Jesse Maassen wants to understand how electrons and heat flow through materials so he can capture excess energy from heat sources and use it to generate electrical power. “My research group’s overarching theme is the study of electro-thermal transport in materials and devices — such as semi-conductors and metals — using theory and simulation,” says Maassen, a professor in the physics and atmospheric science department at Dalhousie University. “We focus on understanding what controls the movement of electrons and heat in materials, so we can design new materials with enhanced properties.” One of the materials he studies is called thermoelectrics. When thermoelectrics are placed in contact with heat sources, they can convert the thermal energy into useful electrical energy, that can be used for everything from charging our phones to powering our homes. For example, using heat from combustion in a car, you can power some of the car’s battery. “Thermoelectrics could have a big impact,” he says. “Roughly 60 per cent of the energy we produce is lost as waste heat — it just evaporates into the environment. On a global scale, this adds up to a huge amount of energy we’re throwing away. Thermoelectrics could harness this waste heat.” Maassen’s goal is to improve the efficiency of the energy conversion from thermal to electrical, so this technology can become more widespread. But that requires optimizing how the electrons and heat flow through these materials. “Heat corresponds to the vibrations of the atoms that make up the material — just like waves, the collective motion of the atoms carries thermal energy from one location to another,” Maassen says. “Since we need to resolve things on the atomic scale, our electron and thermal calculations are based on quantum mechanics simulations. This cutting-edge modeling also helps us identify or design materials with exceptional properties even if they don’t yet exist. This can guide experimental researchers towards new discoveries.” In addition to helping reduce global energy consumption, he’d like to improve the speed of computer processors. “The circuits driving our phones and computers are made from billions of tiny electronic devices,” he says. “They’ve been getting smaller, and are now below 10 nanometers. When an electrical current flows through these tiny devices, it generates heat, however heat doesn’t dissipate efficiently in such small structures because the physics are different. This results in higher temperatures that can prematurely burn out the circuit.” It’s a major challenge for the semiconductor industry and the main reason the speed of processors stopped increasing over a decade ago. “Understanding and controlling thermal generation and flow on the nanoscale could have an impact on information technology,” he says. “These insights can help us design new electronics with reduced heating that would run faster and more efficiently.” He uses simulations to gain insights into what controls electron and heat flow in existing and new materials. He does these calculations using ACENET’s super-computers. “Without good computing resources, we wouldn’t be able to make these calculations, and these insights that we’re getting would evaporate,” he says. Even with access to high-powered computing resources, the calculations take a long time. ACENET’s resources played a role in his return to Canada from the U.S. “I knew life would be easier having ACENET available to me,” he says. “The very tough calculations we do can take weeks, but without all these resources, we just wouldn’t do them.”
Showcase Tag: Nanometre-scale
Exploring the World of Nanoparticles
The world that Martin Mkandawire studies is very, very small, but his work could have a massive impact on human health and the treatment of diseases, including cancer. He’s also playing a significant role in helping to clean up the environment, particularly around mining and industrial sites. Mkandawire is a chemistry professor and scientist at Cape Breton University (CBU) who uses spectroscopy and photochemistry to study the properties of nanoparticles – microscopic objects less than 100 nanometres in diameter. He studies organometallic compounds and interactions between molecules and nanoparticles that have at least one bond between an atom of an organic compound and a metal. He’s also working to develop devices using natural biological processes as the model, including developing and improving efficiency of organic solar cells based on cyanobacterial photosynthesis. As Industrial Research Chair for Mine Water Management at the Verschuren Centre for Sustainability in Energy and the Environment at CBU, Mkandawire devotes much of his research to mine water remediation and management, developing cost-effective cleanup and treatment strategies, mostly based on principles of nanotechnology. One of those strategies involves using sensors that contain protein bound to nanoparticles that change colour, or fluoresce, when they come in contact with certain pollutants – acting as chemical canaries in coal mines. “We’re using nanoparticles for biosensor development,” he says. Mkandawire and his team are also using nanotechnology to make cancer radiation treatments safer and more effective. Amanda Cameron is an undergraduate chemistry student at CBU and the recipient of a 2015 ACENET Research Fellowship. She is also one of the authors of a landmark paper on gold nanoparticle absorption rates published in the Royal Chemical Society journal Nanoscale. Under Mkandawire’s direction she is studying the interaction of nanoparticles with certain cancer drugs. “Right now there are a lot of negative side effects associated with some cancer drugs,” says Cameron. “If we attach those drugs to a nanoparticle that targets the cancer cells we can better target the tumour without affecting the healthy cells around it.” By injecting metallic nanoparticles directly inside cancer cells, small doses of radiation can be highly targeted to kill cancer cells without harming the healthy cells around it. “With this technique, a small amount of radiation has a strong effect,” says Mkandawire. His team also worked on targeting nanoparticles at the mitochondria in cancer cells – a study they published in the Royal Chemical Society journal, Nanoscale. Nanotechnology research may also lead to major improvements in one of the world’s oldest medical treatments: wound dressings. Mkandawire is testing smart wound dressings that contain magnetic nanoparticles incorporated in wound dressing fibres capable of detecting bacteria and increasing conditions during wound healing such as temperature or pH – conditions that can kill the bacteria without the need for antibiotics or other drugs. “Right now you have to keep undressing the wound and checking for infections,” says Mkandawire. “Smart dressings would allow you to keep the dressing on without disturbing the wound and still be well protected from the possibility of infection.” To carry out his studies Mkandawire uses the ACENET computer network to run complex algorithms before he puts his theories to laboratory testing. “We can enter in parameters like thermodynamic properties, reaction rates, the energy of interaction, type of interaction, and strength of the molecular bonding. It allows us to analyze what will occur over time. They are extremely complex calculations and they take a long time to run on the computer. ACENET speeds up the process and allows us to do a lot more in the limited time we have. It’s a great resource.”
