Monday, November 08. 2010
Via MIT Technology Review
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A device containing piezoelectric nanowires can now scavenge enough energy to power small electronic devices.
By Katherine Bourzac
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Power flex: This material contains piezoelectric nanowires. When flexed, it produces enough power to drive a liquid-crystal display.
Credit: ACS/Nano Letters |
Devices that harvest wasted mechanical energy could make many new advances possible—including clothing that recharges personal electronics with body movements, or implants that tap the motion of blood or organs. But making energy-harvesting devices that are compact, flexible, and, above all, efficient remains a big challenge. Now researchers at Georgia Tech have made the first nanowire-based generators that can harvest sufficient mechanical energy to power small devices, including light-emitting diodes and a liquid-crystal display.
The generators take advantage of materials that exhibit a property called piezoelectricity. When a piezoelectric material is stressed, it can drive an electrical current (applying a current has the reverse effect, making the material flex). Piezoelectrics are already used in microphones, sensors, clocks, and other devices, but efforts to harvest biomechanical energy using them have been stymied by the fact that they are typically rigid. Piezoelectric polymers do exist, but they aren't very efficient.
Zhong Lin Wang, who directs the Center for Nanostructure Characterization at Georgia Tech, has been working on another approach: embedding tiny piezoelectric nanowires in flexible materials. Wang was the first to demonstrate the piezoelectric effect at the nanoscale in 2005; since then he has developed increasingly sophisticated nanowire generators and used them to harvest all sorts of biomechanical energy, including the movement of a running hamster. But until recently, Wang hadn't developed anything capable of harvesting enough power to actually run a device.
In a paper published online last week in the journal Nano Letters, Wang's group describes using a nanogenerator containing more nanowires, over a larger area, to drive a small liquid crystal display.
To make the generator, Wang's team dripped a solution containing zinc-oxide nanowires onto a thin metal electrode sitting on a sheet of plastic, creating several layers of the wires. They then covered the material with a polymer and topped it with an electrode. The resulting device is about 1.5 by two centimeters and, when compressed 4 percent every second, it produces about two volts, enough to drive a liquid-crystal display taken from a calculator. "We were generating 50 millivolts in the past, so this is an enhancement of about 20 times," says Wang.
In a paper published in Nano Letters this summer, Wang demonstrated a nanogenerator capable producing 11 milliwatts per cubic centimeter—enough to light up an LED. Wang notes that a pacemaker requires 5 milliwatts to run, an iPod 80 milliwatts. "We're almost there," he says.
The devices made by the Georgia Tech group are "getting into the realm where the power output is reasonable," says Michael McAlpine, professor of mechanical engineering at Princeton University and a 2010 TR35 awardee. "Getting impressive power outputs is a matter of scaling up," he adds.
Both Wang and McAlpine are looking to more efficient materials for making nanogenerators. Both have recently demonstrated making nanowires from PZT, a crystalline material that is standard in commercial piezoelectric devices. PZT, a compound that contains lead, zirconium, and titanium, is the most efficient piezoelectric material known, but making it into nanowires has been tricky because there are no good catalysts for growing PZT nanowires.
Wang and McAlpine have found different solutions to this problem. Wang treats his starting solution at high temperature and pressure, which does away with the need for an efficient catalyst. McAlpine grows a flat film of PZT, and then uses a mask to pattern nanowires through chemical etching. Energy harvesters made from PZT nanowires aren't as efficient as the zinc-oxide ones yet, but McAlpine says this is because he and Wang have only just begun to work with them.
Copyright Technology Review 2010.
Friday, May 14. 2010
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Machines made of DNA could one day assemble complex--and tiny--electrical and mechanical devices.
By Prachi Patel
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DNA assembly line: An atomic force microscope image shows gold nanoparticles on a DNA track.
Credit: Courtesy of Ned Seeman |
Its precise structure and ability to bind with other molecules makes DNA an attractive scaffolding material for nanotech researchers. Scientists have already used DNA to construct two-dimensional patterns, three-dimensional objects, and simple shape-changing devices. Now two teams of researchers have separately made complex programmable machines using DNA molecules.
