Developed at the Microelectronics Systems Laboratory (LSM), Director Yusuf Leblebici is unveiling these results to experts on Wednesday the 25th of January in Paris, in a keynote presentation at the 2012 Interconnection Network Architectures Workshop.

"It's the logical next step in electronics development, because it allows a large increase in terms of efficiency," says Leblebici.

Up to this point, chips could only be assembled horizontally via connections along their edges. Here, they are connected vertically by several hundred very thin copper microtubes. These wires pass through tiny openings, called Through-Silicon-Vias (TSV), made in the core of the silicon layer of each chip.

3D processors
"This superposition reduces the distance between circuits, and thus considerably improves the speed of data exchange," explains LSM researcher Yuksel Temiz, who is doing his PhD thesis on the subject.

To reach this result, the team had to overcome a number of difficulties, such as the fragility of the copper connections and supports which, because they are miniaturized to such an extreme degree (about 50 micrometers in thickness), are as thin as a human hair.

"In three years of work, we made and tested thousands of TSV connections, and had more than 900 functioning simultaneously," says Leblebici.

"Now we have a production process that is really efficient." He adds that the laboratory has also manufactured 3D multi-core processors, connected by a TSV network.

This technology will initially be made available to a number of academic research teams for further development, before being commercialized.

See a related video here. ]]> Thu, 09 FEB 2012 09:06:16 AEST Raleigh, NC (SPX) Jan 25, 2012 - Researchers from North Carolina State University have developed a new method for creating elastic conductors made of carbon nanotubes, which will contribute to large-scale production of the material for use in a new generation of elastic electronic devices.

"We're optimistic that this new approach could lead to large-scale production of stretchable conductors, which would then expedite research and development of elastic electronic devices," says Dr. Yong Zhu, an assistant professor of mechanical and aerospace engineering at NC State, and lead author of a paper describing the new technique.

Stretchable electronic devices would be both more resilient and able to conform to various shapes. Potential applications include devices that can be incorporated into clothing, implantable medical devices, and sensors that can be stretched over unmanned aerial vehicles.

To develop these stretchable electronics, one needs to create conductors that are elastic and will reliably transmit electric signals regardless of whether they are being stretched.

One way of making conductive materials more elastic is to "buckle" them. Zhu's new method buckles carbon nanotubes on the plane of the substrate. Think of the nanotubes as forming squiggly lines on a piece of paper, rather than an accordion shape that zigs up and down with only the bottom parts touching the sheet of paper. Zhu's team used carbon nanotubes because they are sturdy, stable, excellent conductors and can be aligned into ribbons.

The new process begins by placing aligned carbon nanotubes on an elastic substrate using a transfer printing process. The substrate is then stretched, which separates the nanotubes while maintaining their parallel alignment.

Strikingly, when the substrate is relaxed, the nanotubes do not return to their original positions. Instead, the nanotubes buckle - creating what looks like a collection of parallel squiggly lines on a flat surface.

The carbon nanotubes are now elastic - they can be stretched - but they have retained their electrical properties.

The key benefit of this new method is that it will make manufacturing of elastic conductors significantly more efficient, because the carbon nanotubes can be applied before the substrate is stretched. This is compatible with existing manufacturing processes. "For example, roll-to-roll printing techniques could be adapted to take advantage of our new method," Zhu says.

A paper describing the new approach, "Buckling of Aligned Carbon Nanotubes as Stretchable Conductors: A New Manufacturing Strategy," was published online Jan. 23 in Advanced Materials. The paper was co-authored by Feng Xu, a Ph.D. student at NC State. The research was funded by the National Science Foundation.

In another new paper, Zhu's team has demonstrated for the first time that carbon nanotubes can be buckled using a technique in which the elastic substrate is stretched before the nanotubes are applied. The substrate is then relaxed, forcing the nanotubes to buckle out of plane. The nanotubes form a ribbon that curves up and down like the bellows of an accordion. This second technique has been used before with other materials. This second paper, "Wavy Ribbons of Carbon Nanotubes for Stretchable Conductors," was published Jan. 19 in Advanced Functional Materials.

]]> Thu, 09 FEB 2012 09:06:16 AEST Sydney, Australia (SPX) Jan 24, 2012 - Physicists at the University of New South Wales have observed a new kind of interaction that can arise between electrons in a single-atom silicon transistor.

