In search of the lighting material of the future

At the Paul Scherrer Institute PSI, researchers have gained insights into a promising material for organic light-emitting diodes (OLEDs). The substance enables high light yields and would be inexpensive to produce on a large scale – that means it is practically made for use in large-area room lighting. Researchers have been searching for such materials for a long time. The newly generated understanding will facilitate the rapid and cost-efficient development of new lighting appliances in the future. The study appears today in the journal Nature Communications.

The compound is a yellowish solid. If you dissolve it in a liquid or place a thin layer of it on an electrode and then apply an electric current, it gives off an intense green glow. The reason: The molecules absorb the energy supplied to them and gradually emit it again in the form of light. This process is called electroluminescence. Light-emitting diodes are based on this principle.

Read more on the Swiss FEL and Swiss Light Source website

Image: Grigory Smolentsev in front of SwissFEL

Credit: Paul Scherrer Institute/Mahir Dzambegovic

Toward better motors with X-ray light

Making Switzerland’s road traffic fit for the future calls for research, first and foremost. In the large-scale research facilities of PSI, chemists and engineers are investigating how to improve the efficiency of motors and reduce their emissions.

“The overall transportation system of Switzerland in 2040 is efficient in all aspects.” The primary strategic goal of the Federal Department of the Environment, Transport, Energy and Communications (DETEC) sounds good. The subordinate Swiss Federal Office of Energy (SFOE) specifies that vehicular traffic should pollute the environment less and become more energy-efficient and climate-friendly. Switzerland has set an ambitious goal for itself: to be climate-neutral by 2050.
This is a major challenge. According to the most recent “microcensus” on mobility from 2015, every person living in Switzerland travels around 24,850 kilometres per year. A high number, which also includes trips abroad. In everyday life and within Switzerland, the average per person is nearly 37 kilometres per day – and rising.
According to the Federal Office for the Environment (FOEN), cars, trucks, and buses produce three-fourths of the greenhouse gas emissions in the transportation sector. From this it follows: Whether or not the nation achieves its goal depends heavily on the motors used in these modes of transportation. Their CO2 emissions must be radically reduced. This is precisely the starting point for researchers at PSI and other institutions.

> Read more on the Swiss Light Source (PSI) website

Image: Passenger cars powered by hydrogen fuel cells have a greater range than electric cars, but they are less efficient. PSI researchers want to change that.
Credit: Adobe Stock/Graphic: Stefan Schulze-Henrichs

Soft X-ray Laminography: 3D imaging with powerful contrast mechanisms

Soft X-ray 3D imaging has already been realized at synchrotron radiation sources using either scanning transmission X-ray microscopy (STXM) schemes or tomography-based concepts. However, the maximum accessible sample volume is severely limited by the reduced penetration depth of the lower-energy soft X-ray radiation. This becomes even more of a drawback in the case of flat and extended specimens, which can be found in various fields of nanoscience.

The generalized geometry of laminography, characterized by a tilted axis of rotation concerning the incident X-ray beam resulting in a constant material thickness during rotation, has proven to be particularly suitable for the investigation of laterally extended and thin objects. The combination of soft X-rays and laminography provides the unique potential of bridging the gap between investigations of elaborate nanostructured thin film samples and taking advantage of the characteristic absorption contrast mechanisms in the soft X-ray range.

>Read more on the Swiss Light Source at PSI website

Image: 3D model constructed from soft X-ray laminography measurements of the front tip of the wing scale from a European peacock butterfly.

More magnets, smoother curves: the Swiss Light Source upgrade

The Swiss Light Source SLS is set to undergo an upgrade in the coming years: SLS 2.0.

The renovation is made possible by the latest technologies and will create a large-scale research facility that will meet the needs of researchers for decades to come.

