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News Article | May 12, 2017
Site: phys.org

Presenting at a conference in Norway, Rozynek, a researcher at Adam Mickiewicz University in Pozna?, Poland, demonstrated something that looked almost like magic. When he poked a needle-shaped electrode into a mixture of micron-sized, spherical metal particles dispersed in silicone oil, a sphere stuck to its end. As Rozynek pulled the electrode out of the dispersion, another sphere attached to the first sphere, and then another to the second sphere, and so on, until a long chain formed. "The spheres behaved like magnetic beads, except no magnetism was involved," said Luijten, professor of materials science and engineering and of engineering and applied mathematics at Northwestern's McCormick School of Engineering. "The particles have no tendency to cluster. I realized that something more complicated was happening." Rozynek, along with his collaborators Filip Dutka, Piotr Garstecki, and Arkadiusz Józefczak, and Luijten joined their teams to understand the phenomenon that caused these chains to form. Their resulting discovery could lead to a new generation of electronic devices and a fast, simple method to write two-dimensional electronic circuits. "Our scientific results could open up other areas for future research—both fundamental and applied," Rozynek said. "We are already working on follow-up projects based on our discovery." Supported by the Foundation for Polish Science, Polish National Science Centre, and the US National Science Foundation, the research was published online today in the journal Nature Communications. Rozynek and Luijten are co-corresponding authors. Rozynek is also co-first author with Ming Han, a PhD student in Luijten's Computational Soft Matter Lab. Rozynek and Han performed multiple calculations, showing how the electrode's electric field changed the particles' properties. When the electrode is dipped into the colloidal solution, its charged tip polarizes each sphere. These induced dipolar interactions cause the spheres to link together. A resulting chain could contain hundreds of thousands of spheres, reaching up to 30 centimeters in length. After the team solved the mystery of how the chains formed, it had a second mystery to tackle. "Another fascinating part is that once we pulled the chain out of the liquid, we no longer had to apply an electric field to hold the chain's structure," Han said. "After the field was turned off, the stable particle chain remained stable." Following months of investigation, Luijten and Rozynek's teams discovered that the chains maintained their structures due to liquid "bridges" between adjacent particles. As researchers pulled the chain out of the liquid, silicone oil clung to the sides of each particle, forming a case around the entire chain and keeping it intact. "Surface tension plays a big role here," Han said. "The liquid bridge made the particles stick together. The physics here is really interesting. Most people would think that if you wanted to hold the structure, then you would need to apply the electric field. But that is not needed in our system." Once the flexible chain is pulled out of the liquid, it can be immediately dragged along a surface and deposited to create a pattern. The researchers believe this method could be used as an alternative way to create simple, two-dimensional electronic circuits. If molten wax is used instead of silicone oil, then the method could also be used to build three-dimensional structures that hold their shapes when the wax cools and hardens. "Though simple, our method for fabricating colloidal structures is very elegant and can be used for many applications," Rozynek said, "including fabrication of conductive paths on different substrates to be used, for example, in electronic applications." Luijten and Rozynek believe that solving this mystery could potentially open the door for applications that they cannot predict today. By understanding how the method works, they can better assess how different types of fluids or voltage levels could affect the chains and change the outcome. "Understanding how it works makes it so much easier to manipulate and optimize," Luijten said. "We can say if the method will work better or worse if the particles are larger or if the electric field is stronger. That's only possible because we understand it. Otherwise, you would have to examine an endless set of combinations." More information: Zbigniew Rozynek et al, Formation of printable granular and colloidal chains through capillary effects and dielectrophoresis, Nature Communications (2017). DOI: 10.1038/ncomms15255


