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Deeper Patterns and Easier Process Comes with New Etching Technique

Improved etching techniques have been making their way into the science journals of late.

Earlier this month, researchers from the University of Pittsburgh published their work in using DNA origami to both promote and inhibit the etching of SiO2 at the single-molecule level.

Now researchers at Argonne Center for Nanoscale Materials and Energy Systems Division have published two studies on a technique they have developed called sequential infiltration synthesis (SIS), which builds on long-standing lithography techniques but could be a real breakthrough in the field, according to the researchers.

The research, which was led by Seth Darling and published in two journals—Journal of Materials Chemistry and the Journal of Physical Chemistry C—involved developing a way by which to strengthen the delicate resist film to the extent that it no longer needs the intermediate mask.

What this translates into is a capability not only to circumvent all the complexities brought on by the use of an intermediate mask, but also to etch a pattern with greater depth and fidelity.

The SIS technique involves the controlled growth of inorganic materials with polymer films that can be built into complex, 3-D structures.

“It's possible we might be able to create very narrow features well over a micron deep using only a very thin, SIS-enhanced etch mask, which from our perspective would be a breakthrough capability," says Darling.

The researchers are looking at expanding the capabilities of the technique by combining SIS with block polymers to make features even smaller than those possible with e-beam lithography.

"This opens a wide range of possibilities," said Argonne chemist Jeff Elam, who helped create the process. "You can imagine applications for solar cells, electronics, filters, catalysts—all sorts of different devices that require nanostructures, but also the functionality of inorganic materials."

Quantum Dot-Based Infrared Materials Gets DARPA Contract

Massachusetts-based QD Vision announced this week that it had been awarded a $900,000 DARPA contract to build two prototype devices based on its quantum dot-based infrared material.

According to published reports, QD Vision “will deliver to DARPA a device with quantum dots as an emissive layer in an electroluminescent electronic device application, and a second, photoluminescent device that is based on a film that is activated by external light sources.”

"This program will leverage QD Vision's experience in developing stable, efficient IR materials for tactical applications," said Jason Carlson, President and CEO of QD Vision. "This is our second DARPA Program as a prime contractor, and we are excited to demonstrate these novel materials in two distinct modes of operation."

This most recent contract follows a US $22 million funding round received just this past May. So, for the company to get a nearly $1 million DARPA contract in just three months must have caused a sigh of relief in the investors.

To get a great backgrounder on the development of quantum dots for application in infrared detectors I refer you to this article written last year by Edward Sargent here on the pages of Spectrum.

In the article, Sargent points out just how quickly infrared detectors based on quantum dots are developing into commercial devices:

"Much closer to commercial development are quantum dots that are exquisitely sensitive to faint infrared light. With only a few years of research behind them, these devices now perform as well as the best traditional infrared detectors."

It appears that commercial development might have been closer than Sargent had even imagined. Granted, it's only a contract for defense department prototypes, but it's a sale nonetheless.

Nanotechnology's Role in the Lithium-ion Battery Anode and Cathode

A recent story in Spectrum covers the commercially promising work being done in using silicon to replace graphite in the anodes of Li-ion batteries.

These developments do hold promise for introduction of these new batteries into our personal electronic devices relatively soon. I have been so intrigued by this line of research I have been highlighting it for nearly four years

One of the key points of the recent Spectrum article referenced above is a discussion of a timeline for these nano-enabled batteries that ranges from two years out to early next year.

Timelines for this sort of thing are a tricky business. I wrote earlier this year on how Nanosys had developed a “silicon-based, architected material that fills in the voids of the carbon anode material matrix” that “remains intact and fully functional after 100% DoD cycle testing.” It also “demonstrated a >2× capacity improvement using 10% additive in a Li+ battery anode.”

When this material was announced, Nanosys was expecting volume sales of the material this year—in 2011. I went to the Nanosys Web site to see how this timeline was progressing, and I saw this: “Nanosys is working in collaboration with the world’s leading lithium-ion battery manufacturers to deliver unprecedented energy performance in new products coming to market over the next 18 months.”

I would imagine that it could be on the far side of two years from now before we see Li-ion batteries that have silicon on their anodes in our gadgets. But we’ll see.

The Spectrum article also suggested that now that the anode side of the battery seems to be covered, work is now turning to improving the cathode. Indeed it has. I bring your attention to the work of researchers at the University of Urbana-Champaign in building 3-D nanostructured cathodes. 

