David Kirkpatrick

August 25, 2010

Making nano-brushes even smaller

Filed under: Science — Tags: , , , , , , — David Kirkpatrick @ 11:52 am

Now this is a nanotech development that can lead to real-world applications.

From the link:

In their latest series of experiments, Duke University engineers have developed a novel approach to synthesize these nano-brushes, which could improve their versatility in the future. These polymer brushes are currently being used in biologic sensors and microscopic devices, such as microcantilevers, and they will play an important role in the future drive to miniaturization, the researchers said.

Nano-brushes are typically made of  grown on flat surfaces with strands of the molecules growing up and out from a surface, much like hairs on a brush. Polymers are large man-made molecules ubiquitous in the manufacture of everyday products.

An atomic force microscopy topographic image of the nano-brushes. The relative heights of the brushes can be tailored by changing the substrate and initiators. Credit: Stefan Zauscher, Pratt School of Engineering

August 9, 2010

Is solar power cheaper than nuclear?

Filed under: Business, Science, Technology — Tags: , , , , — David Kirkpatrick @ 9:04 pm

Surprisingly, maybe so.

From the link:

One of the issues associated with shifting from using fossil fuels to alternative energy sources is the cost. While adherents of alternative energy tout its benefits, many are skeptical, pointing out that such alternatives are just too expensive. Advocates of nuclear power point out that it is less polluting (if you don’t count storage of spent fuel) than fossil fuels, and that it costs less than alternatives like solar power.

A new study out of Duke University, though, casts doubt on the idea that  is cheaper than . Using information from North Carolina, the study shows that solar power may be more cost efficient than nuclear power. With costs dropping on the production of photovoltaic cells, and with solar cells becoming increasingly efficient, it appears that — in North Carolina at least — solar installations offer a viable alternative to nuclear power, which is the source for about 20% of the electricity in the U.S.

June 2, 2010

Copper nanowires may improve solar cells and displays

This is an interesting use of nanotech because it looks like it might be market-ready much sooner than later, and as team member Benjamin Wiley puts it, “If we are going to have these ubiquitous electronics and solar cells we need to use materials that are abundant in the earth’s crust and don’t take much energy to extract.”

Also from the link:

A team of Duke University chemists has perfected a simple way to make tiny copper nanowires in quantity. The cheap conductors are small enough to be transparent, making them ideal for thin-film solar cells, flat-screen TVs and computers, and flexible displays.

“Imagine a foldable iPad,” said Benjamin Wiley, an assistant professor of chemistry at Duke. His team reports its findings online this week in .

Nanowires made of  perform better than carbon nanotubes, and are much cheaper than silver nanowires, Wiley said

May 12, 2010

DNA-based logic chips

Very cool and very fascinating in terms of extreme mass production.

The release:

DNA could be backbone of next generation logic chips

IMAGE: This is Duke University’s Chris Dwyer.

Click here for more information.

DURHAM, N.C. – In a single day, a solitary grad student at a lab bench can produce more simple logic circuits than the world’s entire output of silicon chips in a month.

So says a Duke University engineer, who believes that the next generation of these logic circuits at the heart of computers will be produced inexpensively in almost limitless quantities. The secret is that instead of silicon chips serving as the platform for electric circuits, computer engineers will take advantage of the unique properties of DNA, that double-helix carrier of all life’s information.

In his latest set of experiments, Chris Dwyer, assistant professor of electrical and computer engineering at Duke’s Pratt School of Engineering, demonstrated that by simply mixing customized snippets of DNA and other molecules, he could create literally billions of identical, tiny, waffle-looking structures.

Dwyer has shown that these nanostructures will efficiently self-assemble, and when different light-sensitive molecules are added to the mixture, the waffles exhibit unique and “programmable” properties that can be readily tapped. Using light to excite these molecules, known as chromophores, he can create simple logic gates, or switches.

These nanostructures can then be used as the building blocks for a variety of applications, ranging from the biomedical to the computational.

IMAGE: This is a closeup of a waffle.

Click here for more information.

“When light is shined on the chromophores, they absorb it, exciting the electrons,” Dwyer said. “The energy released passes to a different type of chromophore nearby that absorbs the energy and then emits light of a different wavelength. That difference means this output light can be easily differentiated from the input light, using a detector.”