Since 2001, “the UFO” has been providing reliable and excellent service: In the circular building of the Swiss Light Source SLS, researchers from PSI and all over the world carry out cutting-edge research. For example, they can investigate the electronic properties of novel materials, determine the structure of medically relevant proteins, and make visible the nanostructure of a human bone.
“Internationally, the SLS has been setting standards for nearly two decades”, says Terence Garvey, SLS 2.0 accelerator project head. Now, Garvey continues, it’s time for a modernisation. In the coming years, SLS is expected to undergo an upgrade with the project title SLS 2.0. SLS will remain within the same UFO-shaped building, but will get changes in crucial areas inside. Garvey is one of the two project leaders for the upgrade, together with Philip Willmott.

Swiss Light Source (SLS) , , ,

A fast and precise look into fibre-reinforced composites

Researchers at the Paul Scherrer Institute PSI have improved a method for small angle X-ray scattering (SAXS) to such an extent that it can now be used in the development or quality control of novel fibre-reinforced composites.

This means that in the future, such materials can be investigated not only with X-rays from especially powerful sources such as the Swiss Light Source SLS, but also with those from conventional X-ray tubes. The researchers have published their results in the journal Nature Communications.
Novel fibre-reinforced composites are becoming increasingly important as stable and lightweight materials. One example of this type of composite is carbon fibre reinforced polymers (CFRP), which are used in aircraft construction or in the construction of Formula 1 racing cars and sports bicycles. The properties of these materials depend to a large extent on how the tiny fibres are aligned and how they are arranged and embedded in the surrounding material, influencing the mechanical, optical, or electromagnetic behaviour of the composites.

To investigate the fibre’s orientation in such composites, researchers must look inside them. One could use small angle X-ray scattering (SAXS), exploiting the fact that X-rays are scattered when they penetrate matter. The resulting scattering pattern can then be used to obtain information about the interior of a sample and potentially the orientation of the fibres. However, the common SAXS methods have the disadvantage of being quite slow: It can take up to several hours to scan centimetre-sized specimens with the required resolution.

>Read more on the Swiss Light Source (PSI) website

Image: Matias Kagias (left) and Marco Stampanoni in front of the apparatus with which they examined the composites using the newly developed X-ray method. Both hold one of the workpieces that have been X-rayed.
Credit: Paul Scherrer Institute/Mahir Dzambegovic

Operando X-ray diffraction during laser 3D printing

Additive manufacturing, a bottom-up approach for manufacturing components layer by layer from a 3D computer model, plays a key role in the so-called “fourth” industrial revolution. Selective laser melting (SLM), one of the more mature additive manufacturing processes, uses a high power-density laser to selectively melt and fuse powders spread layer by layer. The method enables to build near full density functional parts and has viable economic benefits. Despite significant progress in recent years, the relationship between the many processing parameters and final microstructure is not well understood, which strongly limits the number of alloys that can be produced by SLM for commercial applications.

>Read more on the Swiss Light Source (PSI) website

Image: Rendered 3D model of the MiniSLM device.

Preventing tumour metastasis

Researchers at the Paul Scherrer Institute, together with colleagues from the pharmaceutical company F. Hoffmann-La Roche AG, have taken an important step towards the development of an agent against the metastasis of certain cancers.

Using the Swiss Light Source, they deciphered the structure of a receptor that plays a crucial role in the migration of cancer cells. This makes it possible to identify agents that could prevent the spread of certain cancer cells via the body’s lymphatic system. The researchers have now published their results in the journal Cell.
When cancer cells spread in the body, secondary tumours, called metastases, can develop. These are responsible for around 90 percent of deaths in cancer patients. An important pathway for spreading the cancer cells is through the lymphatic system, which, like the system of blood vessels, runs through the entire body and connects lymph nodes to each other. In the migration of white blood cells through this system, for example to coordinate the defense against pathogens, one special membrane protein, the chemokine receptor 7 (CCR7) plays an important role. It sits in the shell of the cells, the cell membrane, in such a way that it can receive external signals and relay them to the interior. Within the framework of a joint project with the pharmaceutical company F. Hoffmann-La Roche AG (Roche), researchers at the Paul Scherrer Institute (PSI) have for the first time been able to decipher the structure of CCR7 and lay the foundation for the development of a drug that could prevent metastasis in certain prevalent cancer types, such as colorectal cancer.