News Article | May 16, 2017
Site: www.cemag.us

IBM has announced that its researchers have identified a new way to trigger the body’s immune response by using polymer-coated graphene sheets. The research was recently published in Nature Communications. In the case of cancer treatment, to target specific tumors in the body, scientists have developed techniques where drug molecules are attached directly to the surface of a nanomaterial, such as graphene sheets. Combining the nanomaterial and the drug molecules, these “nanotherapies” could help clinicians treat tumors by transporting the drugs directly to the tumors, where they can be released onto the cancer cells to help fight the disease. Previously, researchers had determined that nanotherapies require the application of coating molecules, such as polyethylene glycol, to be biocompatible and avoid damaging surrounding cells as shown in a previous study published in Nature Nanotechnology by the same team at IBM Research. IBM’s new research indicates that the polymer-coated graphene sheets can have an inadvertent, previously unknown, secondary effect, which triggers the release of cytokine proteins. These proteins act as “signal flares of the body” and attract the body’s immune cells like helper T cells (which relay the signal forward) and killer T cells (which kill infected cells) to the location of the graphene sheets. Simulations on IBM’s Blue Gene super computer showed that the polymers attach the nanomaterials to cell surfaces, amplifying the initial signaling process. Research suggests these signals are broadcast within six hours of the nanodrugs being encountered. “We’ve essentially uncovered a new way for clinicians to trigger the body’s immune system to spring into action — which is not an easy task” says Dr. Ruhong Zhou, Manager, Soft Matter Science at IBM Research. “This discovery could represent an incredible development in precision medicine. If these nanomaterials were targeted at, say, tumors or virus-infected cells, one could, in principal, stimulate the immune system to attack cancer and infections at their source.” Clinicians might couple immunotherapies like nanotherapies with the delivery of traditional drugs, which are already compatible with graphene surfaces. Coupling both nano or traditional pharmaceuticals and the body’s own natural immune system response could form the basis for new ways for clinicians to fight human diseases.


News Article | April 26, 2017
Site: www.newscientist.com

Everyone poops, and it takes them about the same amount of time. A new study of the hydrodynamics of defecation finds that all mammals with faeces like ours take 12 seconds on average to relieve themselves, no matter how large or small the animal. The research, published in Soft Matter, reveals that the soft matter coming out of the hind ends of elephants, pandas, warthogs and dogs slides out of the rectum on a layer of mucus that keeps toilet time to a minimum. “The smell of body waste attracts predators, which is dangerous for animals. If they stay longer doing their thing, they’re exposing themselves and risking being discovered,” says Patricia Yang, a mechanical engineer at the Georgia Institute of Technology in Atlanta. Yang and colleagues filmed elephants, pandas and warthogs at a local zoo, and one team member’s dog in a park, as they defecated.  All these animals produce cylindrical faeces, like we do, and this is the most common kind among mammals. Though the animals’ body masses ranged from 4 to 4,000 kilograms, the duration of defecation remained constant. That consistency across animals is down to a few things. First, the length of faecal pieces was 5 times as long as the diameter of the rectum in each of the animals. Yang also found that the normal, low-level pressure animals apply to push through a bowel movement is constant, and unrelated to a creature’s body mass. This means that, whether it’s a human or a mouse, the pressure used on normal excrement is the same. This is similar to her previous finding that mammals take the same amount of time to empty their bladders. The final piece of this puzzle is the mucus layer in the colon, which plays a big role in the duration of evacuation. Creatures with cylindrical faeces aren’t squeezing matter through a nozzle like a toothpaste tube.  “It’s more like a plug that just goes through a chute,” she says. Yang says larger animals have more rectal mucus, which facilitates quicker expulsion. Constipation happens when that mucus is absorbed by the faeces. Without this slick layer, a human applying no pressure at all would take 500 days to void their bowels, Yang says. “It would be shortened to 6 hours if you apply maximum pressure, but I believe you’d still need to see a doctor,” she says. All animals produce on average two pieces of faeces. Larger animals have longer faeces and a longer rectum, but they have thicker mucus, which makes the faeces accelerate faster – so they travel a longer distance in the same amount of time. Yang’s team also used Youtube videos of animals relieving themselves to measure the average time of defecation among 23 different species. “There’s a surprising amount of poop videos online. They’re mostly from zoos where tourists film it and upload it,” she says. They collected stool samples from 34 species and found that diet affects the density of faecal matter. Floaters – droppings that are lighter than water – are produced by pandas and other herbivores like elephants and kangaroos. They eat low-nutrition, high-fiber foods and defecate much of it in undigested form. Sinkers are produced by large carnivores like bears, tigers and lions. They eat heavier, indigestible ingredients, including fur and bone. Using a rheometer – a device that measures the way fluids flow under applied force – Yang found that faeces are shear-thinning, which means they have lower resistance the faster they’re deformed. That’s why dog poop feels slippery when you step on it. Based on animals at the Atlanta Zoo, they found that on average, animals take in about 8 per cent of their body mass in food, and expel 1 per cent of body mass in faeces. Their observations fed into a mathematical model that can predict defecation times for various problems within the digestive system. “If it’s taking far longer than 12 seconds, I’d say you should go see someone about it,” she says. “But you can’t count the newspaper time.”


