Quantum Tunneling Composites Sniff Out Nasties
16 May 2012, 16:38
Categories: smt-energy-piezoelectric sensors
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A U.K. company, Peratech, says its highly pressure-sensitive material could be used to integrate a sensor that detects chemical compounds into paper or clothing.
The sensor rapidly detects volatile organic compounds. Many VOCs do not have an odor, but an electronic sensor could alert a user to the presence of harmful chemicals or perhaps indicate that something is off-kilter with a user’s health.
Peratech’s sensors use quantum tunneling composites (QTCs), which have previously been used to create pressure-sensitive touch screens. In quantum tunneling, electrons jump between conductors that are distributed through an otherwise nonconductive matrix. Deformation like twisting or bending brings the conductors close enough to one another that electrons can travel this way.
There are challenges that will need to be overcome, but two special features of Peratech’s sensor are that it can be printed in thin film and requires a low amount of power, which could be supplied by a small dedicated power source integrated into clothing.
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A Nanotechnology Cookbook
16 May 2012, 14:42
Categories: other
The peculiarities of materials at the nanoscale demand an interdisciplinary approach which can be difficult for students and researchers who are trained predominantly in a single field. A chemist might not have experience at working with cell cultures or a physicist may have no idea how to make the gold colloid they need for calibrating an atomic force microscope.
To help address this, Andrew Collins is the author of a new book, titled Nanotechnology Cookbook. Practical, Reliable and Jargon-free Experimental Procedures, which uses an interdisciplinary approach to help one quickly synthesize information from multiple perspectives. The cookbook is intended to be a handy reference to flick through, and from which you may select a preparation. The book, therefore, supports fundamental nanoscience experimentation via user-friendly access to knowledge; it features:
• 100+ detailed recipes for synthesis of basic nanostructured materials, enables readers to pick up the book and get started on a preparation immediately.
• High fidelity images show how preparations should look rather than vague schematics or verbal descriptions.
• Sequential and user-friendly by design, so the reader won’t get lost in overly detailed theory or miss out a step from ignorance.
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Bright White Light From Cadmium Selenide Quantum Dots
16 May 2012, 14:34
Categories: Quantum-Dots smt-luminescent-light-emit
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With the age of the incandescent light bulb fading rapidly, the holy grail of the lighting industry is to develop a highly efficient form of solid-state lighting that produces high quality white light. Compact fluorescent tubes and most white-light LEDs emit a combination of monochromatic colors that simulate white light.
One of the few alternative technologies that produce pure white light is white-light quantum dots. These are ultra-small fluorescent beads of cadmium selenide that can convert the blue light produced by an LED into a warm white light with a spectrum similar to that of incandescent light.
Seven years ago, when white-light quantum dots were discovered accidentally in a Vanderbilt chemistry lab, their efficiency was too low for commercial applications and several experts predicted that it would be impossible to raise it to practical levels. Today, however, Vanderbilt researchers have proven those predictions wrong by reporting that they have successfully boosted the fluorescent efficiency of these nanocrystals from an original level of three percent to as high as 45 percent.
“Forty-five percent is as high as the efficiency of some commercial phosphors which suggests that white-light quantum dots can now be used in some special lighting applications,” says Sandra Rosenthal. “The fact that we have successfully boosted their efficiency by more than 10 times also means that it should be possible to improve their efficiency even further.”
The general measure for the overall efficiency of lighting devices is called luminous efficiency and it measures the amount of visible light (lumens) a device produces per watt. An incandescent light bulb produces about 15 lumens/watt, while a fluorescent tubes put out about 100 lumens/watt. White light LEDs currently on the market range from 28 to 93 lumens/watt.
“We calculate that if you combine our enhanced quantum dots with the most efficient ultraviolet LED, the hybrid device would have a luminous efficiency of about 40 lumens/watt,” reported James McBride. “There is lots of room to improve the efficiency of UV LEDS and the improvements would translate directly into a higher efficiencies in the hybrid.”