Read more on the SLS at PSI website

Image: Steffen Brünle (right) and Jörg Standfuss at the apparatus they use to separate proteins from each other. For their study, the researchers modified insect cells to produce a human protein. To extract this from the cell, the cell was destroyed, and then the protein, whose structure the researchers have now elucidated, was separated with the help of this apparatus.
Credit: Paul Scherrer Institute/Markus Fischer

World record in tomography: watching how metal foam forms

An international research team at the Swiss Light Source (SLS) has set a new tomography world record using a rotary sample table developed at the HZB.

With 208 three-dimensional tomographic X-ray images per second, they were able to document the dynamic processes involved in the foaming of liquid aluminium. The method is presented in the journal Nature Communications.
The precision rotary sample table designed at the HZB rotates around its axis at several hundred revolutions per second with extreme precision. The HZB team headed Dr. Francisco García-Moreno combined the rotary sample table with high-resolution optics and achieved a world record of over 25 tomographic images per second using the BESSY II EDDI beamline in 2018.

>Read more on the Bessy II at HZB wesbite

Image: The precision rotary sample table designed at the HZB turns around its axis at several hundred revolutions per second with extreme precision.
Credit: © HZB

Weyl fermions discovered in another class of materials

A particular kind of quasi-particle states, the Weyl fermions, were first discovered a few years ago in certain solids. Their specialty: They move through a material in a well ordered manner that practically never lets them collide with each other and is thus very energy efficient. This implies intriguing possibilities for the electronics of the future. Up to now, Weyl fermions had only been found in certain non-magnetic materials. Now however, for the very first time, scientists at the Paul Scherrer Institute PSI have experimentally proven their existence in another type of material: a paramagnet with intrinsic slow magnetic fluctuations. This finding also shows that it is possible to manipulate the Weyl fermions with small magnetic fields. It thus opens further possibilities to use them in spintronics, a promising development in electronics for novel computer technology. The researchers have published their findings in the scientific journal Science Advances.

Amongst the approaches that could pave the way to energy efficient electronics of the future, Weyl fermions could play a role. Found experimentally only inside materials as so-called quasi-particles, they behave like particles which have no mass. Predicted theoretically already in 1929 by the mathematician Hermann Weyl, their experimental discovery by scientists amongst other at PSI only came in 2015. So far, Weyl fermions had only been observed in certain non-magnetic materials. Now however, a team of scientists at PSI together with researchers in the USA, China, Germany and Austria also found them in a specific paramagnetic material. This discovery could bring a potential usage of Weyl fermions in future computer technology one step closer.

>Read more on the Swiss Light Source at PSI website

Image: The three PSI researchers Junzhang Ma, Ming Shi and Jasmin Jandke (from left to right) at the Swiss Light Source SLS, where they succeeded in proving the existence of Weyl fermions in paramagnetic material.
Credit: Paul Scherrer Institute/Markus Fischer

New material with magnetic shape memory

Researchers at the Paul Scherrer Institute PSI and ETH Zurich have developed a new material whose shape memory is activated by magnetism.

It retains a given shape when it is put into a magnetic field. It is a composite material consisting of two components. What is special about the new material is that, unlike previous shape-memory materials, it consists of a polymer and droplets of a so-called magnetorheological fluid embedded in it. Areas of application for this new type of composite material include medicine, aerospace, electronics and robotics. The researchers are now publishing their results in the scientific journal Advanced Materials.
It looks like a magic trick: A magnet moves away from a black, twisted band and the band relaxes –without any further effect (see video). What looks like magic can be explained by magnetism. The black ribbon consists of a composite of two components: a silicone-based polymer and small droplets of water and glycerine in which tiny particles of carbonyl iron float. The latter provide the magnetic properties of the material and its shape memory. If the composite material is forced into a certain shape with tweezers and then exposed to a magnetic field, this shape is retained even when the tweezers are removed. Only when the magnetic field is also removed does the material return to its original shape.

