|
pencilvanian
1000+ Penny Miser Member
USA
2209 Posts |
 Posted - 11/05/2008 : 20:30:09
|
A long read but nice information for silver bugs
You must be logged in to see this link.
The Future Is a Silver Thread
27.10.2008 Silver is beautiful – but it can be much more than that. This precious metal has long been used in technology and medicine, but now nanotechnology makes it possible to coat fibers and materials with a very fine layer of silver particles. ECG measurements taken by your T-shirt, odorless sportswear, data exchange via your jacket – these ideas are not as far-fetched as you might think.
The Chinese have been using silver needles for acupuncture for around 7000 years. And in medieval times, if a nobleman feared for his life, he would simply test his wine with a little silver rod: if the metal turned black, it meant that his drink was spiked with arsenic. The special properties of this metal were recognized early on. We now know that in addition to a very high light-reflecting capacity of 98 percent, silver also offers unbeatable conductivity, combined with antistatic and antibacterial effects. The applications for this precious metal range from coins and jewelry to the automotive industry, photography, electronics and even antibiotics. Several years ago researchers at Empa decided to focus on the unique properties of silver, developing a new nanotechnique known as low-pressure plasma technology. Using this technology, silver-coated fibers can be produced in a more environmentally friendly way, using less metal than was possible with previous methods. Dirk Hegemann, head of the Plasma-Modified Surfaces group and holder of a doctorate in materials science, explains the main differences: "The galvanic bath, as we know it today, is a wet electrochemical procedure that is ideal for producing layers a few micrometers thick – a human hair, by comparison, is 50 micrometers thick. Textiles treated in this way are currently available on the market and are used to combat neurodermatitis, for example. After a few washes, however, these products show little or no effect because much of the silver has been washed out.
Half a Gram of Silver on a Kilometer of Fiber
Our technology, in contrast, is a dry physical process by which the silver particles are applied only to the surface of the fiber in a thin, highly adhesive layer." In the world of nanotechnology a "thin layer" can be anything from a few to several hundred nanometers, or millionths of a millimeter. This means that 0.5 grams of silver are applied to one kilometer of synthetic yarn. A fiber like this retains the properties of the silver, in particular its conductivity and antibacterial effect. But, because the textile properties also remain unchanged, it can be processed just like an uncoated fiber. "Silver nanoparticles can also be bought and melted into polymers. In this case the silver is present throughout the fiber, but it only takes effect on the surface when it interacts with an aqueous environment. In theory, yarn that has been coated using our process can release silver ions continuously for up to a year. The quantity of ions released depends on the structure and size of the surface, so the application is the key factor here," Hegemann says.
Antibacterial Effect Helps after Operations
Niklaus Zemp, managing director of Tersuisse Multifils SA, is convinced that there is no shortage of applications. Last year the company from Emmenbrücke in Switzerland took over Empa's patent rights for the fiber-coating process along with the pilot system. "Clean and constant release of silver ions is essential if we are to meet the quality requirements. We are currently in the middle of developing these metallized fibers. We have lots of ideas, but it's a new area and we now need additional partners to help us develop projects – in the field of antibacterial applications, for example," Zemp explains. Here he touches on the sector with probably the greatest potential: In itself, silver has no antibacterial effect. But when it comes into contact with water – whether in the body, on the skin, with sweat or airborne moisture – the metal surface oxidizes and antibacterial silver ions are washed out of this layer. The amount of silver that is released from a matrix depends on the particle density: The more ions are released, the greater the antibacterial effect. However, we also have to bear in mind that while some forms of bacteria can be destroyed very easily, others are almost impossible to kill, or can only be eradicated by using large amounts of silver. It can therefore be employed effectively in specific locations, for example hospitals, where the types of bacteria to be combated are known. However, the market for medical textiles is still very small. At present, only dressings for wounds are available. Research is still being carried out on bandages, for example, where the amount of silver released must be appropriate to the injury so as to avoid toxic effects. On the other hand, Hegemann sees enormous potential in the development of implants: "Silver nanoparticles embedded in a polymer matrix can produce an antibacterial effect for two or three days without the silver inhibiting cell growth. This would be very helpful after an operation." Other more futuristic possibilities include antibacterial clothing – and sportswear in particular. What about "odor-neutral" dancers in nightclubs, or changing rooms where your nose isn't assailed as soon as you walk in? Nice idea!
Changing Rooms – Odor-Free at Last!
Silver has even more to offer. It's also one of the best conductors of electricity and can therefore have an antistatic effect. "This would be ideal for work clothing," says Hegemann, "perhaps for surgeons in the operating room or for jobs involving microelectronic components. Or for filters in cars; or in industry, where it's essential to avoid the build-up of electrical charges." According to Hegemann, Empa tests show that silver-coated fibers incorporated into textiles are extremely durable and can survive more than 50 washes. Products made from conductive fibers – like gloves with an integrated user interface for a mobile phone or jackets that can transmit MP3 data – are no longer a futuristic vision: They're already on the market. Anything's possible, provided it doesn't involve high voltages and the associated risk of overheating. Imagine a T-shirt that not only measures bodily functions such as your pulse, but also can perform an ECG. Another potential application: A silver thread could be sewn into another material and used to test its integrity by moni¬toring the electrical resistance. A detector like this could save costs, particularly on the expensive filter materials used in industrial processes, where filters are routinely replaced without checking.
After the Research It's Time for Innovation
Having researched and developed the plasma process, Empa is already working on how to refine the fibers even further. Hegemann explains: "We're looking at how they react in contact with the skin and whether discoloration, for example, can be avoided. But we're also working on new developments: applying multiple layers, refining the data transfer technology, trying out different fibers. And we're thinking about using other metals, like gold, palladium or titanium. We also have ideas for using multiple coatings of different metals. If we could manufacture insulated textile wires and incorporate luminescent materials, you could even have television or computer screens integrated into your curtains." Hegemann eventually unveils his ultimate vision: "At present, textiles are often applied to the outside of Chinese high-rise buildings instead of plaster. If you used these to operate photovoltaic systems and harnessed the surface area of the building to generate power, this would make a clean and efficient contribution to the energy problem in Asia." Given the visionary quality of these ideas it's reassuring to know that the original idea is already being put into practice.
|
|
Silver & its uses
Forum Locked