News Article | April 27, 2017
Site: phys.org

Sure, it's uncomfortable to talk about. But that's where science comes in, because what we don't like to discuss can still cause harm. Irritable bowel syndrome, inflammatory bowel disease, gastrointestinal infections and other poop-related ailments cost Americans billions of dollars annually. But trying to stem these problems was not our main motivation for trying to figure out some of the physics of defecation. It was something else, much more sinister. From personal observation, into the lab When parenthood hits, it hits hard. One of us is a working dad who survived by learning a new set of skills, one of which was fecal analysis. Years of diaper changes and then potty training turned me from a poo-analysis novice to a wizened connoisseur. My life passes by in a series of images: hard feces pellets like peas to long feces like a smooth snake to a puddle of brown water. Unlike the ancients, we didn't believe that we could predict the future from children's stool. But we did think it was worth trying to understand where all these shapes come from. Having a laboratory to answer questions about the everyday world is one of the distinct pleasures of being a scientist. As fluid dynamicists, we joined forces with colorectal surgeon Daniel Chu, and two stalwart undergraduates, Candice Kaminski and Morgan LaMarca, who filmed defecation and hand-picked feces from 34 mammalian species at Zoo Atlanta in order to measure their density and viscosity. We learned that most elephants and other herbivores create "floaters" while most tigers and other carnivores create "sinkers." Inadvertently, we also ranked feces from most to least smelly, starting with tiger and rhino and going all the way to panda. The zoo's variety of animals provided us with a range of fecal sizes and shapes that served as independent pieces of evidence to validate our mathematical model of the duration of defecation. We also placed the feces in a device called a "rheometer," a precision blender that can measure the properties of liquid-like and solid-like materials such as chocolate and shampoo. Our lab shares two rheometers with Georgia Tech physicist Alberto Fernandez-Nieves. We have since categorized the rheometers as the "clean rheometer" and the "David Hu rheometer" – which has seen its fair share of frog saliva, mucus and feces. The secret to the speed What else did we learn? Bigger animals have longer feces. And bigger animals also defecate at higher speed. For instance, an elephant defecates at a speed of six centimeters per second, nearly six times as fast as a dog. The speed of defecation for humans is in between: two centimeters per second. Together, this meant that defecation duration is constant across many animal species – around 12 seconds (plus or minus 7 seconds) – even though the volume varies greatly. Assuming a bell curve distribution, 66 percent of animals take between 5 and 19 seconds to defecate. It's a surprisingly small range, given that elephant feces have a volume of 20 liters, nearly a thousand times more than a dog's, at 10 milliliters. How can big animals defecate at such high speed? The answer, we found, was in the properties of an ultra-thin layer of mucus lining the walls of the large intestine. The mucus layer is as thin as human hair, so thin that we could measure it only by weighing feces as the mucus evaporated. Despite being thin, the mucus is very slippery, more than 100 times less viscous than feces. During defecation, feces moves like a solid plug. Therefore, in ideal conditions, the combined length and diameter of feces is simply determined by the shape of one's rectum and large intestine. One of the big findings of our study was that feces extend halfway up the length of the colon from the rectum. Putting the length of feces together with the properties of mucus, we now have a cohesive physics story for how defecation happens. Bigger animals have longer feces, but also thicker mucus, enabling them to achieve high speeds with the same pressure. Without this mucus layer, defecation might not be possible. Alterations in mucus can contribute to several ailments, including chronic constipation and even infections by bacteria such as C. difficile in the gastrointestinal tract. Beyond simply following our scientific curiosity, our measurements of feces have also had some practical applications. Our defecation data helped us design an adult diaper for astronauts. Astronauts want to stay in space suits for seven days, but are limited by their diapers. Taking advantage of the viscosity of feces, we designed a diaper that segregates the feces away from direct contact with skin. It was a semifinalist in the NASA Space Poop Challenge earlier this year. It just shows that physics and mathematics can be used everywhere, even in your toilet bowl. More information: Patricia J Yang et al. Hydrodynamics of defecation, Soft Matter (2017). DOI: 10.1039/C6SM02795D


