|(Nanowerk News) Advanced plasma-based etching is a key enabler of Moore’s Law that observes that the number of transistors on integrated circuits doubles nearly every two years. It is the plasma’s ability to reproduce fine patterns on silicon that makes this scaling possible and has made plasma sources ubiquitous in microchip manufacturing.|
|A groundbreaking fabrication technique, based on what is called a DC-augmented capacitively coupled plasma source, affords chip makers unprecedented control of the plasma. This process enables DC-electrode borne electron beams to reach and harden the surface of the mask that is used for printing the microchip circuits. More importantly, the presence of the beam creates a population of suprathermal electrons in the plasma, producing the plasma chemistry that is necessary to protect the mask. The energy of these electrons is greater than simple thermal heating could produce—hence the name “suprathermal.” But how the beam electrons transform themselves into this suprathermal population has been a puzzle.|
|A plasma wave can give rise to a population of suprathermal electrons. (Credit: I.D. Kaganovich and D. Sydorenko)|
|Now a computer simulation developed at the U.S. Department of Energy’s Princeton|
|Plasma Physics Laboratory in collaboration with the University of Alberta has shed light on this transformation. The simulation reveals that the initial DC-electrode borne beam generates intense plasma waves that move through the plasma like ripples in water. And it is this beam-plasma instability that leads to the generation of the crucial suprathermal electrons.|
|Understanding the role these instabilities play provides a first step toward still-greater control of the plasma-surface interactions, and toward further increasing the number of transistors on integrated circuits. Insights from both numerical simulations and experiments related to beam-plasma instabilities thus portend the development of new plasma sources and the increasingly advanced chips that they fabricate.|
|55th Annual Meeting of the APS Division of Plasma Physics|
|TO6.00005 Collisionless acceleration of plasma electrons by intense electron beam|
|Session: Low Temperature Plasma Science, Engineering and Technology|
|9:30 AM–11:06 AM, Thursday, November 14, 2013|
|Source: American Physical Society|
12 Nov 2013
(Nanowerk Spotlight) Cancer is one of the leading causes of death in the world and remains a difficult disease to treat. Current problems associated with conventional cancer chemotherapies include insolubility of drugs in aqueous medium; delivery of sub-therapeutic doses to target cells; lack of bioavailability; and most importantly, non-specific toxicity to normal tissues. Recent contributions of nanotechnology research address possible solutions to these conundrums. Nevertheless, challenges remain with respect to delivery to specific sites, real time tracking of the delivery system, and control over the release system after the drug has been transported to the target site.
Nanomedical research on nanoparticles is exploring these issues and has already been showing potential solutions for cancer diagnosis and treatment. But a heterogeneous disease like cancer requires smart approaches where therapeutic and diagnostic platforms are integrated into a theranostic approach.
Theranostics – a combination of the words therapeutics and diagnostics – describes a treatment platform that combines a diagnostic test with targeted therapy based on the test results, i.e. a step towards personalized medicine. Making use of nanotechnology materials and applications, theranostic nanomedicine can be understood as an integrated nanotherapeutic system, which can diagnose, deliver targeted therapy and monitor the response to therapy.
Theranostic nanomedicine has the potential for simultaneous and real time monitoring of drug delivery, trafficking of drug and therapeutic responses.
Our Smart Materials and Biodevice group at the Biosensors and Bioelectronics Centre, Linkoping University, Sweden, has demonstrated for the first time a MRI-visual order-disorder micellar nanostructures for smart cancer theranostics.
The drug release mechanism via functional outcome of the pH response illustrated in the schematic diagram. (Image: Smart Materials and Biodevice group, Linköping University) In the report, we fabricated a novel pH-triggered tumour microenvironment sensitive order-disorder nanomicelle platform for smart theranostic nanomedicine.
The real-time monitoring of drug distribution will help physicians to assess the type and dosage of drug for each patient and thus will prevent overdose that could result in detrimental side-effects, or suboptimal dose that could lead to tumour progression.
Additionally, the monitoring of normal healthy tissues by differentiating with the MRI contrast will help balance the estimation of lethal dose (for normal tissue) and pharmacologically active doses (for tumour). As a result, this will help to minimize off-target effects and enhance effective treatment.
In the present report, the concurrent therapy by doxorubicin and imaging strategies by superparamagnetic iron oxide nanoparticles with our smart architecture will provide every detail and thus can enable stratification of patients into categorized responder (high/medium/low), and has the potential to enhance the clinical outcome of therapy.
It shows, for the first time, concentration dependent T2-weighted MRI contrast for a monolayer of clustered cancer cells. The pH tunable order-disorder transition of the core-shell structure induces the relative changes in MRI that will be sensitive to tumour microenvironment and stages.
A novel MRI visual order-disorder nanostructure for cancer nanomedicine explores pH-trigger mechanism for theranostics of tumour hallmark functions. The pH tunable order-disorder transition induces the relative changes in MRI contrast. The outcome elucidates the potential of this material for smart cancer theranostics by delivering non-invasive real-time diagnosis, targeted therapy and monitoring the course and response of the action. (Image: Smart Materials and Biodevice group, Linköping University)
Our findings illustrate the potential of these biocompatible smart theranostic micellar nanostructures as a nontoxic, tumour-target specific, tumour-microenvironment sensitive, pH-responsive drug delivery system with provision for early stage tumour sensing, tracking and therapy for cells over-expressed with folate receptors.
