Category Archives: nanotechnology

Large(!)-scale graphene composite fabrication at the US Oak Ridge National Laboratory (ORNL)

When you’re talking about large-scale production of nanomaterials, it would be more accurate term to say ‘relatively large when compared to the nanoscale’. A May 15, 2015 news item on ScienceDaily, trumpets the news,

One of the barriers to using graphene at a commercial scale could be overcome using a method demonstrated by researchers at the Department of Energy’s Oak Ridge National Laboratory [ORNL].

Graphene, a material stronger and stiffer than carbon fiber, has enormous commercial potential but has been impractical to employ on a large scale, with researchers limited to using small flakes of the material.

Now, using chemical vapor deposition, a team led by ORNL’s Ivan Vlassiouk has fabricated polymer composites containing 2-inch-by-2-inch sheets of the one-atom thick hexagonally arranged carbon atoms. [emphasis mine]

Once you understand where these scientists are coming from in terms of the material size, it becomes easier to appreciate the accomplishment and its potential. From a May 14, 2015 ORNL news release (also on EurekAlert), which originated the news item,

The findings, reported in the journal Applied Materials & Interfaces, could help usher in a new era in flexible electronics and change the way this reinforcing material is viewed and ultimately used.

“Before our work, superb mechanical properties of graphene were shown at a micro scale [one millionth of a metre],” said Vlassiouk, a member of ORNL’s Energy and Transportation Science Division. “We have extended this to a larger scale, which considerably extends the potential applications and market for graphene.”

While most approaches for polymer nanocomposition construction employ tiny flakes of graphene or other carbon nanomaterials that are difficult to disperse in the polymer, Vlassiouk’s team used larger sheets of graphene. This eliminates the flake dispersion and agglomeration problems and allows the material to better conduct electricity with less actual graphene in the polymer.

“In our case, we were able to use chemical vapor deposition to make a nanocomposite laminate that is electrically conductive with graphene loading that is 50 times less compared to current state-of-the-art samples,” Vlassiouk said. This is a key to making the material competitive on the market.

If Vlassiouk and his team can reduce the cost and demonstrate scalability, researchers envision graphene being used in aerospace (structural monitoring, flame-retardants, anti-icing, conductive), the automotive sector (catalysts, wear-resistant coatings), structural applications (self-cleaning coatings, temperature control materials), electronics (displays, printed electronics, thermal management), energy (photovoltaics, filtration, energy storage) and manufacturing (catalysts, barrier coatings, filtration).

Here’s a link to and a citation for the paper,

Strong and Electrically Conductive Graphene-Based Composite Fibers and Laminates by Ivan Vlassiouk, Georgios Polizos, Ryan Cooper, Ilia Ivanov, Jong Kahk Keum, Felix Paulauskas, Panos Datskos, and Sergei Smirnov. ACS Appl. Mater. Interfaces, Article ASAP DOI: 10.1021/acsami.5b01367 Publication Date (Web): April 28, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Cosmetics giant, L’Oréal, to 3D print skin

L’Oréal, according to a May 19, 2015 BBC (British Broadcasting Corporation) online news item, has partnered with Organovo, a 3D bioprinting startup, to begin producing skin,

French cosmetics firm L’Oreal is teaming up with bio-engineering start-up Organovo to 3D-print human skin.

It said the printed skin would be used in product tests.

Organovo has already made headlines with claims that it can 3D-print a human liver but this is its first tie-up with the cosmetics industry.

Experts said the science might be legitimate but questioned why a beauty firm would want to print skin. [emphasis mine]

L’Oreal currently grows skin samples from tissues donated by plastic surgery patients. It produces more than 100,000, 0.5 sq cm skin samples per year and grows nine varieties across all ages and ethnicities.

Its statement explaining the advantage of printing skin, offered little detail: “Our partnership will not only bring about new advanced in vitro methods for evaluating product safety and performance, but the potential for where this new field of technology and research can take us is boundless.”