Instead of conventional circuits using electrical current to rapidly switch between zeros or ones, or to yes and no, light can be used to stimulate similar responses from the DNA-based switches – and much faster.

“This is the first demonstration of such an active and rapid processing and sensing capacity at the molecular level,” Dwyer said. The results of his experiments were published online in the journal Small. “Conventional technology has reached its physical limits. The ability to cheaply produce virtually unlimited supplies of these tiny circuits seems to me to be the next logical step.”

DNA is a well-understood molecule made up of pairs of complimentary nucleotide bases that have an affinity for each other. Customized snippets of DNA can cheaply be synthesized by putting the pairs in any order. In their experiments, the researchers took advantage of DNA’s natural ability to latch onto corresponding and specific areas of other DNA snippets.

Dwyer used a jigsaw puzzle analogy to describe the process of what happens when all the waffle ingredients are mixed together in a container.

“It’s like taking pieces of a puzzle, throwing them in a box and as you shake the box, the pieces gradually find their neighbors to form the puzzle,” he said. “What we did was to take billions of these puzzle pieces, throwing them together, to form billions of copies of the same puzzle.”

IMAGE: These are many waffles.

Click here for more information.

In the current experiments, the waffle puzzle had 16 pieces, with the chromophores located atop the waffle’s ridges. More complex circuits can be created by building structures composed of many of these small components, or by building larger waffles. The possibilities are limitless, Dwyer said.

In addition to their use in computing, Dwyer said that since these nanostructures are basically sensors, many biomedical applications are possible. Tiny nanostructures could be built that could respond to different proteins that are markers for disease in a single drop of blood.

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Dwyer’s research is supported by the National Science Foundation, the Air Force Research Laboratory, the Defense Advanced Research Projects Agency and the Army Research Office. Other members of the Duke team were Constantin Pistol, Vincent Mao, Viresh Thusu and Alvin Lebeck

October 13, 2009

Web 2.0 and privacy

As it turns out — not, surprisingly I might add — not so much.

The release:

Looking for privacy in the clouds

DURHAM, N.C. — Millions of Internet users have been enjoying the fun — and free — services provided by advertiser-supported online social networks like Facebook. But Landon Cox, a Duke University assistant professor of computer science, worries about the possible down side — privacy problems.

When people post pictures or political opinions to share with their friends, they’re actually turning them over to the owners of the network as well.

“My concern is that they’re under the control of a central entity,” Cox said. “The social networks currently control all the information that users throw into them. I don’t think that’s necessarily evil. But it raises some concerns.”

For instance, MIT student experimenters have demonstrated the ability to sneak in and download more than 70,000 Facebook profiles. And a BBC technology program also showed how such personal information could be stolen.

“A disgruntled employee could leak information about social network users,” Cox said. “They could also become attractive targets for hackers and other computer ne’er-do-wells.”

Though users may not have caught this when they clicked to accept a site’s terms of service, they’ve largely signed away the rights to their own data by joining an Online Social Network. “These rights commonly include a license to display and distribute all content posted by users in any way the provider sees fit,” Cox said.

To delve deeper into these issues and begin the search for alternatives, Cox recently won a $498,000, three-year grant from the National Science Foundation. The funding is part of the federal stimulus package called the American Recovery & Reinvestment Act of 2009 (ARRA). He and two of his graduate students, Amre Shakimov and Dongtao Liu, are collaborating closely with Ramon Caceres at AT&T Labs in Florham Park, N.J., which is also a major supporter.

“What the grant will do is fund research into alternatives for providing social networking services that don’t concentrate all this information in a single place,” he said. Cox’s notion is instead to create what network architects would call a “peer-to-peer” system architecture in which information is spread out. Being distributed, individual data is thus harder to steal or otherwise exploit.

“The basic idea is that users would control and store their own information and then share it directly with their friends instead of it being mediated through a site like Facebook. And there are some interesting challenges that go along with decomposing something like Facebook into a peer-to-peer system.

“Facebook is a great service because it’s highly available and really fast. When you break something into thousands and millions of different pieces instead, you’d want to try to recreate the same availability and performance. That’s the research challenge we’re going to be looking at over the next three years.”

