Sharp Develops Concentrator Solar Cell with World’s Highest Conversion Efficiency of 43.5%

Engineerblogger
May 31, 2012

Sharp Corporation has achieved the world’s highest solar cell conversion efficiency*1 of 43.5%*2 using a concentrator triple-junction compound solar cell. These solar cells are used in a lens-based concentrator system that focuses sunlight on the cells to generate electricity.

Compound solar cells utilize photo-absorption layers made from compounds consisting of two or more elements, such as indium and gallium. The basic structure of this latest triple-junction compound solar cell uses Sharp’s proprietary technology that enables efficient stacking of the three photo-absorption layers, with InGaAs (indium gallium arsenide) as the bottom layer.

To achieve this latest increase in conversion efficiency, Sharp capitalized on the ability of this cell to efficiently convert sunlight collected via three photo-absorption layers into electricity. Sharp also optimized the spacing between electrodes on the surface of the concentrator cell and minimized the cell’s electrical resistance.

This latest Sharp breakthrough came about through research and development efforts that are part of the “R&D on Innovative Solar Cells” project promoted by Japan’s New Energy and Industrial Technology Development Organization (NEDO).*3 Measurement of the value of 43.5%, which sets a record for the world’s highest concentrating conversion efficiency, was confirmed at the Fraunhofer Institute for Solar Energy Systems (ISE)*4 in Germany.

Because of their high conversion efficiency, compound solar cells have been used primarily on space satellites. Sharp’s aim for the future is to apply this latest development success into concentrator photovoltaic power systems that can efficiently generate electricity using small-surface-area solar cells and make them practical for terrestrial use.

Source: Sharp Corporation

Additional Information:

1. As of May 30, 2012, for concentrator solar cells at the research level (based on a survey by Sharp).
2. Conversion efficiency confirmed by the Fraunhofer Institute for Solar Energy (ISE; one of several organizations around the world that officially certifies energy conversion efficiency measurements in solar cells) in April 2012 under a light-concentrating magnification of 306 times (cell surface: approx. 0.167 cm²). 43.5% is the same conversion efficiency achieved by Solar Junction of the United States in March 2011.
3. NEDO is one of Japan’s largest public management organizations for promoting research and development as well as for disseminating industrial, energy, and environmental technologies.
4. ISE was one of the participating members from the EU side at “NGCPV: A new generation of concentrator photovoltaic cells, modules and systems”. The collaboration is part of the “R&D in Innovative Solar Cells” project.

Is This the Key to Vastly Better Batteries?

Engineerblogger
May 31, 2012

Power maker: This component is part of a new, cheaper process to make ionic liquids (upper left) that could greatly boost the storage capacity of batteries. Credit: Boulder Ionics

Researchers are experimenting with a handful of ideas that could make batteries vastly better than they are today, which could lead to more affordable electric cars and cheaper ways to store solar power to use at night. But many of these approaches have one thing in common: they aren't practical because of the shortcomings of existing battery electrolytes.

Jerry Martin, CEO and cofounder of a small startup in Colorado, says his company—Boulder Ionics—is developing a way of making a type of electrolyte that would enable high-performance batteries. The electrolyte, made from ionic liquids—salts that are molten below 100 ⁰C—can operate at high voltages and temperatures, isn't flammable, and doesn't evaporate. Ionic liquids are normally expensive to produce, but Boulder Ionics is developing a cheaper manufacturing process.

Replacing conventional electrolytes with ionic liquids could double the energy storage capacity of ultracapacitors by allowing them to be charged to higher voltages. That could make it possible to replace a starter battery in a car with a battery the size of a flashlight, Martin says.

The electrolytes could also help improve the storage capacity of lithium-ion batteries, the kind used in electric vehicles and mobile phones; and they could help make rechargeable metal-air batteries practical. In theory, such batteries could store 10 times as much energy as conventional lithium-ion batteries.

Boulder Ionics, which is a year-and-a-half old, has built and demonstrated the key pieces of equipment needed for its process and used them to make evaluation samples for battery manufacturers. Earlier this year, it raised $4.3 million in venture capital.

Martin says his company's process could actually make ionic liquids that are cheaper than conventional electrolytes per watt-hour of energy storage in the batteries they enable.

The company is reducing the cost of making them in two main ways. First, it's switching from a batch process to a continuous one. This is far faster—it takes six minutes to make ionic liquid electrolyte, compared to three days for a conventional process—and allows the company to produce more material with a given-size piece of equipment, which reduces capital costs. Instead of building a large chemical plant, it would be possible to make enough ionic liquid for 100,000 electric cars in a space the size of a living room, Martin says.

The continuous process also gives Boulder Ionics more precise control over the chemical reactions involved, which reduces impurities. Martin says this makes costly purification steps unnecessary. Scaling up continuous production could prove a challenge, however.

For use in ultracapacitors, the new ionic liquid electrolyte can simply replace a conventional one. "It's a nearly drop-in replacement, compatible with existing production lines," Martin says. But battery makers will need to switch to new electrode materials that operate at higher voltages to take advantage of the high-voltage resistance of ionic liquids in lithium-ion batteries.

Ionic liquids are suitable for rechargeable metal-air batteries because the electrolyte in such a battery is exposed to the air, and ionic liquids do not evaporate. At least one company, Fluidic Energy, is hoping to make metal-air batteries practical by using ionic liquids.

Source: Technology Review

Researchers unique approach to materials allows temperature-stable circuits

Engineerblogger
May 31, 2012

Sandia National Laboratories materials science researcher Steve Dai has come up with a unique approach to creating materials whose properties won't degenerate with temperature swings. (Photo by Randy Montoya)

Sandia National Laboratories researcher Steve Dai jokes that his approach to creating materials whose properties won’t degenerate during temperature swings is a lot like cooking — mixing ingredients and fusing them together in an oven.

Sandia has developed a unique materials approach to multilayered, ceramic-based, 3-D microelectronics circuits, such as those used in cell phones. The approach compensates for how changes due to temperature fluctuations affect something called the temperature coefficient of resonant frequency, a critical property of materials used in radio and microwave frequency applications. Sandia filed a patent for its new approach last fall. The work was the subject of a recently completed two-year Early Career Laboratory Directed Research and Development (LDRD) project that focused on understanding why certain materials behave as they do. That knowledge could help manufacturers design and build better products.

“At this point we’re just trying to demonstrate that the technology is practical,” Dai said. “Can we design a device with it, can we design it over and over again, and can we design this reliably?”

The familiar cell phone illustrates how the development might be used. The Federal Communications Commission allocates bandwidth to various uses — aviation, the military, cell phones, and so on. Each must operate within an assigned bandwidth with finite signal-carrying capacity. But as temperatures vary, the properties of the materials inside the phone change, and that causes a shift in the resonant frequency at which a signal is sent or received.

Because of that shift, cell phones are designed to operate squarely in the middle of the bandwidth so as not to break the law by drifting outside their assigned frequency range. That necessary caution wastes potential bandwidth and sacrifices higher rates at which data could move.

Dai worked on low-temperature co-fired ceramic (LTCC), a multilayer 3-D packaging and interconnection technology that can integrate passive components — resistors, capacitors and inductors.

Most mainstream LTCC dielectrics now on the market have a temperature coefficient of resonant frequency in a range as wide as that between northern Alaska in the winter and southern Arizona in the summer. Dai’s research achieved a near-zero temperature coefficient by incorporating compensating materials into the LTCC — basically a dielectric that works against the host dielectric and in essence balances the temperature coefficient of resonant frequency. A dielectric is a material, such as glass, that does not conduct electricity but can sustain an electric field.

A graph shows the differences. Resonant frequencies used in various LTCC base dielectrics today appear as slanted lines on the graph as temperatures change. Dai’s approach to an LTCC leaves the line essentially flat — indicating radio and microwave resonator frequency functions that remain stable as temperatures change.

He presented the results of the approach in a paper published in January in the Journal of Microelectronics and Electronic Packaging.

“We can actually make adjustments in the materials property to make sure my resonance frequency doesn’t drift,” Dai said. “If this key property of your material doesn’t drift with the temperature, you can fully utilize whatever the bandwidth is.”

Another advantage: Manufacturers could cut costs by eliminating additional mechanical and electrical circuits now built into a device to compensate for temperature variations.

