Engineers Solve a Biological Mystery and Boost Artificial Intelligence

By simulating 25,000 generations of evolution within computers, Cornell University engineering and robotics researchers have discovered why biological networks tend to be organized as modules -- a finding that will lead to a deeper understanding of the evolution of complexity.

Conceptual illustration of a computer chip functioning as a brain. (Credit: © Nikolai Sorokin / Fotolia)

The new insight also will help evolve artificial intelligence, so robot brains can acquire the grace and cunning of animals.

From brains to gene regulatory networks, many biological entities are organized into modules -- dense clusters of interconnected parts within a complex network. For decades biologists have wanted to know why humans, bacteria and other organisms evolved in a modular fashion. Like engineers, nature builds things modularly by building and combining distinct parts, but that does not explain how such modularity evolved in the first place. Renowned biologists Richard Dawkins, Günter P. Wagner, and the late Stephen Jay Gould identified the question of modularity as central to the debate over "the evolution of complexity."

For years, the prevailing assumption was simply that modules evolved because entities that were modular could respond to change more quickly, and therefore had an adaptive advantage over their non-modular competitors. But that may not be enough to explain the origin of the phenomena.

The team discovered that evolution produces modules not because they produce more adaptable designs, but because modular designs have fewer and shorter network connections, which are costly to build and maintain. As it turned out, it was enough to include a "cost of wiring" to make evolution favor modular architectures.

This theory is detailed in "The Evolutionary Origins of Modularity," published January 29 in the Proceedings of the Royal Society by Hod Lipson, Cornell associate professor of mechanical and aerospace engineering; Jean-Baptiste Mouret, a robotics and computer science professor at Université Pierre et Marie Curie in Paris; and by Jeff Clune, a former visiting scientist at Cornell and currently an assistant professor of computer science at the University of Wyoming.

To test the theory, the researchers simulated the evolution of networks with and without a cost for network connections.

"Once you add a cost for network connections, modules immediately appear. Without a cost, modules never form. The effect is quite dramatic," says Clune.

The results may help explain the near-universal presence of modularity in biological networks as diverse as neural networks -- such as animal brains -- and vascular networks, gene regulatory networks, protein-protein interaction networks, metabolic networks and even human-constructed networks such as the Internet.

"Being able to evolve modularity will let us create more complex, sophisticated computational brains," says Clune.

Says Lipson: "We've had various attempts to try to crack the modularity question in lots of different ways. This one by far is the simplest and most elegant."

The National Science Foundation and the French National Research Agency funded this research.

source:sciencedaily

New Genre of 'Intelligent' Micro And Nanomotors

 Enzymes, workhorse molecules of life that underpin almost every biological process, may have a new role as "intelligent" micro- and nanomotors with applications in medicine, engineering and other fields. That's the topic of a report in the Journal of the American Chemical Society, showing that single molecules of common enzymes can generate enough force to cause movement in specific directions.

Enzymes may work as “intelligent” micro- and nanomotors, like tiny car engines, with applications in medicine, engineering. (Credit: © Gudellaphoto / Fotolia)

Peter J. Butler, Ayusman Sen and colleagues point out that enzymes -- proteins that jump-start chemical reactions -- are the basis of natural biological motors essential to life. Scientists long have wondered whether a single enzyme molecule, the smallest machine that could possibly exist, might be able to generate enough force to cause its own movement in a specific direction. "Positive answers to these questions," they explain, "have important implications in areas ranging from biological transport to the design of 'intelligent,' enzyme-powered, autonomous nano- and micromotors, which are expected to find applications in bottom-up assembly of structures, pattern formation, cargo (drug) delivery at specific locations, roving sensors and related functions."

They provide the positive answers in experiments with two common enzymes called catalase and urease. Catalase protects the body from harmful effects of hydrogen peroxide formed naturally in the course of life. Urease, found in many plants, converts urea to ammonia and carbon dioxide. The researchers show that these two enzymes, in the presence of their respective substrate (hydrogen peroxide or urea, which acts as fuel), show movement. More significantly, the movement becomes directional through the imposition of a substrate gradient, a form of chemotaxis. Chemotaxis is what attracts living things toward sources of food. The researchers also show that movement causes chemically interconnected enzymes to be drawn together; a form of predator-prey behavior at the nanoscale.

The authors acknowledge funding from The Pennsylvania State University Materials Research Science and Engineering Center supported by the National Science Foundation.

source:sciencedaily

NANO-BREAKTHROUGH FOR AUTOMOTIVE FUEL CELLS ?

NANO-BREAKTHROUGH FOR AUTOMOTIVE FUEL CELLS ?

NANO-BREAKTHROUGH FOR AUTOMOTIVE FUEL CELLS ?

What if by some engineering miracle one part within a conventional internal combustion engine was changed that would multiply its power output by a factor of 5 without burning additional fuel? A 100 horsepower engine would suddenly put out 500. The world would change. Engines would be smaller, lighter and presumably somewhat less expensive.

Unfortunately this miracle hasn’t happened. But it MAY have for proton exchange membrane (PEM) fuel cells. (I emphasize the “may” because the breakthrough technology doesn’t appear to have been tested in a working, off-the-shelf, fuel cell.)

There’s one part within a fuel cell that literally makes it all come together. Appropriately named it’s the catalyst. The catalyst creates the opportunity for hydrogen to combine with oxygen to make water, and while doing so momentarily allows electrons to be borrowed as flowing electric current to do real work, like turning an electric motor to drive a car to the supermarket.

Catalysts are typically made of pricey platinum (but not very much of it) adding to the cost of fuel cells and encumbering their mass adoption into vehicles and other portable uses.

