Pages: pp. 17-19
A researcher has come up with a possible solution to one of nanotechnology's big challenges: finding tiny, easily accessible, affordable generators to power the ultrasmall devices that the approach could yield.
The output could one day power tiny devices "such as nanosensors or in-vivo biological sensors built on single nanowires or ultrathin semiconductor films. They could range in size from 100 nanometers to several microns," according to Georgia Tech University research scientist Xudong Wang.
The generators could also eventually power larger systems such as cardiac pacemakers, wireless sensors, or personal electronic devices such as digital-audio players or cellular phones.
Wang created a nanoscale generator that converts ultrasonic waves—high-frequency vibrations—into electricity. He fabricated the device with 50-nanometer-wide wires made of zinc oxide, an optical semiconducting material.
Other nanogenerator researchers had used this material, but their wires tangled in production. This was a problem because nanowires must have the same orientation for users to manipulate and integrate them into a device.
In addition, Wang explained, "For our nanogenerator, we need all the nanowire to generate electricity simultaneously and continuously, which can only be realized when all the nanowires are vertically standing and separated from each other."
Wang said his group is the first to grow precisely positioned, vertically aligned zinc oxide nanowires.
"To have all of them standing vertically, we needed to make sure their growth direction is perpendicular to the substrate," he explained. "This is controlled by many parameters such as the substrate, [wire-growth] catalyst, pressure, and temperature."
The Georgia Tech researchers used gold as the catalyst. Growing the wires at 900 to 1,000 degrees Celsius vaporized the zinc oxide and yielded droplets of a gold-zinc oxide alloy, from which the nanowires were grown.
To generate electricity, Wang's team used forests of nanowire arrays on a gallium-nitride substrate—measuring between 30 and 50 nanometers wide and 1 to 2 microns long—that served as one electrode. They made the second electrode of platinum-coated silicon.
Figure Georgia Tech University researchers have developed a tiny nanogenerator that could generate power for nanotechnology devices. The technology uses ultrasonic waves to squeeze two electrodes together, causing the nanowires between them to flex. When flexed, strains formed on the wire's side surfaces, creating electric potential that generates a current when connected to a circuit.
In one experiment, Wang and a colleague generated a very small current by bending the nanowires with the tip of an atomic-force microscope, which created an ultrasonic wave. In a different experiment, a wave generator produced the ultrasonic waves.
Either way, the waves squeezed the two electrodes together, causing the nanowires between them to flex. The wire's zinc oxide is a piezoelectric material. When flexed, Wang explained, strains form on the wire's sides, creating electric potential that generates a current when connected to an electronic circuit.
He said his team has increased the nanogenerator's output from an initial 0.6 to 0.7 nanoamperes to 600 nanoamperes, largely by increasing the number of nanowires and making them more uniform.
Wang said it could be three to five years before devices such as his generator are used commercially.
A company has developed a beta version of a tool that uses advanced Semantic Web principles to help users better organize, explore, analyze, and share information.
Lew Tucker, Radar Networks' vice president of engineering, said Twine ( www.twine.com) uses two Semantic Web technologies:
These technologies are considered important parts of the Semantic Web, in which computers store data in machine-readable formats for easy retrieval, usage, sharing, and integration by applications, agents, and virtual assistants.
Radar Networks' tool either automatically places or lets users put information they gather online—from e-mail, web searches, PowerPoint presentations, videos, or documents—into a twine, which is basically an online topic-based knowledge-sharing network.
"People visit www.twine.com and can then add notes, pictures, documents to their own private collection," explained Tucker. They can then share information via twines. All the information is stored on Twine's servers except material the service points to on, for example, a video- or photo-sharing site.
For purposes of sharing information, users can designate whether the twines are open to the public or only to members of a specific group, noted Tucker.
Upon encountering an e-mail, text, or other file, the system creates a bookmark representation of the page, including metatags, title, and description. This makes it easier for other Twine participants to find the information when they use the application to conduct searches.
Twine automatically analyzes, classifies, tags, and identifies relationships between pieces of information using advanced machine-learning and natural-language processing algorithms.
In addition, Twine includes a graph that shows the relevancy and importance of information, Tucker said. Relevancy could be based on the way Twine users weigh their search, such as giving more credence to certain sources. As the researchers evolve the system, other properties—such as the number of links referring to a site, a potential indicator of its importance—may be used to prioritize search results, he noted.
