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Scales and Weights Have Just Gone Down the Tubes

You know your weight… well, maybe within 10 pounds or so. That’s because you regularly stand on a springloaded device that stretches the spring according to your mass and the force applied by gravity. But what if you wanted to weigh something as small as a virus?

It’s true that we have exotic devices called mass spectrometers, which can weigh atoms and small molecules, but they don’t work for viruses. Do our aspirations for such precise data just fall by the wayside, down the tubes of impossible science?

Not so! Researchers at Georgia Institute of Technology have developed tiny little springs made of carbon nanotubes. Nanotubes are a form of elemental carbon in which all the atoms of carbon are attached to each other in an arrangement that forms a cylindrical tube, just a few Angstroms in diameter. They are just like buckyballs, only tubular.

These form miniature springs when a small voltage is applied to them. By looking at the frequency of oscillation of these miniature springs with high-resolution electron microscopes, the mass of small objects attached to the nanotubes can be inferred down to 1 femtogram. That is about the mass of 50 million carbon atoms.

It is expected that they soon will be using some of the new atom microscopes (the ones that produce all those fancy pictures of atoms in crystals) linked with lasers to measure the oscillation frequencies more precisely and so be able to distinguish viruses just by the measurement of mass.

This is a springboard to a whole new era in virology and cellular biology.

Reference: Science, 283, p. 1513
Reference: New Scientist, March 13, 1999, p. 15

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