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Monday, 18 February 2013

Erik Schlangen: A "self-healing" asphalt

Feb 18, 2013

Paved roads are nice to look at, but they’re easily damaged and costly to repair. Erik Schlangen demos a new type of porous asphalt made of simple materials with an astonishing feature: When cracked, it can be “healed” by induction heating.

Source: TED
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Miguel Nicolelis: A monkey that controls a robot with its thoughts. No, really.

Feb 18, 2013

Can we use our brains to directly control machines -- without requiring a body as the middleman? Miguel Nicolelis talks through an astonishing experiment, in which a clever monkey in the US learns to control a monkey avatar, and then a robot arm in Japan, purely with its thoughts. The research has big implications for quadraplegic people -- and maybe for all of us.

Source: TED

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Friday, 15 February 2013

New carbon films improve prospects of solar energy devices

Feb 15, 2013
Abstract Image
New research by Yale University scientists helps pave the way for the next generation of solar cells, a renewable energy technology that directly converts solar energy into electricity. (Illustration by the researchers)
New research by Yale University scientists helps pave the way for the next generation of solar cells, a renewable energy technology that directly converts solar energy into electricity.

In a pair of recent papers, Yale engineers report a novel and cost-effective way to improve the efficiency of crystalline silicon solar cells through the application of thin, smooth carbon nanotube films. These films could be used to produce hybrid carbon/silicon solar cells with far greater power-conversion efficiency than reported in this system to date.

“Our approach bridges the cost-effectiveness and excellent electrical and optical properties of novel nanomaterials with well-established, high efficiency silicon solar cell technologies,” said André D. Taylor, assistant professor of chemical and environmental engineering at Yale and a principal investigator of the research.

The researchers reported their work in two papers published in December, one in the journal Energy and Environmental Science and one in Nano Letters (Record High Efficiency Single-Walled Carbon Nanotube/Silicon p–n Junction Solar Cells). Mark A. Reed, a professor of electrical engineering and applied physics at Yale, is also a principal investigator.

Silicon, an abundant element, is an ideal material for solar cells because its optical properties make it an intrinsically efficient energy converter. But the high cost of processing single-crystalline silicon at necessarily high temperatures has hindered widespread commercialization.

Organic solar cells — an existing alternative to high-cost crystalline silicon solar cells — allow for simpler, room-temperature processing and lower costs, researchers said, but they have low power-conversion efficiency.

Instead of using only organic substitutes, the Yale team applied thin, smooth carbon nanotube films with superior conductance and optical properties to the surface of single crystalline silicon to create a hybrid solar cell architecture. To do it, they developed a method called superacid sliding.

As reported in the papers, the approach allows them to take advantage of the desirable photovoltaic properties of single-crystalline silicon through a simpler, low-temperature, lower-cost process. It allows for both high light absorption and high electrical conductivity.

“This is striking, as it suggests that the superior photovoltaic properties of single-crystalline silicon can be realized by a simple, low-temperature process,” said Xiaokai Li, a doctoral student in Taylor’s lab and a lead author on both papers. “The secret lies in the arrangement and assembly of these carbon nanotube thin films,”

In previous work, Yale scientist successfully developed a carbon nanotube composite thin film that could be used in fuel cells and lithium ion batteries. The recent research suggests how to extend the film’s application to solar cells by optimizing its smoothness and durability.

“Optimizing this interface could also serve as a platform for many next-generation solar cell devices, including carbon nanotube/polymer, carbon/polymer, and all carbon solar cells,” said Yeonwoong (Eric) Jung, a postdoctoral researcher in Reed’s lab and also a lead author of the papers.

All authors are listed on the papers (links above).

The National Science Foundation, NASA, the U.S. Department of Energy, and the Yale Institute for Nanoscience and Quantum Engineering provided support for the research.

Source: Yale University

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Forget about leprechauns, engineers are catching rainbows

Feb 15, 2012

An image of the “hyperbolic metamaterial waveguide,” which catches an ultimately absorbs wavelengths (or color) in a vertical direction.
An up-close look at the “hyperbolic metamaterial waveguide,” which catches and ultimately absorbs wavelengths (or color) in a vertical direction.

University at Buffalo engineers have created a more efficient way to catch rainbows, an advancement in photonics that could lead to technological breakthroughs in solar energy, stealth technology and other areas of research.

Qiaoqiang Gan, PhD, an assistant professor of electrical engineering at UB, and a team of graduate students described their work in a paper called “Rainbow Trapping in Hyperbolic Metamaterial Waveguide,” published in the online journal Scientific Reports.

They developed a “hyperbolic metamaterial waveguide,” which is essentially an advanced microchip made of alternate ultra-thin films of metal and semiconductors and/or insulators. The waveguide halts and ultimately absorbs each frequency of light, at slightly different places in a vertical direction (see the above figure), to catch a “rainbow” of wavelengths.

Gan is a researcher within UB’s new Center of Excellence in Materials Informatics.

“Electromagnetic absorbers have been studied for many years, especially for military radar systems,” Gan said. “Right now, researchers are developing compact light absorbers based on optically thick semiconductors or carbon nanotubes. However, it is still challenging to realize the perfect absorber in ultra-thin films with tunable absorption band.

“We are developing ultra-thin films that will slow the light and therefore allow much more efficient absorption, which will address the long existing challenge.”

Light is made of photons that, because they move extremely fast (i.e., at the speed of light), are difficult to tame. In their initial attempts to slow light, researchers relied upon cryogenic gases. But because cryogenic gases are very cold – roughly 240 degrees below zero Fahrenheit – they are difficult to work with outside a laboratory.

Before joining UB, Gan helped pioneer a way to slow light without cryogenic gases. He and other researchers at Lehigh University made nano-scale-sized grooves in metallic surfaces at different depths, a process that altered the optical properties of the metal. While the grooves worked, they had limitations. For example, the energy of the incident light cannot be transferred onto the metal surface efficiently, which hampered its use for practical applications, Gan said.

The hyperbolic metamaterial waveguide solves that problem because it is a large area of patterned film that can collect the incident light efficiently. It is referred to as an artificial medium with subwavelength features whose frequency surface is hyperboloid, which allows it to capture a wide range of wavelengths in different frequencies including visible, near-infrared, mid-infrared, terahertz and microwaves.

It could lead to advancements in an array of fields.

For example, in electronics there is a phenomenon known as crosstalk, in which a signal transmitted on one circuit or channel creates an undesired effect in another circuit or channel. The on-chip absorber could potentially prevent this.

The on-chip absorber may also be applied to solar panels and other energy-harvesting devices. It could be especially useful in mid-infrared spectral regions as thermal absorber for devices that recycle heat after sundown, Gan said.

Technology such as the Stealth bomber involves materials that make planes, ships and other devices invisible to radar, infrared, sonar and other detection methods. Because the on-chip absorber has the potential to absorb different wavelengths at a multitude of frequencies, it could be useful as a stealth coating material.

