Eczema woes not just skin deep

 

Eczema wreaks havoc on its sufferers' lives with health problems that are more than skin deep. Adults who have eczema -- a chronic itchy skin disease that often starts in childhood -- have higher rates of smoking, drinking alcoholic beverages and obesity and are less likely to exercise than adults who don't have the disease, reports a new Northwestern Medicine® study. These behaviors give them a higher risk of cardiovascular disease, including high blood pressure and high cholesterol as well as diabetes. They also have higher rates of insomnia. "This disease takes a huge emotional toll on its sufferers, like chronic pain," said lead study author Dr. Jonathan Silverberg. "Because eczema often starts in early childhood, people are affected all through their developmental years and adolescence. It hurts their self-esteem and identity. That's part of why we see all these negative behaviors." Silverberg is an assistant professor of dermatology at Northwestern University Feinberg School of Medicine and a dermatologist at Northwestern Memorial Hospital. He also is director of the Northwestern Medicine Multidisciplinary Eczema Center. Adding to eczema patients' health woes is difficulty exercising, because sweat and heat aggravate the itching. "They will avoid anything that triggers the itch," Silverberg said. "Patients report their eczema flares during a workout." The study was published Jan. 8 in the Journal of Allergy and Clinical Immunology. "This opens our eyes in the world of dermatology that we're not just treating chronic inflammation of the skin but the behavioral, lifestyle side of things," Silverberg said. Dermatologists need to ask patients about their lifestyle habits such as smoking and physical activity so they can offer interventions. The study analyzed data for 27,157 and 34,525 adults aged 18 to 85 years from the 2010 and 2012 National Health Interview Survey. The Northwestern study reported patients with eczema had 54 percent higher odds of being morbidly obese, 48 percent higher odds of hypertension, up to 93 percent higher odds of having pre-diabetes and up to 42 percent higher odds of having diabetes. They also had 36 percent higher odds of high cholesterol. Silverberg said patients should be offered interventions for alcohol and smoking by their dermatologists. In addition, he is collaborating with colleagues in Northwestern's department of physical therapy and human movement sciences to figure out how patients with eczema can exercise to improve their health without worsening their skin flare-ups. Story Source: The above story is based on materials provided by Northwestern University. The original article was written by Marla Paul. Note: Materials may be edited for content and length. Journal Reference: Jonathan I. Silverberg, Philip Greenland. Eczema and cardiovascular risk factors in 2 US adult population studies. Journal of Allergy and Clinical Immunology, 2015; DOI: 10.1016/j.jaci.2014.11.023

Inventors choose to reveal their secret sauce before patent approval

 

