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Carbon Nanotubes Enable First Step Toward Artificial Skin

Researchers at Stanford University have devised a method by which they can spray single-walled carbon nanotubes (SWNTs) onto a thin layer of silicone and create a flexible and stretchable pressure sensor.

The researchers, led by Zhenan Bao, associate professor of chemical engineering, published their work in the journal Nature Nanotechnology this week under the title "Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes."

"This sensor can register pressure ranging from a firm pinch between your thumb and forefinger to twice the pressure exerted by an elephant standing on one foot," said Darren Lipomi, a postdoctoral researcher in Bao's lab, who is part of the research team, in the Stanford article covering the research.

The researchers discovered that when they sprayed SWNTs onto silicone, the SWNTs naturally formed themselves into clumps, or “nanobundles.” When the silicone was initially stretched, those “nanobundles” aligned themselves in the direction of the stretching. On release, the nanobundles form into “nanosprings,” which in the silicone material act as electrodes.

"After we have done this kind of pre-stretching to the nanotubes, they behave like springs and can be stretched again and again, without any permanent change in shape," Bao is quoted as saying in the article.

The remarkable bit is that after the initial stretching forms the SWNTs into nanosprings, they can undergo numerous stretches without losing their electrical conductivity.

The initial aim of the research was looking not for high sensitivity, but instead to exploit the characteristics of transparency and its flexibility. However, according to Bao, they need only make some changes to the surface of the electrodes to increase its sensitivity.

A video that accompanied the Stanford press release on this story (see below) provides some of the application potential for the use of the material as an artificial skin both for robotics and artificial limbs for amputees.

With a Carbon Nanotube Glut, What Do You Do with Them?

While I was attending the EuroNanoForum 2011 conference earlier this year, I ran into an old acquaintance who works at a national nanotechnology laboratory.

He told me the tale of how a large, multinational company that produces multi-walled carbon nanotubes (MWNTs) approached the organization, wanting to pitch some ideas on how it could use carbon nanotubes. It came down to the company inventing uses for the MWNTs so it could get rid of the stuff.

The reason for desperate acts like this is that carbon nanotube producers have been on a capacity increase binge for the last few years without demand increasing, leaving the market for the stuff oversupplied to say the least.

Based on some analysis I have seen, the low, spot-pricing for MWNTs has dropped from $700/kg in 2006 to below $100/kg in 2009—and the price is expected to go down further, reaching $50/kg by next year. But truth be told, nobody buys raw carbon nanotubes. There is no market for them. Instead the market consists of sales of dispersions, master batches, and pre-pregs.

It is with this backdrop that I glanced over at a Spotlight piece in Nanowerk, entitled: “Global carbon nanotubes market—industry beckons.”

Well, if the author meant that MWNT producers are beckoning for someone to buy their glut of inventory, that title might make sense. But I don’t think that’s what he was driving at.

One could make the argument that the precipitous drop in pricing for MWNTs has made it a more attractive material, so we may be experiencing a slight shift to market pull as opposed to technology push. But let’s be serious. MWNT producers are probably at 10 percent utilization rates or below with all the new capacity they have. There’s just not enough industry using the material to constitute a beckoning.

I mean, the growth market for MWNTs appears to be in wind turbine blades and heads. That’s got to tell you something about the market’s prospects.

No, it’s not 2001 anymore, and little promotional pieces like this one kind of miss the mark a decade later.

The EC Defines a Nanomaterial: Now What?

This year I have been covering the sometimes-laughable efforts by the European Commission to define what a nanomaterial is so the Commission can develop a regulatory framework.

My views of this effort have evolved over time, and I see myself now firmly in the camp that believes arriving at a definition of nanomaterials when the science around the toxicity of nanomaterials is still so uncertain seems a counterproductive effort.

The counterargument that basically goes like this: How would one create a regulatory framework without a definition of some kind?

I suppose the simple answer to that would be to create a regulatory framework that was flexible and could be adjusted to the most recent and reliable science on the toxicity of nanomaterials. That seems a lot more sensible if one is indeed concerned about the potential threats of nanomaterials to the environment, health, and safety rather than quibbling over “how much” versus “how many” nanoparticles constitute a nanomaterial.

