Tag Archives: Vienna University of Technology

Rust shocks scientists

Researchers at the Vienna University of Technology have made a surprising discovery about a well established atomic structure on magnetite surfaces (rust), according to a Dec. 4, 2014 news item on ScienceDaily,

Magnetite (or Fe3O4) is an elaborate kind of rust — a regular lattice of oxygen and iron atoms. But this material plays an increasingly important role as a catalyst, in electronic devices and in medical applications.

Scientists at the Vienna University of Technology have now shown that the atomic structure of the magnetite surface, which everybody had assumed to be well-established, has in fact been wrong all along. The properties of magnetite are governed by missing iron atoms in the sub-surface layer. “It turns out that the surface of Fe3O4 is not Fe3O4 at all, but rather Fe11O16,” says Professor Ulrike Diebold, head of the metal-oxide-research group at TU Wien (Vienna). The new findings have now been published in the journal Science.

A Dec. 5, 2014 Vienna University of Technology press release, which despite the date appears to have originated the news item, describes the process which resulted in the researchers changing how they thought about the surface chemistry and physics they were examining,

Perhaps the most surprising property of the magnetite surface is that single atoms placed on the surface, for instance gold or palladium, stay perfectly in place instead of balling up and forming a nanoparticle. This effect makes the surface an extremely efficient catalyst for chemical reactions – but nobody had ever been able to tell why magnetite behaves that way. “Also, Fe3O4-based electronics never function quite as well as they should”, says Gareth Parkinson (TU Wien). “Because materials interact with their environment through the surface, it’s really important to understand the structure of the surface and why it forms.”

Very often, the properties of metal oxides depend on oxygen vacancies in the topmost atomic layers. Depending on the environment, some oxygen atoms on the surface may be missing. This can dramatically influence the electronic properties of the material. “Everyone in our community thinks about missing oxygen atoms. That is why it took us quite a while to figure out that it is in fact missing iron atoms that do the trick”, says Gareth Parkinson.

It’s not the oxygen, it’s the metal

Developing this new understanding, further the scientists proposed a new theory (from the press release),

Instead of a fixed structure of metal atoms with built-in oxygen atoms, one rather has to think of iron-oxides as a well-defined oxygen structure with little metal atoms hiding inside. Directly below the outermost atomic layer, the crystal structure is rearranged and some iron atoms are absent.

It is precisely above such places of missing iron atoms that other metal atoms attach. These iron-vacancy-sites are regularly spaced, and so there is always some well-defined distance between gold or palladium atoms attaching to the surface. This explains why magnetite surfaces prevent these atoms from forming clusters.

The idea of completely re-thinking the crystal structure of magnetite was rather bold, and therefore the scientists analysed their theory very carefully. Quantum simulations were carried out on large supercomputers to show that the proposed structure was indeed physically reasonable. After that, electron diffraction measurements were done together with researchers at the University of Erlangen-Nuremberg, Germany.

“By scattering slow electrons at surfaces, one can measure how well the actual crystal structure of the material agrees with a theoretical model”, says Ulrike Diebold. This agreement is quantified by the so-called “R-value”. “For very well-known structures, one may achieve an R-value of 0.1 or 0.15. For magnetite, nobody had ever managed to get anything better than 0.3, and people said it just could not be done.” But the new magnetite structure with missing iron atoms agrees very well with the experimental data, yielding an R-value of 0.125.

This new theory may apply to more than one metal oxide (from the press release),

Metal oxides are widely known to be technologically important but extremely complicated to describe. “Our results show that there is no need to despair. Metal oxides can be modelled quite accurately after all, but maybe not in the way one might expect at first glance”, says Gareth Parkinson. The scientists expect that their findings do not just apply to iron oxide but also to oxides of cobalt, manganese or nickel. Re-thinking their crystal structures could possibly boost iron-oxide research in many areas and lead to applications in chemical catalysis, electronics or medicine.