>Read more on the Swiss Light Source website

Image: Paolo Testa, first author of the study, with a model of the overall structure of the shape-memory material
Credit: Paul Scherrer Institute/Mahir Dzambegovic

New material also reveals new quasiparticles

Researchers at PSI have investigated a novel crystalline material that exhibits electronic properties that have never been seen before.

It is a crystal of aluminum and platinum atoms arranged in a special way. In the symmetrically repeating unit cells of this crystal, individual atoms were offset from each other in such a way that they – as connected in the mind’s eye – followed the shape of a spiral staircase. This resulted in novel properties of electronic behaviour for the crystal as a whole, including so-called Rarita-Schwinger fermions in its interior and very long and quadruple topological Fermi arcs on its surface. The researchers have now published their results in the journal Nature Physics.

Researchers at the Paul Scherrer Institute PSI have found a new kind of quasiparticle. Quasiparticles are states in material that behave in a certain way like actual elementary particles. The two physicists William Rarita and Julian Schwinger had predicted this type of quasiparticles in 1941, which came to be known as Rarita-Schwinger fermions. Exactly these have now been detected experimentally for the first time – thanks in part to measurements at the Swiss Synchrotron Light Source SLS at PSI. “As far as we know, we are – simultaneously with three other research groups – among the first to see Rarita-Schwinger fermions”, says Niels Schröter, a researcher at PSI and first author of the new study.

>Read more on the Swiss Light Source at PSI website.

Image: Niels Schröter (left) and Vladimir Strocov at their experimental station in the Swiss Light Source SLS at PSI.
Credit: Paul Scherrer Institute/Mahir Dzambegovic

A compass pointing West

Researchers at the Paul Scherrer Institute PSI and ETH Zurich have discovered a special phenomenon of magnetism in the nano range.

It enables magnets to be assembled in unusual configurations. This could be used to build computer memories and switches to increase the performance of microprocessors. The results of the work have now been published in the journal Science.
Magnets are characterized by the fact that they have a North pole and a South pole. If two common magnets are held close to each other, opposite poles attract and like poles repel each other. This is why magnetic needles, such as those found in a compass, align themselves in the Earth’s magnetic field so that we can use them to determine the cardinal directions North and South and, derived from this, East and West. In the world that we experience every day with our senses, this rule is correct. However, if you leave the macroscopic world and dive into depths of much smaller dimensions, this changes. Researchers at the Paul Scherrer Institute PSI and the ETH Zurich have now discovered a very special magnetic interaction at the level of nanoscopic structures made of magnetic layers only a few atoms thick.

>Read more on the Swiss Light Source at PSI website

Image: Zhaochu Luo, lead author of the study, in front of a so-called sputter deposition tool. In the apparatus the layers of platinum, cobalt and aluminium oxide are produced. Each layer is only a few nanometers thick. Credit: Paul Scherrer Institute/Mahir Dzambegovic

Virtual lens improves X-ray microscopy

PSI researchers are first to transfer state-of-the-art microscopy method to X-ray imaging

X-rays provide unique insights into the interior of materials, tissues, and cells. Researchers at the Paul Scherrer Institute PSI have developed a new method that makes X-ray images even better: The resolution is higher and allows more precise inferences about the properties of materials. To accomplish this, the researchers moved the lens of an X-ray microscope and recorded a number of individual images to generate, with the help of computer algorithms, the actual picture. In doing so they have, for the first time ever, transferred the principle of so-called Fourier ptychography to X-ray measurements. The results of their work, carried out at the Swiss Light Source SLS, are published in the journal Science Advances.