One challenge was choosing different materials that don’t fall apart when co-fired together, Dai said. Glass ceramic materials used in cell phone applications are both fragile and rigid, but they’re also very solid with minimal porosity. Researchers experimented with different materials, changing a parameter, adjusting the composition, and seeing which ones worked best together.

He had to consider both physical and chemical compatibility. Physical compatibility means that as materials shrink when they’re fired, they shrink in the same way so they don’t warp or buckle. Chemical compatibility means each material retains its unique properties rather than diffusing into the whole.

The LDRD project created a new set of materials to solve the problem of resonant frequency drift but also developed a better understanding of why and how the processes involved in identifying the best materials work. “Why select material A and not B, what’s the rationale? Once you have A in place, what’s the behavior when you make a formulation change, a composition change, do little things?” Dai said.

Researchers looked at variables to boost performance. For example, the functional material within the composite carries the electrical signal, and researchers experimented with placing that material in different areas within the composite until they came up with what arrangement worked best and understood why.

The team also constructed a computational model to analyze what happens when materials with different properties are placed together, and what happens when they change their order in the stacked layers or the dimensions of one material versus another.

“We study all these different facets, the placement of materials, the thickness, to try to hit the sweet spot of the commercial process,” Dai said.

Manufacturing can be done as simple screen printing, a low-cost, standard commercial process much like printing an image on a T-shirt. Dai said the idea was to avoid special requirements that would make the process more expensive or difficult.

“That’s kind of the approach you try to take: Make it simple to use with solid understanding of the fundamentals of materials science,” he said.

Source: Sandia National Laboratories

Researchers find new properties of the carbon material graphene

Engineerblogger
May 30, 2012

Iowa State physicist Jigang Wang, right, examines graphene monolayers grown on a substrate mounted in a cooper adapter as graduate students Tianq Li, far left, and Liang Luo look on in Wang's laboratory.

Graphene has caused a lot of excitement among scientists since the extremely strong and thin carbon material was discovered in 2004. Just one atom thick, the honeycomb-shaped material has several remarkable properties combining mechanical toughness with superior electrical and thermal conductivity.

Now a group of scientists at Iowa State University, led by physicist Jigang Wang, has shown that graphene has two other properties that could have applications in high-speed telecommunications devices and laser technology – population inversion of electrons and broadband optical gain.

Wang is an assistant professor in the Department of Physics and Astronomy in the College of Liberal Arts and Sciences at Iowa State University. He also is an associate scientist with the Department of Energy's Ames Laboratory.

Wang's team flashed extremely short laser pulses on graphene. The researchers immediately discovered a new photo-excited graphene state characterized by a broadband population inversion of electrons. Under normal conditions, most electrons would occupy low-energy states and just a few would populate higher-energy states. In population-inverted states, this situation is reversed: more electrons populate higher, rather than lower, energy states. Such population inversions are very rare in nature and can have highly unusual properties. In graphene, the new state produces an optical gain from the infrared to the visible.

Simply stated, optical gain means more visible light comes out than goes in. This can only happen when the gain medium is externally pumped and then stimulated with light (stimulated emission). Wang’s discovery could open doors for efficient amplifiers in the telecommunication industry and extremely fast opto-electronics devices.
Graphene as a gain medium for light amplification

"It's very exciting," Wang said. "It opens the possibility of using graphene as a gain medium for light amplification. It could be used in making broadband optical amplifiers or high-speed modulators for telecommunications. It even provides implications for development of graphene-based lasers."

Wang's team unveiled its findings in the journal Physical Review Letters on April 16. In addition to Wang, the paper's other authors are Tianq Li, Liang Luo and Junhua Zhang, Iowa State physics graduate students; Miron Hupalo, Ames Laboratory scientist; and Michael Tringides and Jörg Schmalian, Iowa State physics professors and Ames Laboratory scientists.

Wang is a member of the Condensed Matter Physics program at Iowa State and the Ames Laboratory. He and his team conduct optical experiments using laser spectroscopy techniques, from the visible to the mid-infrared and far-infrared spectrum. They use ultrashort laser pulses down to 10 quadrillionths of a second to study the world of nanoscience and correlated electron materials.

In 2004 United Kingdom researchers Andre Geim and Konstantin Novoselov discovered graphene, which led to their winning the 2010 Nobel Prize in Physics. Graphene is a two-dimensional (height and width) material with a growing list of known unique properties. It is a single layer of carbon only one atom thick. The carbon atoms are connected in a hexagonal lattice that looks like a honeycomb. Despite a lack of bulk, graphene is stronger than steel, it conducts electricity as well as copper and conducts heat even better. It is also flexible and nearly transparent.

An understanding gap existed, Wang explained, between the two scientific communities that studied the electronic and photonic properties of graphene. He believed his group could help bridge the gap by elaborating the non-linear optical properties of graphene and understanding the non-equilibrium electronic state. Wang explained that linear optical properties only transmit light – one light signal comes into a material and one comes out. "The non-linear property can change and modulate the signal, not just transmit it, producing functionality for novel device applications."
Graphene in a highly non-linear state

Wang said other scientists have studied graphene's optical properties, but primarily in the linear regime. His team hypothesized they could generate a new "very unconventional state" of graphene resulting in population inversion and optical gain.

"We were the first group to break new ground, to start looking at it in a highly excited state consisting of extremely dense electrons – a highly non-linear state. In such a state, graphene has unique properties."

Wang's group started with high-quality graphene monolayers grown by Hupalo and Tringides in the Ames Laboratory. The researchers used an ultrafast laser to "excite" the material's electrons with short pulses of light just 35 femtoseconds long (35 quadrillionths of a second). Through measurements of the photo-induced electronic states, Wang's team found that optical conductivity (or absorption) of the graphene layers changed from positive to negative – resulting in the optical gain – when the pump pulse energy was increased above a threshold.

The results indicated that the population inverted state in photoexcited graphene emitted more light than it absorbed. "The absorption was negative. It meant that population inversion is indeed established in the excited graphene and more light came out of the inverted medium than what entered, which is optical gain," Wang said. "The light emitted shows gain of about one percent for a layer a mere one atom thick, a figure on the same order to what's seen in conventional semiconductor optical amplifiers hundreds of times thicker."

The key to the experiments, of course, was creating the highly non-linear state, something "that does not normally exist in thermal equilibrium," Wang said. "You cannot simply put graphene under the light and study it. You have to really excite the electrons with the ultrafast laser pulse and have the knowledge on the threshold behaviors to arrive at such a state."

Wang said a great deal more engineering and materials perfection lies ahead before graphene's full potential for lasers and optical telecommunications is ever realized. "The research clearly shows, though, that lighting up graphenes may produce brighter emissions as well as a bright future," he said.

Source:  Iowa State University

Planning for uncertainty in power generation

Engineerblogger
May 30, 2012


Renewable energy sources such as wind and solar power help to diversify the nation's energy mix, but they also bring new uncertainty to the power supply. Two UC Davis researchers are working with a national team of experts, funded by the U.S. Department of Energy, to help power utilities make sound plans in the face of that uncertainty.

"The goal is to be able to plan to generate power in the face of the uncertainty caused by a 30-percent penetration of renewables in the power supply," said David Woodruff, a professor in the UC Davis Graduate School of Management.

Woodruff and Roger Wets, a distinguished research professor in the UC Davis Department of Mathematics, are collaborating on the $3 million, two-year project with partners at Iowa State University, Sandia National Laboratories, Alstom, and the Independent System Operator (ISO)-New England. Woodruff and Wets are leading experts in the field of optimization under uncertainty.

The team plans to develop tools that can be implemented commercially by power utilities and regional system operators such as ISO-New England.

Wind and solar power bring big advantages in reducing carbon emissions, but power generation can drop suddenly as clouds form or wind dies down. To compensate, power system managers keep extra capacity from coal- and gas-fired plants in reserve. Coal-fired electricity is relatively cheap, but slow to come online. Gas plants can ramp up fast, but are more expensive. That means that the cost of power can fluctuate over a few hours or even minutes.

One option is to pass costs directly to consumers through a "smart grid" and other devices. For example, a "smart" air conditioning unit could be programmed to cut off when the cost of power goes beyond a pre-set level. But although consumers might plan to be thrifty, when the mercury rises they may well hit the override switch.