Following a lead from some research done at the University of North Carolina, the researchers decided to see if treating the quantum dots with metal salts would have a brightening effect. They noticed that some of the salts seemed to produce a small – 10 to 20 percent – but noticeable improvement.
“They were acetate salts and they smelled a bit like acetic acid,” said McBride. “We knew that acetic acid binds to the quantum dots so we decided to give it a try.” The acetic acid treatment increased the quantum dots fluorescent efficiency from eight percent to 20 percent!
Acetic acid is a member of the carbocyclic acid family. So the researchers tried the other members in the family. They found that the simplest and most acidic member – formic acid, the chemical that ants use to mark their paths – worked the best, pushing the efficiency as high as 45 percent.
The brightness boost had an unexpected side effect. It shifted the peak of the color spectrum of the quantum dots slightly into the blue. This is ironic because the major complaint of white-light LEDs is that the light they produce has an unpleasant blue tint. However, the researchers maintain that they know how to correct the color-balance of the boosted light.
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Flexible Nanocomposite Generator
15 May 2012, 12:49
Categories: nanocomposites smt-energy-piezoelectric
Researchers at Georgia Tech and the Korea Advanced Institute of Science and Technology (KAIST) have developed a new form of low cost, large-area nanogenerator technology using the piezoelectric ceramic nanoparticles. Previous nanogenerator technologies have limitations such as complicated process, high-cost, and size-related restrictions.
The team developed a nanocomposite-based nanogenerator that successfully overcomes the critical restrictions existed in previous nanogenerators and builds a simple, low-cost, and large-scale self-powered energy system. The piezoelectric nanocomposite was produced by mixing piezoelectric nanoparticles with carbon-based nanomaterials (carbon nanotubes and reduced graphene oxide) in a polydimethylsiloxane (PDMS) matrix, and then fabricating the nanocomposite generator by the simple process of spin-casting or bar-coating method.
Professor Zhong Lin Wang from Georgia Institute of Technology, who is the inventor of the nanogenerator, said, “This exciting result first introduces a nanocomposite material into the self-powered energy system, and therefore it can expand the feasibility of nanogenerator in consumer electronics, ubiquitous sensor networks, and wearable clothes.”
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Graphene + Protein Fibrils = New Paper
15 May 2012, 12:22
Categories: bionanotech--nanobiotech nanocomposites
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ETH Zurich researchers, led by Raffaele Mezzenga, have created a new nanocomposite made of graphene and protein fibrils: a special paper, which combines the best features of both components. The nanocomposite paper is made of alternating layers of protein fibrils and graphene, after vacuum filtration drying.
The two components can be mixed in varying compositions, brought into solution, and dried into thin sheets through a vacuum filter, “similarly as one usually does in the manufacture of normal paper from cellulose,” says Mezzenga. “This combination of different materials with uncommon properties produces a novel nanocomposite with some major benefits.” For example, the material is entirely biodegradable.
Graphene is mechanically strong and electrically conductive, as well as, highly water repellent by nature. On the other hand, the protein fibrils are biologically active and can bind water. This allows the new material to absorb water and to change shape under varying humidity conditions. Furthermore, the “graphene paper” has shape memory features such that it can deform when adsorbing water, and recover the original shape upon drying. This could be used, for example, either in water sensors or humidity actuators.
The material can also be designed to meet other needs. For example, the higher the proportion of graphene, the better it conducts electricity. On the other hand, the more fibrils are present, the more water can be absorbed by this material, with enhanced deformations in response to humidity changes.
Interestingly, this new material can be made with relatively simple means. The protein, in this case, beta-lactoglobulin, a milk protein, is first denatured by high temperatures in an acidic solution. The end-products of this denaturation process are protein fibrils suspended in water; these fibrils then act as stabilizers for the hydrophobic graphene sheets and allow them to be finely dispersed in water and processed into nanocomposites by a simple filtration technology.
