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Carbon Nanotubes Form Smallest Pixels for 3D Holographic Imaging

The holograms we have seen for the past 50 years have at once fascinated and disappointed us. If we had been hoping to see something along the lines of the projected image of Princess Leia from Star Wars, or the holodeck from Star Trek Next Generation, disappointment would likely have overwhelmed our sense of fascination.

Two years ago researchers at the University of Arizona for the first time “demonstrated an optical material that can display "holographic video," as opposed to static holograms found in credit cards and product packages.” Since then it seemed our hopes for holograms have been getting brighter.

Now researchers at the University of Cambridge’s Centre of Molecular Materials for Photonics and Electronics (CMMPE) have used carbon nanotubes to create 3D hologram images with an extremely wide field of view and the highest possible resolution.

The research, which was published in the journal Advanced Materials (“Carbon Nanotube Based High Resolution Holograms”), essentially used the carbon nanotubes as diffractive elements that turn the carbon nanotubes into optical projectors. The small size of the carbon nanotubes created smaller pixels thus boosting the resolution of the image.

“Smaller pixels allow the diffraction of light at larger angles – increasing the field of view. Essentially, the smaller the pixel, the higher the resolution of the hologram,” says Dr. Haider Butt from CMMPE in a press release.

The demonstration of their new carbon nanotube-based pixels involved spelling out the name “Cambridge” using various colors of laser light that had been scattered through the carbon nanotube pixels. While initially a fairly modest display and dependent on the prohibitively expensive carbon nanotubes, Butt believes that some kind of nanomaterials will form the basis of a new approach to holographic images.

Butt adds in the release: “A new class of highly sensitive holographic sensors can be developed that could sense distance, motion, tilt, temperature and density of biological materials. What’s certain is that these results pave the way towards utilizing nanostructures to producing 3D holograms with wide field of view and the very highest resolution.”

To replace the carbon nanotubes, the researchers are looking at the prospect of using zinc oxide nanowires, which Zhong Lin Wang at Georgia Tech has been using over the years for its of piezoelectric qualities.

The other big issue that the researchers still we need to address is investigating “holographic video” because currently the carbon nanotube pixels can only project static holograms. Looks like there’s still some work to be done before Princess Leia holograms are projected, at least with a nanomaterial as the pixel.

Wearable Health Monitoring Project Turns to Nanotechnology for Power Sources

Sometimes significant innovations result just from aggregating a number of different innovations into one product. So it is with a multi-institution research effort to exploit recent developments in wireless health monitoring systems and couple them with thermoelectric and piezoelectric nanomaterials to power them.

The research is being led by the Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) headquartered at North Carolina State University in collaboration with partner institutions Florida International University, Pennsylvania State University and the University of Virginia.

“Currently there are many devices out there that monitor health in different ways,” says Dr. Veena Misra, the center’s director and professor of electrical and computer engineering at NC State in the university press release covering the research. “What’s unique about our technologies is the fact that they are powered by the human body, so they don’t require battery charging.”

While Misra may be correct in her assertion that this combination is unique within health monitoring systems, both thermoelectric and piezoelectric nanomaterials for powering devices is an area being vigorously pursued.

In the area of thermoelectric nanomaterials, we have seen significant developments this year. One coming from Wake Forest University involved using multi-walled carbon nanotubes to fabricate a thin film that the researchers claim can convert differences in temperature into electrical energy. In that case, the researchers were targeting the powering of cell phones.

A month after the Wake Forest research was announced, an international team of researchers from the California Institute of Technology, the Chinese Academy of Science's Shanghai Institute of Ceramics, Brookhaven National Laboratory and the University of Michigan developed a liquid-like material in which selenium atoms make a crystal lattice and copper atoms flow through the crystal structure like a liquid. This unusual behavior of the copper ions around the selenium lattice resulted in very low thermal conductivity (bad at conducting heat) in what is otherwise a fairly simple semiconductor (good at conducting electricity), making it an excellent candidate as a thermoelectric material.