Cox proposed three possible options in a report for the Association for Computing Machinery’s Workshop for Online Social Networks in Barcelona in August 2009. In each, users would load their personal information into what is called a “Virtual Individual Server,” or VIS.

One option would host each social network user’s VIS on his or her own desktop. “But the problem with desktop machines is that they go down all the time,” Cox said. “When desktops are shut off they are not available.”

An alternative idea is to distribute VISs within redundant “clouds” of servers such as those offered by the Amazon Elastic Computer Cloud. “Amazon will run little computers on your behalf out in their infrastructure,” Cox said. “The nice thing about that is the service will never go down. But the problem is that it’s very expensive. It costs about $50 a month to have just one server out in the cloud.”

A third notion is called “hybrid decentralization.” The idea is to keep VISs on desktops when possible but switch to the more costly and reliable cloud distribution option when individual desktops go offline.

“So there are these different tradeoffs,” Cox said. “Users can try to put their information in clouds of servers, which are going to be highly available but expensive. Or they could try to store it on their own machines, which would be cheap but subject to service interruptions.”

Under his NSF stimulus grant, Cox will be able to pay Shakimov and Liu for three years and fund some of his own work to explore those options. Other AT&T Labs research participants besides Caceres are Alexander Varshavsky and Kevin Li. Amazon is also providing equipment support.

“The research will point in a couple of directions,” he said. “Can we get a desktop machine to intelligently switch over to a cloud? Can we reduce the cost by only using a cloud when the desktop is not available?”

Or perhaps the same information can be put in a number of places in the hope that at least one of those computers is always working. “So in addition to serving my own stuff I might ask my friends to serve my stuff as well,” Cox said.

“The problem there is that now you’re trusting somebody else to serve and store your data. We have some interesting challenges ahead.”

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January 22, 2009

Semiconducting nanotubes produced

Very cool news. This is the sort of progress in nanotech that could change an industry — electronics in this case.

The release:

Semiconducting nanotubes produced in quantity at Duke

DURHAM, N.C. — After announcing last April a method for growing exceptionally long, straight, numerous and well-aligned carbon cylinders only a few atoms thick, a Duke University-led team of chemists has now modified that process to create exclusively semiconducting versions of these single-walled carbon nanotubes.

The achievement paves the way for manufacturing reliable electronic nanocircuits at the ultra-small billionths of a meter scale, said Jie Liu, Duke’s Jerry G. and Patricia Crawford Hubbard Professor of Chemistry, who headed the effort.

“I think it’s the holy grail for the field,” Liu said. “Every piece is now there, including the control of location, orientation and electronic properties all together. We are positioned to make large numbers of electronic devices such as high-current field-effect transistors and sensors.”

A report on their achievement, co-authored by Liu and a team of collaborators from his Duke laboratory and Peking University in China, was published Jan 20, 2009 in the research journal Nano Letters. Their work was funded by the United States Naval Research Laboratory, the National Science Foundation of China, carbon nanotube manufacturer Unidym Inc., Duke University and the Ministry of Science and Technology of the People’s Republic of China.

Liu has filed for a patent on the method. A post doctoral researcher in his laboratory, Lei Ding, was first author of the new report as well as the previous study http://news.duke.edu/2008/04/stnanotubes.html published April 16, 2008, in the Journal of the American Chemical Society (JACS).

That earlier JACS report described how the researchers coaxed forests of nanotubes to form in long, parallel paths that will not cross each other to impede potential electronic performance. Their method grows the nanotubes on a template made of a continuous and unbroken kind of single quartz crystal used in electronic applications. Copper is also used as a growth promoter.

Carbon nanotubes are sometimes called “buckytubes” because their ends, when closed, take the form of soccer ball-shaped carbon-60 molecules known as buckminsterfullerines, or “buckyballs.” The late Richard Smalley, who headed the Rice University laboratory where Liu was based before coming to Duke, shared a Nobel Prize for synthesizing buckyballs.

In addition to being especially tiny, those nanotubes offer other advantages — including reduced heat output and higher frequency operation — over current materials used to make miniaturized electronic components such as transistors, said Liu. “Operating at higher frequencies means they would be much better devices for wireless communications,” he added.