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

Subsurface cation vacancy stabilization of the magnetite (001) surface by R. Bliem, E. McDermott, P. Ferstl, M. Setvin, O. Gamba, J. Pavelec, M. A. Schneider, M. Schmid, U. Diebold, P. Blaha, L. Hammer, and G. S. Parkinson. Science 5 December 2014: Vol. 346 no. 6214 pp. 1215-1218 DOI: 10.1126/science.1260556

This paper is behind a paywall.

It’s an ‘Alice in Wonderland’ world where a particle can be separated from its properties

In a joint research project, French, Austrians, and American researchers have achieved a state described in Lewis Carroll’s well loved story, Alice in Wonderland. (Three of the four institutions involved have issued news releases, as this is the only one to feature a quote from Alice in Wonderland describing the state, it gets mentioned first.) From a July 29, 2014 Chapman University news release on EurekAlert,

… “Well! I’ve often seen a cat without a grin,” thought Alice in Wonderland, “but a grin without a cat! It’s the most curious thing I ever saw in my life!” Alice’s surprise stems from her experience that an object and its property cannot exist independently. It seems to be impossible to find a grin without a cat. However, the strange laws of quantum mechanics (the theory which governs the microscopic world of atoms; and the most successful theory in history) tell us that it is indeed possible to separate a particle from its properties—a phenomenon which is strikingly analogous to the Cheshire Cat story. The quantum Cheshire Cat is the latest example of how strange quantum mechanics becomes when viewed through the lens of one of Aharonov’s fundamental discoveries called the “weak measurement.”

Modesty does not favour contemporary research and educational institutions and, as is common in situations where there’s significant scientific excitement with a number of collaborators, the cooperating institutions are angling to establish the importance of their institutions and/or researchers’ contributions.

Here’s more from the Chapman  University news release where it establishes its claim to the theory,

The idea of the Quantum Cheshire Cat was first discovered by Chapman’s Prof. Yakir Aharonov and first published by Aharonov’s collaborator, Prof. Jeff Tollaksen (also at Chapman University), in 2001. Aharonov’s team, including Sandu Popescu (University of Bristol and Chapman’s Institute for Quantum Studies) and Daniel Rorhlich (Ben Gurion University), continued to develop the Cheshire Cat theory in more recent publications.

A July 29, 2014 Vienna University of Technology news release on EurekAlert provides this description and its claim to inventing the technique used in the latest experimental work,

According to the law of quantum physics, particles can be in different physical states at the same time. If, for example, a beam of neutrons is divided into two beams using a silicon crystal, it can be shown that the individual neutrons do not have to decide which of the two possible paths they choose. Instead, they can travel along both paths at the same time in a quantum superposition.

“This experimental technique is called neutron interferometry”, says Professor Yuji Hasegawa from the Vienna University of Technology. “It was invented here at our institute in the 1970s, and it has turned out to be the perfect tool to investigate fundamental quantum mechanics.”

A July 29, 2014 Institut Laue-Langevin (international research institute located in Grenoble, France) news release on EurekAlert establishes its claim as the location for the experimental work,

Researchers from the Vienna University of Technology have performed the first separation of a particle from one of its properties. The study, carried out at the Institute Laue-Langevin (ILL) and published in Nature Communications, showed that in an interferometer a neutron’s magnetic moment could be measured independently of the neutron itself, thereby marking the first experimental observation of a new quantum paradox known as the ‘Cheshire Cat’. The new technique, which can be applied to any property of any quantum object, could be used to remove disturbance and improve the resolution of high precision measurements.

The fourth collaborating institution (l’Université de Cergy-Pontoise) does not seem to have issued a news release in either French or English as per my August 8, 2014 searches.

The research itself is quite fascinating and it’s worth reading all three news releases for additional nuggets information hidden amongst the repetitive bits. Here’s a description you’ll find in both the Vienna University of Technology and Chapman University news releases,

Neutrons are not electrically charged, but they carry a magnetic moment. They have a magnetic direction, the neutron spin, which can be influenced by external magnetic fields.