The findings, to be published this week in the journal Physical Review Letters, offer a more complete understanding of the mechanisms for electron transport in nanostructures at the atomic level.

"We have been able to study some of the most complicated transport mechanisms that can arise up to the single atom level," says lead author Dr Giuseppe C. Tettamanzi, from the School of Physics at UNSW.

The results contained in this study open the door for new quantum electronic schemes inwhich it is the orbital nature of the electrons - and not their spin or their charge - that plays a major role, he says.

The study, in collaboration with scientists from the ICMM in Madrid and the Kavli Institute in The Netherlands, describes how a single electron bound to a dopant atom in a silicon matrix can interact with many electrons throughout the transistor.

In these geometries, electron-electron interactions can be dominated by something called the Kondo effect. Conventionally, this arises from the spin degree of freedom, which represents an angular momentum intrinsic to each electron and is always in the up or in the down state.

However, researchers also observed that similar interactions could arise through the orbital degree of freedom of the electron. This describes the wave-like function of an electron and can be used to help determine an electrons' probable location around the atom's nucleus.

Importantly, by applying a strong magnetic field, the researchers were able to tune thiseffect to eliminate the spin-spin interactions while preserving the orbital-orbital interactions.

"By tuning the effect in two different symmetries of the fundamental state of the system...we have observed a symmetry crossover identical to those seen in high-energy physics," says Tettamanzi.

"In our case this crossover was observed simply by using a semiconductor device which is not too different from the transistor you use daily to send your emails."

Tettamanzi, who was recently awarded a prestigious ARC Discovery Early Career Researcher Award fellowship, will now investigate another transport mechanism that can arise in quantum dots and single atom transistors called "quantised charge pumping".

The idea here is to create a current flowing through a nanostructure without applying a voltage between the leads, but by applying varying potentials at one or more gates of the transistor, in an apparent violation of Ohm's law.

]]> Thu, 09 FEB 2012 09:06:16 AEST Copenhagen, Denmark (SPX) Jan 24, 2012 - Researchers at the Niels Bohr Institute have combined two worlds - quantum physics and nano physics, and this has led to the discovery of a new method for laser cooling semiconductor membranes.

Semiconductors are vital components in solar cells, LEDs and many other electronics, and the efficient cooling of components is important for future quantum computers and ultrasensitive sensors. The new cooling method works quite paradoxically by heating the material!

Using lasers, researchers cooled membrane fluctuations to minus 269 degrees C. The results are published in the scientific journal, Nature Physics.

"In experiments, we have succeeded in achieving a new and efficient cooling of a solid material by using lasers. We have produced a semiconductor membrane with a thickness of 160 nanometers and an unprecedented surface area of 1 by 1 millimeter.

"In the experiments, we let the membrane interact with the laser light in such a way that its mechanical movements affected the light that hit it.

"We carefully examined the physics and discovered that a certain oscillation mode of the membrane cooled from room temperature down to minus 269 degrees C, which was a result of the complex and fascinating interplay between the movement of the membrane, the properties of the semiconductor and the optical resonances," explains Koji Usami, associate professor at Quantop at the Niels Bohr Institute.

From gas to solid
Laser cooling of atoms has been practiced for several years in experiments in the quantum optical laboratories of the Quantop research group at the Niels Bohr Institute. Here researchers have cooled gas clouds of cesium atoms down to near absolute zero, minus 273 degrees C, using focused lasers and have created entanglement between two atomic systems.

The atomic spin becomes entangled and the two gas clouds have a kind of link, which is due to quantum mechanics. Using quantum optical techniques, they have measured the quantum fluctuations of the atomic spin.

"For some time we have wanted to examine how far you can extend the limits of quantum mechanics - does it also apply to macroscopic materials?

It would mean entirely new possibilities for what is called optomechanics, which is the interaction between optical radiation, i.e. light, and a mechanical motion," explains Professor Eugene Polzik, head of the Center of Excellence Quantop at the Niels Bohr Institute at the University of Copenhagen.

But they had to find the right material to work with.

Lucky coincidence
In 2009, Peter Lodahl (who is today a professor and head of the Quantum Photonic research group at the Niels Bohr Institute) gave a lecture at the Niels Bohr Institute, where he showed a special photonic crystal membrane that was made of the semiconducting material gallium arsenide (GaAs). Eugene Polzik immediately thought that this nanomembrane had many advantageous electronic and optical properties and he suggested to Peter Lodahl's group that they use this kind of membrane for experiments with optomechanics. But this required quite specific dimensions and after a year of trying they managed to make a suitable one.