Additional authors of the paper include Haifeng Hu, Dengxin Ji, Xie Zeng and Kai Liu, all PhD candidates in UB’s Department of Electrical Engineering. The work was sponsored by the National Science Foundation and UB’s electrical engineering department.

Source:  University of Buffalo

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Tuesday, 12 February 2013

Stem cell breakthrough could lead to new bone repair therapies on nanoscale surfaces

Feb 12, 2013

Stem cell breakthrough could lead to new bone repair therapies

Scientists at the University of Southampton have created a new method to generate bone cells which could lead to revolutionary bone repair therapies for people with bone fractures or those who need hip replacement surgery due to osteoporosis and osteoarthritis.

The research, carried out by Dr Emmajayne Kingham at the University of Southampton in collaboration with the University of Glasgow and published in the journal Small, cultured human embryonic stem cells on to the surface of plastic materials and assessed their ability to change.

Scientists were able to use the nanotopographical patterns on the biomedical plastic to manipulate human embryonic stem cells towards bone cells. This was done without any chemical enhancement.

The materials, including the biomedical implantable material polycarbonate plastic, which is a versatile plastic used in things from bullet proof windows to CDs, offer an accessible and cheaper way of culturing human embryonic stem cells and presents new opportunities for future medical research in this area.

Professor Richard Oreffo, who led the University of Southampton team, explains: “To generate bone cells for regenerative medicine and further medical research remains a significant challenge. However we have found that by harnessing surface technologies that allow the generation and ultimately scale up of human embryonic stem cells to skeletal cells, we can aid the tissue engineering process. This is very exciting.

“Our research may offer a whole new approach to skeletal regenerative medicine. The use of nanotopographical patterns could enable new cell culture designs, new device designs, and could herald the development of new bone repair therapies as well as further human stem cell research,” Professor Oreffo adds.

The study was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

This latest discovery expands on the close collaborative work previously undertaken by the University of Southampton and the University of Glasgow. In 2011 the team successfully used plastic with embossed nanopatterns to grow and spread adult stem cells while keeping their stem cell characteristics; a process which is cheaper and easier to manufacture than previous ways of working.

Dr Nikolaj Gadegaard, Institute of Molecular, Cell and Systems Biology at the University of Glasgow, says: "Our previous collaborative research showed exciting new ways to control mesenchymal stem cell – stem cells from the bone marrow of adults – growth and differentiation on nanoscale patterns.

“This new Southampton-led discovery shows a totally different stem cell source, embryonic, also respond in a similar manner and this really starts to open this new field of discovery up. With more research impetus, it gives us the hope that we can go on to target a wider variety of degenerative conditions than we originally aspired to. This result is of fundamental significance."

Source: University of Southampton

Monday, 11 February 2013

Humans and robots work better together following cross-training

Feb 11, 2013

Julie Shah, assistant professor of aeronautics and astronautics and head of the Interactive Robotics Group at MIT

Spending a day in someone else’s shoes can help us to learn what makes them tick. Now the same approach is being used to develop a better understanding between humans and robots, to enable them to work together as a team.

Robots are increasingly being used in the manufacturing industry to perform tasks that bring them into closer contact with humans. But while a great deal of work is being done to ensure robots and humans can operate safely side-by-side, more effort is needed to make robots smart enough to work effectively with people, says Julie Shah, an assistant professor of aeronautics and astronautics at MIT and head of the Interactive Robotics Group in the Computer Science and Artificial Intelligence Laboratory (CSAIL).

“People aren’t robots, they don’t do things the same way every single time,” Shah says. “And so there is a mismatch between the way we program robots to perform tasks in exactly the same way each time and what we need them to do if they are going to work in concert with people.”

Most existing research into making robots better team players is based on the concept of interactive reward, in which a human trainer gives a positive or negative response each time a robot performs a task.

However, human studies carried out by the military have shown that simply telling people they have done well or badly at a task is a very inefficient method of encouraging them to work well as a team.

So Shah and PhD student Stefanos Nikolaidis began to investigate whether techniques that have been shown to work well in training people could also be applied to mixed teams of humans and robots. One such technique, known as cross-training, sees team members swap roles with each other on given days. “This allows people to form a better idea of how their role affects their partner and how their partner’s role affects them,” Shah says.

In a paper to be presented at the International Conference on Human-Robot Interaction in Tokyo in March, Shah and Nikolaidis will present the results of experiments they carried out with a mixed group of humans and robots, demonstrating that cross-training is an extremely effective team-building tool.

To allow robots to take part in the cross-training experiments, the pair first had to design a new algorithm to allow the devices to learn from their role-swapping experiences. So they modified existing reinforcement-learning algorithms to allow the robots to take in not only information from positive and negative rewards, but also information gained through demonstration. In this way, by watching their human counterparts switch roles to carry out their work, the robots were able to learn how the humans wanted them to perform the same task.

Each human-robot team then carried out a simulated task in a virtual environment, with half of the teams using the conventional interactive reward approach, and half using the cross-training technique of switching roles halfway through the session. Once the teams had completed this virtual training session, they were asked to carry out the task in the real world, but this time sticking to their own designated roles.

Shah and Nikolaidis found that the period in which human and robot were working at the same time — known as concurrent motion — increased by 71 percent in teams that had taken part in cross-training, compared to the interactive reward teams. They also found that the amount of time the humans spent doing nothing — while waiting for the robot to complete a stage of the task, for example — decreased by 41 percent.

What’s more, when the pair studied the robots themselves, they found that the learning algorithms recorded a much lower level of uncertainty about what their human teammate was likely to do next — a measure known as the entropy level — if they had been through cross-training.

Finally, when responding to a questionnaire after the experiment, human participants in cross-training were far more likely to say the robot had carried out the task according to their preferences than those in the reward-only group, and reported greater levels of trust in their robotic teammate. “This is the first evidence that human-robot teamwork is improved when a human and robot train together by switching roles, in a manner similar to effective human team training practices,” Nikolaidis says.

Shah believes this improvement in team performance could be due to the greater involvement of both parties in the cross-training process. “When the person trains the robot through reward it is one-way: The person says ‘good robot’ or the person says ‘bad robot,’ and it’s a very one-way passage of information,” Shah says. “But when you switch roles the person is better able to adapt to the robot’s capabilities and learn what it is likely to do, and so we think that it is adaptation on the person’s side that results in a better team performance.”

The work shows that strategies that are successful in improving interaction among humans can often do the same for humans and robots, says Kerstin Dautenhahn, a professor of artificial intelligence at the University of Hertfordshire in the U.K. “People easily attribute human characteristics to a robot and treat it socially, so it is not entirely surprising that this transfer from the human-human domain to the human-robot domain not only made the teamwork more efficient, but also enhanced the experience for the participants, in terms of trusting the robot,” Dautenhahn says.

