Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sharply-tuned nanostrings work at room temperature

14.07.2006
Using a fast, low-cost fabrication technique that allows inexpensive testing of a wide variety of materials, Cornell researchers have come up with nanoscale resonators -- tiny vibrating strings -- with the highest quality factor so far obtainable at room temperature for devices so small.

The work is another step toward "laboratory on a chip" applications in which vibrating strings can be used to detect and identify biological molecules. The devices also can be used as very precisely tuned oscillators in radio-frequency circuits, replacing relatively bulky quartz crystals.

When you strike a bell or pluck a guitar string, it will vibrate within a small range of frequencies, centering on what is called the resonant frequency. Quality factor, or Q, refers to how narrow that range will be. It is defined as the ratio of the resonant frequency to the range of frequencies over which resonance occurs. A radio receiver with high-Q circuitry, for example, will be more selective in separating one station from another.

Cornell researchers have already used vibrating strings and cantilevers to detect masses as small as a single bacterium or virus. Resonant frequency depends on the mass of a vibrating object (a thick guitar string has a lower pitch than a thin one). If a nanoscale vibrator is coated with antibodies that cause a virus or some other molecule to adhere to it, the change in mass causes a measurable change in frequency. In a high Q nanostring, the researchers say, a small change in mass will produce a much more noticeable shift.

The new nanostrings, made by graduate student Scott Verbridge and colleagues in the laboratories of Harold Craighead, Cornell professor of applied and engineering physics, and Jeevak Parpia, professor of physics, are made of silicon nitride under stress. By controlling the temperature, pressure and other factors as the film is deposited, the experimenters can cause the silicon nitride to be, in effect, stretched.

The longest string the researchers made was 200 nanometers (nm) wide, 105 nm thick and 60 microns long and had a resonant frequency of 4.5 megaHertz with a quality factor of 207,000. (A nanometer is one-billionth of a meter, about as long as three atoms in a row; a micron, or micrometer, is one-millionth of a meter.) Comparing the results with those reported by other workers in the field, Verbridge said others have reached similar Q factors in samples cooled to within a few degrees of absolute zero, but he believes this is the highest Q achieved at room temperature.

To demonstrate the possible applications in electronics, Verbridge's colleague, graduate student Robert Reichenbach, has built what he calls "the world's most expensive radio," using about $200,000 worth of lab equipment to mix the vibration of a nanoscale resonator with the off-the-air signal from local radio station WICB and read the output with a laser. The quartz crystals ordinarily used in radios are about one-half-inch square and require relatively large batteries to operate, Reichenbach said. The replacement is about the size of a human hair and requires little power. Radio transmitters using such devices could be made small enough to implant in the body to report on medical conditions, and cell phones could shrink to wristwatch size or smaller, he said.

In addition to having a high quality factor, the stressed silicon nitride strings are very robust mechanically, the researchers said, making them practical for consumer devices.

The research is described in a paper, "High Quality Factor Resonance at Room Temperature With Nanostrings Under High Tensile-Stress," in the June 15 issue of the Journal of Applied Physics.

Fabrication by electrospinning

Cornell is famous for its interdisciplinary collaborations, but workers in the Craighead Research Group may hold a record for the most unlikely combination, using tools from the Department of Textiles and Apparel to advance nanotechnology.

At the Cornell NanoScale Facility, the smallest devices are usually made by a process called electron beam lithography: A sharply focused beam of electrons cuts a pattern into a chemical film covering a wafer of silicon or a similar substance. The wafer is then etched with acid that cuts away the silicon in the places the resist has been removed,

As an alternative way of making simple straight lines, researchers turned to electrospinning, in which a liquid polymer is forced through a row of openings just a few nanometers in diameter, creating very fine fibers. Textiles and apparel researchers have been using electrospinning to create a sort of fabric by letting the fibers collect and mat up. The nanotech researchers allow them to flow smoothly onto a moving silicon wafer, creating a series of parallel lines that act as a chemical resist and guide an etchant to carve out nanostrings.

The process is faster and much cheaper than electron-beam lithography, and it allows researchers to test a wide variety of materials and configurations in a short time and on a low budget.

"Given the substrate, I can make you a nanobeam resonator in under an hour," said graduate student Scott Verbridge.

Bill Steele | EurekAlert!
Further information:
http://www.cornell.edu

More articles from Physics and Astronomy:

nachricht CCNY physicists master unexplored electron property
26.07.2017 | City College of New York

nachricht Large, distant comets more common than previously thought
26.07.2017 | University of Maryland

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

CCNY physicists master unexplored electron property

26.07.2017 | Physics and Astronomy

Molecular microscopy illuminates molecular motor motion

26.07.2017 | Life Sciences

Large-Mouthed Fish Was Top Predator After Mass Extinction

26.07.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>