January 15, 2015 Georgia Institute of Technology Common wisdom and prior economic research suggest that an inventor filing a patent would want to keep the technical know-how secret as long as possible. But a new study of nearly 2 million patents shows that inventors are not as concerned with secrecy as previously thought. Researchers found that since 2000, most inventors when given the choice opted to disclose information about their patents before patent approval -- even small inventors -- and this disclosure correlates with more valuable patents. Common wisdom and prior economic research suggest that an inventor filing a patent would want to keep the technical know-how secret as long as possible. But a new study of nearly 2 million patents shows that inventors are not as concerned with secrecy as previously thought. Researchers found that since 2000, most inventors when given the choice opted to disclose information about their patents before patent approval -- even small inventors -- and this disclosure correlates with more valuable patents. "Do inventors really value the secrecy that economists assumed they did based on the prior literature? Our findings are that overwhelmingly, and in every category that we can test, inventors don't," said Stuart Graham, study co-author and assistant professor at the Georgia Institute of Technology's Scheller College of Business. Graham was the first-ever chief economist appointed at the U.S. Patent and Trademark Office (USPTO), serving in the U.S. Department of Commerce while on leave from Georgia Tech from 2010 to 2013. The study, co-authored with Deepak Hegde (New York University), will be published January 16 in the journal Science, and was sponsored in part by the Ewing Marion Kauffman Foundation. During the congressional debate over the AIPA, prominent inventors raised concerns that reduced secrecy would harm not only small inventors, but undermine the inventive spirit throughout the world. So a loophole was included in the AIPA, allowing inventors to maintain secrecy of their patent applications if they were not also filing for parallel foreign patent protection on the same invention. The change in the law created an opportunity for Graham and his colleague Deepak Hegde, an assistant professor of management and organizations at NYU's Stern School of Business, to examine which inventors were choosing to opt into the secrecy loophole, and whether their patents differed in important ways. They examined 1.8 million granted patents filed at the USPTO from 1995 to 2005 and analyzed the disclosure preferences of the inventors. Their analysis found that, among those not seeking foreign protection, about 85 percent of inventors filing a patent since 2000 chose to disclose information about their patents prior to their approval. "Overwhelmingly, those inventors patenting only in the U.S. are choosing 18 month disclosure," co-author Hegde said. The patents examined in the study are called utility patents, which are available on new and useful processes, machines, manufactured articles, or compositions, and protect technologies like software, laptops, medical devices, and drugs. These are the commonest type of patent with more than 570,000 filed at the USPTO in 2013, each containing technical information. When the AIPA was passed, one of the biggest complaints was that the publication requirement would hurt U.S. small inventors, but the researchers found that individuals and small companies still opted for disclosure during the study period. "Small U.S. inventors are not choosing the secrecy route," Graham said. "When they patent only in the U.S., they are choosing secrecy in only about 15 percent of the cases, not statistically different than the rate among all other types of inventors." Another major complaint of the AIPA was that disclosing patent secrets would stop the engine of innovation in the United States and that society would get less meaningful inventions. Contrary to these arguments, the researchers found that patents born out of secrecy were overall less valuable than those that opted for disclosure. "When we examine indicators of patent value, we find consistent evidence that the least-valuable and least-impactful patents are those that opted for pre-grant secrecy," Hegde said. The authors point out that more patent information, provided to society earlier, could be socially beneficial. Publishing patent information earlier may provide a head start for other innovators, and may help society avoid unnecessary duplicative research spending, the researchers said. "We have limited resources in our society that we can invest in innovation and invention," Graham said. "To the extent that we can more efficiently choose projects and avoid wasteful, redundant efforts, then that's good for us as a society." Future work will involve pinpointing why inventors are choosing not to keep their patent information secret until grant. Some possible answers are that disclosure acts as an early signal to competitors to not innovate in that technology space, or announces to potential licensees that a technology is coming to the marketplace and may be available as an input for someone else's manufacturing or engineering process. "This study is a first window into what inventors are really doing. The next question is why are they doing it?" Graham said. "It remains for us to figure out why inventors seeking to maximize the value of their inventions are not particularly interested in pre-patent secrecy." Story Source: The above story is based on materials provided by Georgia Institute of Technology. Note: Materials may be edited for content and length. Journal Reference: S. Graham, D. Hegde. Disclosing patents' secrets. Science, 2015; 347 (6219): 236 DOI: 10.1126/science.1262080

When used effectively, discharge summaries reduce hospital readmissions

 