Piezoelectric nanomaterials have been dominated until late by the use of nanowires, and specifically the research of Professor Zhong Lin Wang, Director of the Center for Nanostructure Characterization at Georgia Tech, who has almost singlehandedly kept the somewhat obscure topic of piezoelectric qualities of zinc oxide nanowires in the news. But recently graphene has entered into the area of piezoelectric materials with research coming out of Stanford University. While the Stanford research was only conducted in modeling and simulation software, it did promise to open up the fairly new conceptual field of “straintronics”.

It is not clear from either the NC State press materials or even the video that they have produced (see below), what nanomaterials they intend to use to bring on either the thermoelectric or piezoelectric effects. It will be interesting to see which direction they go with their materials.

Directed Self-Assembly Accomplished with Magnets

As chips shrink ever smaller, traditional lithography techniques have begun to lose their ability to remain accurate and the hopes of maintaining Moore's Law have dimmed as a result. But directed self-assembly, a way to build integrated circuits from the bottom up, has been held out as a possible way to keep shrinking chip feature sizes and and sustain Moore’s Law.

Basically, directed self-assembly is a way of exploiting the ability of molecules to arrange themselves into ordered structures—with a little direction from our end. Previously, H.-S. Philip Wong used lithography to carve indentations that served as a template for the molecules to self-assemble themselves. This combination of traditional lithography with self-assembly techniques has been a line of research that has seemed to be the most promising in the field. 

A less traditional line of research for directed self-assembly has been the work of Angela Belcher, in which DNA serves as the template and viruses actually build up the integrated circuit

A new addition to the field comes from the University of Delaware. Eric M. Furst and his colleagues have demonstrated how paramagnetic colloids can be directed to self-assemble in the presence of a magnetic field. 

The research, which was published in the Proceedings of the National Academies of Science (PNAS) online edition (“Multi-scale kinetics of a field-directed colloidal phase transition”),  was able to observe how the particles transitioned from a solid-like material into an organized crystalline structure. Furst claims that this represents the first time that anyone has observed this guided “phase separation” of particles.

“This development is exciting because it provides insight into how researchers can build organized structures, crystals of particles, using directing fields and it may prompt new discoveries into how we can get materials to organize themselves,” Furst says in the university press release covering the research.

An interesting twist to the research was the enlistment of NASA to see how the particles would react in a weightless environment. To realize this some of the experiments were conducted in the International Space Station. The weightless environment allowed for some fresh observations on the self-assembly process. The particles first developed into its solid-like form and then coarsened to the point of breaking apart. After separating—not unlike the way water and oil separate when combined—the particles formed themselves into the crystalline lattice structure.

Furst further notes in the article: “This is the first time we've presented the relationship between an initially disordered structure and a highly organized one and at least one of the paths between the two. We’re excited because we believe the concept of directed self-assembly will enable a scalable form of nanotechnology.”

Nanotechnology Takes Aim at Improving Beer

The motivations for certain applications of nanotechnology can run the gamut from ending our dependence on fossil fuels to providing clean drinking water in poor, remote regions of the world.  But these high-minded aspirations are not always the goal for nanotechnology applications; sometimes we just want to have a better beer drinking experience.

Australian researchers created a better way to keep beer cool two-and-a-half years ago. But  it seems that scientists in Ireland were not entirely satisfied and are developing a new material for extending the shelf life of beer

Until quite recently, it was unheard of to use plastic for beer containers because oxygen and carbon monoxide would escape through the relatively porous plastic and take away the taste of the beer.  But for some years now Nanocor Inc., which is wholly owned subsidiary of AMCOL International Corporation, has been selling its nanoclay materials to create gas-proof plastic composites for beer packaging.

Researchers at CRANN--the Science Foundation Ireland-funded nanoscience institute based at Trinity College Dublin--have decided on a different approach. Instead of using a nanoclay, the researchers will exfoliate nanosheets of boron nitride and mix them into a polymer.

The CRANN team have partnered with the brewing company SABMiller, which has agreed to invest in the research over the next two years, so we're pretty sure to have a commercial product at the end.

So, if we combine the Australian and Irish research we should be able to enjoy a plastic bottle of beer that remains cold over a much longer period of time. The joys of science.

Individual Molecular Bonds Imaged for First Time

IBM has been pushing the boundaries of Atomic Force Microscopy (AFM) all this year. In February we learned that IBM Zurich had imaged the charge distribution within a molecule for the first time.  Then the same team in May not only imaged individual hydrogen atoms but also manipulated them with the use of AFM. 

