Tag Archives: NEMS

Identifying performance problems in nanoresonators

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Use of nanoelectromechanical systems (NEMS) can now be maximised due to a technique developed by researchers at the Commissariat a l’Energie Atomique (CEA) and the University of Grenoble-Alpes (France). From a March 7, 2016 news item on ScienceDaily,

A joint CEA / University of Grenoble-Alpes research team, together with their international partners, have developed a diagnostic technique capable of identifying performance problems in nanoresonators, a type of nanodetector used in research and industry. These nanoelectromechanical systems, or NEMS, have never been used to their maximum capabilities. The detection limits observed in practice have always been well below the theoretical limit and, until now, this difference has remained unexplained. Using a totally new approach, the researchers have now succeeded in evaluating and explaining this phenomenon. Their results, described in the February 29 [2016] issue of Nature Nanotechnology, should now make it possible to find ways of overcoming this performance shortfall.

A Feb. 29, 2016 CEA press release, which originated the news item, provides more detail about NEMS and about the new technique,

NEMS have many applications, including the measurement of mass or force. Like a tiny violin string, a nanoresonator vibrates at a precise resonant frequency. This frequency changes if gas molecules or biological particles settle on the nanoresonator surface. This change in frequency can then be used to detect or identify the substance, enabling a medical diagnosis, for example. The extremely small dimensions of these devices (less than one millionth of a meter) make the detectors highly sensitive.

However, this resolution is constrained by a detection limit. Background noise is present in addition to the wanted measurement signal. Researchers have always considered this background noise to be an intrinsic characteristic of these systems (see Figure 2 [not reproduced here]). Despite the noise levels being significantly greater than predicted by theory, the impossibility of understanding the underlying phenomena has, until now, led the research community to ignore them.

The CEA-Leti research team and their partners reviewed all the frequency stability measurements in the literature, and identified a difference of several orders of magnitude between the accepted theoretical limits and experimental measurements.

In addition to evaluating this shortfall, the researchers also developed a diagnostic technique that could be applied to each individual nanoresonator, using their own high-purity monocrystalline silicon resonators to investigate the problem.

The resonant frequency of a nanoresonator is determined by the geometry of the resonator and the type of material used in its manufacture. It is therefore theoretically fixed. By forcing the resonator to vibrate at defined frequencies close to the resonant frequency, the CEA-Leti researchers have been able to demonstrate a secondary effect that interferes with the resolution of the system and its detection limit in addition to the background noise. This effect causes slight variations in the resonant frequency. These fluctuations in the resonant frequency result from the extreme sensitivity of these systems. While capable of detecting tiny changes in mass and force, they are also very sensitive to minute variations in temperature and the movements of molecules on their surface. At the nano scale, these parameters cannot be ignored as they impose a significant limit on the performance of nanoresonators. For example, a tiny change in temperature can change the parameters of the device material, and hence its frequency. These variations can be rapid and random.

The experimental technique developed by the team makes it possible to evaluate the loss of resolution and to determine whether it is caused by the intrinsic limits of the system or by a secondary fluctuation that can therefore by corrected. A patent has been applied for covering this technique. The research team has also shown that none of the theoretical hypotheses so far advanced to explain these fluctuations in the resonant frequency can currently explain the observed level of variation.

The research team will therefore continue experimental work to explore the physical origin of these fluctuations, with the aim of achieving a significant improvement in the performance of nanoresonators.

The Swiss Federal Institute of Technology in Lausanne, the Indian Institute of Science in Bangalore, and the California Institute of Technology (USA) have also participated in this study. The authors have received funding from the Leti Carnot Institute (NEMS-MS project) and the European Union (ERC Consolidator Grant – Enlightened project).

Here’s a link to and a citation for the paper,

Frequency fluctuations in silicon nanoresonators by Marc Sansa, Eric Sage, Elizabeth C. Bullard, Marc Gély, Thomas Alava, Eric Colinet, Akshay K. Naik, Luis Guillermo Villanueva, Laurent Duraffourg, Michael L. Roukes, Guillaume Jourdan & Sébastien Hentz. Nature Nanotechnology (2016) doi:10.1038/nnano.2016.19 Published online 29 February 2016

This paper is behind a paywall.