New Yale research shows how effectively using discharge summaries can prevent hospital readmissions for heart failure patients. For heart failure patients making the transition from hospital to home, a discharge summary that gets to their primary doctors quickly and contains detailed and useful information can mean the difference between recovering quickly or returning to the hospital, according to two studies from Yale School of Medicine researchers. The findings are published by the Yale research team in the current issue of Circulation: Cardiovascular Quality and Outcomes. In theory, a discharge summary is meant to help outside physicians understand what happened to patients while they were hospitalized, but in practice, it has served as an aid for medical billing, according to lead author Leora Horwitz, M.D., adjunct associate professor of internal medicine at Yale School of Medicine and director of the Center for Healthcare Innovation and Delivery Science at New York University Langone Medical Center. "The medical community hasn't really made full use of discharge summaries as a tool for transitions," she said. Horwitz and her team analyzed data from Telemonitoring to Improve Heart Failure Outcomes (Tele-HF), a large multicenter study of patients hospitalized with heart failure. This data contained more than 1,500 discharge summaries from 46 hospitals across the country. Horwitz said in order for a discharge summary to do the job of making the transition from hospital to home safer, it needs three key factors: It has to be timely, it has to be sent to the outside physician, and it has to include useful information. "It's like a three-legged stool," she said. "All three need to be present in order for it to do its job." In the first study, Horwitz and her team expected the summaries to be similar at all the hospitals they analyzed, but they found that hospitals varied widely in their performance. And even at the highest-performing hospitals, the quality of discharge summaries was insufficient in terms of timeliness, transmission, and content. No hospital consistently produced high-quality summaries in all domains. In the second study using the same data from Tele-HF, the team looked at whether improving hospital practices regarding discharge summaries made a difference in hospital readmissions. They found that discharge summary quality was indeed associated with readmission risk; patients whose summaries included useful content or were sent to outside clinicians had lower readmission rates. "This study tells us for the first time that it is actually worth spending the time and effort to improve discharge communication, and patients do seem to benefit," said Horwitz. Story Source: The above story is based on materials provided by Yale University. The original article was written by Karen N. Peart. Note: Materials may be edited for content and length. Journal References: M. S. Al-Damluji, K. Dzara, B. Hodshon, N. Punnanithinont, H. M. Krumholz, S. I. Chaudhry, L. I. Horwitz. Hospital Variation in Quality of Discharge Summaries for Patients Hospitalized With Heart Failure Exacerbation. Circulation: Cardiovascular Quality and Outcomes, 2015; DOI: 10.1161/CIRCOUTCOMES.114.001227 M. S. Al-Damluji, K. Dzara, B. Hodshon, N. Punnanithinont, H. M. Krumholz, S. I. Chaudhry, L. I. Horwitz. Association of Discharge Summary Quality With Readmission Risk for Patients Hospitalized With Heart Failure Exacerbation. Circulation: Cardiovascular Quality and Outcomes, 2015; DOI: 10.1161/CIRCOUTCOMES.114.001476

Study reveals lack of data on opioid drugs for chronic pain

 

