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Nanogenerator Fueled by Vibrations
An array of zinc-oxide nanowires that generates current when vibrated with ultrasonic waves could provide a new way to power biological sensors and nanodevices.
An array of zinc-oxide nanowires that generates current when vibrated with ultrasonic waves could provide a new way to power biological sensors and nanodevices.
Using ultrasonic waves to vibrate an array of zinc-oxide nanowires, researchers at Georgia Tech have made a tiny generator that can produce direct current. By taking advantage of the fact that zinc-oxide nanowires are piezoelectric--they can convert mechanical energy into electricity--and by finding a way to collect electricity from multiple nanowires, the researchers have taken a big step toward a practical nanoscale power generator.
"We can make each and every wire simultaneously and continuously produce electricity," says Zhong Lin Wang, a professor of materials science at Georgia Tech, who led the work. In a Science paper published this week, Wang and his colleagues demonstrate a prototype device, about two millimeters square, that generates around 0.5 nanoamperes of current for more than an hour.
"The technique essentially provides a new method of power generation," says Pulickel Ajayan, a materials engineering professor at Rennselaer Polytechnic Institute. He says that the generator could be coupled with devices that are difficult or inefficient to power using conventional means.
One important application is powering implantable biological sensors. According to Thomas Thundat, who researches nanoscale biological sensors at Oak Ridge National Laboratory, current battery technology limits the use of microelectromechanical sensors that measure cancer biomarkers, blood pH, and glucose. These sensors are getting smaller and smaller, but conventional chemical batteries can't keep up. "[The batteries] are huge and they run out of power...most of the time it's the battery that's big compared to the sensing part," Thundat says. "We have always been looking for very small power sources that don't need refilling." The new nanowire generator looks like a promising answer, he says. It could be implanted in the body, and, driven by muscle contractions, blood flow, or external vibrations transmitted through tissue, it could power the sensors.
The generator could also drive nanodevices. Wang's research group has previously made nanowire pressure sensors that can detect extremely small piconewton forces as well as nanowire gas sensors. (See "A Nano Pressure Sensor.") Instead of an external battery, these devices could run on wind or water flow using the new generator.
A key innovation that has led to the nanowire generator is a new electrode design. The surface of the platinum-coated electrode has a zigzag shape like the teeth of a saw: it has alternating parallel peaks and trenches. This zigzag electrode goes on top of an array of upright zinc-oxide nanowires, and its teeth can push many nanowires at the same time if it moves up and down.
To vibrate the electrode, the researchers package the device, put it in water, and expose it to ultrasonic waves. As the zigzag electrode moves up and down, its peaks push and bend the nanowires, which generate electric current that the electrode collects simultaneously. "The wires can be compressed, can be vibrated left or right--it doesn't matter: all the current adds up in the same direction," Wang says.
This is the first demonstration of a direct current output from nanowires that are driven by mechanical energy, says Charles Lieber, a chemistry professor at Harvard University. The new development is a "key step towards novel, cost-effective, adaptable, and mobile applications of nanogenerators in nanotechnology," he says.
For real-world applications, the current generated by the nanogenerator would need to be higher and more stable. Wang's research group is working on improvements toward that goal. Right now, the nanowires are grown randomly, and the researchers estimate that anywhere between 250 and 1,000 nanowires contribute to the current. This is less than 1 percent of all the wires in the array, Wang says. An important next step is to grow a more regular array of nanowires that are uniform in size and height. Matching the nanowire pattern with the pattern on the electrode would utilize all the nanowires, increasing the current output and making it more stable, he says.
The research team also needs to increase the generator's lifetime. It runs for a little more than an hour right now, and Wang says the researchers are not sure why it dies after that time. As a proof of concept, though, Thundat says that this work is a "major advancement in the power-generation area."
"We can make each and every wire simultaneously and continuously produce electricity," says Zhong Lin Wang, a professor of materials science at Georgia Tech, who led the work. In a Science paper published this week, Wang and his colleagues demonstrate a prototype device, about two millimeters square, that generates around 0.5 nanoamperes of current for more than an hour.
