Successful First Test Drive of 'Sighted' Wheelchair

The wheelchair has a joystick for steering and a haptic robot that acts as a virtual white cane. With the help of a laser scanner a simplified 3D map is created of the wheelchair surroundings. The laser scanner uses Time-of-flight technique. The 3D map is transferred to the haptic robot so that a visually impaired wheelchair driver can"feel or see" obstacles such as open doors or oncoming people, and navigate past them.

The"sighted" wheelchair has been developed by Kalevi Hyyppä, a professor at Luleå University of Technology and his research team at the LTU division EISLAB. The other members of the research team are prospective Ph.D. student Daniel Innala Ahlmark, assistant professor Håkan Fredriksson and Ph.D. student Fredrik Broström.

"This may be important aids for the visually impaired who are wheelchair users. Many have already been in touch with me and asked if they can come for a test drive," says Kalevi Hyyppä.

The first test of the"sighted" wheelchair for an audience was carried out in one of the corridors of the Department of Computer Science, Electrical- and Space Engineering at Luleå University of Technology.

There are several classrooms in the corridor, which means that students often pass there. For those who are visually impaired or blind, it is quite a changing environment to move in. Daniel Innala Ahlmark, who is visually impaired, dared to test the wheelchair while explaining how he experienced it -- and he did so before the entire local and even national media in Sweden.

"I feel safe when I run it, it is like using a white cane," he said as he avoided various obstacles along the corridor.

There is much left when it comes to improving the 3D sensor and the haptic robot. The laser beam that sweeps in front of the wheelchair hits only objects which are a certain height. It has not the capacity to see things that are higher or lower than that height. Now the research team plan to develop a 3D camera that can do a full 3D measurement. Then the sighted wheelchair can be manufactured and used for real. This might be possible in approximately five years.

Research on the sighted wheelchair has been made with funding from the European Regional Structural Fund Northern Sweden.

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Super Energy Storage: Activated Graphene Makes Superior Supercapacitors for Energy Storage

"Those properties make this new form of carbon particularly attractive for meeting electrical energy storage needs that also require a quick release of energy -- for instance, in electric vehicles or to smooth out power availability from intermittent energy sources, such as wind and solar power," said Brookhaven materials scientist Eric Stach, a co-author on a paper describing the material published inScienceon May 12, 2011.

Supercapacitors are similar to batteries in that both store electric charge. Batteries do so through chemical reactions between metallic electrodes and a liquid electrolyte. Because these chemicals take time to react, energy is stored and released relatively slowly. But batteries can store a lot of energy and release it over a fairly long time.

Supercapacitors, on the other hand, store charge in the form of ions on the surface of the electrodes, similar to static electricity, rather than relying on chemical reactions. Charging the electrodes causes ions in the electrolyte to separate, or polarize, as well -- so charge gets stored at the interface between the electrodes and the electrolyte. Pores in the electrode increase the surface area over which the electrolyte can flow and interact -- increasing the amount of energy that can be stored.

But because most supercapacitors can't hold nearly as much charge as batteries, their use has been limited to applications where smaller amounts of energy are needed quickly, or where long life cycle is essential, such as in mobile electronic devices.

The new material developed by the UT-Austin researchers may change that. Supercapacitors made from it have an energy-storage capacity, or energy density, that is approaching the energy density of lead-acid batteries, while retaining the high power density -- that is, rapid energy release -- that is characteristic of supercapacitors.

"This new material combines the attributes of both electrical storage systems," said University of Texas team leader Rodney Ruoff."We were rather stunned by its exceptional performance."

The UT-Austin team had set out to create a more porous form of carbon by using potassium hydroxide to restructure chemically modified graphene platelets -- a form of carbon where the atoms are arrayed in tile-like rings laying flat to form single-atom-thick sheets. Such"chemical activation" has been previously used to create various forms of"activated carbon," which have pores that increase surface area and are used in filters and other applications, including supercapacitors.

But because this new form of carbon was so superior to others used in supercapacitors, the UT-Austin researchers knew they'd need to characterize its structure at the nanoscale.

Ruoff had formed a hypothesis that the material consisted of a continuous three-dimensional porous network with single-atom-thick walls, with a significant fraction being"negative curvature carbon," similar to inside-out buckyballs. He turned to Stach at Brookhaven for help with further structural characterization to verify or refute this hypothesis.

