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Adoption of Graphene-Based Optical Modulator Seems Stymied by Business Not Technology

IEEE Spectrum has coverage this week on recent research conducted at the Nanoscale Science and Engineering Center at the University of California, Berkeley that demonstrated a device made of graphene can modulate light and potentially operate at speeds of 500 gigahertz.

The work was initially published in the journal Nature and demonstrates how with the application of voltage the energy state of electrons in a monolayer of graphene can be manipulated to block or allow the passage of photons, effectively modulating light.

Perhaps the most intriguing aspect of this research is how commercially attractive this material for integrated optical modulators is compared to other materials that are being considered.

The idea is that someday we will be replacing all those copper interconnects in chips with optical interconnects. Some material needed to be found that was easily compatible with complementary metal-oxide semiconductor (CMOS). Silicon modulators were too big for on-chip optical interconnects and the germanium and compound semiconductors being experimented with were not so easy to integrate into CMOS.

So, here we are. We’ve got a material that one of the researchers, Ming Liu, says should fit in easily with CMOS manufacturing.

But wait. The distressing bit of the story is the comment provided by Frank Schwierz, head of the RF & Nanoelectronics Research Group at Technical University of Ilmenau, in Germany, who, on the one hand is encouraged by the research, but on the other laments that it may take some time before we would ever see this in a device.

"This is not related to the modulator itself but rather to the fact that the semiconductor industry itself is very conservative," he is quoted as saying in the Spectrum article. "History tells us that chipmakers introduce new materials when, and only when, it is unavoidable."

Indeed. Optical interconnects on chips would be wonderful, no doubt. However, chip manufacturers may have more pressing concerns. This kind of wrinkle in capitalism and how it impacts technological advances I have mentioned before and is hardly anything new, but a bit demoralizing nonetheless.

Nanomaterial Boosts Efficiency of Salinity Power Technology

The work of Yi Cui, Associate Professor of Materials Science and Engineering at Stanford University, has garnered a great deal of interest, especially with his paper "High Performance Silicon Nanowire Field Effect Transistors" that has become the second most cited paper in the ACS journal Nano Letters over the past 10 years.

A few years back, I noted his work in replacing the lithium in the anodes of li-ion batteries with silicon nanowires and thereby increasing the battery life of a laptop to over 20 hours.

Now Cui and his colleagues have developed a material that improves on the technique of generating electricity by exploiting the difference in salinity between freshwater and saltwater.

The technique of using the combination of fresh and saltwater to generate electricity has become known as pressure-retarded osmosis and is being used in a working prototyple plant in Norway run by Statkraft

While Statkraft has claimed a goal of converting 80 percent of the available chemical energy this technique to electricity, Cui is quoted as believing that the best efficiency they can really hope for is 40 percent.

The material that Cui has developed is a manganese-dioxide nanorod that makes up the electrode, and, according to Cui, because this material offers 100 times more surface area for the sodium ions to interact with and allows those ions to attach and detach more quickly from the electrode.

The result is that Cui’s team was able to convert 74 percent of the potential energy that exists between the fresh and salt water into electricity, and, if the electrodes are brought closer together, could possibly achieve 85 percent efficiency.

Cui offers some pretty stunning calculations on how much energy could be produced if “all of the freshwater from all of the world's coastal rivers were harnessed.” He calculates that roughly 2 terawatts of electricity would be produced under such circumstances, or 13 percent of the world’s current energy demand.

Needless to say, nobody is going to undertake such a project on that scale since not only would it disturb sensitive aquatic habitats but also it would likely have large energy costs as well. 

But an outfit like Statkraft might take an interest in the new material to see if it will bump some salinity power technology over the 80 percent efficiency mark.

Building a Knowledge-based Economy on Nanotechnology Is Not that Easy

I have read, heard and even reported that resource-rich countries that dig a hole in the ground and seemingly pull out money are keen to transition their economies from exploiting natural resources to ones based on knowledge in science and technology.