"It's hard to predict what consumers will do when you expose them to these prices," Woodruff said.

Woodruff, Wets and colleagues are pursuing a second option, using large-scale computational models to find optimal strategies to hedge against fluctuations in regional power supply.

The project is funded through the Green Electricity Network Integration program of the U.S. Department of Energy's Advanced Research Projects Agency-Energy.

Source: UC Davis

New materials could slash energy costs for CO2 capture

Engineerblogger
May 30, 2012

Artist Kelly Harvey evoked images of the sea and a coral reef to hint at the diversity of structures in Rice's zeolite database.

A detailed analysis of more than 4 million absorbent minerals has determined that new materials could help electricity producers slash as much as 30 percent of the “parasitic energy” costs associated with removing carbon dioxide from power plant emissions.

The research by scientists at Rice University, the University of California, Berkeley, Lawrence Berkeley National Laboratory (LBNL) and the Electric Power Research Institute (EPRI) was published online this week in the journal Nature Materials.

Coal- and natural-gas-fired power plants account for about half of the carbon dioxide (CO2) that humans add to the atmosphere each year, but current technology for capturing that CO2 and storing it underground can gobble up as much as one-third of the steam the plant could otherwise use to make electricity.

In the new study, researchers found that commonly used industrial minerals called zeolites could significantly improve the energy efficiency of “carbon capture” technology.

“It looks like we can beat the current state-of-the-art technology by about 30 percent, and not just with one or two zeolites,” said study co-author Michael Deem, Rice’s John W. Cox Professor of Bioengineering and professor of physics and astronomy. “Our analysis showed that dozens of zeolites are more efficient than the amine absorbents currently used for CO2 capture.”

Commercial power plants do not capture CO2 on a large scale, but the technology has been tested at pilot plants. At test plants, flue gases are funneled through a bath of ammonia-like chemicals called amines. The amines are then boiled to release the captured CO2, and additional energy is required to compress the CO2 so it can be pumped underground. The “parasitic energy” costs associated with current technology is high; up to one-third of the steam that could be used to generate electricity is siphoned off to boil the amines and liquefy the CO2.

Deem said the new study is the first to compare the “parasitic energy” costs for a whole class of carbon-capture materials. The study found dozens of zeolites that could remove CO2 from flue gas for a lower energy cost than amines could.

Zeolites are common minerals made mostly of silicon and oxygen. About 40 exist in nature, and there are about 160 man-made types. All zeolites are highly porous — like microscopic Swiss cheese — and the pore sizes and shapes vary depending upon how the silicon and oxygen atoms are arranged. The pores act like tiny reaction vessels that capture, sort and spur chemical reactions of various kinds, depending upon the size and shape of the pores. The chemical industry uses zeolites to refine gasoline and to make laundry detergent and many other products.

In 2007, Deem and colleagues used computers to calculate millions of atomic formulations for zeolites, and they have continued to add information to the resulting catalog, which contains about 4 million zeolite structures.

In the new study, the zeolite database was examined with a new computer model designed to identify candidates for CO2 capture. The new model was created by a team led by co-author Berend Smit, UC Berkeley’s Chancellor’s Professor in the departments of chemical and biomolecular engineering and of chemistry and a faculty senior scientist at LBNL. Smit and his UC Berkeley group worked with study co-author Abhoyjit Bhown, a technical executive at EPRI, to establish the best criteria for a good carbon capture material. Focusing on the energy costs of capture, release and compression, they created a formula to calculate the energy consumption for any materials in the zeolite database.

In this zeolite structure, the arrangement of oxygen atoms (red) and silicon atoms (tan) influences the regions in the pores (colored surface) where CO2 can be captured.

Running the painstaking calculations to compare the CO2-capture abilities of each zeolite would have taken approximately five years with standard central processing units (CPUs), so Smit and his colleagues at UC-Berkeley and LBNL created a new way to run the calculations on graphics processing units, or GPUs — the processors used in PC graphics cards. Deem said the GPU technique cut the compute time to about one month, which made the project feasible.

Smit said, “Our database of carbon capture materials is going to be coupled to a model of a full plant design, so if we have a new material, we can immediately see whether this material makes sense for an actual design.”

Study co-authors include graduate students Li-Chiang Lin and Joseph Swisher, both of UC Berkeley; Adam Berger of the EPRI; Richard Martin, Chris Rycroft and Maciej Haranczyk, all of LBNL’s Computational Research Division; and postdoctoral fellows Jihan Kim and Kuldeep Jariwala of LBNL’s Materials Science Division. This research was supported by the Department of Energy, the Advanced Research Projects Agency–Energy and EPRI’s Office of Technology Innovation.

Source: Rice University

High-speed method to aid search for solar energy storage catalysts

Engineerblogger
May 30, 2012


Eons ago, nature solved the problem of converting solar energy to fuels by inventing the process of photosynthesis.

Plants convert sunlight to chemical energy in the form of biomass, while releasing oxygen as an environmentally benign byproduct. Devising a similar process by which solar energy could be captured and stored for use in vehicles or at night is a major focus of modern solar energy research.

“It is widely recognized that solar energy is the most abundant source of energy on the planet,” explains University of Wisconsin-Madison chemistry professor Shannon Stahl. “Although solar panels can convert sunlight to electricity, the sun isn't always shining.”

Thus, finding an efficient way to store solar energy is a major goal for science and society. Efforts today are focused on electrolysis reactions that use sunlight to convert water, carbon dioxide, or other abundant feedstocks into chemicals that can be stored for use any time.

A key stumbling block, however, is finding inexpensive and readily available electrocatalysts that facilitate these solar-driven reactions. Now, that quest for catalysts may become much easier thanks to research led by Stahl and UW-Madison staff scientist James Gerken and their colleagues.

Writing this week in the journal Angewandte Chemie, the Wisconsin group describes a new high-throughput method to identify electrocatalysts for water oxidation.

Efficient, earth-abundant electrocatalysts that facilitate the oxidation of water are critical to the production of solar fuels, says Gerken. "If we do this well enough, we can keep the party going all night long."

Existing technology to store solar energy is not economicallyviable because using the sun to split water into oxygen and hydrogen is inefficient. Water oxidation provides electrons and protons needed for hydrogen production, and better catalysts minimize the energy lost when converting energy from sunlight to chemical fuels, says Stahl.

In addition to being efficient, the catalysts need to be made from materials that are more abundant and far less expensive than metals like platinum and the rare earth compounds currently found in the most effective catalysts.

According to Stahl and Gerken, the discovery of promising electrocatalytic materials is hindered by the costly and laborious approaches used to discover them. What’s more, the sheer number of possible catalyst compositions far exceeds the number that can be tested using traditional methods.

In the Angewandte Chemie report, Gerken, Stahl and their colleagues describe a screening method capable of rapidly evaluating potential new electrocatalysts. In simple terms, the technique works using ultraviolet light and a fluorescent paint to test prospective metal-oxide electrocatalysts. A camera captures images from a grid of candidate catalysts during the electrolysis process, as the paint responds to the formation of oxygen. This approach turns out to be a highly efficient way to sort through many compounds in parallel to identify promising leads.

Already, the Wisconsin team has identified several new metal-oxide catalysts that are composed of inexpensive materials such as iron, nickel and aluminum, and that hold promise for use in solar energy storage.

In addition to Gerken and Stahl, authors of the new study include Jamie Y.C. Chen, Robert C. Massé, and Adam B. Powell, all of UW-Madison's department of chemistry. The work was supported by a grant from the U.S. National Science Foundation and a provisional patent has been submitted through the Wisconsin Alumni Research Foundation.

Source:  University of Wisconsin-Madison

Engineers Develop Cheap Onboard Tracking System For UAVs

Engineerblogger
May 30, 2012

The popularity of Unmanned Aerial Vehicles or UAVs has exploded in just a few years. That's the result of smaller, cheaper computers that allow these vehicles to fly unaided, better radio communication systems and more efficient, lighter motors for longer flight times.

As a result, UAVs are extraordinarilly capable. The flying machines available in any toyshop for a few hundred dollars would have been the envy of any UAV research team just ten years ago.

But there are still limits to what these machines can do and one of them is tracking objects on the ground. Send up one of these cheap UAVs to circle your house or to follow a car and it'll be hopelessly lost in seconds.