From what I could tell after speaking to some of the officials involved in this process, it seemed that arriving at a definition for nanomaterials was as much about public relations as about creating good regulatory policy.

That’s fine, of course, but after the EC announced its finalized definition for nanomaterials this week, it didn’t take long for the public, in the form of the European Environmental Bureau (EEB), to both express disappointment with the definition and to mock the amount of time it took to develop. So much for good public relations.

The definition itself…well, I don’t see how it helps to narrow anything, which I understand to be one of the main purposes of definitions. It would seem that the nanoparticles that are given off when your car’s tires roll along the pavement are now up for regulatory policy (“Nanomaterial” means a natural, incidental or manufactured material containing particles…”). And due to the lack of distinction between “hard” and “soft” nanoparticles in the definition, Andrew Maynard points out, “someone needs to check the micelle size distribution in homogenized milk.”

So what is the fallout from this definition? It would seem to be somewhat less than had been anticipated earlier in the year, when worries surrounded getting the definition just right because it would immediately dictate policy.

Instead, we are told that:

“Nanomaterials are not intrinsically hazardous per se but there may be a need to take into account specific considerations in their risk assessment. Therefore one purpose of the definition is to provide clear and unambiguous criteria to identify materials for which such considerations apply. It is only the results of the risk assessment that will determine whether the nanomaterial is hazardous and whether or not further action is justified.”

So basically they have created a class of materials that at the moment are not known to be intrinsically hazardous; but if some day they are, there is now a separate class for them. While some may see as this as making some sense, the sense of it eludes me.

Another Material Mimics Graphene's Capabilities

While listening to one of the better explanations I’ve heard of where we are with graphene’s capabilities in electronics applications, from Professor Ravi Silva, director of the Advanced Technology Institute at Surrey University, I saw that graphene was getting another competitor in the race for “wonder material” honors. 

You may recall from the beginning of this year how molybdenite was demonstrated to have a number of the same advantages graphene has over silicon in electronics but also has an inherent band gap.

In the joint research carried out in the labs of Helmholtz-Zentrum Dresden-Rossendorf (HZDR) linked to above, Dr. Frederik Wolff-Fabris and Dr. Jun Sung Kim came from South Korea discovered that when the metal SrMnBi2 (a mixture of strontium, manganese, and bismuth) is exposed to strong magnetic fields it behaves a lot like graphene.

In the coverage I have seen thus far for the research, which was published in the American Physical Society’s journal Physical Review Letters, I haven’t seen what characteristics the SrMnBi2 mimics of graphene, but I imagine it has to do with electron mobility.

It seems the real focus of the research was to observe various metals under a high magnetic field rather than seeking a new graphene. But because SrMnBi2 can easily be doped with foreign atoms, the researchers believe that this may allow for creating new magnets or superconductors for the material. 

It will be interesting to see if anyone pursues the graphene angle, in which case instead of the “carbon nanotechnology revolution” maybe we’ll be talking about the “SrMnBi2 nanotechnology revolution.”

A Pinch of Salt Makes All the Difference in Nanoscale Process for Hard Disks

Researchers in Singapore have developed a nanopatterning technique that enables hard disk drives to store potentially up to 3.3 Terabit/in2 of information, which is six times the recording density of current devices. 

In collaborative research between Singapore’s Institute of Materials Research and Engineering (IMRE), the National University of Singapore (NUS) and the Data Storage Institute (DSI), the researchers have been able to demonstrate data-storage capability of 1.9 Terabit/in2 and fabricated bits capable of up to 3.3 Terabit/in2 densities.

“What we have shown is that bits can be patterned more densely together by reducing the number of processing steps,” said Dr Joel Yang, the IMRE scientist who heads the project.

The process that the researchers came up with, published in the Institute of Physics journal Nanotechnology, involved the use of a high-resolution electron-beam lithography followed directly by magnetic film deposition. This essentially enabled the researchers to avoid the pattern transfer processes, such as etching and liftoff that manage to lessen pattern fidelity.

But the trick was in Yang’s discovery that by adding sodium chloride to the developed solution used in the lithography, “he was able to produce highly defined nanostructures down to 4.5 nm half pitch, without the need for expensive equipment upgrades.” 