The beauty and cosmetics industry has a major interest in technology, especially anything to do with the skin. I’m curious as to what kind of an expert wouldn’t realize that cosmetics companies test products on skin and might like to have a ready supply. Still, I have to admit to surprise when I first (2006) started researching nanotechnology;  L’Oréal at one point was the sixth largest nanotechnology patent holder in the US (see my Nanotech Mysteries Wiki page: Marketers put the buy in nano [scroll down to Penetration subhead]). In 2008 L’Oréal company representatives were set for a discussion on their nanotechnology efforts and the precautionary principle, which was to be hosted by the Wilson Center’s Project for Emerging Nanotechnologies (PEN). The company cancelled at a rather interesting time as I had noted in my June 19, 2008 posting. (scroll down about 40% of the way until you see mention of Dr. Andrew Maynard).

Back to 3D printing technology and cosmetics giants, a May 5, 2015 Organovo/L’Oréal press release provides more detail about the deal,

L’Oreal USA, the largest subsidiary of the world’s leading beauty company, has announced a partnership with 3-D bioprinting company Organovo Holdings, Inc. (NYSE MKT: ONVO) (“Organovo”).  Developed between L’Oreal’s U.S.-based global Technology Incubator and Organovo, the collaboration will leverage Organovo’s proprietary NovoGen Bioprinting Platform and L’Oreal’s expertise in skin engineering to develop 3-D printed skin tissue for product evaluation and other areas of advanced research.

This partnership marks the first-ever application of Organovo’s groundbreaking technology within the beauty industry.

“We developed our technology incubator to uncover disruptive innovations across industries that have the potential to transform the beauty business,” said Guive Balooch, Global Vice President of L’Oreal’s Technology Incubator.  “Organovo has broken new ground with 3-D bioprinting, an area that complements L’Oreal’s pioneering work in the research and application of reconstructed skin for the past 30 years. Our partnership will not only bring about new advanced in vitro methods for evaluating product safety and performance, but the potential for where this new field of technology and research can take us is boundless.”

Organovo’s 3D bioprinting enables the reproducible, automated creation of living human tissues that mimic the form and function of native tissues in the body.

“We are excited to be partnering with L’Oreal, whose leadership in the beauty industry is rooted in scientific innovation and a deep commitment to research and development,” said Keith Murphy, Chairman and Chief Executive Officer at Organovo. “This partnership is a great next step to expand the applications of Organovo’s 3-D bioprinting technology and to create value for both L’Oreal and Organovo by building new breakthroughs in skin modeling.”

I don’t have much information about Organovo here, certainly nothing about the supposed liver (how did I miss that?), but there is a Dec. 26, 2012 posting about its deal with software giant, Autodesk.

McGill University researchers put the squeeze Tomonaga-Luttinger theory in quantum mechanics

McGill University (Montréal, Québec, Canada) researchers testing the Tomonaga-Luttinger theory had international help according to a May 15, 2015 news item on ScienceDaily,

We all know intuitively that normal liquids flow more quickly as the channel containing them tightens. Think of a river flowing through narrow rapids.

But what if a pipe were so amazingly tiny that only a few atoms of superfluid helium could squeeze through its opening at once? According to a longstanding quantum-mechanics model, the superfluid helium would behave differently from a normal liquid: far from speeding up, it would actually slow down.

For more than 70 years, scientists have been studying the flow of helium through ever smaller pipes. But only recently has nanotechnology made it possible to reach the scale required to test the theoretical model, known as the Tomonaga-Luttinger theory (after the scientists who developed it).

Now, a team of McGill University researchers, with collaborators at the University of Vermont and at Leipzig University in Germany, has succeeded in conducting experiments with the smallest channel yet – less than 30 atoms wide. In results published online today in Science Advances, the researchers report that the flow of superfluid helium through this miniature faucet does, indeed, appear to slow down.

