Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Reach out and touch an oscillator: Cornell researchers find a new way to read nanoscale vibrations

28.03.2007
Nanomechanical oscillators -- tiny strips of vibrating silicon only a few hundred atoms thick -- are the subject of extensive study by nanotechnology researchers. They could someday replace bulky quartz crystals in electronic circuits or be used to detect and identify bacteria and viruses.

The catch is that measuring their vibrations isn't easy. It is usually done by bouncing laser beams off them -- which won't work when the nanodevices become smaller than the wavelength of the light -- or with piezoelectric devices -- those bulky quartz crystals we're trying to get rid of.

An AFM uses a tiny probe that moves slowly just above a surface. Electrostatic attraction or repulsion between the atoms in the tip of the probe and those in the surface causes the probe to move up and down, creating an image of the surface so detailed that individual atoms show up as bumps. Alternatively, the AFM can be used in "tapping mode," literally bouncing off the surface.

"AFMs are all over the place," said Rob Ilic, research associate in the Cornell NanoScale Facility and lead author on a paper about the research published Feb. 23 in the online edition of the Journal of Applied Physics. "So this offers a simple way to study these structures." (Cornell, for example, has at least a dozen AFMs in various labs.) Moreover, he said, probes similar to those in an AFM can be built directly into nanofabricated devices.

This would amount to using MEMS to measure NEMS, he said. MEMS (microelectromechanical systems) are machines with moving parts measured in microns, or millionths of a meter; NEMS (nanoelectromechanical systems) are measured in nanometers, or billionths of a meter. A nanometer is about the length of three atoms in a row. When the NEMS oscillator is too small to be observed by laser light, it could still be coupled to a MEMS probe that in turn would be large enough for a laser readout.

To measure the vibration of a nanomechanical oscillator, the AFM probe moves along the length of the oscillating rod. The result is a complex bouncing interaction between the probe and the oscillator -- imagine shaking one end of a spring and watching the vibrations at the other end -- from which the frequency of vibration of the oscillator can be determined mathematically.

For the experiments just reported, Ilic and colleagues manufactured a wide variety of silicon cantilevers -- strips of silicon attached at one end with the other free to vibrate -- from 5 to 12 microns long, 1/2 to 1 micron wide and about 250 nanometers thick, which had natural vibration frequencies from 1 to 15 Mhz. The cantilevers were set into vibration by a piezoelectric device.

The experimenters first measured the resonant frequencies of the cantilevers by focusing laser beams on them and observing deflection of the reflected light, then scanned each cantilever with the AFM probe, both in tapping mode and with the probe just above the surface. They found the AFM measurements in good agreement with laser measurements, although the AFM readouts had a somewhat lower "quality factor," because the oscillator and probe were interacting. This would make the method somewhat less precise in mass detection.

Nanomechanical oscillators are often cited as potential tools for detecting bacteria, viruses or other organic molecules. An array of tiny cantilevers might be created with antibodies to many different pathogens attached to them. An experimental solution could then be washed over the array, allowing microbes to bind to the cantilevers with matching antibodies. Since the cantilevers are so tiny, an attached bacterium or virus represents a significant change in mass, which changes the frequency at which the oscillator will vibrate.

In a practical device, a MEMS probe could be mounted above each NEMS oscillator to read out which oscillators in the array show a change in frequency -- and thus identify which pathogens are present.

Press Relations Office | EurekAlert!
Further information:
http://www.cornell.edu

More articles from Physics and Astronomy:

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

nachricht Protecting the power grid: Advanced plasma switch for more efficient transmission
17.08.2018 | DOE/Princeton Plasma Physics Laboratory

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: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>