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Applied Nanotech Unveils Ultra-Strong Structural Adhesive
15 May 2012, 12:11
Categories: adhesives nanocomposites
Applied Nanotech Holdings, Inc. has unveiled a new product called CNTstix™, an ultra-strong carbon-nanotube reinforced adhesive for structural applications. With the global market for adhesives projected to reach $38 billion by the year 2017, Applied Nanotech’s two-part carbon nanotube reinforced epoxy adhesive performs much better than similar products on the market. Tested by a leading independent laboratory in North America, the adhesion tear strength of CNTstix™ is more 60% higher than that of a popular adhesive manufactured by a leading industry competitor.
“Our CNTstix™ adhesive outperforms conventional adhesives because of our patented carbon nanotube technology, which is also being used by Yonex Corporation for sporting goods,” said Dr. Dongsheng Mao. “Carbon nanotubes possess unique mechanical, electrical, and thermal properties. They are the strongest material known in the world to date.”
Using its proprietary functionalization and dispersion technologies, Applied Nanotech is able to significantly improve the properties of adhesives using carbon nanotubes, in particular for bonding materials to each other. The improvements realized with CNTstix™ have innumerable industrial and commercial applications such as packaging, sporting goods, automotive, electronics, footwear, construction repair and remodeling, textiles, consumer goods, and shipbuilding, etc.
“The potential market for CNTstix™ is very large,” said Dr. Zvi Yaniv. “After we sent samples to numerous potential customers from different industries, such as composite assemblies for automotive applications and carbon fiber tubing assembly for racing bicycles, responses have been very positive due to the performance and characteristics of this new adhesive for their applications.”
Building on its success in developing nanocomposites for Yonex Corporation (high performance golf club shafts and badminton racquets), Applied Nanotech has started to gain traction for its nanocomposite materials for additional commercial applications with very large market potential.
“In late 2011, we embarked on an aggressive direct sales program to increase our high-margin revenues. We are pleased to have CNTstix™ join our award-winning thermal management material CarbAl™ as the latest product to be sold direct to users,” said Doug Baker. “In addition, our growth plan will also result in other products coming on the market in 2012.”
Applied Nanotech is currently capable of providing CNTstix™ in a variety of quantities, starting at one ounce. Its special burst pouch packaging ensures a 100 percent accurate proper mixing of the CNT reinforced epoxy and compatible hardener.
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Virus-Based Piezoelectric Power Generation
15 May 2012, 11:34
Categories: bionanotech--nanobiotech smt-energy-piezoelectric
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Scientists at the University of California, Berkeley, have developed a way to generate electricity using viruses. The researchers built a generator with a postage stamp-sized electrode and based on a small film of specially engineered viruses. When a finger tapped the electrode, the viruses converted the mechanical energy into electricity.
“More research is needed, but our work is a promising first step toward the development of personal power generators, actuators for use in nano-devices, and other devices based on viral electronics,” said Dr Seung-Wuk Lee.
The virus used in the research was an M13 bacteriophage, which attacks bacteria but is benign to humans. For the demonstration, they took a multilayered film of viruses measuring 1 sq cm and sandwiched it between two gold-plated electrodes. These were connected by wires to a liquid-crystal display.
When pressure was applied to the generator, it was able to produce up to a quarter of the voltage of a common battery. This was enough current to flash the number “1” on the display.
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Designing Nanoarchitecture
15 May 2012, 11:22
Categories: scientists other
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In the video above, Lee Park, professor of chemistry at Williams College, presents Designing Nanoarchitecture. The talk was delivered on March 12, 2012, as part of the “Williams Thinking” lecture series.
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Energy Applications For Graphene
15 May 2012, 10:44
Categories: nanotubes-wires-fullerenes energy
Graphene-based materials are emerging as highly attractive materials for real applications, especially in the area of energy conversion and storage. There are four major energy-related areas where graphene will have an impact: solar cells, supercapacitors, lithium-ion batteries, and catalysis for fuel cells.