A May 15, 2015 University of McGill news release (also on EurekAlert), which originated the news item, expands on the theme and notes this is one step on the road to proving the theory,

“Our results suggest that a quantum faucet does show a fundamentally different behaviour,” says McGill physics professor Guillaume Gervais, who led the project. “We don’t have the smoking gun yet. But we think this a great step toward proving experimentally the Tomonaga-Luttinger theory in a real liquid.”

The zone where physics changes

Insights from the research could someday contribute to novel technologies, such as nano-sensors with applications in GPS systems. But for now, Gervais says, the results are significant simply because “we’re pushing the limit of understanding things on the nanoscale. We’re approaching the grey zone where all physics changes.”

Prof. Adrian Del Maestro from the University of Vermont has been employing high-performance computer simulations to understand just how small the faucet has to be before this new physics emerges. “The ability to study a quantum liquid at such diminutive length scales in the laboratory is extremely exciting as it allows us to extend our fundamental understanding of how atoms cooperate to form the superfluid state of matter,” he says. “The superfluid slowdown we observe signals that this cooperation is starting to break down as the width of the pipe narrows to the nanoscale” and edges closer to the exotic one-dimensional limit envisioned in the Tomonaga-Luttinger theory.

Building what is probably the world’s smallest faucet has been no simple task. Gervais hatched the idea during a five-minute conversation over coffee with a world-leading theoretical physicist. That was eight years ago. But getting the nano-plumbing to work took “at least 100 trials – maybe 200,” says Gervais, who is a fellow of the Canadian Institute for Advanced Research.

A beam of electrons as drill bit

Using a beam of electrons as a kind of drill bit, the team made holes as small as seven nanometers wide in a piece of silicon nitride, a tough material used in applications such as automotive diesel engines and high-performance ball bearings. By cooling the apparatus to very low temperatures, placing superfluid helium on one side of the pore and applying a vacuum to the other, the researchers were able to observe the flow of the superfluid through the channel. Varying the size of the channel, they found that the maximum speed of the flow slowed as the radius of the pore decreased.

The experiments take advantage of a unique characteristic of superfluids. Unlike ordinary liquids – water or maple syrup, for example – superfluids can flow without any viscosity. As a result, they can course through extremely narrow channels; and once in motion, they don’t need any pressure to keep going. Helium is the only element in nature known to become a superfluid; it does so when cooled to an extremely low temperature.

An inadvertent breakthrough

For years, however, the researchers were frustrated by a technical glitch: the tiny pore in the silicon nitride material kept getting clogged by contaminants. Then one day, while Gervais was away at a conference abroad, a new student in his lab inadvertently deviated from the team’s operating procedure and left a valve open in the apparatus. “It turned out that this open valve kept the hole open,” Gervais says. “It was the key to getting the experiment to work. Scientific breakthroughs don’t always happen by design!”

Prof. Bernd Rosenow, a quantum physicist at Leipzig University’s Institute for Theoretical Physics, also contributed to the study.

Here’s a link to and a citation for the paper,

Critical flow and dissipation in a quasi–one-dimensional superfluid by Pierre-François Duc, Michel Savard, Matei Petrescu, Bernd Rosenow, Adrian Del Maestro, Guillaume Gervais. Science Advances 15 May 2015: Vol. 1 no. 4 e1400222 DOI: 10.1126/sciadv.1400222

This is an open access paper.

I sing the body cyber: two projects funded by the US National Science Foundation

Points to anyone who recognized the reference to Walt Whitman’s poem, “I sing the body electric,” from his classic collection, Leaves of Grass (1867 edition; h/t Wikipedia entry). I wonder if the cyber physical systems (CPS) work being funded by the US National Science Foundation (NSF) in the US will occasion poetry too.

