Why quantum dots can join every aspect of everyday life


QDOTS imagesCAKXSY1K 8Nanotechnology is often confined to niche products, but quantum dots are so versatile they could be used in everything from light bulbs to laptops.

 

 

 

 

Sheet of semiconductor crystals

Tiny bits of semiconductor crystals – so-called quantum dots – have such remarkable properties that scientists think they will soon be used in everything from light bulbs to the design of ultra-efficient solar cells. Photograph: Science Photo Library

The properties of a material were once thought to be defined only by its chemical composition. But size matters too, especially for semiconductors. Make crystals of silicon small enough – less than 10 nanometres – and their tiny dimensions can start to dictate how the atoms behave and react in the presence of other things.

These tiny bits of semiconductor crystals – so-called quantum dots – have such remarkable, novel properties that scientists think they will soon be used in everything from light bulbs to imaging of cancer cells or in the design of ultra-efficient solar cells.

Semiconductors such as silicon or indium arsenide are chosen to build electronic circuits because of the discrete energy levels at which they can give off electrons or photons. This makes them useful in building switches, transistors and other devices. It was once thought these energy levels – known as band gaps – were fixed. But shrinking the physical size of the semiconductor material to quantum-dot level seems able to change the band gaps, altering the wavelengths of light the material can emit or changing the energy it takes to change a material from an insulator to a conductor.

Instead of looking for brand new materials to build different devices, then, quantum dots make it possible to use a single type of semiconductor to produce a range of different characteristics. Researchers could tune dots made from silicon to emit a range of different colours in different situations, for example, instead of having to use a range of materials with different chemical compositions.

“The main application for quantum dots at the moment is biological tagging of cells,” says Paul O’Brien, a professor of inorganic materials at the University of Manchester and co-founder of Nanoco Technologies a quantum dot manufacturer also based in Manchester. They are used in the same way as fluorescent dyes, to label agents, he says, but with the advantage that a single laser source can be used to illuminate many different tags each with a specific wavelength.

By attaching different types of quantum dots to proteins that target and attach to specific cell types in the body, these bits of semiconductor can be used by doctors to monitor different kinds of cells. When a laser is then directed on to tagged cells, doctors can see what colour they glow.

The ability to shine also makes quantum dots well suited to produce white light. Existing white bulbs based on low energy light emitting diode (LED) technology tend to produce a garish and bluish form of light that notoriously feels cold, says O’Brien. This is because these LEDs use a phosphor that produces an artificial white light that contains less red wavelengths than natural white light. By embedding quantum dots into a film that is placed over a bulb containing blue LEDs, it is possible to get a much warmer colour of white light. The blue light  from the LED stimulates the quantum dots which, in turn, emit light in a range of colours. Provided you have chosen your dots carefully, these will combine to form white light.

The first of these quantum dot lights hit the market in 2010, a partnership between QD Vision, an MIT spinout in Lexington, Massachusetts, and Nexxus Lighting of Charlotte, North Carolina.

Backlights for laptops, tablets and mobile devices are next in line, and they should appear in products before the end of 2012 says VJ Sahi, head of corporate development at materials design company Nanosys of Palo Alto, California. Besides the colour advantages, quantum-dot-based backlights can be three times more efficient than traditional backlights.

Eventually, says Sahi, quantum dots will do more than just light up displays. The long-term aim is use them to create each red, green and blue sub-pixel that makes up a coloured display. This should produce much brighter colours and consume less power than LCD or even the latest state-of-the-art organic LED (OLED) displays. They should also have no problems with viewing angles, he adds.

The interesting properties of quantum dots come from the fact that they behave like tuning forks for photons, a result of a phenomenon called confinement. At less than 10 nanometres in size – about 50 atoms – they fall within the dimensions of a critical quantum characteristic of the material known as the exciton Bohr radius. The energy levels of electrons within the material’s atoms are constrained and, when a photon or electron hits an atom and excites it, the atom re-emits the energy as a photon of a very specific energy level.

Quantum dots also have another trick up their sleeve. Besides converting photons of one energy into photons of another, they can also be used to release electrons and create electrical currents: in other words they can be used to make solar cells. Arthur Nozik at the National Renewable Energy Laboratory in Boulder, Colorado, says that quantum-dot solar cells would be much more efficient at converting the energy from photons and therefore boost the amount of power they can produce.

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Nano Materials Will Enable Electronics and Semiconductors: But Costs Must be Reduced


Though India had become a dominant player in the global software arena, it is a laggard in the electronics hardware industry despite resources and talent, says founder director-general of National Informatics Centre N. Seshagiri

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BANGALORE, INDIA: The fledgling Indian semiconductor industry has to invest in the research and development (R&D) of nanotechnology to face the challenge of disruptive technologies and shrinking innovative product cycles, a top expert said on Monday.
“Nanotechnology is the future of the electronics industry worldwide.