A recent review in Small gives a brief overview of the recent research concerning chemical and thermal approaches toward the production of well-defined graphene-based nanomaterials and their applications in energy-related areas. The review’s authors, led by Linjie Zhi, a professor in physical chemistry at the National Center for Nanoscience and Technology in Beijing, first discuss current research activities utilizing chemical approaches towards graphene-based nanomaterials. Then they specifically address graphene’s use in energy-related areas including solar cells, lithium ion batteries, supercapacitors, and catalysis
But before graphene-based nanomaterials and devices find widespread commercial use, two important problems have to be solved: one is the preparation of graphene-based nanomaterials with well-defined structures, and the other is the controllable fabrication of these materials into functional devices.
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Silver Nanoparticles For Mercury Clean-Up
14 May 2012, 13:38
Categories: nanoparticles filtration
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Researchers at the University of Brighton, UK, have used silver nanoparticles to decontaminate mercury-contaminated water. It has been hailed as a paradigm shift in scientists’ understanding of chemistry, since it is generally accepted that when silver is reduced at the nanoscale, it can only absorb a certain amount of mercury. However, Dr. Kseniia Katok was able to reduce the nanoparticles of silver to below 35 nanometers in diameter, and found that this allowed almost twice as much mercury to be absorbed.
The breakthrough opens the way for more effective, cheaper ways of cleaning mercury-contaminated water. Existing clean-up methods for mercury-polluted water either have either low mercury removal capabilities, leave a large chemical waste footprint or are not energy efficient. Professor Andy Cundy, the University’s Professor of Applied Geochemistry and Dr. Katok’s lead supervisor, said: “Dr. Katok’s findings enable a major shift towards the use of nanomaterials for waste water remediation and metal removal and recycling.”
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Nanoparticles Customize Colored Light
14 May 2012, 13:00
Categories: optics--photonics smt-chromism-color-change
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Engineers at Harvard have demonstrated a new kind of tunable color filter that uses optical nanoantennas to obtain precise control of color output. Whereas a conventional color filter can only produce one fixed color, a single active filter under exposure to different types of light can produce a range of colors.
The advance has the potential for application in televisions and biological imaging, and could even be used to create invisible security tags to mark currency. The findings appear in the February issue of Nano Letters.
The team engineered the size and shape of metal nanoparticles so that the color they appear strongly depends on the polarization of the light illuminating them. The nanoparticles can be regarded as antennas similar to those used for wireless communications but much smaller in scale and operating at visible frequencies.
“With the advances in nanotechnology, we can precisely control the shape of the optical nanoantennas, so we can tune them to react differently with light of different colors and different polarizations,” said co-author Tal Ellenbogen. “By doing so, we designed a new sort of controllable color filter.”
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Greener, Cleaner Plaster
14 May 2012, 12:43
Categories: self-assembly nanoparticles
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Gypsum is a naturally occurring mineral that is often used in industrial processes and, if left alone for thousands of years, can grow into huge translucent, towering and eerie, crystals more than 10 metres tall. Nevertheless, the formation of gypsum has until now been largely unexplored.
A new study by researchers from the University of Leeds, UK, and the CSIC-University of Granada, Spain, found that gypsum starts off as tiny crystals of a mineral called bassanite (commonly known as Plaster of Paris).
Currently, bassanite plaster is manufactured at a rate of 100 million tons per year by dehydrating quarried gypsum at 150 ºC. Builders, artists and medical specialists buy the bassanite powder and add water to create a malleable material that hardens once dried again.
By experimenting with supersaturated gypsum solutions, the researchers were able to produce bassanite at room temperature. This than transforms to gypsum.
“This process has never been documented before. In nature gypsum grows as these fantastic large crystals, yet we show that in the lab gypsum actually grows through the assembly of many, tiny bassanite crystals,” says Professor Liane G Benning from the University of Leeds. “These link together like a string of pearls before they crystallize to gypsum. We studied hundreds of high-resolution images and caught the tiny bassanite crystals in the act of assembling into gypsum.”