>Read more on the Swiss Light Source at PSI website

Image: Klaus Wakonig and Ana Diaz, together with other PSI researchers, have transferred the principle of Fourier ptychography to X-ray microscopy for the first time ever.
Credit: Paul Scherrer Institute/Markus Fischer

Industrial collaboration

Fabia Gozzo made a beamline at the Swiss Light Source SLS of the Paul Scherrer Institute PSI into one of the world’s leading facilities and today she is making her knowledge available to industry with her spin-off.

In spring 2012 Fabia Gozzo faced an important decision: security or risk? After 12 years, she had resigned from her job at the Paul Scherrer Institute to move to Brussels with her family. Her husband had taken a post as vice president of a company. The two had previously agreed to emigrate if one of them got such a one-of-a-kind offer.

Fabia Gozzo was looking for a job too. Soon she had an offer for a position as laboratory head at a Brussels-based institute for nano- and microelectronics. The position would have been a comparable to the one she had held up to that point at PSI. Then I asked myself: For that, do I want to burden myself with the trouble of this big relocation?, Gozzo says today. She found the answer was no. And instead, she founded her own firm: Excelsus Structural Solutions.

She had long had the idea of offering her experience in the analysis of material structures, which she had gained at the Swiss Light Source SLS, to the pharmaceutical industry. With the synchrotron light, the smallest devation from the desired solid structure in drugs can be detected – so their effectiveness can be improved. Gozzo and PSI signed an agreement for regular commercial use of a beamline at SLS. Now all Gozzo needed was customers. She gave herself two years to see if it would all work out.

>Read more on the Swiss Light Source at PSI website

Image: Fabia Gozzo is CEO and founder of Excelsus Structural Solutions. 
Credit: Scanderbeg Sauer Photography

A day as a young scientist

Physics isn’t everyone’s favourite subject. At the iLab of the Paul Scherrer Institute PSI, students experience the material in a different way: with experiments instead of memorising formulas.

Beat Henrich likes to use the Big Bang to explain the benefits of spectrometry to his adolescent guests. We know that everything in our universe is constantly moving apart, he says to the 17 students at the experiment station of the school laboratory iLab, only because we can measure the light of other galaxies. But because not all processes in the universe can be explained by matter that generates or reflects light, Henrich continues, scientists are currently investigating the “dark matter”, the big mystery in the history of the universe’s origins. If you make a discovery there, the head of iLab concludes, you would be candidates for the Nobel Prize.Is there a future Nobel laureate sitting here? Or a future top researcher? Michael Portmann, a physics teacher at the cantonal high school Alpenquai in Lucerne, casts a glance at the students of his two classes with whom he travelled to PSI today. Naturally, it’s too soon to tell, says Portmann, who has taught physics for 15 years and knows of a just handful of his former students who went on to study his subject later. But here it does show who is open to research.

Image: The school laboratory iLab gives young people an insight into the world of research.
Credit: Paul Scherrer Institute/Markus Fischer

Cleaner diesel emissions

More effective control of diesel nitrogen oxides through dosed addition of ammonia

In diesel engines, the burning of the fuel releases nitrogen oxides (NOx), which are harmful to human health. The automobile industry therefore developed a technique that reduces these emissions: Gaseous ammonia is added to the exhaust and, prompted by a catalyst, reacts with the nitrogen oxides to produce harmless nitrogen and water. At low temperatures, however, this process does not yet work optimally. Now, for the first time, scientists at the Paul Scherrer Institute PSI have found a remedy which is based on observations at the molecular level: The precise amount of added ammonia needs to be varied depending on the temperature. With this knowledge, manufacturers can improve the effectiveness of their catalytic converters for diesel vehicles. The researchers have now published their findings in the journal Nature Catalysis.

>Read more on the Paul Scherrer Institute website

Image: At the X-ray beam line: Davide Ferri (left) and Maarten Nachtegaal at the SLS experimental station where they studied diesel catalysis.
Photo: Paul Scherrer Institute/Markus Fischer