"We managed to produce a nanomembrane that is only 160 nanometers thick and with an area of more than 1 square millimetre. The size is enormous, which no one thought it was possible to produce," explains Assistant Professor Soren Stobbe, who also works at the Niels Bohr Institute. Basis for new research

Now a foundation had been created for being able to reconcile quantum mechanics with macroscopic materials to explore the optomechanical effects.

Koji Usami explains that in the experiment they shine the laser light onto the nanomembrane in a vacuum chamber. When the laser light hits the semiconductor membrane, some of the light is reflected and the light is reflected back again via a mirror in the experiment so that the light flies back and forth in this space and forms an optical resonator. Some of the light is absorbed by the membrane and releases free electrons.

The electrons decay and thereby heat the membrane and this gives a thermal expansion. In this way the distance between the membrane and the mirror is constantly changed in the form of a fluctuation.

"Changing the distance between the membrane and the mirror leads to a complex and fascinating interplay between the movement of the membrane, the properties of the semiconductor and the optical resonances and you can control the system so as to cool the temperature of the membrane fluctuations.

This is a new optomechanical mechanism, which is central to the new discovery. The paradox is that even though the membrane as a whole is getting a little bit warmer, the membrane is cooled at a certain oscillation and the cooling can be controlled with laser light. So it is cooling by warming! We managed to cool the membrane fluctuations to minus 269 degrees C", Koji Usami explains.

"The potential of optomechanics could, for example, pave the way for cooling components in quantum computers. Efficient cooling of mechanical fluctuations of semiconducting nanomembranes by means of light could also lead to the development of new sensors for electric current and mechanical forces. Such cooling in some cases could replace expensive cryogenic cooling, which is used today and could result in extremely sensitive sensors that are only limited by quantum fluctuations," says Professor Eugene Polzik.

]]> Thu, 09 FEB 2012 09:06:16 AEST Austin TX (SPX) Jan 23, 2012 - The first systematic power profiles of microprocessors could help lower the energy consumption of both small cell phones and giant data centers, report computer science professors from The University of Texas at Austin and the Australian National University.

Their results may point the way to how companies like Google, Apple, Intel and Microsoft can make software and hardware that will lower the energy costs of very small and very large devices.

"The less power cell phones draw, the longer the battery will last," says Kathryn McKinley, professor of computer science at The University of Texas at Austin.

"For companies like Google and Microsoft, which run these enormous data centers, there is a big incentive to find ways to be more power efficient. More and more of the money they're spending isn't going toward buying the hardware, but toward the power the datacenters draw."

McKinley says that without detailed power profiles of how microprocessors function with different software and different chip architectures, companies are limited in terms of how well they can optimize for energy usage.

The study she conducted with Stephen M. Blackburn of The Australian National University and their graduate students is the first to systematically measure and analyze application power, performance, and energy on a wide variety of hardware.

This work was recently invited to appear as a Research Highlight in the Communications of the Association for Computer Machinery (CACM). It's also been selected as one of this year's "most significant research papers in computer architecture based on novelty and long-term impact" by the journal IEEE Micro.

"We did some measurements that no one else had done before," says McKinley. "We showed that different software, and different classes of software, have really different power usage."

McKinley says that such an analysis has become necessary as both the culture and the technologies of computing have shifted over the past decade.

Energy efficiency has become a greater priority for consumers, manufacturers and governments because the shrinking of processor technology has stopped yielding exponential gains in power and performance.

The result of these shifts is that hardware and software designers have to take into account tradeoffs between performance and power in a way they did not ten years ago.

"Say you want to get an application on your phone that's GPS-based," says McKinley, "In terms of energy, the GPS is one of the most expensive functions on your phone. A bad algorithm might ping your GPS far more than is necessary for the application to function well.

"If the application writer could analyze the power profile, they would be motivated to write an algorithm that pings it half as often to save energy without compromising functionality."

McKinley believes that the future of software and hardware design is one in which power profiles become a consideration at every stage of the process.

Intel, for instance, has just released a chip with an exposed power meter, so that software developers can access some information about the power profiles of their products when run on that chip. McKinley expects that future generations of chips will expose even more fine-grained information about power usage.