The lead author, Alexander van Driessche from the Laboratorio de Estudios Cristalográficos in Grenada, said: “Our study shows a new, low cost and low temperature way of making bassanite, although so far we have only managed to keep it stable for up to one hour.”
“If we manage to produce and stabilize bassanite crystals at room temperature through a clean, green method for long periods, we don’t just learn something about a natural process but, compared to what is industry standard currently, our research could also lead to a massive cost and energy saving for the production of plaster,” Benning said.
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Building Novel Nanomagnets
14 May 2012, 12:25
Categories: self-assembly molecular-machines--devices
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Researchers in Germany have succeeded in building new nanomagnets using a technique that involves a scanning tunnelling microscope whose tip can pick and place individual iron atoms. The magnets can be of different shapes and their properties can be directly measured and compared to elaborate computer simulations for the first time. Indeed, deviations from the simulations hint at novel, fundamental, atomic-scale magnetism effects, says the team.
“The assembly technique we used is very similar to the children’s game LEGO,” says Jens Wiebe of Hamburg University. “Our building blocks are iron atoms that are laid down on a very clean copper surface, and each block behaves like a small compass needle that can point in one of two directions – up or down. This allows us to assemble magnets whose constituent atoms can be arranged in a variety of different configurations.”
“In this way, we can build artificial magnets atom by atom that have a variety of different shapes – such as chains, triplets and ‘flowers’,” Wiebe said. “What is more, in the microscope we employed, the tip is coated with a magnetic material, which allows us to measure the magnetization curve of each of the constituent iron atoms within the magnet.”
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Knitting Carbon Fibers
13 May 2012, 16:28
Categories: nanofibers techniques
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Textile structures made from silicon carbide fibers are very interesting for the manufacture of fiber-reinforced, high temperature resistant, ceramic matrix composites (CMC). To produce such textile structures, one- or multi-step manufacturing processes like braiding, weaving, warp, or weft knitting are necessary. Depending on the fiber packing density and orientation the fabric structure, the stiffness, deformation, and fracture behavior of the fabric structure vary in a wide range.
In contrast to woven fabrics, which exhibit a low drapability and stretchability in different directions, warp-knitted fabrics are formed by creating loops which give rise for high flexibility and deformability. However, a high Young’s modulus and low deformability of the carbide fibers makes loop formation during knitting difficult. Bending of fibers is also affected by the friction which is caused by ribbing between fibers and the machine parts and by the friction between the fibers inside the roving.
Recently, scientists from the Friedrich-Alexander-University Erlangen-Nuremberg, Germany, demonstrated the manufacturing of knitted fabrics made of silicon carbide fiber. They derived the critical bending loads from fiber knot and loop testing in order to optimize yarn pretension, working speed, and take up speed during knitting processing. Subsequently, they tested and examined the mechanical behavior of the knit fabric under tensional load.
The investigations show that fiber fracture during knitting can be caused by torsion, bending, or tension. The German researchers considered fiber bending as the critical loading condition imposing boundary condition on the knitting process. Reduction of inter fiber friction surface sizing was found to be a critical step in order to produce a continuous knit structure.
The scientists modified the processing conditions for knitting and reduced buckling and friction acting on the silicon carbide fiber rovings. Using penetrating oil the points of largest friction between fibers and critical knitting elements were lubricated which decreased fiber fracture. Compared to woven silicon carbide fabric structures the knitted fiber perform offers a superior flexibility, wider range of pore size and a higher degree of drapability.
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Nanotube Electrodes Improve Solar Cells
13 May 2012, 16:20
Categories: nanotubes-wires-fullerenes smt-energy-photovoltaic
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Forests of carbon nanotubes are an efficient alternative for platinum electrodes in dye-sensitized solar cells (DSC), according to new research by collaborators at Rice University and Tsinghua University.