More practically, a May 15, 2015 news item on Nanowerk, describes two cyber physical systems (CPS) research projects newly funded by the NSF,

Today [May 12, 2015] the National Science Foundation (NSF) announced two, five-year, center-scale awards totaling $8.75 million to advance the state-of-the-art in medical and cyber-physical systems (CPS).

One project will develop “Cyberheart”–a platform for virtual, patient-specific human heart models and associated device therapies that can be used to improve and accelerate medical-device development and testing. The other project will combine teams of microrobots with synthetic cells to perform functions that may one day lead to tissue and organ re-generation.

CPS are engineered systems that are built from, and depend upon, the seamless integration of computation and physical components. Often called the “Internet of Things,” CPS enable capabilities that go beyond the embedded systems of today.

“NSF has been a leader in supporting research in cyber-physical systems, which has provided a foundation for putting the ‘smart’ in health, transportation, energy and infrastructure systems,” said Jim Kurose, head of Computer & Information Science & Engineering at NSF. “We look forward to the results of these two new awards, which paint a new and compelling vision for what’s possible for smart health.”

Cyber-physical systems have the potential to benefit many sectors of our society, including healthcare. While advances in sensors and wearable devices have the capacity to improve aspects of medical care, from disease prevention to emergency response, and synthetic biology and robotics hold the promise of regenerating and maintaining the body in radical new ways, little is known about how advances in CPS can integrate these technologies to improve health outcomes.

These new NSF-funded projects will investigate two very different ways that CPS can be used in the biological and medical realms.

A May 12, 2015 NSF news release (also on EurekAlert), which originated the news item, describes the two CPS projects,

Bio-CPS for engineering living cells

A team of leading computer scientists, roboticists and biologists from Boston University, the University of Pennsylvania and MIT have come together to develop a system that combines the capabilities of nano-scale robots with specially designed synthetic organisms. Together, they believe this hybrid “bio-CPS” will be capable of performing heretofore impossible functions, from microscopic assembly to cell sensing within the body.

“We bring together synthetic biology and micron-scale robotics to engineer the emergence of desired behaviors in populations of bacterial and mammalian cells,” said Calin Belta, a professor of mechanical engineering, systems engineering and bioinformatics at Boston University and principal investigator on the project. “This project will impact several application areas ranging from tissue engineering to drug development.”

The project builds on previous research by each team member in diverse disciplines and early proof-of-concept designs of bio-CPS. According to the team, the research is also driven by recent advances in the emerging field of synthetic biology, in particular the ability to rapidly incorporate new capabilities into simple cells. Researchers so far have not been able to control and coordinate the behavior of synthetic cells in isolation, but the introduction of microrobots that can be externally controlled may be transformative.

In this new project, the team will focus on bio-CPS with the ability to sense, transport and work together. As a demonstration of their idea, they will develop teams of synthetic cell/microrobot hybrids capable of constructing a complex, fabric-like surface.

Vijay Kumar (University of Pennsylvania), Ron Weiss (MIT), and Douglas Densmore (BU) are co-investigators of the project.

Medical-CPS and the ‘Cyberheart’

CPS such as wearable sensors and implantable devices are already being used to assess health, improve quality of life, provide cost-effective care and potentially speed up disease diagnosis and prevention. [emphasis mine]

Extending these efforts, researchers from seven leading universities and centers are working together to develop far more realistic cardiac and device models than currently exist. This so-called “Cyberheart” platform can be used to test and validate medical devices faster and at a far lower cost than existing methods. CyberHeart also can be used to design safe, patient-specific device therapies, thereby lowering the risk to the patient.

“Innovative ‘virtual’ design methodologies for implantable cardiac medical devices will speed device development and yield safer, more effective devices and device-based therapies, than is currently possible,” said Scott Smolka, a professor of computer science at Stony Brook University and one of the principal investigators on the award.

