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Statistical noise characterized in interactions of atoms with nanomachines

As nanotechnology progresses in manipulating individual molecules and atoms, it becomes increasingly important to understand in detail the interactions of miniature machines and individual atoms. As an extension of previous work developing a miniature machine capable of measuring the mass of individual molecules, the interactions of xenon atoms with a nanoelectromechanical system (NEMS) have now been measured to characterize the statistical noise caused by atomic fluctuations in this NEMS device. Physorg.com points to this Caltech feature written by Marcus Woo “Bring in the (nano) noise“:

At the forefront of nanotechnology, researchers design miniature machines to do big jobs, from treating diseases to harnessing sunlight for energy. But as they push the limits of this technology, devices are becoming so small and sensitive that the behavior of individual atoms starts to get in the way. Now Caltech researchers have, for the first time, measured and characterized these atomic fluctuations—which cause statistical noise—in a nanoscale device.

Physicist Michael Roukes and his colleagues specialize in building devices called nanoelectromechanical systems—NEMS for short—which have a myriad of applications. For example, by detecting the presence of proteins that are markers of disease, the devices can serve as cheap and portable diagnostic tools—useful for keeping people healthy in poor and rural parts of the world. Similar gadgets can measure toxic gases in an enclosed room, providing a warning for the inhabitants.

Two years ago, Roukes’s group created the world’s first nanomechanical mass spectrometer, enabling the researchers to measure the mass of a single biological molecule. The device, a resonator that resembles a tiny bridge, consists of a thin strip of material 2 microns long and 100 nanometers wide that vibrates at a resonant frequency of several hundred megahertz. When an atom is placed on the bridge, the frequency shifts in proportion to the atom’s mass.

But with increasingly sensitive devices, the random motions of the atoms come into play, generating statistical noise. “It’s like fog or smoke that obscures what you’re trying to measure,” says Roukes, who’s a professor of physics, applied physics, and bioengineering. In order to distinguish signal from noise, researchers have to understand what’s causing the ruckus.

So Roukes—along with former graduate student and staff scientist Philip X. L. Feng, former graduate student Ya-Tang (Jack) Yang, and former postdoc Carlo Callegari—set out to measure this noise in a NEMS resonator. They described their results in the April issue of the journal Nano Letters [abstract]. …

The full text of the research article is available as a PDF at Michael Roukes’s web site. The Roukes group is part of

…the Alliance for Nanosystems VLSI, a close and enthusiastic collaboration with scientists and engineers at CEA/LETI-MINATEC in Grenoble, France. Together we have already demonstrated the first examples of very-large-scale integration (VLSI) of nanoelectromechanical systems. Our current work is focused on highly-multiplexed bio/chemical detection systems, producible en masse to enable both new commercializable applications and fundamental explorations at the frontiers of the life sciences.

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