With disruptive technologies and product cycles shrinking, the Indian semicon industry has to invest in nanotechnology R&D to innovate applications using nano materials and nano tubes,” founder director-general of National Informatics Centre N. Seshagiri said here.

Delivering the inaugural address at the sixth Vision Summit of the Indian Semiconductor Association (ISA) here, Seshagiri told about 300 delegates that though India had become a dominant player in the global software arena with about $60 billion export revenue, it is a laggard in the electronics hardware industry despite resources and talent.

“It will be a blunder to ignore the innovations taking place in nanotechnology worldwide, especially in the US, Germany and Korea and application of nano materials and nano tubes in the manufacturing of electronics products for diverse applications, especially consumer goods, including mobiles, laptops and tablets, medical equipment, energy efficiency and security,” the former special secretary to the IT department and Planning Commission said.

Noting that the sunrise nanotechnology sector was a $20 billion industry worldwide with about 1,000 nano-based products rolled out by 400 firms across 25 countries, the eminent technocrat said the market size for nanotech electronics was estimated to be $1.6 trillion over the next two years.

“The absence of a chip-making (fab) facility and sound electronics manufacturing base should not deter the Indian semicon and hardware industry from using nanotechnology in developing sub-systems and electronic devices, which will account for about 30 percent of the projected $30 billion industry in 2014,” Seshagiri pointed out.

Referring to the huge investments being made by global chip maker Intel and IT major IBM in developing 40 nanometre and sub-25 nanometre flash memory, the former official said the cost of producing nano materials and nano tubes had to be reduced substantially through R&D and innovation so as to bring down the overall cost of end-products.

“Presently, it costs about $400,000 to produce a kilogram of nano tubes even in the US. As nanotechnology and miniaturisation of electronic products are going to be order of this decade, the Indian electronics hardware industry had to catch up with the rest of the world to be in race for a pie of the multi-billion dollar market,” Seshagiri asserted.

Earlier, Union IT department Joint Secretary Ajay Kumar said demand for electronics hardware was projected to be a whopping $400 billion by 2020 from $45 billion in 2009 in the Indian sub continent, while the global demand is expected to be $2.4 trillion by the end of this decade.

“The Indian semicon industry has to move up the value chain from chip designing and embedded systems to fabrication, manufacturing and value addition to increase its share of the domestic market, which continues to be import dependent,” Kumar added.

“The IKEA of Solar Fields”


Oman Project Is A Step Toward ‘The Ikea Of Solar’

GlassPoint installation in Oman, with oil rigs in background (Credit: GlassPoint)
In the desert of southern Oman, near the border with Yemen, 4 acres of glass houses catch the sun. They sit in the Amal West oilfield, operated by Petroleum Development Oman. But these glasshouses aren’t growing tomatoes, or any other crop, rather they are making steam.

When it comes to developing its oil and gas reserves Oman faces a conundrum. The small country on the southeastern tip of the Arabian Peninsula has a lot of oil, but it is mostly of the heavy kind.

Far from gushing up out of the sands, this oil is stubborn and needs to be coaxed out of its reservoirs. To do that, Petroleum Development Oman (60% Oman government, 34% Royal Dutch Shell), has perfected the technique of blasting steam down into the oil reservoirs to soften and loosen up the thick crude and push it up to the surface. Heating water to make that steam for injection requires a lot of energy.

They could use some of the oil they pull up to generate steam, but it’s more profitable to sell that on the world market. So instead, PDO burns natural gas. Oman still has a lot of gas, but is in the process of doubling gas prices for industrial users, and has even had to divert some of its supply away from LNG exports and into the oilfields.

A solution could be on the horizon. At PDO’s Amal West oil field in southern Oman, a California-based company called GlassPoint has installed an innovative solar system that seeks to assist in the steam-generation process by boiling water with sunshine.

From outside, the GlassPoint installation doesn’t look a thing like any solar project you may have in your mind’s eye. It’s not photovoltaic-based, so there’s no panels. And there’s no stand-alone solar-concentrating dishes.

These glasshouses are filled with flimsy mirrors–little more than curved sheets of aluminum foil, suspended by wires from the ceiling. Motors pull the wires, adjusting the mirrors’ pitch to ensure they’re tracking the sun perfectly. The reflected rays are focused and concentrated to heat water inside a network of pipes, boiling it into steam that is continually injected down oil wells deep underground, loosening up and pushing out the gunky crude.

There’s good reasons for putting the gear under glass. Wind is a problem for solar installations — they need to be sturdy enough to withstand gusts, and heavier systems require more robust actuators and gears. Glasspoint’s technique enables them to use cheaper, lightweight materials. The glass also protects the gear from dust — it’s easier to clean dust off of glass than from mirrors.

The Oman project, covering 4 acres and generating the equivalent of 7 mw of energy per day, is only a test pilot. But so far the tests look good. Syham Bentouati, head of new technology implementation at PDO writes in an email that the system has already proven that it can generate steam at the right specs for oil recovery. Next is for GlassPoint to prove that the system can work reliably for a year. “So far, the performance is very promising and likely to be above contractual requirement,” writes Bentouati.