First, a neutron beam is split into two parts in a neutron interferometer. Then the spins of the two beams are shifted into different directions: The upper neutron beam has a spin parallel to the neutrons’ trajectory, the spin of the lower beam points into the opposite direction. After the two beams have been recombined, only those neutrons are chosen, which have a spin parallel to their direction of motion. All the others are just ignored. “This is called postselection”, says Hermann Geppert. “The beam contains neutrons of both spin directions, but we only analyse part of the neutrons.”

These neutrons, which are found to have a spin parallel to its direction of motion, must clearly have travelled along the upper path – only there, the neutrons have this spin state. This can be shown in the experiment. If the lower beam is sent through a filter which absorbs some of the neutrons, then the number of the neutrons with spin parallel to their trajectory stays the same. If the upper beam is sent through a filter, than the number of these neutrons is reduced.

Things get tricky, when the system is used to measure where the neutron spin is located: the spin can be slightly changed using a magnetic field. When the two beams are recombined appropriately, they can amplify or cancel each other. This is exactly what can be seen in the measurement, if the magnetic field is applied at the lower beam – but that is the path which the neutrons considered in the experiment are actually never supposed to take. A magnetic field applied to the upper beam, on the other hand, does not have any effect.

“By preparing the neurons in a special initial state and then postselecting another state, we can achieve a situation in which both the possible paths in the interferometer are important for the experiment, but in very different ways”, says Tobias Denkmayr. “Along one of the paths, the particles themselves couple to our measurement device, but only the other path is sensitive to magnetic spin coupling. The system behaves as if the particles were spatially separated from their properties.”

Here’s an illustration the researchers have provided,

Caption: The basic idea of the Quantum Cheshire Cat: In an interferometer, an object is separated from one if its properties -- like a cat, moving on a different path than its own grin. Credit: TU Vienna / Leon Filter

Caption: The basic idea of the Quantum Cheshire Cat: In an interferometer, an object is separated from one if its properties — like a cat, moving on a different path than its own grin.
Credit: TU Vienna / Leon Filter

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

Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment by Tobias Denkmayr, Hermann Geppert, Stephan Sponar, Hartmut Lemmel, Alexandre Matzkin, Jeff Tollaksen, & Yuji Hasegawa. Nature Communications 5 Article number: 4492 doi:10.1038/ncomms5492 Published 29 July 2014

This is an open access paper.

Perhaps in response to concerns about the importance of theoretical physics, Chapman University’s Jeff Tollaksen offers this about possible applications  (from the Chapman University news release),

Co-Director of the Institute for Quantum Studies, Prof. Jeff Tollaksen has said: “Theoretical physics has yielded the most significant benefits for our society at the lowest costs. Discoveries in fundamental physics often lead to new industries: from electricity to smartphones to satellites. Quantum physics resulted in technological advances that drive our economy, such as the entire computer revolution, electronics, and the nuclear power industry. In addition, it impacts many other disciplines such as genetics, medicine and mathematics. Experts therefore estimate that nearly half the wealth created in the 20th century arose from quantum physics. At the Institute, we’re committed to producing the next generation of breakthroughs which will lead to the technology of the 21st century. Similarly, I’m sure this breakthrough will lead to many new applications including revised intuitions which can then serve as a guide to finding novel quantum effects.” This “Quantum Cheshire Cat” could be used for practical applications. For example, it could be used to make high precision measurements less sensitive to external perturbations. The measurements which now have been published in Nature Communications are the first experimental proof of this phenomenon.

By contrast the Europeans offer this,

With their landmark observation suitably vindicated, questions turn to the potential impact of their fundamental discovery. One application might high precision measurements of quantum systems which are often affected by disturbance.  [from the Institut Laue-Langevin news release]

Or, there’s this,

This counter intuitive effect is very interesting for high precision measurements, which are very often based on the principle of quantum interference. “When the quantum system has a property you want to measure and another property which makes the system prone to perturbations, the two can be separated using a Quantum Cheshire Cat, and possibly the perturbation can be minimized”, says Stephan Sponar. [from the Vienna University of Technology news release]

The contrast is certainly interesting.

