Monday, June 27, 2005

"CHIPS: Molecular gates spin photons from chemicals"

The human eye employs millions of nanoscale photoreceptors that output chemical signals when they are stimulated by photons. By reversing that process, a team of researchers in Northern Ireland and Japan has engineered a tiny molecular transistor that emits photons when supplied with the right chemicals. The researchers showed just how small logic gates can be made when using individual molecules � in this case, 3 nanometers in radius. And besides demonstrating the ability to operate nanoscale molecular logic gates (a capability that has been shown elsewhere in solutions inside test tubes), the team showed how such gates could be embedded in an organic thin film. Arrays of logic gates could be assembled on such membranes, heralding a comprehensive architecture for future molecular-sized computers, the team said.

Monday, June 20, 2005

"CHIPS: Soft-lithography method harnesses DNA"

A soft-lithography technique that harnesses deoxyribonucleic acid (DNA) as a self-reproducing template is being developed at the Massachusetts Institute of Technology's Supramolecular Nano Materials Group. Researchers in the SuNMag project have demonstrated a self-assembling method, dubbed nanocontact printing, that transfers subnanoscale patterns from a master wafer to any number of production wafers. In doing so, the method sidesteps the problems of both photolithography and nanoimprinting.
"What we have developed is a method that is able to reproduce DNA patterns from one surface to another," said materials scientist Francesco Stellacci, who heads the project. Stellacci, who describes the technique as using "DNA strands as Gutenberg movable type," performed the work with EE professor Henry Smith, EE graduate student Tim Savas and materials science graduate student Amy Yu. Yu described Stellacci's new method as marshaling "nature's most efficient printing technique: the DNA/RNA [ribonucleic acid] information transfer."

"PC-BOARDS: Low-temperature adhesives putting heat on solder"

Low-temperature, low-profile conductive adhesives are poised to enable ultraflat-panel displays for cell phones, laptop computers and wall-mounted televisions.
Going beyond recommendations to take the lead out of solder, researchers at the Georgia Institute of Technology are working to build a world of electronics free of metal-solder itself. While the interconnect trade association IPC and other organizations are pursuing a no-lead goal, they "are only looking at low-temperature adhesives as one of many different alternatives," said Ching-Ping Wong, professor of materials science and engineering at Georgia Tech (Atlanta). "We believe that our approach to low-temperature adhesives has much greater potential because we are solving the fundamental problems that make others hesitant to use them." Other approaches to low-temperature conductive adhesives have been afflicted with self-alignment and low-carrier mobility problems. Wong's group, which included graduate student Grace Yi Li and post-doctoral researcher Kyoung-sik Moon, is working to overcome those obstacles.

Wednesday, June 15, 2005

"SYSTEMS: U.S. expected to dominate supercomputer list"

U.S. supercomputer makers are expected to dominate this year's list of the world's fastest supercomputers. The list of world's fastest supercomputers will be released at the 20th International Supercomputer Conference (June 22-24) in Heidelberg, Germany. IBM Corp. is expected to snag three of the top five slots, with Silicon Graphics Inc. (Mountain View, Calif.) taking third. NEC Corp. is the only non-U.S. supercomputer maker expected to make the list. The fastest supercomputer list will be released by the TOP500 organization, which is an independent judge of supercomputer performance. The TOP500 project originated in 1993 and each year provides a nonpartisan method of measuring supercomputer performance. IBM's BlueGene/L supercomputer is expected to remain at the top of the TOP500 list, delivering peak performace of 91.8 teraflops.

Monday, June 13, 2005

"CHIPS: Silica, dye yield new kind of quantum dot"

An alternative to quantum dots-encapsulating organic dyes in a silica matrix-has been developed by researchers at Cornell University. The process, they said, could cut the cost of making optical computing devices, and render them chemically inert as well. The Cornell approach is a departure from the way most quantum dots are fabricated: nanoparticles being doped with heavy metals like cadmium-selenium. "We have encapsulated multiple organic dyes in the core of a nanoparticle," said Ulrich Wiesner, professor of materials science and engineering. "The core is then encapsulated into a pure silica shell for protection." The core-shell architecture can be used in applications ranging from flat-panel displays to medical imaging to sensor and optical lasers that emit a single photon at a time, he said. Wiesner's nanoparticles, which he calls "Cornell dots," are novel. They begin with a core 2.2 nanometers in diameter that contains a few colored dye molecules. The molecules are surrounded with 22.8 nm of silicon dioxide, resulting in quantum dots measuring 25 nm in diameter. This core-shell architecture, Wiesner said, makes his quantum dots as much as 30 times brighter than conventional fluorescent dyes. "The particles are very, very bright, because they act independently rather than quenching each other," he said. "Our dots are almost as bright as quantum dots." Wiesner collaborated with fellow Cornell professors Watt Webb and Barbara Baird. They were assisted by postdoctoral researcher Mamta Srivastava and graduate students Hooisweng Ow and Daniel Larson. The silicon dioxide-or silica-shell also prevents the dyes from fading, while allowing a variety of colors to be produced without changing the diameter of the core. The silicon dioxide-coated nanoparticles are also chemically inert, making them safer to manufacture and handle.