It makes sense since no matter how you feel about the concept of “peak oil”, fossil fuels are a finite resource. So sooner or later that ATM in the ground will stop dispensing cash.

This reasoning has been partly behind Russia’s huge investments in making itself a player in the field of nanotechnology.

As an outsider I have marveled at the machinations this flood of cash into a Russian nanotechnology initiative has initiated. But I am merely looking in from the outside.

So I was intrigued to read an opinion piece over at Nanotech-Now written by Eugene Birger, Principal Analyst for what appears to be a news service on all things related to nanotechnology in Russia, NanoNewsNet.ru, to see what insights it would offer in Russia’s recent attempts to create a “Silicon Valley” just outside of Moscow. 

The editorial details the progress, or lack thereof, in developing the Skolkovo high-tech hub that was started last Spring. Great expectations for the project were there from the onset since it played to the Russian practice when it was part of the Soviet Union of building large and centralized technology centers.

But as is typical whenever anyone starts flashing billions of dollars around, those who should know better kind of lose their objectivity and ignore obvious obstacles to the success of the project.

For instance, Birger refers to Vadim Malkin, Managing Partner of Transitional Markets Consultancy LLP, who argues (rightly in my estimation) that there seemed to have been a lack of recognition that other regions, namely Portugal, with its tax breaks, or India, with its cheap labor, could offer stiff competition for attracting investors in a technology park.

But ultimately the real obstacle remains oil riches. It’s hard to get anyone interested in investing in modernization projects when oil is forecast to be above $120/barrel.

While strictly speaking the Skolkovo project is not part of Russia’s nanotechnology initiative, it could be indicative of what we can expect from the Russian attempts to jump start their research into nanotechnology.

First you see lots of money being announced, then you see a number of bureaucratic obstacles delaying the release of those funds, followed by high-profile agreements and memorandums of understanding that all lead to far less cash actually being spent than originally announced and MOUs that seem never to be turned into contracts.

Birger references a quote made by Russian politician Victor Chernomyrdin in 1993, which, according to Birger, has become a catch phrase in post-Soviet Russia, "We intended for something better, but it turned out just as it always does."

Time will tell with this dim assessment is applicable to both the Skolkovo project and the Russian nanotechnology initiative, but in any event we know it won’t be easy for them to be succesful.

Carbon Nanotubes Provide Reinforcement to Composites Instead of Merely Filler

I have at times made out the use of carbon nanotubes in fillers for composite resins as much a marketing ploy as it was a structural improvement.

It seems researchers of a joint research project between Applied NanoStructured Solutions LLC (ANS, Baltimore, Md.), a Lockheed Martin subsidiary, and Owens Corning (Toledo, Ohio) were not altogether satisfied either with just using carbon nanotubes in these fillers.

The researchers were frustrated that resin loading of the carbon nanotubes was limited to little more than 3% or else the filler would become to viscous. So instead they started to look for ways of using carbon nanotubes in reinforcements rather than resins.

Back in 2007 when they embarked on this project they were looking to develop a way to incorporate nanoparticles directly into the fibers themselves. Now they have done that and also managed to do it in a way that it can be dropped into composites processors.

“We have developed a way to grow carbon nanostructures on fabrics,” Dr. Tushar Shah, ANS’ chief technology officer, is quoted as saying in the article from Composites World. “We’re not making CNTs and then transferring them,” he clarifies. “This is a continuous, direct growth process, directly onto the reinforcing fibers.”

The first application area being targeted is in electronics for electromagnetic interference (EMI) shielding. But that is really just a starting off point.

Because the composites developed with this process exhibit an inherent conductivity they are likely strong candidates for structural health monitoring (SHM) applications in which the material itself could serve as an in situ nanosensor in “smart” body armor.

If this industrial partnership is successful in getting these composites into more products, I think my reflex to scoff at the use of carbon nanotubes in them will have been cured.