A National Institutes of Health white paper that was released today finds little to no evidence for the effectiveness of opioid drugs in the treatment of long-term chronic pain, despite the explosive recent growth in the use of the drugs. The paper, which constitutes the final report of a seven-member panel convened by the NIH last September, finds that many of the studies used to justify the prescription of these drugs were either poorly conducted or of an insufficient duration. An NIH white paper finds little to no evidence for the effectiveness of opioid drugs in the treatment of long-term chronic pain. That makes prolific use of these drugs surprising, says Dr. David Steffens, chair of the psychiatry department at UConn Health and one of the authors of the study. When it comes to long-term pain, he says, "there's no research-based evidence that these medicines are helpful." Yet despite this, prescriptions for opioid drugs (also known as opiate drugs; the two terms are technically distinct, but most physicians use them interchangeably) have more than tripled in the past 20 years, with more than 219 million prescriptions written in 2011, according to the study. At the same time, the abuse of these drugs has also skyrocketed, leading some to refer to prescription drug abuse as an epidemic. More than 16,000 people died from prescription opioid overdoses in 2012, according to the Centers for Disease Control, and drug overdose now causes more deaths than motor vehicle accidents for people ages 25-64. This level of opioid use and abuse is unprecedented in the world: the United States, with just 4.6 percent of the world's population, consumes 80 percent of the world's opioid drugs. That, says Steffens, makes this "a peculiarly American problem." Steffens, like the other members of the panel, was surprised by many of these findings, since he is not an expert in opioid drugs, in drug abuse, or in pain management. The members of the panel were experienced clinicians with expertise in other areas; Steffens' specialty is geriatric psychiatry. "The NIH intentionally invited people from other fields of medicine," he says, "in order to avoid potential conflicts of interest, and to get a fresh perspective on the issue." Over two days, the panel listened to evidence presented by an outside agency, which had conducted an exhaustive search of all the available studies about the use of opioid drugs. The panel's draft report was made available for public comment late last fall. The final report is published in the Annals of Internal Medicine. Steffens notes that one of the great challenges in grappling with this issue is the fact that opioid drugs clearly are an effective treatment for some people dealing with pain, but it is hard to predict where trouble will crop up. Part of the problem, he points out, is the need for better communication about best practices to physicians who are prescribing these drugs. "There are certain syndromes, like fibromyalgia, where opioids are less likely to be effective and patients are more likely get into trouble with abuse," says Steffens. Another issue both for patients and for society at large is that pills from the pharmacy don't always end up in the hands they were prescribed for. The process of medicine being sold or given away (known as diversion) has long been identified as a key driver in the rise of prescription drug abuse. Says Steffens, "I wish that doctors treating people for sports or workplace injuries would be cautious with the amount of pills they dispense." Story Source: The above story is based on materials provided by University of Connecticut. The original article was written by Tim Miller. Note: Materials may be edited for content and length. Journal Reference: David B. Reuben, Anika A. H. Alvanzo, Takamaru Ashikaga, G. Anne Bogat, Christopher M. Callahan, Victoria Ruffing, David C. Steffens. National Institutes of Health Pathways to Prevention Workshop: The Role of Opioids in the Treatment of Chronic Pain. Annals of Internal Medicine, 2015; DOI: 10.7326/M14-2775

Liquids and glasses relax, too -- but not like you thought

 

At the picosecond scale, liquids move not so much in a gang rush as a follow-the-leader process akin to the space moving around in a 15 puzzle, according to a group of NIST researchers. The physical model they propose has implications for the design of protein-based drugs that must be stored for long periods at room temperature. A new insight into the fundamental mechanics of the movement of molecules recently published by researchers at the National Institute of Standards and Technology (NIST) offers a surprising view of what happens when you pour a liquid out of a cup. More important, it provides a theoretical foundation for a molecular-level process that must be controlled to ensure the stability of important protein-based drugs at room temperature. Proteins depend critically on their three-dimensional structure, the shape the long and complex molecules tend to fold into. Modern protein-based drugs -- for example, vaccines or antibodies created to fight cancers -- generally are not stable at room temperature or in the liquid formulations most convenient for clinical use. To preserve them for use in parts of the world without reliable refrigeration, manufacturers freeze-dry the proteins and coat the complex molecules with glassy sugars to keep their structure intact. "It's like a lollypop," observes NIST biochemist Marcus Cicerone, "but these lollypops are only 10 microns or smaller." The challenge is to design the sugar coating to get the maximum shelf life for a given pharmaceutical protein, which ideally would be measured in years. The issue revolves around what chemists refer to as "relaxation" -- broadly, any molecular motion that leads to transport of the molecule. About 10 years ago, NIST researchers discovered a testing shortcut. Using neutron radiation, they discovered that measuring tiny molecular movements in the proteins at very short timescales -- picoseconds* -- could reliably predict the long-term stability of a formulation. The sugars that worked the best were the ones that suppressed the tiny, rapid motions. Exactly why this was so was not particularly clear, but it worked. This new paper finally explains the underlying principles. The neutron experiments, says Cicerone, measure mean square displacement. "Imagine a jarful of molecules. It's how far the average molecule jiggles around for a given timescale," he says. "In condensed matter like a liquid or glass, we usually think that all the molecules are identical, and on the average they all have the same environment with a little bit of space for them to jiggle, but not very much." "What we found is that picture is not really right." In reality, Cicerone says, there are two different environments the molecules can be in. "There is one environment like that -- molecules are very well packed and on a picosecond timescale they move maybe one percent of their radius. They're hardly moving at all. But there's another environment where some molecules can move maybe 30 percent of their radius in the same time.They're really making big jumps, and in glasses, those big jumps are essentially the only way that molecules can move around. Everybody else is completely stuck. "It's kind of like a 15 puzzle. You can only move one at a time." What happens is a molecule next to a region that's more loosely packed can move there, and does. Then one that was next to it suddenly has room to move, and does, and so on. On a picosecond and nanometer scale of time and space, when you pour a liquid out of a cup, it doesn't really all come out all at once. It's more follow-the-leader. On a practical level, says Cicerone, the results explain why the short timescale mean displacement measurements can predict the results of molecular degradation measurements that would normally take months. "It gives a really good solid understanding of why these picosecond and nanosecond timescale measurements correlate with degradation processes in glass for the proteins," he says, "so it gives us confidence that the techniques we build that are based on this idea will be robust and people will be able to use them." As a bonus, he says, the model also explains a somewhat arcane degradation process in glasses called Johari-Goldstein relaxation. "It's the timescale for the switching between the tightly packed and loosely packed regions. It's the vacancy in the game of 15 moving around," says Cicerone. *0.000 000 000 001 second Story Source: The above story is based on materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length. Journal Reference: Marcus T. Cicerone, Qin Zhong, Madhusudan Tyagi. Picosecond Dynamic Heterogeneity, Hopping, and Johari-Goldstein Relaxation in Glass-Forming Liquids. Physical Review Letters, 2014; 113 (11) DOI: 10.1103/PhysRevLett.113.117801