"The technique essentially provides a new method of power generation," says Pulickel Ajayan, a materials engineering professor at Rennselaer Polytechnic Institute. He says that the generator could be coupled with devices that are difficult or inefficient to power using conventional means.
One important application is powering implantable biological sensors. According to Thomas Thundat, who researches nanoscale biological sensors at Oak Ridge National Laboratory, current battery technology limits the use of microelectromechanical sensors that measure cancer biomarkers, blood pH, and glucose. These sensors are getting smaller and smaller, but conventional chemical batteries can't keep up. "[The batteries] are huge and they run out of power...most of the time it's the battery that's big compared to the sensing part," Thundat says. "We have always been looking for very small power sources that don't need refilling." The new nanowire generator looks like a promising answer, he says. It could be implanted in the body, and, driven by muscle contractions, blood flow, or external vibrations transmitted through tissue, it could power the sensors.
The generator could also drive nanodevices. Wang's research group has previously made nanowire pressure sensors that can detect extremely small piconewton forces as well as nanowire gas sensors. (See "A Nano Pressure Sensor.") Instead of an external battery, these devices could run on wind or water flow using the new generator.
A key innovation that has led to the nanowire generator is a new electrode design. The surface of the platinum-coated electrode has a zigzag shape like the teeth of a saw: it has alternating parallel peaks and trenches. This zigzag electrode goes on top of an array of upright zinc-oxide nanowires, and its teeth can push many nanowires at the same time if it moves up and down.
To vibrate the electrode, the researchers package the device, put it in water, and expose it to ultrasonic waves. As the zigzag electrode moves up and down, its peaks push and bend the nanowires, which generate electric current that the electrode collects simultaneously. "The wires can be compressed, can be vibrated left or right--it doesn't matter: all the current adds up in the same direction," Wang says.
This is the first demonstration of a direct current output from nanowires that are driven by mechanical energy, says Charles Lieber, a chemistry professor at Harvard University. The new development is a "key step towards novel, cost-effective, adaptable, and mobile applications of nanogenerators in nanotechnology," he says.
For real-world applications, the current generated by the nanogenerator would need to be higher and more stable. Wang's research group is working on improvements toward that goal. Right now, the nanowires are grown randomly, and the researchers estimate that anywhere between 250 and 1,000 nanowires contribute to the current. This is less than 1 percent of all the wires in the array, Wang says. An important next step is to grow a more regular array of nanowires that are uniform in size and height. Matching the nanowire pattern with the pattern on the electrode would utilize all the nanowires, increasing the current output and making it more stable, he says.
The research team also needs to increase the generator's lifetime. It runs for a little more than an hour right now, and Wang says the researchers are not sure why it dies after that time. As a proof of concept, though, Thundat says that this work is a "major advancement in the power-generation area."
SOURCE : www.technologyreview.com
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at
7:11 AM
Providing Web Services: Moving Away From Place
During the early years of the Web, before content had semantic meaning, sites were developed as a collection of “pages.” Sites in the 1990s were usually either brochure-ware (static HTML pages with insipid content) or they were interactive in a flashy, animated, JavaScript kind of way. In that era, a common method of promoting sites was to market them as “places”—the Web as a virtual world complete with online shopping malls and portals.
In the late 90s and especially the first few years of the 21st century, the advent of XML technologies and Web services began to change how sites were designed. XML technologies enabled content to be shareable and transformable between different systems, and Web services provided hooks into the innards of sites. Instead of visual design being the interface to content, Web services have become programmatic interfaces to that same content. This is truly powerful. Anyone can build an interface to content on any domain if the developers there provide a Web services API.
Two great examples of the shift away from place to services on the Web are Amazon.com and eBay, both of which provide an immense amount of commercial data in the form of Web services, accessible to any developer who wants it. An interesting interface built using eBay’s Web services is Andale, a site that tracks sales and prices to give auction sellers a better idea of what items are hot and how much they’ve been selling for.
source : digital web magazine
During the early years of the Web, before content had semantic meaning, sites were developed as a collection of “pages.” Sites in the 1990s were usually either brochure-ware (static HTML pages with insipid content) or they were interactive in a flashy, animated, JavaScript kind of way. In that era, a common method of promoting sites was to market them as “places”—the Web as a virtual world complete with online shopping malls and portals.