Source: MIT

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Quality control at the point of a finger

Feb 11, 2013

A point of the finger is all it takes to send the defect in the paint to the QS inspection system, store it and document it.
© Fraunhofer IOSB

For production operations, quality assurance over the process chain is indispensable: it is the only way to detect problems at an early stage and lower additional costs. Fraunhofer researchers developed an efficient type of quality control: With a pointing gesture, employees can input any detected defects to car body parts into the inspection system, and document them there. The non-contact gesture-detection process will be on display at the 2013 Hannover Messe from 8 to 12 April.

With utter meticulousness, the quality control inspector examines a car bumper for defects in the paint work – ultimately, only impeccable body parts get sent to final assembly. If he finds a defect in the paint, just a point of the finger is all it takes to send the defect to the QS inspection system, store it and document it. The employee obtains visual feedback through a monitor that displays a 3D reconstruction of the bumper. At first glance, it might seem completely futuristic, though soon enough, it could become an everyday part of quality assurance: Researchers at the Fraunhofer Institute for Optronics, System Technologies and Image Exploitation IOSB in Karlsruhe engineered the intelligent gesture control system on behalf of the BMW Group. In the future, it should supersede today’s time-consuming test procedures. “Previously, the inspector had to note all defects that were detected, leave his workstation, go to the PC terminal, operate multiple input screens and then label the position of the defect and the defect type. That approach is laborious, time-intensive and prone to error,” asserts Alexander Schick, scientist at IOSB. The gesture control system, by contrast, improves the inspector’s working conditions considerably, and triggering substantial time savings – the employee can remain at his workstation and interact directly with the test object. “If the bumper is fine, then he swipes over it from left to right. In the event of damage, he points to the location of the defect,” says Schick.

3D tracking records people and objects in real time

This non-contact gesture-detection system is based on 3D data. Hence, the entire workstation must first be reconstructed in 3D. That includes the individual as well as the object with which he is working. “What does the inspector look like? Where is he situated? How does he move? What is he doing? Where is the object? – all of these data are required so that the pointing gesture can properly link to the bumper,” ex-
plains the researcher. In order to enable gesture control, the experts apply 3D-body tracking, which records the individual’s posture in real time. Even the car body parts are “tracked.” When it comes to this, the hardware requirements are minimal: A standard PC and two Microsoft Kinect systems – consisting of camera and 3D sensors – suffice in order to realize the reconstruction. Schick and his team developed the corresponding algorithms, which fuse multiple 2D and 3D images together, specifically for this kind of application, and adapted them to the standards of the BMW Group.

“The breeding ground for this technology is our Smart Control Room, where people can interact with the room quite naturally. They can use pointing gestures to operate remote displays – without any additional equipment. The room recognizes what actions are taking place at that moment, and offers the appropriate information and tools. Since gesture detection does not depend on display screens, this means we can im-
plement applications that use no monitors, like the gesture interaction here with real objects,” explains Schick. “It makes no difference what kind of object we are dealing with. Instead of a bumper, we could also track a different part.”

The technology can be subsequently integrated into existing production systems at little expense. Scientists could incorporate their effective process into the BMW Group’s system through a specialized interface module. The gesture detection system will be presented at the 2013 Hannover Messe, from 8 to 12 April, at the Fraunhofer joint exhibition booth in Hall 2, Booth D18.

Plans call for the installation of a prototype model at the BMW plant in Landshut in January 2013. Working in cooperation with quality control inspectors, the system will be fine-tuned onsite before it gets deployed to production in the future.

Source: Fraunhofer-Gesellschaft

Implants make light work of fixing broken bones

Feb 11, 2013

Richard Oreffo

Artificial bone, created using stem cells and a new lightweight plastic, could soon be used to heal shattered limbs.

The use of bone stem cells combined with a degradable rigid material that inserts into broken bones and encourages real bone to re-grow has been developed at the Universities of Edinburgh and Southampton.

Researchers have developed the material with a honeycomb scaffold structure that allows blood to flow through it, enabling stem cells from the patient’s bone marrow to attach to the material and grow new bone. Over time, the plastic slowly degrades as the implant is replaced by newly grown bone.

Scientists developed the material by blending three types of plastics. They used a pioneering technique to blend and test hundreds of combinations of plastics, to identify a blend that was robust, lightweight, and able to support bone stem cells. Successful results have been shown in the lab and in animal testing with the focus now moving towards human clinical evaluation.

The study, published in the journal Advanced Functional Materials, was funded by the Biotechnology and Biological Sciences Research Council.

This new discovery is the result of a seven-year partnership between the University of Southampton and the University of Edinburgh.

Richard Oreffo, Professor of Musculoskeletal Science at the University of Southampton, comments: "Fractures and bone loss due to trauma or disease are a significant clinical and socioeconomic problem. This collaboration between chemistry and medicine has identified unique candidate materials that support human bone stem cell growth and allow bone formation. Our collaborative strategy offers significant therapeutic implications."

Professor Mark Bradley, of the University of Edinburgh’s School of Chemistry, adds: “We were able to make and look at a hundreds of candidate materials and rapidly whittle these down to one which is strong enough to replace bone and is also a suitable surface upon which to grow new bone.

“We are confident that this material could soon be helping to improve the quality of life for patients with severe bone injuries, and will help maintain the health of an ageing population.”

Source:  University of Southampton

Wednesday, 16 January 2013

John Maeda: How art, technology and design inform creative leaders

Jan 16, 2013

John Maeda, President of the Rhode Island School of Design, delivers a funny and charming talk that spans a lifetime of work in art, design and technology, concluding with a picture of creative leadership in the future. Watch for demos of Maeda’s earliest work -- and even a computer made of people.

 John Maeda is the president of the Rhode Island School of Design, where he is dedicated to linking design and technology. Through the software tools, web pages and books he creates, he spreads his philosophy of elegant simplicity.

Source: TED

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Engineer making rechargeable batteries with layered nanomaterials

Jan 16, 2013

We study the process of graphene growth on Cu and Ni substrates subjected to rapid heating (approximately 8 °C/s) and cooling cycles (approximately 10 °C/s) in a modified atmospheric pressure chemical vapor deposition furnace. Electron microscopy followed by Raman spectroscopy demonstrated successful synthesis of large-area few-layer graphene (FLG) films on both Cu and Ni substrates. The overall synthesis time was less than 30 min. Further, the as-synthesized films were directly utilized as anode material and their electrochemical behavior was studied in a lithium half-cell configuration. FLG on Cu (Cu-G) showed reduced lithium-intercalation capacity when compared with SLG, BLG and Bare-Cu suggesting its substrate protective nature (barrier to Li-ions). Although graphene films on Ni (Ni-G) showed better Li-cycling ability similar to that of other carbons suggesting that the presence of graphene edge planes (typical of Ni-G) is important in effective uptake and release of Li-ions in these materials.  Source: ACS

A Kansas State University researcher is developing more efficient ways to save costs, time and energy when creating nanomaterials and lithium-ion batteries.