Stach and Brookhaven colleague Dong Su conducted a wide range of studies at the Lab's Center for Functional Nanomaterials, the National Synchrotron Light Source, and at the National Center for Electron Microscopy at Lawrence Berkeley National Laboratory, all three facilities supported by the DOE Office of Science."At the DOE laboratories, we have the highest resolution microscopes in the world, so we really went full bore into characterizing the atomic structure," Stach said.

"Our studies revealed that Ruoff's hypothesis was in fact correct, and that the material's three-dimensional nanoscale structure consists of a network of highly curved, single-atom-thick walls forming tiny pores with widths ranging from 1 to 5 nanometers, or billionths of a meter."

The study includes detailed images of the fine pore structure and the carbon walls themselves, as well as images that show how these details fit into the big picture."The data from NSLS were crucial to showing that our highly local characterization was representative of the overall material," Stach said.

"We're still working with Ruoff and his team to pull together a complete description of the material structure. We're also adding computational studies to help us understand how this three-dimensional network forms, so that we can potentially tailor the pore sizes to be optimal for specific applications, including capacitive storage, catalysis, and fuel cells," Stach said.

Meanwhile, the scientists say the processing techniques used to create the new form of carbon are readily scalable to industrial production."This material -- being so easily manufactured from one of the most abundant elements in the universe -- will have a broad range impacts on research and technology in both energy storage and energy conversion," Ruoff said.

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Toward Faster Transistors: Physicists Discover Physical Phenomenon That Could Boost Computers' Clock Speed

In this week's issue of the journalScience,MIT researchers and their colleagues at the University of Augsburg in Germany report the discovery of a new physical phenomenon that could yield transistors with greatly enhanced capacitance -- a measure of the voltage required to move a charge. And that, in turn, could lead to the revival of clock speed as the measure of a computer's power.

In today's computer chips, transistors are made from semiconductors, such as silicon. Each transistor includes an electrode called the gate; applying a voltage to the gate causes electrons to accumulate underneath it. The electrons constitute a channel through which an electrical current can pass, turning the semiconductor into a conductor.

Capacitance measures how much charge accumulates below the gate for a given voltage. The power that a chip consumes, and the heat it gives off, are roughly proportional to the square of the gate's operating voltage. So lowering the voltage could drastically reduce the heat, creating new room to crank up the clock.

MIT Professor of Physics Raymond Ashoori and Lu Li, a postdoc and Pappalardo Fellow in his lab -- together with Christoph Richter, Stefan Paetel, Thilo Kopp and Jochen Mannhart of the University of Augsburg -- investigated the unusual physical system that results when lanthanum aluminate is grown on top of strontium titanate. Lanthanum aluminate consists of alternating layers of lanthanum oxide and aluminum oxide. The lanthanum-based layers have a slight positive charge; the aluminum-based layers, a slight negative charge. The result is a series of electric fields that all add up in the same direction, creating an electric potential between the top and bottom of the material.

Ordinarily, both lanthanum aluminate and strontium titanate are excellent insulators, meaning that they don't conduct electrical current. But physicists had speculated that if the lanthanum aluminate gets thick enough, its electrical potential would increase to the point that some electrons would have to move from the top of the material to the bottom, to prevent what's called a"polarization catastrophe." The result is a conductive channel at the juncture with the strontium titanate -- much like the one that forms when a transistor is switched on. So Ashoori and his collaborators decided to measure the capacitance between that channel and a gate electrode on top of the lanthanum aluminate.

They were amazed by what they found: Although their results were somewhat limited by their experimental apparatus, it may be that an infinitesimal change in voltage will cause a large amount of charge to enter the channel between the two materials."The channel may suck in charge -- shoomp! Like a vacuum," Ashoori says."And it operates at room temperature, which is the thing that really stunned us."

Indeed, the material's capacitance is so high that the researchers don't believe it can be explained by existing physics."We've seen the same kind of thing in semiconductors," Ashoori says,"but that was a very pure sample, and the effect was very small. This is a super-dirty sample and a super-big effect." It's still not clear, Ashoori says, just why the effect is so big:"It could be a new quantum-mechanical effect or some unknown physics of the material."

There is one drawback to the system that the researchers investigated: While a lot of charge will move into the channel between materials with a slight change in voltage, it moves slowly -- much too slowly for the type of high-frequency switching that takes place in computer chips. That could be because the samples of the material are, as Ashoori says,"super dirty"; purer samples might exhibit less electrical resistance. But it's also possible that, if researchers can understand the physical phenomena underlying the material's remarkable capacitance, they may be able to reproduce them in more practical materials.