Hitachi Maxell, of Tokyo, thinks it has a new catalyst solution that would be a true breakthrough if it works in the real fuel cell world. The catalyst not only uses less platinum but dramatically increases electric current producing reactions by almost that factor of five eluded to above: It encourages 4.8 times the hydrogen-oxygen combinations than a typical commercial platinum catalyst of the same unit area. The more hydrogen and oxygen combinations a catalyst can encourage the more electrons will be available for use as flowing electricity.

for more visit http://nanoscience2day.blogspot.in/

Scientists Create Artificial Mini 'Black Hole'

Chinese researchers have successfully built an electromagnetic absorbing device for microwave frequencies. The device, made of a thin cylinder comprising 60 concentric rings of metamaterials, is capable of absorbing microwave radiation, and has been compared to an astrophysical black hole (which, in space, soaks up matter and light).

Omnidirectional electromagnetic absorber. (Credit: Image courtesy of Institute of Physics)

The research published June 3 inNew Journal of Physics, shows how the researchers utilised the special properties of metamaterials, a class of ordered composites which can distort light and other waves.

Qiang Cheng and Tie Jun Cui of the State Key Laboratory of Millimeter Waves at Southeast University in Nanjing, China, designed and fabricated their absorbing device, officially called an "omnidirectional electromagnetic absorber," using 60 strips of circuit board arranged in concentric layers coated in copper. Each layer is imprinted with alternating patterns, which resonate or don't resonate in electromagnetic waves.

The designed device can trap and absorb electromagnetic waves coming from all directions by spiraling the radiation inwards and converting its energy into heat with an absorption rate of 99%. Hence it behaves like an "electromagnetic black body" or an "electromagnetic black hole."

At the moment, the device only works with microwaves, but the researchers are planning to develop a black hole for visible light next.

The current results could find some applications in microwaves. As the researchers write, "The good agreement between theoretical and experimental results has shown the excellent ability for metamaterials as the candidate to construct artificial omnidirectional absorbing devices.

"Since the lossy core can transfer electromagnetic energies into heat energies, we expect that the proposed device could find important applications in thermal emitting and electromagnetic-wave harvesting."

How to Treat Heat Like Light: New Approach Using Nanoparticle Alloys Allows Heat to Be Focused or Reflected Just Like Electromagnetic Waves

Jan. 11, 2013 — An MIT researcher has developed a technique that provides a new way of manipulating heat, allowing it to be controlled much as light waves can be manipulated by lenses and mirrors.

Thermal lattices. (Credit: Image courtesy of the researchers)

The approach relies on engineered materials consisting of nanostructured semiconductor alloy crystals. Heat is a vibration of matter -- technically, a vibration of the atomic lattice of a material -- just as sound is. Such vibrations can also be thought of as a stream of phonons -- a kind of "virtual particle" that is analogous to the photons that carry light. The new approach is similar to recently developed photonic crystals that can control the passage of light, and phononic crystals that can do the same for sound.

The spacing of tiny gaps in these materials is tuned to match the wavelength of the heat phonons, explains Martin Maldovan, a research scientist in MIT's Department of Materials Science and Engineering and author of a paper on the new findings published Jan. 11 in the journal Physical Review Letters.

"It's a completely new way to manipulate heat," Maldovan says. Heat differs from sound, he explains, in the frequency of its vibrations: Sound waves consist of lower frequencies (up to the kilohertz range, or thousands of vibrations per second), while heat arises from higher frequencies (in the terahertz range, or trillions of vibrations per second).

In order to apply the techniques already developed to manipulate sound, Maldovan's first step was to reduce the frequency of the heat phonons, bringing it closer to the sound range. He describes this as "hypersonic heat."

"Phonons for sound can travel for kilometers," Maldovan says -- which is why it's possible to hear noises from very far away. "But phonons of heat only travel for nanometers [billionths of a meter]. That's why you couldn't hear heat even with ears responding to terahertz frequencies."

Heat also spans a wide range of frequencies, he says, while sound spans a single frequency. So, to address that, Maldovan says, "the first thing we did is reduce the number of frequencies of heat, and we made them lower," bringing these frequencies down into the boundary zone between heat and sound. Making alloys of silicon that incorporate nanoparticles of germanium in a particular size range accomplished this lowering of frequency, he says.

Reducing the range of frequencies was also accomplished by making a series of thin films of the material, so that scattering of phonons would take place at the boundaries. This ends up concentrating most of the heat phonons within a relatively narrow "window" of frequencies.

Following the application of these techniques, more than 40 percent of the total heat flow is concentrated within a hypersonic range of 100 to 300 gigahertz, and most of the phonons align in a narrow beam, instead of moving in every direction.

As a result, this beam of narrow-frequency phonons can be manipulated using phononic crystals similar to those developed to control sound phonons. Because these crystals are now being used to control heat instead, Maldovan refers to them as "thermocrystals," a new category of materials.

These thermocrystals might have a wide range of applications, he suggests, including in improved thermoelectric devices, which convert differences of temperature into electricity. Such devices transmit electricity freely while strictly controlling the flow of heat -- tasks that the thermocrystals could accomplish very effectively, Maldovan says.

Most conventional materials allow heat to travel in all directions, like ripples expanding outward from a pebble dropped in a pond; thermocrystals could instead produce the equivalent of those ripples only moving out in a single direction, Maldovan says. The crystals could also be used to create thermal diodes: materials in which heat can pass in one direction, but not in the reverse direction. Such a one-way heat flow could be useful in energy-efficient buildings in hot and cold climates.

Other variations of the material could be used to focus heat -- much like focusing light with a lens -- to concentrate it in a small area. Another intriguing possibility is thermal cloaking, Maldovan says: materials that prevent detection of heat, just as recently developed metamaterials can create "invisibility cloaks" to shield objects from detection by visible light or microwaves.

Rama Venkatasubramanian, senior research director at the Center for Solid State Energetics at RTI International in North Carolina, says this is "an interesting approach to control the various frequencies of the phonon spectra that conduct heat in a solid-state material."