But the April 2008 JACS report left one unresolved issue blocking use of such numerous, straight and well-aligned nanotubes as electronic components. Only some of the resulting nanotubes acted electronically as semiconductors. Others were the electronic equivalent of metals. To work in transistors, the nanotubes must all be semiconducting, Liu said.

In their new Nano Letters report, the researchers announced success at achieving virtually all-semiconductor growth conditions by making one modification. In their earlier work they had used the alcohol ethanol in the feeder gas to provide carbon atoms as building blocks for the growing nanotubes. In the new work they tried various ratios of two alcohols — ethanol and methanol — combined with two other gases they also used previously — argon and hydrogen.

“We found that by using the right combination of the two alcohols with the argon and hydrogen we could grow exclusively semiconducting nanotubes,” Liu said. “It was like operating a tuning knob.” Chemically inert argon gas was used to provide a steady feed of the ethanol and methanol, with hydrogen to keep the copper catalyst from oxidizing.

After making the nanotubes by the chemical vapor deposition method in a small furnace set to a temperature of 900 degrees Celsius, the researchers assembled some of them into field-effect transistors to test their electronic properties.

“We have estimated from these measurements that the samples consisted of 95 to 98 percent semiconducting nanotubes,” the researchers reported.

As a double-check, the scientists also subjected some nanotubes to Raman spectroscopy, an analytical technique that can differentiate semiconducting and metallic properties by studying how materials interact with various types of lasers.

According to the new Nano Letters report, the introduction of methanol to complement ethanol also shrunk the diameters of the resulting nanotubes and improved their atomic alignments with the underlying quartz crystal.

The resulting nanotubes can only be seen with exceptionally high magnification devices like scanning electron and atomic force microscopes. Whether the hollow carbon cylinders are metallic or semiconducting is a matter of their three dimensional alignments in space — a trait scientists call “chirality.”

The group’s next challenge will be to understand at an atomic level how “just so” tuning of growth gas mixtures resulted in the right chirality to produce exclusively semiconducting nanotubes. The researchers are also wondering whether another combination might produce all-metallic nanotubes.

“We want to be able to control that chirality,” he said.

 

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Other authors of the Nano Letters report include Alexander Tselev, Dongning Yuan and Thomas McNicholas at Duke, and Yan Li, Jinyong Wang and Haibin Chu at Peking University.

 

January 16, 2009

The latest in cloaking tech

Haven’t blogged on this subject in a while. It’s always fun to cover, though.

The release:

Next generation cloaking device demonstrated

IMAGE: Pictured is the new cloak with bump, left, and the prototype, right.

Click here for more information. 

DURHAM, N.C. – A device that can bestow invisibility to an object by “cloaking” it from visual light is closer to reality. After being the first to demonstrate the feasibility of such a device by constructing a prototype in 2006, a team of Duke University engineers has produced a new type of cloaking device, which is significantly more sophisticated at cloaking in a broad range of frequencies.

The latest advance was made possible by the development of a new series of complex mathematical commands, known as algorithms, to guide the design and fabrication of exotic composite materials known as metamaterials. These materials can be engineered to have properties not easily found in natural materials, and can be used to form a variety of “cloaking” structures. These structures can guide electromagnetic waves around an object, only to have them emerge on the other side as if they had passed through an empty volume of space.

IMAGE: This is David R. Smith with the new cloak device.

Click here for more information. 

The results of the latest Duke experiments were published Jan. 16 in the journal Science. First authors of the paper were Duke’s Ruopeng Liu, who developed the algorithm, and Chunlin Li. David R. Smith, William Bevan Professor of electrical and computer engineering at Duke, is the senior member of the research team.

Once the algorithm was developed, the latest cloaking device was completed from conception to fabrication in nine days, compared to the four months required to create the original, and more rudimentary, device. This powerful new algorithm will make it possible to custom-design unique metamaterials with specific cloaking characteristics, the researchers said.

“The difference between the original device and the latest model is like night and day,” Smith said. “The new device can cloak a much wider spectrum of waves — nearly limitless — and will scale far more easily to infrared and visible light. The approach we used should help us expand and improve our abilities to cloak different types of waves.”