The outcomes elucidate the potential of smart cancer theranostic nanomedicine in non-invasive real-time diagnosis, targeted therapy and monitoring of the course and response of the action before, during and after treatment regimen.
By Hirak K Patra, Nisar Ul Khali, Thobias Romu, Emilia Wiechec, Magnus Borga, Anthony PF Turner and Ashutosh Tiwari, Biosensors and Bioelectronics Centre, Linköping University, Sweden
You might think that such a new ‘wonder material’ would lie outside your everyday experience, but graphene is the exception. When you write or draw with a pencil, the graphite (the ‘lead’ of the pencil) slides off in thin layers to leave a trail – the line on the paper. Carbon’s ability to form a thin layer of molecules is what makes graphene special – and scientists are starting to explore the possibilities for electronics and computing of carbon grids that are just one molecule thick.
The semiconductor industry is the basis of today’s high-tech economy, directly supporting over 100,000 jobs in Europe, and indirectly even more. This has been achieved through continued miniaturisation in ‘Complementary metal-oxide-semiconductor’ (CMOS) technology, based on silicon. But this model will only last for 10 or 15 more years.
The major challenge for the ICT industry is to find alternatives for information processing and storage beyond the limits of existing CMOS. There are good indications that graphene is a prime candidate for “Beyond CMOS” components, and is, despite its revolutionary nature, complementary to conventional CMOS technologies.
Graphene has been the subject of a scientific explosion since the ground-breaking experiments on this novel material less than 10 years ago, recognised by the Nobel Prize in Physics in 2010 awarded to Professor Andre Geim and Professor Kostya Novoselov, at the University of Manchester. The remarkable electrical properties of graphene may overcome the physical limits silicon faces as transistors shrink to ever-smaller sizes – providing solutions for the “Beyond CMOS” era, needed to meet the challenges of global competition.
Bringing together multiple disciplines and addressing research across a whole range of issues, from the fundamental understanding of material properties to graphene production, the GRAPHENE (1) Flagship was launched in October 2013. The proposed research includes electronics, spintronics, photonics, plasmonics and mechanics – all based on graphene.
Led by Professor Jari Kinaret, from Sweden’s Chalmers University, the Flagship involves over 126 academic and industrial research groups in 17 European countries, with 136 principal investigators, including four Nobel laureates. With an initial 30-month budget of EUR 54 million, the GRAPHENE consortium will grow to include another 20-30 groups through an open call for project proposals in November , worth up to a total of EUR 9 million.
‘Graphene production is obviously central to our project,’ said Prof. Kinaret at the launch, but key applications to be looked at include fast electronic and optical devices, flexible electronics, functional lightweight components and advanced batteries. Examples of new products enabled by graphene technologies include fast, flexible and strong consumer electronics, such as electronic paper and bendable personal communication devices, as well as lighter and more energy-efficient aeroplanes. In the longer term, graphene is expected to give rise to new computational paradigms and revolutionary medical applications, such as artificial retinas.
Setting sail: Graphene as FET flagship
Described by European Commission Vice-President Neelie Kroes as a ‘daring venture’, the ‘Future and emerging technologies’ (FET) flagships are visionary, large-scale, science-driven research initiatives which tackle scientific and technological challenges across scientific disciplines. These new instruments in EU research funding foster coordinated efforts between the EU and its Member States’ national and regional programmes, are highly ambitious, and rely on cooperation among a range of disciplines, communities and programmes – requiring support for up to 10 years. Following the start-up phase, running until March 2016 under the EU’s current ‘Seventh Framework Programme’ for research (FP7), the work will continue under the next programme, ‘Horizon 2020’, with an expected EUR 50 million per year for the Flagship project.
Graphene was chosen as a flagship following a competition between six pilot projects to investigate the areas with the greatest potential for sustained investment. As Mrs Kroes has said: ‘Europe’s position as a knowledge superpower depends on thinking the unthinkable and exploiting the best ideas. This multi-billion competition rewards home-grown scientific breakthroughs and shows that when we are ambitious we can develop the best research in Europe.’
The Flagship pilot for graphene, the GRAPHENE-CA (2) project, looked at how developments in this carbon-based material could revolutionise ICT and industry. The pilot project established a comprehensive scientific and technological roadmap to serve as the basis for the research agenda of the GRAPHENE Flagship – covering electronics, spintronics, photonics, plasmonics and mechanics, and supporting areas such as graphene production and chemistry. And this was the basis on which it was selected.