That's because object recognition tends to be a computationally intensive task and there are obvious power and weight limits for small flyers.

The standard way to solve this problem is to broadcast the images back to the ground where they can be crunched relatively easily and then sent back. But this obviously doesn't work when communications systems are disrupted.

So today Ashraf Qadir and pals at the University of North Dakota in Grand Forks reveal a solution. With Department of Defense funding, these guys have built their own image processing machine, which is small and light enough to be carried by a small UAV. They say their device is capable of tracking objects such as cars and houses in real time without the need for number crunching on the ground.

The way these guys have solved this problem is to simplify it and then solve the simplified puzzle. They point out that from a plane, objects on the ground such as cars and houses do not generally change shape.

However, they do change their orientation and position relative to the camera. So their object-tracking program essentially solves just these two problems. First , it uses the motion of the object in the previous frames to predict where it is going to be in the next frame. That's fairly straightforward.

Second, it uses a remarkably simple process to follow the object as it rotates. When the onboard computer first finds its target, it uses a simple image processing program to creates a set of images in which the object is rotated by 10 degrees. That produces a library of 36 pictures showing the object in every orientation.

So the process of following the target is simply a question of matching it to one of those images. Qadir and co have developed a simple protocol to optomise this process.

And that's it. They've tested the approach both in the lab and in the air using a Linux computer on a single printed circuit board plus a small camera and gimballing system. All this is carried on board the university's customised UAV called Super Hauler with a wingspan of 350 centimetres and payload capability of 11 kilograms.

These guys say the system worked well in tests. The UAV has an air-to-ground video link which allows an operator to select a target such as a car, building, or in these tests, the group's control tent. The onboard computer then locks onto the target, generates the image library and begins tracking.

From an altitude of 200 metres or so, Qadir and co say the system works well at frame rates over 25 frames per second--that's essentially real time..

Of course, the systems has some limitations. Following a single vehicle is obviously much harder than selecting and following one of many in traffic, for example. Similarly, station keeping over a single tent in a field is relatively straightforward compared to the same problem in suburbia where all the houses look the same.

But one step at a time, as they say. These are problems for the future.

These guys have a proof-of-principle device that could easily be deployed cheaply and more widely. The Super Hauler isn't quite in the 'toy' department yet but it isn't hard to imagine how a version of this kind of software and hardware could be deployed in cheap UAVs elsewhere in the near future.

The Department of Defense obviously has its own uses for this kind of gear but for the rest of us it boils down to stalking. All of a sudden, it won't be so hard to follow your boyfriend's car when he says he's going to the game or station keep over your girlfriend's house when she says she "needs time to herself". Gulp!



Source: Technology Review

Additional Information:

• Ref: arxiv.org/abs/1205.5742: Implementation of an Onboard Visual Tracking System with Small Unmanned Aerial Vehicle (UAV)

Study takes novel 'back-casting' approach to transform cities for healthier lives

Engineerblogger
May 30, 2012


Researchers at four of the country’s leading universities, led by the University of Birmingham, are embarking on a low carbon engineering project that could transform the way cities are built, as well as the way we live in them, by taking a novel ‘back-casting’ approach to their study.

The study will create visions of an alternative urban future with drastically reduced CO2 emissions then develop realistic and radical engineering solutions to achieve them in a socially acceptable way. Research will closely link people’s social aspirations and wellbeing with the engineering of cities.

The UK government is committed to meeting its 2050 climate change target to reduce greenhouse gas emissions by 80 per cent from 1990 levels.

Professor Chris Rogers at the University of Birmingham’s School of Civil Engineering, said: ‘Engineering of our cities has traditionally been a ‘top-down’ exercise, mainly because it’s so very difficult to create a ‘bottom-up’ approach: solutions are created and society must either learn to work and live with them or choose to resist them.

‘Our research is novel in that we start by imagining the future that we want for our cities, for example, what does a city like Birmingham look like with an 80 per cent carbon reduction? We then work backwards to find out what combinations of engineering solutions, behavioural changes and technological developments are needed to make these alternative futures possible, while at the same time ensuring that the planet can still provide us with the resources we need. The ambition of our research programme is necessary to deal with the global challenges that we face.’

Professor Rogers’ research experience encompasses the Mapping the Underworld project to create a prototype multi-sensor device to detect and map the pipes that lie beneath our cities’ streets without the need for excavation. Such technical advances will make utility service provision and streetworks more sustainable.

As the world undergoes the largest wave of urban growth in history, research that can provide visions of an alternative economically viable future for low carbon, sustainable development is crucial.

In 2008, for the first time in history, more than half the world’s population was living in towns and cities. The UK was the first country in the world in which this happened. By the time of the 2001 census almost 80 per cent of the UK population was living in cities, today this figure has risen to 90 per cent.

By using focus groups, case studies, a city analysis methodology and other approaches in pioneering futures research, the researchers will create a roadmap that aims to drive future engineering thinking for decades to come. Its goal is to influence policy and be used by urban designers in the UK with the potential to be applied anywhere in the world.

The study has been made possible by a £6 million programme grant from the Engineering and Physical Sciences Research Council (EPSRC). Programme grants are flexible grants made available to world-leading research teams aiming to address major research challenges.

Lancaster University, University College London and the University of Southampton are part of the five-year multidisciplinary research team. Commercial partners include power and gas company E-ON, global engineering consultancy Halcrow, international engineering and construction company Costain, and the UK’s rail operator Network Rail.

Source:  Birmingham University


Additional Information:

• Engineering and Physical Sciences Research Council (EPSRC)

Copper-Nickel Nanowires Could Be Perfect Fit For Printable Electronics

Engineerblogger
May 29, 2012


Copper-nickel nanowires stay shiny, unlike old pennies, making them better for printed electronics & display screens.

While the Statue of Liberty and old pennies may continue to turn green, printed electronics and media screens made of copper nanowires will always keep their original color.

Duke University chemists created a new set of flexible, electrically conductive nanowires from thin strands of copper atoms mixed with nickel. The copper-nickel nanowires, in the form of a film, conduct electricity even under conditions that break down the transfer of electrons in plain silver and copper nanowires, a new study shows.

Because films made with copper-nickel nanowires are stable and are relatively inexpensive to create, they are an attractive option to use in printed electronics, products like electronic paper, smart packaging and interactive clothing, said Benjamin Wiley, an assistant professor of chemistry at Duke. His team describes the new nanowires in a NanoLetters paper published online May 29.

The new copper-nickel nanowires are the latest nanomaterial Wiley's lab has developed as a possible low-cost alternative to indium tin oxide, or ITO. This material is coated on glass to form the transparent conductive layer in the display screens of cell phones, e-readers and iPads.

Indium, at $600 - $800 per kilogram, is an expensive rare-earth element. Most of it is mined and exported from China, which is reducing exports, causing indium's price to increase. Indium tin oxide is deposited as a vapor in a relatively slow, expensive coating process, adding to its cost. And the film is brittle, which is a major reason the signature pads at grocery store checkout lines eventually fail and why there is not yet a flexible, rollable iPad.

Last year, Wiley's lab created copper nanowire films that can be deposited from a liquid in a fast, inexpensive coating process. These conductive films are much more flexible than the current ITO film. Copper is also one-thousand times more abundant and one-hundred times cheaper than indium. One problem with copper nanowire films, however, is that they have an orange tint that would not be desirable in a display screen. The copper-based films also oxidize gradually when exposed to air, suffering from the same chemical reaction that turns the Statue of Liberty or an old penny green, Wiley said.

Nickels, however, rarely turn green. Inspired by the U.S. five-cent piece, Wiley wondered if he could prevent oxidation of the copper nanowires by adding nickel. He and his graduate student, Aaron Rathmell, developed a method of mixing nickel into the copper nanowires by heating them in a nickel salt solution.

"Within a few minutes, the nanowires become much more grey in color," Wiley said.

Rathmell and Wiley then baked the new nanowires at various temperatures to test how long they conducted electricity and resisted oxidation. The tests show that the copper-nickel nanowire films would have to sit in air at room temperature for 400 years before losing 50 percent of their electrical conductivity. Silver nanowires would lose half of their conductivity in 36 months under the same conditions. Plain copper nanowires would last only 3 months.