Transition metal dichalcogenides (molybdenum disulfide and tungsten diselenide) rock the graphene boat

Anyone who’s read stories about scientific discovery knows that the early stages are characterized by a number of possibilities so the current race to unseat graphene as the wonder material of the nanoworld is a ‘business as usual’ sign although I imagine it can be confusing for investors and others hoping to make their fortunes. As for the contenders to the ‘wonder nanomaterial throne’, they are transition metal dichalcogenides: molybdenum disulfide and tungsten diselenide both of which have garnered some recent attention.

A March 12, 2014 news item on Nanwerk features research on molybdenum disulfide from Poland,

Will one-atom-thick layers of molybdenum disulfide, a compound that occurs naturally in rocks, prove to be better than graphene for electronic applications? There are many signs that might prove to be the case. But physicists from the Faculty of Physics at the University of Warsaw have shown that the nature of the phenomena occurring in layered materials are still ill-understood and require further research.


Researchers at the University of Warsaw, Faculty of Physics (FUW) have shown that the phenomena occurring in the crystal network of molybdenum disulfide sheets are of a slightly different nature than previously thought. A report describing the discovery, achieved in collaboration with Laboratoire National des Champs Magnétiques Intenses in Grenoble, has recently been published in Applied Physics Letters.

“It will not become possible to construct complex electronic systems consisting of individual atomic sheets until we have a sufficiently good understanding of the physics involved in the phenomena occurring within the crystal network of those materials. Our research shows, however, that research still has a long way to go in this field”, says Prof. Adam Babinski at the UW Faculty of Physics.

A March 12, 2014 Dept. of Physics University of Warsaw (FUW) news release, which originated the news item, describes the researchers’ ideas about graphene and alternative materials such as molybdenum disulfide,

“It will not become possible to construct complex electronic systems consisting of individual atomic sheets until we have a sufficiently good understanding of the physics involved in the phenomena occurring within the crystal network of those materials. Our research shows, however, that research still has a long way to go in this field”, says Prof. Adam Babiński at the UW Faculty of Physics.

The simplest method of creating graphene is called exfoliation: a piece of scotch tape is first stuck to a piece of graphite, then peeled off. Among the particles that remain stuck to the tape, one can find microscopic layers of graphene. This is because graphite consists of many graphene sheets adjacent to one another. The carbon atoms within each layer are very strongly bound to one another (by covalent bonds, to which graphene owes its legendary resilience), but the individual layers are held together by significantly weaker bonds (van de Walls [van der Waals] bonds). Ordinary scotch tape is strong enough to break the latter and to tear individual graphene sheets away from the graphite crystal.

A few years ago it was noticed that just as graphene can be obtained from graphite, sheets a single atom thick can similarly be obtained from many other crystals. This has been successfully done, for instance, with transition metals chalcogenides (sulfides, selenides, and tellurides). Layers of molybdenum disulfide (MoS2), in particular, have proven to be a very interesting material. This compound exists in nature as molybdenite, a crystal material found in rocks around the world, frequently taking the characteristic form of silver-colored hexagonal plates. For years molybdenite has been used in the manufacturing of lubricants and metal alloys. Like in the case of graphite, the properties of single-atom sheets of MoS2 long went unnoticed.

From the standpoint of applications in electronics, molybdenum disulfide sheets exhibit a significant advantage over graphene: they have an energy gap, an energy range within which no electron states can exist. By applying electric field, the material can be switched between a state that conducts electricity and one that behaves like an insulator. By current calculations, a switched-off molybdenum disulfide transistor would consume even as little as several hundred thousand times less energy than a silicon transistor. Graphene, on the other hand, has no energy gap and transistors made of graphene cannot be fully switched off.