The modeling used to develop this new system "needs to be further developed," Venkatasubramanian adds. "The theory of what wavelengths of phonons, and at what temperatures, contribute to how much heat transport is a complex problem even in simpler materials, let alone nanostructured materials, and these will have to be factored in -- so this paper will trigger more interest and study in that direction."

source:sciencedaily.

World's Most Complex 2-D Laser

World's Most Complex 2-D Laser Beamsteering Array Demonstrated

Jan. 17, 2013 — A new 2-D optical phased array technology will enable advanced LADAR and other defense applications.

A new 2-D optical phased array technology will enable advanced LADAR and other defense applications. (Credit: MIT)

Most people are familiar with the concept of RADAR. Radio frequency (RF) waves travel through the atmosphere, reflect off of a target, and return to the RADAR system to be processed. The amount of time it takes to return correlates to the object's distance. In recent decades, this technology has been revolutionized by electronically scanned (phased) arrays (ESAs), which transmit the RF waves in a particular direction without mechanical movement. Each emitter varies its phase and amplitude to form a RADAR beam in a particular direction through constructive and destructive interference with other emitters.

Similar to RADAR, laser detection and ranging, or LADAR, scans a field of view to determine distance and other information, but it uses optical beams instead of RF waves. LADAR provides a more detailed level of information that can be used for applications such as rapid 3-D mapping. However, current optical beam steering methods needed for LADAR, most of which are based on simple mechanical rotation, are simply too bulky, slow or inaccurate to meet the full potential of LADAR.

As reported in the current issue of the journal Nature, DARPA researchers have recently demonstrated the most complex 2-D optical phased array ever. The array, which has dimensions of only 576µm x 576µm, roughly the size of the head of a pin, is composed of 4,096 (64 x 64) nanoantennas integrated onto a silicon chip. Key to this breakthrough was developing a design that is scalable to a large number of nanoantennas, developing new microfabrication techniques, and integrating the electronic and photonic components onto a single chip.

"Integrating all the components of an optical phased array into a miniature 2-D chip configuration may lead to new capabilities for sensing and imaging," said Sanjay Raman, program manager for DARPA's Diverse Accessible Heterogeneous Integration (DAHI) program. "By bringing such functionality to a chip-scale form factor, this array can generate high-resolution beam patterns -- a capability that researchers have long tried to create with optical phased arrays. This chip is truly an enabling technology for a host of systems and may one day revolutionize LADAR in much the same way that ESAs revolutionized RADAR. Beyond LADAR, this chip may have applications for biomedical imaging, 3D holographic displays and ultra-high-data-rate communications."

This work was supported by funding from DARPA's Short-Range, Wide Field-of-View Extremely agile, Electronically Steered Photonic Emitter (SWEEPER) program under Josh Conway, and the Electronic-Photonic Heterogeneous Integration (E-PHI) thrust of the DAHI program. Future steps include integrating non-silicon laser elements with other photonic components and silicon-based control and processing electronics directly on-chip using E-PHI technologies currently under development.

source:sciencedaily.

First Fossil Bird With Teeth Specialized for Tough Diet

First Fossil Bird With Teeth Specialized for Tough Diet

Jan. 7, 2013 — Beak shape variation in Darwin's finches is a classic example of evolutionary adaptation, with beaks that vary widely in proportions and shape, reflecting a diversity of ecologies. While living birds have a beak to manipulate their food, their fossil bird ancestors had teeth. Now a new fossil discovery shows some fossil birds evolved teeth adapted for specialized diets.

Photograph of Sulcavis geeorum skull, a fossil bird from the Early Cretaceous (120 million-years-ago) of Liaoning Province, China with scale bar in millimeters. (Credit: Photograph by Stephanie Abramowicz)

A study of the teeth of a new species of early bird, Sulcavis geeorum, published in the latest issue of theJournal of Vertebrate Paleontology, suggests this fossil bird had a durophagous diet, meaning the bird's teeth were capable of eating prey with hard exoskeletons like insects or crabs. The researchers believe the teeth of the new specimen greatly increase the known diversity of tooth shape in early birds, and hints at previously unrecognized ecological diversity.

Sulcavis geeorum is an enantiornithine bird from the Early Cretaceous (121-125 million years ago) of Liaoning Province, China. Enantiornithine birds are an early group of birds, and the most numerous birds from the Mesozoic (the time of the dinosaurs). Sulcavisis the first discovery of a bird with ornamented tooth enamel. The dinosaurs -- from which birds evolved -- are mostly characterized by carnivorous teeth with special features for eating meat. The enantiornithines are unique among birds in showing minimal tooth reduction and a diversity of dental patterns. This new enantiornithine has robust teeth with grooves on the inside surface, which likely strengthened the teeth against harder food items.

No previous bird species have preserved ridges, striations, serrated edges, or any other form of dental ornamentation. "While other birds were losing their teeth, enantiornithines were evolving new morphologies and dental specializations. We still don't understand why enantiornithines were so successful in the Cretaceous but then died out -- maybe differences in diet played a part." says Jingmai O'Connor, lead author of the new study.

"This study highlights again how uneven the diversity of birds was during the Cretaceous. There are many more enantiornithines than any other group of early birds, each one with its own anatomical specialization." offers study co-author Luis Chiappe, from Natural History Museum of Los Angeles County.

source:sciencedaily.

Particles of Crystalline Quartz Wear Away Teeth

Jan. 9, 2013 — Dental microwear, the pattern of tiny marks on worn tooth surfaces, is an important basis for understanding the diets of fossil mammals, including those of our own lineage. Now nanoscale research by an international multidisciplinary group that included members of the Max Planck Institute for Evolutionary Anthropology in Leipzig has unraveled some of its causes. It turns out that quartz dust is the major culprit in wearing away tooth enamel.