Now the Flagship is up and running, it already comprises a research team of dizzying scope . There are universities from Louvain in Belgium, Aalto in Finland, Lille and Strasbourg in France, Bremen, Chemnitz, Dresden and Hamburg in Germany, Ioannina in Greece, Dublin in Ireland, Trieste in Italy, Minho in Portugal, Barcelona and Castilla-La Mancha in Spain, Basel, Geneva and Zurich in Switzerland, Delft and Groningen in the Netherlands, and Cambridge, Manchester and Oxford in the United Kingdom. These are complemented by polytechnics and institutes of technology from Austria, Denmark, France, Germany, Greece, Italy, Poland, Spain, Sweden and Switzerland. In addition, there are industrial partners such as Nokia, Thales, Alcatel Lucent, Philips Technology, Airbus and ST Microelectronics. And this list accounts for only part of the participating organisations.
Their mission is to take graphene, and related layered materials, from the academic laboratories to society – revolutionising multiple industries and creating economic growth and new jobs in Europe.
‘The Commission, and all the academic and industrial partners of the Graphene Flagship, are all in this together. It is an unusually long-term commitment, and there will be challenges, let’s be clear about that,’ said Carl-Christian Buhr, member of the Cabinet of Mrs Kroes. ‘We need to bring in industry in such a way that ideas are taken up and lead to new products and markets. That’s the whole idea of the Flagship.’
Indeed, it includes a comprehensive set of complementary activities to achieve this, such as:
– An ERA-NET type of project, FLAG-ERA (3), to support the Flagship in the coordination of national research initiatives on graphene.
– A range of initiatives focused on spreading knowledge about graphene to the wider world. The Graphene Week , for example, is an annual forum bringing together hundreds of researchers to share their latest developments across disciplines – the next will be held in Gothenburg, Sweden, in June 2014. It aims to be a ‘gathering of the graphene tribe’, where discussions of fundamental science can meet exciting new applications.
– Graphene Connect is an interaction platform for academia and businesses promoting scientists to think outside the box and industries to develop end-user products based on graphene – this will include a number of industrial workshops, and sessions for business angels, entrepreneurs and venture capitalists to discuss potential graphene investment opportunities.
– Graphene Study is a European winter school on graphene that will help build a new generation of graphene researchers, as well as new direct communication channels between young researchers and academia-industry players. The first will be held in the Austrian Alps, on 2-7 February 2014.
Some of the EU’s previously funded graphene research is already delivering. The GRAND (4) project, which ended in December 2010, looked at whether graphene would still work its wonders when integrated with the silicon CMOS process.
Led by AMO in Germany, the project team set out to assess whether graphene really could bring conventional semiconductor technology into the “Beyond CMOS” era. The GRAND consortium developed ways of fabricating 2-dimensional graphene nanostructures (with widths of only 5 nm across) for use in electronics components. It was important to show that not only could such components function, but that they could be fabricated in a way that could be scaled up to industrial quantities.
As a result, the team designed a new type of transistor – with the concept published in the renowned journal ‘Applied Physics Letters’ – that could open new routes for graphene-based high-speed electronic and optoelectronic devices.
As part of the GRAND project, graphene has also been integrated into a non-volatile memory device that could be reduced to molecular sizes – a graphene memory measuring just 1×1 nm that retains the information stored in it even when power is turned off. The team fabricated more than 10 such devices – indicating their scalability.
Led by the Chalmers University of Technology, Sweden, the CONCEPTGRAPHENE (5) project set out to unlock the potential of depositing a thin layer of graphene on to a silicon carbide (SiC) base – aiming to develop scalable electronics with potential applications in ‘spintronics’ and ultra-accurate measuring devices. The team worked on fabricating large-scale graphene wafers that would allow for high-density electronic devices to be manufactured on a single silicon wafer. This type of technology will be needed for full-scale industrial manufacture of graphene-based components and devices in a way that is compatible with current industry techniques.
Having ended in September 2013, the project launched a start-up company that will produce graphene wafers. Graphensic AB is located in Linköping, Sweden. The company is a spin-off from Linköping University and produces high-quality, highly uniform, graphene on silicon carbide (SiC) using a patented ‘High-temperature graphene process’ – a growth method which produces a thin layer of graphene, even a single layer of atoms, on SiC.
More where that came from
But graphene is not the only innovative material that could transform electronics – the 2D-NANOLATTICES (6) project, ending in May 2014, is working on other graphite-like molecular-lattice structures based on different elements. These ‘nanolattices’ also have great potential to pave the way to ever-smaller, and more powerful, nano-electronic devices. In particular, ‘silicene’ (or ‘germanene’), the silicon or germanium equivalent of graphene, if they exist, may offer better compatibility with silicon processing.
Led by the National Center for Scientific Research ‘Demokritos’, in Greece, the project team aims to find ways to induce and stabilise the silicon and germanium and prove for the first time that silicene has a physical existence. By producing alternating layers weakly bonded between one another, each consisting of a single layer of atoms, this new material could serve as the elements of gates and other components in new, miniaturised 2D semiconductors.
Perhaps we are still in the early stages, but these look to be the first steps in a transformation of the way electronics devices are made – and in their abilities – with the potential to similarly transform the European high-tech industry and economy.
The projects featured in this article have been supported by the Seventh Framework Programme (FP7) for research.
(1) ‘Graphene-based revolutions in ICT and beyond’
(2) ‘Graphene-based nanoelectronic devices’
(3) ‘A flagship-supporting ERA-NET’
(4) ‘New electronics concept: wafer-scale epitaxial graphene’
(5) ‘Coordination Action for graphene-driven revolutions in ICT and beyond’
(6) ‘Strongly anisotropic Graphite-like semiconductor/dielectric 2D nanolattices’.
