Friday, February 25, 2005

"NANOTECH: NIST crafts molecular solder iron"

While molecular-size components such as diodes and resistors built from individual atoms have been demonstrated in laboratories worldwide, their exceedingly small size creates some fundamental problems. One is how to solder these tiny components into circuits. Now the National Institute of Standards and Technology (NIST) is offering a patented solution: a molecular soldering iron for researchers who are assembling electronics one atom at a time. "We patented this process because we knew of the need for something like a molecular soldering iron from U.S. researchers," said NIST researcher Chris Zangmeister, who said that NIST is "cooperating with universities and companies like Hewlett-Packard" on the project. The process, co-developed by Zangmeister and fellow NIST researcher Roger van Zee, connects molecular components with copper by selectively coating only the ends that need to be soldered. A layer of molecular components is first assembled with all their ends pointing upward from the substrate. The dangling ends get coated, so that future devices can be soldered into a second layer in a multilayered-chip construction similar to the way silicon chips are built.

"NANOTECH: nano-sensor 'immune' to toxins it detects"

Engineers at the University of Texas (Austin) and Georgia Institute of Technology say they have built a reusable sensor that can detect nerve gas and similar toxic airborne agents without getting contaminated itself. By integrating nanoscale techniques with microelectromechanical systems, the team has created a so-called nanoelectromechanical system that is sensitive enough to detect as few as 50 molecules per billion of nerve gas. "Sensor poisoning is a persistent problem with other designs," said UT professor Li Shi. "Their active element is not a single-crystal film like ours. Nor do others operate their sensors at 500 degrees C." He described the nerve gas sensor, which he designed with professor Zhong Lin Wang from Georgia Tech, as "completely self-cleaning, yet small and low-power enough to be wearable, since it can run off a battery with a power consumption of only 3 to 4 milliwatts." Choongho Yu, a postdoctoral fellow at Lawrence Berkeley National Laboratory, assisted in the work.

Thursday, February 17, 2005

"QUANTUM: Nano mechanical oscillator makes big wave"

A 1.5-GHz silicon "comb" that is said to be the world's fastest nanoscale electromechanical system (NEMS) is nevertheless huge on the quantum scale: The oscillation of its teeth exhibit the world's biggest quantum motion. According to the research project team, headed by Boston University professor Pritiraj Mohanty, the teeth of the comb exhibit quantum-mechanical motion by jumping between two discrete positions without passing through the physical space between them. "We believe that our system is truly a macroscopic quantum system, [but since] it's a new phenomenon, it's best not to be guided by expectations based on conventional wisdom. The philosophy here is to let the data speak for itself," said Alexei Gaidarzhy, one of the principal researchers in Mohanty's group. Other researchers in Mohanty's group included Guiti Zolfagharkhani, a graduate student, and Robert Badzey, a post-doctoral Fellow in Boston University's Physics Department.

Friday, February 11, 2005

"NANOTECH: Hearing aids given nanotech spin"

Nanotech hearing aids due out next month will carry spintronic sensors that automatically adjust to accommodate the source of sounds. If a phone is held to the wearer's ear, for example, the hearing aid will automatically switch modes without the person's intervention. Giant magnetoresistance (GMR) sensors from NVE Corp. (Eden Prairie, Minn.) are at the heart of the hearing aids, built by Starkey Laboratories (Minneapolis). The sensors are based on a chip that uses electron spin rather than charge to store information. By automatically switching modes, the sensor frees a wearer from today's need to switch either manually or with a bulky switch. The sensor, one-third the size of the switch's coil, is built from nanoscale layers of magnetic thin films just a few atomic layers thick. The result, say both companies, is a magnetic sensor that's smaller, more precise and less power-hungry than devices available today. "Our hearing aids can now be built much smaller and perform significantly better," said Dale Lizakowski, a quality engineer at Starkey Labs. "I have personally worn and tested the GMR sensor, and it performs well above and beyond any other technology for switching sensitivity, overall reliability and ultrasmall size."

Thursday, February 10, 2005

"MEMS: cochlea is closest yet to real thing"

A MEMS-based implant holds the promise of an artificial ear that would let the deaf hear without external electronics. The device mimics the snail-shaped structure of the inner ear, the cochlea, that makes hearing possible. The fully integrated implant-the size of a real cochlea-has been fabricated with backside through-wafer etching using an inductively coupled plasma deep-reactive ion etch. It was based on a microelectromechanical system designed by University of Michigan associate professor Karl Grosh. While other researchers have fabricated micromachined devices that mimic aspects of the cochlea, Grosh said, "our design differs from previous work by using a beam-array structure in a fully micromachined, liquid-filled two-duct structure."

Monday, February 07, 2005

"QUANTUM: Semiconductor aerogels advance sensors"

Semiconducting aerogels have recently been demonstrated that cast quantum dots into a sparse, crystalline-like matrix with more space than substance. Such porous materials could enable supersensitive sensors and superefficient plastic photovoltaics, said the Wayne State University research team pursuing the project. That's because the very porous structure, through which environmental molecules can waft, has the maximum possible amount of surface area, essentially enabling every embedded quantum dot to sense the environment independently. "We have found that the best way to engineer nanoparticles with novel electronic properties is to replace the oxides that everybody else uses with a semiconductor," said professor Stephanie L. Brock, leader of the semiconducting-aerogel research group at Wayne State (Detroit). "Instead of an oxide, which is an insulator, we use a semiconducting material such as cadmium selenide or cadmium-, zinc- or lead sulphide."

Friday, February 04, 2005

"NANOTECH: Crossbar logic shrinks to nanoscale"

Hewlett-Packard Co.'s HP Labs has designed a crossbar switch that may one day allow the company to pack the power of a traditional microprocessor arithmetic logic unit into just a few square microns. Current bus structures applied at the nanoscale are akin to trying to drain a swamp with a soda straw � domains measuring a few nanometers across are just too much of a bottleneck for traditional input/output schemes. Hewlett-Packard (Palo Alto, Calif.) claims that its crossbar switch design has broken that bottleneck by reducing the I/O problem by 128 to 1, while providing a bistable latching architecture for cascading any number of layers of nanoscale memory and logic. "A single pair of lines can now control 100 or more switches at the same time," said Phil Kuekes, senior architect at HP Labs' Quantum Science Research group. "Since our latches can also restore the logic levels of these bits, we can now gang together any number of layers of logic and memory functions. Next we want to show we can perform traditional logic functions with crossbar switches, but at a density you can't achieve today with transistors � such as packing a 128-bit ALU into just a few square microns."