While the copper-nickel nanowires stack up against silver and copper alone, they aren't going to replace indium-tin-oxide in flat-panel displays any time soon, Wiley said, explaining that, for films with similar transparency, copper-nickel nanowire films cannot yet conduct the same amount of electricity as ITO. "Instead, we're currently focusing on applications where ITO can't go, like printed electronics," he said.

The greater stability of copper-nickel nanowires makes them a better alternative to both copper and silver for applications that require a stable level of electrical conductivity for more than a few years, which is important for certain printed electronics applications, Wiley said.

He explained that printed electronics combine conductive or electronically active inks with the printing processes that make magazines, consumer packaging and clothing designs. The low cost and high speed of these printing processes make them attractive for the production of solar cells, LEDs, plastic packaging and clothing.

A Durham, NC startup company, NanoForge Corp., which Wiley co-founded has begun manufacturing copper-nickel nanowires to test in these and other potential applications.

Source: Duke University

Additional Information:

• "Synthesis of Oxidation-Resistant Cupronickel Nanowires for Transparent Conducting Nanowire Networks'" Rathmell, A. R., Nguyen, M., Chi, M. and Wiley, B. J. NanoLetters, May 29, 2012.

Nanotechnology for for a sustainable process industry: Metal-free catalysts

Engineerblogger
May 27, 2012

Magnus Rønning, a professor in the Department of Chemical Engineering at the Norwegian University of Science and Technology, is head of a new EU funded effort to find metal-free catalysts.

The EU has awarded 4 million Euros to a new research project that will develop carbon materials to replace precious metals needed in catalysis. The research will help make the production of chemicals and commodities greener, while enabling the European process industry to keep its worldwide competitive edge. The project is called FREECATS - Doped carbon nanostructures as metal-free catalysts. Nine European research institutions and technology enterprises are working on the project, coordinated by the Norwegian University of Science and Technology (NTNU). Professor Magnus Rønning from the Catalysis group at the university's Department of Chemical Engineering is leading the effort, which started on 1 April 2012 and will last for three years.

A more sustainable process industry

Catalysis is one of the major consumers of precious metals, such as platinum. Catalysts affect the speed of chemical reactions, and are frequently used in the process industry. Platinum group metals are not generally found naturally in Europe. Metal-free catalysts that are based on carbon will lead to a significant reduction in the high demand for platinum group metals in Europe.

"Metal-free materials with catalysis properties that are equally as good as precious metals do not exist naturally, so FREECATS is aimed at developing new materials. Using nanotechnology, with atoms as building blocks, we can build carbon structures capable of binding or transforming substances in desired ways," says Magnus Rønning.

Carbon-based catalysis also offers environmental benefits. "Catalysts often contribute to parallel chemical reactions that may compete with the main reaction. Metal-free catalysts have a higher selectivity; they are more reliable in performing the reactions we want. This reduces the risk of reactions creating unwanted waste products that may be harmful to the environment," says Rønning.

Focus on fuel cell technology, olefin production and water purification

FREECATS has chosen to focus on three applications where metal-free catalysts can replace metal-based catalysts: fuel cell technology, the production of light olefins, and water purification.

Catalysts are used in fuel cells to initiate the process by which energy from fuel is converted to electricity in contact with oxygen. The energy produced by fuel cells emits low levels of greenhouse gases, but the method is expensive at present, partly because of costly materials.

Catalysts are used in the production of polyolefin materials to convert propane and ethane to light olefins. The demand for olefins is increasing globally. The existing use of platinum-based catalysts in production is not sustainable, because they are characterized by low selectivity and they are short-lived, costly and polluting.
Organic compounds in water can be oxidized or mineralized into harmless substances by means of catalysis. The method is used to remove bacteria, solvents, chemicals or fertilizers in waste water from industry and agriculture. Metal-free catalysts work just as well for water purification as metal-based catalysts, but they can make the process less expensive.

Source: The Norwegian University of Science and Technology

Device may inject a variety of drugs without using needles

Engineerblogger
May 27, 2012




Getting a shot at the doctor’s office may become less painful in the not-too-distant future.

MIT researchers have engineered a device that delivers a tiny, high-pressure jet of medicine through the skin without the use of a hypodermic needle. The device can be programmed to deliver a range of doses to various depths — an improvement over similar jet-injection systems that are now commercially available.

The researchers say that among other benefits, the technology may help reduce the potential for needle-stick injuries; the Centers for Disease Control and Prevention estimates that hospital-based health care workers accidentally prick themselves with needles 385,000 times each year. A needleless device may also help improve compliance among patients who might otherwise avoid the discomfort of regularly injecting themselves with drugs such as insulin.

“If you are afraid of needles and have to frequently self-inject, compliance can be an issue,” says Catherine Hogan, a research scientist in MIT’s Department of Mechanical Engineering and a member of the research team. “We think this kind of technology … gets around some of the phobias that people may have about needles.”

The team reports on the development of this technology in the journal Medical Engineering & Physics.

Pushing past the needle

In the past few decades, scientists have developed various alternatives to hypodermic needles. For example, nicotine patches slowly release drugs through the skin. But these patches can only release drug molecules small enough to pass through the skin’s pores, limiting the type of medicine that can be delivered.

With the delivery of larger protein-based drugs on the rise, researchers have been developing new technologies capable of delivering them — including jet injectors, which produce a high-velocity jet of drugs that penetrate the skin. While there are several jet-based devices on the market today, Hogan notes that there are drawbacks to these commercially available devices. The mechanisms they use, particularly in spring-loaded designs, are essentially “bang or nothing,” releasing a coil that ejects the same amount of drug to the same depth every time.

Breaching the skin

Now the MIT team, led by Ian Hunter, the George N. Hatsopoulos Professor of Mechanical Engineering, has engineered a jet-injection system that delivers a range of doses to variable depths in a highly controlled manner. The design is built around a mechanism called a Lorentz-force actuator — a small, powerful magnet surrounded by a coil of wire that’s attached to a piston inside a drug ampoule. When current is applied, it interacts with the magnetic field to produce a force that pushes the piston forward, ejecting the drug at very high pressure and velocity (almost the speed of sound in air) out through the ampoule’s nozzle — an opening as wide as a mosquito’s proboscis.

The speed of the coil and the velocity imparted to the drug can be controlled by the amount of current applied; the MIT team generated pressure profiles that modulate the current. The resulting waveforms generally consist of two distinct phases: an initial high-pressure phase in which the device ejects drug at a high-enough velocity to “breach” the skin and reach the desired depth, then a lower-pressure phase where drug is delivered in a slower stream that can easily be absorbed by the surrounding tissue.

Through testing, the group found that various skin types may require different waveforms to deliver adequate volumes of drugs to the desired depth.

“If I’m breaching a baby’s skin to deliver vaccine, I won’t need as much pressure as I would need to breach my skin,” Hogan says. “We can tailor the pressure profile to be able to do that, and that’s the beauty of this device.”

Samir Mitragotri, a professor of chemical engineering at the University of California at Santa Barbara, is developing new ways to deliver drugs, including via jet injection. Mitragotri, who was not involved with the research, sees the group’s technology as a promising step beyond jet injection designs currently on the market.

MIT-engineered device injects drug without needles, delivering a high-velocity jet of liquid that breaches the skin at the speed of sound.
Image courtesy of the MIT BioInstrumentation Lab

“Commercially available jet injectors … provide limited control, which limits their applications to certain drugs or patient populations,” Mitragotri says. “[This] design provides excellent control over jet parameters, including speed and doses … this will enhance the applicability of needleless drug devices.”

The team is also developing a version of the device for transdermal delivery of drugs ordinarily found in powdered form by programming the device to vibrate, turning powder into a “fluidized” form that can be delivered through the skin much like a liquid. Hunter says that such a powder-delivery vehicle may help solve what’s known as the “cold-chain” problem: Vaccines delivered to developing countries need to be refrigerated if they are in liquid form. Often, coolers break down, spoiling whole batches of vaccines. Instead, Hunter says a vaccine that can be administered in powder form requires no cooling, avoiding the cold-chain problem.

Source: MIT

Metamaterials: Researchers Design Mystifying Materials

Engineerblogger
May 27, 2012

Adilson E. Motter

It’s not magic, but new materials designed by two Northwestern University researchers seem to exhibit magical properties. Some contract when they should expand, and others expand when they should contract.