The single-wall nanotube arrays, grown in a process invented at Rice, are both much more electroactive and potentially cheaper than platinum, a common catalyst in DSCs, said Jun Lou, a materials scientist at Rice. In combination with newly developed sulfide electrolytes synthesized at Tsinghua, they could lead to more efficient and robust solar cells at a fraction of the current cost for traditional silicon-based solar cells.
“These are very versatile materials,” Lou said. “Single-walled carbon nanotubes have been around at Rice for a very long time, and people have found many different ways to use them. This is another way that turns out to be very well-matched to a sulfid-based electrolyte in DSC technology.”
Both Rice and Tsinghua built working solar cells, with similar results. They were able to achieve a power conversion efficiency of 5.25 percent – lower than the DSC record of 11 percent with iodine electrolytes a platinum electrode, but significantly higher a control that combined the new electrolyte with a traditional platinum counter electrode. Resistance between the new electrolyte and counter electrode is “the lowest we’ve ever seen,” Lou said.
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Nanoparticles Help Detect Radiation
13 May 2012, 16:10
Categories: sensors nanoparticles
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Researchers at the Georgia Tech Research Institute (GTRI) are developing ways to enhance the radiation-detection devices used at ports, border crossings, airports and elsewhere. The aim is to create technologies that will increase the effectiveness and reliability of detectors in the field, while also reducing cost.
“U.S. security personnel have to be on guard against two types of nuclear attack – true nuclear bombs, and devices that seek to harm people by dispersing radioactive material,” said Bernd Kahn, a researcher who is principal investigator on the project. “Both of these threats can be successfully detected by the right technology.”
The GTRI team, led by co-principal investigator Brent Wagner, is utilizing novel materials and nanotechnology techniques to produce improved radiation detection. The researchers have developed the Nano-photonic Composite Scintillation Detector, a prototype that combines rare-earth elements and other materials at the nanoscale for improved sensitivity, accuracy and robustness.
Scintillation detectors and solid-state detectors are two common types of radiation detectors, Wagner explained. A scintillation detector commonly employs a single crystal of sodium iodide or a similar material, while a solid-state detector is based on semiconducting materials such as germanium.
Both technologies are able to detect gamma rays and subatomic particles emitted by nuclear material. When gamma rays or particles strike a scintillation detector, they create light flashes that are converted to electrical pulses to help identify the radiation at hand. In a solid-state detector, incoming gamma rays or particles register directly as electrical pulses.
“Each reaction to a gamma ray takes a very short time – a fraction of a microsecond,” Wagner said. “By looking at the number and the intensity of the pulses, along with other factors, we can make informed judgments about the type of radioactive material we’re dealing with.”
But both approaches have drawbacks. A scintillation detector requires a large crystal grown from sodium iodide or other materials, and germanium-based solid-state detectors are difficult to make and germanium must be kept extremely cold.
To address these problems, the GTRI team has been investigating a wide variety of alternative materials and methodologies. After selecting the scintillation approach over solid-state, the researchers developed a composite material — composed of nanoparticles of rare-earth elements, halides and oxides — capable of creating light.
“A nanopowder can be much easier to make, because you don’t have to worry about producing a single large crystal that has zero imperfections,” Wagner said. Recently, the researchers have been investigating combining gadolinium and cerium bromide with silica and alumina.
“We’re optimistic that we’ve identified a productive methodology for creating a material that could be effective in the field,” Wagner said. “We’re continuing to work on issues involving purity, uniformity and scaling, with the aim of producing a material that can be successfully tested and deployed.”
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Touché Offers Interaction With Objects
13 May 2012, 15:54
Categories: sensors
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A doorknob that knows whether to lock or unlock based on how it is grasped, a smartphone that silences itself if the user holds a finger to her lips and a chair that adjusts room lighting based on recognizing if a user is reclining or leaning forward are among the many possible applications of Touché, a new sensing technique developed by a team at Disney Research, Pittsburgh, and Carnegie Mellon University.
Touché is a form of capacitive touch sensing, the same principle underlying the types of touchscreens used in most smartphones. But instead of sensing electrical signals at a single frequency, like the typical touchscreen, Touché monitors capacitive signals across a broad range of frequencies.