"Affordable" Chevrolet Bolt electric vehicle concept has a range of 200 miles

 

The Chevrolet Bolt EV concept has a range of 200 miles (322 km) and should cost around $30,000 (Photo: Loz Blain/Gizmag) Image Gallery (13 images) Two of the biggest obstacles to the widespread adoption of electric vehicles (EVs) have been their prohibitively high prices and limited ranges. Chevrolet's new Bolt EV concept seeks to tackle both of these factors. It is designed to go 200 miles (322 km) per charge and cost from around US$30,000. Chevrolet says it has used the knowledge gained from its Volt and Spark EVs to produce the Bolt. "We have made tremendous strides in technologies that make it easier and more affordable for Chevrolet customers to integrate an all-electric vehicle in their daily lives," said General Motors CEO Mary Barra. Amongst the technologies present in the car is the ability to change driving mode depending on the environment in which it is being used. Available modes are tailored towards daily commuting and "spirited weekend cruising," as well as other situations. Selecting different modes changes aspects of the car's setup, such as accelerator pedal mapping, vehicle ride height and suspension tuning. The Bolt is also said to support DC fast charging and has LED headlights and taillights. The Bolt's weight has been kept to a minimum by using lightweight materials, including aluminum, magnesium, carbon fiber and woven mesh. This helps to increase the vehicle's range. Chevrolet says the car has been designed in such a way as to minimize any overhang at both the front and the rear, maximizing interior space. A large glass roof and large expanses of glass right around the vehicle, meanwhile, allows plenty of light in and increases visibility. A variety of technologies are used inside the Bolt aimed at improving the driving experience. A 10-in touchscreen on the dashboard provides vehicle information, whilst the Bolt EV Connect app allows a user's smartphone to be used as a key fob and for ride-sharing management. The app also allows users to exit the vehicle and instruct it to park itself, before summoning it back to their location at a later time. The Chevrolet Bolt EV concept is currently on display at the North American International Auto Show in Detroit. There is no word on commercial availability. Source: Chevrolet Share About the Author Stu is a tech writer based in Liverpool, UK. He has previously worked on global digital estate management at Amaze and headed up digital strategy for FACT (Foundation for Art and Creative Technology). He likes cups of tea, bacon sandwiches and RSS feeds.   All articles by Stu Robarts

Skin care: 5 tips for healthy skin

 