Surface of a tooth, with two large scratches (dark blue lines) that have been caused by quartz particles. (Credit: © Peter Lucas, Kuwait University

Silica phytoliths, particles produced by plants, just rub enamel, and thus have a minor effect on its surface. The results suggest that scientists will have to revise what microwear can tell us about diets, and suggest that environmental factors like droughts and dust storms may have had a large effect on the longevity of teeth. In particular, East African hominins may have suffered during dust storms, particularly from particles carried in by seasonal winds from the Arabian peninsula.

New research published by the scientists in Leipzig suggests that the main cause of the physical wear of mammalian teeth is the extremely hard particles of crystalline quartz in soils in many parts of the world. To show this, single particles were mounted on flat-tipped titanium rods and slid over flat tooth enamel surfaces at known forces. Quartz particles could remove pieces of tooth enamel at extremely low forces, meaning that even during a single bite, these particles could abrade much of the surface of the tooth if they are present in numbers.

In contrast, fossilized plant remains, so-called phytoliths, indented the enamel under the same conditions, but without tissue removal. The effect of the considerably softer phytoliths is similar to that of a fingernail pressed against a softwood desk. This kind of mark, called a rubbing mark, is visible but purely cosmetic.

The Max Planck Institute's Amanda Henry provided the phytoliths for the study, and assisted in the interpretation. "This study suggests that phytoliths do affect teeth, but in a different manner than we previously thought," she says. A new theory of wear, developed by collaborator Tony Atkins from Reading in the UK, suggests exactly what geometrical and material conditions are required for abrasive versus rubbing contacts. "People have not realized the vital importance of factoring fracture toughness into wear analyses" says Prof. Atkins. Study leader and Kuwait University researcher Peter Lucas says "we think that we've gone a lot further with the analysis of microwear than previous investigations because we realized that to uncover the mechanisms that cause it, you need to go one level smaller -- to nanoscale. It is only then that the difference between relatively innocuous rubbing contacts and those that remove tooth tissues becomes clear." The team could distinguish between marks made by quartz dust, plant phytoliths, and also by enamel chips rubbing against larger pieces of enamel.

source:sciencedaily.

DNA Prefers to Dive Head First

DNA Prefers to Dive Head First Into Nanopores

Jan. 8, 2013 — If you want to understand a novel, it helps to start from the beginning rather than trying to pick up the plot from somewhere in the middle. The same goes for analyzing a strand of DNA. The best way to make sense of it is to look at it head to tail.

A preference for diving head first: When a DNA strand is captured and pulled through a nanopore, it’s much more likely to start the journey at one of its ends (top left) rather than being grabbed somewhere in the middle and pulled through in a folded configuration. (Credit: Stein lab/Brown University)

Luckily, according to a new study by physicists at Brown University, DNA molecules have a convenient tendency to cooperate.

The research, published in the journal Physical Review Letters, looks at the dynamics of how DNA molecules are captured by solid-state nanopores, tiny holes that soon may help sequence DNA at lightning speed. The study found that when a DNA strand is captured and pulled through a nanopore, it's much more likely to start the journey at one of its ends, rather than being grabbed somewhere in the middle and pulled through in a folded configuration.

"We think this is an important advance for understanding how DNA molecules interact with these nanopores," said Derek Stein, assistant professor of physics at Brown, who performed the research with graduate students Mirna Mihovilivic and Nick Haggerty. "If you want to do sequencing or some other analysis, you want the molecule going through the pore head to tail."

"What we found was that ends are special places ... and that has a consequence for the likelihood a molecule starts its journey from the end."Research into DNA sequencing with nanopores started a little over 15 years ago. The concept is fairly simple. A little hole, a few billionths of a meter across, is poked in a barrier separating two pools of salt water. An electric current is applied across the hole, which occasionally attracts a DNA molecule floating in the water. When that happens, the molecule is whipped through the pore in a fraction of a second. Scientists can then use sensors on the pore or other means to identify nucleotide bases, the building blocks of the genetic code.

The technology is advancing quickly, and the first nanopore sequencing devices are expected to be on the market very soon. But there are still basic questions about how molecules behave at the moment they're captured and before.

"What the molecules were doing before they're captured was a mystery and a matter of speculation," Stein said. "And we'd like to know because if you're trying to engineer something to control that molecule -- to get it to do what you want it to do -- you need to know what it's up to."

To find out what those molecules are up to, the researchers carefully tracked over 1,000 instances of a molecule zipping through a nanopore. The electric current through the pore provides a signal of how the molecule went through. Molecules that go through middle first have to be folded over in order to pass. That folded configuration takes up more space in the pore and blocks more of the current. So by looking at differences in the current, Stein and his team could count how many molecules went through head first and how many started somewhere in the middle.

The study found that molecules are several times more likely to be captured at or very near an end than at any other single point along the molecule.

"What we found was that ends are special places," Stein said. "The middle is different from an end, and that has a consequence for the likelihood a molecule starts its journey from the end or the middle."

Always room for Jell-O

As it turns out, there's an old theory that that explains these new experimental results quite well. It's the theory of Jell-O.

Jell-O is a polymer network -- a mass of squiggly polymer strands that attach to each other at random junctions. The squiggly strands are the reason Jell-O is a jiggly, semi-solid. The way in which the polymer strands connect to each other is not unlike the way a DNA strand connects to a nanopore in the instant it's captured. In water, DNA molecules are jumbled up in random squiggles much like the gelatin molecules in Jell-O.

"There's some powerful theory that describes how many ways the polymers in Jell-O can arrange and attach themselves," Stein said. "That turns out to be perfectly applicable to the problem of where these DNA molecules get captured by a nanopore."

When applied to DNA, the Jell-O theory predicts that if you were to count up all the possible configurations of a DNA strand at the moment of capture, you would find that there are more configurations in which it is captured by its end, compared to other points along the strand. It's a bit like the odds of getting a pair in poker compared to the odds of getting three of a kind. You're more likely to get a pair simply because there are more pairs in the deck than there are triples.