Triscone cautions that wholesale changes to the way computer chips are manufactured will inevitably face resistance."So much money has been injected into the semiconductor industry for decades that to do something new, you need a really disruptive technology," he says.

"It's not going to revolutionize electronics tomorrow," Ashoori agrees."But this mechanism exists, and once we know it exists, if we can understand what it is, we can try to engineer it."

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Lasers Take the Lead in Auto Manufacturing

The era of gas guzzlers that clatter through streets and pollute the air is over. Cars rolling off the assembly line today are cleaner, quieter and -- in terms of their performance weight -- more efficient than ever before. Nevertheless, development continues. Ever-stricter environmental regulations and steadily rising fuel costs are increasing the demand for cars that further reduce their impact on the environment. But customer demands are often tough for manufacturers to meet: car bodies should be safe yet light-weight and engines durable yet efficient. Year after year, new models must be developed and built that can claim to be better, more efficient, and more intelligent than the last.

The race against time and competitors places high demands on manufacturers and their suppliers. Lasers can help them win the race. Resistant to wear and universally applicable, laser light is an ideal tool in the manufacture of vehicles. Lasers can be used to join, drill, structure, cut or shape any kind of material. Surfaces can be engineered for motors and drive trains that create less friction and use less fuel. Lasers are not only a decisive key towards faster, more efficient and economical production, but also towards energy-saving vehicles. At Laser 2011, Fraunhofer scientists will demonstrate how we can use lasers to save time, money and energy.

A weight-loss program in automotive manufacturing

Extra pounds cost energy. They have to be accelerated and slowed down every time you drive -- over the entire lifespan of the car. To reduce weight, manufacturers are increasingly turning to the use of fiber-reinforced plastics, which are 30 to 50 percent lighter than metal. The disadvantage, however, is that these new materials are difficult to process. Fiber-reinforced plastics are brittle, meaning cutting and drilling tools are quickly worn out and the conventional assembly techniques used for metal components are often not appropriate."Lasers represent an ideal alternative here," explains Dr. Arnold Gillner of the Fraunhofer Institute for Laser Technology ILT in Aachen."Lasers can cut fiber-reinforced plastics without wear and can join them too. With the appropriate lasers, we can cut and ablate components with minimal thermal side-effects. Lasers can also be used for welding light-weight components -- a viable alternative to conventional bonding technology. We can even join fiber-reinforced plastics to metals with laser welding. The laser roughens the metal surface, while the plastic, briefly-heated, penetrates the pores of the metal and hardens. The results are very stable."

Weight reduction can also be achieved with high-strength metallic materials. These, however, are difficult to process."Joining combinations of various materials allows us to make optimal use of the individual materials' specific properties. But this proves to be difficult in many cases," explains Dr. Anja Techel, Deputy Director of the Fraunhofer Institute for Material and Beam Technology IWS in Dresden. Her team believes in lasers:"With our newly-developed integrated laser tools, we can now even weld together combinations of materials, free of fissures or cracks." At Laser 2011, Fraunhofer scientists will present, for the first time, a new welding head capable not only of focusing with extreme precision but of moving back and forth across the seam with high frequency to mix the molten materials. When they harden, they create a stable bond.

Laser replaces chemistry

Lasers also save time and money in tool design. The molds used in the production of plastic fixtures and steering wheels, for example, have to be structured to give the finished component a visually and tactilely appealing surface. Most car manufacturers order a design from their suppliers, whose surface typically has the appearance of leather. Until now, the negative pattern used to create the design has been etched out of the steel tools used in injection molding -- a tedious and time-consuming process."With lasers, the steel surface can not only be patterned more quickly, but also with greater scope for variety," explains Kristian Arntz of the Fraunhofer Institute for Production Technology IPT."We can transfer any possible design directly from the CAD model to the tool surface: What will later become a groove in the plastic is preserved as a ridge, while the surrounding material is vaporized. The process is efficient, fully automatic, and highly variable."

Saving energy with low friction motors

Laser technology is also in demand in engine optimization. Engineers strive to keep friction as low as possible in order to improve efficiency."That is true not only for the electric engines currently being developed, but also for classic internal combustion engines and diesel motors, as well as transmissions and bearings," says Arnold Gillner of the ILT. Ceramic, high-performance coatings are especially desirable, because they are not only resistant to wear but also smooth, which generates less friction. Coated metal components have until now been prohibitively expensive, being produced in plasma chambers in which the ceramic was vaporized and applied to the surface of the components. Fraunhofer scientists have now developed a less expensive and faster method in which work pieces are coated with ceramic nano-particles, then treated with a laser. This finishing process has already been applied to gear wheels and bearings.