Good skin care — including sun protection and gentle cleansing — can keep your skin healthy and glowing for years to come. By Mayo Clinic Staff Don't have time for intensive skin care? You can still pamper yourself by acing the basics. Good skin care and healthy lifestyle choices can help delay the natural aging process and prevent various skin problems. Get started with these five no-nonsense tips. 1. Protect yourself from the sun One of the most important ways to take care of your skin is to protect it from the sun. A lifetime of sun exposure can cause wrinkles, age spots and other skin problems — as well as increase the risk of skin cancer. For the most complete sun protection: Use sunscreen. Use a broad-spectrum sunscreen with an SPF of at least 15. Apply sunscreen generously, and reapply every two hours — or more often if you're swimming or perspiring. Seek shade. Avoid the sun between 10 a.m. and 2 p.m., when the sun's rays are strongest. Wear protective clothing. Cover your skin with tightly woven long-sleeved shirts, long pants and wide-brimmed hats. Also consider laundry additives, which give clothing an additional layer of ultraviolet protection for a certain number of washings, or special sun-protective clothing — which is specifically designed to block ultraviolet rays. 2. Don't smoke Smoking makes your skin look older and contributes to wrinkles. Smoking narrows the tiny blood vessels in the outermost layers of skin, which decreases blood flow. This depletes the skin of oxygen and nutrients that are important to skin health. Smoking also damages collagen and elastin — the fibers that give your skin strength and elasticity. In addition, the repetitive facial expressions you make when smoking — such as pursing your lips when inhaling and squinting your eyes to keep out smoke — can contribute to wrinkles. If you smoke, the best way to protect your skin is to quit. Ask your doctor for tips or treatments to help you stop smoking. Next Dec. 16, 2014 References See more In-depth

Astronaut Twins Available for Interviews about Yearlong Space Station Mission, Health Study

 

January 14, 2015 MEDIA ADVISORY M15-009 NASA astronaut Scott Kelly and his twin, former astronaut Mark Kelly, are pictured in the check-out facility at Ellington Field near NASA's Johnson Space Center in Houston on May 6, 2008. Image Credit: NASA/JSC NASA will host an opportunity for media to conduct in-person interviews with astronaut Scott Kelly and his twin brother, former astronaut Mark Kelly, Monday, Jan. 19. The twins will be available for in-person interviews from 5:30 to 6:30 p.m. EST at NASA’s Johnson Space Center in Houston. The opportunity previously had been planned for Tuesday, Jan. 20, but was changed due to a scheduling conflict. Scott and his Russian colleague, cosmonaut Mikhail Kornienko, embark March 27 on the first-ever yearlong mission to the International Space Station. Mark, who flew four space shuttle missions and commanded the final flight of space shuttle Endeavour, will participate in biomedical studies on the ground while his twin is aboard the orbiting laboratory. The valuable scientific data collected will provide insight into how the human body responds to longer durations in space, supporting the next generation of space exploration. In addition to a full suite of investigations to be conducted during the mission, scientists plan to compare medical data from the twins to better understand the results gleaned from Scott’s extended mission. To participate in the interviews, reporters must contact Nicole Cloutier-Lemasters at 281-483-5111 or nicole.cloutier-1@nasa.gov no later than 4 p.m. Thursday, Jan. 15. More information about the International Space Station and its crews is available at: http://www.nasa.gov/station Scott Kelly is sharing his mission preparation and journey to space on Twitter at: http://www.twitter.com/StationCDRKelly For Scott Kelly's full biography, visit: http://www.jsc.nasa.gov/Bios/htmlbios/kellysj.html For Mark Kelly’s full NASA biography, visit: http://www.jsc.nasa.gov/Bios/htmlbios/kellyme.html

One step closer to a next-generation electric car battery

 