This measure of all the possible configurations -- a measure of what physicists refer to as the molecule's entropy -- is all that's needed to explain why DNA tends to go head first. Some scientists had speculated that perhaps strands would be less likely to go through by the middle because folding them in half would require extra energy. But that folding energy appears not to matter at all. As Stein puts it, "The number of ways that a molecule can find itself with its head sticking in the pore is simply larger than the number of ways it can find itself with the middle touching the pore."

These theories of polymer networks have actually been around for a while. They were first proposed by the late Nobel laureate Pierre-Gilles de Gennes in the 1960s, and Bertrand Duplantier made key advances in the 1980s. Mihovilivic, Stein's graduate student and the lead author of this study, says this is actually one of the first lab tests of those theories.

"They couldn't be tested until now, when we can actually do single molecule measurements," she said. "[De Gennes] postulated that one day it would be possible to test this. I think he would have been very excited to see it happen."

source:sciencedaily.

Scientists Mimic Fireflies to Make Brighter LEDs

Scientists Mimic Fireflies to Make Brighter LEDs: New Bio-Inspired Coating That Increases LED Efficiency by 55 Percent

Jan. 8, 2013 — The nighttime twinkling of fireflies has inspired scientists to modify a light-emitting diode (LED) so it is more than one and a half times as efficient as the original.

A GaN LED, coated with a “factory-roof” pattern modeled off the fireflies’ scales. The bio-inspired LED coating increased light extraction by more than 50 percent. (Credit: Nicolas Andr)

Researchers from Belgium, France, and Canada studied the internal structure of firefly lanterns, the organs on the bioluminescent insects' abdomens that flash to attract mates. The scientists identified an unexpected pattern of jagged scales that enhanced the lanterns' glow, and applied that knowledge to LED design to create an LED overlayer that mimicked the natural structure. The overlayer, which increased LED light extraction by up to 55 percent, could be easily tailored to existing diode designs to help humans light up the night while using less energy.

The work is published in a pair of papers today in the Optical Society's (OSA) open-access journal Optics Express.

"The most important aspect of this work is that it shows how much we can learn by carefully observing nature," says Annick Bay, a Ph.D. student at the University of Namur in Belgium who studies natural photonic structures, including beetle scales and butterfly wings. When her advisor, Jean Pol Vigneron, visited Central America to conduct field work on the Panamanian tortoise beetle (Charidotella egregia), he also noticed clouds of twinkling fireflies and brought some specimens back to the lab to examine in more detail.

Fireflies create light through a chemical reaction that takes place in specialized cells called photocytes. The light is emitted through a part of the insect's exoskeleton called the cuticle. Light travels through the cuticle more slowly than it travels through air, and the mismatch means a proportion of the light is reflected back into the lantern, dimming the glow. The unique surface geometry of some fireflies' cuticles, however, can help minimize internal reflections, meaning more light escapes to reach the eyes of potential firefly suitors.

In Optics Express papers, Bay, Vigneron, and colleagues first describe the intricate structures they saw when they examined firefly lanterns and then present how the same features could enhance LED design. Using scanning electron microscopes, the researchers identified structures such as nanoscale ribs and larger, misfit scales, on the fireflies' cuticles. When the researchers used computer simulations to model how the structures affected light transmission they found that the sharp edges of the jagged, misfit scales let out the most light. The finding was confirmed experimentally when the researchers observed the edges glowing the brightest when the cuticle was illuminated from below.

"We refer to the edge structures as having a factory roof shape," says Bay. "The tips of the scales protrude and have a tilted slope, like a factory roof." The protrusions repeat approximately every 10 micrometers, with a height of approximately 3 micrometers. "In the beginning we thought smaller nanoscale structures would be most important, but surprisingly in the end we found the structure that was the most effective in improving light extraction was this big-scale structure," says Bay.

Human-made light-emitting devices like LEDs face the same internal reflection problems as fireflies' lanterns and Bay and her colleagues thought a factory roof-shaped coating could make LEDs brighter. In the second Optics Express paper published today, which is included in the Energy Express section of the journal, the researchers describe the method they used to create a jagged overlayer on top of a standard gallium nitride LED. Nicolas André, a postdoctoral researcher at the University of Sherbrooke in Canada, deposited a layer of light-sensitive material on top of the LEDs and then exposed sections with a laser to create the triangular factory-roof profile. Since the LEDs were made from a material that slowed light even more than the fireflies' cuticle, the scientists adjusted the dimensions of the protrusions to a height and width of 5 micrometers to maximize the light extraction.

"What's nice about our technique is that it's an easy process and we don't have to create new LEDs," says Bay. "With a few more steps we can coat and laser pattern an existing LED."

Other research groups have studied the photonic structures in firefly lanterns as well, and have even mimicked some of the structures to enhance light extraction in LEDs, but their work focused on nanoscale features. The Belgium-led team is the first to identify micrometer-scale photonic features, which are larger than the wavelength of visible light, but which surprisingly improved light extraction better than the smaller nanoscale features. The factory roof coating that the researchers tested increased light extraction by more than 50 percent, a significantly higher percentage than other biomimicry approaches have achieved to date. The researchers speculate that, with achievable modifications to current manufacturing techniques, it should be possible to apply these novel design enhancements to current LED production within the next few years.

The firefly specimens that served as the inspiration for the effective new LED coating came from the genus Photuris, which is commonly found in Latin America and the United States. Bay says she has also examined the lanterns of a particularly hardy species of firefly found on the Caribbean island of Guadeloupe that did not have the factory roof structure on the outer layer. She notes that she and her colleagues will continue to explore the great diversity of the natural world, searching for new sources of knowledge and inspiration. "ThePhoturis fireflies are very effective light emitters, but I am quite sure that there are other species that are even more effective," says Bay. "This work is not over."

source:sciencedaily

The Self-Assembling Particles That Come from InSPACE

Jan. 7, 2013 — Shape-shifting malleable, gelatinous forms are orbiting Earth at this very moment -- assembling and disassembling, growing as they are bombarded by magnetic pulses. These forms will take shape as astronauts run experiments involving smart fluids aboard the International Space Station.

