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World Smallest Optical Cavities Lead to Most Intense Nanolaser Beams

Metamaterials can produce astounding effects. They possess quite different electromagnetic properties from conventional materials that allow them—among other things—to make objects appear invisible. Physics as magic, if you will.

If you manipulate the structure of a metamaterial, it will change how it interacts with electromagnetic waves. Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have taken advantage of this phenomenon at the nanoscale to create “the world’s smallest three-dimensional optical cavities with the potential to generate the world’s most intense nanolaser beams.” 

The development of the “world’s smallest optical cavities” should have applications across a number of optical fields, including LEDs, optical sensing, nonlinear optics, quantum optics and photonic integrated circuits. It seems that metamaterials are on a bit of a roll when it comes to optoelectronics applications as evidenced by research coming out of the UK and Spain earlier this year.

Key to this technology’s operation is the optical property known as negative refraction, which makes it possible for some kinds of metamaterials to bend light in the opposite direction from what we would expect based on typical refraction. Achieving this negative refraction involves reversing the electrical component (permittivity) and the magnetic component (permeability) of a material’s refractive index. This is accomplished by constructing the material so that it has structures with dimensions smaller than the wavelengths of the light it is intended to refract.

“Due to the unnaturally high refractive index supported in the metamaterials, our 3D cavities can be smaller than one tenth of the optical wavelength,” says Xiaodong Yang, lead author of the Nature Photonics paper,  in a Berkeley Lab press release. “At these nanoscale dimensions, optical cavities compress the optical mode into a tiny space, increasing the photon density of states and thereby enhancing the interactions between light and matter.”

Xiang Zhang, a principal investigator with Berkeley Lab’s Materials Sciences Division and director of UC Berkeley’s Nano-scale Science and Engineering Center (SINAM), believes this research should make possible a new generation of high-performance photonic devices.

“Our work opens up a new approach for designing a truly nano-scale optical cavity,” Zhang says in the Berkeley Lab press release. “By using metamaterials, we show intriguing cavity physics that counters conventional wisdom. For example, the quality factor of our optical mode rapidly increases with the decrease of cavity size. The results of this study provide us with a tremendous opportunity to develop high performance photonic devices for communications.”

Carbon Nanotube-enabled ‘Strain Paint’ Could Replace Strain Gauges


Rice University appears committed to the development of the carbon nanotube (CNT). Ever since its chemistry professor Richard Smalley spun out his research with CNTs into the start-up Carbon Nanotechnologies Inc. (CNI), the university has been inextricably tied to CNTs.

CNI eventually merged with Unidym to create a “nano blockbuster” in 2007,and then it went belly up in 2009. But CNI’s demise had been written on the wall long before that. 

The cautionary tale of CNI is not a knock against the use of carbon nanotubes in commercial applications, but simply a reminder that market pull needs to be more critical to a company’s story than IP position or Nobel Prizes

So, it was pleasing to see that Rice University researchers have not abandoned commercial aspirations for CNTs but instead re-focused their commercial strategies. They have developed a polymeric varnish infused with CNTs that when painted on a surface can act as a strain sensor. The researchers, who have dubbed their material “strain paint,” believe that its early applications could include structures such as airplane wings.

After the “strain paint” has been applied to the surface of a structure and allowed to cure, it is then possible to excite the CNTs that are in the film by focusing a laser beam on the paint. The excited CNTs fluoresce in a way that indicates the amount of strain. More about the research, which was initially published in the American Chemical Society journal Nano Letters, can be found in the video below.


“For an airplane, technicians typically apply conventional strain gauges at specific locations on the wing and subject it to force vibration testing to see how it behaves,” says Satish Nagarajaiah, a Rice professor of civil and environmental engineering and of mechanical engineering and materials science, in a Rice University press release. “They can only do this on the ground and can only measure part of a wing in specific directions and locations where the strain gauges are wired. But with our non-contact technique, they could aim the laser at any point on the wing and get a strain map along any direction,” says Nagarajaiah.