This Swept Frequency Capacitive Sensing (SFCS) makes it possible to not only detect a “touch event,” but to recognize complex configurations of the hand or body that is doing the touching. An object thus could sense how it is being touched, or might sense the body configuration of the person doing the touching.
SFCS is robust and can enhance everyday objects by using just a single sensing electrode. Sometimes, as in the case of a doorknob or other conductive objects, the object itself can serve as a sensor and no modifications are required. Even the human body or a body of water can be a sensor.
“Signal frequency sweeps have been used for decades in wireless communication, but as far as we know, nobody previously has attempted to apply this technique to touch interaction,” said Ivan Poupyrev, senior research scientist at Disney Research, Pittsburgh. “Yet, in our laboratory experiments, we were able to enhance a broad variety of objects with high-fidelity touch sensitivity. When combined with gesture recognition techniques, Touché demonstrated recognition rates approaching 100 percent. That suggests it could immediately be used to create new and exciting ways for people to interact with objects and the world at large.”
Both Touché and smartphone touchscreens are based on the phenomenon known as capacitive coupling. In a capacitive touchscreen, the surface is coated with a transparent conductor that carries an electrical signal. That signal is altered when a person’s finger touches it, providing an alternative path for the electrical charge. By monitoring the change in the signal, the device can determine if a touch occurs.
By monitoring a range of signal frequencies, however, Touché can derive much more information. Different body tissues have different capacitive properties, so monitoring a range of frequencies can detect a number of different paths that the electrical charge takes through the body.
Among the proof-of-concept applications the researchers have investigated is a smart doorknob. Depending on whether the knob was grasped, touched with one finger or two, or pinched, a door could be programmed to lock or unlock itself, admit a guest, or even leave a reply message, such as “I’ll be back in five minutes.”
In another proof-of-concept experiment, they showed that SFCS could enhance a traditional touchscreen by sensing not just the fingertip, but the configuration of the rest of the hand. They created the equivalent of a mouse “right click,” zoom in/out and copy/paste functions depending on whether the user pinched the phone’s screen and back with one finger or two, or used a thumb.
The researchers also were able to monitor body gestures, such as touching fingers, grasping hands and covering ears by having subjects wear electrodes similar to wristwatches on both arms. Such gestures could be used to control a smartphone or other device.
They also showed that a single electrode attached to any water vessel could detect a number of gestures, such as fingertip submerged, hand submerged and hand on bottom. Sensing touch in liquids might be particularly suited to toys, games and food appliances.
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Copper-Gold Nanoparticles Convert CO2
11 May 2012, 12:20
Categories: nanoparticles energy
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Various researchers around the world have studied copper’s potential as an energy-efficient means of recycling carbon dioxide emissions in powerplants: Instead of being released into the atmosphere, carbon dioxide would be circulated through a copper catalyst and turned into methane — which could then power the rest of the plant. Such a self-energizing system could vastly reduce greenhouse gas emissions from coal-fired and natural-gas-powered plants.
But copper is temperamental: easily oxidized, as when an old penny turns green. As a result, the metal is unstable, which can significantly slow its reaction with carbon dioxide and produce unwanted byproducts such as carbon monoxide and formic acid. Now researchers at MIT have come up with a solution that may further reduce the energy needed for copper to convert carbon dioxide, while also making the metal much more stable.
The group has engineered tiny nanoparticles of copper mixed with gold, which is resistant to corrosion and oxidation. The researchers observed that just a touch of gold makes copper much more stable. In experiments, they coated electrodes with the hybrid nanoparticles and found that much less energy was needed for these engineered nanoparticles to react with carbon dioxide, compared to nanoparticles of pure copper.
“You normally have to put a lot of energy into converting carbon dioxide into something useful,” says Hamad-Schifferli, an associate professor of mechanical engineering and biological engineering. “We demonstrated hybrid copper-gold nanoparticles are much more stable, and have the potential to lower the energy you need for the reaction.”