News Article | April 17, 2017
Site: phys.org

Hydrogelators, which have a stacked fibrous network structure, can potentially be used in bioengineering, pharmaceutical technologies, environmental remediation, catalytic processes and personal care products. In collaborative research published in Soft Matter earlier this year, a group of Australian investigators led by Curtin University and the University of Western Australia, also confirmed that the selection of electrolyte plays a key role in determining the strength of a hydrogel formed by calixerene (bound with the amino acid proline). Upon heating to 30° C, calixerene hydrogels formed with the electrolyte magnesium chloride increased in strength and maintained increased stiffness upon cooling. The compound exhibited significant hysteresis (a memory of the initial structure). The investigators pointed out that this unusual, reproducible behaviour did not result in a loss of water upon heating. Because the gel stiffness got smaller over repeated annealing, it suggested a dynamic rearrangement process was occurring. Atomic force microscopy imaging at the University of Western Australia revealed that new larger, straighter fibres formed at 25 – 30° C, possibly supporting the formation of a more robust gel while smaller fibres appeared to dissolve. Co-author Instrument scientist Chris Garvey authors confirmed the model of what was happening to the gel structure following annealing over the temperature range 10-30° C using SANS on QUOKKA. "SANS is the technique of choice for gelators because can determine how molecules behave in an ensemble while a parameter is changing," said Garvey. Scattering data indicated a change from uniform rod-like structures to a more complex system. "In this study, the SANS data was consistent with the structural model and scattering curve calculations," said Garvey. The authors report that in the MgCl hydrogel this represents a change from the initial configuration of long, flexible fibres to short, straight fibres upon heating, which become long, straight fibres when the system is cooled. The hydrogel formed with the electrolyte lithium chloride responded differently to annealing. "One of my co-authors is interested in tissue scaffolding as part of dementia research but there are a great many potential applications for low molecular weight gelators," said Garvey. "The study was undertaken because there are still aspects of their behaviour that need investigation, such as how gel structure evolve over time and how to ensure the stability of load bearing structures." Explore further: Better understanding of light harvesting may benefit agriculture More information: Emily C. Barker et al. Thermal annealing behaviour and gel to crystal transition of a low molecular weight hydrogelator, Soft Matter (2017). DOI: 10.1039/C6SM02431A