Nanotech Terrorists Apparently Don't Know What Nanotechnology Is

The confusion—which now seems insurmountable—over the advanced material science that accounts for the nanotechnology being used in products today and the molecular mechanosynthesis of the famed “nanobot” variety has now resulted in violence.

Some radical group that calls itself “Individuals Tending Toward the Savage” (oh dear!) has taken credit for at least two bomb attacks on Mexican researchers and written up a manifesto to accompany the attacks that expresses “fears that that nanoparticles could reproduce uncontrollably and form a 'gray goo' that would snuff out life on Earth.”

I have done my bit with the baby-talk explanation that would prevent people from confusing nanoparticles with mythical “gray goo,” but sometimes stupidity is just too difficult to overcome.

I first heard about threats to nanotechnology research facilities when attending the opening of IBM’s new nanotech lab in Zurich back in May. I have since learned that three so-called “eco terrorists” were convicted of planning to bomb the IBM facility

It seems to me there might be much to be radical about in this day and age, but focusing your frustration and outrage at a bunch of material scientists who ride their bikes to work and spend their days focusing atomic force microscopes hardly seems like it’s well directed or helpful.

It’s even worse when you clearly have no idea of what you’re talking about. You need to know what nanotechnology is before you can be outraged by it. 

The Unfulfilled Quest for a Good Nanotech Investment Article

My initial reaction to a new article on nanotechnology investment advice is typically less than welcoming. But today there were a couple of reasons for me to take an interest, such as the recent news that early-stage VC investors make a 2.4% higher return than their later-stage counterparts.

This kind of data might encourage investors to start early on the long road of investing in a company trying to make its way to profit with a nano-enabled product. It might also help the US economy get out of its liquidity trap.  (One can always hope.) And, if so, a little good investment advice in nanotech could be useful, especially given the discouraging news we seem to get on a regular basis on nanotech-start-up companies.

So, I decided I was going to read the latest article in this vein with as much open-mindedness as I could possibly muster.

The article entitled “Should Investors Roll the Dice with Nanotechnology?” is authored by Deborah Sweeney, the CEO of MyCorporation.com. I am sorry to say I had never heard of Ms. Sweeney before, but it seems she comes at this issue from a background in legal services.

Fair enough. It’s not exactly a background one would associate with having extensive knowledge on how to invest in an emerging technology, but you never know who might have something interesting to say.

Unfortunately, I can’t report that there is anything interesting here as it’s burdened with well-worn platitudes like, “Great rewards typically only come with great risks…” or “Before looking at a project, and potentially sinking money into it, investors must ask if this can be sold to someone.”

Really? You think? While giving a test run of every investment cliché, not one mention is made of investment horizons and how this factors into investors’ formula for risk, or how much better a nanotech-enabled product needs to be over its competitors to take a portion of the market, and how the funding gap between government research projects to commercial products is supposed to be bridged when the private investment community is keen to wait on the sideline until profits are made. 

And who are the investors this article is supposed to be addressing—VCs, stock traders, private equity? It's hard to imagine any of them sitting down to read this to inform their investments.

The question of funding and investment to further the commercialization of nanotechnology is fundamental and critical. It really deserves to be addressed better than this. 

I held my nose and took a bite, and now that I’ve swallowed it, I feel a little ill and have a bad taste left in my mouth. It might be a while before I try this again.

Paradigm Shift in Understanding of Biology Could Alter Electronics

The discovery that microbial nanowires inside the bacterium Geobacter sufurreducens can conduct electricity not only represents a paradigm shift in our fundamental understanding of biology but also could completely change how we manufacture and use electronics.

Researchers at the University of Massachusetts, led by microbiologist Derek Lovley with physicists Mark Tuominen and Nikhil Malvankar, have discovered that the Geobacter bacterium uses the nanowire-like protein filaments to transfer electrons into iron oxide (rust) contained within the soil where they live, and that this mechanism serves the same function as oxygen does for humans.

While the research, which was published in the August 7th advanced online edition of Nature Nanotechnologyrepresents the first time that metallic-like conduction of electrical charge has been observed in a protein filament, the researchers had conjectured as far back as 2005 that this was the case.

