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Paper-based Origami Battery Operates on the Respiration of Microbes

The Japanese art of folding paper into objects, known as origami, has taken on new life in nanotechnology research. The latest incarnation of this ancient art comes to us via research out of Binghamton University in New York. The technique has been applied to a battery technology that uses bacteria as the power source.

In the journal Nano Energy, the Binghamton researchers demonstrate how they have captured the respiration of microbes to generate enough energy to power a paper-based biosensor. All the microbes that were needed could be provided in a single drop of liquid teeming with bacteria.

“Dirty water has a lot of organic matter,” said Seokheun “Sean” Choi, who led the research, in a press release. “Any type of organic material can be the source of bacteria for the bacterial metabolism.”

Origami’s role in the battery design comes into play with the folding of two-dimensional sheets to create a three-dimensional battery structure that is about the size of a matchbook. The air-breathing cathode was produced by spraying nickel onto one side of a typical piece of paper. The anode is screen printed with carbon paints. The bacteria-laced water was added into a folded battery stack. In operation, this stack is unfolded, exposing all the cathodes to the air, maximizing their cathodic reactions.

The point of developing this simple battery was to find a way to power a separate paper-based biosensor without depending on an external handheld device to run the analysis. Choi believes that the simple battery he and his colleagues have developed can produce the microwatts required to run a biosensor in a self-contained system.

This simple, self-contained device should prove particularly useful in remote locations where resources—especially money—are limited; the entire device would cost only five cents.

Having been awarded a US $300,000 three-year grant from the National Science Foundation to develop a commercially viable origami battery, Choi is confident that we could see such a device in the field in the not-too-distant future.

Choi added: “Paper is cheap and it’s biodegradable. And we don’t need external pumps or syringes [for a paper-based biosensor] because paper can suck up a solution using capillary force.”

Graphene Shines in World's Thinnest Light Bulb

Back in April, we covered news that graphene was going to make a commercial breakout of sorts as a coating in an LED light bulb to reduce its energy consumption and lengthen its lifetime.

Now researchers at Columbia University from James Hone’s lab,  in cooperation with a team at Korea Research Institute of Standards and Science (KRISS), have taken this huge step forward by creating the first on-chip incandescent visible light source using graphene as the filament.

“We've created what is essentially the world's thinnest light bulb,” says Hone, a professor at Columbia Engineering, in a press release. “This new type of 'broadband' light emitter can be integrated into chips and will pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.”

In work published in the journal Nature Nanotechnology, researchers suspended graphene above a silicon substrate by attaching it to two metal electrodes and then passed current through the graphene-based filament, causing it to heat up.

In the video below you can see an animated depiction of how the graphene filament operate.

The aim of creating integrated circuits that use photons rather than electrons, sometimes called integrated photonic circuits,  depends on being able to generate light on the chip itself. While a number of approaches have been developed for generating this light, this research marks the first time that anyone has done it with the simplest artificial light source: incandescent light.

The main reason that this was never achieved before is because of the amount of heat that incandescent light generates. In order for these micro-scale metal wires to glow in the visible light range, they must be able to withstand temperatures reaching thousands of degrees Celsius. Getting that level of heat to transfer out of the micro-scale wires was always a problem and often led to damaging the surrounding chip.

But graphene makes all the difference. The international team demonstrated heating the graphene-based filament to 2500 degree Celsius, so that it would glow brightly enough to be seen by the naked eye. The material’s success in this application depended on two of its properties: transparency and the fact that it acts as a poorer heat conductor the hotter it gets.

Graphene’s unusual heat conduction was key to keeping the light emitter from destroying the chip it was built on. The lack of conduction confines the heat within a small “hot spot” in the center of the graphene filament.

Graphene’s transparency was behind the discovery that emitted spectrum of light emitted had peaks at certain wavelengths. This, they found, occurred because of interference between the light emitted from the graphene filament and the light reflecting off the silicon substrate beneath it. So it becomes possible to tune the emission spectrum by altering the distance between the filament and the substrate.

Novel Nanomaterial Makes Carbon Dioxide Sensors Portable

Researchers at ETH Zurich, Switzerland and the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany have leveraged a new type of nanomaterial to fabricate a novel carbon dioxide (CO2) sensor that is much smaller in scale and requires less energy than previous devices.

A new operating principle allows the sensor to be both small and energy efficient. The researchers envision portable applications, such as scuba diving or high-altitude mountaineering.

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Quantum Dots Enable Next Generation of LED Lighting Systems

Quantum dots have gone big time. With Samsung’s first quantum dot televisions shipping last month, production is being ramped up and the decade-and-a-half of promise appears to be coming true.

