacuum and up to 750 degrees Celsius in air.

"For a chemist, the structure of carbon nanotubes is not very interesting," says Peszke. "It's just like a sheet of graphite, only rolled up to form a cylinder." Still, humanity has never had such an amazing tool before. The chemical properties of nanotubes make them a perfect material for chemical modifications that open up possibilities for many new applications. Nanotubes, when synthesized with the conventional arc discharge method, are usually produced from graphite, the cheapest source of carbon. In order to use nanotubes obtained in such a way for further synthesis, you have to clear them of a byproduct called amorphic carbon. After several clearing sessions, the nanotubes, enriched with chemical functional groups, obtain new chemical and physical properties. For example, they can be dissolved in polar solvents such as water, alcohol or acetone. After obtaining a mixture with carbohydrates, it is possible to generate fat-soluble compounds. This opens up the way to synthesizing biologically active nanosystems, which makes carbon nanotubes an excellent tool for medicine. They can also be combined with polymers and have hundreds or even thousands of other possible applications. For example, they could be used to make indestructible car bodies and bulletproof vests that would be just 2 millimeters thick. They could also be used in a myriad of ways in the aviation and semiconductor industries.

Nanotubes vs. cancer

The Jan Długosz University in Częstochowa, a city 220 km south of Warsaw, is among the strongest nanotechnology centers in Poland. It collaborates with many other centers at home and abroad, particularly in the Far East. Peszke once worked in Taiwan and South Korea, for example. In Poland, he has worked with researchers such as Leszek Stobiński, Ph.D., from the Institute of Physical Chemistry of the Polish Academy of Sciences (PAN). Together, they have developed some of the methods for the chemical modification of nanotubes.

The Chemistry and Environmental Protection Institute of the Jan Długosz University in Częstochowa is working on technologies that have drawn the attention of both other scientists and industry. A manufacturer of bulletproof vests wants to reinforce its products with the use of nanotechnology and develop a method for repairing damaged vests. Such vests are used by Polish troops serving in international missions in the Middle East, for example.

The institute has also designed special sports clothes with carbon nanotubes based on the prototype heating surface. However, the biggest hopes are being pinned on the use of nanotubes in medicine, particularly in cancer therapy. The institute's "non-surgical selective method" for fighting cancer cells has already undergone tests, and the results are promising. The black liquid in the small tube shown by Peszke in the photo is in fact a ready "cure for cancer." The liquid contains magnetic nanocapsules as the main component of a nanocomposite that is expected to become a weapon against cancer. The magnetic nanocapsules have been developed by Prof. Andrzej Huczko and Dr. Michał Bystrzejewski. Peszke has modified the nanocapsules to enable their use as a medication.

"In this case, nanotubes play the role of a vehicle that transports biologically active chemical compounds to a precisely determined area of the body," says Peszke. The combination that is already undergoing clinical tests includes folic acid, magnetic nanocapsules and a photosensitizer based on porphyrin. One end of the nanotube has several dozen molecules of folic acid attached chemically, while the other end has porphyrin structures attached. The so-equipped nanotube is expected to attach to cancer cells that need folic acid for DNA replication. Such a complex achieves the highest concentration in the proximity of cancer cells and after it gets attached to them, doctors can observe the shape, size and type of tumor. The next step involves exposure to laser light of appropriate wavelength in order to stimulate the porphyrins to start cytotoxic reactions. The effectiveness of this type of therapy depends on the degree of malignancy, but it is generally no less than 60 percent. Paradoxically, better results are achieved with malignant tumors. Nanotubes can also be combined with vitamins or cytostatics and sent to a precisely defined area of the body.

From lab to factory

This is how medicine may look in the future. But, for the time being, the invention is sitting on a laboratory shelf along with several other nanotechnologies developed at the Jan Długosz University. Their use in industry is obstructed by formal and procedural obstacles rather than a shortage of funds. Paradoxically, these inventions show that advanced technology is not necessarily expensive. "The technologies we offer have to be inexpensive; low price is among our priorities," says Peszke.

Private companies have appreciated this low-cost strategy. The institute works with the Nanoco company from Tarnowskie Góry that runs innovative nanotechnology programs. One example of a successful transfer of technology from academia to industry is a product containing nanosilver that has been developed with Peszke's involvement. Industrial production began a year ago. Meanwhile, talks on the production of heating surfaces made of carbon nanotubes are also promising; Nanoco has received the first prototype.

"Nanotubes will keep surprising us with their potential for a long time," says Peszke. "They are already a great tool for industry, biology and medicine, and there are many more areas where we don't know how to use them yet." For example, many scientists dealing with the synthesis of nanomaterials dream about producing long threads of carbon nanotubes. They already know how to connect nanotubes like pieces of a rope but the threads are still too short. Once a method for extending them in a significant way is developed, the range of applications of such a "rope" will be limited only by human imagination.

Ewa Dereń