Researchers from Columbia University, Arizona State University, and Caltech have made a device that follows a programmable path on a surface patterned with DNA. Meanwhile, researchers from New York University, led by DNA nanoarchitecture pioneer Ned Seeman, have combined multiple DNA devices to make an assembly line. The nano contraption picks up gold nanoparticles as it tumbles along a DNA-patterned surface.
The two machines, described in today's Nature journal, are a possible step forward in making DNA nanobots that could assemble tiny electrical and mechanical devices. DNA robots could also put together molecules in new ways to make new materials, says Lloyd Smith, a chemistry professor at the University of Wisconsin-Madison. "Robots might have the ability to position one molecule in a particular way so that a reaction happens with another molecule which might not happen if they randomly collide in solution," he says.
In the past, researchers have made simple machines such as tweezers and walkers that have also been fashioned from DNA. Tweezers open and close by adding specific DNA strands to the solution. Walkers are molecules with dangling strands, or legs, that bind and detach from other DNA strands patterned on a surface, in effect moving along the surface.
The nano walker made at Columbia University is a protein molecule decorated with three legs--single-stranded DNAzymes, synthetic DNA molecules that act as enzymes and catalyze a reaction. The legs bind to complementary DNA strands on a surface. Then they catalyze a reaction that shortens one of the surface strands, so that its attachment to the leg becomes weaker. That leg lets go and moves on to the next surface strand.
The walker follows a track of strands that the researchers pattern on the surface. It can take up to 50 steps--compared to the two or three steps taken by previous walkers. It stops when it encounters a sequence that cannot be shortened. "We show how to program [the walker's] behavior by programming the landscape," says Milan Stojanovic, a biomedical engineer at Columbia University who developed the walker. "It enables us to think about adding further complexity: more than one molecule interacting and more complicated commands on the surface. What we hope to do eventually is to be able to [use nanobots to] repair tissues."
Seeman and his colleagues at New York University combine three different DNA components to make an assembly line. They have DNA path, a walker, and a machine that can deliver or hold back a cargo of a molecule of gold. The machine is a DNA structure that can be set up to either put a gold nanoparticle-laden strand in the path of the walker or away from it. The walker has four legs and three single-stranded DNA hands that can bind to the gold.
The researchers demonstrated a system in which the walker passes three machines, each carrying a different type of gold particle. Each machine can be set up to either deliver its cargo or keep it, giving a total of eight different ways in which the walker can be loaded, leading to eight different products.
The advances represent continuing success in creating nano devices with increasingly complex functions. "[We're] moving from individual entities that do something interesting to systems of entities working on something with a more complex behavior and function," Smith says.
Copyright Technology Review 2010.
Friday, February 05. 2010
"The fissure was induced in order present an image which shows the characteristics of the coating. The image shows the SiO2 coating on a filament of a microfibre." Image: Nanopool
If it Works and is Safe, It Could Change the World
A special coating technically known as "SiO2 ultra-thin layering", but more memorably called "spray-on liquid glass", has been invented in Turkey at the Saarbrücken Institute for New Materials (the patent is owned by Nanopool). It is non-toxic promises to "protect virtually any surface against almost any damage from hazards such as water, UV radiation, dirt, heat, and bacterial infections [...] the coating is also flexible and breathable, which makes it suitable for use on an enormous array of products."
How Does it Work?
The details are still secret, but based on the information that is available, it seems like a pretty simple process. They purify silicon dioxide (SiO2, which is basically what you find in regular glass) from quartz sand, add water or ethanol molecules, and then through an unknown process are able to spray this on surfaces and get a very thin film of glass (100 nanometers, or 15-30 molecules) to stick. "The really clever part is that there are no added nano-particles, resins or additives- the coatings form and bond due to quantum forces." They also claim that it is very safe (these is already a lot of these types of inert molecules out in the wild, though I think it stills needs to be rigorously tested for toxicity).