The team chose to engineer particles at the nanoscale in order to “get more bang for their buck,” Hamad-Schifferli says: The smaller the particles, the larger the surface area available for interaction with carbon dioxide molecules. “You could have more sites for the CO2 to come and stick down and get turned into something else,” she says.
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Improved Batteries with Carbon Nanoparticles
11 May 2012, 12:12
Categories: energy nanoparticles
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From smartphones to e-bikes, the number of mobile electronic devices is steadily growing around the world. As a result, there is an increased need for batteries that are small and light, yet powerful. As the potential for the further improvement of lithium-ion batteries is nearly exhausted, experts are now turning to a new and promising power storage device: lithium-sulfur batteries. In an important step toward the further development of this type of battery, a team of international researchers from Ludwig Maximilians Universität in Munich and Waterloo University in Canada has developed porous carbon nanoparticles that utilize sulfur molecules to achieve the greatest possible efficiency.
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Graphene Supercapacitor Promising For Portable Electronics
11 May 2012, 12:04
Categories: energy nanotubes-wires-fullerenes
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Electrochemical capacitors (ECs), also known as supercapacitors or ultracapacitors, differ from regular capacitors that you would find in your TV or computer in that they store substantially higher amounts of charges. They have garnered attention as energy storage devices as they charge and discharge faster than batteries, yet they are still limited by low energy densities, only a fraction of the energy density of batteries.
An EC that combines the power performance of capacitors with the high energy density of batteries would represent a significant advance in energy storage technology. This requires new electrodes that not only maintain high conductivity but also provide higher and more accessible surface area than conventional ECs that use activated carbon electrodes.
Now researchers at UCLA have used a standard LightScribe DVD optical drive to produce such electrodes. The electrodes are composed of an expanded network of graphene — a one-atom-thick layer of graphitic carbon — that shows excellent mechanical and electrical properties as well as exceptionally high surface area. The process is based on coating a DVD disc with a film of graphite oxide that is then laser treated inside a LightScribe DVD drive to produce graphene electrodes.
Typically, the performance of energy storage devices is evaluated by two main figures, the energy density and power density. Suppose we are using the device to run an electric car — the energy density tells us how far the car can go a single charge whereas the power density tells us how fast the car can go. Here, devices made with Laser Scribed Graphene (LSG) electrodes exhibit ultrahigh energy density values in different electrolytes while maintaining the high power density and excellent cycle stability of ECs. Moreover, these ECs maintain excellent electrochemical attributes under high mechanical stress and thus hold promise for high power, flexible electronics.
“Our study demonstrates that our new graphene-based supercapacitors store as much charge as conventional batteries, but can be charged and discharged a hundred to a thousand times faster,” said Richard B. Kaner, professor of chemistry & materials science and engineering.
“Here, we present a strategy for the production of high-performance graphene-based ECs through a simple all solid-state approach that avoids the restacking of graphene sheets,” said Maher F. El-Kady, the lead author of the study and a graduate student in Kaner’s lab.
The research team replaced the liquid electrolyte with a polymer gelled electrolyte that also acts as a separator, further reducing the device thickness and weight and simplifying the fabrication process as it does not require special packaging materials.
In order to evaluate under real conditions the potential of this all solid-state LSG-EC for flexible storage, the research team placed a device under constant mechanical stress to analyze its performance. Interestingly enough, this had almost no effect on the performance of the device.
“We attribute the high performance and durability to the high mechanical flexibility of the electrodes along with the interpenetrating network structure between the LSG electrodes and the gelled electrolyte,” explains Kaner. “The electrolyte solidifies during the device assembly and acts like glue that holds the device components together.”
The method improves the mechanical integrity and increases the life cycle of the device even when tested under extreme conditions. Since this remarkable performance has yet to be realized in commercial devices, these LSG supercapacitors could lead the way to ideal energy storage systems for next generation flexible, portable electronics.
Posted by: The Editors
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