Molecule's Mass Measured Mechanically

Category: Science & Technology
Posted: August 29, 2012 10:48AM
Author: Guest_Jim_*

Mass is a characteristic that is measured fairly often for many reasons, but for some objects, such a measurement is hard to make. Larger objects can be placed on a scale, but smaller objects have to be measured by other means, like mass spectroscopy, but some objects, like proteins, are too complex for mass spectroscopy to work. Researchers at the California Institute of Technology and CEA-LETI in Grenoble, France however have designed a system that can accurately measure the mass of single molecules, one at a time.

The way the researchers achieved this is actually pretty clever. The nanoelectromechanical device has a bridge in it, which the molecule falls on. This bridge is made to vibrate back and forth at specific frequencies and modes. When a molecule falls on the bridge though, it mass and position affects the frequency of the vibration. At first the position had to be known to identify the mass, but now the researchers have found a way to determine the position based on the frequency change of the first and second vibrational modes. (The modes relate to the number of humps to the wave, with the first mode having one hump, the second having two humps, and so on.)

To measure a molecule's mass like this could be very useful for medical tests as a means to identify molecules in samples. We may even see this technology soon as current semiconductor fabrication techniques can be used to manufacture the device.