Lasers can even be used to make specific modifications to the properties of engine parts."Friction between the cylinder wall and piston is responsible for a big part of a motor's energy consumption. That is why we try to minimize it. This is especially important for engines featuring modern, automatic start-stop functions that are stressed by frequent ignition," says Gillner."To protect them, we have to ensure that the cylinder is always coated with a film of oil. Laser technology can help reduce friction with special structuring processes that improve oil adhesion." Fraunhofer researchers aim to increase the engine's life-span and reduce energy consumption in this way.

Fitness program for electric cars

Lasers can even increase the efficiency and life-span of electric batteries. That is good news for manufacturers and owners of electric cars, since batteries continue to be extremely expensive. The engineers and scientists at Fraunhofer are currently working on various solutions to make batteries more durable and less expensive. One approach is to increase the surface area of the electrodes with appropriate coating in order to increase their efficiency. Another approach involves analyzing and optimizing production processes.

Manufacturers produce batteries using one anode and one cathode cell, which they then connect. In theory that sounds pretty simple, but in practice the fusing of copper anodes with aluminum cathodes creates brittle connections that break easily. That presents a problem for application in cars that sometimes drive on cobblestone or dirt roads. With the help of lasers, researchers at the ILT have succeeded in forming durable connections between electrodes without creating the culprit brittle alloys. Researchers at the IWS in Dresden have developed an alternative solution in which a laser warms the surfaces and rollers press them together."Using roll plating with lasers and inductive pre-heating, we were able to create very stable connections with high electrical conductivity, with only a minimal loss of power," reports Anja Techel."The finished batteries are very efficient. And since only small amounts of electrical energy are transformed into heat, these batteries do not require as much cooling."

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Finding Reserves on the Electrical Grid

When storms lash northern and eastern Germany, it regularly gets tight in the high-voltage and highest-voltage electrical grids. Electricity from renewable resources has priority on the grid. But, on stormy days in particular, wind turbine systems must be taken offline, because the gird capacities are insufficient."Currently we are in a situation where we have high inflows from renewable energies into our high voltage line system and are expecting large increases in the future. However, the grid is not designed for this level of energy feed," reports Hanjo During of envia Verteilnetz GmbH in Halle, Germany, Additional power lines are being planned. But the authorization processes could take years and very often fail due to the resistance of the people living near the projected path of the lines.

For this reason, the grid operators are already utilizing various line-monitoring procedures to increase the grid capacity over the short term: They utilize reserves that are the result of a standardized assumption regarding the worst weather conditions for operating the line and the actual state of the line. In favorable weather conditions, they were therefore able to increase the transmission capacities by 20 percent or more. Currently, Amprion and envia Verteilnetz are testing a new type of autonomously powered sensor network to monitor 110 kV and 380 kV lines. It is being developed jointly with the Fraunhofer Institutes for Reliability and Microintegration IZM in Berlin and Electronic Nanosystems ENAS in Chemnitz, Germany as well as other research and industrial partners in the"ASTROSE" project."Our autonomously powered sensor network can be retrofitted easily and does not require additional infrastructure," says Dr. -Ing. Volker Großer from the IZM. In contrast to the current monitoring systems it supplies measurement data from a tight-knit sensor network directly attached to the conductor wires.

How much current can be transmitted by a power line depends very much on temperature. If the conductor wires heat up as a result of flowing current or the sun, they expand and sag. If the sagging conductor wire gets too close to the ground, buildings, vehicles or humans, there is a risk of electrocution. To rule this out, prescribed safety clearances are mandatory. At the same time, the permitted current flow is calculated under the assumption that the ambient temperature is 35°C and that the wind's velocity will not exceed 0.6 m/s. However, high midsummer temperatures often bring with them a lull in the wind. Most wind turbine systems will only start to operate once wind velocity has reached 3 m/s. They deliver high amounts of electricity during fall and in winter when the power lines are effectively cooled by the weather.