The news release goes on to describe how the researchers refined their understanding of molybdenum disulfide and its properties,

Valuable information about a crystal’s structure and phenomena occurring within it can be obtained by analyzing how light gets scattered within the material. Photons of a given energy are usually absorbed by the atoms and molecules of the material, then reemitted at the same energy. In the spectrum of the scattered light one can then see a distinctive peak, corresponding to that energy. It turns out, however, that one out of many millions of photons is able to use some of its energy otherwise, for instance to alter the vibration or circulation of a molecule. The reverse situation also sometimes occurs: a photon may take away some of the energy of a molecule, and so its own energy slightly increases. In this situation, known as Raman scattering, two smaller peaks are observed to either side of the main peak.

The scientists at the UW Faculty of Physics analyzed the Raman spectra of molybdenum disulfide carrying on low-temperature microscopic measurements. The higher sensitivity of the equipment and detailed analysis methods enabled the team to propose a more precise model of the phenomena occurring in the crystal network of molybdenum disulfide.

“In the case of single-layer materials, the shape of the Raman lines has previously been explained in terms of phenomena involving certain characteristic vibrations of the crystal network. We have shown for molybdenum disulfide sheets that the effects ascribed to those vibrations must actually, at least in part, be due to other network vibrations not previously taken into account”, explains Katarzyna Gołasa, a doctorate student at the UW Faculty of Physics.

The presence of the new type of vibration in single-sheet materials has an impact on how electrons behave. As a consequence, these materials must have somewhat different electronic properties than previously anticipated.

Here’s what the rocks look like,

Molybdenum disulfide occurs in nature as molybdenite, crystalline material that frequently takes the characteristic form of silver-colored hexagonal plates. (Source: FUW)

Molybdenum disulfide occurs in nature as molybdenite, crystalline material that frequently takes the characteristic form of silver-colored hexagonal plates. (Source: FUW)

I am not able to find the published research at this time (March 13, 2014).

The tungsten diselenide story is specifically application-centric. Dexter Johnson in a March 11, 2014 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) describes the differing perspectives and potential applications suggested by the three teams that cooperated to produce papers united by a joint theme ,

The three research groups focused on optoelectronics applications of tungsten diselenide, but each with a slightly different emphasis.

The University of Washington scientists highlighted applications of the material for a light emitting diode (LED). The Vienna University of Technology group focused on the material’s photovoltaic applications. And, finally, the MIT [Massachusetts Institute of Technology] group looked at all of the optoelectronic applications for the material that would result from the way it can be switched from being a p-type to a n-type semiconductor.

Here are some details of the research from each of the institutions’ news releases.

A March 10, 2014 University of Washington (state) news release highlights their LED work,

University of Washington [UW] scientists have built the thinnest-known LED that can be used as a source of light energy in electronics. The LED is based off of two-dimensional, flexible semiconductors, making it possible to stack or use in much smaller and more diverse applications than current technology allows.

“We are able to make the thinnest-possible LEDs, only three atoms thick yet mechanically strong. Such thin and foldable LEDs are critical for future portable and integrated electronic devices,” said Xiaodong Xu, a UW assistant professor in materials science and engineering and in physics.

The UW’s LED is made from flat sheets of the molecular semiconductor known as tungsten diselenide, a member of a group of two-dimensional materials that have been recently identified as the thinnest-known semiconductors. Researchers use regular adhesive tape to extract a single sheet of this material from thick, layered pieces in a method inspired by the 2010 Nobel Prize in Physics awarded to the University of Manchester for isolating one-atom-thick flakes of carbon, called graphene, from a piece of graphite.

In addition to light-emitting applications, this technology could open doors for using light as interconnects to run nano-scale computer chips instead of standard devices that operate off the movement of electrons, or electricity. The latter process creates a lot of heat and wastes power, whereas sending light through a chip to achieve the same purpose would be highly efficient.

“A promising solution is to replace the electrical interconnect with optical ones, which will maintain the high bandwidth but consume less energy,” Xu said. “Our work makes it possible to make highly integrated and energy-efficient devices in areas such as lighting, optical communication and nano lasers.”