Making Molecules Dance
It’s a revolutionary idea – a technique that could change the design of nuclear power plants. Mount Allison University scientist Khashayar Ghandi is experimenting with the possibility of converting nuclear radiation directly into electricity using gold nanoparticles that act as a sponge to soak up electrons. Currently nuclear reactors create electricity by heating steam to drive large dynamos. The conversion process Ghandi envisions would eliminate the steps required to convert the energy to thermal and then mechanical energy – increasing efficiency and decreasing costs. Ghandi is an associate professor in chemistry & biochemistry and an associate of the physics department at Mount Allison. His research focuses on sustainable and environmentally friendly energy production methods, and chemical processes for industry. He is working with Atomic Energy of Canada Limited to study radiation produced in nuclear reactors, and with the Atomic Energy of France (a country that produces 75% of its electricity from nuclear power) to understand more about the safe storage of nuclear waste. Ghandi and his team are also working on other green energy solutions, including the development of a process to use sunlight to create hydrogen – a potential storage system for solar energy that would make solar a practical main energy source even when the sun isn’t shining. Other projects include the development of nuclear shields that could lead to more effective radiation treatments for cancer. Ghandi is also experimenting with using specialized clay materials to compress atoms and molecules from three dimensions down to two – a process that has the potential of changing the properties of substances at a molecular level. “If you think about carbon atoms, a diamond is made of carbon atoms spread out into three dimensions,” he says. “Graphite has the same atom in two dimensions.” Because of the complexity of his work, Ghandi and his team often travel to facilities such as TRIUMF national laboratory in Vancouver, ISIS at the Rutherford Appleton Laboratory in the UK and JPARC in Japan to use particle accelerators, pulsed muon sources and other advanced technology. But much of his experimental work is conducted at Mount Allison, often requiring elaborate computer simulations, scientific mechanical design that also need computer design and simulations, spectroscopic and quantum mechanical simulations. Ghandi was one of the first users of the ACENET computer network, joining the ACENET program shortly after it began. “ACENET is a very important resource for us and provides my research students with great opportunities,” he says. The computational power of the ACENET system allows Ghandi to construct elaborate chemical reaction models and test them mathematically before subjecting his ideas to real world testing in the lab. “We’re dealing with lots of data and we have to do some heavy data crunching,” he says. “By doing it this way it helps us to understand the chemistry that’s at work and allows us to make predictions of how reactions are going to behave. That way we can design new materials to perform certain functions before we go to the lab. I always like to have some intuition and a mathematical model before I start.” Ghandi says his work is motivated by the need to develop cost-effective green energy systems, but another passion drives him as well. “The other works we do don’t have a practical application at all,” he says. “We do it for pure imagination. To increase our fundamental understanding of the way atoms and molecules behave. To watch them dance and to understand how this dance led to new physics and chemistry.”
Why Materials Do the Things They Do
Dr. Geoffrey Lee-Dadswell is a theoretical physicist at Cape Breton University, who for the past 15 years has been studying why materials do the things they do. Specifically, he studies heat and momentum transport on a very small scale. For an example of large scale heat transport, take a frying pan on a stove. We know that the stove element heats the bottom of a pan to the point that food cooks. However, the handle of the pan doesn’t get as hot. Why? The answer lies in understanding the transport of heat, which obeys Fourier’s Law of Heat Conduction. This law has been known for almost 200 years, but surprisingly, is not well understood. One of the mysteries about Fourier’s Law is that it doesn’t seem to work for some objects on the nanometre-scale. A nanometre is one billionth of a metre. If you were to lay atoms across a nanometre, you might fit only about 10! Computers for example have become faster largely because the parts of their chips have been made smaller over the years. As this process continues, more and more parts of an ordinary desktop computer or smart phone are nano-electronics. Lee-Dadswell studies nano-systems that are one-dimensional, which is to say that for theoretical purposes, they have only length. Now because we live in a three-dimensional world, everything has a width and a depth. However, in some nano-systems, these are so small that they can be ignored. Examples of one-dimensional systems are carbon nano-tubes (think of these like a sheet of graphite that’s been rolled up into a tube) and polymer chains such as the polyethylene chains that pop bottles are made of. Carbon nano-tubes are often a few micrometres long, but can be only five to ten nanometres wide. Physicists once believed that everything obeyed Fourier’s Law of Heat Conduction, but researchers have found that these one-dimensional systems behave differently from other systems –disobeying Fourier’s Law. Moreover, they don’t know why, which also means that they don’t have a solid understanding of why everything else does obey Fourier’s Law. Physical laws are preferably derived from the more fundamental mechanics, but nobody knows how to derive Fourier’s Law from mechanics. If they can’t derive it, then they really don’t understand the law. This drives physicists nuts! It means that we don’t understand things like heat flow as well as we thought. This puzzle began to surface in the early 1900s, but didn’t come to the forefront until the 1970s. It’s challenging to make progress on such a long-standing mystery, and tackling it is therefore rather scary. Lee-Dadswell is one of only a few researchers in the world doing so. Lee-Dadswell generally has one or two undergraduate students working with him. He develops models, and the students then run dozens of simulations in parallel on ACENET systems, each running for possibly weeks and involving tens or hundreds of thousands of atoms interacting with each other. By understanding the fundamental laws of transport, solving problems such as removing heat from nano-electronics and improving refrigeration technology become possible.