If all goes well, a full-scale GlassPoint build out in Oman could come next. PDO won’t say how big, or what it might cost, but industry sources suggest the scale would consist of more like 3,000 mw and cost upwards of $1.5 billion, assuming installation costs of roughly 50 cents per watt.
GlassPoint is already gearing up for that kind of scale. I recently chatted with Rod MacGregor, CEO of GlassPoint, who said that with help from a $26 million investment by Royal Dutch Shell he has opened a factory with 100 people working in Shenzhen, China building components. Their goal is to make the sets so simple and easy to build that labor costs can be kept to a minimum.

It’s a simple vision, says MacGregor, who is also eyeing Kuwait and Bahrain as future customers: “We want to be the Ikea of solar fields.”

For more on Glasspoint, check out this story about their first installation at a Berry Petroleum oil field in California.

“Balance” the Key for Quantum Dot Enabled Solar Cells


Posted: May 24th, 2013

Balance is key to making quantum-dot solar cells work

(Nanowerk News) There has been great interest in recent years in using tiny particles called quantum dots to produce low-cost, easily manufactured, stable photovoltaic cells. But, so far, the creation of such cells has been limited by the fact that in practice, quantum dots are not as good at conducting an electric charge as they are in theory.

Something in the physical structure of these cells seems to trap their electric-charge carriers (known as electrons and holes), but researchers have been hard-pressed to figure out exactly what. Now, for the most widely used type of quantum dots, made of compounds called metal chalcogenides, researchers from MIT may have found the key: The limiting factor seems to be off-kilter ratios of the two basic components that make up the dots.

The new findings — by Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering, materials science and engineering graduate student Donghun Kim, and two other researchers — were reported this month in the journal Physical Review Letters (“Impact of Stoichiometry on the Electronic Structure of PbS Quantum Dots”).

This illustration shows a lead sulfide quantum dot array. Each quantum dot (the colored clusters) is ‘passivated’ by molecules that bind to its surface. Dots that are made up of unequal amounts of lead and sulfur tend to cause electrons (shown in red) to become highly localized, which can substantially lower the electrical transport of the device. (Image: Donghun Kim and Jeffrey C. Grossman)

In bulk quantities of lead sulfide, the material used for the quantum dots in this study, the ratio (known by chemists as “stoichiometry”) of lead atoms to sulfur atoms is exactly 1-to-1. But in the minuscule quantities of the material used to make quantum dots — which, in this case, were about 5 nanometers, or billionths of a meter, across — this ratio can vary significantly, a factor that had not previously been studied in detail. And, the researchers found, it turns out that this ratio is the key to determining the electrical properties of the material.

When the stoichiometry is a perfect 1-to-1, the quantum dots work best, providing the exact semiconductor behavior that theory predicts. But if the ratio is off in either direction — a bit more lead or a bit more sulfur — the behavior changes dramatically, impeding the solar cell’s ability to conduct charges.
Taking care of dangling bonds

Grossman explains that every atom inside the material has neighboring atoms on all sides, so all of that atom’s potential bonds are used, but some surface atoms don’t have neighbors, so their bonds can react with other atoms in the environment. These missing bonds, sometimes called “dangling bonds,” have been thought to play a critical role in a quantum dot’s electronic properties.

As a result, the consensus in the field has been that the best devices will have what is known as full “passivation”: the addition of extra molecules that bind to any loose atomic bonds on the material’s surface. The idea was that adding more of the passivating material (called ligands) would always improve performance, but that didn’t work as scientists had expected: Sometimes it improved performance, but sometimes it made it worse.
“That was the traditional view that people believed,” says Kim, who was the paper’s lead author. But now it turns out that “how many dangling bonds the quantum dot has is not always important, as it doesn’t really affect the density of trap states — at least in lead-and-sulfur-based dots.” So, if a given dot already has an exact 1-to-1 ratio, adding ligands makes it worse, Kim says.

The new research solves the mystery of why that is: Computer simulations reveal that there is an optimum amount of passivating material, an amount that neutralizes exactly enough of these loose bonds to counterbalance any discrepancy in the stoichiometry, restoring an effective 1-to-1 balance. Too much or too little passivating material, and the imbalance remains, or even increases, reducing the efficiency of the material.

Great potential for solar cells
There has been “a lot of excitement” about the potential for quantum dots in applications including electronic devices, lighting and solar cells, Grossman says. Among other potential advantages, quantum-dot solar cells could be made in a low-temperature process, by depositing material from a solution at room temperature, rather than the high-temperature, energy-intensive processes used for conventional photovoltaics. In addition, such devices could be precisely “tuned,” to obtain maximum conversion of specific wavelengths (colors) of light to energy, by adjusting the size and shape of the particles.