Links to project on CORDIS:
– FP7 on CORDIS
– GRAPHENE Flagship project factsheet on CORDIS
– GRAPHENE-CA project factsheet on CORDIS
– GRAND project factsheet on CORDIS
– CONCEPTGRAPHENE project factsheet on CORDIS
– 2D-NANOLATTICES project factsheet on CORDIS
Links to projects’ websites:
– ‘Graphene-based revolutions in ICT and beyond’ project website
– ‘Coordination Action for graphene-driven revolutions in ICT and beyond’ website
– ‘Graphene-based nanoelectronic devices’ website
– ‘New electronics concept: wafer-scale epitaxial graphene’ website
– ‘Strongly anisotropic Graphite-like semiconductor/dielectric 2D nanolattices’ website
Links to related news and articles:
– ‘Feature Stories – Meet the pioneers of future and emerging technology’
– EC press release: Graphene and Human Brain Project win largest research excellence award in history
– GRAPHENE Flagship launch press release
09 Nov 2013
Asymmetrical particles could make lab-on-a-chip diagnostic devices more efficient and portable.
Anne Trafton, MIT News Office
MIT chemical engineers have designed tiny particles that can “steer” themselves along preprogrammed trajectories and align themselves to flow through the center of a microchannel, making it possible to control the particles’ flow through microfluidic devices without applying any external forces.
Such particles could make it more feasible to design lab-on-a-chip devices, which hold potential as portable diagnostic devices for cancer and other diseases. These devices consist of microfluidic channels engraved on tiny chips, but current versions usually require a great deal of extra instrumentation attached to the chip, limiting their portability.
Much of that extra instrumentation is needed to keep the particles flowing single file through the center of the channel, where they can be analyzed. This can be done by applying a magnetic or electric field, or by flowing two streams of liquid along the outer edges of the channel, forcing the particles to stay in the center.
The new MIT approach, described in Nature Communications, requires no external forces and takes advantage of hydrodynamic principles that can be exploited simply by altering the shapes of the particles.
Lead authors of the paper are Burak Eral, an MIT postdoc, and William Uspal, who recently received a PhD in physics from MIT. Patrick Doyle, the Singapore Research Professor of Chemical Engineering at MIT, is the senior author of the paper.
The work builds on previous research showing that when a particle is confined in a narrow channel, it has strong hydrodynamic interactions with both the confining walls and any neighboring particles. These interactions, which originate from how particles perturb the surrounding fluid, are powerful enough that they can be used to control the particles’ trajectory as they flow through the channel.
View Video on YouTube Here:
The MIT researchers realized that they could manipulate these interactions by altering the particles’ symmetry. Each of their particles is shaped like a dumbbell, but with a different-size disc at each end.
When these asymmetrical particles flow through a narrow channel, the larger disc encounters more resistance, or drag, forcing the particle to rotate until the larger disc is lagging behind. The asymmetrical particles stay in this slanted orientation as they flow.
Because of this slanted orientation, the particles not only move forward, in the direction of the flow, they also drift toward one side of the channel. As a particle approaches the wall, the perturbation it creates in the fluid is reflected back by the wall, just as waves in a pool reflect from its wall. This reflection forces the particle to flip its orientation and move toward the center of the channel.
Slightly asymmetrical particles will overshoot the center and move toward the other wall, then come back toward the center again until they gradually achieve a straight path. Very asymmetrical particles will approach the center without crossing it, but very slowly. But with just the right amount of asymmetry, a particle will move directly to the centerline in the shortest possible time.
“Now that we understand how the asymmetry plays a role, we can tune it to what we want. If you want to focus particles in a given position, you can achieve that by a fundamental understanding of these hydrodynamic interactions,” Eral says.
“The paper convincingly shown that shape matters, and swarms can be redirected provided that shapes are well designed,” says Patrick Tabeling, a professor at the École Supérieure de Physique et de Chimie Industrielles in Paris, who was not part of the research team. “The new and quite sophisticated mechanism … may open new routes for manipulating particles and cells in an elegant manner.”
Diagnosis by particles
In 2006, Doyle’s lab developed a way to create huge batches of identical particles made of hydrogel, a spongy polymer. To create these particles, each thinner than a human hair, the researchers shine ultraviolet light through a mask onto a stream of flowing building blocks, or oligomers. Wherever the light strikes, solid polymeric particles are formed in the shape of the mask, in a process called photopolymerization.
During this process, the researchers can also load a fluorescent probe such as an antibody at one end of the dumbbell. The other end is stamped with a barcode — a pattern of dots that reveals the particle’s target molecule.
This type of particle can be useful for diagnosing cancer and other diseases, following customization to detect proteins or DNA sequences in blood samples that can be signs of disease. Using a cytometer, scientists can read the fluorescent signal as the particles flow by in single file.
“Self-steering particles could lead to simplified flow scanners for point-of-care devices, and also provide a new toolkit from which one can develop other novel bioassays,” Doyle says.