After having established new boundaries for AFM, IBM scientist Leo Gross and his colleagues next set out to apply these tools. What they've developed is a method, using AFM, for distinguishing individual molecular bonds.The researchers believe that being able to image these individual bonds could prove critical in studying graphene devices, with potential applications in high-bandwidth wireless communication and electronic displays.

“We found two different contrast mechanisms to distinguish bonds. The first one is based on small differences in the force measured above the bonds. We expected this kind of contrast but it was a challenge to resolve,” says Gross in the IBM press release covering the research. “The second contrast mechanism really came as a surprise: Bonds appeared with different lengths in AFM measurements. With the help of ab initio calculations we found that the tilting of the carbon monoxide molecule at the tip apex is the cause of this contrast.”

The researchers, who published their findings in the 14 September edition of Sciencewere able to image the bond order and length of individual carbon-carbon bonds in C60 (or buckyballs). 

While the concept of bond order had predicted that the individual bonds between carbon atoms in molecules like the buckyball differed in their length and strength, this research is the first to actually visualize these differences.

The IBM researchers expect their work to lead to greater understanding of individual molecules, which in turn could improve research into novel electronic devices, organic solar cells, and organic light-emitting diodes (OLEDs).

Ever since IBM Zurich opened up its new $90-million nanotechnology research facility last year (aptly named the “Binnig and Rohrer Nanotechnology Center”, after the joint discoverers of the AFM), it seems the researchers there have been on a tear to push AFM into the forefront of nanotechnology research. 

Nanoparticle Sensor Detects Mercury at Levels a Million Times Below Current Technology

An international team of researchers has developed a nanoparticle that is the most sensitive sensor yet for detecting the known toxin mercury in our water—an interesting and ironic use of nanotechnology, given that a number of other researchers are hard at work determining whether other nanoparticles might be hazardous to our health or the environment.

Researchers at Northwestern University in collaboration with colleagues at Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have developed a sensor system based around a nanoparticle that can detect minute levels of mercury and other heavy metals in water and fish. 

The research ("Ultrasensitive detection of toxic cations through changes in the tunnelling current across films of striped nanoparticles"), which was published in the journal Nature Materials, has produced a sensor capable of detecting heavy metals in much smaller concentrations than today's state-of-the-art methods.

“The system currently being used to test for mercury and its very toxic derivative, methyl mercury, is a time-intensive process that costs millions of dollars and can only detect quantities at already toxic levels,” says Bartosz Grzybowski, lead author of the study, in the university press release covering the research. “Ours can detect very small amounts, over [a] million times smaller than the state-of-the-art current methods. This is important because if you drink polluted water with low levels of mercury every day, it could add up and possibly lead to diseases later on. With this system consumers would one day have the ability to test their home tap water for toxic metals.”

The device the researchers have developed is basically a commercial strip of glass covered with a nanoparticle that gives the glass a kind of coat of hair—“a kind of nano-velcro”—that can then be dipped into water for testing purposes. If a metal cation—a positively charged ion—from something like methyl mercury comes in contact with the hairs, the hairs close up around the pollutant, trapping it.

The film then becomes electrically conductive and alerts the tester to the presence of the cation. A measurement of the voltage along the nanostructure film indicates the level of contamination. The researchers also found if they shortened the length of the nano-hairs they could detect cadmium.

What sounds particularly attractive about the method is that the nanofilm can be produced at a cost of somewhere between $1 to $10 to make, according to Grzybowski.

The researchers carried out studies on water in Lake Michigan near Chicago and on a mosquito fish from the Florida Everglades. The tests of the Lake Michigan water came within the range of the measurements found by the FDA and the fish testing was nearly identical to that of the US Geological Survey.

When you see a technology that is capable of improving on the current state-of –the-art by one million times and does so in a field designed for our health and safety, you have to wonder why it seems others are so keen to find replacements for it before it’s even been determined a risk.