Cloaking devices bend electromagnetic waves, such as light, in such a way that it appears as if the cloaked object is not there. In the latest laboratory experiments, a beam of microwaves aimed through the cloaking device at a “bump” on a flat mirror surface bounced off the surface at the same angle as if the bump were not present. Additionally, the device prevented the formation of scattered beams that would normally be expected from such a perturbation.

The underlying cloaking phenomenon is similar to the mirages seen ahead at a distance on a road on a hot day.

“You see what looks like water hovering over the road, but it is in reality a reflection from the sky,” Smith explained. “In that example, the mirage you see is cloaking the road below. In effect, we are creating an engineered mirage with this latest cloak design.”

Smith believes that cloaks should find numerous applications as the technology is perfected. By eliminating the effects of obstructions, cloaking devices could improve wireless communications, or acoustic cloaks could serve as protective shields, preventing the penetration of vibrations, sound or seismic waves.

“The ability of the cloak to hide the bump is compelling, and offers a path towards the realization of forms of cloaking abilities approaching the optical,” Liu said. “Though the designs of such metamaterials are extremely complex, especially when traditional approaches are used, we believe that we now have a way to rapidly and efficiently produce such materials.”

With appropriately fine-tuned metamaterials, electromagnetic radiation at frequencies ranging from visible light to radio could be redirected at will for virtually any application, Smith said. This approach could also lead to the development of metamaterials that focus light to provide more powerful lenses.

The newest cloak, which measures 20 inches by 4 inches and less than an inch high, is actually made up of more than 10,000 individual pieces arranged in parallel rows. Of those pieces, more than 6,000 are unique. Each piece is made of the same fiberglass material used in circuit boards and etched with copper.

The algorithm determined the shape and placement of each piece. Without the algorithm, properly designing and aligning the pieces would have been extremely difficult, Smith said.

 

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The research was supported by Raytheon Missile Systems, the Air Force Office of Scientific Research, InnovateHan Technology, the National Science Foundation of China, the National Basic Research Program of China, and National Science Foundation of Jiangsu Province, China.

Others members of the research team were Duke’s Jack Mock, as well as Jessie Y. Chin and Tie Jun Cui from Southeast University, Nanjing, China.

November 6, 2008

Gold nanostars

Very cool, and looks to have some great applications.

The release:

Gold nanostar shape of the future

DURHAM, N.C. – Rods, cones, cubes and spheres – move aside. Tiny gold stars, smaller than a billionth of a meter, may hold the promise for new approaches to medical diagnoses or testing for environmental contaminants.

While nanoparticles have been the rage across a wide spectrum of sciences, a new study by Duke University bioengineers indicates that of all the shapes studied to date, stars may shine above all the rest for certain applications.

The key is light, and how that light reflects off the particles. Compared to the other shapes, nanostars can dramatically enhance the reflected light, the Duke scientists found. This increases their potential usefulness as a tracer, label, or contrast agent.

Since the researchers also found that the size and shape of the nanostars affect the spectrum of reflected light, they believe that these tiny nanostars can also be “tuned” to identify particular molecules or chemicals.

“To our knowledge, this is the first report of the development and use of gold nanostars as labels for molecular detection and description of their controlled synthesis with different sizes and shapes” said Chris Khoury, lead author of a paper published on-line in the Journal of Physical Chemistry. Khoury is a graduate student in biomedical engineering working in the laboratory of senior researcher Tuan Vo-Dinh, R. Eugene and Susie E. Goodson Distinguished Professor of Biomedical Engineering and director of The Fitzpatrick Institute for Photonics at Duke.

In the Duke experiments, the nanostars were used in conjunction with a phenomena first described in the 1970s known as surface-enhanced Raman scattering (SERS). When light, usually from a laser, is shined on a sample, the target molecule vibrates and scatters back in its own unique light, often referred to as the Raman scatter. However, this Raman response is extremely weak. When the target molecule is coupled with a metal nanoparticle or nanostructure, the Raman response is greatly enhanced by the SERS effect –often by more than a million times, Vo-Dinh said.

