Illness-inducing bacteria, meet nano-engineered cotton–and a quick death. Researchers have created a new “filter” that zaps bacteria with electric fields to clean drinking water. They say their system may find use in developing countries since it requires only a small amount of voltage (a couple of car batteries, a stationary bike, or a solar panel could do the job) and cleans water an estimated 80,000 times faster than traditional devices.

Instead of trapping bacteria in small pores like many slow-going traditional filters, the cotton and silver nanowire combo uses small electric currents running through the nanowires to kill the bacteria outright. In a paper to appear in the journal Nano Letters researchers say that 20 volts and 2.5 inches worth of the material killed 98 percent of Escherichia coli in the water they tested in their lab setup.

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Sure, a laser can shine finely-tuned light to do anything from scanning your barcodes to correcting your vision, but soon that precise hero may meet its match: Physicists have recently imagined a device that can absorb light of certain frequencies, an “anti-laser.”

Absorbing light may not seem all that impressive, since after all, anything that appears black works as an absorber. Your driveway, however, is not the anti-laser. A paper in the Physical Review Letters lays out the plans for this device which can absorb light wave clones (same frequency, phase, and polarization) that some lasers emit. The pickiness of this theoretical light absorber is part of what would make the device unique, just as an important part of what separates a laser from a flashlight is the precision of the light a laser emits.

Instead of amplifying light into coherent pulses, as a laser does, an antilaser absorbs light beams zapped into it. It can be “tuned” to work at specific wavelengths of light, allowing researchers to turn a dial and cause the device to start and then stop absorbing light. “By just tinkering with the phases of the beams, magically it turns ‘black’ in this narrow wavelength range,” says team member A. Douglas Stone, a physicist at Yale University. “It’s an amazing trick.” [Science News]

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Perhaps it’s a fitting tribute. The Japanese–designers of some of the world’s most ingenious robots–can now watch a traditional art form get a robotic makeover. As described in a paper published this week in Proceedings of the National Academy of Sciences, MIT and Harvard researchers have made self-folding origami that can mold itself into a boat or an airplane.

Why? Origami is just a first step; researchers picture the “shape-shifting” robots used for everything from “smart” cups that could change from grande to venti based on how much coffee you need to a “Swiss army knife” that will bend to its user’s will, forming a variety of tools.

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A new type of solar cell using “quantum dots” may double the theoretical efficiency of current solar cells–allowing a panel to convert around 60 percent of the sun’s energy that it laps up into electricity. The research on these new cells appeared Friday in Science.

Current silicon-based solar cells lose about 80 percent of the sun’s energy they take in. It’s an inherent flaw: even working at their theoretical ideal, these cells would still lose 70 percent.

We can blame the sun’s diversely energized photons for this inefficiency. Silicon cells can only purposefully harvest photons with just the right amount energy. When they strike the cell, photons with just enough juice will prod an electron into motion (and create an electric current). An overly energized photon will excite the electrons to no purpose; the electrons will just quickly give off that photon’s energy as heat.

In two steps, this project, funded in part by the Department of Energy, salvages these “hot electrons.”

“There are a few steps needed to create what I call this ‘ultimate solar cell,’” says [Xiaoyang] Zhu, professor of chemistry and director of the Center for Materials Chemistry. “First, the cooling rate of hot electrons needs to be slowed down. Second, we need to be able to grab those hot electrons and use them quickly before they lose all of their energy.” [University of Texas at Austin]

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Michael Gratzel has come clean and revealed that he stole his award-winning design for a new kind of solar cell–stole it from a leaf, that is. The Swiss inventor and first prize-winner of the $960,000 Millennium Technology Prize believes he has a cheap way to power everything from cell phones to street lamps, copying plants’ power to harness sunlight and turn it into energy.

“I was always intrigued with natural photosynthesis,” Gratzel says in a Millennium Technology Prize video (see below), “the way the plant uses molecules to generate charges.”

His  solar cells aren’t as efficient as the current silicon photovoltaic panels, but they do use cheaper manufacturing materials.

“Gratzel’s innovation is likely to have an important role in low-cost, large-scale solutions for renewable energy,” Ainomaija Haarla, president of Finland’s Technology Academy, says in a prepared news release on the group’s website. [CNN]

Gratzel can also make his solar cells transparent or flexible. This means that designers might integrate them into existing structures, for example windows or even furniture.

“You can imagine using those cells as electricity producing windows…. What’s very exciting is that you collect light from all sides, so can capture electricity from the inside as well as the outside…. You could think that the glass of all high-rises in New York would be electricity generating panels,” he said. [BBC]

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Cigarettes aren’t done causing damage when you put them out. Whether the tally of discarded butts worldwide is 4.5 trillion or 5.6 trillion, it represents an enormous amount of nicotine and heavy metals deposited in the environment. But what if the contents of your ashtray had a useful application? According to Chinese researchers, they might.

Seeking a use for all that junk, the scientists tested the chemicals in cigarette butts for their effects on a kind of steel used in oil and gas pipelines.

