At the U.S. Department of Energy lab, they were able to measure variations in the resonant frequency of tiny gold-coated silicon bars just two microns long and fifty nanometers thick by vibrating them with the heat of a solid-state laser at a speed of about two million times a second.
Those variations reflected any extra weight that was loaded onto the bars--in this case, masses as low as 5.5 femtograms could be detected. A femtogram is a billionth of a billionth of a gram, or roughly the mass of 122 gold atoms.
The experiments are among the latest in the field of nanotechnology, which has captured the imagination of the computing industry.involves working with materials at the atomic or molecular level, often with the goal of making products out of components measuring 100 nanometers or less. A nanometer is a billionth of a meter.
By coating the silicon bars with different substances, they can be made to absorb particles of different natures--DNA, proteins, cells or trace amounts of chemical contaminants. This is the basis of an exceptionally sensitive detector for airborne substances: Researcher Panos Datskos expects the technology to be able to detect single molecules in the near future, once the vibration frequency is raised to 50 MHz by fabricating smaller, stiffer bars.
"We can control very precisely the effect of the laser, and not only did we detect this small mass, but we did so under ambient conditions," Datskos told industry publication EE Times. "People can probably do this very easily in a vacuum, but to do it in air and in the presence of friction--because the cantilevers have to displace air to vibrate...friction increases--people have had great difficultly so far trying to achieve that."
Datskos also said that his team was working on a handheld "universal" device that could detect any substance by an array of ten different lengths of sensor. Power consumption would be very low: The most energy-demanding part of the device--the laser--is the same kind as those used in portable CD players.
ZDNet UK's Rupert Goodwins reported from London.