News Article | August 30, 2016
Site: www.spie.org

Plastic foil substrates and chromium oxide interlayers are used in a novel technology that combines high efficiency, low weight, and extreme flexibility in a single platform. In the pursuit to solve the fossil fuel energy crisis, the use and development of photovoltaic technologies is thriving. In this technology, nature's most abundant source of energy—sunlight—is directly tapped. To achieve this, light-absorbing materials that are highly efficient, lightweight, low-cost, and stable during operation are required. Organolead halide perovskites1 are one such class of materials that show promise for photovoltaic applications, and they have recently become a strong focus of solar cell research. Indeed, their cell efficiency has been increased to about 20%2 within only a few years. Organolead halide perovskites are popular because their raw materials are plentiful and cheap, and because they can be fabricated in a simple manner (i.e., optimal prerequisites for cheap solar power). The limited stability of many perovskite absorbers under ambient conditions, however, may ultimately limit the widespread adoption of these materials in solar cells (especially if heavy and costly packaging is to be avoided). The main issue that gives rise to the poor stability of perovskites is water ingress3 and the subsequent liberation of highly corrosive species that rapidly damage metal contacts. In a previous attempt to overcome this problem,4 thick carbon electrodes were used to enable solar cell operation under ambient conditions. Nonetheless, if power output per solar cell weight (a critical metric for all mobile applications)—as well as power conversion efficiency—is to be optimized, alternative strategies are required. In such approaches, it is necessary to maintain the thin and light form factor of a direct band gap absorber material. In our approach,5 we thus demonstrate ultrathin (3μm), highly flexible perovskite solar cells that have stabilized 12% efficiency and a power-per-weight value as high as 23W/g. To realize these devices, we use 1μm-thick plastic foils as substrates and we process (from solution, at low temperature) pinhole-free perovskite films at high yield. We achieve perfect growth of tightly packed perovskite crystallites by treating the transparent polymer electrode with dimethyl sulfoxide. In addition, we introduce a chromium oxide–chromium interlayer, which effectively protects the metal top contacts from reacting with the perovskite, to facilitate air-stable operation. The detailed structure of our solar foils is depicted in Figure 1, together with a photograph of the freestanding ultrathin solar cell. The transparent conducting electrode and the absorber layer are processed from solution, and the electron-selective metal top contacts are thermally evaporated. Figure 1. (a) Schematic illustration of the cell stack. Polyethylene terephthalate (PET) foils (1.4μm thick) serve as the substrate and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is the transparent hole-selective electrode. Using dimethyl sulfoxide as an additive promotes the formation of pinhole-free perovskite layers. A one-step solution precursor deposition method is used to form the methylammonium lead iodide absorber. Perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) constitute the electron-transport layers. The chromium (Cr) oxide (Cr O ) stabilizes the metal top contact so that the device can be operated in ambient air. Low-resistivity metals, e.g., gold (Au), copper (Cu), and aluminum (Al), complete the device, and a 1μm-thick capping layer of polyurethane is used for mechanical protection. (b) Photograph of freestanding 3μm-thick solar cells (with copper top-metal contacts). (a) Schematic illustration of the cell stack. Polyethylene terephthalate (PET) foils (1.4μm thick) serve as the substrate and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is the transparent hole-selective electrode. Using dimethyl sulfoxide as an additive promotes the formation of pinhole-free perovskite layers. A one-step solution precursor deposition method is used to form the methylammonium lead iodide absorber. Perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) constitute the electron-transport layers. The chromium (Cr) oxide (Cr) stabilizes the metal top contact so that the device can be operated in ambient air. Low-resistivity metals, e.g., gold (Au), copper (Cu), and aluminum (Al), complete the device, and a 1μm-thick capping layer of polyurethane is used for mechanical protection. (b) Photograph of freestanding 3μm-thick solar cells (with copper top-metal contacts). 5 Solar cells that have aluminum or gold in direct contact with the perovskite degrade immediately upon exposure to ambient atmosphere. The ingress of water into the absorber layer causes this degradation of the perovskite crystal structure, i.e., by the formation of intermediate hydrated phases. The degradation culminates in the reforming of lead iodide, after enough water has permeated the film. In contrast, chromium oxide is resistant to aggressive oxidizing conditions (even nitric acid and aqua regia). It is for this reason (i.e., the excellent stability) that chromium plating is used to form corrosion-resistant coatings on various metals, and why we use a chromium oxide interlayer to provide an excellent buffer to shield the top-contact metal from chemical etching. We packaged our air-stable, thin, light solar cells (with a micrometer-thick spray-on polyurethane coating) so that they could be operated in field tests, where we used the solar panels to power various unmanned aerial vehicles. A snapshot of our model airplane, on a solar-powered flight, is shown in Figure 2. The same airplane is shown with our solar-powered blimp and a ‘solar leaf’ in a short video clip available online.6 For these tests, we powered the airplane and blimp with a 3μm-thick, 5.2g/cm2, light solar panel (with 64 individual cells). The high power-per-weight performance of our devices (i.e., up to 23W/g) is vital for such applications. Several other solar technologies for decentralized power generation and distribution (e.g., blimps, weather balloons, robotic insects, smart buildings, and aerospace applications), environmental and industrial monitoring, rescue and emergency response, as well as tactical security applications, all have a similar requirement. With our new technology we combine high power conversion efficiency, minimal weight, flexibility, mechanical resilience, operational stability, and low cost in a single platform and thus make the realization of these future concepts possible. Figure 2. Snapshot of the model airplane powered by the perovskite solar cell. This image was captured while the airplane was flying on a sunny winter afternoon (on the campus of the Johannes Kepler University). The airplane has a total weight of about 4.8g and is powered by air-stable, 3μm-thick solar arrays (with a power-per-weight value of 23W/g). The wingspan is 58cm. Through our tests we have also clearly demonstrated the high yield at which we fabricated the solar cells (even on thin, rough plastic foils). Our solar foils are extremely flexible and can endure severe mechanical deformation. In addition, they become stretchable (as shown in the video6) when they are laminated on a pre-stretched rubber band and they conform to arbitrary surfaces. Our foils are therefore ideal power sources for applications where conformability, stretchability, and light weight are required (e.g., portables, wearables, and robotics). In summary, we have presented a novel approach for achieving ultrathin, highly flexible perovskite solar cells. Our devices exhibit stable operation in air, 12% efficiency, and a power-per-weight value of up to 23W/g. The concepts we introduce (i.e., plastic foil substrates and chromium oxide interlayers) are readily applicable to the growing family of perovskite absorbers and could be used to increase the power-per-weight of such materials even further. By merging high efficiency, low weight, and extreme flexibility in our single photovoltaic platform, there seem to be few obstacles to keeping perovskite solar cells grounded. Indeed, our aeronautic models are still fully functional more than six months after their initial flights. In our future research we plan to focus on realizing perovskites with improved efficiency and moisture resistance (by exploring electrode transport materials, alternative metals, and superhydrophobic coatings). We will also investigate further ways to unify the high efficiency of perovskite cells with the low weight and flexibility of our technology. This work was supported by a European Research Council Advanced Investigators Grant (‘Soft-Map’) to Siegfied Bauer and the Austrian Science Fund's Wittgenstein Award (Solare Energie Umwandlung Z222-N19) to Niyazi Serdar Sariciftci. Department of Soft Matter Physics Johannes Kepler University Martin Kaltenbrunner received his PhD from the Johannes Kepler University Linz and then joined the Someya-Sekitani Laboratory for Organic Electronics at the University of Tokyo, Japan. He is now an assistant professor. His research interests include soft transducers, photovoltaics, as well as thin-film, flexible, and stretchable electronics. Siegfried Bauer received his PhD from the University of Karlsruhe, Germany. After stays at the Heinrich Hertz Institute in Berlin and the University of Potsdam (both Germany), he became a professor at the Johannes Kepler University Linz. He has has been head of the department since 2002. His research is devoted to functional soft matter. Institute for Physical Chemistry Johannes Kepler University Niyazi Serdar Sariciftci received his PhD from the University of Vienna, Austria. Following time at the University of Stuttgart, Germany, and the University of California at Santa Barbara, he became a professor at the Johannes Kepler University Linz in 1996. He has been a fellow of SPIE since 2009. His research is focused on organic photovoltaics and energy conversion. 3. A. M. A. Leguy, Y. Hu, M. Campoy-Quiles, M. I. Alonso, O. J. Weber, P. Azarhoosh, M. van Schilfgaarde, et al., Reversible hydration of CH NH PbI in films, single crystals, and solar cells, Chem. Mater. 27, p. 3397-3407, 2015. 5. M. Kaltenbrunner, G. Adam, E. D. Glowacki, M. Drack, R. Schwödiauer, L. Leonat, D. H. Apaydin, et al., Flexible high power-per-weight perovskite solar cells with chromium oxide–metal contacts for improved stability in air, Nat. Mater. 14, p. 1032-1039, 2015. 6. http://spie.org/documents/newsroom/videos/6223/Kaltenbrunner-solar_plane.mp4 a ‘solar leaf’ operated outdoors on sunny winter afternoons, with about 40 kilolux solar irradiation.