To go beyond the efficiencies achieved so far with quantum-dot solar cells, Grossman says, researchers needed to understand why the charges got trapped in the material. “We found something quite different than what people thought was causing the problem,” he says. “We hope this will inspire experimenters to look at this in new ways,” he adds.

Figuring out how to apply this knowledge, and how to produce quantum dots with well-controlled elemental ratios, will be “challenging,” Grossman says, “but there are a number of ways of controlling the surface.”

The discovery came as a pleasant surprise, Kim says, noting that the researchers unexpectedly observed the origin of trap states as they were studying the way surface treatments would affect the material. But now that they have found this key factor, he says, they know what their goal is in further research: “The electrons will be happy when the distribution … is just right,” he says.

Giulia Galli, a professor of physics and chemistry at the University of California at Davis who was not connected with this research, says it is “quite a creative and important piece of work,” and adds that, “I’m pretty sure this will stimulate new experiments” to engineer the stoichiometry of quantum dots in order to control their properties.

Source: By David L. Chandler, MIT
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Quantum Dot Enabled Display Screens Poised to Emerge & Dominate


*** Note to Readers: A great article contrasting emerging superior Quantum Dot Enabled Technologies for Display Screens with existing OLED/ LCD technologies.

A new LCD backlighting technology from material science company, Nanosys Inc, delivers the promises of OLED displays at LCD prices.

Who IS Nanosys?

Nanosys is an advanced materials architect. We design and build new materials at the molecular level to improve products like tablets, TVs and even electric vehicles. Our products enable stand-out electronics using known, viable manufacturing processes. Our ability to engineer new materials allows us to create products with performance capabilities far surpassing today’s standards like TVs with lifelike color and batteries that last all day.

What is QDEF?

QDEF is a new kind of backlight technology that’s going to enable a new generation of LED backlit TVs that have OLED-like performance at only a fraction of the cost.

Display performance is all about light- how much can I generate, how efficiently, how wide a range of colors, and how much resolution can I pack in? QDEF gives LCD makers a way to tune the spectrum of light in the backlight and dramatically improve picture quality. It does this with millions of tiny nanoscrystal phosphors, called “quantum dots.” These “dots” emit light at a very precise wavelength and can be controlled by their size. We use a mix of different color emitting dots to create the perfect backlight for your LCD. The result is richer, more saturated color that’s more true to life.
Jeff Yurek from Nanosys describes QDEF in detail in this article.

[Ed] For more detail on LCD display anatomy, see Bill Hammack’s excellent video.

What are the advantages of QDEF over today’s backlit LED displays?
QDEF is also an LED-based LCD technology but there are some key differences and advantages compared to today’s LED TV’s.

A standard LCD backlight creates white light using a technology called YAG (yttrium aluminum garnet) phosphor. YAG produces a two-color spectrum, dominated by blue and accompanied by a broad, yellow component. It lacks a strong red and green element and this results in poor color performance.
QDEF creates a pure white backlight that is designed specifically for LCD displays. This light, made up only of narrow spectral peaks in red, blue and green wavelengths, allows for wide color gamut performance when mixing these primary colors at the pixel level. It does this with great efficiency, so it doesn’t sacrifice the brightness of the display.

As you can see in the comparison below, the 47 inch HDTV on the left has been modified with Nanosys’ QDEF technology. It shows a much wider range of colors, note the difference in the greens here.

QDEF seems to be a viable alternative to OLED. What technical advantages and disadvantages does QDEF have over OLED?

QDEF offers the same high color gamut performance as OLED, while also offering a brighter, more energy efficient display. Unlike OLED, QDEF displays can be made for very large sizes.

Color Purity

Both OLED and QDEF are able to reproduce greater than 100 percent of the NTSC color gamut. In our experience, (see measurements below) QDEF can deliver more, especially in terms of red. This means that QDEF can offer more coverage, not just area, of more of the industry standard high gamut formats like Adobe RGB, DCI-P3 and NTSC.

[Ed] For more detail on color gamut, see our previous article
Efficiency

This is a difficult comparison to make since LCD and OLED are such different technologies. OLED is emissive, meaning each pixel is also a light source, and so the amount of power it consumes is dependent on content. For example, if a pixel is black, it is consuming no power while a white pixel can consume a significant amount of power due to the inefficiencies in the underlying material system, particularly in terms of blue, which is only 4-6 percent efficient. This “zero power consumption for black” is a really nice story, but in practice, it’s not very useful since we don’t spend a lot of time looking at black screens. Screens with white backgrounds, like most of the web (i.e., Google), or e-book reading are much more challenging for OLED. QDEF is an LCD technology, so it relies on a backlight that stays on all the time. This sounds less efficient at first glance but QDEF is able to improve the efficiency of the system by tuning the spectrum of the light in the backlight to match the color filters. This means less wasted light because you are only generating light that you will see and much more color for the same amount of power input. Compare the iPhone 4 LCD and Nexus OLED display power consumption in Displaymate’s Shootout
Reliability and Lifespan
Nanosys spent a significant amount of time designing and testing QDEF to ensure it is of the highest quality and reliability. More than 100 patents have gone into the design of QDEF, and it has been tested to meet industry standard lifetimes for TV’s (ie, 50,000 hours or more). OLED has historically been limited by the performance of its blue component and the mismatch between red, green and blue lifetimes can lead to issues over the life of the display.