An Almost Unbelievable List of Applications
Nanopool writes:
The flexible and breathable glass coating is approximately 100 nanometres thick (500 times thinner than a human hair), and so it is completely undetectable. It is food safe, environmentally friendly (winner of the Green Apple Award) and it can be applied to almost any surface within seconds . When coated, all surfaces become easy to clean and anti- microbially protected (Winner of the NHS Smart Solutions Award ). Houses, cars, ovens, wedding dress or any other protected surface become stain resistant and can be easily cleaned with water ; no cleaning chemicals are required. Amazingly a 30 second DIY application to a sink unit will last for a year or years, depending on how often it is used. But it does not stop there - the coatings are now also recognised as being suitable for agricultural and in-vivo application. Vines coated with SiO2 don't suffer from mildew, and coated seeds grow more rapidly without the need for anti-fungal chemicals. This will result in farmers in enjoying massively increased yields . Trials for in-vivo applications are subject to a degree of secrecy, but Neil McClelland, the UK Project Manager for Nanopool GmbH, describes the results as "stunning". "Items such as stents can be coated, and this will create anti sticking features - catheters , and sutures which are a source of infection, will also cease to be problematic."
Physorg has a few more details: "Food processing companies in Germany have already carried out trials of the spray, and found sterile surfaces that usually needed to be cleaned with strong bleach to keep them sterile needed only a hot water rinse if they were coated with liquid glass. The levels of sterility were higher for the glass-coated surfaces, and the surfaces remained sterile for months. [...] A year-long trial of the spray in a Lancashire hospital also produced "very promising" results for a range of applications including coatings for equipment, medical implants, catheters, sutures and bandages. The war graves association in the UK is investigating using the spray to treat stone monuments and grave stones, since trials have shown the coating protects against weathering and graffiti. Trials in Turkey are testing the product on monuments such as the Ataturk Mausoleum in Ankara. "
Promising, but Let's Wait and See
I'm still waiting for more tests (real-world and lab) before getting too excited. But if it works as promised, this could be a new super-material like graphene, with multiple applications in tons of different fields. And if it really makes things more durable and reduces or removes the need for strong chemicals to clean something, it could have a pretty significant positive environmental impact. But it could also have unforeseen effects, so let's not rush to put this everywhere.
Via Nanopool, Physorg
More Green Science & Technology
Making High-Tech Aircraft Parts with... Cork
Better Air Quality Means Fewer Ear Infections in Children
New Antireflective Coating Boosts Lifetime Energy Capture of Solar Cells
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Via TreeHugger
Friday, November 13. 2009
by Emily Singer
Joanna Aizenberg, a materials scientist at Harvard University, has scoured the natural world for clues to biological building codes. She aims to decipher some of Mother Nature’s unique designs, including dirt-resistant sea urchins and sea sponges made of super-strong light-conducting glass, to develop novel materials that, like these organisms, can self-assemble and sense and respond to their environment.
“We try to identify biological systems that have unusual and sophisticated properties, such as optical, structural, or magnetic properties, to make extremely sophisticated, efficient, and highly potent devices and materials,” says Aizenberg, who is also a core faculty member at the Wyss Institute for Biologically Inspired Engineering. “Then we take these principles and try to integrate them with what we already know in materials science--incorporating them into existing materials or fabricating a new generation of materials based on biological principles.” The work could result in better fiber optics, paint that changes color in response to temperature or light, and new ways of delivering drugs or clearing arterial plaques.
This collection of striking images explores some of Aizenberg’s new materials, as well as the organisms that inspired them.
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... Lire la suite et voir les images ICI.
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Via MIT Technology Review
Personal comment:
Les promesses de matériaux "hallucinants" grâce aux nanotechnologies, biotechnologies, etc. Pour autant qu'il n'y ait pas de "side effects".
Tuesday, November 10. 2009
Converting sunlight to electricity might no longer mean large panels of photovoltaic cells atop flat surfaces like roofs. Using zinc oxide nanostructures grown on optical fibers and coated with dye-sensitized solar cell materials, researchers at the Georgia Institute of Technology have developed a new type of three-dimensional photovoltaic system. The approach could allow PV systems to be hidden from view and located away from traditional locations such as rooftops.