Viruses Enable Carbon Nanotubes to Better Conduct Electrons in Solar Cells

One of the fundamental problems in using carbon nanotubes (CNTs) for solar cell applications is that you often get a mix of  semi-conducting nanotubes and conducting (metallic) CNTs.

While a couple of years back researchers discovered that adding imperfections to CNTs used in dye-sensitized solar cells helped in their catalytic function, it did not seem to do much for their conductivity, or really make much of a marked effect on their overall efficiency.

But now Angela Belcher and her research associates at MIT, who have been using viruses to improve lithium-ion batteries, have found that they can use viruses to sort out the various nanotubes and create a better material for transporting electrons through it

The research, which was initially published in the journal Nature Nanotechnologydescribes how by the manipulation of the protein sequence of the M13 virus it created a pH switch that attracts the carbon nanotubes to it.

While the research used dye-sensitized solar cells, the researchers believe that the technique could be used with quantum-dot and organic solar cells.

It is the level of improved efficiency that is obtained through this technique that has impressed. It is reported that this method can improve the efficiency of the dye-sensitized solar cells by 30%, bringing their conversion rate to 8 to 10%. Not earth shattering numbers, but an improvement with these types of solar cells. 

In the article cited above, Prashant Kamat, a professor of chemistry and biochemistry at Notre Dame University who has done extensive work on dye-sensitized solar cell, comments, “Dye-sensitized solar cells have already been commercialized in Japan, Korea and Taiwan,” he says. “If the addition of carbon nanotubes via the virus process can improve their efficiency, “the industry is likely to adopt such processes.”

"Ground Breaking" Research in Nanotechnology Doesn't Appear to be Related to Nanotechnology At All

About 12 years ago, the world of physics was abuzz with the news that researchers led by Lene Hau had slowed down the speed of light from 186,282 miles a second to about the speed of grandma on the highway (38 miles an hour). 

Now we have news that researchers in Australia are using silicon photonic crystals to slow down light to generate individual pairs of photons.

The device the researchers from the Centre of Excellence for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS) nodes at the University of Sydney and Macquarie University developed is 100 microns long, making it 100 times smaller than the one-centimeter devices used by other groups.

Great! Chapeau…and all the rest. But could someone explain to me how this story constitutes research into nanotechnology as the headline states. I became even more bewildered when the article claimed that the device is on the nanoscale. I don’t get it 100 microns is small for sure, but 100 microns is equal to 100,000 nanometers, just sayin’.

I do not know where the research was originally published so I don’t have any place to check this information. Maybe there is some kind of explanation for it being considered a “nanotechnology-related” story. I’d be glad if anyone could comment with an explanation. 

But then again perhaps the market analysis and investment folks are not the only ones engaged in pointlessly hyping nanotechnology. It’s being given credit for a development that apparently is more within the field of photonics than nanotechnology, and is being plastered all over Twitter like the biggest breakthrough in nanotechnology since…well, ever.

Will Science or Politics Ultimately Define Nanotechnology?

Recently I reported on the strained efforts of an EU commission to define nanomaterials that could possilby shape nanotech regulations into the foreseeable future.

At the time I wrote the article, my thought was that for all of their struggle on deciding whether a nanomaterial was best defined as “how many” nanoparticles or “how much” it didn’t really seem to address whether there was in fact any risk from either.

Andrew Maynard commented on the entry and promised an analysis of the situation, which we now have.

Maynard’s insights get far deeper into the fundamental problems that occur when bureaucrats attempt to define nanotechnology. According to Maynard, what you risk ending up with is politics dictating health and safety regulations rather than science.

And the politics in this instance are a powder keg of misinformation. As Maynard relates in his analysis, “This situation has been exacerbated by the underlying assumption that nanomaterials present a unique risk.  And all too often the science has been co-opted to support this position rather than to evaluate it.”

