Monday, August 28, 2006

"OPTICAL: Displays may see full color"

Swiss researchers have found a way to directly make any color that can be perceived by the human eye on a computer screen. Instead of mixing red, green and blue, as is done today, electrical engineers at the Swiss Federal Institute of Technology (Zurich) have crafted an electrically controlled, flexible diffraction grating that can be tuned in real-time to any possible color. Though they have so far made only a single pixel, the EEs say that displays based on their technology could one day emit a unique color at each pixel by sending the appropriate electrical voltage to its deformable diffraction grating. Creating a spectrum of colors on a computer display is now accomplished by mixing RGB subpixels. But mixing three primary colors can represent only a fraction of the color space that the human eye can perceive. Now, the Swiss team believes it has found a way around the problem. Its electrically deformable diffraction grating is fabricated by sandwiching an electroactive-polymer dielectric--also called an artificial muscle--between two flexible conductors. The diffraction grating separates white light into a spectrum of colors in the same way that prisms do. When a voltage is applied, the conductors are attracted to each other, thereby squeezing the sandwiched polymer, which causes it to spread out.

"SECURITY: CT scanner to screen carry-on luggage in '07"

Since the British police foiled the plot to smuggle liquid explosives onto U.S.-bound commercial aircraft in carry-on baggage, the Transportation Security Administration (TSA) has been scrambling to develop technologies that could spot such items. Luckily, the best bet for identifying liquid explosives, according to its developer, is already in beta testing at Boston's Logan International Airport. Dubbed Cobra by developer Analogic Corp. (Peabody, Mass.), the scanner can detect objects of any shape that are massive enough to be a threat — including liquid explosives. If it passes certification by the TSA, Cobra could be deployed in airports nationwide by mid-2007. Both Cobra and a larger version called Exact, which has already been installed in more than half of the major airports in the United States, draw on Analogic's expertise in making medical scanners. By the late 1990s, Analogic was already adapting what was then called the "CAT" scanner--today called computed tomography (CT)--for use by airport security. After Sept. 11, the TSA mandated that all checked baggage be scanned, and Analogic's Exact was available to meet the need. The company quickly sold 525 Exact scanners, for sales of $525 million. The system, standing more than 7 feet tall and weighing 6,700 pounds, screens checked baggage automatically in an airport's private back room, diverting any suspicious bags to a side conveyer, where they are hand-checked with trace detectors. Cobra scales down Exact to a size and cost that makes it economical for use in screening carry-on bags.

Monday, August 21, 2006

"SECURITY: PC tool teams with X-rays to find explosives"

The revelation of a terrorist plot to smuggle liquid-explosive precursors onto airliners headed for the United States, then mix them together in the plane's bathroom, has sent the U.S. Transportation Security Administration and other anti-terrorism task forces worldwide scouring for systems that can detect liquid threats. The problem is that traditional, "sniffer" type sensors depend on detecting traces of explosives left on the outsides of the containers in which they are packed. Carefully sealed liquid containers, possibly fitting an unusual form factor or even shielded by metal, might get by a sniffer. And conventional X-ray detectors, which depend on human screeners to read the X-rays and identify weapons via shape recognition, cannot screen for liquids. Now Guardian Technologies International Inc. (Herndon, Va.) says it has devised PC-based software that can be used in tandem with conventional X-ray detectors in the field, acting as "a second set of eyes" to identify liquid-based compounds for explosives in scanned baggage.

"ENERGY: ORNL spin-off beta tests hybrid solar lighting"

The Department of Energy's Oak Ridge National Laboratory has transferred its hybrid solar/artificial-light technology to Sunlight Direct LLC (Oak Ridge, Tenn.), a company spun off from ORNL to commercialize the approach. Now in beta testing at five locations, with 20 more slated to be installed this fall, the technology could save utility customers $1 per square foot yearly on lighting costs, its inventors say. The adaptive, full-spectrum, solar collection and distribution platform, developed over a 10-year period with millions in Energy Department grants, collects sunlight via a mirrored dish on the roof that tracks the sun as it passes overhead each day. The mirror concentrates the resultant beam onto more than 120 fiber-optic cables, each measuring 3 mm in diameter, and distributes the fibers to 12 light fixtures covering 1,000 square feet in the building. The fixtures house two diffusion tubes (for dispersing the light from the fibers) alongside a high-temperature fluorescent tube. An electronic tracker adjusts the fluorescent tube's output so that the illumination level in the building does not vary with the strength of the sunlight. The system costs about $12 per square foot to install, but Sunlight Direct aims to reduce that to about $4. At the lower installed cost, the system would take only a few years to pay for itself. Besides the savings to the utility customer, hybrid solar lighting should ease overtaxed power grids during peak demand periods.