The group’s approach combines patient-specific computational models of heart dynamics with advanced mathematical techniques for analyzing how these models interact with medical devices. The analytical techniques can be used to detect potential flaws in device behavior early on during the device-design phase, before animal and human trials begin. They also can be used in a clinical setting to optimize device settings on a patient-by-patient basis before devices are implanted.

“We believe that our coordinated, multi-disciplinary approach, which balances theoretical, experimental and practical concerns, will yield transformational results in medical-device design and foundations of cyber-physical system verification,” Smolka said.

The team will develop virtual device models which can be coupled together with virtual heart models to realize a full virtual development platform that can be subjected to computational analysis and simulation techniques. Moreover, they are working with experimentalists who will study the behavior of virtual and actual devices on animals’ hearts.

Co-investigators on the project include Edmund Clarke (Carnegie Mellon University), Elizabeth Cherry (Rochester Institute of Technology), W. Rance Cleaveland (University of Maryland), Flavio Fenton (Georgia Tech), Rahul Mangharam (University of Pennsylvania), Arnab Ray (Fraunhofer Center for Experimental Software Engineering [Germany]) and James Glimm and Radu Grosu (Stony Brook University). Richard A. Gray of the U.S. Food and Drug Administration is another key contributor.

It is fascinating to observe how terminology is shifting from pacemakers and deep brain stimulators as implants to “CPS such as wearable sensors and implantable devices … .” A new category has been created, CPS, which conjoins medical devices with other sensing devices such as wearable fitness monitors found in the consumer market. I imagine it’s an attempt to quell fears about injecting strange things into or adding strange things to your body—microrobots and nanorobots partially derived from synthetic biology research which are “… capable of performing heretofore impossible functions, from microscopic assembly to cell sensing within the body.” They’ve also sneaked in a reference to synthetic biology, an area of research where some concerns have been expressed, from my March 19, 2013 post about a poll and synthetic biology concerns,

In our latest survey, conducted in January 2013, three-fourths of respondents say they have heard little or nothing about synthetic biology, a level consistent with that measured in 2010. While initial impressions about the science are largely undefined, these feelings do not necessarily become more positive as respondents learn more. The public has mixed reactions to specific synthetic biology applications, and almost one-third of respondents favor a ban “on synthetic biology research until we better understand its implications and risks,” while 61 percent think the science should move forward.

I imagine that for scientists, 61% in favour of more research is not particularly comforting given how easily and quickly public opinion can shift.

A ‘sweat’mometer—sensing your health through your sweat

At this point, it’s more fitness monitor than diagnostic tool, so, you’ll still need to submit blood, stool, and urine samples when the doctor requests it but the device does offer some tantalizing possibilities according to a May 15, 2015 news item on phys.org,

Made from state-of-the-art silicon transistors, an ultra-low power sensor enables real-time scanning of the contents of liquids such as perspiration. Compatible with advanced electronics, this technology boasts exceptional accuracy – enough to manufacture mobile sensors that monitor health.

Imagine that it is possible, through a tiny adhesive electronic stamp attached to the arm, to know in real time one’s level of hydration, stress or fatigue while jogging. A new sensor developed at the Nanoelectronic Devices Laboratory (Nanolab) at EPFL [École Polytechnique Fédérale de Lausanne in Switzerland] is the first step toward this application. “The ionic equilibrium in a person’s sweat could provide significant information on the state of his health,” says Adrian Ionescu, director of Nanolab. “Our technology detects the presence of elementary charged particles in ultra-small concentrations such as ions and protons, which reflects not only the pH balance of sweat but also more complex hydration of fatigues states. By an adapted functionalization I can also track different kinds of proteins.”

A May 15, 2015 EPFL press release by Laure-Anne Pessina, which originated the news item, includes a good technical explanation of the device for non-experts in the field,

Published in the journal ACS Nano, the device is based on transistors that are comparable to those used by the company Intel in advanced microprocessors. On the state-of-the-art “FinFET” transistor, researchers fixed a microfluidic channel through which the fluid to be analyzed flows. When the molecules pass, their electrical charge disturbs the sensor, which makes it possible to deduce the fluid’s composition.