NASA astronaut Suni Williams photographing InSPACE-3 vial assembly after particles redistribution operation on the International Space Station. (Credit: NASA)

While they may change shape, the forms are not things of science fiction. They are the things of fundamental science.

The purpose of the Investigating the Structures of Paramagnetic Aggregates from Colloidal Emulsions-3, or InSPACE-3, study is to gather fundamental data about Magnetorheological, or MR fluids. These fluids are a type of smart fluid that tends to self-assemble into shapes. When they are exposed to a magnetic field, they can quickly transition into a nearly solid-like state. When the magnetic field is removed, they return to a liquid state.

"Initially the particles in the fluid form long, thin chains," said Eric Furst, InSPACE-3 principal investigator, University of Delaware, Newark, Del. "The magnetic dipoles induced in the particles cause these singular chains to grow parallel to the applied field. Over time the chains parallel to each other interact and bond together. These 'bundles' of chains become more like columns when the magnetic field is toggled on and off. And these columns grow in diameter with time exposed to a pulsed magnetic field."

This self-directed "bundling" was never before observed until it was seen in an earlier space station investigation, InSPACE-2, which ended in 2009. The results of InSPACE-2 were highlighted in a September 2012 article titled "Multi-scale Kinetics of a Field-directed Phase Transition" published in the Proceedings of the National Academy of Sciences.

"Earlier InSPACE investigations looked at MR fluids composed of spherical, or round, particles," said Bob Green, InSPACE-3 project scientist, NASA's Glenn Research Center, Cleveland, Ohio. "InSPACE-3 is focused on oval or ellipsoid-shaped particles. The expectation is that these shapes will pack differently and form column-like structures differently than in previous experiments. The particles in InSPACE-3 are made of a polystyrene material embedded with tiny nano-sized iron oxide particles."

Iron oxide is chemically similar to rust. In fact, when the fluid is mixed, it has a brownish rust-type hue. Astronauts, under the direction of the project team, are currently running a series of experiments on this rust-colored mixture and will continue to do so for the next few months.

"We have six vials of which three are primary and three are backups," said Nang Pham, InSPACE-3 project manager at Glenn. "We'll run 12 tests on each of the three vials of different sized ellipsoid-shaped particles for a total of 36 test runs."

A test run could be changing the frequency of the magnetic pulse, altering the magnetic field strength, or using different particle sizes. The first InSPACE-3 test was Oct. 5. Plans are to complete the test runs in early 2013.

For the investigation, astronauts apply a magnetic field of a certain strength, which is pulsed from a low frequency of around 0.66 hertz up to 20 hertz. The pulse is on for a very short time and then is turned off. Scientists are looking for formation of structures that are at a lower energy state. Typically in an MR fluid application, a constant field is applied and the particles form a gel-like structure. They don't pack very well, so the particles have no definite form. They are like a cloud or hot glass that can form into almost any shape.

In a pulsed field, the on-off magnetic field forces the particles to assemble, disassemble, assemble, disassemble and so on. This on-and-off action occurs in millisecond pulses over the approximately two hours of the experiment. In this pulsed field, the particles organize into a more tightly packed structure. Scientists can then measure and plot the column growth over time.

"The idea is to understand the fundamental science around this directed self-assembly in the hopes of better defining new methods of manufacturing materials composed of small colloidal or nanoparticle building blocks," Furst said.

New manufacturing models resulting from InSPACE-2 and -3 studies could be used to improve or develop active mechanical systems such as new brake systems, seat suspensions, stress transducers, robotics, rovers, airplane landing gears and vibration damping systems.

Coupled with the work of InSPACE-2, the InSPACE-3 investigation into fundamental science could advance these systems and improve how we ride, drive and fly. Thanks to these space station investigations, the fluids that come from space may one day further improve your daily commute, whether on the highway or off the road.

New Path to More Efficient Organic Solar Cells Uncovered

Jan. 7, 2013 — Why are efficient and affordable solar cells so highly coveted? Volume. The amount of solar energy lighting up Earth's land mass every year is nearly 3,000 times the total amount of annual human energy use. But to compete with energy from fossil fuels, photovoltaic devices must convert sunlight to electricity with a certain measure of efficiency. For polymer-based organic photovoltaic cells, which are far less expensive to manufacture than silicon-based solar cells, scientists have long believed that the key to high efficiencies rests in the purity of the polymer/organic cell's two domains -- acceptor and donor. Now, however, an alternate and possibly easier route forward has been shown.

Molecular view of polymer/fullerene solar film showing an interface between acceptor and donor domains. Red dots are PC71BM molecules and blue lines represent PTB7 chains. Excitons are shown as yellow dots, purple dots are electrons and green dots represent holes. (Credit: Image courtesy of Harald Ade, NC State University)

Working at Berkeley Lab's Advanced Light Source (ALS), a premier source of X-ray and ultraviolet light beams for research, an international team of scientists found that for highly efficient polymer/organic photovoltaic cells, size matters.

"We've shown that impure domains if made sufficiently small can also lead to improved performances in polymer-based organic photovoltaic cells," says Harald Ade, a physicist at North Carolina State University, who led this research. "There seems to be a happy medium, a sweet-spot of sorts, between purity and domain size that should be much easier to achieve than ultra-high purity."

Ade, a longtime user of the ALS, is the corresponding author of a paper describing this work in Advanced Energy Materials titled "Absolute Measurement of Domain Composition and Nanoscale Size Distribution Explains Performance in PTB7:PC71 BM Solar Cells." Co-authors are Brian Collins, Zhe Li, John Tumbleston, Eliot Gann and Christopher McNeill.