All-Optical Nanowire Switch Promises “Consumer Photonics” in the Future

 

While nanophotonic devices have been used for optical processing for some time, the aim of late has been to use light to actually throw switches to control electronic circuits. Hong X. Tang of Yale University wrote on the pages of Spectrum three years ago about his success in using the pressure of light to operate nanomechanical devices

Now researchers at the University of Pennsylvania have developed what they claim is the first all-optical nanowire switch. The research, which was published in the journal Nature Nanotechnology (“All-optical active switching in individual semiconductor nanowires”), not only succeeded in fashioning a switch from cadmium sulfide nanowires, but also managed to combine the photonic switches into a logic gate.

The idea that cadmium sulfide nanowires could be used to make optical switches derived from the researchers previous research that demonstrated that these nanowires possessed extraordinary strong light-matter coupling

With that previous work as inspiration, the researchers set off on their current research and started by cutting a gap into a nanowire. They then ran energy through one of the nanowire pieces until it started to emit laser light from one end of it and started to bridge the gap to the other piece of nanowire.

“Once we have the light in the second segment, we shine another light through the structure and turn off what is being transported through that wire,” says associate professor Ritesh Agarwal in the university press release covering the research. “That's what makes it a switch.”

Agarwal and his colleague in the research, graduate student Brian Piccione, opted to combine their new switches together to assemble a logic gate. “We used these optical switches to construct a NAND gate, which is a fundamental building block of modern computer processing,” says Piccione in the press release.

While Agarwal makes a fair assessment that this work at least indicates that the future could become “consumer photonics” as opposed to “consumer electronics”, I think it also fair to say that we may still be a long way off from that eventual future. Definitely a step in the right direction though.

Public Awareness of Nanotechnology Continues to Dwindle

The numbers are in again and it seems that Americans are still largely ignorant of nanotechnology’s existence

Five years ago the Project on Emerging Technology commissioned a poll to determine the awareness of nanotechnology among the U.S. population. At the time, there was surprise that only 6 percent of Americans had “heard a lot” about nanotechnology, down from 10 percent in 2006.

It seems that in the years since, the number has slipped even further. Only 5 percent of the population now claims to have “heard a lot” about nanotechnology. It seems that a seemingly endless parade of public outreach projects hasn’t raised the nation’s nano-consciousness.

With Harris Interactive releasing this poll, we were spared the Project on Emerging Technology’s blatantly obvious insights like: “Individuals with less education and lower incomes are least likely to have heard about nanotechnology.” But Harris does dwell on the discovery that people over the age of 65 believe that nanotechnology’s benefits outweighed its risks (58%, versus 32%-36% among other age groups).

So fascinated were the folks at Harris Interactive that they brought in Dr. Kathleen Eggleson, leader of the Nano Impacts Intellectual Community at the University of Notre Dame to comment. "Though it may initially seem counterintuitive, it actually makes sense that those aware of nanotechnology within the 65+ age group tend to believe that the benefits of nanotechnology will outweigh the risks, as the prevalence of worry in general tends to decline with age," says Eggleson in the press release. "Older Americans also have firsthand experience with the emergence of many different technologies that have brought new benefits to their lives."

While Eggleson sees this primarily as a psychological phenomenon related to one’s age, I see it more as a social phenomenon brought upon by the age we live in. The current generation has been raised on an overarching “distrust of big business and the supposedly complicit governments that support the immoral aims of business.”

The generation that stayed up late watching Apollo missions, and bought the first personal computers, grew up believing that technology and those who developed it were on a mission to raise the human condition. Younger generations give greater credence to theories that the Apollo moon landings were staged and that the computers we’ve brought into our homes were designed to spy on us.

To those inclined to see corporate and governmental conspiracies lurking behind every new high-tech development, nanotechnology is just the latest in a long line of threats. Nonetheless, try as some NGOs might, it seems that people just are not afraid of nanotechnology and it still enjoys a “white hat” status

I suppose we are supposed to see the numbers of this report as alarming. I do not. Perhaps the dwindling number of people who “know a lot” about nanotechnology is a sign that we have outgrown the hype that surrounded the field a decade ago. Maybe it also means that the term is disappearing from general use as it morphs from a separate field to just another prefix. I am further comforted that despite persistent and sometimes deliberately misleading attempts to demonize nanotechnology, people for the most part just don’t seem too worried. 