The new device doesn’t host only sensors, but also transistors and circuits enabling the amplification of the signals – a significant innovation. The feat relies on a layered design that isolates the electronic part from the liquid substance. “Usually it is necessary to use separately a sensor for detection and a circuit for computing and signal amplification,” says Sara Rigante, lead author of the publication. “In our chip, sensors and circuits are in the same device – making it a ‘Sensing integrated circuit’. This proximity ensures that the signal is not disturbed or altered. We can thereby obtain extremely stable and accurate measurements.”

But that’s not all. Due to the size of the transistors – 20 nanometers, which is one hundred to one thousand times smaller than the thickness of a hair – it is possible to place a whole network of sensors on one chip, with each sensor locating a different particle. “We could also detect calcium, sodium or potassium in sweat,” the researcher elaborates.

As to what makes the device special (from the press release),

The technology developed at EPFL stands out from its competitors because it is extremely stable, compatible with existing electronics (CMOS), ultra-low power and easy to reproduce in large arrays of sensors. “In the field of biosensors, research around nanotechnology is intense, particularly regarding silicon nanowires and nanotubes. But these technologies are frequently unstable and therefore unusable for now in industrial applications,” says Ionescu. “In the case of our sensor, we started from extremely powerful, advanced technology and adapted it for sensing need in a liquid-gate FinFET configurations. The precision of the electronics is such that it is easy to clone our device in millions with identical characteristics.”

In addition, the technology is not energy intensive. “We could feed 10,000 sensors with a single solar cell,” Professor Ionescu asserts.

Of course, there does seem to be one shortcoming (from the press release),

Thus far, the tests have been carried out by circulating the liquid with a tiny pump. Researchers are currently working on a means of sucking the sweat into the microfluidic tube via wicking. This would rid the small analyzing “band-aid” of the need for an attached pump.

While they work on eliminating the pump part of the device, here’s  a link to and a citation for the paper,

Sensing with Advanced Computing Technology: Fin Field-Effect Transistors with High-k Gate Stack on Bulk Silicon by Sara Rigante, Paolo Scarbolo, Mathias Wipf, Ralph L. Stoop, Kristine Bedner, Elizabeth Buitrago, Antonios Bazigos, Didier Bouvet, Michel Calame, Christian Schönenberger, and Adrian M. Ionescu. ACS Nano, Article ASAP DOI: 10.1021/nn5064216 Publication Date (Web): March 27, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

As for the ‘sweat’mometer in the headline, I was combining sweat with thermometer.

Iridescent bird feathers inspire synthetic melanin for structural color/colour

I’m hoping one day they’ll be able to create textiles that rely on structure rather than pigment or dye for colour so my clothing will no longer fade with repeated washings and exposure to sunlight. There was one such textile, morphotex (named for the Blue Morpho butterfly, no longer produced by Japanese manufacturer Teijin but you can see a photo of the fabric which was fashioned into a dress by Australian designer Donna Sgro in my July 19, 2010 posting.

This particular project at the University of California at San Diego (UCSD), sadly, is not textile-oriented, but has resulted in a film according to a May 13, 2015 news item on ScienceDaily,

Inspired by the way iridescent bird feathers play with light, scientists have created thin films of material in a wide range of pure colors — from red to green — with hues determined by physical structure rather than pigments.

Structural color arises from the interaction of light with materials that have patterns on a minute scale, which bend and reflect light to amplify some wavelengths and dampen others. Melanosomes, tiny packets of melanin found in the feathers, skin and fur of many animals, can produce structural color when packed into solid layers, as they are in the feathers of some birds.

“We synthesized and assembled nanoparticles of a synthetic version of melanin to mimic the natural structures found in bird feathers,” said Nathan Gianneschi, a professor of chemistry and biochemistry at the University of California, San Diego. “We want to understand how nature uses materials like this, then to develop function that goes beyond what is possible in nature.”