Thursday, August 17, 2006

"CHIPS: Atomic switch could yield higher-density memories"

A single-atom oscillator demonstrated by the Center for Nanoscale Science and Technology could become the basis for a future bistable atomic switch. Scientists at the Center, part of the Commerce Department's National Institute of Standards and Technology (NIST), injected a charge that switched a single cobalt atom between two locations on a crystalline substrate. The next step will be building a working device in a circuit. That will require a semiconducting or insulating substrate. Though they are years away, arrays of atomic-scale devices could provide the enhanced density needed for future memory devices.

Wednesday, August 16, 2006

"CHIPS: Diamond MEMS integrated with CMOS"

The world's first microelectromechanical systems (MEMS) directly integrated onto a CMOS chip is the aim of a new joint effort among U.S. laboratories, industry and academia.
Advanced Diamond Technologies Inc. (ADT), a spinoff from the U.S. Energy Department's Argonne National Laboratory, partnered last week with MEMS pioneer Innovative Micro Technology (Santa Barbara, Calif.) and the University of Wisconsin at Madison. They will supply the Defense Advanced Research Projects Agency (Darpa) with RF MEMS oscillators and resonators by next year. MEMS devices will be integrated with CMOS chips using the ultrananocrystalline diamond thin films patented by Argonne National Laboratory and licensed to ADT. Low-temperature processing required for diamond films enables MEMS circuit components to be fabricated in predesignated areas on finished CMOS chips.

Monday, August 14, 2006

"CHIPS: Nanotubes form vias in novel chip process"

Vias on printed-circuit boards are metal-clad holes that connect component leads on the top to component leads on the bottom. Similarly, on chips, semiconductor circuitry on one layer can be connected to a second layer via a hole, etched in the interlayer dielectric, which is then filled with metal. Now Purdue University engineers have demonstrated a semiconductor fabrication technique that uses tiny, 30- to 50-nanometer-pitch arrays of vertically grown carbon nanotubes for vias be- tween layers on semiconductor chips. The technique, devised by Timothy Fisher and Timothy Sands at Purdue's Birck Nanotechnology Center, works by virtue of "porous anodic alumina," which can form a network of evenly spaced pores in an aluminum oxide dielectric layer and then grow carbon nanotubes through the pores to form vias between layers. The technique produces both single- and double-walled carbon nanotubes. Each pore grows only a single tube, suggesting that the vias can be strictly controlled. That would make them easier to integrate with normal CMOS circuitry.

"MATERIALS: Metamaterials hold key to cloak of invisibility"

A "cloak of invisibility" sounds like the stuff of comic book superheroes. In fact, invisibility cloaks for any type of electromagnetic radiation--even visible light--are something Duke University postdoctoral fellow David Schurig believes are within grasp. Schurig and the professors directing his research--David Smith at Duke and Sir John Pendry at the Imperial College in London--maintain that by the end of 2007, metamaterials will enable an invisibility cloak that works in the microwave range. Further engineering effort will create such cloaks for other types of light, the researchers say. Metamaterials, or engineered composites, substitute macroscopic objects for atoms in a giant crystalline-like lattice, enabling the pitch of passive-component arrays to set the wavelengths affected. The design of these component arrays harks back to the first principles of electronics--simple R-C-L (resistor-capacitor-inductor) circuits. The electromagnetic waves passing through arrays of tiny resistors, capacitors, inductors and other dielectric materials positioned in free space can be bent down any designer-specified path. In 2000, Smith, who was then at the University of California- San Diego, and his colleagues demonstrated a composite metamaterial that used embedded passive resonators to bend microwaves backward. The circuit elements that the team used were based on the theoretical analysis provided by Pendry and his colleagues in London. Schurig recently sat down with technology editor R. Colin Johnson to describe how the cloaking device works, and what EEs can do to turn this science fiction idea into fact.

Monday, August 07, 2006

"MATERIALS: Phonons may drive high-Tc superconduction"

Just last month, an Oak Ridge National Laboratory team offered evidence that magnetic resonance was a more likely candidate than phonons as the mechanism behind high-temperature superconducting. But now a research team at Cornell University (Ithaca, N.Y.) has countered that careful characterization at the atomic scale reveals that the mechanism causing high-temperature superconducting may be phonons after all. Since the discovery of high-temperature superconducting materials, no one has convincingly explained why they work. Low-temperature superconducting is caused by a boson mode—a phonon—that interacts with electrons. But electron-phonon interaction in high-temperature superconductors has been elusive to observe, giving rise to the magnetic-resonance hypothesis. If the mechanism that enables high-temperature superconducting can be quantified, then designers worldwide could craft materials that eventually would enable room-temperature superconductivity.