We are given the example of how European Commission Directorate General for Health and Consumers Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) last year published a paper, which Maynard describes as one containing “a palpable sense of the authors contorting themselves to serve an assumption that doesn’t align well with the facts.” He adds, “It’s no surprise therefore that the conclusions they reach are peppered with caveats that seem to call into question the assumption on which their task was based.”

Maynard points out that just five years ago he was among the chorus of those calling for a definition of nanomaterials. But it seems the more science reveals about the properties and possible risk of nanomaterials and nanoparticles the less beneficial it will be to arrive at this definition.

“Five years ago, the state of the science was such that it still seemed feasible that a regulatory definition of nanomaterials could be crafted.  Today, that hope is looking increasingly tenuous.  We know that size matters when it comes to understanding the risks presented by materials generally – and particles more specifically – and that characteristics such as physical form and chemistry are also important.  But these are relevant from diameters of tens of micrometers – where particles begin to be able to penetrate organisms – down to the nanometer size range.  At different length scales, different material-biology interactions lead to different mechanisms of action that have the potential to cause harm in different ways.  But there are no rules that are generalizeable to the nanoscale specifically – that much the science is clear on.  And this alone calls into question the scientific-basis of enforcing nanoscale-specific regulations.”

This is a crucial point and is linked to the idea that inspired one of my recent blogs in which I point out that there now exists a commonplace knee-jerk reaction to the term nanotechnology that is uninformed about the most recent science looking into the risks of nanomaterials.

I myself have bemoaned how politics are taking on a dangerously influential role in guiding the question of nanotechnology’s risk some years ago. I fear that science is not in a fair fight when it comes up against those who are expert at manipulating a political debate.

Is the Future of Nanotechnology Limited to Three Nanometers?

I was a bit stunned when I saw that Professor Mike Kelly at Cambridge University for Advanced Photonics and Electronics had claimed that structures with dimensions three nanometers or less could not be mass-produced

I became somewhat relieved when I clicked on the source story for the above link to discover that Kelly had added that this 3-nm limit only applied to “using a top-down approach.” 

My sense of relief was short lived when it seems in the source article that Kelly wasn’t really sure that a bottom-up approach could do it either since the processes used were too prone to unpredictable defects.

So, I thought I might find some respite in the original paper published by the UK’s Institute of Physics IOP (The paper is currently free if you register on the site).

The only real hopeful bit that escapes Kelly’s rather pessimistic theorem is that he doesn’t specifically discuss bottom-up approaches to manufacturing structures below 3nm, except to say, “There is a vanishing probability of generating a wide-area defect-free (especially line-defect-free) arrays.”

The main thrust of Kelly’s argument is one that is not altogether that radical, which is that you may be able to fabricate one-off structures that have dimensions below 3nm but you won’t be able to duplicate that in a full-scale manufacturing process.

While most have noted the difficulty of ramping up to a manufacturing process, or implied that new techniques would be developed to enable these manufacturing processes, Kelly is not quite as hopeful. From the IOP paper: 

“If this (top-down) manufacturing process is to be based on the most modern forms of deposition (including epitaxy), e-beam or ultra-deep UV lithography and precision etching, the mainstay of microelectronics and optoelectronics fabrication, then there are strict limits described below for which one-off fabrication is possible, but manufacture is not.”

So, metaphorically speaking Kelly has laid down the gauntlet, challenging the nanoscience community to either disprove his theorem, or, if they cannot, to start developing techniques for manufacturability rather than continuing to develop structures that will never be able to be manufactured.

"If I am wrong, and a counterexample to my theorem is provided, many scientists would be more secure in their continued working, and that is good for science,” says Kelly. "If more work is devoted to the hard problem of understanding just what can be manufactured and how, at the expense of more studies of things that cannot be manufactured under the conditions of the present theorem, then that too is good for science and for technology."

The Etch-a-SketchTM of Microscopy Creates Single Electron Transistors

Many of us grew up playing with an Etch-a-SketchTM toy in which a stylus cuts into an aluminum powder that coats in the inside of the toy’s screen revealing the dark inside the toy.