Software developers like Microsoft (where McKinley is spending the next year, while taking a leave from the university) are already using what information they have to inform their designs. And device manufacturers are testing out different architectures for their phones or tablets that optimize for power usage.

McKinley says that even consumers may get information about how much power a given app on their smart phone is going to draw before deciding whether to install it or not.

"In the past, we optimized only for performance," she says. "If you were picking between two software algorithms, or chips, or devices, you picked the faster one. You didn't worry about how much power it was drawing from the wall socket.

There are still many situations today-for example, if you are making software for stock market traders-where speed is going to be the only consideration. But there are a lot of other areas where you really want to consider the power usage."

]]> Thu, 09 FEB 2012 09:06:16 AEST Boston MA (SPX) Jan 20, 2012 - The Fourier transform is one of the most fundamental concepts in the information sciences. It's a method for representing an irregular signal - such as the voltage fluctuations in the wire that connects an MP3 player to a loudspeaker - as a combination of pure frequencies. It's universal in signal processing, but it can also be used to compress image and audio files, solve differential equations and price stock options, among other things.

The reason the Fourier transform is so prevalent is an algorithm called the fast Fourier transform (FFT), devised in the mid-1960s, which made it practical to calculate Fourier transforms on the fly. Ever since the FFT was proposed, however, people have wondered whether an even faster algorithm could be found.

At the Association for Computing Machinery's Symposium on Discrete Algorithms (SODA) this week, a group of MIT researchers will present a new algorithm that, in a large range of practically important cases, improves on the fast Fourier transform.

Under some circumstances, the improvement can be dramatic - a tenfold increase in speed. The new algorithm could be particularly useful for image compression, enabling, say, smartphones to wirelessly transmit large video files without draining their batteries or consuming their monthly bandwidth allotments.

Like the FFT, the new algorithm works on digital signals. A digital signal is just a series of numbers - discrete samples of an analog signal, such as the sound of a musical instrument. The FFT takes a digital signal containing a certain number of samples and expresses it as the weighted sum of an equivalent number of frequencies.

"Weighted" means that some of those frequencies count more toward the total than others. Indeed, many of the frequencies may have such low weights that they can be safely disregarded. That's why the Fourier transform is useful for compression.

An eight-by-eight block of pixels can be thought of as a 64-sample signal, and thus as the sum of 64 different frequencies. But as the researchers point out in their new paper, empirical studies show that on average, 57 of those frequencies can be discarded with minimal loss of image quality.

Heavyweight division
Signals whose Fourier transforms include a relatively small number of heavily weighted frequencies are called "sparse." The new algorithm determines the weights of a signal's most heavily weighted frequencies; the sparser the signal, the greater the speedup the algorithm provides. Indeed, if the signal is sparse enough, the algorithm can simply sample it randomly rather than reading it in its entirety.

"In nature, most of the normal signals are sparse," says Dina Katabi, one of the developers of the new algorithm.

Consider, for instance, a recording of a piece of chamber music: The composite signal consists of only a few instruments each playing only one note at a time. A recording, on the other hand, of all possible instruments each playing all possible notes at once wouldn't be sparse - but neither would it be a signal that anyone cares about.

The new algorithm - which associate professor Katabi and professor Piotr Indyk, both of MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL), developed together with their students Eric Price and Haitham Hassanieh - relies on two key ideas.

The first is to divide a signal into narrower slices of bandwidth, sized so that a slice will generally contain only one frequency with a heavy weight.

In signal processing, the basic tool for isolating particular frequencies is a filter. But filters tend to have blurry boundaries: One range of frequencies will pass through the filter more or less intact; frequencies just outside that range will be somewhat attenuated; frequencies outside that range will be attenuated still more; and so on, until you reach the frequencies that are filtered out almost perfectly.

If it so happens that the one frequency with a heavy weight is at the edge of the filter, however, it could end up so attenuated that it can't be identified. So the researchers' first contribution was to find a computationally efficient way to combine filters so that they overlap, ensuring that no frequencies inside the target range will be unduly attenuated, but that the boundaries between slices of spectrum are still fairly sharp.

Zeroing in
Once they've isolated a slice of spectrum, however, the researchers still have to identify the most heavily weighted frequency in that slice.