According to Rice chemistry professor Bruce Weisman, some reproducibility and long-term stability of the spectral shifts need to be ironed out before market considerations can be fully explored. “We’ll need to optimize details of its composition and preparation, and find the best way to apply it to the surfaces that will be monitored,” says Weisman in the same press release. “These fabrication/engineering issues should be addressed to ensure proper performance, even before we start working on portable read-out instruments.”

What I like best about the story covering this technology is the final quote from Weisman: “I’m confident that if there were a market, the readout equipment could be miniaturized and packaged. It’s not science fiction.” Exactly.

A123 Introduces New Battery Technology Amid Recent Financial Troubles


You have to hand it to A123 Systems. After experiencing an embarrassing and costly manufacturing snafu this past March that required a recall costing the company US $55 million, then having to report a first quarter loss of $125 million in May, one might have expected the company to retrench in order to sort out how its revenues last quarter had decreased by 40 percent from the same quarter in 2011. But A123 didn’t do that. Instead the company announced an update to its Nanophosphate® lithium iron phosphate battery technology.

This would be an understandable approach to managing dwindling fortunes, especially if the company had suddenly devised a Li-ion battery that could compete head to head with internal combustion engines. As U.S. Energy Secretary Steven Chu once declared, "a rechargeable battery that can last for 5000 deep discharges, [and offer] 6 or 7 times as much storage capacity (3.6 Mj/kg = 1,000 Wh) at [one-third of today's costs] will be competitive with internal combustion engines (400-500 mile range).”  A press release proclaiming that would certainly change the conversation and forever alter the company's market fortunes.

However, we didn’t get that. Instead, we got A123's same battery technology, but updated so that it can operate at extreme temperatures. "We believe Nanophosphate EXT is a game-changing breakthrough that overcomes one of the key limitations of lead acid, standard lithium-ion, and other advanced batteries. By delivering high power, energy, and cycle life capabilities over a wider temperature range, we believe Nanophosphate EXT can reduce or even eliminate the need for costly thermal management systems, which we expect will dramatically enhance the business case for deploying A123's lithium ion battery solutions for a significant number of applications," said David Vieau, the company's CEO, in a press release.

Will removing or just reducing the need for cooling systems be a game changer for both the transportation and telecommunications markets? Both applications will certainly benefit, but I imagine it will make more of a difference in the telecommunications market, where it will be used to power cell tower sites built off-grid or in regions with unstable power. After all, it’s hard to see how this brings Li-ion battery technology any closer to propelling a car for 800 kilometers on a single charge while lowering the price of the battery system by a factor of three. I am not sure this changes the conversation, never mind the game.



“Plastic Paint” Magnetic Field Sensor Based on Spintronics Takes Aim at Consumer Electronics


Ever since researchers discovered that magnetic field sensors could be produced on organic thin-film materials, there has been the hope the discovery would lead to inexpensive sensors on flexible substrates. If you could get it right, there was huge potential simply due to the ubiquity of magnetic field sensors in consumer electronics.

There were just a couple of rather large problems. A very narrow magnetic field range limited these sensors usefulness and they required continuous calibration to compensate for changes in temperature and the degradation of the material.

Now researchers at the University of Utah have developed a “spintronic” organic thin-film semiconductor that serves as an inexpensive magnetic field sensor capable of detecting intermediate to strong magnetic fields and never needs to be calibrated.

The magnetic sensing film, which is described in the June 12th edition of the journal Nature Communications,  also resists heat and degradation and operates at room temperatures. The thin film is an organic semiconductor polymer called MEH-PPV.

Christoph Boehme, Associate Professor at the University of Utah, and one of the named authors of the Nature paper, describes the thin film in the Institute of Physics’ website story linked to above as an orange-colored "electrically conducting, magnetic field-sensing plastic paint that is dirt cheap. We measure magnetic fields highly accurately with a drop of plastic paint, which costs just as little as drop of regular paint."

The researchers are so enthusiastic about their discovery that they are considering launching a spinoff company to commercialize the technology. The commercial applications for magnetic-field sensors are quite broad, so let’s hope the scientists get some good business advice on which application space to target their technology. Further, they should refrain from three-year projections to having devices on the market, managing investors’ expectations is often the key to success.

Does the Effect of Nanoparticles on Amino Acids Translate into a Risk for Consumers?