In the early 1980s, while at the Oak Ridge National Laboratory, Tenn., Vo-Dinh and colleagues were among the first to demonstrate that SERS could be put into practical use to detect chemicals including carcinogens, environmental pollutants, and early markers of disease. Now at Duke, Vo-Dinh is pushing the boundaries of the SERS technology by designing a variety of unique types and shapes of metal nanoparticles that can be used as SERS labels for chemical and biomedical detection.

“We are trying to understand which type of nanostructures will give us the optimal signal so we can use them to monitor trace amounts of pollutants or detect diseases in their earliest stage” Vo-Dinh said. “This study is the first demonstration that these nanostars can enhance the effect of SERS to produce strong and unique signatures, like ‘optical fingerprints.'”

Khoury “grew” the nanostars by mixing miniscule gold particle seeds in a growth solution. As more gold was added to the solution, protrusions began to sprout from the central core. Additional gold increased the size of the entire particle.

“These experiments demonstrate that it is possible to vary the size and shape of the nanostars in a controlled fashion by adjusting the volume of gold seeds added to the growth solution,” Khoury said. “We found that variations in star size changed the reflected light, which hints toward the tuning capabilities that can be exploited by SERS technology.”

For such studies, or those involving environmental contaminants, a dye would be attached to the nanostars and mixed with the sample to be tested. The sample would then be placed under a microscope and hit with a burst of laser energy. Sensors would pick up the Raman scattering and interpret the unique optical fingerprint.

Khoury said that nanostars are small enough to pass through cell walls into the interior of the cell, which would make them an effective method for molecular diagnostics. Nanostars could be attached to an antibody to search for antigens, or coupled with a dye to improve the effectiveness of different imaging tests.

While silver enhances the Raman scattering more effectively, gold was chosen as the metallic base of the current nanoparticle because it is a stable metal that doesn’t cause immune system reactions within the body. Unlike silver, it also does not oxidize in samples.

Vo-Dinh research group at Duke is currently developing novel techniques for chemical detection and medical diagnostics using SERS. Vo-Dinh said that since each SERS label molecule has its own unique optical fingerprint, theoretically a single probe could be created that could detect an array of different cancers, for example, or different environmental toxins.

 

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The research was supported by the National Institutes of Health.

July 17, 2008

C-level finance execs not optimistic

Filed under: Business — Tags: , , , — David Kirkpatrick @ 12:19 am

The Duke University/CFO magazine Global Business Outlook Survey finds finance executives looking for a prolonged downturn.

Here’s some of the numbers from the survey:

The fact that 53 percent of finance executives responding to this quarter’s Duke University/CFO magazine Global Business Outlook Survey are less optimistic than they were three months ago can be seen as good news only when compared with the whopping 72 percent who said last quarter that they were less optimistic than they were at the start of the year. But even though CFOs are not quite as down as they were in April, they’re hardly thrilled with the economic picture. In fact, many are taking significant steps to control costs as they prepare for a lengthy downturn.

Seventy-one percent of finance executives say the U.S. economy will not begin to recover until 2009 or later, and 30 percent say they don’t expect a rebound until at least the second half of next year. CFOs are forecasting minimal growth in earnings and capital spending over the next 12 months. About 40 percent of them plan to delay or cancel expansion plans, and roughly the same number have initiated cost-cutting programs.

And here’s a link to a one-page PDF charting the results.

April 24, 2008

Headway toward nanoprocessing

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 8:25 pm

From KurzweilAI.net:

Aligned nanotube swarms may lead to nanoprocessors
KurzweilAI.net, April 24, 2008

Duke University chemists have found a way to grow swarms of long, straight cylinders only a few atoms thick in very large numbers by using the crystal structure of a quartz surface as a template.

These single-walled carbon nanotubes also follow parallel paths as they grow, so they don’t cross each other to potentially impede electronic performance. Carbon nanotubes can act as semiconductors and could thus further scale-down circuitry to nanometer features.

The availability of forests of identical nanotubes would allow future nanoengineers to bundle them onto multiple ultra-tiny chips that could operate with enough power and speed for nanoprocessing, using less-expensive semiconductor wafers normally used in computer chips.

Source: Nanotubes grown straight in large numbers, Duke University