Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


To see the message, just add noise


USC nanotube device uses ’Stochastic Resonance’ to enhance subthreshold signals

Stochastic resonant image of nanotube, with progressively more noise added

Paradoxical as it seems, a team of University of Southern California researchers has built a signal detector that only works when noise is added.

The device uses a novel kind of transistor made from carbon nanotubes. The principal investigator, Professor Bart Kosko of the USC department of electrical engineering, claims that the series of experiments reported in the December issue of the American Chemical Society’s Nano Letters, says the result is significant both in the development of electronic applications for nanotubes, and in the development of applications for "stochastic resonance," the counterintuitive use of noise to amplify signals.

The basic idea of stochastic resonance detection, says Kosko, is to create devices with strict threshold effects, that only respond to signals of more than a certain amplitude -- and then set this threshold around, or even below the amplitude
of the signal expected.

In the sub threshold form, "In a quiet, noise-free environment," said the scientist, "the detectors will not receive a signal." But if a moderate amount of noise is present, the signal will, as it were, float on top of the noise, triggering the detectors."

Kosko, who earlier published a theorem setting forth the mathematical basis for the phenomenon, says that the experiments made with the novel carbon nanotube detectors reported in the new paper confirm his predictions.

Carbon nanotubes are minute pipes made of graphite, the form of carbon familiar in pencil lead. Carbon atoms in graphite naturally organize themselves into two-dimensional sheets or lattices in a chicken wire or beehive like hexagonal lattice. Modern fabrication techniques can roll up such sheets into ultra thin tubes 100,000 times smaller than a human hair -- less than 2 nanometers in diameter.

Twisting such tubes can drastically change their electronic properties, from conductors, to semiconductors. A main focus of interest now is their use in flat panel displays.

The experiment used semiconductor nanotubes two nanometers in diameter and 3,000-5000 nanometers long created by Chongwu Zhou, also of the department of electrical engineering, configured to perform as a simple transistor set to detect an electronic signal.

The signal to be detected, however, was deliberately set well below this critical minimum, so that, in silent conditions, no signal at all was received.

But when the experimenters added noise -- random electrical activity -- generated by several alternate methods, the signal came through. Too much added noise wiped it out. But at moderate levels previously undetectable signals would come through.

Kosko has earlier created illustrations of the principle. " Each pixel acts as a separate threshold unit or neuron (or nanotube transistor)," he said.

"We start off by throwing away a great deal of the image’s structure and then add noise from there."

The noise makes the fragmentary picture suddenly recognizable. (See illustration).

Kosko has been studying stochastic resonant effects -- how noise can in some circumstances bring out otherwise hidden patterns -- for years, building on work done for the most part in biology. Researchers have discovered that, for example, random Brownian movement stimulation of the cochlear sensors frog ears increases their sensitivity.

Kosko believes that increased awareness of the stochastic resonance phenomenon can aid designers of communications, including especially modern spread-spectrum devices, which often rely on an array of faint signals.

"Nano-device designers can individually tailors nanotubes to specific signals and then deploy them in numbers -- rather like pipe organs tuned to different notes -- to take advantage of the SR-effects, " he said.

In addition to Zhou, the paper was also co-authored by USC graduate students Ian Y. Lee and Anile Liu. The National Science Foundation provided funding for the research

Bob Calverley | EurekAlert!
Further information:

More articles from Power and Electrical Engineering:

nachricht Neutrons pave the way to accelerated production of lithium-ion cells
20.03.2018 | Technische Universität München

nachricht Monocrystalline silicon thin film for cost-cutting solar cells with 10-times faster growth rate fabricated
16.03.2018 | Tokyo Institute of Technology

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>