News Article | December 15, 2016
Site: www.eurekalert.org

For the first time, light is used to specifically design defined molecule chains; publication in Nature Communications Chemists of Karlsruhe Institute of Technology (KIT) have succeeded in specifically controlling the setup of precision polymers by light-induced chemical reactions. The new method allows for the precise, planned arrangement of the chain links, i.e. monomers, along polymer chains of standard length. The precisely structured macromolecules develop defined properties and may possibly be suited for use as storage systems of information or synthetic biomolecules. This novel synthesis reaction is now reported in open-access Nature Communications. (DOI: 10.1038/NCOMMS13672) Chemical reactions may be triggered by light at room temperature. This effect was used by KIT scientists to specifically link molecules to defined polymer chains under light. "In many conventional processes, polymer chains of variable length are produced. The building blocks are arranged randomly along the chain," says Professor Christopher Barner-Kowollik of the KIT Institute for Chemical Technology and Polymer Chemistry (ITCP). "We wanted to develop a light-induced method for polymer structuring, which reaches the precision of nature," the Holder of the Chair for Preparative Macromolecular Chemistry adds. The models in nature, e.g. proteins, have an exactly defined structure. The new, light-induced synthesis method allows for customized molecule design, with the building blocks being arranged at the positions desired similar to a string of colored pearls. "By controlling the structure of the molecule, the so-called sequence, properties of macromolecules can be controlled," Barner-Kowollik says. "Sequence-defined polymers might also be used as molecular data and information storage systems." Information might be encoded by the sequence of monomers, similar to the genetic information of the DNA. The team of Barner-Kowollik now presents the new light-induced and highly precise polymerization method in Nature Communications under the heading of "Coding and Decoding Libraries of Sequence Defined Functional Copolymers Synthesized via Photoligation." The developers expect the fundamental method to become a tool for chemists, biologists, and materials scientists and to be the key to future macromolecular chemistry. The new method was developed under the Collaborative Research Center 1176 "Molecular Structuring of Soft Matter" which is funded by the German Research Foundation (DFG) and coordinated by KIT. For the first four years, a budget of EUR 9 million is available to the Collaborative Research Center that started in January 2016. Nicolas Zydziak, Waldemar Konrad, Florian Feist, Sergii Afonin, Steffen Weidner, and Christopher Barner-Kowollik: Coding and Decoding Libraries of Sequence Defined Functional Copolymers Synthesized via Photoligation. DOI: 10.1038/NCOMMS13672 Karlsruhe Institute of Technology (KIT) pools its three core tasks of research, higher education, and innovation in a mission. With about 9,300 employees and 25,000 students, KIT is one of the big institutions of research and higher education in natural sciences and engineering in Europe. KIT - The Research University in the Helmholtz Association Since 2010, the KIT has been certified as a family-friendly university.