Gurpreet Singh, assistant professor of mechanical and nuclear engineering, and his research team have published two recent articles on newer, cheaper and faster methods for creating nanomaterials that can be used for lithium-ion batteries. In the past year, Singh has published eight articles -- five of which involve lithium-ion battery research.

"We are exploring new methods for quick and cost-effective synthesis of two-dimensional materials for rechargeable battery applications," Singh said. "We are interested in this research because understanding lithium interaction with single-, double- and multiple-layer-thick materials will eventually allow us to design battery electrodes for practical applications. This includes batteries that show improved capacity, efficiency and longer life."

For the latest research, Singh's team created graphene films that are between two and 10 layers thick. Graphene is an atom-thick sheet of carbon. The researchers grew the graphene films on copper and nickel foils by quickly heating them in a furnace in the presence of controlled amounts of argon, hydrogen and methane gases. The team has been able to create these films in less than 30 minutes. Their work appears in the January issue of ACS-Applied Materials and Interfaces in an article titled "Synthesis of graphene films by rapid heating and quenching at ambient pressures and their electrochemical characterization."

The research is significant because the researchers created these graphene sheets by quickly heating and cooling the copper and nickel substrates at atmospheric pressures, meaning that scientists no longer need a vacuum to create few-layer-thick graphene films and can save energy, time and cost, Singh said.

The researchers used these graphene films to create the negative electrode of a lithium-ion cell and then studied the charge and discharge characteristics of this rechargeable battery. They found the graphene films grown on copper did not cycle the lithium ions and the battery capacity was negligible. But graphene grown on nickel showed improved performance because it was able to store and release lithium ions more efficiently.

"We believe that this behavior occurs because sheets of graphene on nickel are relatively thick near the grain boundaries and stacked in a well-defined manner -- called Bernal Stacking -- which provides multiple sites for easy uptake and release of lithium ions as the battery is discharged and charged," Singh said.

In a second research project, the researchers created tungsten disulfide nanosheets that were approximately 10 layers thick. Starting with bulk tungsten disulfide powder -- which is a type of dry lubricant used in the automotive industry -- the team was able to separate atomic layer thick sheets of tungsten disulfide in a strong acid solution. This simple method made it possible to produce sheets in large quantities. Much like graphene, tungsten disulfide also has a layered atomic structure, but the individual layers are three atoms thick.

The researchers found that these acid-treated tungsten disulfide sheets could also store and release lithium ions but in a different way. The lithium is stored through a conversion reaction in which tungsten disulfide dissociates to form tungsten and lithium sulfide as the cell is discharged. Unlike graphene, this reaction involves the transfer of at least two electrons per tungsten atom. This is important because researchers have long disregarded such compounds as battery anodes because of the difficulty associated with adding lithium to these materials, Singh said. It is only recently that the conversion reaction-based battery anodes have gained popularity.

"We also realize that tungsten disulfideis a heavy compound compared to state-of-the-art graphite used in current lithium-ion batteries," Singh said. "Therefore tungsten disulfide may not be an ideal electrode material for portable batteries."

The research appeared in a recent issue of the Journal of Physical Chemistry Letters in an article titled "Synthesis of surface-functionalized WS2 nanosheets and performance as Li-ion battery anodes."

Both projects are important because they can help scientists create nanomaterials in a cost-effective way. While many studies have focused on making graphene using low-pressure chemical processes, little research has been tried using rapid heating and cooling at atmospheric pressures, Singh said. Similarly, large quantities of single-layer and multiple-layer thick sheets of tungsten disulfide are needed for other applications.

"Interestingly, for most applications that involve this kind of battery research and corrosion prevention, films that are a few atoms thick are usually sufficient," Singh said. "Very high quality large area single-atom-thick films are not a necessity."

Other Kansas State University researchers involved in the projects include Romil Bhandavat and Lamuel David, both doctoral students in mechanical engineering, India, and Saksham Pahwa, a visiting undergraduate student, India. The graphene research involved University of Michigan researchers, including Zhaohui Zhong, assistant professor of electrical engineering and computer science, andGirish Kulkarni, doctoral candidate in electrical engineering.

Singh's work has been supported by the National Institute of Standards and Technology and the Kansas National Science Foundation Experimental Program to Stimulate Competitive Research program.

Singh plans future research to study how these layered nanomaterials can create better electrodes in the form of heterostructures, which are essentially three-dimensional stacked structures involving alternating layers of graphene and tungsten or molybdenum disulfide.

Source:  Kansas State University

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Sunday, 13 January 2013

Peel-and-Stick Solar Cells: Devices could charge battery-powered products in the future

Jan 13, 2013

(a) As-fabricated TFSCs on the original Si/SiO2 wafer. (b) The TFSCs are peeled off from the Si/SiO2 wafer in a water bath at room temperature. (c) The peeled off TFSCs are attached to a target substrate with adhesive agents. (d) The temporary transfer holder is removed, and only the TFSCs are left on the target substrate. Credit: Nature

It may be possible soon to charge cell phones, change the tint on windows, or power small toys with peel-and-stick versions of solar cells, thanks to a partnership between Stanford University and the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).
A scientific paper, “Peel and Stick: Fabricating Thin Film Solar Cells on Universal Substrates,” appears in the online version of Scientific Reports, a subsidiary of the British scientific journal Nature.

Peel-and-stick, or water-assisted transfer printing (WTP), technologies were developed by the Stanford group and have been used before for nanowire based electronics, but the Stanford-NREL partnership has conducted the first successful demonstration using actual thin film solar cells, NREL principal scientist Qi Wang said.

The university and NREL showed that thin-film solar cells less than one-micron thick can be removed from a silicon substrate used for fabrication by dipping them in water at room temperature. Then, after exposure to heat of about 90°C for a few seconds, they can attach to almost any surface.

Wang met Stanford’s Xiaolin Zheng at a conference last year where Wang gave a talk about solar cells and Zheng talked about her peel-and-stick technology. Zheng realized that NREL had the type of solar cells needed for her peel-and-stick project.

NREL’s cells could be made easily on Stanford’s peel off substrate. NREL’s amorphous silicon cells were fabricated on nickel-coated Si/SiO2 wafers. A thermal release tape attached to the top of the solar cell serves as a temporary transfer holder. An optional transparent protection layer is spin-casted in between the thermal tape and the solar cell to prevent contamination when the device is dipped in water. The result is a thin strip much like a bumper sticker: the user can peel off the handler and apply the solar cell directly to a surface.