I am sure for the next few days—if not weeks and even years—research out of Trinity College Dublin will be portrayed in the press and among some NGOs as "nanotechnology causes arthritis."

Unfortunately, the story of the research—which was published in the journal Nanomedicine— is a bit more complicated than that and the details will likely get lost in the furor that the initial headlines will generate. Basically, the researchers examined whether proteins when exposed to certain nanoparticles can change the amino acid arginine into the amino acid citrulline. This process known as post-translational citrullination of proteins has been linked to autoimmune diseases like rheumatoid arthritis.

So maybe to avoid some confusion, it might be best to say from the outset that this research does not establish the risk of nanoparticles but only their potential hazard under very controlled (but unusual) circumstances. Further, despite what the press release may claim, I don’t see how they have established much in the way of safety implications for the “use and ultimate disposal of nanotechnology products and materials.”

Whenever I see a story about nanoparticles and toxicity, I immediately drag out my formula for understanding risk: Hazard x Exposure = Risk. When you consider that the researchers did not expose human cells from the lining of the airway passages to a freshly minted carbon nanotube bicycle, you start to wonder how they have established that “nanotechnology products” are a threat to our safety. They have established that some free-floating nanoparticles effect a change in proteins, but— apart from the pollution we have been exposed to since automobiles  with carbon black tires first started driving on pavement— how often are we exposed to free-floating nanoparticles or deliberately manufactured nanoparticles like carbon nanotubes?

For me this raises the more vexing concern of when we’ll eventually see more research on how long it would take for the carbon nanotubes to be released from the material matrix of a “nanotechnology product”—like a carbon fiber bicycle—so that they could cause the kind of hazard the researchers from Trinity College have described.

While a carbon nanotube or some other nanoparticles “facilitating post-translational citrullination of proteins” is no doubt a serious concern, it sort of pales in comparison to say hydrofluoric acid, which on its own can kill you depending on your exposure but as an ingredient among others can formulate the drug Prozac. Go figure.  Again, what we need to start seeing more of in nanoparticle toxicology research is how dangerous those particles are when they are part of a larger material matrix.

Increasingly research is showing what the Royal Society warned about nearly 10 years ago in their report “Nanoscience and nanotechnologies: opportunities and uncertainties”: Workers making products out of nanoparticles are in more danger than those who buy and use the products made from the nanoparticles. But lifecycle risks from these products  have to be more aggressively pursued so that we can take appropriate precautions  while still enjoying all the benefits these nanoparticles can impart.

NNI Founder Urges International Collaboration in Nanotech Research


Mihail Roco is a sometimes-polarizing figure in the development story of nanotechnology. On the one hand, he gave shape and purpose to what became the US National Nanotechnology Initiative (NNI) and led it through its early formative years, but on the other—especially among those who support a vision of nanotechnology involving molecular manufacturing (MNT)—he was at least one of the agents behind moving US funding away from MNT and towards material science.  A sin some still have not forgiven him for. 

Whichever side of the fence you may be on that characterization, it’s hard to deny that Roco has been one of the most influential figures in nanotechnology, not just for the US but for the world. Roco was the man behind turning a scattering of papers in condensed matter/solid state physics or chemistry into a national initiative. In doing so, he unwittingly—or not—launched an international nanotechnology arms race, which has seen at least 35 countries jump on to the bandwagon since the NNI was started.

Make no mistake, this “race” is no joke. There are billions of dollars at stake and national reputations seem to be built up on success in crossing the vague finish line before some other country. 

Beyond mere reputation or pride, countries—including the US—believe that by pumping money into nanotechnology (which up to this point has largely gone to building new research facilities)  they will create for themselves an economic zone, a Silicon Valley of nanotech. There’s no sense in trying to explain that Silicon Valley was a complicated recipe that is probably nearly impossible to duplicate; governments are giving the money away so why not build a new microscopy lab in the middle of nowhere.

On top of everything, this past week we witnessed what may be the height of the nanotech arms race with the arrest and indictment of a nanotechnology scientist from Sandia National Labs, who is accused of sharing research information with the Chinese. 

