Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists moving closer to 'artificial noses'

27.04.2009
More than one nanostring to their bow

These days, chemical analysts are expected to track down even single molecules. To do this highly sensitive detective work, nano researchers have developed minute strings that resonate in characteristic fashion. If a molecule docks onto one of the strings, then it becomes heavier, and its oscillations become measurably slower.

Until recently, however, such "nano-electromechanical systems", or NEMS, have been short of practical applications. Physicists at LMU Munich have now made a breakthrough in this field: They have constructed a system of nanostrings made of non-conducting material, where each string can be electrically excited separately. Thousands of these strings can be produced on a small chip. One of the devices that could be created with this system is a highly sensitive "artificial nose" that detects various molecules – pollutants for example – individually. These new NEMS could also be used in a multitude of other applications – acting as tiny pulse generators in mobile phone clocks, for example.

Quick, certain and cheap detection of single molecules is a task that chemical analysts are now expected to perform. Luckily, there is a method they can employ for this, which uses nanotechnology: Specifically, they use "nano-electromechanical systems", or NEMS. These systems involve strings with diameters of the order of 100 nanometers – a ten-thousandth of a millimeter or a 1/500 of a human hair – which can be excited to resonate in a characteristic fashion. If these strings are coated with the right kind of chemicals, then molecules will dock onto them. More specifically: only one kind of molecule can dock onto each string. When a molecule docks onto a string, the string becomes heavier and its oscillation slows down a tiny bit. "By measuring the period of oscillation, we could therefore detect chemical substances with molecular precision," explains Quirin Unterreithmeier, first author of the study. "Ideally, you would have several thousand strings sitting on a chip the size of a fingernail, each one for highly specifically recognizing a single molecule – so you could build an extremely sensitive 'artificial nose', for example."

Until recently, however, getting such systems to work has proven technically difficult; one problem being to produce and measure the oscillations. While the nanostrings can be made to oscillate by magnetomechanical, piezoelectric or electrothermal excitement, this only works if the nanostrings are made of metal, or are at least metal-coated, which in turn greatly dampens the oscillations, preventing sensitive measurement. That hardly allows the detection of a single molecule. It also makes it harder to distinguish the different signals from differently oscillating strings.

The newly developed method now avoids these difficulties. Quirin Unterreithmeier, Dr. Eva Weig and Professor Jörg Kotthaus of the Center for NanoScience (CeNS), the Faculty of Physics of LMU Munich and the cluster of excellence "Nanosystems Initiative Munich (NIM)" have constructed an NEMS in which the nanostrings are excited individually by dielectric interaction – the same phenomenon that makes hair stand on end in winter. Following this physical principle, the nanostrings, which are made of electrically non-conducting silicon nitride, are excited to resonate when exposed to an oscillating inhomogeneous electric field, and their vibration then measured.

The alternating electric field required for this stimulation was produced between two gold electrodes right up close to the string. The oscillations were measured by two other electrodes. "We created this setup using etching techniques," reports Weig. "But this was easily done – even repeated ten thousand times on a chip. The only thing to do now is to make sure the strings can be individually addressed by a suitable circuit." All in all, this ought to be a technically easy exercise – but one that will allow a breakthrough in chemical analysis. Yet there are even more applications that can be seen beyond this "artificial nose". Among other things, the nanostrings could be employed as the pulse generators in mobile phone clocks, for example. These novel resonators could even be used as ultra-sharp electrical signal filters in metrological systems.

The study is a project of the cluster of excellence "Nanosystems Initiative Munich" (NIM), which has its sights set on developing, researching and bringing into operation functional nanosystems for application in information processing and life sciences. (NIM/suwe)

Publication:
"Universal transduction scheme for nanomechanical systems based on dielectric forces",
Quirin P. Unterreithmeier, Eva M. Weig, Jörg P. Kotthaus
Nature, 23 April 2009
doi:10.1038/nature07932
Contact:
Professor Jörg P. Kotthaus
Faculty of Physics, LMU Munich
Tel.: 089 / 2180 – 3737
E-Mail: kotthaus@cens.de
Dr. Peter Sonntag
Nanosystems Initiative Munich (NIM)
Tel.: 089 / 2180 – 5091
E-Mail: peter.sonntag@lmu.de

Luise Dirscherl | EurekAlert!
Further information:
http://www.lmu.de
http://www.nano-initiative-munich.de/press/press-material

More articles from Life Sciences:

nachricht Scientists enlist engineered protein to battle the MERS virus
22.05.2017 | University of Toronto

nachricht Insight into enzyme's 3-D structure could cut biofuel costs
19.05.2017 | DOE/Los Alamos National Laboratory

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

Im Focus: Hydrogen Bonds Directly Detected for the First Time

For the first time, scientists have succeeded in studying the strength of hydrogen bonds in a single molecule using an atomic force microscope. Researchers from the University of Basel’s Swiss Nanoscience Institute network have reported the results in the journal Science Advances.

Hydrogen is the most common element in the universe and is an integral part of almost all organic compounds. Molecules and sections of macromolecules are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

Media accreditation opens for historic year at European Health Forum Gastein

16.05.2017 | Event News

 
Latest News

New approach to revolutionize the production of molecular hydrogen

22.05.2017 | Materials Sciences

Scientists enlist engineered protein to battle the MERS virus

22.05.2017 | Life Sciences

Experts explain origins of topographic relief on Earth, Mars and Titan

22.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>