World’s* smallest FM radio transmitter made out of graphene

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I’m always amazed at how often nanotechnology is paired with radio. The latest ‘nanoradio’ innovation is from the University of Columbia School of Engineering. According to a November 18, 2013 news item on ScienceDaily,

 A team of Columbia Engineering researchers, led by Mechanical Engineering Professor James Hone and Electrical Engineering Professor Kenneth Shepard, has taken advantage of graphene’s special properties — its mechanical strength and electrical conduction — and created a nano-mechanical system that can create FM signals, in effect the world’s smallest FM radio transmitter.

One of my first ‘nanorado’ stories (in 2007 and predating the existence of this blog) focused on carbon nanotubes and a Zettl Group (Alex Zettl) project at the University of California at Berkeley (from the Zettl Group’s Nanotube Radio: Supplementary materials webpage),

We have constructed a fully functional, fully integrated radio receiver, orders-of-magnitude smaller than any previous radio, from a single carbon nanotube. The single nanotube serves, at once, as all major components of a radio: antenna, tuner, amplifier, and demodulator. Moreover, the antenna and tuner are implemented in a radically different manner than traditional radios, receiving signals via high frequency mechanical vibrations of the nanotube rather than through traditional electrical means. We have already used the nanotube radio to receive and play music from FM radio transmissions such as Layla by Eric Clapton (Derek and the Dominos) and the Beach Boy’s Good Vibrations. The nanotube radio’s extremely small size could enable radical new applications such as radio controlled devices small enough to exist in the human bloodstream, or simply smaller, cheaper, and more efficient wireless devices such as cellular phones.

The group features four songs transmitted via their carbon nanotube radio (from the ‘supplementary materials’ webpage),

A high resolution transmission electron microscope allows us to observe the nanotube radio in action. We have recorded four videos from the electron microscope of the nanotube radio playing four different songs. At the beginning of each video, the nanotube radio is tuned to a different frequency than that of the transmitted radio signal. Thus, the nanotube does not vibrate, and only static noise can be heard. As the radio is brought into tune with the transmitted signal, the nanotube begins to vibrate, which blurs its image in the video, and at the same time, the music becomes audible. The four songs are Good Vibrations by the Beach Boys, Largo from the opera Xerxes by Handel (this was the first song ever transmitted using radio), Layla by Eric Clapton (Derek & the Dominos), and the Main Title from Star Wars by John Williams.

Good Vibrations (Quicktime, 8.06 MB)
Layla (Quicktime, 6.13 MB)
Largo (Quicktime, 8.73 MB)
Star Wars (Quicktime, 8.68 MB)

‘Layla’ is quite scrtachy and barely audible but it is there, if you care to listen to this 2007 carbon nanotube radio project. Now in 2013 we have a graphene radio receiver and this graphene radio project is intended to achieve some of the goals as the carbon nanotube radio project,. From the Nov. 17, 2013 University of Columbia news release on newswise and also on EurekAlert),

“This work is significant in that it demonstrates an application of graphene that cannot be achieved using conventional materials,” Hone says. “And it’s an important first step in advancing wireless signal processing and designing ultrathin, efficient cell phones. Our devices are much smaller than any other sources of radio signals, and can be put on the same chip that’s used for data processing.”

Graphene, a single atomic layer of carbon, is the strongest material known to man, and also has electrical properties superior to the silicon used to make the chips found in modern electronics. The combination of these properties makes graphene an ideal material for nanoelectromechanical systems (NEMS), which are scaled-down versions of the microelectromechanical systems (MEMS) used widely for sensing of vibration and acceleration. For example, Hone explains, MEMS sensors figure out how your smartphone or tablet is tilted to rotate the screen.

In this new study, the team took advantage of graphene’s mechanical ‘stretchability’ to tune the output frequency of their custom oscillator, creating a nanomechanical version of an electronic component known as a voltage controlled oscillator (VCO). With a VCO, explains Hone, it is easy to generate a frequency-modulated (FM) signal, exactly what is used for FM radio broadcasting. The team built a graphene NEMS whose frequency was about 100 megahertz, which lies right in the middle of the FM radio band (87.7 to 108 MHz). They used low-frequency musical signals (both pure tones and songs from an iPhone) to modulate the 100 MHz carrier signal from the graphene, and then retrieved the musical signals again using an ordinary FM radio receiver.

“This device is by far the smallest system that can create such FM signals,” says Hone.