In the SODA paper, they do this by repeatedly cutting the slice of spectrum into smaller pieces and keeping only those in which most of the signal power is concentrated. But in an as-yet-unpublished paper, they describe a much more efficient technique, which borrows a signal-processing strategy from 4G cellular networks.

Frequencies are generally represented as up-and-down squiggles, but they can also be though of as oscillations; by sampling the same slice of bandwidth at different times, the researchers can determine where the dominant frequency is in its oscillatory cycle.

Two University of Michigan researchers - Anna Gilbert, a professor of mathematics, and Martin Strauss, an associate professor of mathematics and of electrical engineering and computer science - had previously proposed an algorithm that improved on the FFT for very sparse signals.

"Some of the previous work, including my own with Anna Gilbert and so on, would improve upon the fast Fourier transform algorithm, but only if the sparsity k" - the number of heavily weighted frequencies - "was considerably smaller than the input size n," Strauss says.

The MIT researchers' algorithm, however, "greatly expands the number of circumstances where one can beat the traditional FFT," Strauss says. "Even if that number k is starting to get close to n - to all of them being important - this algorithm still gives some improvement over FFT."

]]> Thu, 09 FEB 2012 09:06:16 AEST Princeton NJ (SPX) Jan 18, 2012 - An international team of researchers including scientists at Princeton University have achieved a 100-fold increase in the ability to maintain control the spins of electrons in a solid material, a key step in the development of ultrafast quantum computers.

Until recently, the best attempts at such control lasted for only a fraction of a second. But researchers Stephen Lyon and Alexei Tyryshkin have found a way to extend the control over the spins of billions of electrons in a silicon chip for up to 10 seconds, far longer than any previous attempt.

Lyon, an electrical engineering professor, said the key to the new results lies in a highly purified sample of silicon. The experiment uses a small silicon chip the size of a pencil lead made almost entirely of a particular isotope of silicon: silicon-28. The researchers, part of an international team, reported their results online Dec. 4 in Nature Materials.

"Partly, it is an improvement in our measurements, but it is mainly the material," Lyon said. "This is the purest sample we have ever used."

In an experiment conducted in the basement of Princeton's Hoyt laboratory, the researchers suspended the sample of pure silicon inside a cylinder filled with liquid helium, dropping its temperature to 2 kelvin, or just above absolute zero.

They locked the cylinder between two donut-shaped rings about the size of pizza boxes that control the magnetic field around the sample. A click of a computer mouse sent microwaves pulsing across the silicon, and coordinated the spins of about 100 billion electrons.

"The first pulse twists them, the second reverses them, and at some point the sample itself produces a microwave pulse, and we call that the echo," Lyon said. "By doing the second pulse, getting everything to reverse, we get the electrons into phase."

In describing electrons, scientists use the term spin. But like a lot of things in quantum mechanics, the meaning is a little bit tricky. For subatomic particles like electrons, spin is a fundamental characteristic that can make them behave like incredibly tiny magnets. Lyon's team uses this magnetic signature in their observations.

Maintaining that phase is what scientists call "coherence." Unlike objects in the everyday world, subatomic particles, which operate under the rules of quantum mechanics, can be in more than one place at the same time. Electrons' spin, for example, can be classified as up, down, or in superposition, a state that is both up and down simultaneously. It is this superposition state that allows for the highly complex mathematics at the heart of quantum computing.

A standard computer uses transistors either switched off or on to represent the 0's and 1's that are the bits that make up the basis of all computer programs. But instead of this binary language, a quantum computer would incorporate the uncertainty of quantum mechanics into its programming. Instead of bits, the computers will use quantum bits or qubits - a value that is inherently indeterminate.

Mathematicians are still working on ways to take advantage of such a machine. They believe it could be used to factor incredibly large numbers, break cryptographic codes or to simulate the behavior of molecules.

Although mathematically fascinating, keeping electrons in this indeterminate state is fantastically difficult for engineers. In a 2003 report in Physical Review B, Lyon's group reported a breakthrough when they maintained coherence for 60 milliseconds (a millisecond is one thousandth of a second.)

To understand why it is so hard, imagine circus performers spinning plates on the top of sticks. Now imagine a strong wind blasting across the performance space, upending the plates and sending them crashing to the ground. In the subatomic realm, that wind is magnetism, and much of the effort in the experiment goes to minimizing its effect. By using a magnetically calm material like silicon 28, the researchers are able to keep the electrons spinning together for much longer.