“It’s been a quite successful collaboration,” Wang said. “We were able to peel it off nicely and test the cell both before and after. We found almost no degradation in performance due to the peel-off.”

Zheng said the partnership with NREL is the key for this successful work. “NREL has years of experience with thin film solar cells that allowed us to build upon their success,” Zheng said. “Qi Wang and (NREL engineer) William Nemeth are very valuable and efficient collaborators.”

Zheng said cells can be mounted to almost any surface because almost no fabrication is required on the final carrier substrates.

The cells’ ability to adhere to a universal substrate is unusual; most thin-film cells must be affixed to a special substrate. The peel-and-stick approach allows the use of flexible polymer substrates and high processing temperatures. The resulting flexible, lightweight, and transparent devices then can be integrated onto curved surfaces such as military helmets and portable electronics, transistors and sensors.

In the future, the collaborators will test peel-and-stick cells that are processed at even higher temperatures and offer more power.

Source: National Renewable Energy Laboratory (NREL)

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Saturday, 12 January 2013

Smarter infrastructure: Converting vibrations into electricity

Jan 12, 2013

Credit: stopthegears, via Flickr creative commons

A team from the Centre for Smart Infrastructure and Construction have developed a mechanical amplifier to convert ambient vibrations into electricity more effectively, which could be used to power wireless sensors for monitoring the structural health of roads, bridges and tunnels.

Undetected structural problems in aging infrastructure can be disastrous, such as the recent incident in the busy Sasago tunnel west of Tokyo. Nine people were killed when huge chunks of concrete began to fall from the roof of the tunnel, starting a fire and trapping people in their vehicles. Thankfully, such incidents are rare, but the ability to determine when structural problems may become a threat to public safety is a major priority for government and industry.

The Centre for Smart Infrastructure and Construction (CSIC) was established in 2011 to develop and commercialise new technologies designed to make smart infrastructure possible, primarily through the development of new sensor and data management technologies, which will enable continuous monitoring of our roads, tunnels and bridges.

A new device designed by researchers in the CSIC could allow this type of observations by converting the vibration experienced by structures into electricity, in order to power small remote monitoring devices in locations where access is limited, such as inside a tunnel or underneath a bridge.

“Wireless sensors are one way to better look after infrastructure, and it’s something that industry is interested in doing, but batteries are always the sticking point,” says Professor Kenichi Soga, who designed the device with Dr Ashwin Seshia and Yu Jia, a PhD student in Dr Seshia’s group. “It’s not the cost of the batteries that is the issue; it’s the cost of human power to replace the batteries.”

Since the devices are self-powered, there is no need to have individuals change the batteries on a regular basis, thereby decreasing cost to industry while enabling continuous remote monitoring in order to detect problems at an early stage.

Self-powered battery-less devices are not an entirely new concept: other energy harvesting principles are used to power digital wristwatches and handheld torches. Existing devices based on vibrational energy harvesting suffer from two key technical limitations, however: low output power density, and the mismatch between the narrow operational frequency bandwidth of conventional energy harvesters and the wideband nature of vibrations experienced by bridges, tunnels and roads.

The device developed by the CSIC team addresses these issues by basing their harvester on a phenomenon known as parametric resonance. The energy harvesting device can be realised as a micro-electromechanical system (MEMS) device, consisting of a micro-cantilever structure and a transducer. When force is applied to the cantilever perpendicular to the length instead of transversely, parametric resonance can be achieved, generating more energy from the same amount of vibration.

The MEMS device provides the added advantage of using batch manufacturing principles common to the semiconductor industry, potentially enabling low-cost battery replacement, large-scale volume production and co-integration with sensors and interface electronics to realise truly autonomous smart sensor nodes: a challenge that the CSIC team are seeking to address in the context of developing innovative monitoring technologies for large-scale built infrastructure.

Prototype versions of MEMS and macro-scale devices based on these principles have demonstrated a significantly improved power output and a wider operational bandwidth relative to current state-of-the-art devices. Preliminary results on a MEMS prototype were presented at the PowerMEMS conference in Atlanta in December. The device is being commercialised by Cambridge Enterprise, the University’s technology transfer office.

In addition to applications in the construction industry, the device also has potential applications such as powering wearable medical devices or extending the life of batteries in mobile phones.

CSIC was established in 2011, and brings together researchers from the Department of Engineering, along with colleagues from the Department of Architecture, the Computer Laboratory, the Judge Business School and Cambridge Enterprise.

Source: University of Cambridge

How to treat heat like light: Using nanoparticle alloys allows heat to be focused or reflected just like electromagnetic waves

Jan 12, 2012

Thermal lattices, shown here, are one possible application of the newly developed thermocrystals. In these structures, where precisely spaced air gaps (dark circles) control the flow of heat, thermal energy can be "pinned" in place by defects introduced into the structure (colored areas). Illustration courtesy of Martin Maldovan

An MIT researcher has developed a technique that provides a new way of manipulating heat, allowing it to be controlled much as light waves can be manipulated by lenses and mirrors.

The approach relies on engineered materials consisting of nanostructured semiconductor alloy crystals. Heat is a vibration of matter — technically, a vibration of the atomic lattice of a material — just as sound is. Such vibrations can also be thought of as a stream of phonons — a kind of “virtual particle” that is analogous to the photons that carry light. The new approach is similar to recently developed photonic crystals that can control the passage of light, and phononic crystals that can do the same for sound.

The spacing of tiny gaps in these materials is tuned to match the wavelength of the heat phonons, explains Martin Maldovan, a research scientist in MIT’s Department of Materials Science and Engineering and author of a paper on the new findings published Jan. 11 in the journal Physical Review Letters.

“It’s a completely new way to manipulate heat,” Maldovan says. Heat differs from sound, he explains, in the frequency of its vibrations: Sound waves consist of lower frequencies (up to the kilohertz range, or thousands of vibrations per second), while heat arises from higher frequencies (in the terahertz range, or trillions of vibrations per second).

In order to apply the techniques already developed to manipulate sound, Maldovan’s first step was to reduce the frequency of the heat phonons, bringing it closer to the sound range. He describes this as “hypersonic heat.”

“Phonons for sound can travel for kilometers,” Maldovan says — which is why it’s possible to hear noises from very far away. “But phonons of heat only travel for nanometers [billionths of a meter]. That’s why you couldn’t hear heat even with ears responding to terahertz frequencies.”

Heat also spans a wide range of frequencies, he says, while sound spans a single frequency. So, to address that, Maldovan says, “the first thing we did is reduce the number of frequencies of heat, and we made them lower,” bringing these frequencies down into the boundary zone between heat and sound. Making alloys of silicon that incorporate nanoparticles of germanium in a particular size range accomplished this lowering of frequency, he says.

Reducing the range of frequencies was also accomplished by making a series of thin films of the material, so that scattering of phonons would take place at the boundaries. This ends up concentrating most of the heat phonons within a relatively narrow “window” of frequencies.