Monday, June 06, 2005

"CHIPS: Organic molecule switches like a transistor"

Researchers at the University of Alberta have successfully demonstrated a single-molecule switch and transistor. "There is no longer a question of whether a single molecule can be used as a switch; we have shown that it can be done," professor Robert Wolkow said. "Also, we have demonstrated how you can get two electrodes to act like the three electrodes normally associated with a transistor. In particular, we have shown that a chargeable atom can act as a gate using the same electrode that is also acting as the source." But there's a caveat: "We don't yet have any kind of realistic temporal control" of the switch," Wolkow said. "Right now, it takes minutes to turn it on and off." Working with postdoctoral fellows Paul Piva and Stanislav Dogel, as well as graduate student Janik Zikovsky, Wolkow's team placed a single organic molecule on a silicon substrate so that the molecule acted as the transistor channel, with the substrate acting as a back gate for switching. The work was performed in cooperation with staff scientists and their postdoctoral assistants at the National Institute for Nanotechnology, which is a part of the National Research Council of Canada, as well as with professor Werner Hofer of the Surface Science Research Centre at Britain's University of Liverpool. Wolkow's group has been working with many organic molecules, learning how to bond them to silicon substrates and get them to line up into rows. But the current demonstration is the first to inject electrons into the molecule.

"CHIPS: Vision chips' mimic eye, brain functions"

As the long development of charge-coupled device (CCD) and CMOS active-pixel sensor technology begins to pay off in the form of affordable all-electronic still and video cameras, a second wave of solid-state imaging chips with very different capabilities is emerging from research labs around the world. Called "vision chips," these silicon imaging devices are typically parallel computers on a chip implementing a processor per pixel to mimic neural processing circuitry in the retina. Rather than striving for high resolution and faithful color reproduction, vision chips capture other aspects of the eye and brain functions, such as edge and motion detection. Target applications include security systems, autonomous robots, artificial implantable retinas and biochemical analysis. A few projects have reached the commercial stage, including a real-time in vivo glucose-monitoring system from Array Vision Engineering Co. (Alachua, Fla.) and a security camera being marketed by Pixim Inc. (Mountain View, Calif.), which has commercialized research from a project at Stanford University. An example of state-of-the-art vision chip technology surfaced at last month's International Symposium on Circuits and Systems in Kobe, Japan, where EE professor Piotr Dudek of the University of Manchester (England) demonstrated a third-generation device with 16,384 pixel-processors that mimics the retina. Called Scamp, for "SIMD current-mode analog-matrix processor," the chip integrates an arithmetic-logic unit, memory, control logic and an input/output circuit behind each and every pixel. The Scamp-3 vision chip promises to enable robots and automated inspection, surveillance and vehicle-guidance systems to "see" in a manner similar to human sight. The Scamp-3 is a 1-cm2 chip fabricated in 0.35-micron CMOS that arranges its 16,384 pixel-processors in a 128 x 128 array. Each pixel-processor measures 50 microns2 and consumes 12 microwatts when running at 1.25 MHz, giving the chip a computational power efficiency of 104 billion instructions per second per watt.

"NANOTECH: Conference plots future of electronics"

Presenters at the First International Nanotechnology Conference on Communication and Cooperation last week identified the key issues facing nanotechnology. The San Francisco conference, which hosted more than 36 presenters from nearly a dozen countries, kicked off with overviews of the state of nanotechnology in the United States, Europe and Japan. A dozen presentations zeroed in on the key issues and challenges facing future EEs designing nanoscale devices. Researchers spoke about nanowires, organic large-area solar cells, molecular electronics, spintronics, bioanalytic systems and nanotechnology in medicine. Speakers looked at the biological and societal implications of nanotechnology, including the use of organic materials in the fabrication of everything from large-area electronics to artificial organs. Also discussed were the ethical issues facing the safe deployment of processing methodologies and end-user applications in nanotechnology that hold the potential to shift the worldwide economic balance. Presenters speculated that chemistry, especially nanoscale catalysts, would be the first technological area to be revolutionized by nanotechnology, followed by semiconductors that employ nanotechnology to indefinitely extend Moore's Law, with a sprinkling of medical breakthroughs along the way.