Saturday, January 14, 2012

'Nano ears' detect sound made by cells and viruses

Even the tiniest things make sounds, such as cells, viruses and bacteria. We just don't have the necessary equipment to detect it. Scientists from a university in Munich have developed a 'nanophone', which is both tiny and capable of registering sounds that tiny things make. It gives us a way of listening to the noise that cells and microbes make.

Gold sphere
The nanophone is spherically shaped and made of gold particles. To perform as tiny microphones, the German scientists trapped the spheres in a laser beam. This made them susceptible to changes in their environment. In the human body, sound waves manifest as ripples that disturb the water around the source. The nanophone detects these ripples because it responds to pressure differences.

To test the nanophone, a second laser fired light pulses at an area close to the gold spheres. It creates sound waves of a specific frequency, which in turn made the nanophone jiggle back and forth. Because the jiggling is specific for each sound frequency, reading its movements tells us something about the sound that tiny things such as cells, if they are in the neighbourhood, are making. According to the German researchers, the sensitivity of the laser-trapped gold spheres is unmatched: they are able to record sound at one millionth of what the human ear can detect.
By listening to cells, we gain knowledge of properties we were previously unable to study. We already know cells ought to make sounds, because they are occasionally seen vibrating under a microscope. In addition to telling us something about its mechanical properties, we are able to detect changes in frequencies, for example during infection. This way it may give us a new set of diagnostic tools. However, more tests are required to discover how this system can be applied in the clinic.

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