The tool uses RDF and OWL to make the information it contains easier to understand, use, and share.
"This is a hot area in enterprise software," said Susan Feldman, research vice president for search and digital marketplace technologies with market-research firm IDC.
Vendors are developing many Semantic Web tools, but wide adoption will depend on increasing education and the understanding of semantic technologies more than on tool availability per se, noted Eric Axel Franzon, vice president of Semantic Universe, an organization that promotes awareness of semantic technologies.
A researcher and software architect with the One Laptop per Child project has taken an innovative approach to eliminating the need for antivirus products in the computers that OLPC plans to sell for $100 or less to developing countries for use by needy children.
OLPC charged its director of security architecture, Ivan Krstić, with creating a secure system that would not require user intervention, a lot of technical support, or ongoing updates. According to Krstić, this would allow the laptops "to be usable by our youngest target audience: children as young as five."
He then built the Bitfrost security platform, named after Norse mythology's secure Bifröst bridge between the realm of the gods and the realm of mortals.
The platform is designed to dramatically raise the bar for would-be hackers and render many kinds of attacks useless, he explained.
Bitfrost seamlessly places every program on the Linux-based computer in a separate virtual operating system, extending an approach known as container-based isolation. This approach isolates a program and keeps it from accessing or even being aware of other applications, the hard drive, or the main OS. Thus, problems with an individual program, such as viruses or spyware, can't cause difficulties elsewhere. This also neutralizes botnet threats, Krstić said.
In addition, the system lets programs operate on data but doesn't let hackers who attack an application exploit the information it contains.
OLPC has also implemented a mechanism that prevents hackers from changing the system's BIOS code, via a malicious program or even the operating-system kernel.
Security expert and University of Pennsylvania professor David J. Farber noted that he has ordered the system to evaluate it for himself. He said, "My casual observation is that virtualization works to a large degree." However, Farber added, he wants to check whether it is possible that malicious data could damage the virtual machine itself, which could then harm the rest of the computer.
OLPC, founded by MIT professor Nicholas Negroponte in 2005, has entered the mass-production phase. Uruguay placed the first order of 100,000 laptops, and initial deployment began in December 2007.
Carnegie Hall will be seeing a very unusual orchestra in April, one that uses laptops instead of musical instruments.
The Princeton Laptop Orchestra ( http://plork.cs.princeton.edu), an ensemble that performs music via computers and specially designed speakers, plans to play the famous New York City concert hall with the conventional American Composers Orchestra on 25 April.
Orchestra members, composers, and conductors include Princeton University undergraduate and graduate students and faculty members. The musicians play 15 "instruments" consisting of identical hardware but different software and control devices.
They make music via sound synthesis and the signal processing of live audio input, explained Princeton assistant professor of music Dan Trueman, one of the group's founders, conductors, and composers.Princeton University's Laptop Orchestra performs music via computers and specially designed speakers. The group has played in places such as Chicago and Washington, D.C., and will appear in New York City's Carnegie Hall in April.
The musicians work with a Bowed Sensor-Speaker Array—a combination of multichannel, omnidirectional speakers with sensors for audio control that Trueman helped design—as their sound source. Participants use a bow to play a fingerboard attached to the speakers.
The orchestra members also work with identically equipped Apple MacBooks and software based on the Max/MSP graphical programming environment, the SuperCollider programming environment and language for real-time audio synthesis and algorithmic composition, and the ChucK audio programming language.
When musicians play their instruments, the input data travels to a laptop that digitizes it and converts it into sound. The system uses signal processing and algorithms to synthesize the sounds of various acoustic instruments, said Trueman. It can also produce music via sound samples. The composers write applications that interpret the sensor data and map it to various types of sound.
Some orchestra members have used accelerometers inside the laptop that detect motion, such as the tilting of the machine, which the system uses to control volume, pitch, and other aspects of the music.
The orchestra has primarily played original music, written in standard musical notation or a unique graphic tablature.
The group has played in places such as Chicago and Washington, D.C. Former member Ge Wang is forming a laptop orchestra at Stanford University, where he now teaches.
Trueman, a classically trained violinist, said he wanted to take electronic music beyond the traditional confines of the studio by adding a live-performance component.