When tensioned, ordinary materials expand along the direction of the applied force. The new metamaterials (artificial materials engineered to have properties that may not be found in nature) do the opposite when tensioned -- they contract. Other materials designed by the researchers expand when compressed.

“Materials are networks of connected constituents, and when you apply tension or pressure, they can respond in surprising ways,” said Adilson E. Motter, the Harold H. and Virginia Anderson Professor of Physics and Astronomy at Northwestern’s Weinberg College of Arts and Sciences.

“Think of a piece of rod that you tension by pulling its ends with your fingers,” he said. “It would normally get longer, but for these materials it will get shorter.”

Motter and Zachary G. Nicolaou applied network concepts to design the new materials, all of which exhibit negative compressibility transitions. Their results are published this week in Nature Materials. Nicolaou, an undergraduate physics student at Northwestern when the work was done, now is a first-year graduate student at Caltech.

Different types of metamaterials already have led to interesting applications such as superlenses, visibility cloaks and acoustic shields. But no existing material or metamaterial was previously shown to exhibit negative compressibility transitions.

These metamaterials may enable new applications, including the development of new protective mechanical devices and actuators (a type of assembly for operating or controlling a system), and the enhancement of microelectromechanical systems.

The materials also exhibit force amplification, a phenomenon in which a small increase in deformation leads to an abrupt increase in the response force. The latter can be useful for the design of micro-mechanical controls, ratchets and force amplifiers.

All known materials deform along the direction of a constant applied force by expanding when they are tensioned and contracting when they are compressed. Owing to stability considerations, such contraction of a material in the same direction of an applied tension (in response to tension) cannot occur continuously. Possibly because of this, most people would intuitively expect that contraction in response to tension would be impossible.

The important point of the Northwestern study is that such a counter-intuitive response can occur discontinuously, namely, through something known by physicists as a phase transition. A familiar form of phase transition is the transformation of water into ice or vapor. Phase transitions allow for abrupt changes in the physical properties of a material. Yet, all conventional materials are such that phase transitions will lead to ordinary compressibility.

“This research shows that new materials, in fact, can be created to exhibit a phase transition during which the material undergoes contraction when tensioned or expansion when pressured,” Motter said. “We refer to such transformations as ‘negative compressibility transitions.’”

Materials with such properties have not been discovered in nature, but they can be constructed as metamaterials. Metamaterials are engineered materials that gain their properties from structure rather than composition. The relevant building blocks of such materials are not necessarily microscopic, atomic-sized objects, but may in fact be composed of a large number of atoms and hence be mesoscopic or macroscopic in size.

A key step for the discovery of the materials in this study was the representation of the material as a network of interacting particles.

“We were inspired by the observation that the realized equilibrium is not necessarily optimal in a decentralized network,” Motter said. “A conceptual precedent to this is the now 45-year-old insight from German mathematician Dietrich Braess that adding a road to a traffic network may increase rather than decrease the average travel time.”

Analogous effects also have been identified in physical networks, including an increase of current upon the removal of an intermediate conductor in electric networks. These are examples in which the equilibrium realized by the system can be brought closer to the optimum by constraining the structure of the network.

“Our materials are devised such that an analogous phenomenon occurs spontaneously, in response to a change in the external force rather than in the structure of the network,” Motter said.

Motter also is a faculty member in the department of engineering sciences and applied mathematics at the McCormick School of Engineering and Applied Science and an executive committee member of the Northwestern Institute on Complex Systems (NICO).

The Materials Research Science and Engineering Center at Northwestern University and the National Science Foundation supported the research.


Source: Northwestern University

Additional Information:  

• Mechanical Metamaterials With Negative Compressibility Transitions

Taking Solar Technology up a Notch: New Solar Cell Shines with Potential

Engineerblogger
May 27, 2012

Robert Chang

The limitations of conventional and current solar cells include high production cost, low operating efficiency and durability, and many cells rely on toxic and scarce materials. Northwestern University researchers have developed a new solar cell that, in principle, will minimize all of these solar energy technology limitations.

In particular, the device is the first to solve the problem of the Grätzel cell, a promising low-cost and environmentally friendly solar cell with a significant disadvantage: it leaks. The dye-sensitized cell’s electrolyte is made of an organic liquid, which can leak and corrode the solar cell itself.

Grätzel cells use a molecular dye to absorb sunlight and convert it to electricity, much like chlorophyll in plants. But the cells typically don’t last more than 18 months, making them commercially unviable. Researchers have been searching for an alternative for two decades.

At Northwestern, where interdisciplinary collaboration is a cornerstone, nanotechnology expert Robert P. H. Chang challenged chemist Mercouri Kanatzidis with the problem of the Grätzel cell. Kanatzidis’ solution was a new material for the electrolyte that actually starts as a liquid but ends up a solid mass. Thus, the new all solid-state solar cell is inherently stable.

“The Grätzel cell is like having the concept for the light bulb but not having the tungsten wire or carbon material,” said Kanatzidis, of the need to replace the troublesome liquid. “We created a robust novel material that makes the Grätzel cell concept work better. Our material is solid, not liquid, so it should not leak or corrode.”

Postdoctoral fellow In Chung in the Kanatzidis group worked closely with graduate student Byunghong Lee in the Chang group to develop the new cells, achieving performance gains that amounted to approximately 1 percent per month.

In the Northwestern cell, a thin-film compound made up of cesium, tin and iodine, called CsSnI3, replaces the entire liquid electrolyte of the Grätzel cell. Details of the new solar cell -- an efficient, more stable and longer lasting cell -- will be published May 24 by the journal Nature.

Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, and Chang, a professor of materials science and engineering at the McCormick School of Engineering and Applied Science, are the two senior authors of the paper.

“This is the first demonstration of an all solid-state dye-sensitized solar cell system that promises to exceed the performance of the Grätzel cell,” Chang said. “Our work opens up the possibility of these materials becoming state of the art with much higher efficiencies than we’ve seen so far.”

The Northwestern cell exhibits the highest conversion efficiency (approximately 10.2 percent) so far reported for a solid-state solar cell equipped with a dye sensitizer. This value is close to the highest reported performance for a Grätzel cell, approximately 11 to 12 percent. (Conventional solar cells made from highly purified silicon can convert roughly 20 percent of incoming sunlight.)

Unlike the Grätzel cell, the new solar cell uses both n-type and p-type semiconductors and a monolayer dye molecule serving as the junction between the two. Each nearly spherical nanoparticle, made of titanium dioxide, is an n-type semiconductor. Kanatzidis’ CsSnI3 thin-film material is a new kind of soluble p-type semiconductor.

“Our inexpensive solar cell uses nanotechnology to the hilt,” Chang said. “We have millions and millions of nanoparticles, which gives us a huge effective surface area, and we coat all the particles with light-absorbing dye.”

A single solar cell measures half a centimeter by half a centimeter and about 10 microns thick. The dye-coated nanoparticles are packed in, and Kanatzidis’ new material, which starts as a liquid, is poured in, flowing around the nanoparticles. Much like paint, the solvent evaporates, and a solid mass results. The sunlight-absorbing dye, where photons are converted into electricity, lies right between the two semiconductors.

Chang chose to use nanoparticles approximately 20 nanometers in diameter. This size optimizes the device, he said, increasing the surface area and allowing enough space between the particles for Kanatzidis’ material to flow through and set.

Technically, this new cell is not really a Grätzel cell since the hole-conducting material CsSnI3 is itself light absorbing. In fact, the material absorbs more light over a wider range of the visible spectrum than the typical dye used in Grätzel cells. In the Kanatzidis-Chang cell, the CsSnI3 plays an additional role in the operation of the cell that is not played by the liquid electrolyte couple, and that role is light absorption.

“This is only the beginning,” Chang said. “Our concept is applicable to many types of solar cells. There is a lot of room to grow.”

The lightweight thin-film structures are compatible with automated manufacturing, the researchers point out. They next plan to build a large array of the solar cells.

The paper is titled “All-Solid-State Dye-Sensitized Solar Cells With High Efficiency.” In addition to Kanatzidis, Chang, Chung and Lee, the other author of the paper is Jiaqing He, from Northwestern.