The research was funded by the National Science Foundation, Novartis, and the Institute for Collaborative Biotechnologies through the U.S. Army Research Office.
07 Nov 2013
West Australian researchers have developed an advanced water decontamination process that turns toxic wastewater into near rainwater quality and which they believe could help Japan in its extensive clean-up of nuclear contaminated waters.
CSIRO scientist Grant Douglas visited the country in September and with assistance from Austrade has submitted a proposal to use CSIRO’s Virtual Curtain technology for widespread remediation work in Japan, estimated to be worth hundreds of millions of dollars.
He says water tanks, flooded buildings and basements in Fukushima remain highly contaminated after the meltdown of the power plant nuclear reactors in 2011.
“They need to clean those up and that’s proving difficult because they have such a wide range of contaminants,” Dr Douglas says.
“They can’t generally employ one technique—they need multiple ones, whereas our technology has the advantage that it can clean up a lot of contaminants in one step.”
“This is a severe environmental liability at the moment; what we’ll be doing is treating water that’s highly acidic and full of all sorts of toxic metals metalloids, arsenic and other things,” he says.
“The water we produce from that is virtually drinking-quality except for the salt level.
“That is then going through a reverse osmosis plant to remove the salt and that effluent – which will be released into a river – is actually going to be better quality water than is now in the river. It’ll be like rainwater.”
The Virtual Curtain technology is patented by CSIRO and made commercial through the company Virtual Curtain Limited.
It uses hydrotalcites; layered minerals consisting of aluminium and magnesium-rich-layers, separated by interlayers of anions (negatively charged molecules like sulphate).
During the process the aluminium and magnesium can be replaced by a range of other metals like copper and lead as the hydotalcites form. The metals and anions are then trapped and easily removed from wastewater as a solid.
Dr Douglas says lime has been used traditionally to decontaminate wastewater but among its drawbacks it requires a number of complex steps and produces enormous amounts of sludge.
“The technique I have produces just 10 per cent or less of the sludge that lime does which is then far more concentrated as a result, and has potential to turn what was wastewater back into an ore; they can re-mine it.”
07 Nov 2013
Re-closable anticorrosion containers: The capsules open when they are reduced and potassium ions migrate into the polymer shell. As soon as the corrosion comes to a halt, the polymer is oxidised, the capsules close and release potassium ions again.
A particularly ingenious remedy for the problem of rust may be available soon. Scientists from the Max-Planck-Institut für Eisenforschung GmbH in Düsseldorf and the Max Planck Institute for Polymer Research in Mainz have succeeded in making two enormous strides towards developing a self-healing anticorrosion coating. In one study, they embedded a few 100-nanometre-sized polymer capsules containing anticorrosion payloads in a coating. They applied the coating to a metal and exposed the metal to corrosion through a crack in the coating. Thereupon, the capsules opened and released the protective payloads. As soon as the corrosive attack ended, the containers closed again. In the second study, the researchers encapsulated substances in nanocontainers that can heal small cracks and holes in the protective metal coating. The researchers thereby demonstrated that the containers were chemically altered and released the healing payloads when the corrosion process started. The containers then closed again at the end of the corrosive attack.
Human and animal skin is exemplary in many respects. Materials scientists are impressed above all by the way in which it heals itself when damaged. They would like to endow anticorrosion coatings with this very capacity, so that fine cracks and small holes in coatings do not spell disaster in the short or long term for the underlying metal. “We have made two breakthroughs in the quest for intelligent corrosion protection,” reports Michael Rohwerder, Leader of a Research Group at the Max-Planck-Institut für Eisenforschung.
Together with their colleagues from the Max Planck Institute for Polymer Research, the Düsseldorf-based researchers tested capsules made from the conductive polymer polyaniline as containers for anticorrosive substances. They had decorated the nanocapsules with metal nanoparticles to generate suitable electrical contact between the containers and the metal to which they applied the capsules as components in a coating. Through a defect in the protective coating, they exposed the metal to corrosion by trickling a drop of salty water onto the opening in the protective coating. The corrosive attack, however, had no effect, as the walls of the polymer capsules became porous, allowing the substances contained in them to escape, which then blocked the oxygen reduction process.
The electrochemical potential is the most reliable key for opening the capsules
“What is crucial here is to select the correct signal for opening the capsule wall,” says Michael Rohwerder. The capsules can thus be opened purely mechanically when the protective coating is scratched. Or they can react to a rising pH value, which can accompany the process of corrosion. However, the Max Planck team opted to exploit the electrochemical potential as a capsule opener that punctured the polyaniline cover through a process of chemical conversion. “This potential always falls when corrosion starts,” explains Rohwerder. “So it provides the most reliable signal for the capsules to open.” Moreover, electrical contact is required for the capsules to recognise the electrochemical alarm as well. This is provided by the metal nanoparticles between the capsule wall and the metal. The capsules detect when the corrosion has stopped through the same information channel, as the potential rises constantly at this point. The capsule wall then restructures itself and the pores are re-sealed.
