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Nanopores in a plastic membrane will make it the first material to block visible light and let our body heat pass through.

Nanomaterial Offers First Fabric That Can Keep Us Cool

The use of nanomaterials in textiles is one of the earliest commercial applications of nanotechnology. Nanomaterials have given us stain-resistant fabrics and enabled a range of wearable electronics. But they’ve yet to solve what has been the most vexing problem in clothing: keeping us cool in hot weather.

Now researchers at Stanford University have taken a nanomaterial called nanoporous polyethylene, or nanoPE (which has been mass produced for use in batteries), and tested it to see how it would tackle the challenge of creating a fabric that can keep us cool.  The results reveal that it may be far more effective at keeping us cool than any other synthetic or natural fabrics.

The reason that clothing has heretofore failed to offer any relief from the heat is because our bodies give off heat in the form of mid-infrared radiation (IR), and our garments block that wavelength from escaping. While this makes clothing a clear benefit when it’s cold, in warm weather it’s a distinct disadvantage.

In research described in the journal Science, the researchers found that the interconnected pores of the nanoPE material allowed 96 percent of the infrared heat to pass through it; cotton allowed only 1.6 percent of the IR to escape.

The Stanford researchers—led by Yi Cui, who has compiled an extensive body of work in getting nanomaterials to improve the performance of batteries—claim that this ability to let IR to pass through would make the person wearing the material feel four degrees Fahrenheit cooler than if they were wearing cotton.

The nanoPE material is able to achieve this release of the IR heat because of the size of the interconnected pores. The pores can range in size from 50 to 1000 nanometers. They’re therefore comparable in size to wavelengths of visible light, which allows the material to scatter that light. However, because the pores are much smaller than the wavelength of infrared light, the nanoPE is transparent to the IR.

It is this combination of blocking visible light and allowing IR to pass through that distinguishes the nanoPE material from regular polyethylene, which allows similar amounts of IR to pass through, but can only block 20 percent of the visible light compared to nanoPE’s 99 percent opacity.

The Stanford researchers were also able to improve on the water wicking capability of the nanoPE material by using a microneedle punching technique and coating the material with a water-repelling agent. The result is that perspiration can evaporate through the material unlike with regular polyethylene.

In the video below, you can see an illustration of how the nanoPE allows both moisture and IR heat to escape through the material.

This material would seem to be a boon for us as global temperatures continue to rise. But it may also help prevent those temperatures from continuing to rise because it will make it possible to work in office buildings without as much energy being used for air conditioning.

“If you can cool the person rather than the building where they work or live, that will save energy,” said Cui in a press release.

Though the nanoPE would—by offering at least an indirect way for securing big energy savings—be one of the biggest advances in clothing since we first started wrapping ourselves in animal hides and furs, it might be good to see if anyone would want to wear the material.

The experiments with the material were conducted on a device that mimics the heat output of human skin, which sounds conspicuously non-human. Anyone that has examined the use of nanomaterials in the textile industry will tell you that the issue raised by textile manufacturers about any new material is the “hand of a fabric”—in other words, how does it feel to our touch.

In continuing research, the Stanford team will be giving the material improved textures and cloth-like characteristics. If they can overcome that hurdle, the next will be producing the material cheaply in mass production.

Nanostructures on a crystal after ion bombardment: Trenches with nanohillocks on either side are created.

Meteorites Offer Insight Into Ion Bombardment on Nanoscale

It turns out if you want to know what happens to semiconductors under ion bombardment, you might do well to look at the effects of meteorites when they impact Earth. At least that’s what a team of researchers at Technische Universität Wien (Technical University of Vienna, TU Wien) discovered when they peered into the crystal surface of a semiconductor with an atomic force microscope (AFM).

In experiments described in the Journal of Physics: Condensed Matter, the researchers bombarded the surface of calcium fluoride with both xenon and lead ions. The AFM revealed the tracks left behind by ions hitting the calcium fluoride surface. Each ion strike creates an initial impact site and a trench several hundred nanometers long that is bordered by a series of nanohillocks on both sides. At the end of trench is a large single hillock created as the ion penetrates into deeper layers of the crystal.

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Surface plasmons allow superfast optical on-chip communications

Nanoscale Wireless Communication Operates at Visible Wavelengths for the First Time

Currently, wireless optical communication on computer chips occurs at near-infrared wavelengths. But if visible light could be used in these on-chip optical communications, the chips could be miniaturized significantly because the wavelengths in that portion of the spectrum are much smaller.

Now researchers at Boston College have developed a nanoscale wireless communication system that does just that. The key to the technology, as described in the journal Nature Scientific Reports, are antennas that can collect photons and reversibly convert them into surface plasmons with a high degree of control.

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Carbon nanotubes wrapped in a polymer offer a powerful sensing platform for many chemicals.

Carbon Nanotube-Based Sensor Detects Toxins With a Mobile Phone

A little over four years ago, researchers at the University of California, Riverside, developed a sensor made from carbon nantoubes for detecting toxic chemicals. So enthusiastic were the researchers with the prospects of their technology that they launched a company, Nano Engineered Applications, that intends to add this sensor to people’s mobile phones.

While the commercial prospects of a smartphone toxin detector are still uncertain, another team of researchers has recently demonstrated a sensing device that also relies on carbon nanotubes (CNTs) to detect different chemicals. Researchers from Japan’s International Center for Materials Nanoarchitectonics and the National Institute for Materials Science, working with collaborators from MIT, combined CNTs with a polymer and discovered that this resulting material offers a powerful sensing platform for toxic chemicals. Their results look to be the first viable demonstration of the power of sensors known as chemresistors.