Following the application of these techniques, more than 40 percent of the total heat flow is concentrated within a hypersonic range of 100 to 300 gigahertz, and most of the phonons align in a narrow beam, instead of moving in every direction.

As a result, this beam of narrow-frequency phonons can be manipulated using phononic crystals similar to those developed to control sound phonons. Because these crystals are now being used to control heat instead, Maldovan refers to them as “thermocrystals,” a new category of materials.

These thermocrystals might have a wide range of applications, he suggests, including in improved thermoelectric devices, which convert differences of temperature into electricity. Such devices transmit electricity freely while strictly controlling the flow of heat — tasks that the thermocrystals could accomplish very effectively, Maldovan says.

Most conventional materials allow heat to travel in all directions, like ripples expanding outward from a pebble dropped in a pond; thermocrystals could instead produce the equivalent of those ripples only moving out in a single direction, Maldovan says. The crystals could also be used to create thermal diodes: materials in which heat can pass in one direction, but not in the reverse direction. Such a one-way heat flow could be useful in energy-efficient buildings in hot and cold climates.

Other variations of the material could be used to focus heat — much like focusing light with a lens — to concentrate it in a small area. Another intriguing possibility is thermal cloaking, Maldovan says: materials that prevent detection of heat, just as recently developed metamaterials can create “invisibility cloaks” to shield objects from detection by visible light or microwaves.

Rama Venkatasubramanian, senior research director at the Center for Solid State Energetics at RTI International in North Carolina, says this is “an interesting approach to control the various frequencies of the phonon spectra that conduct heat in a solid-state material.”

The modeling used to develop this new system “needs to be further developed,” Venkatasubramanian adds. “The theory of what wavelengths of phonons, and at what temperatures, contribute to how much heat transport is a complex problem even in simpler materials, let alone nanostructured materials, and these will have to be factored in — so this paper will trigger more interest and study in that direction.”

Source: MIT

Good vibrations: Scientists recently developed a new microvibration excitation device

Jan 12, 2013

NPL scientists recently developed a new microvibration excitation device, which is currently under test at the European Space Agency (ESA) space test centre at ESTEC in Noordwijk, Holland.

The NPL excitation unit mounted on the ESA
Reaction Wheel Characterization Facility
The 'little shaker' device was produced as part of a technology research project for ESA to develop a prototype universal reference excitation unit which can be used to validate the performance of all kind of microvibration test facilities, traceable to ISO17025 levels of confidence and which can be deployed to perform inter facility comparison measurements.

The device is about the size of a shoe-box and generates small forces and torques (µN/µNm to single digit N/Nm range) at relatively low frequency (0.05 Hz to 10 Hz) in a controlled manner via reaction force against a moving mass. It can create force and torque along or about a single axis, and be repositioned in any orientation, to allow six-degree-of-freedom forces to be generated. The device is unique because there are currently no comparable means of producing highly repeatable forces and torques of this low magnitude in such a small, compact and portable mechanism.

Testing at the ESTEC space test center involved placing the device on Reaction Wheel Characterization Facility platform, activating it to create sinusoidal forces and moments in various orientations, and comparing the generated forces with those measured by the ESTEC facility.

Preliminary results are excellent and ESA now has a prototype device it can take to other facilities that will produce an identical drive signal, to allow comparisons of measurement results between facilities.

NPL was a natural partner for ESA on this project due to previous successful collaborations with challenging micro-thrust measurements. Additionally, NPL's role as the UK's National Measurement Institute provides confidence and experience in measurements traceable to primary standards and will be critical in allowing ESA to accredit their microvibration facility to the ISO 17025 standard in the future.

Source: NPL

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Monday, 7 January 2013

Ford 1.0-Liter EcoBoost Engine Sets the Standard for Smoothness and Quietness in Small Engines

Jan 7, 2013

Ford CEO Alan Mulally kissing 1.0-liter EcoBoost engine
  • Innovative engine mounts, flywheel and pulley in the new 1.0-liter Ford EcoBoost® engine combine to dramatically reduce the vibrations that are inherent in three-cylinder engines
  • Super-stiff block, isolated fuel injectors and oil-immersed timing belts help make 1.0-liter EcoBoost engine one of Ford’s quietest engines
  • 1.0-liter EcoBoost engine debuts in North America in the redesigned 2014 Ford Fiesta

Start up Ford’s patented new 1.0-liter three-cylinder EcoBoost® engine and chances are you’ll have to look at the tachometer to verify that the engine is running.

Ford engineers always knew they could build a powerful, fuel-efficient three-cylinder engine. The real engineering magic would be solving the problem that has often sunk previous three-cylinder automobile engines – conquering the unpleasant vibrations that come from having an odd number of cylinders under the hood.

For Ford’s new three-cylinder engine to be successful, it would have to be a no-compromise engine. It could not force customers to choose between performance versus economy or responsiveness versus smoothness. It had to deliver it all and it had to be affordable.

The traditional way of reducing shaking forces in small-displacement engines is to install a counter-rotating balance shaft inside the motor that cancels out most vibrations. But the problem with a balance shaft, explains Andy Delicata, Ford of Europe manager of Powertrain Noise, Vibration and Harshness, is that it is heavy, expensive, and it reduces fuel economy.

The 1.0-liter’s NVH engineering team, led by Delicata at Ford Technical Centres in Dunton and Dagenham, England, attacked the problem by focusing on two areas – the engine’s front pulley and rear flywheel, and the mounting system that connects the powertrain with the car’s body.

The pulley and flywheel are unbalanced with weights that are placed precisely to counteract the natural shaking forces of the engine and drive the energy in a less sensitive direction. The engine mounts are designed to decouple as well as absorb the engine’s shaking forces, Delicata explained.

The result is one of the smoothest and quietest engines in Ford’s global lineup. “We like to compare the refinement of the 1.0-liter EcoBoost engine with what you would typically experience in a vehicle two or three classes up from Fiesta and Focus,” said Delicata.

The smoothness of the engine is complemented by class-leading quietness. Engineers in Dunton and Dagenham attacked engine noise at its many sources.

For instance, a super-compact, highly stiff cast-iron block structure and an integrated engine mounting bracket are crucial in absorbing noise energy. In addition to immersing the engine’s toothed rubber timing belts in oil, isolated fuel injectors electronically controlled for soft landing and a foam-covered engine collectively help keep noise and vibration from reaching the driver.

The 1.0-liter EcoBoost engine is off to a fast start in Europe. Since its launch in March in the Focus, the 1.0-liter EcoBoost engine has won four major international awards. In the Focus, the 1.0-liter engine accounts for about 30 percent of sales, no small feat in a part of the world where the diesel engine is king.

The 1.0-liter is just now launching in B-MAX and C-MAX, and will be available in North America next year in the redesigned 2014 Ford Fiesta.