The containers, in which the researchers enclosed payloads can be used to form a polymer skin. These payloads can polymerise in a defect and seal the crack or hole. However, in this study the scientists did not apply the capsules to a metal using a coating to test them for corrosion. They replicated the chemical conditions that exist at the beginning and end of the corrosion process with reducing and oxidising substances and opened or closed the capsules in this way. “We were able to repeat this redox process with the polyaniline capsules over 80 times,” says Daniel Crespy, a Research Group Leader at the Max Planck Institute for Polymer Research, who supervised the study.
Oily fluids can be encapsulated in a miniemulsion
The fact that the healing substances can be encapsulated in a targeted way is of particular interest from the chemist’s perspective. This is made possible by a technique developed by researchers working with Katharina Landfester at the Max Planck Institute for Polymer Research in Mainz. They produce an emulsion from an aqueous solution, in which drops of oil float. A process that only functions to a limited extent with milk – after a while the cream accumulates on the top – was perfected by the chemists. In their miniemulsion, not only are the drops of oil similarly small in size, but they remain, thanks to a few chemical tricks, almost completely stable.
Before Daniel Crespy and his colleagues finely emulsify the oily fluid in the aqueous solution by mixing it and using ultrasound, they add the components for the polymer capsules to it. The components only react to produce long chain molecules when the chemists trickle another chemical ingredient into the prepared emulsion, which dissolves in water and triggers the polymerisation precisely on the surface of the oil drops. “This is how we can encapsulate oily fluids in an aqueous environment,” says Daniel Crespy. However, despite sounding like a simple recipe, the finer details of process are actually very difficult to implement. During the polymerisation, the chemical milieu of the emulsion changes so that the drops of oil tend to aggregate and would normally accumulate on top of the water. “But we found a way of stabilising the emulsion,” says Crespy.
The anticorrosion substances must be made more effective
Moreover, it is not exactly easy to prove that the capsules only release the remedy for healing the defects in a coating when necessary. To this end, the researchers in Mainz had to isolate the capsules after each step, displace them with suitable solvents and examine them with the help of nuclear magnetic resonance spectroscopy, which provided information about the volumes of the substances contained in the capsules.
In the two recent studies, the team of researchers from Düsseldorf and Mainz endowed the nanocapsules with some of the functions that a self-healing corrosion coating would have to provide. “We now want to enclose the healing substances and the anticorrosion substances together in the same capsules,” says Crespy, as only both substances combined can provide comprehensive protection against the destruction caused by rust. Whereas the anticorrosion substances quickly stem the corrosion, like the initial halting of the blood flow in the case of injury, the healing substances restore the enduring anticorrosive effect of the coating. However, like a healing wound, they need more time to do their work. “Up to now, it has not been possible to encapsulate both substances under the same chemical conditions,” says Daniel Crespy. This is what he and his colleagues would like to achieve.
Michael Rohwerder has also identified two further challenges that must still be overcome before the self-healing anticorrosion system is complete. “First, we must identify inhibiting substances which are as effective, for example, as chromates,” says the scientist. Chromates still set the standard in terms of anticorrosion coatings at present; however, they are being banned in an increasing number of applications due to their toxicity. “Second, we must ensure that the healing substances reach a defect faster and in greater quantities,” says Rohwerder. Up to now, they have been held back by the fact that they are not very water-soluble; corrosion, however, only occurs when a defect is exposed to water. If the researchers succeed in making progress on these issues, it is entirely possible that metal coatings will be the equal of living skin when it comes to powers of self-healing.
Explore further: A self-healing protective coating for concrete
Animal and plant cells are prominent examples of how nature constructs ever-larger units in a targeted, preprogrammed manner using molecules as building blocks. In nanotechnology, scientists mimic this ‘bottom-up‘ technique by using the ability of suitably structured nano materials to ‘self-assemble‘ into higher order architectures. Applying this concept, polymer scientists from Bayreuth, Aachen, Jena, Mainz, and Helsinki have recently published an article in the prestigious journal Nature that describes a new principle for the self-assembly of patterned nanoparticles. This principle may have important implications for the fundamental understanding of such processes as well as future technologies.
Animal and plant cells are prominent examples of how nature constructs ever-larger units in a targeted, preprogrammed manner using molecules as building blocks. In nanotechnology, scientists mimic this ‘bottom-up’ technique by using the ability of suitably structured nano materials to ‘self-assemble’ into higher order architectures. Applying this concept, polymer scientists from Bayreuth, Aachen, Jena, Mainz, and Helsinki have recently published an article in the prestigious journal Nature that describes a new principle for the self-assembly of patterned nanoparticles. This principle may have important implications for the fundamental understanding of such processes as well as future technologies.
However, the process of self-assembly does not end with the nanoparticles. If the nanoparticles formed by each type of macromolecule were left to their own, spherical superstructures would result on the one hand and linear superstructures on the other. Müller’s team has developed and implemented a different approach. The nanoparticles with one and two bonding sites are mixed so that they aggregate together into a completely new superstructure in a process of co-assembly. In the final superstructure, the nanoparticles originating from the A-B-C molecules and nanoparticles formed by the A-D-C molecules alternate in a precisely defined pattern.