To better utilize these reserves in the grid without compromising safety, the ASTROSE project partners equip the 110 kV and 380 kV lines with„eGrains." Cylindrical sensor nodes are wrapped around the conductor wire approximately every 500 meters.„They consist of two half cups that are clamped on and attached to each other. The ASTROSE-eGrains measure the cable's angle of inclination, the current flow, the temperature as well as wind movement. All measurement values are relayed from eGrain to eGrain to the next transformer station and there they are fed into the central monitoring and control system or rather made available to the internet-based remote maintenance systems of the grid operators," explains Großer. The ASTROSE eGrains pull the energy they require from the electrical field that surrounds the conductor wires. However, the ASTROSE sensor network does not only help utilize the capacities of the power lines better. It also reports dangerous line sags, such as can occur in winter as a result of ice build-up on the lines. The sensor node can be seen at the„Sensor + Test" tradeshow from June 7 -- 9 in Nuremberg, Germany, in Hall 12, Booth 231.

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Electromechanics Also Operates at the Nanoscale

"We have been studying carbon nanotubes theoretically, in order to see how they behave when they are stimulated to behave according to the laws quantum mechanics. The results provide a completely new platform for scientists to stand on," says Gustav Sonne of the Department of Physics at the University of Gothenburg.

Every day we use a number of different microelectromechanical components for various forms of detection, to determine whether a certain process has taken place or whether a certain substance is present. These cannot be detected without instruments. One example is the detection of rapid accelerations that is used to activate the airbag in a car during an accident. What all of these components have in common is that they combine mechanical and electronic properties in order to react to external stimuli.

Gustav Sonne has taken research down to a whole new dimension -- from the micrometer scale to the nanometer scale -- and he has studied the younger brothers of these components: nanoelectromechanical systems. The studies have been based on tiny nanotubes suspended between two electrical contacts. He has subsequently calculated how small vibrations in the suspended tubes can be coupled to a current that is led through them.

"Our research has focussed mainly on how these systems, which consist of a tiny, super-light mechanical oscillator (the suspended nanotube), can be described in quantum mechanical terms, and what effects this has on the measurements we can carry out. We have been able to demonstrate a number of new mechanisms for electromechanical coupling that should be possible to observe experimentally. This, in turn, may lead to extremely exotic physical phenomena in these structures, phenomena which may be of interest for research into quantum computers, and other fields."

Interest in nanotubes is based on their outstanding properties: they are among the strongest materials known, weigh next to nothing, and have extremely high conductivity for both electric currents and heat. Carbon nanotubes can be used to manufacture composite materials that are several orders of magnitude stronger than currently available materials.

The thesis"Mesoscopic phenomena in the electromechanics of suspended nanowires" was successfully defended in the Department of Physics. Supervisor: Associate professor Leonid Gorelik.

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Battery-Less Chemical Detector Developed

The device overcomes the power requirement of traditional sensors and is simple, highly sensitive and can detect various molecules quickly. Its development could be the first step in making an easily deployable chemical sensor for the battlefield.

The Lab's Yinmin"Morris" Wang and colleagues Daniel Aberg, Paul Erhart, Nipun Misra, Aleksandr Noy and Alex Hamza, along with collaborators from the University of Shanghai for Science and Technology, have fabricated the first-generation battery-less detectors that use one-dimensional semiconductor nanowires.

The nanosensors take advantage of a unique interaction between chemical species and semiconductor nanowire surfaces that stimulate an electrical charge between the two ends of nanowires or between the exposed and unexposed nanowires.

The group tested the battery-less sensors with different types of platforms -- zinc-oxide and silicon -- using ethanol solvent as a testing agent.

In the zinc-oxide sensor the team found there was a change in the electric voltage between the two ends of nanowires when a small amount of ethanol was placed on the detector.

"The rise of the electric signal is almost instantaneous and decays slowly as the ethanol evaporates," Wang said.

However, when the team placed a small amount of a hexane solvent on the device, little electric voltage was seen,"indicating that the nanosensor selectively responds to different types of solvent molecules," Wang said.

The team used more than 15 different types of organic solvents and saw different voltages for each solvent."This trait makes it possible for our nanosensors to detect different types of chemical species and their concentration levels," Wang said.

The response to different solvents was somewhat similar when the team tested the silicon nanosensors. However, the voltage decay as the solvent evaporated was drastically different from the zinc-oxide sensors."The results indicate that it is possible to extend the battery-less sensing platform to randomly aligned semiconductor nanowire systems," Wang said.

The team's next step is to test the sensors with more complex molecules such as those from explosives and biological systems.

The research appears on the inside front cover of the Jan. 4 issue ofAdvanced Materials.

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