Solar cell conversion efficiency in polymer/organic photovoltaic cells hinges on excitons -- electron/hole pairs energized by sunlight -- getting to the interfaces of the donor and acceptor domains quickly so as to minimize energy lost as heat. Conventional wisdom held that the greater the purity of the domains, the fewer the impedances and the faster the exciton journey.

Ade and his co-authors became the first to simultaneously measure the domain size, composition and crystallinity of an organic solar cell. This feat was made possible by ALS beamlines 11.0.1.2, a Resonant Soft X-ray Scattering (R-SoXS) facility; 7.3.3, a Small- and Wide-Angle X-Ray Scattering (SAXS/WAXS/) end-station; and 5.3.2, an end-station for Scanning Transmission X-Ray Microscopy (STXM).

Says Collins, the first author on the Advanced Energy Materialspaper, "The combination of these three ALS beamlines enabled us to obtain comprehensive pictures of polymer-based organic photovoltaic film morphology from the nano- to the meso-scales. Until now, this information has been unattainable."

The international team used the trifecta of ALS beams to study the polymer/fullerence blend PTB7:PC₇₁BM in thin films made from chlorobenzene solution with and without the addition (three-percent by volume) of the solvent diiodooctane. The films were composed of droplet-like dispersions in which the dominant acceptor domain size without the additive was about 177 nanometers. The addition of the solvent shrank the acceptor domain size down to about 34 nanometers while preserving the film's composition and crystallinity. This resulted in an efficiency gain of 42-percent.

"In showing for the first time just how pure and how large the acceptor domains in organic solar devices actually are, as well as what the interface with the donor domain looks like, we've demonstrated that the impact of solvents and additives on device performance can be dramatic and can be systematically studied," Ade says. "In the future, our technique should help advance the rational design of polymer-based organic photovoltaic films."

This research was primarily supported by the DOE Office of Science, which also supports the ALS.

Jumping Droplets Help Heat Transfer

Jumping Droplets Help Heat Transfer: Scalable Nanopatterned Surfaces for More Efficient Power Generation and Desalination

Jan. 4, 2013 — Many industrial plants depend on water vapor condensing on metal plates: In power plants, the resulting water is then returned to a boiler to be vaporized again; in desalination plants, it yields a supply of clean water. The efficiency of such plants depends crucially on how easily droplets of water can form on these metal plates, or condensers, and how easily they fall away, leaving room for more droplets to form.

The key to improving the efficiency of such plants is to increase the condensers' heat-transfer coefficient -- a measure of how readily heat can be transferred away from those surfaces, explains Nenad Miljkovic, a doctoral student in mechanical engineering at MIT. As part of his thesis research, he and colleagues have done just that: designing, making and testing a coated surface with nanostructured patterns that greatly increase the heat-transfer coefficient.

The results of that work have been published in the journal Nano Letters, in a paper co-authored by Miljkovic, mechanical engineering associate professor Evelyn Wang, and five other researchers from the Device Research Lab (DRL) in MIT's mechanical engineering department.

On a typical, flat-plate condenser, water vapor condenses to form a liquid film on the surface, drastically reducing the condenser's ability to collect more water until gravity drains the film. "It acts as a barrier to heat transfer," Miljkovic says. He and other researchers have focused on ways of encouraging water to bead up into droplets that then fall away from the surface, allowing more rapid water removal.

"The way to remove the thermal barrier is to remove [the droplets] as quickly as possible," he says. Many researchers have studied ways of doing this by creating hydrophobic surfaces, either through chemical treatment or through surface patterning. But Miljkovic and his colleagues have now taken this a step further by making scalable surfaces with nanoscale features that barely touch the droplets.

The result: Droplets don't just fall from the surface, but actually jump away from it, increasing the efficiency of the process. The energy released as tiny droplets merge to form larger ones is enough to propel the droplets upward from the surface, meaning the removal of droplets doesn't depend solely on gravity.

Other researchers have worked on nanopatterned surfaces to induce such jumping, but these have tended to be complex and expensive to manufacture, usually requiring a clean-room environment. Those approaches also require flat surfaces, not the tubing or other shapes often used in condensers. Finally, prior research has not tested the enhanced heat transfer predicted for these types of surfaces.

In a paper published early in 2012, the MIT researchers showed that droplet shape is important to enhanced heat transfer. "Now, we've gone a step further," Miljkovic says, "developing a surface that favors these kinds of droplets, while being highly scalable and easy to manufacture. Furthermore, we've actually been able to experimentally measure the heat-transfer enhancement."

The patterning is done, Miljkovic says, using a simple wet-oxidation process right on the surface that can be applied to the copper tubes and plates commonly used in commercial power plants.

The nanostructured pattern itself is made of copper oxide and actually forms on top of the copper tubing. The process produces a surface that resembles a bed of tiny, pointed leaves sticking up from the surface; these nanoscale points minimize contact between the droplets and the surface, making release easier.

Not only can the nanostructured patterns be made and applied under room-temperature conditions, but the growth process naturally stops itself. "It's a self-limiting reaction," Miljkovic says, "whether you put it in [the treatment solution] for two minutes or two hours."

After the leaflike pattern is created, a hydrophobic coating is applied when a vapor solution bonds itself to the patterned surface without significantly altering its shape. The team's experiments showed that the efficiency of heat transfer using these treated surfaces could be increased by 30 percent, compared to today's best hydrophobic condensing surfaces.

That means, Miljkovic says, that the process lends itself to retrofitting thousands of power plants already in operation around the world. The technology could also be useful for other processes where heat transfer is important, such as in dehumidifiers and for heating and cooling systems for buildings, the authors say.

Challenges for this approach remain, Miljkovic says: If too many droplets form, they can "flood" the surface, reducing its heat-transfer ability. "We are working on delaying this surface flooding and creating more robust solutions that can work well [under] all operating conditions," he says.