A May 13, 2015 UCSD news release by Susan Brown (also on EurekAlert), which originated the news item, describes the inspiration and the work in more detail,

Gianneschi’s work focuses on nanoparticles that can sense and respond to the environment. He proposed the project after hearing Matthew Shawkey, a biology professor at the University of Akron, describe his work on the structural color in bird feathers at a conference. Gianneschi, Shawkey and colleagues at both universities report the fruits of the resulting collaboration in the journal ACS Nano, posted online May 12 [2015].

To mimic natural melanosomes, Yiwen Li, a postdoctoral fellow in Gianneschi’s lab, chemically linked a similar molecule, dopamine, into meshes. The linked, or polydopamine, balled up into spherical particles of near uniform size. Ming Xiao, a graduate student who works with Shawkey and polymer science professor Ali Dhinojwala at the University of Akron, dried different concentrations of the particles to form thin films of tightly packed polydopamine particles.

The films reflect pure colors of light; red, orange, yellow and green, with hue determined by the thickness of the polydopamine layer and how tightly the particles packed, which relates to their size, analysis by Shawkey’s group determined.

The colors are exceptionally uniform across the films, according to precise measurements by Dimitri Deheyn, a research scientist at UC San Diego’s Scripps Institution of Oceanography who studies how a wide variety of organisms use light and color to communicate. “This spatial mapping of spectra also tells you about color changes associated with changes in the size or depth of the particles,” Deheyn said.

The qualities of the material contribute to its potential application. Pure hue is a valuable trait in colorimetric sensors. And unlike pigment-based paints or dyes, structural color won’t fade. Polydopamine, like melanin, absorbs UV light, so coatings made from polydopamine could protect materials as well. Dopamine is also a biological molecule used to transmit information in our brains, for example, and therefore biodegradable.

“What has kept me fascinated for 15 years is the idea that one can generate colors across the rainbow through slight (nanometer scale) changes in structure,” said Shawkey whose interests range from the physical mechanisms that produce colors to how the structures grow in living organisms. “This idea of biomimicry can help solve practical problems but also enables us to test the mechanistic and developmental hypotheses we’ve proposed,” he said.

Natural melanosomes found in bird feathers vary in size and particularly shape, forming rods and spheres that can be solid or hollow. The next step is to vary the shapes of nanoparticles of polydopamine to mimic that variety to experimentally test how size and shape influence the particle’s interactions with light, and therefore the color of the material. Ultimately, the team hopes to generate a palette of biocompatible, structural color.

Here’s a link to and a citation for the paper,

Bio-Inspired Structural Colors Produced via Self-Assembly of Synthetic Melanin Nanoparticles by Ming Xiao, Yiwen Li, Michael C. Allen, Dimitri D. Deheyn, Xiujun Yue, Jiuzhou Zhao, Nathan C. Gianneschi, Matthew D. Shawkey, and Ali Dhinojwala. ACS Nano, Article ASAP DOI: 10.1021/acsnano.5b01298 Publication Date (Web): May 4, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

For anyone who’d like to explore structural colour further, there’s this Feb. 7, 2013 posting which features excerpts from and a link to an excellent article by Cristina Luiggi for The Scientist.

Policing, detecting, and arresting pollution

The title for a May 13, 2015 news item on ScienceDaily was certainly eye-catching,

Nano-policing pollution

Pollutants emitted by factories and car exhausts affect humans who breathe in these harmful gases and also aggravate climate change up in the atmosphere. Being able to detect such emissions is a critically needed measure.

