Printed circuit tracks
Modern computer chips are based on the chemical element silicon, which is found, for example, in normal quartz sand. Around six hundred steps are required to manufacture one chip, which can take up to four weeks. Nanotechnology now means that electronic components can literally be printed. The primary role is played by a kind of ink of nanoparticles. This semiconducting material can be applied to various surfaces as conducting tracks using standard printing techniques. Complex electronic systems can also be mass produced on large areas of paper or film in this way. Such materials are considerably easier to recycle than standard semiconductor components. By reducing the number of production stages and using smaller amounts of materials, both raw materials and energy are saved. Printable electronics will make possible many technical applications for which the use of standard electronics is currently still too expensive. From watches to entry cards, ‘intelligent objects’ would be able to communicate with computers in their environment via radio signals to make life more pleasant.
Marble on a roll
Whether in the bathroom, utility room or kitchen, ceramics are a popular facing and decorative material. But anyone who’s ever laid ceramic tiles knows how difficult it is to cut this hard, brittle material – often enough it will just shatter. And it doesn’t matter how carefully you apply your grout, it can still offer a great habitat for bacteria and mould. Using nanotechnology, a German chemical company has developed “marble on a roll”. The product is flexible, tough and can even be cut to fit individual requirements. This novel wall covering consists of a maximum of four layers. The base is a polymer fleece, which is covered with a ceramic metal oxide layer. It can be printed as required. The bottom coats are then also covered with a ceramic protective layer. The resultant material is extremely lightweight, scratch and impact resistant, chemical resistant and resistant to ultraviolet light. It withstands heat and flames and is water resistant yet breathable. Because it is applied without joints, there are fewer points vulnerable to dirt and mould. A further advantage is the low-energy manufacturing process. Whilst manufacture of normal ceramics requires temperatures of 1250 °C, 250 °C is sufficient for ceramisation of “marble on a roll”.
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The clean facade
Home-owners face substantial costs in repainting their facades once the paint turns grey. A self-cleaning facade could help save plenty of money. There are now a number of exterior paints which use nanotechnology to ensure that walls remain cleaner for longer. In one type of paint, the sun activates a photocatalyst. The catalyst decomposes strongly adhered dirt so that it is washed off the facade the next time it rains. Another paint makes use of the ‘lotus effect’. Facades to which this paint has been applied have a highly water-repellent surface similar to that of a lotus leaf. It dramatically reduces the contact surface for water and dirt. Dirt particles barely adhere and are simply pulled off by raindrops rolling off the surface. In a third type of paint, innovative binders form an extremely fine network structure. The principle behind it is that inorganic nanoparticles and organic polymer particles are processed to an aqueous dispersion (nanocomposite dispersion) and fixed. After applying the paint and allowing it to dry, the nanoparticles form a homogeneous three dimensional network which not only protects against dirt, it also keeps the paint looking good for longer. The network structure of the nanoparticles also offers some protection against fire, as it prevents the paint film from melting, thereby slowing the rate at which fire spreads.
A different way of looking at paint
An example of the unusual paints manufactured using nanotechnology can be found in the car industry. Instead of standard single-colour pigments, microscopically small silica discs are mixed into the paint. These discs are coated with a layer of metal compounds just a few nanometres thick. This layer influences the way in which light is refracted by the discs. The vehicle body thus, for example, looks red when observed from an angle from in front, but green when observed from an angle from behind. By changing the thickness of this layer and adding standard pigments, it is possible to determine the colour profile pretty much however you want. Nanomaterials thus give this vehicle a very special aura.
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Targeted drug deployment
Drugs usually disperse throughout the body before finding their way to the diseased body part, frequently leading to side-effects. This is particularly apparent in the case of chemotherapy for cancer patients. Although it kills fast-growing cancer cells, other equally fast-growing cells, such as hair cells, also die. Nanotechnology is therefore researching particles which treat diseased tissue directly and exclusively. A number of approaches are being used. One possibility is nanocontainers. The actual drug is held within the containers, which transport it specifically to the sick cells. The difficulty for the nanoparticles is differentiating sick cells from healthy ones. The particles also have to overcome obstacles such as the body’s immune system or pass cell or mucus layers without getting stuck. There are methods for adapting the physical, chemical and biological properties of the nanoparticles to achieve this. Size and structure play an important role, as does whether a surface is rough, water-repellent or lipophilic. Nanocontainers also need to have sufficient storage space for their cargo and must not themselves have any toxic effects on the body. Research into such nanoparticles requires a great deal of know-how, patience and money, but success is already being achieved with nanoscale liposomes, polymer nanoparticles and micelles. Hepatitis C, for example, can be treated in this way using products derived from nanotechnology. A further nanoworld technology is based on selectively enriching magnetic nanoparticles in a tumour. These can be made to move using an external magnetic field such that they heat up and destroy the cancer cells. Because they don’t penetrate healthy cells, the latter are not affectedn.