When viewed under a transmission electron microscope, the new superstructure bears a strong resemblance to a caterpillar larva, because it also consists of a series of clearly separate, regularly ordered sections. Müller’s research team has thus coined the term “caterpillar micelles” for such co-assembled superstructures.
The research findings recently published in Nature represent a breakthrough in the field of hierarchical structuring and nano-engineering as it allows creating new materials by self-assemble preprogrammed particles. This could be a game changer, because so far only top-down procedures, i.e., extracting a microstructure from a larger complex, are widely accepted structuring processes. “The limitations of this technique will become all too apparent in the near future,” explained Müller. “Only rarely is it possible to generate complex structures in the nanometer range.”
However, a bottom-up principle of self-assembly based on that employed in nature could well represent the best way forward. One factor that makes this particularly attractive is the large number of macromolecules, which are readily available as building blocks. They can be used to incorporate specific properties in the resultant superstructures, such as sensitivity to environmental stimuli (e.g. temperature, light, electric and magnetic fields, etc.) or give them the ability to be switched on and off at will. Possible applications include nanolithography and the delivery of drugs in which the time and site of release of active substances can be preprogrammed. Here, the similarity to the structural principles of animal and plant cells becomes apparent again, where various properties are compartmentalized into areas of limited space.
The macromolecules carrying diverse functional segments can be hundreds of times smaller than a micrometer. The superstructures that such macromolecules produce have correspondingly high resolution. “Future technologies – such as tailor-made artificial cells, transistors, or components for micro/nano-robotics – may benefit significantly from this particularly delicate structuring,” explained Müller. “The research findings we published in Nature do not yet have any immediate real-world applications. Nevertheless, the better we understand bottom-up processes starting with molecules in the nanometer range and moving on to the higher hierarchical levels in the micrometer range, the more likely future technologies will be within our grasp.” The caterpillar micelles are in no way the only superstructures that can be produced with the self-assembling nanoparticles. “Such soft nanoparticles can be combined with inorganic or biological nano- and microparticles to create previously unknown materials with specific functions. The number of possible combinations is practically endless,” concluded Müller.
07 Nov 2013
SAN MARCOS, Texas, Nov. 7, 2013 /PRNewswire/ – Quantum Materials Corp. announced today that it has provided Tetrapod Quantum Dots (TQD) to an advanced medical device manufacturer to optimize performance of an “engineered spectrum” quantum dot-enabled light source to better provide useful data to researchers and practitioners that has not been easily discernible until now.
David Doderer, Vice President of R&D, explained, “We are fulfilling specific requests for tetrapod quantum dots, in this case, to create tailored light for investigation of tissue. Differences between healthy and suspect tissue often can be better identified if the available fluorophores’ color combination is engineered for either true representation of color, or emphasized in the visible spectrum depending on the tissue type. I think our bespoke tetrapod quantum dots provide the depth of data necessary to highlight subtle differences that researchers and healthcare professionals need to efficiently understand disease and devise effective treatments.”
To achieve efficient healthcare in an increasingly demanding marketplace, the ability to get actionable information is crucial. Medical diagnostic assays currently count in the multi-millions per year and per country, and differences in tissues types at the cellular level are critically important for accuracy in results. Conventional organic dyes and other types of fluorophores are currently used for luminescence in assays by researchers, but they have limitations sometimes preventing clear distinctions in reading the data. Broad data sets can tend to obscure patterns that might become clear by removing these uncertainties.
Tetrapod quantum dots address this issue well for biochemical detection and biomedical device application by providing a broad array of colors, which translates to increased number of pieces in the data set, and also precise tune-ability and stability for high contrast and distinctive identification certainty. For biochemical detection, most typically in a rapid assay that provides a breadth of data in a single test kit, Quantum Materials has begun conversations with biotech researchers and companies needing narrow color emissions to provide clear identification when identifying particular targets by attaching to the desired organism or cell type when specifically functionalized.
As part of this effort, the Company is developing a suitable TQD film for medical devices while maintaining consistency in both uniformity and scalability. The Company believes this technology, one of several under review, could also successfully translate into Tetrapod Quantum Dot film applications such as general light applications, electronic displays and quantum dot solar cells.
Quantum Materials Corp. manufactures Tetrapod Quantum Dots for use in medical, display, solar energy and lighting applications through patent pending continuous-flow production process. Quantum dot semiconductors enable a new level of engineered performance in a wide array of established consumer and industrial products. QMC’s volume manufacturing methods enable consistent QD quality and scalable cost reductions to drive innovative discovery to commercial success.
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Materials science and nanotechnology students at the University of Alberta have recently joined more than 70 universities across the world in becoming members of the internationally known Materials Research Society (MRS).
The newly established MRS chapter at the U of A is the first in Canada and will set an example for other universities in the country to follow, according to its founding member.
Rokib Hassan, PhD student and president of the U of A MRS chapter, said it’s becoming increasingly important for students to get involved with these global organizations, as they help foster a sense of leadership in their fields.
“What happens is the (students can) boost their research and commit to working with the materials research or nanotechnology communities,” he said.
“They’re trying to create a field or a platform for their students, so that they can become more passionate to pursue their interests or their research in the areas of materials research or nanotechnology.”