Brightness

QDEF displays are as bright as LCDs. In tests that Nanosys has conducted using QDEF in an iPad, we were able to match the iPad’s brightness without needing extra power. OLED displays have to work harder to achieve the same level of brightness as LCD displays, which translates directly to higher power consumption. In order to maintain the same level of brightness with a less efficient OLED display, the device can use a lot of power.

Size

QDEF’s manufacturing process scales very easily; it can be made as large as the very biggest LCDs on the market today. So while 55” was a big announcement for OLED at CES, QDEF is ready to enable better color at 65” and beyond- today.

PPI

QDEF is compatible with all LCD resolutions- i.e. 300+ ppi and above.
Contrast Ratio and Black Level
QDEF doesn’t affect the “black” level of LCD displays. That said, I give a lot of QDEF display demos and it’s not uncommon for people to say they think the contrast ratio is better with QDEF. I believe it may have something to do with the Helmholtz Kohlrousch or HK effect, which says that intensely saturated colors increase our perception of the brightness of that color. This means that images tend to ‘pop’ a little more than a meter reading might suggest they would. I’ll also add that I was at CEDIA this year and saw some newer LCD TVs with local dimming technology that had stunning blacks. In one demo, you could not tell which TV was on in a pitch dark room. So I think we’re getting to a point with state-of-the art LCDs where contrast ratio is less of a differentiator for OLED.
How have you overcome the problem of thermal stability normally associated with quantum dots?
Nanosys has invested about a decade of R&D into QDEF to ensure it is of the highest quality and reliability. More than 100 patents have gone into the design of QDEF, and it has been tested to meet industry standard lifetimes for TV’s (i.e., 50,000 hours or more).

From a manufacturing perspective, what is cost implication of modifying an existing production line with QDEF vs. building an entirely new production line for OLED?

A manufacturer will incur virtually no cost to switch to QDEF displays. They simply swap out the diffuser sheet they are currently using for a QDEF sheet and exchange the white YAG phosphor LEDs to cheaper blue LEDs. Everything else remains the same. For OLED, a manufacturer must invest hundreds of millions to build an entire new fab for a completely different technology.

What is the cost of a QDEF display vs. a comparable size OLED display?

Nanosys is aiming to deliver QDEF to the manufacturer on a cost neutral basis. We can do this because display makers will be able to use cheaper blue LEDs, offsetting the cost of QDEF. The final consumer pricing will ultimately be decided by the brands when they go to market. In terms of OLED, we’ve heard that the 55” panels everyone saw at CES this year will hit the market at around the $8,000 mark. Given that you can pick up a 65” LCD for less than half of that price, I think there will be a significant price advantage for QDEF even if brands decide to position it as a premium product relative to other LCDs.

When will commercial QDEF displays be available?

Nanosys has delivered thousands of square feet of QDEF to our customers in anticipation of scaling up production of commercial products in the very near future. We cannot speak to the schedule our customers hold for when and where those products will be available.

Why do I need a wider-gamut display on my TV when the best content I can get is limited to Rec.709?

When HD TVs first started rolling off assembly lines, there was very little HD content available but the market responded pretty quickly. The content creation pipeline from TV stations, to sports broadcasts, to Hollywood started to upgrade their capture capabilities to take advantage of the extra resolution. We also s saw “upscaling” DVD players right away. While these DVD players couldn’t make up new data, they could scale the image to fill the screen and make for an improved experience from the library of DVDs that you already owned and had potentially invested a lot in.
I think we’ll see something very similar with color. There are some great color ‘upscaling’ technologies that are starting to emerge that increase the saturation of your rec 709 content on the fly without blowing out flesh tones. So the red Ferrari in the car chase seen really pops but the main characters look just right.

Finally, Hollywood has been capturing film in high color gamut formats for years but have to throw much of it out in post-production in order to match the color performance of your TV. Producers are leaving the best color on the cutting room floor. Color movie film, for example, has much more color saturation than the rec 709 on a Blu-ray disc. This means Hollywood can go back to the vaults and remaster decades of content so that it looks like it looked on the big screen on your TV.
[Ed] Don’t know what Rec. 709 is? See our previous article.

What impact will high color gamut displays have for consumers at home?

High color displays will allow for consumers to enjoy more visceral, more impactful, and truer to life content. Current home TVs are only able to display 30 to 40 percent of the visual color spectrum, and mobile devices are only capable of displaying 20 to 30 percent. This means the user is missing a large component of the visual experience. High color performance displays will make our digital viewing experience of movies and videogames more lifelike. Filmmakers and video game developers will be able to more accurately bring their creative vision to life.