The National Science Foundation, the U.S. Department of Energy and the Initiative for Energy and Sustainability at Northwestern (ISEN) supported the research.
Source:  Northwestern University

Additional Information:

• All-solid-state dye-sensitized solar cells with high efficiency

Microreactors to produce explosive materials

Engineerblogger
May 27, 2012

Microreactors can e.g. be used to produce explosive materials much more safely. © Fraunhofer ICT

The larger the reaction vessel, the quicker products can be made – or so you might think. Microreactors show just how wrong that assumption is: in fact, they can be used to produce explosive materials – nitroglycerine, for instance – around ten times faster than in conventional vessels, and much more safely as well. At the ACHEMA trade fair, held June 18-22 in Frankfurt, researchers will demonstrate microreactors they use for a very broad range of chemical processes.

If the task is to tunnel through a mountain, workers turn to explosives: the 15-kilometer-long Gotthard Tunnel, for instance, was created by blasting through the rock with explosive gelatin made largely out of the nitroglycerine – better-known as dynamite. Producing these explosives calls for extreme caution. After all, no one wants a demonstration of explosive force in the lab. Because the production process generates heat, it must proceed slowly: drop for drop, the reagents are added to the agitating vessel that holds the initial substance. A mixture that heats up too suddenly can cause an explosion. The heat generated cannot be permitted to exceed the heat dissipated.

Researchers at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal have developed a method for safer production of nitroglycerine: a microreactor process, tailored to this specific reaction. What makes the process safer are the tiny quantities involved. If the quantities are smaller, less heat is generated. And because the surface is very expansive compared to the volume involved, the system is very easy to cool. Another benefit: the tiny reactor produces the explosive material considerably faster than in agitating vessels. Unlike a large agitating vessel filled before the slow reaction proceeds, the microreactor works continuously: the base materials flow through tiny channels into the reaction chamber in “assembly-line fashion“. There, they react with one another for several seconds before flowing through other channels into a second microreactor for processing – meaning purification. This is because the interim product still contains impurities that need to be removed for safety reasons. Purification in the microreactor functions perfectly: the product produced meets pharmaceutical specifications and in a modified form can even be used in nitro capsules for patients with heart disease. “This marks the first use of microreactors in a process not only for synthesis of a material but also for its subsequent processing,“ observes Dr. Stefan Löbbecke, deputy division director at ICT. The microreactor process is already successfully in use in industry.

When developing a microreactor, researchers match the reactors to the reaction desired: how large may the channels be to ensure that the heat generated can be dissipated effectively? Where do researchers need to build impediments into the channels to ensure that the fluids are well blended and the reaction proceeds as planned? Another important parameter is the speed with which the liquids flow through the channels: on the one hand, they need enough time to react with one another, while on the other the reaction should come to an end as soon as the product is formed. Otherwise, the result might be too many unwanted by-products.

While microreactors suggest themselves for explosive materials, this is not the only conceivable application: researchers at ICT build reactors for every chemical reaction conceivable – and each is tailored to the particular reaction involved. Just one of numerous other examples is a microreactor that produces polymers for OLEDs. OLEDs are organic light-emitting diodes that are particularly common in displays and monitors. The polymers of which the OLEDs are made light up in colors. Still, when they are produced – synthesized – imperfections easily arise that rob the polymers of some of their luminosity. “Through precise process management, we are able to minimize the number of these imperfections,“ Löbbecke points out. To accomplish this, researchers first analyzed the reaction in minute detail: When do the polymers form? When do the imperfections arise? How fast does the process need to be? “As it turns out, many of the reaction protocol that people are familiar with from batch processes are unnecessary. Often, the base materials don‘t need to boil for hours at a time; in many cases all it takes is a few seconds,“ the researcher has found. Long periods spent boiling can cause the products to decompose or generate unwanted byproducts.

To develop and perfect a microreactor for a new reaction, the researchers study the ongoing reaction in real time – peering into the reactor itself, so to speak. Various analytical procedures are helpful in this regard: some, such as spectroscopic techniques, reveal which kinds of products are created in the reactor – and thus how researchers can systematically increase yields of the desired product, possibly even preventing by products from forming in the first place. Other analytical methods, such as calorimetry, provide scientists with information about the heat released over the course of a reaction. This measurement method tells them how quickly and completely the reaction is proceeding. It also provides an indication of how the process conditions need to be selected to ensure that the reaction proceeds safely. Researchers will be presenting a variety of microreactors, microreactor processes and process-analytical techniques at the ACHEMA trade fair from June 18-22 in Frankfurt.

Source: Fraunhofer-Gesellschaft

Bright future for solar power in space

Engineerblogger
May 19, 2012

Dr Massimiliano Vasile

Solar power gathered in space could be set to provide the renewable energy of the future thanks to innovative research being carried out by engineers at the University of Strathclyde, Glasgow.


Researchers at the University have already tested equipment in space that would provide a platform for solar panels to collect the energy and allow it to be transferred back to earth through microwaves or lasers.

This unique development would provide a reliable source of power and could allow valuable energy to be sent to remote areas in the world, providing power to disaster areas or outlying areas that are difficult to reach by traditional means.

Dr Massimiliano Vasile, of the University of Strathclyde’s Department of Mechanical and Aerospace Engineering, who is leading the space based solar power research, said: “Space provides a fantastic source for collecting solar power and we have the advantage of being able to gather it regardless of the time of the day or indeed the weather conditions.

“In areas like the Sahara desert where quality solar power can be captured, it becomes very difficult to transport this energy to areas where it can be used. However, our research is focusing on how we can remove this obstacle and use space based solar power to target difficult to reach areas.

“By using either microwaves or lasers we would be able to beam the energy back down to earth, directly to specific areas. This would provide a reliable, quality source of energy and would remove the need for storing energy coming from renewable sources on ground as it would provide a constant delivery of solar energy.

“Initially, smaller satellites will be able to generate enough energy for a small village but we have the aim, and indeed the technology available, to one day put a large enough structure in space that could gather energy that would be capable of powering a large city.”

Last month, a team of science and engineering students at Strathclyde developed an innovative ‘space web’ experiment which was carried on a rocket from the Arctic Circle to the edge of space.

The experiment, known as Suaineadh – or ‘twisting’ in Scots Gaelic, was an important step forward in space construction design and demonstrated that larger structures could be built on top of a light-weight spinning web, paving the way for the next stage in the solar power project.

Dr Vasile added: “The success of Suaineadh allows us to move forward with the next stage of our project which involves looking at the reflectors needed to collect the solar power.

“The current project, called SAM (Self-inflating Adaptable Membrane) will test the deployment of an ultra light cellular structure that can change shape once deployed. The structure is made of cells that are self-inflating in vacuum and can change their volume independently through nanopumps.

“The structure replicates the natural cellular structure that exists in all living things. The independent control of the cells would allow us to morph the structure into a solar concentrator to collect the sunlight and project it on solar arrays. The same structure can be used to build large space systems by assembling thousands of small individual units.”

The project is part of a NASA Institute for Advanced Concepts (NIAC) study led by Dr John Mankins of Artemis Innovation. The University of Strathclyde represents the European section of an international consortium involving American researchers, and a Japanese team, led by Professor Nobuyuki Kaya of the University of Kobe, a world leader in wireless power transmission.

The NIAC study is demonstrating a new conceptual design for large scale solar power satellites. The role of the team at the University of Strathclyde is to develop innovative solutions for the structural elements and new solutions for orbit and orbit control.

Source: University of Strathclyde

Additional Information:

• Advanced Space Concepts Laboratory
• Centre for Future Air-Space Transportation Technology (cFASTT)
• Suaineadh

Prosthetic retina offers simple solution to restoring sight

Engineerblogger
May 19, 2012

Credit: University of Strathclyde

A device which could restore sight to patients with one of the most common causes of blindness in the developed world is being developed in an international partnership.

Researchers from the University of Strathclyde and Stanford University in California are creating a prosthetic retina for patients of age related macular degeneration (AMD), which affects one in 500 patients aged between 55 and 64 and one in eight aged over 85.

The device would be simpler in design and operation than existing models. It acts by electrically stimulating neurons in the retina, which are left relatively unscathed by the effects of AMD while other ‘image capturing’ cells, known as photoreceptors, are lost.

It would use video goggles to deliver energy and images directly to the eye and be operated remotely via pulsed near infra-red light- unlike most prosthetic retinas, which are powered through coils that require complex surgery to be implanted.