Source: Ford Motor Company

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Leah Buechley: How to “sketch” with electronics

Jan 6, 2012

Designing electronics is generally cumbersome and expensive -- or was, until Leah Buechley and her team at MIT developed tools to treat electronics just like paper and pen. In this talk from TEDYouth 2011, Buechley shows some of her charming designs, like a paper piano you can sketch and then play.

Leah Buechley is an MIT electronics designer who mixes high and low tech to create smart and playful results.

Source: TED

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Saturday, 5 January 2013

Building a better machine: Students use creativity to improve the heat engine

Jan 4, 2012

When Roman Berens signed up for the “Physics and Applied Physics Research Freshman” Seminar, he wasn’t sure what to expect.

“Initially, I really had no idea what it was about,” he said. “But I’m majoring in physics, so I thought having lab experience would be really valuable.”

Berens and other freshmen in the seminar discussed their research at a presentation at the Rowland Institute on Dec. 12. Using a handmade, laboratory-scale, Sterling heat engine, the team of students was able to generate enough electricity to power several light-emitting diodes, or LEDs, and a laptop computer.

“I’m amazed and invigorated by what our freshmen are capable of,” said Jene Golovchenko, Rumford Professor of Physics and Gordon McKay Professor of Applied Physics, and professor to the freshman seminar. “This year’s class has a wonderful collection of students who were admitted by interview to assure they were ready to take advantage of the high level of support provided them by the Rowland Institute. They are all prime candidates to concentrate in either in physics or SEAS,” the School of Engineering and Applied Sciences.

The seminar challenged students to study and improve upon the Sterling heat engine constructed by last year’s seminar students. Participants were tasked to improve on the existing model, turning it into a scientific instrument — embodying the laws of classical mechanics and thermodynamics.
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How a computer game could radically alter manufacturing

Jan 4, 2013

Here at The Engineer we’re used to explaining difficult concepts, whether it’s nuclear fusion or spintronics (actually I’m still not sure about that one). It helps that we have a receptive and enthusiastic audience and are tackling subject material that is usually instantly exciting.

But what if you had to explain something with less obvious appeal to people who think you might be wasting their time, for example, a complex new manufacturing business model to a group of sceptical bean counters? It’s probably not a conversation you’d want to have at a dinner party.

The answer to this might be to make the explanation into a game, according to one research group at least. Make the process fun, entertaining and engaging, and the audience might be more likely to understand and remember the concept, and perhaps even become more enthusiastic about it.

A team led by Aston University Business School are about to do just this by starting a five-year research project on the gamification of explaining servitisation. Now comes the bit where I explain what this boring and complicated-sounding concept actually is.

A product service system (PSS) is a business model where a firm offers both products and services. Rolls-Royce, for example, is well known for earning around 50 per cent of its revenue through service and support contracts, providing things such as maintenance and advice to customers that also buy its goods. Simply put, servitisation is when a straightforward manufacturing company adopts this model.

Particularly in developed marketplaces and economies, servitisation offers companies a chance to make more money than they would simply by selling products and competing against other manufacturers. Described like this, it sounds rather simple and very attractive. But making it a reality is a far more complex procedure with many barriers, and so servitisation of manufacturing firms has been slow.

Prof Tim Baines of Aston University argues that one of the biggest barriers to adoption of PSS is just explaining how the process of servitisation works. ‘To try to get those ideas across to someone in a manufacturing company in five or 10 minutes in a way that makes sense to them is quite challenging,’ he says.

This is where he believes gamification could come in. This is another slightly off-putting piece of jargon that basically means turning a process into a game. It’s not a new concept but has found growing popularity in recent years thanks to the growth of the internet and smartphones. There are any number of websites and apps that encourage you to do something by making it a game and rewarding you in some for participation.

For example, if you want to get fit but struggle to find the motivation, an app on your phone can monitor your progress to give you encouragement, telling you how many calories you’ve burnt or giving you badges for completing certain levels. One app even asks you to image you’re being chased by zombies and the only way to escape them is to run to a certain place.

But how will this work for explaining servitisation? Baines is planning to work with the Serious Games Institute at Coventry University and Sheffield’s Advanced Manufacturing Research Centre to create a computer simulation of a business adopting PSS. Companies, including Ford and Xerox, will then be brought in to test the game. ‘One of the big barriers is understanding, getting across the basic ideas and the language used, an appreciation of what it can actually mean,’ says Baines.

‘We’ll create a demonstration first of all so that we can communicate to the gaming community what we’re trying to do. The big hurdle is translating between these two communities, explaining to the gaming community what it is that we’re trying to model and them explaining to us what makes an engaging game. We’ve got to try to find the middle ground and from that we’ll create the basics of the game.’

It would be easy to write this concept of gamification off as a fad or a buzzword. For one thing, it doesn’t sound like the most fun idea for a game but, then again, there have been whole series of popular computer games designed around simulating real-life industries (Sim City, for example). And this won’t be the first time games are used to explain manufacturing concepts. Team games have been used before to demonstrate and introduce Western manufacturers to the Japanese-originated ideas of lean manufacturing.

Perhaps it will take more than a computer game to persuade companies to adopt dramatically different business models, but Baines hopes the game will do more than just change individual’s minds. ‘I would like it to be something quite pervasive that people inside the organisation become aware of and have a go at it, and for the top managers to hear about it not just from academics but also from people within the organisation who get to know about this thing called servitisation from playing the game.’

The game will also serve as a way for academics to further study servitisation so they can better understand the barriers to adopting PSS when it is attempted by real companies.

With gamification spreading even into business management techniques, it’s interesting to consider how else it could be used in manufacturing or other parts of the economy. Perhaps games could become a more common sight at work, motivating people to complete tasks or reach certain levels of achievement. On the other hand, you could argue we already run such a reward system. It’s called getting paid.

Source: The Engineer

Jumping droplets help heat transfer

Jan 4, 2013

Many industrial plants depend on water vapor condensing on metal plates: In power plants, the resulting water is then returned to a boiler to be vaporized again; in desalination plants, it yields a supply of clean water. The efficiency of such plants depends crucially on how easily droplets of water can form on these metal plates, or condensers, and how easily they fall away, leaving room for more droplets to form.

The key to improving the efficiency of such plants is to increase the condensers’ heat-transfer coefficient — a measure of how readily heat can be transferred away from those surfaces, explains Nenad Miljkovic, a doctoral student in mechanical engineering at MIT. As part of his thesis research, he and colleagues have done just that: designing, making and testing a coated surface with nanostructured patterns that greatly increase the heat-transfer coefficient.

The results of that work have been published in the journal Nano Letters, in a paper co-authored by Miljkovic, mechanical engineering associate professor Evelyn Wang, and five other researchers from the Device Research Lab (DRL) in MIT’s mechanical engineering department.

