According to Michael Roukes, professor of physics, applied physics, and bioengineering at Caltech and the founding director of Caltech's Kavli Nanoscience Institute, the technology his group has announced this week shows the immense potential of nanotechnology for creating transformational new instrumentation for the medical and life sciences. The new devices are at the nanoscale, he explains, since their principal component is significantly less than a millionth of a meter in width.
The Caltech devices are "nanoelectromechanical resonators"--essentially tiny tuning forks about a micron in length and a hundred or so nanometers wide that have a very specific frequency at which they vibrate when excited. Just as a bronze bell rings at a certain frequency based on its size, shape, and composition, these tiny tuning forks ring at their own fundamental frequency of mechanical vibration, although at such a high pitch that the "notes" are nearly as high in frequency as microwaves.
The researchers set up electronic circuitry to continually excite and monitor the frequency of the vibrating bar. Intermittently, a shutter is opened to expose the nanodevice to an atomic or molecular beam, in this case a very fine "spray" of xenon atoms or nitrogen molecules. Because the nanodevice is cooled, the molecules condense on the bar and add their mass to it, thereby lowering its frequency. In other words, the mechanical vibrations of the now slightly-more-massive nanodevice become slightly lower in frequency--just as thicker, heavier strings on an instrument sound notes that are lower than lighter ones.
Because frequency can be measured so precis