From 4600 BC to today’s nanotechnology: Silver has a long shelf life
A 27-year-old man was arrested in Yokohama last week for possessing two guns made by a 3-D printer, although the police found no bullets. Poor old Yoshitomo Imura was his own worst enemy: he posted footage of the guns on the internet along with a blueprint showing how to use a 3-D printer to make the weapons, and it wasn’t long before Yokohama’s finest were on his trail. According to the Nikkei news service, Imura had learned about the technology on the internet and had been encouraged by reports that a U.S. gunmaker had fired bullets from such a gun.
Fortunately, much of the new technology coming through has much more positive outcomes. For silver, which has been used for at least 6,500 years, the story just keeps getting better.
As I have pointed out before silver is used as a biocide — an agent capable of destroying organisms — in wound care, catheters, pacemakers, heart valves and feeding tubes. Silver interrupts the bacteria cell’s processes that allow it to survive: when a bacteria cells meets silver, it disintegrates. Johnson & Johnson and other healthcare companies routinely apply silver as an active ingredient to bandages and ointments. Silver-imbedded equipment (surgical tools, catheters, needles, stethoscopes and door handles) may prove the answer to the so far persistent “superbug”, or “Staph”, which is a big worry in hospitals around the world. Bandages often now include silver ions to combat bacteria growth. By 2020, around 600 tonnes a year of silver could be going into the health market.
Clean water is another big market. Silver is replacing chlorine in filtration; it prevents bacteria and algae building up in filters. Silver ions are being added to water purification systems in hospitals, pools and spas. The use of silver in water is a science that is still in its very early stages.
The latest bulletin from the Washington-based Silver Institute has some of the latest silver developments.
Tata Chemicals in India has developed what it calls its Swach Silver Boost, a new water purifier that can produced between 3 litres and 4 litres of water an hour that uses metallic silver. As the Silver Institute explains, up until now water filter systems have been only partially effective: chlorine, the basic water cleanser, does not block Cryptosporidium, while most membranes do not block all diseases, such as polio, hepatitis A or E. But, as Tata claims too, silver nanotechnologies make water safe from viruses, bacteria, parasites, algae, rust and fungus.
In another development, Chinese scientists have developed “smart tags” using silver and gold rods, microscopically tiny, that stick to food containers and change colour when the food has gone bad. The tags are about the size of a corn kernel and the Chinese say they can be made for about one cent each. The technology means that the state of the contained food can be judged without opening the container or touching the food inside.
And silver is now making medical testing faster and cheaper. Researchers at Cambridge University in Britain have come up with the idea of imbedding silver particles in hydrogels, which are highly-absorbent materials used in products ranging from contact lenses to disposable diapers. Once the silver is embedded, the metal particles can be hit with a laser beam forming holograms which change colour depending on whether the compound is glucose, alcohol, hormones, drugs, bacteria or pollutants. The researchers say these smart holograms hold the promise of detecting diabetes, drug use, cardiac abnormalities, infections or hormonal imbalances.
At present much medical testing is conducted on large, expensive equipment. The holograms are cheap and could be used for early diagnosis. The sensors involved would cost about 10c each.
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