The results were pretty dramatic. In a near-boiling solution of 10 and 15 percent hydrochloric acid (HCl; same stuff as stomach acid), the cigarette-derived cocktail reduce corrosion by between 90 and 94 percent [Discovery News].

The researchers document their technique in the study in Industrial & Engineering Chemistry Research. First, they had to soak cigarette butts they found on the side of the road in distilled water, with five butts to 100 milliliters (about 3.4 ounces) of water. That extract was then added to the HCL solution. If just five percent of the resulting solution consisted of that cigarette extract, those dramatic corrosion reductions began to appear.

If the researchers upped the strength of the acid, they needed to also increase the amount of added cigarette extract. For instance, with a 20 percent hydrochloric acid solution, the researchers needed to increase the butt leachate to 10 percent of the liquid to keep damage to the steel low: at less than 12 percent of the corrosion seen with the unamended acid solution [Science News].

Nine of the cigarette chemicals appeared to offer protective services for steel; interestingly, nicotine was the most important of the nine.

Don’t keep smoking for steel’s sake: The trillions of butts across the world represent more than enough for this use. But if you want to put your butts to good use, you can actually recycle them.

Related Content:
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80beats: Electronic Cigarettes Not a Safe Alternative to Conventional Cigs
80beats: In a Bad Economy, Recyclables Are Just Pieces of Junk
DISCOVER: Smoke Gets in Your Hair

Image: flickr / Nufkin

Doctors already use concentrated sound waves to see through solid tissue and take a look inside the body, as with ultrasound scans. But in this week’s Proceedings of the National Academy of Sciences, Caltech scientists say they’ve developed a metamaterial that focuses sound to such a high concentration that it could go on the offensive, targeting cancers or kidney stones while leaving the surrounding tissues alone. Oh, and one other thing: The military could use it to make weapons.

“The beauty of this system is that it’s just a bunch of ball bearings that we control with weights,” said Chiara Daraio [Discovery News], a member of the research team. Caltech’s acoustic lens relies on the same principle as Newton’s cradle—that toy your high school science teacher probably kept on his or her desk with metal balls on strings that demonstrated the conservation of energy. In this design, 21 parallel chains each contain 21 bearings. When the team strikes one end, it starts a compression wave that carries through the system. But instead of having the last ball swing out like a pendulum and bring the momentum back into the system, like the toy does, the acoustic lens focuses all the energy at the end of the system onto one spot, just a few inches away from the metamaterial.

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Scientists have created the world’s smallest superconductor, made out of just four molecule-pairs and less than a nanometer wide. That’s far smaller than the head of a pin — which stretches across a million nanometers — and more on the order of a DNA molecule, which is about 2 nanometers wide [PopSci]. The invention, described in the journal Nature Nanotechnology, provides the first evidence that nanoscale molecular superconducting wires can be fabricated, which could be used for nanoscale electronic devices and energy applications [Xinhua]. Superconductive materials allow electrical currents to pass through with zero resistance, making them potentially useful to a wide variety of industries.

Lead author Saw-Wai Hla, a physics professor at Ohio University’s Nanoscale and Quantum Phenomena Institute, explains that earlier it was almost impossible to make nanoscale interconnects using metallic conductors because the resistance increased as the size of wire becomes smaller. “The nanowires become so hot that they can melt and destruct. That issue, Joule heating, has been a major barrier for making nanoscale devices a reality” [Xinhua], Hla says.

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It’s become one of our favorite rituals: Researchers come out with a paper pushing the science of invisibility cloaks a little further, inspiring everyone to go giddy with visions of Harry Potter and Romulan Warbirds. This week’s study in Science is another small step, but it’s a crucial one. Scientists in Germany have created the first rudimentary “invisibility cloak” in 3D.

Invisibility cloak mania started in 2006, when a Duke University team created the technology to bend light waves around an object; since the tiny object neither absorbed nor reflected the experiment’s microwaves, it was essentially “cloaked.” (The researchers used microwaves instead of visible light because microwaves have longer wavelengths, and are therefore easier to control.) The invisibility excitement struck again two years later when researchers refined their technique to hide a nanoscale object from visible light waves.

Now, researchers have created a cloak that not only works in infrared light wavelengths that are close to humans’ visual range, but also in 3D, too. Previous devices have been able to hide objects from light travelling in only one direction; viewed from any other angle, the object would remain visible [BBC News].

The team from Karlsruhe Institute of Technology didn’t exactly make the Statue of Liberty disappear. The “bump” made invisible is a spot in a layer of gold that’s 0.00004 inches high by 0.00005 inches wide. That hasn’t dampened lead researcher Tolga Ergin’s excitement, though. “In principle, the cloak design is completely scalable; there is no limit to it,” Ergin said. Developing the fabrication technology so that the crystals were smaller could “lead to much larger cloaks” [The Independent].

The sci-fi kind of cloaking will be harder to achieve, since visible wavelengths of light are shorter than infrared and thus harder to control. But Ergin’s 3D cloak is another step toward humanity’s ultimate dream: not being bothered by other humans.