Roll to Roll Printing Technologies: Exploding Growth in Flexible Devices


Flexible devices manufactured by roll-to-roll technologies to reach nearly $22.7 billion by 2017

05/23/2013

The diffusion of roll-to-roll technologies is expected to have a marked effect in lowering the unit prices of flexible devices.

Consequently, while consumption in terms of volume is forecast to rise very rapidly, revenues will increase somewhat more moderately.

As a result, the total market for roll-to-roll flexible devices is forecast to grow at a CAGR of 16.1 percent from 2012 to 2017, reaching global revenues of nearly $22.7 billion by 2017.

The global market for flexible devices manufactured by roll-to-roll technologies increased from $8.5 billion in 2010 to nearly $10 billion in 2011, and was valued at nearly $10.8 billion in 2012, growing at a compound annual growth rate (CAGR) of 12.3 percent during the two-year period.

Circuit devices currently account for a nearly 96.9 percent share of all revenues in 2012. Sales within this segment are primarily associated with flexible printed circuits.

Displays and other optoelectronic devices account for a 2.5 percent share of the roll-to-roll flexible devices market, with total 2012 revenues of $264 million, while solar cells, sensors, and other emerging applications currently represent a combined share of only 0.7 percent of the total.

There are several reasons why flexible devices are gaining increasing importance. First, flexible devices are being created with the same functionalities as traditional (rigid) integrated circuits, yet are produced with low-cost materials and processes with the intent to make them commercially available at lower unit prices than their rigid counterparts.

To read the Full Article, Go Here:

http://www.electroiq.com/articles/sst/2013/05/flexible-devices-manufactured-by-roll-to-roll-technologies-to-re.html

Stronger, Lighter Nano-composite Materials


Posted: May 20th, 2013

Advanced carbon nanocomposite materials for planes, trains and automobiles

(Nanowerk News) These days, aerospace engineering is all about the light stuff: building airplanes with lighter wings, fuselage and landing gear in an effort to reduce fuel costs.

Advanced carbon-fiber composites have been used in recent years to lighten planes’ loads. These materials can match aluminum and titanium in strength but at a fraction of the weight, and can be found in aircraft like the Boeing 787 and Airbus A380, reducing such jets’ weight by 20 percent.

For the next generation of commercial jets, researchers are looking to even stronger and lighter materials, such as composites made with carbon fibers coated with carbon nanotubes — tiny tubes of crystalline carbon. When arranged in certain configurations, nanotubes can be hundreds of times stronger than steel, but only one-sixth the weight, making such composites attractive for use in airplanes, as well as cars, trains, spacecraft and satellites.
But a significant hurdle to achieving such composites lies at the nanoscale: Scientists who have tried growing carbon nanotubes on carbon fibers have found that doing so significantly degrades the underlying fibers, stripping them of their inherent strength.

Now a team from MIT has identified the root cause of this fiber degradation, and devised techniques to preserve the fibers’ strength. Applying their discoveries, the researchers coated carbon fibers with nanotubes without causing fiber degradation, making the fibers twice as strong as previous nanotube-coated fibers — paving the way for carbon-fiber composites that are not only stronger, but also more electrically conductive. The researchers say the techniques can easily be integrated into current fiber-manufacturing processes.

“Up until now, people were basically improving one part of the material but degrading the underlying fiber, and it was a trade-off, you couldn’t get everything you wanted,” says Brian Wardle, an associate professor of aeronautics and astronautics at MIT. “With this contribution, you can now get everything you want.”

A paper detailing the results by Wardle and his colleagues is published in the journal ACS Applied Materials and Interfaces (“Circumventing the Mechanochemical Origins of Strength Loss in the Synthesis of Hierarchical Carbon Fibers”). Co-authors are postdoc Stephen Steiner, who contributed to the research as a graduate student, and Richard Li, a graduate student who was an undergraduate in Wardle’s lab.

MIT researchers have produced carbon fibers coated in carbon nanotubes without degrading the underlying fiber’s strength. The engineered fibers may be woven into composites to make stronger, lighter airplane parts.
Getting to the nitty-gritty of fiber degradation.

To understand how carbon fibers are manufactured, the group visited carbon-fiber production plants in Japan, Germany and Tennessee. One aspect of the fiber-manufacturing process stood out: During manufacturing, fibers are stretched to near their breaking point as they are heated to high temperatures. In contrast, researchers who have tried to grow nanotubes on carbon fibers in the lab typically do not use tension in their fabrication processes.

To replicate the manufacturing process they witnessed, Li and Steiner engineered a small-scale apparatus made of graphite. The researchers strung individual carbon fibers — each 10 times thinner than a human hair — across the device, much like the strings of a guitar, and hung tiny weights on either end of each fiber, pulling them taut. The group then grew carbon nanotubes on the fibers, first covering the fibers with a special set of coatings, and then heating the fibers in a furnace. They then used chemical vapor deposition to grow a fuzzy layer of nanotubes along each fiber.