About three years ago, researchers at the University of Pittsburgh, led by Jeremy Levy, a professor of Physics and Astronomy in Pitt's School of Arts and Sciences, developed a technique that employed the tip of an atomic force microscope to etch patterns into the interface between two materials: a crystal of strontium titanate and a 1.2 nanometer-thick layer of lanthanum aluminate. At the time, the researchers likened the technique to a kind of microscopic Etch-a-SketchTM since like the toy it can erase the devices it makes and start anew.

Jump ahead three years to today and researchers from Pitt, University of Wisconsin at Madison and HP Labs, again led by Levy, have used the Etch-a-SketchTM technique to build a single-electron transistor, which they have dubbed SketchSET (sketch-based single electron transistor).

The research, which was initially published in the journal Nature Nanotechnologymarks the first time that a single-electron transistor has been made from oxide materials.

The foundation of the transistor is a conducting oxide “island” only 1.5nm in diameter that serves to have electrons tunnel resonantly between the source and drain electrodes. The island can only contain 0, 1 or 2 electrons, which provides it with unique conducting capabilities.

In addition to being extremely sensitive to electric charge, the oxide materials that make up the transistor possess ferroelectricity properties, which make it possible for the transistor to serve as a solid-state memory. These ferroelectric properties could also make it attractive as nanoscale charge and force sensor.

In the grander scheme of things, this transistor is being considered another tool for creating quantum computers. In fact, since last year Levy has been part of a U.S. Air Force Office of Scientific Research’s Multi-University Research Initiative (MURI) program to build a semiconductor for use in quantum super computers

 

Silver Nanoparticles Enable Palladium to Become More Effective Catalyst for Fuel Cells

In the continuing saga of nanotechnology’s application for fuel cells in this blog (see here and here) I have come to realize that there is a fervent belief among some that the reason we don’t have fuel cells powering our automobiles today is the result of a conspiracy among certain interests (presumably the oil industry) to block their use.

I really try to avoid taking sides in this rather fruitless debate. Instead I merely point out how nanotechnology has sometimes failed or succeeded in its intended applications for fuel cells. In either case, I try to put it into context. The current context by the way is that fuel cells power all sorts of things today, but when it comes to automobiles it is only for prototypes.

So, with this latest research coming out of Oxford University in the UK I am going to avoid pronouncements that it will usher in fuel-cell powered cars, or not.

The research, which was originally published in the journal Nature Nanotechnology, has shown how by applying an atomic layer of palladium on top of silver particles a catalyst is created for turning formic acid into hydrogen.

Despite all sorts of interminable calculations to the contrary, hydrogen is flammable and is not as easy or as safe to store as formic acid. As the Nature Nanotechnology abstract explains, “Formic acid (HCOOH) has great potential as an in situ source of hydrogen for fuel cells, because it offers high energy density, is non-toxic and can be safely handled in aqueous solution.”

Edman Tsang of Oxford University’s Department of Chemistry adds in the article reporting on the research “that the storage and handling of organic liquids, such as formic acid, is much easier and safer than storing hydrogen.” (Do I really need to add a video of hydrogen gas exploding?)

The main achievement of the research was the determination that the underlying silver nanoparticles enhance the catalytic properties of palladium. Tsang believes that these improved catalysts could “enable the production of hydrogen from liquid fuel stored in a disposable or recycled cartridge, creating miniature fuel cells to power everything from mobile phones to laptops.” However, I still argue carrying around a container for formic acid in your laptop or cell phone is a bit of a hard sell.

Even Tsang concedes, “There are lots of hurdles before you can get a real device, but we are looking at the possibility of using this new technology to replace lithium battery technology with an alternative which has a longer lifespan and has less impact on the environment.”

I’d argue that even if you got all the engineering perfectly sorted, you would still face just some commercial market realities that in the current environment would be hard to overcome.

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Nanoclast

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

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