The prosthetic retina is a thin silicon device that converts pulsed near infra-red light to electrical current that stimulates the retina and elicits visual perception. It requires no wires and would make surgical implantation simpler.

The device has been shown to produce encouraging responses in initial lab tests and is reported in an article published in Nature Photonics. The technology is now being developed further.

Credit: University of Strathclyde

Dr Keith Mathieson, now a Reader in the Institute of Photonics at the University of Strathclyde in Glasgow, was one of the lead researchers and first author of the paper. He said: “AMD is a huge medical challenge and, with an aging population, is continuing to grow. This means that innovative, practical solutions are essential if sight is to be restored to people around the world with the condition.

“The prosthetic retina we are developing has been partly inspired by cochlear implants for the ear but with a camera instead of a microphone and, where many cochlear implants have a few channels, we are designing the retina to deal with millions of light sensitive nerve cells and sensory outputs.

“The implant is thin and wireless and so is easier to implant. Since it receives information on the visual scene through an infra-red beam projected through the eye, the device can take advantage of natural eye movements that play a crucial role in visual processing.”

The research was co-authored by Dr. Jim Loudin of Stanford and led by Professor Daniel Palanker, also of Stanford, and Professor Alexander Sher, of the University of California, Santa Cruz.

Professor Palanker said: "The current implants are very bulky, and the surgery to place the intraocular wiring for receiving, processing and power is difficult. With our device, the surgeon needs only to create a small pocket beneath the retina and then slip the photovoltaic cells inside it."

Dr Mathieson was supported through a fellowship from SU2P, a venture between academic institutions in Scotland and California aimed at extracting economic impact from their joint research portfolio in photonics and related technologies.

Strathclyde leads the collaboration, which also includes Stanford, the Universities of St Andrews, Heriot-Watt and Glasgow and the California Institute of Technology. SU2P was established through funding from Research Councils UK- as part of its Science Bridges awards- the Scottish Funding Council and Scottish Enterprise.

The research links to Photonics and Health Technologies at Strathclyde- two of the principal themes of the University’s Technology and Innovation Centre (TIC), a world-leading research and technology centre transforming the way universities, business, and industry collaborate.

Through Health Technologies at Strathclyde, academics work with industry and the health sector to find technologies for earlier, more accurate disease detection and better treatments, as well as life-long disease prevention.

Source: University of Strathclyde 

Additional Information:

• Read the article in Nature Photonics
• Institute of Photonics
• SU2P

DARPA Collaboration Offers Hope to People with Tetraplegia

Engineerblogger
May 19, 2012

Momentum builds behind upper-limb prosthetic technology as researchers demonstrate direct neural control of an advanced prosthetic arm

DARPA launched the Revolutionizing Prosthetics program in 2006 to advance the state of upper-limb prosthetic technology with the goals of improving quality of life for service-disabled veterans and ultimately giving them the option of returning to duty. Since then, Revolutionizing Prosthetics teams have developed two anthropomorphic advanced modular prototype prosthetic arm systems, including sockets, which offer increased range of motion, dexterity and control options. Through DARPA-funded work and partnerships with external researchers, the arm systems and supporting technology continue to advance.

In a recent development reported in the May 17 issue of Nature, researchers at Providence VA Medical Center, Brown University and Massachusetts General Hospital demonstrated the ability to control an advanced prosthetic arm using a direct neural interface system in humans with brainstem stroke. The BrainGate research team was led by Drs. John Donoghue and Leigh Hochberg, VA researchers and professors at Brown and Brown/Harvard respectively, through funding from the Department of Veterans Affairs. This project featured collaboration with the National Institutes of Health, who provided additional funding, and the Defense Advanced Research Projects Agency, who provided a Generation 2 advanced prosthetic arm developed by DEKA under DARPA’s Revolutionizing Prosthetics program. Microelectrode arrays were implanted in the motor cortex of the brains of two tetraplegic patients. With minimal prior use, the patients were able to control the arm in three-dimensional space and perform reach and grasp tasks.

Source: Defense Advanced Research Projects Agency(DARPA)

Additional Information:

• Revolutionizing Prosthetics

Direct Digital: Novel Casting Process Could Transform How Complex Metal Parts Are Made

Engineerblogger
May 19, 2012

Image shows a collection of molds made through the large area maskless photopolymerization (LAMP) technology and airfoil components produced using them. Credit: Gary Meek

A Georgia Tech research team has developed a novel technology that could change how industry designs and casts complex, costly metal parts. This new casting method makes possible faster prototype development times, as well as more efficient and cost-effective manufacturing procedures after a part moves to mass production.

Suman Das, a professor in the George W. Woodruff School of Mechanical Engineering, has developed an all-digital approach that allows a part to be made directly from its computer-aided design (CAD). The project, sponsored by the Defense Advanced Research Projects Agency (DARPA), has received $4.65 million in funding.

“We have developed a proof-of-concept system which is already turning out complex metal parts, and which fundamentally transforms the way that very high-value castings are made,” said Das, who directs the Direct Digital Manufacturing Laboratory in Georgia Tech’s Manufacturing Research Center (MaRC). “We’re confident that our approach can lower costs by at least 25 percent and reduce the number of unusable waste parts by more than 90 percent, while eliminating 100 percent of the tooling.”

The approach being utilized by Das and his team focuses on a technique called investment casting, also known as lost-wax casting. In this process, which dates back thousands of years, molten metal is poured into an expendable ceramic mold to form a part.

The mold is made by creating a wax replica of the part to be cast, surrounding or “investing” the replica with a ceramic slurry, and then drying the slurry and hardening it to form the mold. The wax is then melted out – or lost – to form a mold cavity into which metal can be poured and solidified to produce the casting.

Today, Das explained, most precision metal castings are designed on computers, using computer-aided design software. But the next step – creating the ceramic mold with which the part is cast – currently involves a sequence of six major operations requiring expensive precision-machined dies and hundreds of tooling pieces.

“The result is a costly process that typically produces many defective molds and waste parts before a useable prototype is achieved,” Das said. “This trial-and-error development phase often requires many months to cast a part that is accurate enough to enter the next stage, which involves testing and evaluation.”

By contrast, Das’s approach involves a device that builds ceramic molds directly from a CAD design, completing the task much faster and producing far fewer unusable parts. Called Large Area Maskless Photopolymerization (LAMP), this high-resolution digital process accretes the mold layer by layer by projecting bitmaps of ultraviolet light onto a mixture of photosensitive resin and ceramic particles, and then selectively curing the mixture to a solid.

The technique places one 100-micron layer on top of another until the structure is complete. After the mold is formed, the cured resin is removed through binder burnout and the remaining ceramic is sintered in a furnace. The result is a fully ceramic structure into which molten metal – such as nickel-based superalloys or titanium-based alloys – are poured, producing a highly accurate casting.

“The LAMP process lowers the time required to turn a CAD design into a test-worthy part from a year to about a week,” Das said. “We eliminate the scrap and the tooling, and each digitally manufactured mold is identical to the others.”

A prototype LAMP alpha machine is currently building six typical turbine-engine airfoil molds in six hours. Das predicts that a larger beta machine – currently being built at Georgia Tech and scheduled for installation at a PCC Airfoils facility in Ohio in 2012 – will produce 100 molds at a time in about 24 hours.

Although the current work focuses on turbine-engine airfoils, Das believes the LAMP technique will be effective in the production of many types of intricate metal parts. He envisions a scenario in which companies could send out part designs to digital foundries and receive test castings within a short time, much as integrated-circuit designers send CAD plans to chip foundries today.

Moreover, he said, direct digital manufacturing enabled by LAMP should allow designers to create increasingly sophisticated pieces capable of achieving greater efficiency in jet engines and other systems.

“This process can produce parts of a complexity that designers could only dream of before,” he said. “The digital technique takes advantage of high-resolution optics and precision motion systems to achieve extremely sharp, small features – on the order of 100 microns.”

Das also noted that the new process not only creates testable prototypes but could also be used in the actual manufacturing process. That would allow more rapid production of complex metal parts, in both low and high volumes, at lower costs in a variety of industries.

“When you can produce desired volumes in a short period without tooling,” he said, “you have gone beyond rapid prototyping to true rapid manufacturing.”

The project depicted in this article is sponsored by the Defense Advanced Research Projects Agency(DARPA).

Source: Georgia Institute of Technology