Simple Solutions based on Nanotechnology Help Flood Victims in Thailand

This week the BBC covered some of the technologies that have been developed and are being planned to cope with the floods that have plagued Thailand in the past year. You will have to go to the link provided to see the video as the BBC has made it impossible to embed it.

Not all of the technologies described involve nanotechnology, but two of the most interesting do. Both were developed by the National Nanotechnology Center in Thailand (Nanotec).

One uses silver nanoparticles for a water filtration system that operates on solar power, called the SOS Water System. The genius of it is its portability—it's shown mounted on a small boat, purifying water from the flooded river it's floating on. Though small, the system is capable of purifying a remarkable 200 liters per hour.

Nanotec calls the second technology covered by the BBC video "n-SACK."  It’s basically a material that absorbs water. As shown, it creates a better sandbag—better in a couple of ways: Before absorption, it's much smaller and lighter than a sandbag, and unlike one, it not only blocks floodwaters, it partially absorbs them.

Now, these nanotechnologies are not groundbreaking. Inexpensive water filtration systems that employ nanoparticles are nothing new, nor are water-philic materials. But it is the development of these technologies for an acute need that is interesting.

Specifically, the breakthrough here is that the Nanotec researchers were able to make a high-capacity water purifier portable and solar-based, on the one hand, and bringing the price down to $2 per "sandbag" in the other. Now that’s still twice as high as a typical sandbag, but these can be reused. And, if I might add, it’s much less labor intensive. With sand bags someone has to shovel that sand into the bags. With the n-SACK, you simply place the bag into the way of the flood and it fills itself up.

While much of nanotechnology research is devoted to far-off aspirations like ridding the world of artificial light—with  the claimed aim of preventing starvation and thirst—sometimes just addressing the problems in front of you can significantly improve the world.

Also noteworthy is the pragmatism shown by the Thailand researchers when they opted to use silver nanoparticles in their portable water filtration system. Meanwhile Europe and the US seems to be in the midst of a “paralysis by analysis” in regulating the use of silver nanoparticles.

It's easy to imagine the victims of this year's Thailand floods weren’t too troubled by a lack of regulations governing the nanoparticles that allowed them to drink the only clean water they may have had access to for days. As I have said in the past: "The billions who eat, sleep, and live in what are virtually open sewers and who might like to have a cheap way of getting clean drinking water or bringing electricity into their homes seem to be lost in FoE (Friends of the Earth) self-righteousness.”

Stable RNA Structures Show Promise in Drug Delivery for Cancer Treatment

Last year I covered research led by Peixuan Guo—at the time he was at the University of Cincinnati—in making stable 3D nanostructures out of RNA (ribonucleic acid) that were resistant to the enzymes that chop RNA up within minutes. 

At the time, this was a significant achievement because RNA possesses more flexible capabilities in building structures than does DNA—or would, if they weren't eaten up in short order. With a stable RNA Guo planned on using it in “gearing a powerful nanomotor that packages viral DNA into the protein shells of a bacterial virus named phi29.”

Now Guo is back with his stable RNA—this time at the University of Kentucky—and has developed a nanoparticle made from the material that could help treat cancer and viral infections

The research, which was published in Nano Today, involved building an X-shaped RNA structure in which each arm of the structure could contain different diagnostic and therapeutic packages.

The packages used in this structure were “small interfering RNA for silencing genes, micro-RNA for regulating gene expression, aptamer for targeting cancer cells, or a ribozyme that can catalyze chemical reactions.”

"RNA nanotechnology is an emerging field, but the instability and degradation of RNA nanoparticles have made many scientists flinch away from the research in RNA nanotechnology,” Guo said in the university press release covering the research.  “We have addressed these issues, and now it is possible to produce RNA nanoparticles that are highly stable both chemically and thermodynamically in the test tube or in the body with great potential as therapeutic reagents.”

Of course, there are a number of nanostructures that have proven capable of both diagnostic and therapeutic in the treatment of cancer and other diseases. It’s not clear from the research whether the RNA-based nanoparticles are any more effective than some other nanostructure in these roles.

The research seems instead to focus on what is capable with an RNA nanoparticle that can stay intact long enough to build something from them. Perhaps their “bottom-up” manufacturing capabilities are still being considered for molecular machine systems as the Foresight Institute wished for last year

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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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