News Article | December 15, 2016
Site: phys.org

Chemists of Karlsruhe Institute of Technology (KIT) have succeeded in specifically controlling the setup of precision polymers by light-induced chemical reactions. The new method allows for the precise, planned arrangement of the chain links, i.e. monomers, along polymer chains of standard length. The precisely structured macromolecules develop defined properties and may possibly be suited for use as storage systems of information or synthetic biomolecules. This novel synthesis reaction is now reported in open-access Nature Communications. Chemical reactions may be triggered by light at room temperature. This effect was used by KIT scientists to specifically link molecules to defined polymer chains under light. "In many conventional processes, polymer chains of variable length are produced. The building blocks are arranged randomly along the chain," says Professor Christopher Barner-Kowollik of the KIT Institute for Chemical Technology and Polymer Chemistry (ITCP). "We wanted to develop a light-induced method for polymer structuring, which reaches the precision of nature," the Holder of the Chair for Preparative Macromolecular Chemistry adds. The models in nature, e.g. proteins, have an exactly defined structure. The new, light-induced synthesis method allows for customized molecule design, with the building blocks being arranged at the positions desired similar to a string of colored pearls. "By controlling the structure of the molecule, the so-called sequence, properties of macromolecules can be controlled," Barner-Kowollik says. "Sequence-defined polymers might also be used as molecular data and information storage systems." Information might be encoded by the sequence of monomers, similar to the genetic information of the DNA. The team of Barner-Kowollik now presents the new light-induced and highly precise polymerization method in Nature Communications under the heading of "Coding and Decoding Libraries of Sequence Defined Functional Copolymers Synthesized via Photoligation." The developers expect the fundamental method to become a tool for chemists, biologists, and materials scientists and to be the key to future macromolecular chemistry. The new method was developed under the Collaborative Research Center 1176 "Molecular Structuring of Soft Matter" which is funded by the German Research Foundation (DFG) and coordinated by KIT. For the first four years, a budget of EUR 9 million is available to the Collaborative Research Center that started in January 2016. More information: Nicolas Zydziak et al. Coding and decoding libraries of sequence-defined functional copolymers synthesized via photoligation, Nature Communications (2016). DOI: 10.1038/NCOMMS13672


News Article | December 15, 2016
Site: www.cemag.us

Chemists of Karlsruhe Institute of Technology (KIT) have succeeded in specifically controlling the setup of precision polymers by light-induced chemical reactions. The new method allows for the precise, planned arrangement of the chain links, i.e. monomers, along polymer chains of standard length. The precisely structured macromolecules develop defined properties and may possibly be suited for use as storage systems of information or synthetic biomolecules. This novel synthesis reaction is now reported in Nature Communications. Chemical reactions may be triggered by light at room temperature. This effect was used by KIT scientists to specifically link molecules to defined polymer chains under light. “In many conventional processes, polymer chains of variable length are produced. The building blocks are arranged randomly along the chain,” says Professor Christopher Barner-Kowollik of the KIT Institute for Chemical Technology and Polymer Chemistry (ITCP). “We wanted to develop a light-induced method for polymer structuring, which reaches the precision of nature,” the Holder of the Chair for Preparative Macromolecular Chemistry adds. The models in nature, e.g. proteins, have an exactly defined structure. The new, light-induced synthesis method allows for customized molecule design, with the building blocks being arranged at the positions desired similar to a string of colored pearls. "By controlling the structure of the molecule, the so-called sequence, properties of macromolecules can be controlled,” Barner-Kowollik says. “Sequence-defined polymers might also be used as molecular data and information storage systems.” Information might be encoded by the sequence of monomers, similar to the genetic information of the DNA. The team of Barner-Kowollik now presents the new light-induced and highly precise polymerization method in Nature Communications under the heading of “Coding and Decoding Libraries of Sequence Defined Functional Copolymers Synthesized via Photoligation.” The developers expect the fundamental method to become a tool for chemists, biologists, and materials scientists and to be the key to future macromolecular chemistry. The new method was developed under the Collaborative Research Center 1176 “Molecular Structuring of Soft Matter” which is funded by the German Research Foundation (DFG) and coordinated by KIT. For the first four years, a budget of EUR 9 million is available to the Collaborative Research Center that started in January 2016.