To get nanotubes to grow, the fiber typically needs to be coated with a metal catalyst like iron, but researchers have hypothesized that such catalysts might also be the source of fiber degradation. In their experiments, however, Steiner and Li found that the catalyst only contributed to about 15 percent of the fiber’s degradation.
“When we got to the nitty-gritty of it, we found that the metal catalyst, the perceived culprit, turned out to be more of an accomplice,” Steiner says. “We could see it did a little damage, but it wasn’t the thing really killing everything.”

Instead, the group found, after further experiments, that the majority of fiber degradation was due to a previously unidentified mechanochemical phenomenon arising from a lack of tension when carbon fibers are heated above a certain temperature.
Hair conditioner in reverse
After identifying the causes of fiber degradation, the researchers came up with two practical strategies for growing nanotubes on carbon fiber that preserve fiber strength.

First, the team coated the carbon fiber with a layer of alumina ceramic to “disguise” it, enabling the iron catalyst to stick to the fiber without degrading it. The solution, however, came with another challenge: the layer of alumina kept flaking off.

To keep the alumina in place, the team developed a polymer coating called K-PSMA — which, as Steiner describes it, works like hair conditioner in reverse. Hair conditioners have two seemingly opposite chemical features: a water-absorbent component that allows the conditioner to stick to hair, and a waterproof component that keeps hair from getting frizzy. Likewise, K-PSMA has hydrophilic and hydrophobic components, but its waterproof feature sticks to the carbon fiber, while the water-absorbent component attracts the alumina and the metal catalyst.
In their experiments, the researchers found the coating allowed the alumina and metal catalyst to stick, without having to add other processes, like pre-etching the fiber surface. The team placed the coated fibers under tension, and successfully grew nanotubes without damaging the fiber.

For the group’s second strategy, Steiner observed that it may be possible to eliminate the need for tension by reducing the temperature of nanotube growth. Using a recently discovered nanotube-growth process together with K-PSMA, the team demonstrated it is possible to grow nanotubes at a much lower temperature — nearly 300 degrees Celsius cooler than is typically used — avoiding damage to the underlying fiber.
“This process reduces not only the amount of energy and volume of gas required, but the amount of extraneous substances you have to put on the fiber,” Steiner says. “It’s actually pretty simple and cost-effective.”
Milo Shaffer, a professor of materials chemistry at Imperial College, London, says the group’s carbon-fiber techniques may be useful in designing composites for use in electrodes and air filters. A next step toward this goal, he says, is to make sure the fiber’s various layers and coatings stay in place.

“This result indicates an important factor to be incorporated in future ‘hairy carbon fiber’ developments,” says Shaffer, who did not contribute to the research. “The effect of the various coating combinations on [nanotube] attachment, and the eventual — and critical — fiber-matrix adhesion in composites, remains to be explored.”
The researchers have filed a patent for the two strategies, and envision advanced fiber composites incorporating their techniques for a whole range of applications.
“There are not a lot of people innovating materials chemistry for advanced aerospace structural applications,” Steiner says. “I think this is particularly exciting, and has a very real possibility to make a large-scale impact on the environment, and on the performance of aerospace vehicles.”

Read more: http://www.nanowerk.com/news2/newsid=30571.php#ixzz2TuVxgXZ5

InkJet Printed Graphene = Foldable Electronics?


Posted: May 20th, 2013

Inkjet-printed graphene opens the door to foldable electronics

(Nanowerk News) Imagine a bendable tablet computer or an electronic newspaper that could fold to fit in a pocket.

The technology for these devices may not be so far off. Northwestern University researchers have recently developed a graphene-based ink that is highly conductive and tolerant to bending, and they have used it to inkjet-print graphene patterns that could be used for extremely detailed, conductive electrodes.

The resulting patterns are 250 times more conductive than previous attempts to print graphene-based electronic patterns and could be a step toward low-cost, foldable electronics.

A paper describing the research, “Inkjet Printing of High Conductivity, Flexible Graphene Patterns,” was published April 8 in the Journal of Physical Chemistry Letters (“Inkjet Printing of High Conductivity, Flexible Graphene Patterns”).

“Graphene has a unique combination of properties that is ideal for next-generation electronics, including high electrical conductivity, mechanical flexibility, and chemical stability,” said Mark Hersam, professor of materials science and engineering at Northwestern’s McCormick School of Engineering and Applied Science. “By formulating an inkjet-printable ink based on graphene, we now have an inexpensive and scalable path for exploiting these properties in real-world technologies.”

Inkjet printing has previously been explored as a method for fabricating transistors, solar cells, and other electronic components. It is inexpensive, capable of printing large areas, and can create patterns on a variety of substrates, making it an attractive option for next-generation electronics.