“Using this technology, we can make photovoltaic generators that are foldable, concealed and mobile,” said Zhong Lin Wang, of the Georgia Tech School of Materials Science and Engineering. “Optical fiber could conduct sunlight into a building’s walls where the nanostructures would convert it to electricity. This is truly a three dimensional solar cell.”
Read More
Paper
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Via Nanoarchitecture
Personal comment:
This sounds really interesting: “Optical fiber could conduct sunlight into a building’s walls where the nanostructures would convert it to electricity. This is truly a three dimensional solar cell.”
Researchers at the University of Bristol, UK, have found that nanoparticles can damage the DNA of cells, even when the cells seem safe behind an impassable barrier of tissue. Their experiment used 30-nanometer-wide beads of cobalt-chromium nanoparticles, which are not currently being used in any treatments, experimental or otherwise. The tissue barrier was made of human cancer cells, about four cells deep, and the “target” cells on the other side of the barrier to the nanoparticles were human fibroblast cells, found in skin and connective tissue.
After a day in a lab dish, DNA damage was discovered in the fibroblasts. It wasn’t extensive, but included single and double-strand breaks in DNA, and abnormal chromosome doubling in some cells. Careful checking found no leaks in the barrier, and no cobalt-chromium beads on the wrong side of it, so the nanoparticles didn’t actually pass through the barrier to damage the DNA.
Instead, the nanoparticles were able to directly influence the nearest layer of barrier cells and disrupted their mitochondria – chambers where energy is generated and stored – which released signaling molecules (ATP), which in turn triggered a cascade of biochemical messages inside the cell. That signaling storm eventually reached the other side of the barrier cell, opening channels that spread the message to the next layer of barrier cells. The process continued until signaling molecules reached the fibroblasts, somehow damaging their DNA – the researchers don’t yet know how this happened.
Read More
Paper
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Via Nanoarchitecture
Tuesday, September 29. 2009
A novel nanoscale sensor needs no power source.
By Katherine Bourzac
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Stress sensor: This scanning-electron-microscope image shows a stress-triggered transistor in cross section. The zinc oxide nanowire, 25 nanometers in diameter, is embedded in a polymer (black area), leaving the top region free to bend.
Credit: ACS/Nano Letters |
Nanoscale sensors have many potential applications, from detecting disease molecules in blood to sensing sound within an artificial ear. But nanosensors typically have to be integrated with bulky power sources and integrated circuits. Now researchers at Georgia Tech have demonstrated a nanoscale sensor that doesn't need these other parts.
The new sensors consist of freestanding nanowires made of zinc oxide. When placed under stress, the nanowires generate an electrical potential, functioning as transistors.
Zhong Lin Wang, professor of materials science at Georgia Tech, has previously used piezoelectric nanowires to make nanogenerators that can harvest biomechanical energy, which he hopes will eventually be used to power portable electronics. Now Wang's group is taking advantage of the semiconducting properties of zinc oxide nanowires--the electrical potential generated when the new nanowires are bent, allowing them to act as transistors.
The Georgia Tech researchers used a vertical zinc oxide wire 25 nanometers in diameter to make a field-effect transistor. The nanowire is partially embedded in a substrate and connected at the root to gold electrodes that act as the source and the drain. When the wire is bent, the mechanical stress concentrates at the root, and charges build up. This creates an electrical potential that acts as a gate voltage, allowing electrical current to flow from source to drain, turning the device on. Wang's group has tested various triggers, including using a nanoscale probe to nudge the wire, and blowing gas over it.
Wang's group is "unique in using nanostructures to make something like this," says Liwei Lin, codirector of the University of California, Berkeley Sensor and Actuator Center. Nanowire sensors could be used for high-end sensing devices such as fingerprint scanners, Lin suggests.
Previous nanowire sensors have been tethered at both ends, limiting their range of motion. Wang says that the freestanding nanowires resemble the sensing hairs of the ear. If grouped into arrays of different lengths, each responsive to a different frequency of sound, the nanowires could potentially lead to battery-free hearing aids, he says.