Related Content:
DISCOVER: How to Build an Invisibility Cloak
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80beats: New Version of Invisibility Moves Closer to Visual Cloaking
80beats: Light-Bending Scientists Take a Step Closer to Invisibility

Image: Science/AAAS

Carbon nanotubes have shown the potential to help us take better x-ray images, make cheaper hydrogen fuel cells, and replace silicon in computer chips. Add another possibility onto the pile: MIT researchers report this week in Nature Materials that they’ve used carbon nanotubes to create thermopower waves, a system they say could put out 100 times more energy than a lithium-ion battery.

Michael Strano’s team coated the tubes, which are only billionths of a meter across, with a fuel. This fuel was then ignited at one end of the nanotube using either a laser beam or a high-voltage spark, and the result was a fast-moving thermal wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse [Environmental News Service]. That wave travels 10,000 times the typical speed of this chemical reaction, and the heat blasts electrons down the tubes. Voila, electric current.

This previously unknown phenomenon opens up an entirely new area of energy research, Strano says, and the technology’s potential applications are exciting. Strano envisions thermopower waves that could enable ultra-small electronic devices, no larger than a grain of rice, perhaps a sensor or treatment device that could be injected into the body. Or they might be used in “environmental sensors that could be scattered like dust in the air,” he says [Environmental News Service].

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It’s not easy to find a material that’s both stretchy and hard. Neither is it to find a glue that will stick underwater. But this week researchers said that the solutions aquatic animals have created for those problems could inspire new materials in the lab.

Mussles have solved the hard-but-still-stretchy problem with their “beards.” The beards are actually made of 50 to 100 so-called byssal threads, and they are what anchor a mussel to a rock or other stable structure. According to study author Matthew Harrington, “they’re not only facing these huge wave forces which are trying to, you know, rip them off the rocks, but also they’re being blasted with debris like small pieces of sand and other debris in the water that are basically acting like sandblasting” [NPR]. If the mussels are blasted off the rocks, they’d likely be eaten or killed.

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For everyone out there who’d like to hear a little less of their amorous neighbors, not to mention their kid badly playing the violin, there may be hope: Hong Kong scientists have devised a delightfully simple material made of latex and plastic that they say could one day reduce the racket at noisy places like airports. The paper appears in Applied Physics Letters.

Zhiyu Yang and colleagues devised a system of thin tiles that, when assembled into a large sheet, could cancel out noise in a huge range, including the bass frequencies that tend to breach the walls of our apartments and houses with ease. Each panel is just three millimeters thick, and less than half an inch wide, with the weighted plastic button in the middle. When sound waves hit the panel, the membrane and weighted buttons resonate at difference frequencies. “The inner part of the membrane vibrates in opposite phase to the outer region,” says Yang. That means the sound waves cancel each other out and no sound gets through [New Scientist]. (more…)

You’ve probably heard about the extraordinary strength of many kinds of spider silk, but researchers in China say they’ve figured out another fascinating property of the silk—how it catches water in the air—and created their own copycat material.

For a study in Nature, Chinese scientists looked at the small, non-poisonous cribellate spider’s silk. The secret, revealed by scanning electron microscope, lies in the silk’s tail-shaped protein fibres which change structure in response to water. Once in contact with humidity, tiny sections of the thread scrunge up into knots, whose randomly arranged nano-fibres provide a roughly, knobbly texture [AFP]. In between these knots are smooth areas where the fibers are neatly aligned, allowing water to slide along until it hits a knot, where dewdrops accumulate.

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The next generation of bulletproof vests and military armor could well be inspired by a deep-sea snail, say scientists.

A team led by materials scientist Christine Ortiz of the Massachusetts Institute of Technology investigated the iron-rich shell of the “scaly foot” mollusk, whose triple-layered shell gives it one of the strongest exoskeletons seen in nature. The researchers believe that copying its microstructure could help in the development of armor for soldiers, tanks, and helicopters. Their work was published (pdf) this week in the Proceedings of the National Academy of Sciences.

Scientists were first drawn to this snail in 2003 when they discovered it living in a relatively harsh environment on the floor of the Indian Ocean. It lives near hydrothermal vents that spew hot water–thereby exposing it to fluctuations in temperature as well as high acidity. It also faces attacks from predators like crabs and other snail species. But unlike other snail species, this snail survives because of its thick shell and the different properties of each of its three layers.

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Stanford University researchers think they’ve stumbled upon a way to transform ordinary sheets of office paper into batteries and superconductors. By painting a carbon nanotube ink, which can collect electric charge, on plain copier paper, and then dipping the coated paper into a lithium ion solution and an electrolyte, they can create a current and store it within the paper battery.

The scientists had previously experimented with making batteries using a similar process of painting nanomaterial ink onto a thin layer of plastic. But in an unexpected twist, they found that pores in paper fibers make it hold the ink better than plastic, for a more durable battery [The New York Times]. The research team, led by Yi Cui, found that you can even crumple up the paper batteries or soak them in acid, and they’ll still work just fine. They hope their technology, which was reported in the journal Proceedings of the National Academy of Sciences, can usher in a new era of lightweight, low-cost batteries.

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