Now researchers at the University of Hiroshima in Japan have used silicon-based quantum dots for a type of light-emitting diode (LED) that promises to revolutionize lighting systems. The Japanese researchers have fabricated a hybrid inorganic/organic LED that produces white-blue electroluminescence using quantum dots. This white-blue electroluminescence LED promises a next-generation of illumination for flexible lighting and displays.

In research published in the journal Applied Physics Letters, the researchers determined that their quantum dot–based LED could achieve its white-blue luminescence with an applied voltage of 6 volts and reach 78 percent of the effective emission obtained from silicon quantum dots.

To give you sense of how these numbers stack up, about six years ago, the luminescent efficiency of quantum dots used in state-of-the-art electroluminescent LEDs were reduced from more than 90 percent to about 15 percent because the dots had to be packed into an organic film that acted as a transport for the electrons.

The Japanese researchers also report that their LED produced current and optical power densities 280 and 350 times as high as those of previously reported devices. The high current and optical power densities of the quantum dot–based LEDs resulted from optimizing the layered structure in a way that better enabled carrier migration.

The actual physical dimensions of the LED provide an active area of 4 square mm, which is 40 times as large as that of a typical commercial LED. In addition, the thickness of the LED is 0.5 mm.

Perhaps the most appealing aspect of the research is that the new LEDs were entirely fabricated through solution-based processing carried out at room temperature and pressure.

The fabrication process involved taking a glass substrate and then depositing conductive polymer solutions and a colloidal silicon quantum dot solution on top of it.

Ken-ichi Saitow, professor at Hiroshima University and leader of the research added: "QD LED has attracted significant attention as a next-generation LED. Although several breakthroughs will be required for achieving implementation, a QD-based hybrid LED allows us to give so fruitful feature that we cannot imagine."

With $31.5 Million in New Funds, Nantero Keeps Up the Good Fight

The long and twisting road for Nantero in its efforts to bring a radically new memory device to market serves as a kind of lesson in perseverance and a microcosm of nanotechnology’s commercial development. The latest news for Nantero is that it has received $31.5 million to continue its now seemingly quixotic quest to bring its carbon nanotube-based non-volatile random access memory device (NRAM) to market.

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Graphene Coating Could Save Millions in Power Plant Energy Costs

Earlier this week, we covered a company, Xefro, that was applying graphene to a home heating system, producing energy savings over traditional systems.

Now research out of MIT is showing that coating power plant condensers with graphene could make them more energy efficient. 

In research published in the journal Nano Letters, the MIT team addressed one of the basic elements of steam-generated electricity: heat transfer in water condensation. In a steam-powered power plant, water is heated up to create steam that turns a turbine. The turning of the turbine produces electricity. In this process, the steam is condensed back into water and the whole process begins again.

The MIT team looked at these condensers and found that by layering their surfaces with graphene they can improve the rate of heat transfer by a factor of four.

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Graphene Heating System Dramatically Reduces Home Energy Costs

Breakthroughs in energy generation using nanomaterials—like their enabling of better supercapacitors or photovoltaics—often grab the headlines. But it is in the unheralded area of energy savings that nanomaterials are perhaps making the biggest inroads.

A startup in the UK called Xefro is bridging this divide between energy generation and energy savings through its development of a heating system that the company claims marks the first time that the “wonder material” graphene has been used as a heating element. Depending on the kind of heating system currently used in a home, the company estimates that this graphene-based heating system can reduce energy costs by anywhere from 25 to 70 percent.

Xefro uses graphene-based ink that can be printed on a variety of materials and into just about any configuration. The system takes advantage of graphene's minimal thermal mass so the heat can be turned on and off quickly, and leverages graphene’s large surface area so that energy isn’t wasted in heating up the heater itself.

“The innovation is all about getting useable heat where it is needed,” explained Tim Harper, a founder of Xefro and co-inventor of the graphene heating element, in an e-mail interview with IEEE Spectrum (full disclosure: I used to work for Harper at a nanotech consultancy called Cientifica Plc). “While it is true that electrical resistive heating is almost 100-percent efficient in converting electricity into heat, it is what happens to that generated heat that is critical.”

Traditional heating systems are very inefficient in that they require heat to be transferred to multiple materials: for example, heating up water to heat up a radiator which heats up air and then finally heats up objects in a room, according to Harper.

He added: “Our initial question was ‘How can we get the heat directly to where it needed?’ and that led us to evaluate a wide range of heating materials and systems before we finally arrived at graphene.”

To meet the company’s criteria that the material should be usable in a wide variety of shapes and sizes, Harper and his collaborators turned to graphene inks. “This is especially important for water heating, where we wrap the flexible graphene element around a hot water tank,” says Harper. “By varying the ink formulation, we can change the resistivity of the heating element and its thickness depending on the required application.”