"The project started ten years ago," said Tyryshkin, a research scientist in the electrical engineering department. "Steve came into my office saying let's try a sample that is clean of other isotopes."

Lyon said the experiment is a successor to one performed in 1958 at Bell Labs by James Gordon, one of the co-inventors of the maser (the predecessor to the laser). Using technology available at the time, Gordon was able to maintain coherence for 600 microseconds (a microsecond is one millionth of second.) Lyon and Tyryshkin began following a similar path after they ran early tests in their lab and began seeing similar numbers to those reported by Gordon.

The researchers tried a series of different samples, each of increasingly purified silicon. The answer finally came through the Avogadro Project, an international effort to create a pure kilogram of silicon.

Michael Thewalt, a physics professor at Simon Fraser University and Kohei Itoh, a professor at Keio University, co-authors of the recent paper with Lyon, had been working with the Avogadro Project and requested a special sample for use in the electron spinning experiment.

Elements are identified by the number of protons inside their nucleus: carbon has 6 protons, silicon has 14. But most elements come in different version - called isotopes - determined by the number of neutrons. Some isotopes, like silicon-28, have no magnetism, while others create a strong magnetic effect at atomic level. A relatively common isotope of silicon, silicon-29, has a very strong magnetic presence and, therefore it was a prime target for elimination.

The combined effort largely eliminated isotopes of silicon that create a strong magnetic field - like silicon-29 - and other impurities. The scientists managed to clean the sample to an amazing degree: silicon-29, which usually makes up nearly 50,000 parts per million of a typical sample, was reduced to 50 parts per million in the chip sent to the Princeton team.

In fact, the final silicon crystal was so pure that the scientists in Berlin added a trace amount of phosphorous so the sample would be electrically active enough to respond to the microwave pulse in the laboratory.

That response, which researchers call "the echo" is how the researchers read the electrons' spin state. So calibrating the correct amount of phosphorous was critical - too much would create the magnetic noise that the team was trying to eliminate, but too little would leave the echo too faint to detect.

"A lot of the work boils down to getting the phosphorous far enough apart," Lyon said. Temperature is also critical. At room temperature, the electrons from the phosphorous are too active, and prevent the control that the team is trying to exert. But once the researchers use liquid helium to drop the sample's temperature to 2 Kelvin (-455.8 degrees Fahrenheit,) everything calms down.

"It has taken quite a bit of work to get to this point," Lyon said. "Nine years of refining measurements and materials."

Besides Tyryshkin, Lyon, Thewalt and Itoh, the team that contributed to the work described in the Nature Materials article included Shinichi Tojo and of Keio University; John Morton of Oxford University; Helge Riemann and Nikolai Abrosimov of the Institut fur Kristallzuchtung; Peter Becker of Physikalisch-Technische Bundesanstalt; Hans-Joachim Pohl, of VITCON Projectconsult GMBH; and Thomas Schenkel of Lawrence Berkeley National Laboratory.

Extending coherence time is an important step toward building a working quantum computer. The key is to maintain coherence long enough for programs to correct and maintain data before the spins lose their coherence. It is hard to set a threshold for the length of coherence needed for a practical computer, because it depends on the type of program and size of the computer.

"The bottom line is, you want it as long as possible," Tyryshkin said.

Other researchers have managed to attain extended coherence using ions in a vacuum instead of a solid material like silicon. But Lyon's team chose to work with silicon because they believe it is more practical to attempt to scale up the material for use in a computer than to try to do so with vacuum tubes.

"It would be far easier to build devices out of silicon, but we still have to do many other things before we can get to that point," he said.

The researchers stressed that their results were one step on a long road toward a working computer. The electrons on their sample represent one quantum bit, or qubit, and many such qubits would be needed for a working computer. How many is difficult to say.

"Right now, we are using one," Tyryshkin said "If we could come up with a thousand, that would be a very interesting machine."

]]> Thu, 09 FEB 2012 09:06:16 AEST West Lafayette, IN (SPX) Jan 18, 2012 - Researchers have created new "microtweezers" capable of manipulating objects to build tiny structures, print coatings to make advanced sensors, and grab and position live stem cell spheres for research.

The microtweezers might be used to assemble structures in microelectromechanical systems, or MEMS, which contain tiny moving parts. MEMS accelerometers and gyroscopes currently are being used in commercial products.