The research team also included postdocs Ryan Enright and Youngsuk Nam and undergraduates Ken Lopez, Nicholas Dou and Jean Sack, all of MIT's mechanical engineering department.

Perfectly Spherical Gold Nanodroplets Produced With the Smallest-Ever Nanojets

Jan. 14, 2012 — KU Leuven researcher Ventsislav Valev and an international team of scientists have developed a new method for optical manipulation of matter at the nanoscale. Using 'plasmonic hotspots' -- regions with electric current that heat up very locally -- gold nanostructures can be melted and made to produce the smallest nanojets ever observed. The tiny gold nanodroplets formed in the nanojets, are perfectly spherical, which makes them interesting for applications in medicine.

Similar to the way water backjets eject droplets of water on the surface of a pond, powerful laser pulses can locally melt gold nanostructures and produce gold nanojets, ejecting perfectly spherical gold nanodroplets. (Credit: Image courtesy of Katholieke Universiteit Leuven)

The 'backjet' phenomenon on which the method turns can be compared to a pebble being dropped into water. Tightly focused ultrafast laser pulses carry sufficient energy to locally melt the surface of a gold film. When a laser pulse of light hits the film, a nanoscale backjet -- a nanojet -- of molten gold surges upward.

As the name suggests, nanojets on the surface of a homogeneous gold film are incredibly small, their size being determined by the distribution of energy in the light pulse. This distribution of energy is in turn dependent on the wavelength of light. Initially, scientists anticipated that nanojets could not be significantly smaller than the wavelength of light. In this study however, Ventsislav Valev and his colleagues show that nanojets can in fact be made much smaller with the help of 'plasmonic hotspots'.

Plasmonic hotspots are regions on the surface of metal nanostructures where light causes very strong oscillation of the electrons. Because electron oscillations constitute an electric current and because electric currents heat up the material the same way an electric stove heats up in the kitchen, the plasmonic hotspots are extremely hot. So hot that they can melt the gold in a spot much smaller than the wavelength of light. Dr. Valev and his colleagues were successfully able to demonstrate that this tiny little pool of molten gold can give rise to the smallest nanojets ever observed.

The gold nanodroplets propelled upward by the nanojets solidify in flight, producing perfectly spherical nanoparticles. These gold nanodroplets can be collected and used for medical applications including cancer treatment. The nanoparticles can be attached to molecules and injected in the blood. Once the molecules attach to cancer cells, light can be used to heat up the gold nanodroplets and destroy the cancer cells. Currently, the gold nanoparticles used in medications are chemically synthesised. These chemically synthesised gold nanoparticles have an unavoidably granular aspect. Conversely, gold nanodroplets created by the plasmonic nanojet method detailed by Dr. Valev and his colleagues are perfectly spherical, ensuring a better efficiency.

source:sciencedaily.

10 Nano gadgets to slip in your pocket

The trend toward owning smaller and smaller gadgets with greater features is growing greatly and hence companies are designing more and more nano gadgets everyday. Nano gadgets try and cram intricate circuitry into smaller sizes so that you can make use of all the awesome features in a compact design.

Here are a few nano gadgets that do not compromise on any features in spite of being so small and portable.

1. Mitsubishi’s Pocket Projector

This pocket projector by Mitsubishi weighs as less as 14 ounces and sells at a price of around $449. This projector is not exactly small enough to fit into your pockets but it can be easily carried around on the palm of your hand. The projector has a resolution of 800 x 600 which is good enough for all your basic projector needs.

2. Micro projector fits into your pocket

This micro projector is capable of fitting into a laptop, a mobile phone or maybe even an mp3 reader. This device was developed by Lemoptix in collaboration with Maher Kayal Laboratory. The projector is capable of functioning just as any other projector and the size of the images displayed can also be modified by changing the distance between the projector and the projection surface.

3. Pocket Pal MP3 Player

The unique feature of this mp3 player is that you can control the device from a different location. The magnetized knob on the player is removable and can be used to change the songs or control the volume. If simplicity is your thing then this extremely portable mp3 player is the thing for you.

4. MicroEmissive Displays

A few years back, the screen size of this device was voted as the smallest, even by the Guinness book of World records. This portable television screen has been created by MicroEmissive Displays, a Scottish firm.

5. Mint V10 projector

The Mint V10 Projector has been created by an Australian company Mint Wireless in collaboration with Taiwanese company Aiptek .The Mint V10 Projector has an internal memory and can run for an hour on a single charge. This device can also be used alongside DVD players, PS3 or any other multimedia device and comes with inbuilt stereo speakers.

6. Multitasking ladybug

If you want a memory Card Reader, a UV money detector light, mini 5pin data cable and flash drive, all in one single, extremely portable unit, then this is the device for you. This device can store up to 4GB of data and looks stylish too, in its great ladybird avatar.

7. Spark Nano GPS Tracker

The Spark Nano GPS Tracker has been created by Brickhouse Security works on both GPRS and GSM networks, hence allowing for a better area of coverage. This device comes with an in built panic button and it is great for keeping an eye on your kids. The device also allows for real time location updates on your laptop, mobile or email, whatever you prefer.

8. Mini DV Camera

This very tiny video camera weighs 50g and measures just 55 x 20 x 18 mm. The camera has a back up time of 2 hours and come with a USB port along with a MicroSD slot of up to 8GB. This device is perfect for the home video experts or aspiring secret agents.

9. Camball world’s smallest personal camcorder

Roughly the size of a ping-pong ball, this camcorder called CamBall can shoot 320 x 240 video at 25 frames per second and come with an in-built motion detector and mic. This water proof camcorder has a battery life of 2.5 hours and costs approximately $199.

10. Swiftpoint Slider Mouse

Anybody with an eye for minute detailing would love to own this gadget. You can use this mouse like any other regular mouse, the only difference being the swift slider that gives you complete control of movements. The downside it is so small that it is susceptible to easily getting lost!