Inkjet printing with graphene — ultra-thin sheets of carbon with exceptional strength and conductivity — is extremely promising, but it has remained a challenge because it is difficult to harvest a sufficient amount of graphene without compromising its electronic properties. Exfoliating, or breaking apart, materials such as graphite often require oxidizing conditions that make the resulting graphene oxide material less conductive than pure carbon. Pristine unoxidized graphene can be achieved through exfoliation, but the process requires solvents whose residues also decrease conductivity.

The Northwestern researchers have developed a new method for mass-producing graphene that maintains its conductivity and can be carried out at room temperature using ethanol and ethyl cellulose to exfoliate graphite. This relatively clean process minimizes residues and results in a powder with a high concentration of nanometer-sized graphene flakes, which is then mixed into a solvent to create the ink.

The researchers demonstrated printing the ink in multiple layers, each 14 nanometers thick, to create precise patterns. The ink’s conductivity remains virtually unchanged, even when bent to a great degree, suggesting that graphene inks could be used to create foldable electronic devices in the future.

Read more: http://www.nanowerk.com/news2/newsid=30577.php#ixzz2TuPT0Sn7

Nano-Tech Sealant closes wounds and hinders bacterial infection


QDOTS imagesCAKXSY1K 8A new joining material for laser welding tissue during operations has the  potential to produce stronger seals and provide an alternative to sutures and  stapling in intestinal surgery, scientists report.

Their study, which involves use of a gold-based sealing material, appears in  the journal ACS Nano.

Kaushal Rege and colleagues from Arizona State University explained in a  statement that laser tissue welding (LTW) is a stitch-free surgical method for  connecting and sealing blood vessels, cartilage in joints, the liver, the  urinary tract and other tissues.

Read more:  http://www.theengineer.co.uk/military-and-defence/news/sealant-closes-wounds-and-hinders-bacterial-infection/1016263.article#ixzz2TDXuCH98

Nanoparticles Harness Powerful Radiation Therapy for Cancer


Posted: May 17th, 2013

Nanoparticle harnesses powerful radiation therapy for cancer

(Nanowerk News) Researchers at the University of Missouri have demonstrated the ability to create a multi-layered harness nanoparticle that can safely encapsulate powerful alpha-emitting radioisotopes and target tumors. The resulting nanoparticles not only offer the possibility of delivering tumor-killing alpha emitters to tumors, but also sparing healthy tissue from radiation damage. J. David Robinson and his colleagues published their findings in the journal PLoS One (“Gold Coated Lanthanide Phosphate Nanoparticles for Targeted Alpha Generator Radiotherapy”).Typically, when radiation treatment is recommended for cancer patients, doctors are able to deliver radiation from a source outside the body or they might inject one of several radiopharmaceuticals that emit low-energy radiation known as beta particles. For years, scientists have been studying how to use “alpha emitters,” which are radioactive elements that release high-energy alpha particles that would more effectively damage cancer cells and trigger cell death. The challenge to using alpha emitters is that the decay elements, the so-called daughters, are themselves highly toxic and difficult to contain in the vicinity of the tumor, thus causing significant damage to healthy tissues.”If you think of beta particles as slingshots or arrows, alpha particles would be similar to cannon balls,” said Dr. Robertson. He explains that recent work has shown that alpha particles can be effective in treating cancer in specific instances. “For example, a current study using radium-223 chloride, which emits alpha particles, has been fast-tracked by the U.S. Food and Drug Administration because it has been shown to be effective in treating bone cancer. However, it only works for bone cancer because the element, radium, is attracted to the bone and stays there. We believe we have found a solution that will allow us to target alpha particles to other cancer sites in the body in an effective manner.”In their studies, Dr. Robertson and colleagues from Oak Ridge National Laboratory and the School of Medicine at the University of Tennessee in Knoxville used the isotope actinium-225, an element that when it decays produces a high-energy alpha particle and radioactive daughter elements, which are also capable of emitting alpha particles. Efforts to contain the daughter elements using traditional molecular constraints proved fruitless because the emitted alpha particles broke the chemical bonds necessary to hold the daughter elements in place.The Missouri team solved this problem by sequestering actinium-225 in the core of a gold-coated magnetic nanoparticle. The magnetic layer, comprised of gadolinium phosphate, serves to increase retention of the daughter elements while simplifying particle purification and the gold coating provides a surface to which tumor-targeting molecules can be attached. In the experiments described in their current publication, the researchers used an antibody that targets a receptor found on the surface of lung tumors.”Holding these alpha emitters in place is a technical challenge that researchers have been trying to overcome for 15 years,” Dr. Robertson said. “With our nanoparticle design, we are able to keep more than 80 percent of the element inside the nanoparticle 24 hours after it is created.” While alpha particles are extremely powerful, they do not travel very far, so when the nanoparticles get close to the targeted cancer cells, the alpha particles are more selective at damaging cancer cells but not surrounding cells.

Read more: http://www.nanowerk.com/news2/newsid=30558.php#ixzz2TiEg009k