New research by the Nanoparticles by Design Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), in collaboration with the Materials Center Leoben Austria and the Austrian Centre for Electron Microscopy and Nanoanalysis has developed an efficient way to improve methods for detecting polluting emissions using a sensor at the nanoscale. …

A May 13, 2015 OIST press release (also on EurekAlert) by Joykrit Mitra, which originated the news item, details the research (Note: A link has been removed),

The researchers used a copper oxide nanowire decorated with palladium nanoparticles to detect carbon monoxide, a common industrial pollutant.  The sensor was tested in conditions similar to ambient air since future devices developed from this method will need to operate in these conditions.

Copper oxide is a semiconductor and scientists use nanowires fabricated from it to search for potential application in the microelectronics industry. But in gas sensing applications, copper oxide was much less widely investigated compared to other metal oxide materials.

A semiconductor can be made to experience dramatic changes in its electrical properties when a small amount of foreign atoms are made to attach to its surface at high temperatures.  In this case, the copper oxide nanowire was made part of an electric circuit. The researchers detected carbon monoxide indirectly, by measuring the change in the resulting circuit’s electrical resistance in presence of the gas. They found that copper oxide nanowires decorated with palladium nanoparticles show a significantly greater increase in electrical resistance in the presence of carbon monoxide than the same type of nanowires without the nanoparticles.

The OIST Nanoparticles by Design Unit used a sophisticated technique that allowed them to first sift nanoparticles according to size, then deliver and deposit the palladium nanoparticles onto the surface of the nanowires in an evenly distributed manner. This even dispersion of size selected nanoparticles and the resulting nanoparticles-nanowire interactions are crucial to get an enhanced electrical response.  The OIST nanoparticle deposition system can be tailored to deposit multiple types of nanoparticles at the same time, segregated on distinct areas of the wafer where the nanowire sits. In other words, this system can be engineered to be able to detect multiple kinds of gases.  The next step is to detect different gases at the same time by using multiple sensor devices, with each device utilizing a different type of nanoparticle.

Compared to other options being explored in gas sensing which are bulky and difficult to miniaturize, nanowire gas sensors will be cheaper and potentially easier to mass produce.

The main energy cost in operating this kind of a sensor will be the high temperatures necessary to facilitate the chemical reactions for ensuring certain electrical response. In this study 350 degree centigrade was used.  However, different nanowire-nanoparticle material configurations are currently being investigated in order to lower the operating temperature of this system.

“I think nanoparticle-decorated nanowires have a huge potential for practical applications as it is possible to incorporate this type of technology into industrial devices,” said Stephan Steinhauer, a Japan Society for the Promotion of Science (JSPS) postdoctoral research fellow working under the supervision of Prof. Mukhles Sowwan at the OIST Nanoparticles by Design Unit.

The researchers have provided this image showing their work,

Palladium nanoparticles were deposited on the entire wafer in an evenly distributed fashion, as seen in the background.  They also attached on the surface of the copper oxide wire in the same evenly distributed manner, as seen in the foreground.   On the upper right is a top view of a single palladium nanoparticle photographed with a transmission electron microscope(TEM) which can only produce black and white images. The nanoparticle is made up of columns consisting of palladium atoms stacked on top of each other.  Courtesy OIST

Palladium nanoparticles were deposited on the entire wafer in an evenly distributed fashion, as seen in the background. They also attached on the surface of the copper oxide wire in the same evenly distributed manner, as seen in the foreground.
On the upper right is a top view of a single palladium nanoparticle photographed with a transmission electron microscope(TEM) which can only produce black and white images. The nanoparticle is made up of columns consisting of palladium atoms stacked on top of each other. Courtesy OIST

Here’s a link to and a citation for the paper,

Single CuO nanowires decorated with size-selected Pd nanoparticles for CO sensing in humid atmosphere by Stephan Steinhauer, Vidyadhar Singh, Cathal Cassidy, Christian Gspan, Werner Grogger, Mukhles Sowwan, and Anton Köck. Nanotechnology 2015 Volume 26 Number 17 doi:10.1088/0957-4484/26/17/175502

This paper is behind a paywall.