So after unleashing this billion-dollar nanotech arms race, Roco now is urging collaboration in nanotech to provide the push the field needs to progress. 

“International collaboration in nanoscale science and engineering is essential at this moment because the field is growing rapidly with different focuses and multidisciplinary breakthroughs in different countries, and the synergism of such contributions determines faster and more efficient development,” said Roco in an interview with Korea Herald when he was attending the 9th Korea-US Nano Forum held at Hanyang University in Seoul.

Well, yes, of course, and it’s about time somebody said it. It probably couldn’t have come from a better source either. Many have said that it took the virulent anti-communist Richard Nixon to open detente with China. Perhaps it will take the man who created national nanotechnology initiatives to urge that nanotechnology research is better served when national borders come secondary to scientific inquiry.

Nanosys Gets 3M to Bring Its Quantum Dot Technology to LCDs


It appears that Nanosys Inc. has found a Liquid Crystal Display (LCD) manufacturer to bring its quantum dot material to market. Nanosys will be supplying its Quantum Dot Enhancement Film (QDEF) technology to the Optical Systems Division of 3M Company to produce an LCD capable of displaying 50 percent more color.

“We are working together to improve an area of display performance that has been largely neglected for the last decade,” said Jason Hartlove, President and CEO of Nanosys in a company press release announcing the agreement. “Improving color performance for LCDs with drop-in solutions will bring a stunning new visual experience to the consumer and a competitive advantage to the LCD manufacturer against new display technologies such as OLED.  Working together with 3M and utilizing their outstanding design and supply chain capabilities will allow our QDEF technology to be widely deployed across all product segments and will ensure availability to all customers.”

While Nanosys seems to have found an avenue for its technology in the LCD market, what became of its attempts to break into the Light Emitting Diode (LED) biz? Back in 2010 I covered the company's use of quantum dots for use in LEDs and was provided a primer on the technology from its Vice President of Worldwide Sales & Marketing at the time, Victor Hsia:

“Nanosys synthesizes quantum dot phosphor material which is subsequently packaged in a form called a Quantum Rail. For LED backlit displays, our Quantum Rail is inserted between an illuminating strip of blue LEDs and the input edge of the display's lightguide panel. Current LED backlights use conventional white LEDs (which are BLUE LEDs with YAG phosphor) that cannot produce saturated GREEN or RED colors. In contrast Nanosys' Quantum Rail produces a pure white light by using a BLUE LED with Green and Red Quantum Dot phosphors, which results in a tuned white light source that enables over 100 percent NTSC color gamut using the same high volume LCD display manufacturing flow that exists today.”

So, what happened? I have looked for some more information on how the Nanosys technology is being used in LEDs but haven’t turned up much.

Getting back to this recent announcement, it’s an interesting approach that both 3M and Nanosys are taking. They spruce up good old LCD technology so that it can better compete with Organic Light Emitting Diodes (OLED) technology performance. The big question will be whether it can actually deliver on that promise of equal performance at a fraction of the cost and better energy efficiency. We’ll see when a product comes to market.

Konarka Goes Belly-Up, But Irrational Exuberance is Alive and Well


Oddly it seems that you can’t convince people of the rule that technology-push is never as promising as market-pull. We have to add another example to the long litany of companies that have crashed against the rocks of this simple rule: Konarka—a developer of thin-film solar panels—filed bankruptcy last week under chapter 7 of the Federal bankruptcy laws.

Konarka was launched with great fanfare back in 2001 with Nobel Prize winner Dr. Alan Heeger as one of its founders and despite never quite getting a product to market by 2007 had managed to raise over US $100 million.

It appears that the political press is already making hay with this announcement dubbing the Massachusetts-based Konarka “Romney’s Solyndra” based on the fact that when Mitt Romney was governor, Massachusetts lent $1.5 million to Konarka.

Beyond the issue of political gamesmanship, the area of nanotech in alternative energy solutions remains fertile soil for attracting investors and delivering little in terms of returns

When you have Nobel Laureates in economics saying that the reason solar power is not our main energy source is because of some conspiracy among oil producers, there are plenty of excuses for pursuing technologies that at present just don’t measure up to the fossil fuel variety. 