Because they didn’t have the mechanism to demonstrate this capability, their hypothesis was met with a fair amount of skepticism. It was believed that if such conduction occurred, it had to involve a mechanism that used a series of proteins known as cytochromes.

The researchers were able to continue their research in a fairly simple way by allowing the Geobacter to grow on electrodes, where the bacteria produce a electrically conductive biofilms. The researchers were able to use a series of genetically modified strains of the bacterium to narrow down the source of the metallic-like electrical conductivity inside the biofilm to a network of nanowires within the bacterium.

"This discovery not only puts forward an important new principle in biology but in materials science,” says Mark Tuominen in the U Mass press release. “We can now investigate a range of new conducting nanomaterials that are living, naturally occurring, nontoxic, easier to produce and less costly than man-made. They may even allow us to use electronics in water and moist environments. It opens exciting opportunities for biological and energy applications that were not possible before."

While Lovley (the microbiologist) has been working with the Geobacter bacterium now for nearly two decades in everything from bioremediation to the synthesis of biofuels (see video below), it was the addition of the physicists to the research that could make this a significant breakthrough in electronic materials research.

 

“As someone who studies materials, I see the nanowires in this biofilm as a new material, one that just happens to be made by nature, says Tuominen. “It’s exciting that it might bridge the gap between solid-state electronics and biological systems. It is biocompatible in a way we haven’t seen before."

While mobile phones that you can use while scuba diving may be a long way off, this would seem to be an inexpensive way to replace nanowires made from toxic and expensive materials in everything from biosensors to solid-state electronics that are used in connection with biological systems.

Flexible Displays Could Push Graphene into the Commercial Limelight

While graphene research has been growing seemingly exponentially since graphene's discovery seven years ago, it has had to cross some rather wide technological chasms to find its way into the electronic products of today.

It may be in the area of touch-screen displays for mobile devices, where the rising cost of indium tin oxide (ITO) is resulting in more expensive products, that graphene could find an early commercial adoption point.

Earlier this year, I covered research coming out of Eindhoven University in the Netherlands, which was using a combination of carbon nanotubes in a mix with plastic nanoparticles to create a material that could be sprayed onto a substrate for creating conductive flexible displays.

Now researchers out of James Tour’s lab at Rice University are using graphene to create a thin film for touch-screen displays

The research, which was originally published in the journal ACS Nano, used a single-layer sheet of graphene with a grid of metallic nanowires on a flexible substrate to create a highly conductive, see-through display that is unbreakable. Anyone who has suffered the heartbreak of watching the display on his or her Smartphone shatter after hitting the ground knows how important this breakthrough could be.

The key to success in the display was the combining of the graphene with the grid of nanowires.

"Other labs have looked at using pure graphene. It might work theoretically, but when you put it on a substrate, it doesn't have high enough conductivity at a high enough transparency. It has to be assisted in some way," says Tour in the article.

Tour’s post-doctoral researcher, Yu Zhu, further explains that the metal grid strengthens the graphene and in turn the graphene fills in the voids of the grid.

Perhaps most intriguing about the research is that it seems to lend itself to inexpensive manufacturing techniques. Tour indicates that roll-to-roll and ink-jet printing are both possible with this material.

"This material is ready to scale right now," he says.

DNA Origami Leaves a Trace on Silicon

Research has been increasing over the last couple of years in using DNA nanostructures for combining top-down and bottom-up approaches to help the semiconductor industry keep feature sizes of chips on their ever-downward trek.

The first I reported on this trend was when IBM two years ago this month announced the use of DNA origami structures as a sort of scaffold for attracting carbon nanotubes to them and thereby creating miniature circuit boards.

Earlier this year, researchers Hongbin Yu and Hao Yan at Arizona State University got all the trade press covering their research, which developed a way to ensure that DNA origami was placed where you wanted it to be on the silicon by using “nano islands” made from gold. The latest technique using DNA origami uses the molecules for the masking and etching of silicon. 

The research, which was originally published in the July 13, 2011 online issue of Journal of the American Chemical Society, exploits the ability of DNA to both promote and inhibit etching of SiO2 at the single-molecule level.

"Our approach to pattern transfer for bottom-up nanofabrication is based on the discovery that DNA promotes/inhibits the etching of SiO2 at the single-molecule level, resulting in negative/positive tone pattern transfers from DNA to the SiO2 substrate," Haitao Liu, an assistant professor in the Department of Chemistry at the University of Pittsburgh, explains in the Nanowerk article cited above.