The next step is to make arrays of the devices. "This is challenging because you have to make the electrical contact reliable, but we will be able to do that," says Wang.
Copyright Technology Review 2009.
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Via MIT Technology Review
Thursday, April 09. 2009
The device harnesses both sunlight and mechanical energy.
By Katherine Bourzac
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Nano hybrid: A dye-sensitized solar cell (top) and a nanogenerator (bottom) sit on the same substrate in the new device.
Credit: Xudong Wang |
Nanoscale generators can turn ambient mechanical energy--vibrations, fluid flow, and even biological movement--into a power source. Now researchers have combined a nanogenerator with a solar cell to create an integrated mechanical- and solar-energy-harvesting device. This hybrid generator is the first of its kind and might be used, for instance, to power airplane sensors by capturing sunlight as well as engine vibrations.
Nanogenerators typically use piezoelectric nanowires--hairlike zinc oxide structures that generate an electrical potential when mechanically stressed--to produce small amounts of power. The first such devices were made by Zhong Lin Wang, a professor at Georgia Tech and director of the institute's Center for Nanostructure Characterization. Wang hopes that nanogenerators will one day eliminate the need for batteries in implantable medical sensors, and will eventually generate enough power to charge up larger personal electronics.
Compared with solar cells, nanogenerators are still a relatively inefficient way of harvesting energy, says Wang, but "sometimes solar energy isn't available." So he collaborated with Xudong Wang, an assistant professor of materials science and engineering at the University of Wisconsin-Madison, to make the new hybrid device.
It combines two previously developed technologies in a layered silicon substrate, both of which rely on zinc oxide nanowires. The top layer consists of a thin-film solar cell embedded with dye-coated zinc oxide nanowires. The large surface area of the nanowires boosts the device's light absorption, a design based on work by Peidong Yang, a professor of chemistry at the University of California, Berkeley. The bottom layer contains Wang's nanogenerator. On the underside of the silicon is a jagged array of polymer-coated zinc oxide nanowires in a toothlike arrangement. When the device is exposed to vibrations, these "teeth" scrape against an underlying array of vertically aligned zinc oxide nanowires, creating an electrical potential.
The solar cell and the nanogenerator are electrically connected by the silicon substrate itself, which acts as both the anode of the solar cell and the cathode of the nanogenerator. It is possible to string together large groups of solar cells and nanogenerators, but having them integrated in a single system takes up less space and is therefore energy efficient. The prototype device can generate 0.6 volts of solar power and 10 millivolts of piezoelectric power. While the prototype device had only one nanogenerator, Wang expects to increase the power output by creating devices with multiple layers of nanogenerators. He says that a likely first application of these devices might be in sensor-laden military aircraft. The U.S. Air Force recently issued a call for research funding proposals related to hybrid energy-scavenging devices.
Charles Lieber, a professor of chemistry at Harvard University, says that Wang's device is "creative" and is, to his knowledge, the first hybrid nanoscale device capable of harvesting two types of energy. "That is particularly important, given that one is light active, while the other can work in the dark," says Lieber. He expects Wang's work to inspire other researchers to focus on hybrid nanogenerator devices, as well as on devices that combine nanogenerators with "complementary nano-enabled power storage."
Copyright Technology Review 2009.
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Via MIT Technology Review
Thursday, November 13. 2008
Alex Zettl's tiny radios, built from nanotubes, could improve everything from cell phones to medical diagnostics By Robert F. Service
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Tiny tunes: A nanoradio is a carbon nanotube anchored to an electrode, with a second electrode just beyond its free end.
Credit: John Hersey |
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If you own a sleek iPod Nano, you've got nothing on Alex Zettl. The physicist at the University of California, Berkeley, and his colleagues have come up with a nanoscale radio, in which the key circuitry consists of a single carbon nanotube.
Any wireless device, from cell phones to environmental sensors, could benefit from nanoradios. Smaller electronic components, such as tuners, would reduce power consumption and extend battery life. Nanoradios could also steer wireless communications into entirely new realms, including tiny devices that navigate the bloodstream to release drugs on command.