Yang happened on this idea not during this research project but back when he was a graduate student at the Massachusetts Institute of Technology—and published it back in 2005

Nanomagnets Provide Protection from Lethal Counterfeit Drugs

A company that started off with the name SingularID over half a decade ago has long impressed me with its ability to take a nanomaterial—in this case nanomagnets—and develop a suite of tools around its physical phenomena to sell a product that helps in brand protection.

Bilcare Research acquired the small start-up back in 2007, and it seems the anti-counterfeiting technology could have a real impact in combating drug counterfeits in India, according to this recent BBC story

According to the BBC piece, counterfeit drugs are a $200 billion business whose main target continues to be poor and developing countries. What we’re talking about here is not just lost profits for the genuine drug producers, but also sometimes lethal consequences for people who need a particular drug but receive a fake one that lacks the active ingredient needed—or simply poisonous drugs.

The article goes on to explain that a number of technologies, including Bilcare’s, are under consideration for combating the counterfeit drugs. What I always found intriguing about the nanomagnet solution developed by SingularID and now marketed by Bilcare is that even they can’t make a copy of it—the nanoparticles position themselves in random patterns.

But beyond that, what always attracted me to the story of this technology is that the developers didn’t just settle with a nanomaterial and a patent and expect the world to come knocking on their door with lucrative licensing agreements. Instead, they developed an entire product that they could sell to someone. This has been surprisingly rare in the brief time that there have been nanotech companies.

The Term "Nanolargesse" Still Not in Common Usage

While nanotechnology has not been a gold mine for creating new fortunes, it’s certainly been one for “nano” being used as a prefix in quasi-portmanteaus, as evidenced by the name of this blog and nearly every nano-related start-up company for the last decade.

However, an editor for Nature’s Nanotechnology expected, when the new journal launched five years ago, that by now the term "nanolargesse" would have come into common usage to describe the huge amount of amount of money that is poured into nanotech research from governments around the world. It hasn’t.

In a new editorial that marks the fifth anniversary of the journal, we get a pretty honest and critical assessment of the state of nanotechnology’s development in the period since the publication's launch. It's somewhat surprising in its harshness, given that the fate of the publication depends somewhat on the hype within the field.

Ironically, for all the honest criticism contained within in the piece, the author apparently failed to recognize that the huge amount of government funding that is continually poured into nanotech would never be referred to as largesse.

Of course, it has been exactly that for the construction industries of countries desperate to appear like a growing economy or for marginalized material scientists who discovered by plugging in the term “nanotechnology” in the place of “surface reconstructions” they could achieve with relative ease research grants that had escaped them in the past.

But with so much riding on the “nanotechnology gravy train”—even for the governments that were serving it out and trying to exploit it as some sort of metric of their leadership—it would seem clear that nobody was going to denigrate the process with a term like largesse.

Despite my issue with the author’s seeming naiveté, commentary is not the main point of the piece. It primarily serves as an introduction to “a series of Web pages that bring together all the papers we have published in four particularly active areas—DNA nanotechnology, graphene, nanopores, and nanotoxicology.”

It is an intriguing way to organize the past five years of research. But what really caught my eye were the author’s reminiscences from the publication's launch, and how at that time papers on graphene were few and far between but those for carbon nanotubes were a regular occurrence. How that relationship has changed in five years.

Carbon Nanotubes in Form of Aerogel Enable Invisibility Cloak

Invisibility is becoming one of the more attractive features of nanomaterials. As evidenced herehere, and here.

The last link on that list brings you to research in which researchers at the University of Texas used graphene to build on the phenomena known as “plasmonic cloaking” and “mantle cloaking.”

It seems the University of Texas is at again, this time at the UT in Dallas. But in this case the researchers are using carbon nanotubes to exploit the single-beam mirage effect, photothermal deflection, to create an invisibility capability.

The research, which was published in the Institute of physics journal Nanotechnology, basically used a sheet of carbon nanotubes in the form of an aerogel to create the "invisibility cloak."

In the past, when I have written about these developments, I didn't have a video to demonstrate the invisibility effect. In covering this story, however, I came across a video of what this invisibility looks like when it operates. 

Unfortunately, I saw that ABC News covered the story as well. The way the ABC reporter approached the story really depressed me. 

