Thursday, January 9, 2014

Black Silicon: a violent nanotechnology

In the month of September 1928, a scientist called Alexander Fleming returned home after enjoying a holiday with his family. Fleming was a brilliant but untidy researcher. Before going on holiday in August, he had stacked his experiment material carelessly on a bench. In the material were some dishes in which Fleming was growing a bacteria of the weighty name Staphylococcus aureus.
Fresh from vacation, he pulled out the culture dishes. In one of the dishes, a mould was growing, just like what we see sometimes growing on a piece of bread forgotten in a corner. Before throwing it out, Fleming had a good look at the dish, and was rewarded with a wonderful sight. The bacteria around the mould had vanished. The mould had killed it. This was the discovery of penicillin, and beginning of the antibiotics industry. Man had won, bacteria had lost.
But Staph aureus, the bacteria that causes diseases like pneumonia and meningitis was not going to give up so easily. By 1960, it developed resistance and could no longer be killed by penicillin. More and more powerful antibiotics with cracking names were discovered – Methicillin, Oxacillin, Streptomycin. But Staph kept on developing resistance. Today, Staph infections is a major menace in Hospitals, and most infections require expensive and risky treatment.
It has happened not only with Staphylococcus aureus, but with many other bacteria. The most famous example is the TB bacteria, Mycobacterium tuberculosis. These bacteria are no longer responding to common antibiotics. Antibiotic resistance is one of the major problems for public health in 21st Century. We are going to need alternate ways of fighting bacteria.
One ray of hope has arrived in form of a interesting research story. It’s a thrilling case of nature teaching us a thing or two.
Scientists found that the wings of Wandering Percher dragonfly (‘Chatur’ in Hindi - do a google search and see the images) can kill bacteria. They examined the wings and found something unique. The wings of dragonfly have very small needle-like structures. The needles are only 250 nanometre long. These knives actually stab the bacteria and leave them harmless!
(To understand what a nanometre is, take a one millimetre long needle and cut it into 1000 parts. Now, grab hold of one of those invisible parts, and again cut into 1000 parts. One of the parts that you are now holding is a nanometre long.)
Researchers got an excellent idea to work with. They identified a material called Black Silicon. This material is made by processing the surface of normal silicon in a certain way. It has nano-needles on its surface that are even longer than the dragonfly.
Black Silicon was tried on the Staph aureus bacteria, and it came out victorious. A one centimetre by one centimetre piece of Black Silicon can kill 4,50,000 bacteria per minute!
Even though the cost of this material is high today, this gives us a whole new weapon in our battle with bacteria. In future, we may be able to protect ourselves from the oldest enemy of mankind with antibacterial clothes!

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