Using Computers to Make Better Computers
About 500 GB of data are created around the world every second, with the total amount of data doubling every two years. Approximately 600 million hard drives were sold last year to contain this data, creating $32 billion in revenue for the industry, with all of that information stored on a disc smaller than a compact disc through the marvels of nano-magnets. But don’t expect this to continue. The laws of physics are being pushed to their limit in the quest for ever decreasing bit size. The industry is looking to fundamental research to provide a roadmap to guide the development of the next generation of magnetic hard drives. At the leading edge of this research are Profs. Martin Plumer and John Whitehead in the Department of Physics and Physical Oceanography, currently in their fourth year of a collaborative research agreement with Western Digital Corporation, near San Francisco, Calif., in a project that uses numerical simulations to study the stability of data stored with ever-smaller bits. “The driver of all this cheap storage is called areal density (AD), which is how many bits you can store on a square inch of a disc,” said Dr. Plumer. “AD has increased 100 million times over the past 50 years, and for a few years in the early 2000s, the annual growth rate in AD was 100 per cent. Today it is down to about 20 per cent. To sustain even a modest growth in AD over the next decade, manufacturers will need to bring new technologies to market in a relatively short time frame, and cheaply.” He explains that while the capacity of a typical disc drive has increased exponentially with time, its price has remained relatively constant because of the fierce competition between manufacturers. However, these price wars have taken their toll. “Fifteen years ago there were eight or so such companies in the U.S.,” he said. “Today, only arch rivals Western Digital and Seagate remain and neither company can afford to let the other take the technology lead. The blistering pace of the time-to-market for these new technologies is therefore critical to staying competitive. Keeping ahead in fundamental research is essential.” The main problem with increasing AD is that it affects the stability of the stored information and limits the increases in AD. The stability problem arises because to form a bit, all the tiny nano-magnets must be aligned in the same direction. “Unfortunately, the nano-magnets would rather align in opposite directions,” said Dr. Whitehead. “Just try holding two refrigerator magnets next to each other the wrong way. Fluctuations of the nano-magnets due to thermal agitation can cause random flips that degrade the bit pattern. Even at room temperature there is enough thermal energy to potentially flip a nano-magnet in a bit. “Over time, more and more nano-magnets flip their direction and the stored information is non-recoverable. For higher AD, you need smaller bits and smaller nano-magnets, which are easier to flip — that’s called superparamagnetism. Ten years ago, hard drives had a typical warranty period of five years. Now you are lucky to get a commitment that your thesis — or photos, or music — stored on your hard drive will still be there three years later, and it’s all because of superparamagnetism.” The researchers’ computer simulations relate the stability of the nano-magnets in a bit pattern to the basic material properties of the thin magnetic films that make up a hard disc. Together with their postdoctoral scholar, Dr. Tim Fal, their part-time research assistant and PhD student Jason Mercer and Dr. Johannes van Ek, their principal collaborator at Western Digital, the professors solve time-dependent equations for interacting nano-magnets or “micromagnetics” that include the effects of thermal fluctuations. “This is not an easy problem and we need the full power of the hundreds of processors available from the Atlantic Computational Excellence Network to get meaningful results,” said Dr. Plumer. “Both Western Digital and Seagate recognize the importance of fundamental research and of funding university collaborations. Our collaborative research agreement with Western Digital supports the development of numerical models that can be used to guide targeted research in materials science to sustain the continued increase in AD over the next decade. It has also brought over US$180,000 into the local economy by providing salaries for post-doctoral scholars and students.” Dr. Plumer adds the collaboration has been a lot of fun. “We get to do the type of research that we love with the added benefit that industry is interested enough to help pay for it,” he said. “It is also a way for our students and post-docs to get exposure to real-world problems and to see first-hand how fundamental science makes an impact. They get to present their results at applied magnetism conferences, interact with industry researchers, and also visit the research and manufacturing sites of Western Digital. In fact, the training in our group has even led to one of our former post-docs landing a permanent position at Seagate in Minneapolis.”