The lesson to be learned from the cautionary tale of Konarka should not be that investments in new energy sources should be avoided, but instead that we may need an entirely new apparatus for developing emerging technologies. Unfortunately before such a new method is adopted, it seems that other companies will likely follow Konarka into bankruptcy while they beguile investors with stories of their remarkable technologies—which nobody seems to want to buy

Rational Design of Nanomaterials Takes a Step Forward

Measuring, characterizing, and manipulating at the nanoscale are foundational elements of nanotechnology. And this week we’ve seen in news from IBM just how important improving microscopy is to all that.

Now researchers at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have used transmission electron microscopy and advanced liquid cell handling to see if they could gather evidence to support the controversial theory that nanoparticles act as artificial atoms during the growth of crystals.

“We observed that as nanoparticles become attached they initially form winding polycrystalline chains,” says Haimei Zheng, a staff scientist in Berkeley Lab’s Materials Sciences Division in a press release. “These chains eventually align and attach end-to-end to form nanowires that straighten and stretch into single crystal nanorods with length-to-thickness ratios up to 40:1. This nanocrystal growth process, whereby nanoparticle chains as well as nanoparticles serve as the fundamental building blocks for nanorods, is both smart and efficient.”

You can see this process quite clearly in the video:

The research, which was published last week in the journal Science, observed the nanoparticles “undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point.”

This observation and understanding of how nanoparticles make up crystal growth will likely provide important insight into the design of nanomaterials.

“From what we observed only single nanoparticles exist at the beginning of crystal growth, but, as growth proceeds, small chains of nanoparticles become dominant until, ultimately, only long chains of nanoparticles can be seen,” Zheng says. “Our observations provide a link between the world of single molecules and hierarchical nanostructures, paving the way for the rational design of nanomaterials with controlled properties.”

Carbon Nanotubes Go Back Inside Fuel Cells

Researchers have tried to apply carbon nanotubes to fuel cells for some time now. At first there was hope that carbon nanotubes would help fuel cells better store hydrogen. That dream was dashed and then later resurrected. There has also been the idea that carbon nanotubes could be used as a cheaper alternative to expensive catalysts within fuel cells

I suppose those are worthy areas of pursuit, but the two main issues that have prevented fuel cells from gaining wider adoption—at least in the area of powering automobiles—are the costs of isolating hydrogen and building an infrastructure that would deliver that hydrogen to the automobiles. The issue of isolating hydrogen has taken precedence of late in nanotech/fuel cell research both at the commercial level and at research labs

But now researchers from Stanford University are again looking at how carbon nanotubes could replace more expensive catalysts used in oxidizing the hydrogen at the anode within the fuel cell.

Hongjie Dai, a professor of chemistry at Stanford and co-author of the study, believes that a cheaper oxidizing catalyst will facilitate wider adoption of fuel cells.

"Platinum is very expensive and thus impractical for large-scale commercialization," says Dai in the Stanford press release covering the research. "Developing a low-cost alternative has been a major research goal for several decades."

Well, if you could develop a catalyst for this purpose that was essentially free, it still wouldn’t usher in a hydrogen economy any time soon. But I suppose it couldn’t hurt.

The research, which was published in the May 27th online edition of the journal Nature Nanotechnology, showed that when the outer walls of a multi-walled carbon nanotube (MWNT) were shredded—and the inner walls left intact—the catalytic ability of the MWNTs were enhanced while maintaining good electrical conductivity.

What I find most intriguing about the research is the potential to use these imperfect MWNTs for metal-air batteries. The researchers hint at this, though they have yet to fully explore the possibilities.

"Lithium-air batteries are exciting because of their ultra-high theoretical energy density, which is more than 10 times higher than today's best lithium ion technology," Dai says in the Stanford press release. "But one of the stumbling blocks to development has been the lack of a high-performance, low-cost catalyst. Carbon nanotubes could be an excellent alternative to the platinum, palladium and other precious-metal catalysts now in use."

I think it's all together possible that researchers at IBM and the US national labs who have been working on metal-air batteries for years now might be somewhat more interested in this line of research than fuel-cell manufacturers.



IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

Dexter Johnson
Madrid, Spain
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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