While graphene NEMS will not be used to replace conventional radio transmitters, they have many applications in wireless signal processing. Explains Shepard, “Due to the continuous shrinking of electrical circuits known as ‘Moore’s Law’, today’s cell phones have more computing power than systems that used to occupy entire rooms. However, some types of devices, particularly those involved in creating and processing radio-frequency signals, are much harder to miniaturize. These ‘off-chip’ components take up a lot of space and electrical power. In addition, most of these components cannot be easily tuned in frequency, requiring multiple copies to cover the range of frequencies used for wireless communication.”

…

Unfortunately I haven’t seen any audio files for this ‘graphene radio’ but here’s a link to and a citation for the 2013 paper ,

Graphene mechanical oscillators with tunable frequency by Changyao Chen, Sunwoo Lee, Vikram V. Deshpande, Gwan-Hyoung Lee, Michael Lekas, Kenneth Shepard, & James Hone. Nature Nanotechnology (2013) doi:10.1038/nnano.2013.232 Published online 17 November 2013

The paper is behind a paywall.

* ‘Wolrd’s’ in headline corrected to ‘World’s’ on July 29, 2015.

Back to my roots, writing nanotechnology

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This July 18, 2011 news item title, Writing Nanostructures: Heated AFM Tip Allows Direct Fabrication of Ferroelectric Nanostructures On Plastic, on the Science Daily website brought back memories. The first part of the title, Writing Nanostructures, that is. My first project about nanotechnology and the language used to describe it for my master’s degree was titled, Writing Nanotechnology.

This, of course, is something entirely different. From the news item on Science Daily,

Using a technique known as thermochemical nanolithography (TCNL), researchers have developed a new way to fabricate nanometer-scale ferroelectric structures directly on flexible plastic substrates that would be unable to withstand the processing temperatures normally required to create such nanostructures.

The technique, which uses a heated atomic force microscope (AFM) tip to produce patterns, could facilitate high-density, low-cost production of complex ferroelectric structures for energy harvesting arrays, sensors and actuators in nano-electromechanical systems (NEMS) and micro-electromechanical systems (MEMS). The research was reported July 15 in the journal Advanced Materials.

“We can directly create piezoelectric materials of the shape we want, where we want them, on flexible substrates for use in energy harvesting and other applications,” said Nazanin Bassiri-Gharb, co-author of the paper and an assistant professor in the School of Mechanical Engineering at the Georgia Institute of Technology.

I particularly like this picture where the professor is holding something that looks like a pencil as a pointer,

Georgia Tech postdoctoral fellow Suenne Kim holds a sample of flexible polyimide substrate used in research on a new technique for producing ferroelectric nanostructures. Assistant professor Nazanin Bassiri-Gharb points to a feature on the material, while graduate research assistant Yaser Bastani observes. (Credit: Gary Meek)

You can check out the rest  in the Science Daily news item or you can check out the original Georgia Institute of Technology news release (which has more images) written by John Toon.

 

Nano oscillation and music

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It’s one of those breakthroughs that sounds exciting but is a little hard to understand if you’re not working in that field … still … Scientists at the National Institute of Nanotechnology in Canada have solved a problem that was preventing more widespread application of nano-electro-mechanical systems (NEMS). They’ve developed a technique to control vibration/oscillation that could be compared to ‘unringing a bell’. The ability to stop the vibration of a nano cantilever in less than a nanosecond opens up new possibilities in information and communications technology (ICT) and other fields.  There’s a more detailed article about the work here at Nanotech Wire or here at Nanowerk. The research is described in the Nov. 2, 2008 online Nature Nanotechnology article, “Time-domain control of ultrahigh-frequency nanomechanical systems,” the abstract is here. The article itself is behind a paywall.

Chinese researchers are investigating ways to exploit the acoustic properties of carbon nanotubes which are usually lauded for their strength and their electrical properties. Shoushan Fan and colleagues from Tsinghua University in Beijing and Beijing Normal University created sheets of carbon nanotubes and sent audio frequency currents through them as if they were music speakers. However, unlike a standard speaker which creates sound by emitting a vibration, the scientists did not detect any vibrations from the ‘carbon nanotube’ speakers. The researchers believe that the carbon nanotube speakers work as thermoacoustic devices using temperature and pressure oscillation in the surrounding air to emit sound. For more including a video clip of the carbon nanotube speakers in action and a brief mention of 19th century thermoacoustic devices, go here.

One more reminder about Visible Verse, the video poetry event on November 6, 2008 at Pacific Cinematheque (1131 Howe St., Vancouver) at 7:30 pm. Tickets and more info. here.