Mon, 01/12/2015 - 11:22am Nick Manning, Univ. of Waterloo An ultra-thin nanomaterial is at the heart of a major breakthrough by Univ. of Waterloo scientists who are in a global race to invent a cheaper, lighter and more powerful rechargeable battery for electric vehicles. Chemistry Prof. Linda Nazar and her research team in the Faculty of Science at the Univ. of Waterloo have announced a breakthrough in lithium-sulphur battery technology in Nature Communications. Their discovery of a material that maintains a rechargable sulphur cathode helps to overcome a primary hurdle to building a lithium-sulphur (Li-S) battery. Such a battery can theoretically power an electric car three times further than current lithium-ion batteries for the same weight—at much lower cost. “This is a major step forward and brings the lithim-sulphur battery one step closer to reality,” said Nazar, who also holds the Canada Research Chair in Solid State Energy Materials and was named a Highly Cited Researcher by Thomson Reuters. Nazar’s group is best known for their 2009 Nature Materials paper demonstrating the feasibility of a Li-S battery using nanomaterials. In theory, sulphur can provide a competitive cathode material to lithium cobalt oxide in current lithium-ion cells. Sulphur as a battery material is extremely abundant, relatively light and very cheap. Unfortunately, the sulphur cathode exhausts itself after only a few cycles because the sulphur dissolves into the electrolyte solution as it’s reduced by incoming electrons to form polysulphides. Nazar’s group originally thought that porous carbons or graphenes could stabilize the polysulphides by physically trapping them. But in an unexpected twist, they discovered metal oxides could be the key. Their initial work on a metallic titanium oxide was published earlier in August in Nature Communications. While the researchers found since then that nanosheets of manganese dioxide (MnO2) work even better than titanium oxides, their main goal in this paper was to clarify the mechanism at work. “You have to focus on the fundamental understanding of the phenomenon before you can develop new, advanced materials,” said Nazar. They found that the oxygenated surface of the ultrathin MnO2 nanosheet chemically recycles the sulphides in a two-step process involving a surface-bound intermediate, polythiosulfate. The result is a high-performance cathode that can recharge more than 2000 cycles. The surface reaction is similar to the chemical process behind Wackenroder’s Solution discovered in 1845 during a golden age of German sulfur chemistry. “Very few researchers study or even teach sulphur chemistry anymore,” said Nazar. “It’s ironic we had to look so far back in the literature to understand something that may so radically change our future.” Source: Univ. of Waterloo

Manipulating nanoribbons at the molecular level

 