In the late 90s and especially the first few years of the 21st century, the advent of XML technologies and Web services began to change how sites were designed. XML technologies enabled content to be shareable and transformable between different systems, and Web services provided hooks into the innards of sites. Instead of visual design being the interface to content, Web services have become programmatic interfaces to that same content. This is truly powerful. Anyone can build an interface to content on any domain if the developers there provide a Web services API.
Two great examples of the shift away from place to services on the Web are Amazon.com and eBay, both of which provide an immense amount of commercial data in the form of Web services, accessible to any developer who wants it. An interesting interface built using eBay’s Web services is Andale, a site that tracks sales and prices to give auction sellers a better idea of what items are hot and how much they’ve been selling for.
source : digital web magazine
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TECHNOLOGY
at
10:17 PM
Crawling robot reveals how fish evolved
The first animal to crawl onto land from the ocean probably looked a bit like today's salamander, and researchers have wondered how it was able to switch from swimming to walking. Now, European scientists have built a robot with a primitive electric nervous system that they say mimics that change in motion. The robot doesn't look much like a salamander it's nearly a yard long and made of nine bright yellow plastic segments each containing a battery and microcontroller but it does seem to move like one. The scientists chose the amphibious salamander as a model because the animal more closely resembles the first land-dwelling vertebrates. The point was to understand how a spinal cord developed to direct a swimming motion that could handle the different coordination needed between a body and its limbs for walking, according to the team led by Auke Jan Ijspeert of the Ecole Polytechnique Federale in Lausanne, Switzerland. So they first designed a basic nervous system modelled on that of the lamprey, a long, primitive eel-like fish. Then that design was modified to show how it could evolve into a nervous system that also could control walking. And to prove their point, they built the salamander robot which walks across floors, down the beach and even manages to swim in Lake Geneva. Its swimming motion uses undulations like the lamprey, while on land the robot uses a slow stepping gait with diagonally opposed limbs moving together while the body forms an S-shape. The work, the researchers reported on Friday in the journal Science, is "a demonstration of how robots can be used to test biological models, and in return, how biology can help in designing robot locomotion controllers." Studies of the robot show that our fishy ancestors likely used their primitive brains to make the evolutionary leap from water worlds to terra firma. The research was funded by the Swiss National Science Foundation and the French Ministry for Research and Technology.
SOURCE : THE TIMES OF INDIA
The first animal to crawl onto land from the ocean probably looked a bit like today's salamander, and researchers have wondered how it was able to switch from swimming to walking. Now, European scientists have built a robot with a primitive electric nervous system that they say mimics that change in motion. The robot doesn't look much like a salamander it's nearly a yard long and made of nine bright yellow plastic segments each containing a battery and microcontroller but it does seem to move like one. The scientists chose the amphibious salamander as a model because the animal more closely resembles the first land-dwelling vertebrates. The point was to understand how a spinal cord developed to direct a swimming motion that could handle the different coordination needed between a body and its limbs for walking, according to the team led by Auke Jan Ijspeert of the Ecole Polytechnique Federale in Lausanne, Switzerland. So they first designed a basic nervous system modelled on that of the lamprey, a long, primitive eel-like fish. Then that design was modified to show how it could evolve into a nervous system that also could control walking. And to prove their point, they built the salamander robot which walks across floors, down the beach and even manages to swim in Lake Geneva. Its swimming motion uses undulations like the lamprey, while on land the robot uses a slow stepping gait with diagonally opposed limbs moving together while the body forms an S-shape. The work, the researchers reported on Friday in the journal Science, is "a demonstration of how robots can be used to test biological models, and in return, how biology can help in designing robot locomotion controllers." Studies of the robot show that our fishy ancestors likely used their primitive brains to make the evolutionary leap from water worlds to terra firma. The research was funded by the Swiss National Science Foundation and the French Ministry for Research and Technology.
SOURCE : THE TIMES OF INDIA
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TECHNOLOGY
at
2:29 AM