New diagnostic procedures
Ultrasound, magnetic resonance and nuclear procedures are poorly suited to providing information on the cause or stage of an illness. It is molecular biology which has clarified the molecular processes within a cell and is today delivering insights into how illnesses arise and develop. In doing so, it uses markers such as antibodies. These markers attach to specific proteins or DNA molecules and can be visualised. In order to detect diseased tissues, markers can also be used as contrast media. These concentrate specifically in the target tissue. Traditional imaging techniques, however, are not always adequate for detecting such small variations in concentration. For this reason, there is much discussion of contrast media which are able to detect even the smallest marker concentrations. Nanoparticles consisting of gadolinium atoms are being developed to image cancerous tissues or atherosclerotic deposits. But markers for biological molecules do not just help improve diagnosis, they also offer new measurement techniques. Gold nanoparticles attached to DNA molecules could soon help detect diseases such as cancer, Alzheimer’s and cystic fibrosis. The DNA molecules are complementary to the disease gene and form clusters of particles as soon as they encounter the relevant gene in a clinical sample. A colour change in the solution indicates diseased tissue. This technique is already used in pregnancy tests. Another procedure uses cantilevers with a length of 10 - 100 µm and a thickness in the micrometre or nanometre range. These bend when a protein or DNA molecule coated with them reacts to a specific target molecule. The deflection of the cantilever can be detected using a laser.
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Better implants
Human life expectancy is steadily increasing, the durability of bone, however, isn’t. Implants aim to help people stay mobile in their later years. The crucial factor is that implants are accepted by the body and are long-lasting. Nanostructures on the surface of implants could help to improve the tissue integration properties of implants. Initial experiments show that bone cells and proteins interact better with such implants, improving integration into the tissue. In the joints, which are in constant motion, titanium implants are loosened by the friction between the bone and the prosthesis. As a result of their low friction and their hardness, nanocrystalline diamond coatings help to reduce abrasion and increase the long-term stability of implants. Nanotechnology is also making progress in the field of bone replacement materials. Bone-like cements made of nanocrystalline bio-materials are already on the market and are used in treating bone defects. As healing progresses, the nanostructure allows the invading bone-forming cells to replace the artificial bone component.
Adhesion at the push of a button
Adhesives are playing an increasing important role in car manufacture. They offer the advantage over welding that they can be used to bind together metal and plastic. Not only do they contribute to making cars lighter, they also ensure more crash-resistant car bodies able to absorb up to 20 % more impact energy. Until recently, however, adhesives had to be cured at high temperatures in special presses for several minutes. This took valuable production time and also consumed energy, as both the work piece and the adhesive were heated. Because of this, a German company has developed a new adhesive in its laboratories. At its core are nanoparticles made from iron compounds. Instead of heat, magnetism is used to trigger the adhesion process. If a rapidly fluctuating magnetic field is precisely place over the adhesion surface in a small area, the particles oscillate back and forth like tiny compass needles, heating up as they do so, so that the adhesive hardens very rapidly. This offers future car manufacturers the advantage that they no longer need to heat the whole work piece, thus saving energy, and that the rapid hardening allows faster production. Since the adhesive can be softened by reapplying the magnetic field, this simplifies both repairs to the vehicle and vehicle recycling.
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Better batteries
In mobile phones, laptops, PDAs and many other devices, electricity is provided by small, compact lithium ion batteries. They are lighter and more powerful then the lead and nickel cadmium alternatives. Use of larger lithium ion batteries, however, currently suffers from safety problems. The material used to keep the positive and negative poles apart, known as a separator, is made of plastic. If this overheats and melts during charging, the battery can explode. One company has therefore used nanotechnology to develop a separator made from a ceramic coated polymer membrane which does not melt. The new film has been in production since early 2006. The new membrane means that for the first time large lithium ion batteries with higher storage capacities can be used in electronic devices and vehicles. The film makes possible the development of high-performance hybrid electric vehicles, of which they are an important component, and helps smooth the way to market for this environmentally-friendly vehicle type. Hybrid electric vehicles are a fuel saving, green alternative to petrol engines, since they use 25 percent less petrol and produce significantly lower exhaust emissions.
Nanocube super storage
Laptops and mobile phones are not only getting ever smaller, they are also getting ever more powerful. Batteries need to keep up with this constant development. For many users, the storage capacity of normal energy carriers is already insufficient. Manufacturers are pinning high hopes on fuel cells. Currently, to obtain energy from fuel cells hydrogen needs to be released from petrol or ethanol in a chemical reaction. This takes place in what is known as a reformer. The reaction between hydrogen and oxygen to produce water releases a large amount of useable energy. Running fuel cells directly using pure hydrogen would, by contrast, be a simpler and cleaner alternative. To achieve this, however, the hydrogen must be stored safely until it is needed and be available at a reasonable price. This is where conventional technologies run into difficulties, because hydrogen does not become liquid until you reach a temperature of minus 253 degrees and a pressure of 300 bars. A German chemical company’s ‘Nanocube’ could, however, soon overcome these hurdles. The microscopically small cube consists of a perforated grid of metal compounds and organic substances. Its numerous nanopores are able to absorb enormous quantities of gases. The network of pores in just two and half grams of this cube has the surface area of a football field – offering plenty of space for storing hydrogen. It is deposited in a thin layer on the walls of the pores. By rapidly reducing the pressure, it regains the properties of a gas and is completely released from the cube. This principle can be used to create mini fuel cells which are smaller, lighter and more powerful than current batteries. Laptop batteries could allow ten hours of continuous use.
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