Here’s a link to and a citation for this team’s paper,

Electrically tunable excitonic light-emitting diodes based on monolayer WSe2 p–n junctions by Jason S. Ross, Philip Klement, Aaron M. Jones, Nirmal J. Ghimire, Jiaqiang Yan, D. G. Mandrus, Takashi Taniguchi, Kenji Watanabe, Kenji Kitamura, Wang Yao, David H. Cobden, & Xiaodong Xu. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.26 Published online 09 March 2014

This paper is behind a paywall.

A March 9, 2014 University of Vienna news release highlights their work on tungsten diselinide and its possible application in solar cells,

… With graphene as a light detector, optical signals can be transformed into electric pulses on extremely short timescales.

For one very similar application, however, graphene is not well suited for building solar cells. “The electronic states in graphene are not very practical for creating photovoltaics”, says Thomas Mueller. Therefore, he and his team started to look for other materials, which, similarly to graphene, can arranged in ultrathin layers, but have even better electronic properties.

The material of choice was tungsten diselenide: It consists of one layer of tungsten atoms, which are connected by selenium atoms above and below the tungsten plane. The material absorbs light, much like graphene, but in tungsten diselenide, this light can be used to create electrical power.

The layer is so thin that 95% of the light just passes through – but a tenth of the remaining five percent, which are absorbed by the material, are converted into electrical power. Therefore, the internal efficiency is quite high. A larger portion of the incident light can be used if several of the ultrathin layers are stacked on top of each other – but sometimes the high transparency can be a useful side effect. “We are envisioning solar cell layers on glass facades, which let part of the light into the building while at the same time creating electricity”, says Thomas Mueller.

Today, standard solar cells are mostly made of silicon, they are rather bulky and inflexible. Organic materials are also used for opto-electronic applications, but they age rather quickly. “A big advantage of two-dimensional structures of single atomic layers is their crystallinity. Crystal structures lend stability”, says Thomas Mueller.

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

Solar-energy conversion and light emission in an atomic monolayer p–n diode by Andreas Pospischil, Marco M. Furchi, & Thomas Mueller. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.14 Published online 09 March 2014

This paper is behind a paywll.

Finally, a March 10, 2014 MIT news release details their work about material able to switch from p-type (p = positive) to a n-type (n = negative) semiconductors,

The material they used, called tungsten diselenide (WSe2), is part of a class of single-molecule-thick materials under investigation for possible use in new optoelectronic devices — ones that can manipulate the interactions of light and electricity. In these experiments, the MIT researchers were able to use the material to produce diodes, the basic building block of modern electronics.

Typically, diodes (which allow electrons to flow in only one direction) are made by “doping,” which is a process of injecting other atoms into the crystal structure of a host material. By using different materials for this irreversible process, it is possible to make either of the two basic kinds of semiconducting materials, p-type or n-type.

But with the new material, either p-type or n-type functions can be obtained just by bringing the vanishingly thin film into very close proximity with an adjacent metal electrode, and tuning the voltage in this electrode from positive to negative. That means the material can easily and instantly be switched from one type to the other, which is rarely the case with conventional semiconductors.

In their experiments, the MIT team produced a device with a sheet of WSe2 material that was electrically doped half n-type and half p-type, creating a working diode that has properties “very close to the ideal,” Jarillo-Herrero says.

By making diodes, it is possible to produce all three basic optoelectronic devices — photodetectors, photovoltaic cells, and LEDs; the MIT team has demonstrated all three, Jarillo-Herrero says. While these are proof-of-concept devices, and not designed for scaling up, the successful demonstration could point the way toward a wide range of potential uses, he says.

“It’s known how to make very large-area materials” of this type, Churchill says. While further work will be required, he says, “there’s no reason you wouldn’t be able to do it on an industrial scale.”

In principle, Jarillo-Herrero says, because this material can be engineered to produce different values of a key property called bandgap, it should be possible to make LEDs that produce any color — something that is difficult to do with conventional materials. And because the material is so thin, transparent, and lightweight, devices such as solar cells or displays could potentially be built into building or vehicle windows, or even incorporated into clothing, he says.

