Mass spectrometry analyses molecules on the basis of the mass-to-charge ratios of their ionic fragments. The method can be difficult to use for substances that are hard to ionize or only available in minute amounts. Michael Roukes and his colleagues at the California Institute of Technology in Pasadena now demonstrate a nanoelectromechanical device that can directly measure the mass of individual molecules.
Inside the device, a tiny suspended beam vibrates at high frequency and acts as a sensor. The authors blasted the device first with gold nanoparticles, and later with bovine serum albumin.
When molecules stick to the sensor's surface, they drastically lower its vibrational frequency. By measuring the change, the mass of individual molecules can be established, the authors say, and this could potentially be done without the use of ionization.