On a typical, flat-plate condenser, water vapor condenses to form a liquid film on the surface, drastically reducing the condenser’s ability to collect more water until gravity drains the film. “It acts as a barrier to heat transfer,” Miljkovic says. He and other researchers have focused on ways of encouraging water to bead up into droplets that then fall away from the surface, allowing more rapid water removal.

“The way to remove the thermal barrier is to remove [the droplets] as quickly as possible,” he says. Many researchers have studied ways of doing this by creating hydrophobic surfaces, either through chemical treatment or through surface patterning. But Miljkovic and his colleagues have now taken this a step further by making scalable surfaces with nanoscale features that barely touch the droplets.

The result: Droplets don’t just fall from the surface, but actually jump away from it, increasing the efficiency of the process. The energy released as tiny droplets merge to form larger ones is enough to propel the droplets upward from the surface, meaning the removal of droplets doesn’t depend solely on gravity.

Jumping-droplet superhydrophobic condensation shown on a nanostructured CuO tube.
Image courtesy of the researchers

 Other researchers have worked on nanopatterned surfaces to induce such jumping, but these have tended to be complex and expensive to manufacture, usually requiring a clean-room environment. Those approaches also require flat surfaces, not the tubing or other shapes often used in condensers. Finally, prior research has not tested the enhanced heat transfer predicted for these types of surfaces.

In a paper published early in 2012, the MIT researchers showed that droplet shape is important to enhanced heat transfer. “Now, we’ve gone a step further,” Miljkovic says, “developing a surface that favors these kinds of droplets, while being highly scalable and easy to manufacture. Furthermore, we’ve actually been able to experimentally measure the heat-transfer enhancement.”

The patterning is done, Miljkovic says, using a simple wet-oxidation process right on the surface that can be applied to the copper tubes and plates commonly used in commercial power plants.

The nanostructured pattern itself is made of copper oxide and actually forms on top of the copper tubing. The process produces a surface that resembles a bed of tiny, pointed leaves sticking up from the surface; these nanoscale points minimize contact between the droplets and the surface, making release easier.

Not only can the nanostructured patterns be made and applied under room-temperature conditions, but the growth process naturally stops itself. “It’s a self-limiting reaction,” Miljkovic says, “whether you put it in [the treatment solution] for two minutes or two hours.”

After the leaflike pattern is created, a hydrophobic coating is applied when a vapor solution bonds itself to the patterned surface without significantly altering its shape. The team’s experiments showed that the efficiency of heat transfer using these treated surfaces could be increased by 30 percent, compared to today’s best hydrophobic condensing surfaces.

That means, Miljkovic says, that the process lends itself to retrofitting thousands of power plants already in operation around the world. The technology could also be useful for other processes where heat transfer is important, such as in dehumidifiers and for heating and cooling systems for buildings, the authors say.

Challenges for this approach remain, Miljkovic says: If too many droplets form, they can “flood” the surface, reducing its heat-transfer ability. “We are working on delaying this surface flooding and creating more robust solutions that can work well [under] all operating conditions,” he says.

Yi Cui, an associate professor of materials science and engineering at Stanford University, calls the concept behind this work “an excellent idea,” and adds, “The studies here can lead to better atmospheric water-harvesting and dehumidification, and efficient heat transfer.” Cui adds that the fact that this team was able to make direct measurements of the actual heat-transfer enhancement from these treated surfaces is “interesting and important.”

The research team also included postdocs Ryan Enright and Youngsuk Nam and undergraduates Ken Lopez, Nicholas Dou and Jean Sack, all of MIT’s mechanical engineering department. The work was supported by MIT’s Solid-State Solar Thermal Energy Conversion Center, the U.S. Department of Energy, the National Science Foundation and the Irish Research Council for Science, Engineering and Technology.

Source: MIT

New 2D material for next generation high-speed electronics

Jan 4, 2013

Artist impression of high carrier mobility through layered molybdenum oxide crystal lattice. Credit: Dr Daniel J White, ScienceFX

Scientists at CSIRO and RMIT University have produced a new two-dimensional material that could revolutionise the electronics market, making “nano” more than just a marketing term.

The material – made up of layers of crystal known as molybdenum oxides – has unique properties that encourage the free flow of electrons at ultra-high speeds.

In a paper published in the January issue of materials science journal Advanced Materials, the researchers explain how they adapted a revolutionary material known as graphene to create a new conductive nano-material.

Graphene was created in 2004 by scientists in the UK and won its inventors a Nobel Prize in 2010. While graphene supports high speed electrons, its physical properties prevent it from being used for high-speed electronics.

The CSIRO's Dr Serge Zhuiykov said the new nano-material was made up of layered sheets – similar to graphite layers that make up a pencil's core.

"Within these layers, electrons are able to zip through at high speeds with minimal scattering," Dr Zhuiykov said.

"The importance of our breakthrough is how quickly and fluently electrons – which conduct electricity – are able to flow through the new material."

RMIT's Professor Kourosh Kalantar-zadeh said the researchers were able to remove "road blocks" that could obstruct the electrons, an essential step for the development of high-speed electronics.

"Instead of scattering when they hit road blocks, as they would in conventional materials, they can simply pass through this new material and get through the structure faster," Professor Kalantar-zadeh said.

"Quite simply, if electrons can pass through a structure quicker, we can build devices that are smaller and transfer data at much higher speeds.

"While more work needs to be done before we can develop actual gadgets using this new 2D nano-material, this breakthrough lays the foundation for a new electronics revolution and we look forward to exploring its potential."

In the paper titled 'Enhanced Charge Carrier Mobility in Two-Dimensional High Dielectric Molybdenum Oxide,' the researchers describe how they used a process known as "exfoliation" to create layers of the material ~11nm thick.

The material was manipulated to convert it into a semiconductor and nanoscale transistors were then created using molybdenum oxide.

The result was electron mobility values of  >1,100 cm2/Vs – exceeding the current industry standard for low dimensional silicon.

The work, with RMIT doctoral researcher Sivacarendran Balendhran as the lead author, was supported by the CSIRO Sensors and Sensor Networks Transformational Capability Platform and the CSIRO Materials Science and Engineering Division.

It was also a result of collaboration between researchers from Monash University, University of California – Los Angeles (UCLA), CSIRO, Massachusetts Institute of Technology (MIT) and RMIT.

Source:  CSIRO

Doris Kim Sung: Metal that breathes

Jan 4, 2013

Modern buildings with floor-to-ceiling windows give spectacular views, but they require a lot of energy to cool. Doris Kim Sung works with thermo-bimetals, smart materials that act more like human skin, dynamically and responsively, and can shade a room from sun and self-ventilate.

Doris Kim Sung is a biology student turned architect interested in thermo-bimetals, smart materials that respond dynamically to temperature change.

Source:  Ted

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