While selenium is not as abundant as silicon or other promising materials for electronics, the thinness of these sheets is a big advantage, Churchill points out: “It’s thousands or tens of thousands of times thinner” than conventional diode materials, “so you’d use thousands of times less material” to make devices of a given size.

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

Optoelectronic devices based on electrically tunable p–n diodes in a monolayer dichalcogenide by Britton W. H. Baugher, Hugh O. H. Churchill, Yafang Yang, & Pablo Jarillo-Herrero. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.25 Published online 09 March 2014

This paper is behind a paywall.

These are very exciting, if not to say, electrifying times. (Couldn’t resist the wordplay.)

2-photon lithography yields precise 3D printing

Engineers had best watch out because the chemists are coming. According to a March 12, 2012 news item on Nanowerk, a multidisciplinary team at the Vienna University of Technology (TU Vienna) has devised a technology for creating extremely detailed and precise 3D nanoscale objects,

Printing three dimensional objects with incredibly fine details is now possible using “two-photon lithography”. With this technology, tiny structures on a nanometer scale can be fabricated. …

The 3D printer uses a liquid resin, which is hardened at precisely the correct spots by a focused laser beam. The focal point of the laser beam is guided through the resin by movable mirrors and leaves behind a hardened line of solid polymer, just a few hundred nanometers wide. This fine resolution enables the creation of intricately structured sculptures as tiny as a grain of sand. “Until now, this technique used to be quite slow”, says Professor Jürgen Stampfl from the Institute of Materials Science and Technology at the TU Vienna. “The printing speed used to be measured in millimeters per second – our device can do five meters in one second.” In two-photon lithography, this is a world record.

3D-printing is not all about mechanics – chemists had a crucial role to play in this project too. “The resin contains molecules, which are activated by the laser light. They induce a chain reaction in other components of the resin, so-called monomers, and turn them into a solid”, says Jan Torgersen. These initiator molecules are only activated if they absorb two photons of the laser beam at once – and this only happens in the very center of the laser beam, where the intensity is highest. In contrast to conventional 3D-printing techniques, solid material can be created anywhere within the liquid resin rather than on top of the previously created layer only. Therefore, the working surface does not have to be specially prepared before the next layer can be produced … , which saves a lot of time. A team of chemists led by Professor Robert Liska (TU Vienna) developed the suitable ingredients for this special resin.

The March 12, 2012 press release includes accompanying images and video from Vienna Technical University. I have embedded the video in this posting largely because it provides a contrast to some of the more processed and visually enhanced materials that one usually finds,

As the researchers note, this is extraordinary detail.

Quantum entanglement and magnetism

A joint Indian/Austrian research team has uncovered the secrets behind why manganese oxides (manganites) have demonstrably different properties when size is reduced. From the Nov. 29, 2011 news item on Nanowerk,

Material properties such as electrical conductivity, magnetic properties or the melting point do not depend on an object’s size and shape. “In India, however, an experiment recently showed that special manganese oxides – so called manganites – exhibit completely different properties, when their size is reduced to tiny grains”, Karsten Held explains.

A team of scientists from the Vienna University of Technology (Austria) and the University of Calcutta (India) investigated this phenomenon – and the new effect could be explained in computer simulations. In a crossover from large crystals to smaller crystals, the distribution of the electrons changes, and so does their energy. This, in turn, changes the electrical and magnetic properties of the crystal. “The phenomenon of quantum entanglement plays a very important role here”, says Professor Karsten Held. “We cannot think of the electrons as classical particles, moving independently of each other, on well-separated paths. The electrons can only be described collectively.” By changing their size, the properties of the manganite-crystals can now be harnessed. Larger crystals are insulators, and they are not magnetic. Tiny crystal pieces on the other hand turn out to be metallic ferromagnets.

Here’s an image of a magnet and crystals,

A magnet and an illustration of manganite cystals (downloaded from the Vienna University of Technology wesite)

Here’s a link to the Nov. 29, 2011 news release from the Vienna University of Technology where you can find additional information in English and German and some pictures.