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Florian Libisch, explaining the structure of graphene

Graphene Doubles Up on Quantum Dots' Promise in Quantum Computing

Quantum dots made from semiconductor materials, like silicon, are beginning to transform the display market. While it is their optoelectronic properties that are being leveraged in displays, the peculiar property of quantum dots that allows their electrons to be forced into discrete quantum states has long held out the promise of enabling quantum computing.

As it turns out, if you really want to exploit quantum dots for quantum computing, you’d have better luck setting aside the semiconductor variety and turning to a pure conductor, like graphene, to do the trick.

Researchers at Technische Universität Wien (TU Wein, or the Vienna University of Technology), along with colleagues from the University of Manchester in the United Kingdom and Rheinisch-Westfälische Technische Hochschule Aachen (RWTH Aachen University), in Germany, have managed to produce quantum dots out of graphene. And according to the multinational team, these dots offer a bold new promise for quantum computing.

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Optical image of the electrodes fabricated by nano-imprint lithography. Nanoscale electrodes (50nm width with separation of 50nm) fan out to microscale patterns and eventually to the contact pads.

Genetically Modified Bacteria Conduct Electricity, Ushering in New Era of Green Electronics

Researchers at the University of Massachusetts at Amherst have genetically modified common soil bacteria to produce nanowires capable of conducting electricity at a level that surprised even the scientists themselves. After years of skepticism that this was even theoretically possible, the practical demonstration could lead to a new generation of “green” electronics in which nanowires could be produced in plant waste, without the need for toxic chemicals.

The research, which was supported by the Office of Naval Research (ONR), goes back to a series of papers that Derek Lovley, a professor at UM Amherst, published back in 2011. Lovely overcame skeptics who claimed it was impossible for soil bacteria to conduct electricity. Brushing aside computer models indicating that it was impossible to make the bacteria into electrically conductive nanowires, Lovley demonstrated through experiments that it was indeed possible.

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New nanocrystal speeds up the modulation from blue laser light to red or green light for visible-light communication

Nanocrystals Enable a New Generation of Visible-Light Communication

Something called visible-light communication (VLC) is shaping up to be a viable alternative to Wi-Fi. Wi-Fi sends data between electronic devices through the use of radio bands, while VLC uses visible light emitted by light-emitting diodes (LEDs). In practical terms, this involves LED light fixtures turning on and off faster than our eyes can resolve, and in so doing, transmitting binary data. VLC technology has also been shown to have some attractive applications in automobiles.

The key to getting VLCs to work is the speed at which an LED can be switched on and off. But not all parts of an LED operate at the same speed. The LEDs used in such a VLC system typically produce a white light. When a white LED is combined with another diode that emits blue light, that blue light can be combined with phosphors to convert the blue light to red and green light. It is this conversion of turning blue light into red and green that is a stumbling block because it doesn’t occur as fast as the switching on and off of the light.

Now researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have developed a new nanocrystalline material that responds to switching 40 times as fast as the previous method of converting blue light to red and green light. This should enable transmission data rates of 2 gigabits per second. This is a marked improvement over today’s LED communications systems, which are capable of only 100 megabits per second, according to the researchers.

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A nanostructured molybdenum disulfide device can purify a water sample 50 times as fast as UV-only devices.

Nanostructured Device Purifies Water With Light

The combination of nanomaterials with water has produced some intriguing possibilities—among them, powering turbines by taking advantage of the production of steam from water that is near freezing, splitting a water molecule through artificial photosynthesis to produce hydrogen gas, dramatically improving water desalination processes, and purifying microbe-infested water simply and cheaply.

Now, researchers at the U.S. Department of Energy's SLAC National Accelerator Laboratory and Stanford University have added a new solution to water purification: a nanomaterial that can reportedly kill 99.999 percent of bacteria in water within just 20 minutes—a process that would otherwise take up to two days if only the ultraviolet (UV) light from the sun were used as a disinfectant. Why is UV treatment so slow? As the researchers explain, ultraviolet light accounts for roughly 4 percent of the total solar energy focused on the water being irradiated. Ratcheting up the amount of energy brought to bear was the aim of the experiments.

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Doped quantum dots

New Production Process Retains Photoluminescence of Quantum Dots

In the world of nanomaterials, carbon nanotubes and graphene have taken a large share of the attention. But in terms of real-world impact, it’s hard to ignore the role of quantum dots. For the past couple of years, these semiconductor crystals appear to have taken over the displays market.  However, quantum dots are vying for a major role in a number of other applications in which their photoluminescence is key, such as photovoltaics and medical applications.

But in order to get quantum dots to do the things we want them to do, they sometimes need to be doped with impurities in order to change their properties. This is where things get tricky: Quantum dots are so small that the dopants tend to wiggle back out of them. The good news: One of the more commonly used methods for introducing these other molecules to quantum dots—something called “click chemistry”—joins molecules together in a way that is fairly easy and results in easily removable byproducts. The bad news: The click chemistry technique that is the most appealing for quantum dots uses copper to catalyze the reaction. But the copper ions end up stripping the quantum dots of their photoluminescence.

Now researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, and the Faculty of Chemistry of the Warsaw University of Technology (FC WUT) have developed a method that keeps the click chemistry’s copper catalyst, but prevents it stripping the quantum dots of their photoluminescence. The key turns out to be improving the quality of the quantum dots.

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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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