Apparently, the reporter felt that he could only relate the news by making reference to Harry Potter (It's hard to write about the experiment done at the University of Texas at Dallas without invoking Harry Potter), and that he was sorry to say he could only tell the story of the breakthrough by discussing nanotechnology (If you're not into nanotechnology, read on anyhow.).

Why must every story that comes from the mainstream press on science and technology be first related through some Hollywood movie or TV show? And is it really necessary to apologize for the fact that this technology involves...technology? 

Iran Trumpets Its Nanotechnology Behind a Veil

This week Iran will be hosting its fourth annual international nanotechnology festival, Iran Nano 2011, and the PR materials have been churned out fast and furious leading up to the event.

Just about everything that has been announced is simultaneously intriguing and baffling. For example, earlier this week I read that the Secretary of Iran's Nanotechnology Initiative Council, Saeed Sarkar, was claiming that Iran was ranked 12th in the world for production of nanoscience.

Now I have no reason not to believe that claim, mainly because I am not sure I could name off the top of my head who is ranked 1 through 11, but more important, I am not sure what it means.

Could it be the production of scientific papers with reference to nanotechnology? We now know that the pursuit of this metric is often on a slippery slope. Or could it be funding? Hard to say on that one; Iran’s expenditures on nanotechnology are not as well known as some other countries. And translating funding into actual impact is probably more critical than just the amount allocated.

The main problem in ranking Iran’s place in the nanotechnology hierarchy is that of transparency: We just don’t know that much.

One of the few people I know who has visited Iran with the purpose of working on nanotechnology is Tim Harper, who offered this about Iran during an interview with Frogheart back in July:

“Iran is a different case, and it’s a place I have visited several times to discuss nanotechnologies. While the world may have some issues with the Iranian government, the scientists and business people I deal with are just like the rest of us. Iran has some great science going on, and the U.S. embargo has meant that they have had to be quite ingenious to get access to even basic instrumentation such as electron microscopes. However, there’s a large domestic market, and the Iranians are manufacturing everything from scientific instruments to nanomaterials. When the political issues are solved, I think a few people will be surprised by the level of sophistication of Iranian nanoscience.”

I suppose Harper’s view is all I really have to prevent me from considering with skepticism recent claims that researchers in Iran have developed a form of the cancer drug doxorubicin that has eliminated many of the drug’s side effects. The new formulation may be a great breakthrough, but I am not sure whether its presentation as a “cure for cancer” is just your typical run-of-the-mill hype or state-sponsored propaganda.

In either case, I wish the Iranians would avoid that kind of announcement, especially when their entire nanotechnology enterprise remains a mystery for many. Sanctions or no, science needs transparency to progress, both within and outside Iran.

Can a Polymer Membrane Be the Next Big Thing in Battery Technology?

At the end of last week, news came out of National University of Singapore's Nanoscience and Nanotechnology Initiative (NUSNNI) that an energy-storage membrane had been developed that was more cost-effective at storing energy than either rechargeable batteries or supercapacitors.

From the NUSNNI press release:

"The research team, led by Principal Investigator Dr Xie Xian Ning, used a polystyrene-based polymer to deposit the soft, foldable membrane converted from organic waste which, when sandwiched between and charged by two graphite plates, can store charge at 0.2 farads per square centimetre. This capability was well above the typical upper limit of 1 microfarad per square centimetre for a standard capacitor. The cost involved in energy storage is also drastically reduced with this invention, from about US$7 to store each farad using existing technologies based on liquid electrolytes to about US$0.62 per farad."

This is pretty amazing news, with publications including Energy & Environmental Science and Nature having already published articles this summer covering the research.

It’s also been so groundbreaking that there have been many calls to exercise caution about overoptimism. But one can’t help but hope for something to replace Li-ion battery technology, nano-enabled or not.

The application areas proposed for the membrane hit on all the favorites, like energy storage for hybrid vehicles and solar power systems.

Besides my usual caveat on these things—don’t expect much for the next few years—I am also a bit concerned that the researchers are seeking out venture capitalists to get this work into commercialization. If there’s one thing we’ve learned in the past 10 years, it’s the VC model just doesn’t get it done in nanotech. 

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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
 
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Rachel Courtland
Associate Editor, IEEE Spectrum
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