News Article | November 22, 2016
Site: www.eurekalert.org

Liquids are an important part of our everyday lives. Fluids such as water are Newtonian, and their viscous behavior is well understood. However, many common fluids are viscoelastic. These fluids, such as those commonly found in cosmetics, soaps and paints, possess a combination of viscous, liquid-like and elastic, solid-like properties and we know surprisingly little about how they flow. Despite not knowing much about their flow properties, manufactures add these fluids to many different types of everyday products. Without viscoelastic fluids, life would feel much different. We wouldn't be able to enjoy the rich lather of shampoos, nor the chewy texture of a gummy candy, nor the springy comfort of a well-built athletic shoe. To understand more about these fluids, researchers from the Micro/Bio/Nanofluidics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) study the flow properties and behavior of different viscoelastic fluids. Prof. Amy Shen, leader of the unit, and Dr. Simon Haward, the group leader of the unit, are investigating two specific types of liquids commonly used in manufactured products: polymer solutions and 'living polymer' solutions. Polymers are long molecules comprised of repeating subunits. Polymeric solutions have a wide range of applications, particularly in the formulation of foods, inks, paints and even prosthetic fluids such as eyedrops and artificial saliva. During flow, these long polymer molecules can become stretched out like rubber bands, which give the fluid its elasticity. In a collaborative study with Massachusetts Institute of Technology researcher Professor Gareth McKinley, Shen and Haward observed the flow patterns of a series of viscoelastic polymer solutions through a 4-way junction (Figure 1). Using a technique called flow-induced birefringence, they showed that as the rate of flow through the junction was increased, polymer molecules became highly stretched out at in a narrow strand passing through the center of the junction. Flow induced birefringence is caused by small measurable changes in the refraction of light passing through a liquid when it is made to flow. These changes in light refraction directly correlate to elastic stresses in the flowing fluid. The researchers found that the strong elasticity within the birefringent strand caused severe distortions of the observed flow patterns. Increasing the flow rate further led to the onset of large fluctuations or instabilities in the flow patterns. These experiments allowed the researchers to show that the mechanism for the onset of instability in this stretching flow is consistent with that for viscoelastic instabilities in other, more simple kinds of flows. In a curved pipe, for example, the onset of instability can be quite well predicted depending on the precise geometric conditions and fluid properties. However, until now it has never been shown that similar predictions can be applied to stretching flows. Many industrial processes, such as extrusion, fiber-spinning and inkjet printing, involve stretching flows of viscoelastic fluids. Flow instabilities generally have a detrimental effect on the quality of end products and so directly limit the rates at which such processes can be carried out. The ability to predict the onset of instabilities in such flows can aid in optimizing processing rates and obtaining superior end products. The results of the study are published in the open access Nature Publishing journal Scientific Reports. The Micro/Bio/Nanofluidics Unit also studies the flow of 'living polymers'. Like polymers, these materials form long chains of multiple repeating units, but unlike polymers, these units are not chemically bound together, but rely on other forces for cohesion. Wormlike micelles (WLM), a type of 'living polymer', form long, rod-like aggregates suspended in a solution. As with polymers, these materials have numerous industrial applications, including as additives in shampoos and cosmetics and as materials to enhance oil and gas recovery (EOR). WLM solutions are pumped into shale during fracking in order to extract more oil and gas from these underground rock formations. The solutions are initially thick and gel-like, which allows them to generate high pressures and fracture the shale. However, when they come into contact with the hydrocarbons, the micelles disassemble allowing the solution to behave more like water and easily flow out of the rock. These shale formations contain many obstructions that alter the flow of solutions within. Prof. Shen decided to use a simplified model to study the flow pattern of WLM solutions when a blockage is present. Dr. Ya Zhao, a former graduate student of Prof. Shen at the University of Washington, built a micro-scale channel in which she could observe the flow of WLM solutions around a cylinder acting as an obstruction in the flow path. She then compared the flow patterns of a Newtonian fluid and a WLM solution by observing the streaks formed by fluorescent tracer particles. She also measured the growth of stresses in the WLM solution using flow-induced birefringence. This research, published in Soft Matter and featured on the inside front cover, revealed some unique flow patterns with the WLM solution. "Unlike Newtonian fluids," Shen explains, "WLM solutions initiate flow instability upstream of the obstruction. Additionally, it was discovered that the degree of instability was directly related to the size of the blockage compared to the total width of the channel". Determining how these materials flow is vitally important in optimizing their applications. These materials exist in a wide variety of products and are exploited in many industrial processes, making their optimization a priority for manufacturers. Determining their flow behavior is one step closer to achieving the full potential of these products.

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