A wider variety of MEMS devices, however, could be produced through a manufacturing technology that assembles components like microscopic Lego pieces moved individually into place with microtweezers, said Cagri Savran (pronounced Chary Savran), an associate professor of mechanical engineering at Purdue University.

"We've shown how this might be accomplished easily, using new compact and user-friendly microtweezers to assemble polystyrene spheres into three-dimensional shapes," he said.

Research findings were detailed in a paper that appeared online in December in the Journal of Microelectromechanical Systems, or JMEMS. The paper was written by Savran, mechanical engineering graduate students Bin-Da Chan and Farrukh Mateen, electrical and computer engineering graduate student Chun-Li Chang, and biomedical engineering doctoral student Kutay Icoz.

The new tool contains three main parts: a thimble knob from a standard micrometer, a two-pronged tweezer made from silicon, and a "graphite interface," which converts the turning motion of the thimble knob into a pulling-and-pushing action to open and close the tweezer prongs.

No electrical power sources are needed, increasing the potential for practical applications. Other types of microtweezers have been developed and are being used in research. However, the new design is simpler both to manufacture and operate, Savran said.

The design contains a one-piece "compliant structure," which is springy like a bobby pin or a paperclip. Most other microtweezers require features such as hinges or components that move through heat, magnetism or electricity, complex designs that are expensive to manufacture and relatively difficult to operate in various media, he said.

The tweezers make it feasible to precisely isolate individual stem cell spheres from culture media and to position them elsewhere. Currently, these spheres are analyzed in large groups, but microtweezers could provide an easy way to study them by individually selecting and placing them onto analytical devices and sensors.

"We currently are working to weigh single micro particles, individually selected among many others, which is important because precise measurements of an object's mass reveal key traits, making it possible to identify composition and other characteristics," Savran said. "This will now be as easy as selecting and weighing a single melon out of many melons in a supermarket."

That work is a collaboration with the research group of Timothy Ratliff, the Robert Wallace Miller Director of Purdue's Center for Cancer Research.

The microtweezers also could facilitate the precision printing of chemical or protein dots onto "microcantilevers," strips of silicon that resemble tiny diving boards. The microcantilevers can be "functionalized," or coated with certain chemicals or proteins that attract specific molecules and materials. Because they vibrate at different frequencies depending on what sticks to the surface, they are used to detect chemicals in the air and water.

Generally, microcantilevers are functionalized to detect one type of substance by exposing them to fluids, Savran said.

However, being able to microprint a sequence of precisely placed dots of different chemicals on each cantilever could make it possible to functionalize a device to detect several substances at once. Such a sensing technology also would require a smaller sample size than conventional diagnostic technologies, making it especially practical.

The new microtweezers are designed to be attached easily to "translation stages" currently used in research.

These stages are essentially platforms on which to mount specimens for viewing and manipulating. Unlike most other microtweezers, the new device is highly compact and portable and can be easily detached from a platform and brought to another lab while still holding a micro-size object for study, Savran said.

The two-pronged tweezer is micromachined in a laboratory called a "clean room" with the same techniques used to create microcircuits and computer chips. The research was based at the Birck Nanotechnology Center in Purdue's Discovery Park.

Purdue has filed for a provisional patent on the design.

]]> Thu, 09 FEB 2012 09:06:16 AEST Duisburg, Germany (SPX) Jan 17, 2012 - Conventional CMOS image sensors are not suitable for low-light applications such as fluorescence, since large pixels arranged in a matrix do not support high readout speeds. A new optoelectronic component speeds up this process. It has already been patented.

CMOS image sensors have long since been the solution of choice for digital photography. They are much cheaper to produce than existing sensors, and they are also superior in terms of power consumption and handling.

Consequently, leading manufacturers of cell-phone and digital cameras fit CMOS chips in their products almost without exception. This not only reduces the demands made of the battery, it also makes increasingly smaller cameras possible.

Yet these optical semiconductor chips are now reaching their limits: while miniaturization in consumer electronics is leading to increasingly smaller pixels around 1 micrometer across, certain applications require larger pixels in excess of 10 micrometers.

Particularly in areas where only minimal light is available, such as in X-ray photography or in astronomy, having a larger pixel area compensates for the lack of light. Pinned photodiodes (PPD) are used to convert the light signals into electrical pulses.