The idea to establish a chapter at the U of A came to Hassan when he travelled to Cancun for an MRS conference and saw the types of schools that were represented — some of the largest, most prestigious American universities had established chapters, he said, but no Canadian schools.
“I was quite shocked when I went there,” Hassan said. “I started thinking, ‘Why not from Canada?’ We are just beside the U.S., and if the U.S. are leading all the (research), why not Canada?”
Hassan said when he began the process of founding the U of A chapter, he received positive responses from the community, quickly gathering interested undergraduate students, graduate students and faculty members in a matter of weeks.
Going forward, the new chapter aims to host its own symposium next year, and eventually create undergraduate funding and a summer research program. Hassan said the chapter, like the ever-changing fields of nanotechnology and materials science, is looking to build the future.
“In the future, everything is coming up to the materials science and nanotechnology, if you think about making all the devices for your iPhone or smartphone,” he said.“Everything is coming into the materials science and nanotechnology (area).”
Researchers from the National Institute of Standards and Technology (NIST) have joined with an international team to engineer and measure a potentially important new class of nanostructured materials for microwave and advanced communication devices.
Based on NIST’s measurements, the new materials—a family of multilayered crystalline sandwiches—might enable a whole new class of compact, high-performance, high-efficiency components for devices such as cellular phones.*
Not a brick wall. Electron microscope image of a cross section of the newly characterized tunable microwave dielectric clearly shows the thick layers of strontium titanate “bricks” separated by thin “mortar lines” of strontium oxide that help promote the largely defect-free growth of the bricks.
Credit: TEM image courtesy David Mueller. Color added for clarity by Nathan Orloff. high resolution version
“These materials are an excellent example of what the Materials Genome Initiative refers to as ‘materials-by-design’,” says NIST physicist James Booth, one of the lead researchers. “Materials science is getting better and better at engineering complex structures at an atomic scale to create materials with previously unheard-of properties.”
The new multilayer crystals are so-called “tunable dielectrics,” the heart of electronic devices that, for example, enable cell phones to tune to a precise frequency, picking a unique signal out of the welter of possible ones.
Tunable dielectrics that work well in the microwave range and beyond—modern communications applications typically use frequencies around a few gigahertz—have been hard to make, according to NIST materials scientist Nathan Orloff. “People have created tunable microwave dielectrics for decades, but they’ve always used up way too much power.” These new materials work well up to 100 GHz, opening the door for the next generation of devices for advanced communications.
Modern cellphone dielectrics use materials that suffer from misplaced or missing atoms called “defects” within their crystal structure, which interfere with the dielectric properties and lead to power loss. One major feature of the new materials, says Orloff, is that they self-correct, reducing the effect of defects in the part of the crystal where it counts. “We refer to this material as having ‘perfect faults’,” he says. “When it’s being grown, one portion accommodates defects without affecting the good parts of the crystal. It’s able to correct itself and create perfect dielectric bricks that result in the rare combination of high tuning and low loss.”
The new material has layers of strontium oxide, believed to be responsible for the self-correcting feature, separating a variable number of layers of strontium titanate. Strontium titanate on its own is normally a pretty stable dielectric—not really tunable at all—but another bit of nanostructure wizardry solves that. The sandwich layers are grown as a thin crystalline film on top of a substrate material with a mismatched crystal spacing that produces strain within the strontium titanate structure that makes it a less stable dielectric—but one that can be tuned. “It’s like putting a queen-sized sheet on a king-sized bed,” says Orloff. “The combination of strain with defect control leads to the unique electronic properties.”
One key discovery by the research team was that, in addition to adding strain to the crystal sandwich, adding additional layers of strontium titanate in between the strontium oxide layers increased the room-temperature “tunability” performance of the structure, providing a new mechanism to control the material response. The material they reported on recently in the journal Nature has six layers of strontium titanate between each strontium oxide layer.
The new sandwich material performs so well as a tunable dielectric, over such a broad range of frequencies, that the NIST team led by Booth had to develop a new measurement technique—an array of test structures fabricated on top of the test film—just to measure its electronic characteristics. “We were able to characterize the performance of these materials as a function of frequency running from 10 hertz all the way up to 125 gigahertz. That’s the equivalent of measuring wavelengths from kilometers down to microns all with the same experimental set-up,” says Orloff, adding, “This material has a much lower loss and a much higher tunability for a given applied field then any material that we have seen.”
An international team of researchers contributed to the recent paper, representing, in addition to NIST, Cornell University, the University of Maryland, Pennsylvania State University, the Institute of Physics ASCR (Czech Republic), Universitat Politècnica de Catalunya (Spain), the Kavli Institute at Cornell for Nanoscale Science, Oak Ridge National Laboratory, the Leibniz Institute for Crystal Growth (Germany), The University of Texas at Austin and Temple University.
Contact: Michael Baum 301-975-2763
For additional perspective, see the Cornell University news story, “Tunable antenna could end dropped cell phone calls” at www.news.cornell.edu/stories/2013/10/tunable-antenna-could-end-dropped-cell-phone-calls. For more on the MGI at NIST, see www.nist.gov/mgi/index.cfm.