"DNA nanostructures can be made with precise control over their sizes and shapes. Their use as lithography mask, however, has been limited due to their poor chemical stability. Our work provides a way to transfer the shape of the DNA nanostructure to silicon wafer, with sub-20 nm resolution."

In the research conducted thus far, the researchers were able to create 20-nm trenches, which could be used as nanofluidic channels, but the process is currently not optimized. However, the researchers believe that if a thinner layer of SiO2 film is used that a “patterned SiO2 layer could be used as a mask for etching of the underlying silicon substrate.”

"The formation of the trench indicates that the DNA origami locally increases the rate of oxide etching under these conditions" explains Liu in the Nanowerk Spotlight piece. "The full width at half-maximum of the trench (16.7 ± 2.8 nm) is comparable with the edge width of the DNA origami, indicating an overall faithful pattern transfer process. This result is consistent with our hypothesis that DNA can increase the etching rate of SiO2 by increasing the concentration of water. The small width of the trench shows that this effect is indeed spatially localized around the DNA." While the researchers move on to sub-10nm structures, it would seem that perfecting this process is some ways off.

As the Nanowerk story concludes, we get: “The major challenges in this undertaking are the issue of how to further increase the contrast of the transferred pattern and, crucially, to increase fidelity, consistency and accuracy of the process.” One might term all these increases as developing “manufacturability.” It seems like it’s kind of a long way off. We may be pinning a lot of hope on a process like this if we’re looking for it to step up and take up the challenge of getting feature sizes below that of photolithography and e-beam lithography.

Molecular Mechanosynthesis Not Far Away in the Dreams of a Journalist and Star Trek Fan

Molecular manufacturing is a seductive concept, especially for journalists when they first encounter the idea.

A recent example comes from a publication called International Business Times, and it reveals what is really the most attractive bit for these scribes: “Star Trek.”

The journalist, who files his report as a video, characterizes those who question the timeline and possibility for Star Trek-like replicators (I guess what he means is those who are skeptical of molecular mechanosynthesis) are “critics and naysayers.”

These critics are quickly swept aside in this brief report because, it explains, “Agents” at the Center for Responsible Technology “have stated that they believe molecular manufacturing will almost certainly be a reality by 2020.” I feel reassured, don’t you?

Of course, a tedious and unrewarding debate could ensue about what it means for molecular manufacturing to be a reality, but even one of the more optimistic of futurists, Ray Kurzweil, doesn’t believe nanobots will be swimming around in our brains until 2030.

I tend to follow more closely the timeline of Philip Moriarty, who said in a recent interview that in 2040 he hoped we will be “at the point where we could simply instruct a computer to build nanostructures, and let the computer handle all the details—no human operator involvement required.”

The critical word in the above is nanostructures, which is far cry from a cup of tea, Earl Grey, hot.

Viagra Patch Made Possible by Nanotechnology

Sildenafil citrate, known commonly by its brand name, Viagra, has extended the sex life of males since its introduction in 1998. The little blue pill comes with some unwanted side effects, however—and with a waiting period before it takes its full effect.

Seeing an opportunity to improve upon the popular prescription pill, researchers in Egypt have developed a nano-enabled transdermal patch that delivers the drug into the bloodstream far more quickly and reduces side effects that result from taking the drug orally in pill form. 

The researchers, led by Yosra S.R. Elnaggar of Alexandria University, have published their work in the International Journal of Nanotechnology. 

Others have attempted to develop a transdermal patch for delivering the sildenafil citrate into the body, butthe trick in this iteration is that the researchers have encapsulated the drug in a nanoemulsion-based system that can cross membranes.

According to a report in the publication In-Pharma Technologist:

"The researchers examined two types of nanocarrier—one forming an emulsion with the drug using a surfactant compound to allow the lipid molecules and drug to mix, and the other a self-emulsifying nanocarrier that has its own inbuilt sufactant."

The self-emulsifying approach proved successful. 

“In this paper, relevance of nanomedicine to improve SC characteristics and transdermal permeation was assessed,” the authors report in their paper. “Nanoemulsion elaborated could significantly enhance transdermal permeation of SC with higher initial permeation and prolonged release.”

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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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