These optoelectric components are crucial for image processing and are built into the CMOS chips. "Yet when the pixels exceed a certain size, the PPDs have a speed problem", explains Werner Brockherde, head of department at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS. Low-light applications tend to call for high image rates. "But the readout speed using PPD is too low", says Brockherde.

The Fraunhofer researchers have now come up with a solution to this problem - it is unique and has already been patented. The scientists have developed a new optoelectronic component, the lateral drift field photodetector (LDPD).

"In this component, the charge carriers generated by the incident light move at high speed to the readout node," explains the researcher. With the PPD the electrons simply diffuse to the exit; a comparatively slow process but which is sufficient for many applications. "But by integrating an internal electric field into the photoactive region of the component, we have managed to accelerate this process by a factor of up to a hundred."

To produce the new component, the Fraunhofer researchers improved upon the currently available CMOS chip manufacturing process based on the 0.35 m standard: "The additional LDPD component must not be allowed to impair the properties of the other components," says Brockherde.

Using simulation calculations the experts managed to meet these requirements - and a prototype of the new high-speed CMOS image sensors is already available. "We expect to get approval for series production next year," says Brockherde.

The high-speed CMOS sensors are ideal candidates for applications that require large pixels and a high readout speed: astronomy, spectroscopy or state-of-the-art X-ray photography are among the potential applications.

But the sensors are also ideally suited for use as 3-D sensors based on the time-of-flight process, whereby light sources emit short pulses that are reflected by the objects. The time-of-flight of the reflected light is then recorded by a sensor and used to create a fully-fledged 3-D image.

This technology is a compelling proposition for applications such as crash protection, as the sensors can precisely record their environment in three dimensions. The Fraunhofer researchers have already developed this kind of area sensor based on the unique pixel configuration for TriDiCam GmbH.

Research News January 2012 [ PDF 0.43MB ]

]]> Thu, 09 FEB 2012 09:06:16 AEST Champaign, IL (SPX) Jan 17, 2012 - University of Illinois materials scientists have developed a new reactive silver ink for printing high-performance electronics on ubiquitous, low-cost materials such as flexible plastic, paper or fabric substrates.

Jennifer Lewis, the Hans Thurnauer Professor of Materials Science and Engineering, and graduate student S. Brett Walker described the new ink in the Journal of the American Chemical Society.

"We are really excited about the wide applicability and excellent electrical properties of this new silver ink," said Lewis, the director of the Frederick Seitz Materials Research Laboratory at the U. of I.

Electronics printed on low-cost, flexible materials hold promise for antennas, batteries, sensors, solar energy, wearable devices and more. Most conductive inks rely on tiny metal particles suspended in the ink. The new ink is a transparent solution of silver acetate and ammonia. The silver remains dissolved in the solution until it is printed, and the liquid evaporates, yielding conductive features.

"It dries and reacts quickly, which allows us to immediately deposit silver as we print," Walker said.

The reactive ink has several advantages over particle-based inks. It is much faster to make: A batch takes minutes to mix, according to Walker, whereas particle-based inks take several hours and multiple steps to prepare. The ink also is stable for several weeks.

The reactive silver ink also can print through 100-nanometer nozzles, an order of magnitude smaller than particle-based inks, an important feature for printed microelectronics. Moreover, the ink's low viscosity makes it suitable for inkjet printing, direct ink writing or airbrush spraying over large, conformal areas.

"For printed electronics applications, you need to be able to store the ink for several months because silver is expensive," Walker said. "Since silver particles don't actually form until the ink exits the nozzle and the ammonia evaporates, our ink remains stable for very long periods. For fine-scale nozzle printing, that's a rarity."

The reactive silver ink boasts yet one more key advantage: a low processing temperature. Metallic inks typically need to be heated to achieve bulk conductivity through a process called annealing. The annealing temperatures for many particle-based inks are too high for many inexpensive plastics or paper. By contrast, the reactive silver ink exhibits an electrical conductivity approaching that of pure silver upon annealing at 90 degrees Celsius.

"We are now focused on patterning large-area transparent conductive surfaces using this reactive ink," said Lewis, who also is affiliated with the Beckman Institute for Advanced Science and Technology, the Micro and Nanotechnology Lab and the department of chemical and biomolecular engineering at the U. of I.

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