Once Xefro made the decision to use graphene, it wanted to avoid the mistake made by the producers of other infrared heating products now available on the market: placing the heating element inside a metal box that reflects back most of the infrared energy, creating an electrical convection heater rather than a true radiant heater. 

“By selecting the right materials and understanding enough about the physics of heat transfer, we’ve been able to tune the heater to emit infrared in the part of the spectrum that gives the most efficient heating effect,” explained Harper. “Further, by selecting the right materials for the construction of the heater, we can reduce absorption of infrared to the minimum and ensure that most of the heat is emitted [out into the room] rather than simply heating up the wall behind the heater.”

While graphene does offer some attractive properties for reducing wasted energy, it is the combination of the graphene-based heating element with an electronic control system that provides the real cost savings.

“Because graphene gives us an instant on/off response, this allows a number of smart switching algorithms to be used,” says Harper. “The energy savings come when the heaters are deployed as a system throughout a building. The heaters are linked with the control system via Wi-Fi, allowing the system to learn your behavior as well as the optimum heating required to maintain a comfortable temperature.”

Harper says the systems will be available in July 2015 through Xefro’s distributors in the UK. It will also be expanding into other markets, with partners and distributors making them available later in the year.

Editor’s note: A disclosure statement was added on June 3, 2015.

NanoMRI Gets Real

Many of us are acquainted with magnetic resonance imaging (MRI), but you may not have heard of nanoMRI a technology that can image viruses and cells for in-depth analysis.

Up until now, nanoMRI has been a long and laborious process, in which a single scan can take up to two weeks to complete. Now researchers at the Swiss Federal Institute of Technology in Zurich (ETH Zurich) have dramatically reduced this scanning time to a couple of days by developing a system that can perform in parallel the measurements that used to have to be done sequentially—a process known as multiplexing.

"As a loose analogy, think of how your eyes register green, red, and blue information at the same time using different receptors—you're measuring different colors in parallel," Alexander Eichler, a postdoctoral researcher in the physics department at ETH Zurich said in a press release.

Fundamentally, MRI exploits the fact that particular atoms have nuclei that are like tiny magnets. When these atoms come under the influence of a magnetic field, they start to rotate around the axis of that magnetic field.

This rotation is called precession.  The precession generates its own frequency of electromagnetic radiation known as the Larmor frequency. The Larmor frequency depends on the type of atoms and the strength of the magnetic field. So an MRI determines the positions of the atoms based on frequencies of their precession.

This standard MRI process works pretty well until you get down to nanoscale objects like cells where the strength of around 1000 atoms is not robust enough to be detected.

"Clinical MRI is only possible because a single 3-D pixel—a ‘voxel’—contains about 1018 atoms," Eichler explained in the press release. "With nanoMRI, we want to detect voxels with only a thousand atoms or less, meaning that we need a sensitivity at least a quadrillion [1015, or a million billion] times better."

In the research published in the journal Applied Physics Letters, the ETH Zurich team developed their technique around a magnetic resonance force microscopy (MRFM) apparatus, which has been the standard piece of equipment for previous nanoMRI methods.

With the MRFM apparatus, the nuclei of the atoms are exposed to a small magnetic force that is transferred to a micro-scale cantilever. The force on the cantilever causes it to vibrate, and that vibration can then be measured in a way that forms an image.

This process used to have to be done one measurement at a time but the ETH researchers have developed a technique to do make these measurements in parallel across six data points. This parallel measurement, known as multiplexing, involves encoding different bits of information in the detector using different phases.

"The term 'phase' refers to a lag in a periodic signal,” said Eichler. “The phase can be used to differentiate between periodic signals in a way similar to how color is used to differentiate between light signals in the eye."

Eichler added: “With commercial applications in mind, this time gain is crucial because it makes a huge difference to a pharmaceutical company if a virus can be characterized within three days rather than a month."

Supercapacitors Take Huge Leap in Performance

The Economist has published an article this week highlighting the work of Lu Wu at the Gwangju Institute of Science and Technology in South Korea in which he and his colleagues have developed a process for producing graphene that could lead to better supercapacitors.

While The Economist article makes some pretty incredible claims, such as that the graphene-based supercapacitors produced by the Korean researchers can store more energy per kilogram than lithium-ion (Li-ion) batteries, the actual research paper in the Journal of Power Sciences offers a less-hyped but nonetheless impressive list of achievements from the research.

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Molecular Electronics Takes Large Stride Forward

Molecular electronics has long promised a day when individual molecules would serve as the basic building blocks for electronics.

That day has moved a bit closer thanks to research out of the Columbia University School of Engineering and Applied Science. Researchers there have developed a new technique that makes it possible to produce a diode from a single molecule.

In research published in the journal Nature Nanotechnology,  the researchers claim that they have not only produced a single-molecule diode, but that it greatly outperforms all previous designs.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
Contributor
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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