Miniaturizing radios has been a goal ever since RCA began marketing its pocket-sized transistor radios in 1955. More recently, electronics manufacturers have made microscale radios, creating new products such as radio frequency identification (RFID) tags. About five years ago, Zettl's group decided to try to make radios even smaller, working at the molecular scale as part of an effort to create cheap wireless environmental sensors.
Zettl's team set out to miniaturize individual components of a radio receiver, such as the antenna and the tuner, which selects one frequency to convert into a stream of electrical pulses that get sent to a speaker. But integrating separate nanoscale components proved difficult. About a year ago, however, Zettl and his students had a eureka moment. "We realized that, by golly, one nanotube can do it all," Zettl says. "Within a matter of days, we had a functioning radio." The first two transmissions it received were "Layla" by Derek and the Dominos and "Good Vibrations" by the Beach Boys.
The Beach Boys song was an apt choice. Zettl's nano receiver works by translating the electromagnetic oscillations of a radio wave into the mechanical vibrations of a nanotube, which are in turn converted into a stream of electrical pulses that reproduce the original radio signal. Zettl's team anchored a nanotube to a metal electrode, which is wired to a battery. Just beyond the nanotube's free end is a second metal electrode. When a voltage is applied between the electrodes, electrons flow from the battery through the first electrode and the nanotube and then jump from the nanotube's tip across the tiny gap to the second electrode. The nanotube--now negatively charged--is able to "feel" the oscillations of a passing radio wave, which (like all electromagnetic waves) has both an electrical and a magnetic component.
Those oscillations successively attract and repel the tip of the tube, making the tube vibrate in sync with the radio wave. As the tube is vibrating, electrons continue to spray out of its tip. When the tip is farther from the second electrode, as when the tube bends to one side, fewer electrons make the jump across the gap. The fluctuating electrical signal that results reproduces the audio information encoded onto the radio wave, and it can be sent to a speaker.
The next step for Zettl and his colleagues is to make their nanoradios send out information in addition to receiving it. But Zettl says that won't be hard, since a transmitter is essentially a receiver run in reverse.
Nano transmitters could open the door to other applications as well. For instance, Zettl suggests that nanoradios attached to tiny chemical sensors could be implanted in the blood vessels of patients with diabetes or other diseases. If the sensors detect an abnormal level of insulin or some other target compound, the transmitter could then relay the information to a detector, or perhaps even to an implanted drug reservoir that could release insulin or another therapeutic on cue. In fact, Zettl says that since his paper on the nanotube radio came out in the journal Nano Letters, he's received several calls from researchers working on radio-based drug delivery vehicles. "It's not just fantasy," he says. "It's active research going on right now."
Tiny Tunes
A nanoradio is a carbon nanotube anchored to an electrode, with a second electrode just beyond its free end. When a voltage is applied between the electrodes, electrons flow from a battery through the nanotube, jumping off its tip to the positive electrode. A radio wave alternately attracts and repels the nanotube tip, causing it to vibrate in sync. When the tip is farther from the electrode, fewer electrons bridge the gap; the varying electrical signal recovers the audio signal encoded by the radio wave.
Credit: John Hersey
See All 10 Emerging Technologies 2008
Copyright Technology Review 2008.
Personal comment:
Cela ressemble furieusement à la première pierre pour les objets communiquants et autres capteurs à l'intérieur du corps humain. En route vers la transparence complète...
Thursday, November 06. 2008
How to build a president from carbon nanotubes.
Wednesday, November 05, 2008
By Katherine Bourzac
John Hart, assistant professor of mechanical engineering at the University of Michigan, has created the president-elect's likeness using vertically grown carbon nanotubes and imaged them with a scanning-electron microscope. His gallery--and instructions on how to make your own "nanobama"--are at flickr and nanobama.com. Hart says that he made the nanobamas to promote interest in nanotechnology research.
Credit: John Hart
Personal comment:
Pour marquer le jour!
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