Mon, 01/12/2015 - 12:44pm Rachel Berkowitz, Lawrence Berkeley National Laboratory Figure 1: Bottom-up synthesis of graphene nanoribbons from molecular building blocks 1 and 2. (a) The resulting ribbon, or heterojunction, has varied widths as a result of different width molecules 1 and 2. (b) Scanning transmission microscope image of graphene nanoribbon heterojunction, with larger-scale inset of multiple ribbons.Narrow strips of graphene called nanoribbons exhibit extraordinary properties that make them important candidates for future nanoelectronic technologies. A barrier to exploiting them, however, is the difficulty of controlling their shape at the atomic scale, a prerequisite for many possible applications. Now, researchers at the U.S. Dept. of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the Univ. of California, Berkeley, have developed a new precision approach for synthesizing graphene nanoribbons from pre-designed molecular building blocks. Using this process the researchers have built nanoribbons that have enhanced properties—such as position-dependent, tunable bandgaps—that are potentially very useful for next-generation electronic circuitry. The results appear in Nature Nanotechnology. “This work represents progress towards the goal of controllably assembling molecules into whatever shapes we want,” says Mike Crommie, senior scientist at Berkeley Lab, professor at UC Berkeley, and a leader of the study. “For the first time we have created a molecular nanoribbon where the width changes exactly how we designed it to.” Nanoribbons past and present Previously, scientists made nanoribbons that have a constant width throughout. “That makes for a nice wire or a simple switching element,” says Crommie, “but it does not provide a lot of functionality. We wanted to see if we could change the width within a single nanoribbon, controlling the structure inside the nanoribbon at the atomic scale to give it new behavior that is potentially useful.” Felix Fischer, professor of chemistry at UC Berkeley who jointly led the study, designed the molecular components to find out whether this would be possible. Together, Fischer and Crommie discovered that molecules of different widths can indeed be made to chemically bond such that width is modulated along the length of a single resulting nanoribbon. “Think of the molecules as different sized Lego blocks,” explains Fischer. Each block has a certain defined structure and when pieced together they result in a particular shape for the whole nanoribbon. “We want to see if we can understand the exotic properties that emerge when we assemble these molecular structures, and to see if we can exploit them to build new functional devices.” Until now, nanoribbon synthesis has mostly involved etching ribbons out of larger 2-D sheets of graphene. The problem, according to Fischer, is that this lacks precision and each resulting nanoribbon has a unique, slightly random structure. Another method has been to unzip nanotubes to yield nanoribbons. This produces smoother edges than the “top-down” etching technique, but it is difficult to control because nanotubes have different widths and chiralities. A third route, discovered by Roman Fasel of Swiss Federal Laboratories for Materials Science & Technology along with his co-workers, involves placing molecules on a metal surface and chemically fusing them together to form perfectly uniform nanoribbons. Crommie and Fischer modified this last approach and have shown that if the shapes of the constituent molecules are varied then so is the shape of the resulting nanoribbon. “What we’ve done that is new is to show that it is possible to create atomically-precise nanoribbons with non-uniform shape by changing the shapes of the molecular building blocks,” says Crommie. Controlling quantum properties Electrons within the nanoribbons set up quantum mechanical standing-wave patterns that determine the nanoribbon’s electronic properties, such as its “bandgap”. This determines the energetics of how electrons move through a nanoribbon, including which regions they accumulate in and which regions they avoid. In the past, scientists spatially engineered the bandgap of micron-scale devices through doping, the addition of impurities to a material. For the smaller nanoribbons, however, it is possible to change the bandgap by modifying their width in sub-nanometer increments, a process that Crommie and Fischer have dubbed “molecular bandgap engineering.” This kind of engineering allows the researchers to tailor the quantum mechanical properties of nanoribbons so they might be flexibly used for future nanoelectronic devices. To test their molecular bandgap engineering, Crommie’s group used scanning tunneling microscopy (STM), a technique that can spatially map the behavior of electrons inside a single nanoribbon. “We needed to know the atomic-scale shape of the nanoribbons, and we also needed to know how the electrons inside adapt to that shape,” says Crommie. UC Berkeley professor of physics Steven Louie and his student Ting Cao calculated the electronic structure of the nanribbons in order to correctly interpret the STM images. This “closed the loop” between nanoribbon design, fabrication, and characterization. New directions toward new devices A major question in this work is how best to build useful devices from these tiny molecular structures. While the team has shown how to fabricate width-varying nanoribbons, it has not yet incorporated them into actual electronic circuits. Crommie and Fischer hope to use this new type of nanoribbon to eventually create new device elements – such as diodes, transistors, and LEDs—that are smaller and more powerful than those in current use. Ultimately they hope to incorporate nanoribbons into complex circuits that yield better performance than today’s computer chips. To this end they are collaborating with UC Berkeley electrical engineers such as Jeffrey Bokor and Sayeef Salahuddin. The required spatial precision already exists: the team can modulate nanoribbon width from 0.7 nm to 1.4nm, creating junctions where narrow nanoribbons fuse seamlessly into wider ones. “Varying the width by a factor of two allows us to modulate the bandgap by more than 1 eV,” says Fischer. For many applications this is sufficient for building useful devices. While the potential applications are exciting, Crommie points out that a central motivation for the research is the desire to answer basic scientific questions like how nanoribbons with non-uniform width actually behave. “We set out to answer an interesting question, and we answered it,” he concludes. Source: Lawrence Berkeley National Laboratory