Incredibly light, strong materials recover original shape after being smashed

Incredibly light, strong materials recover original shape after being smashed

  4:10:00 PM    Science Lover

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Materials scientists have developed a method for creating new structural materials by taking advantage of the unusual properties that solids can have at the nanometer scale. They have used the method to produce a ceramic (e.g., a piece of chalk or a brick) that contains about 99.9 percent air yet is incredibly strong and can recover its original shape after being smashed by more than 50 percent.

This sequence shows how the Greer Lab's three-dimensional,
ceramic nanolattices can recover after being compressed by
more than 50 percent. Clockwise, from left to right, an alumina
nanolattice before compression, during compression, fully
compressed, and recovered following compression.

Credit: Lucas Meza/Caltech

Imagine a balloon that could float without using any lighter-than-air gas. Instead, it could simply have all of its air sucked out while maintaining its filled shape. Such a vacuum balloon, which could help ease the world's current shortage of helium, can only be made if a new material existed that was strong enough to sustain the pressure generated by forcing out all that air while still being lightweight and flexible. 

Caltech materials scientist Julia Greer and her colleagues are on the path to developing such a material and many others that possess unheard-of combinations of properties. For example, they might create a material that is thermally insulating but also extremely lightweight, or one that is simultaneously strong, lightweight, and nonbreakable -- properties that are generally thought to be mutually exclusive.

Greer's team has developed a method for constructing new structural materials by taking advantage of the unusual properties that solids can have at the nanometer scale, where features are measured in billionths of meters. In a paper published in the September 12 issue of the journal Science, the Caltech researchers explain how they used the method to produce a ceramic (e.g., a piece of chalk or a brick) that contains about 99.9 percent air yet is incredibly strong, and that can recover its original shape after being smashed by more than 50 percent.

"Ceramics have always been thought to be heavy and brittle," says Greer, a professor of materials science and mechanics in the Division of Engineering and Applied Science at Caltech. "We're showing that in fact, they don't have to be either. This very clearly demonstrates that if you use the concept of the nanoscale to create structures and then use those nanostructures like LEGO to construct larger materials, you can obtain nearly any set of properties you want. You can create materials by design."

The researchers use a direct laser writing method called two-photon lithography to "write" a three-dimensional pattern in a polymer by allowing a laser beam to crosslink and harden the polymer wherever it is focused. The parts of the polymer that were exposed to the laser remain intact while the rest is dissolved away, revealing a three-dimensional scaffold. That structure can then be coated with a thin layer of just about any kind of material -- a metal, an alloy, a glass, a semiconductor, etc. Then the researchers use another method to etch out the polymer from within the structure, leaving a hollow architecture.

The applications of this technique are practically limitless, Greer says. Since pretty much any material can be deposited on the scaffolds, the method could be particularly useful for applications in optics, energy efficiency, and biomedicine. For example, it could be used to reproduce complex structures such as bone, producing a scaffold out of biocompatible materials on which cells could proliferate.

In the latest work, Greer and her students used the technique to produce what they call three-dimensional nanolattices that are formed by a repeating nanoscale pattern. After the patterning step, they coated the polymer scaffold with a ceramic called alumina (i.e., aluminum oxide), producing hollow-tube alumina structures with walls ranging in thickness from 5 to 60 nanometers and tubes from 450 to 1,380 nanometers in diameter.

Greer's team next wanted to test the mechanical properties of the various nanolattices they created. Using two different devices for poking and prodding materials on the nanoscale, they squished, stretched, and otherwise tried to deform the samples to see how they held up.

They found that the alumina structures with a wall thickness of 50 nanometers and a tube diameter of about 1 micron shattered when compressed. That was not surprising given that ceramics, especially those that are porous, are brittle. However, compressing lattices with a lower ratio of wall thickness to tube diameter -- where the wall thickness was only 10 nanometers -- produced a very different result.

"You deform it, and all of a sudden, it springs back," Greer says. "In some cases, we were able to deform these samples by as much as 85 percent, and they could still recover."

To understand why, consider that most brittle materials such as ceramics, silicon, and glass shatter because they are filled with flaws -- imperfections such as small voids and inclusions. The more perfect the material, the less likely you are to find a weak spot where it will fail. Therefore, the researchers hypothesize, when you reduce these structures down to the point where individual walls are only 10 nanometers thick, both the number of flaws and the size of any flaws are kept to a minimum, making the whole structure much less likely to fail.

"One of the benefits of using nanolattices is that you significantly improve the quality of the material because you're using such small dimensions," Greer says. "It's basically as close to an ideal material as you can get, and you get the added benefit of needing only a very small amount of material in making them."

The Greer lab is now aggressively pursuing various ways of scaling up the production of these so-called meta-materials.

Story Source: http://www.sciencedaily.com/releases/2014/09/140911135450.htm

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For better batteries, just add water

For better batteries, just add water

  12:29:00 AM    Science Lover

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A new type of lithium-ion battery that uses aqueous iodide ions in an aqueous cathode configuration provides twice the energy density of conventional lithium-ion batteries.

A new type of lithium-ion battery that uses aqueous iodide ions
in an aqueous cathode configuration provides twice the energy
density of conventional lithium-ion batteries.

Lithium-ion batteries are now found everywhere in devices such as cellular phones and laptop computers, where they perform well. In automotive applications, however, engineers face the challenge of squeezing enough lithium-ion batteries onto a vehicle to provide the desired power and range without introducing storage and weight issues. Hye Ryung Byon, Yu Zhao and Lina Wang from the RIKEN Byon Initiative Research Unit have now developed a lithium-iodine battery system with twice the energy density of conventional lithium-ion batteries.

Byon's team is involved in alternative energy research and, specifically, improving the performance of lithium-based battery technologies. In their research they turned to an 'aqueous' system in which the organic electrolyte in conventional lithium-ion cells is replaced with water. Such aqueous lithium battery technologies have gained attention among alternative energy researchers because of their greatly reduced fire risk and environmental hazard. Aqueous solutions also have other advantages, which include an inherently high ionic conductivity.

For their battery system, the researchers investigated an 'aqueous cathode' configuration (Fig. 1), which accelerates reduction and oxidation reactions to improve battery performance. Finding suitable reagents for the aqueous cathode, however, proved to be a tricky proposition. According to Byon, water solubility is the most important criterion for screening new materials, since this parameter determines the battery's energy density. Furthermore, the redox reaction has to take place in a restricted voltage range in order to avoid water electrolysis. An extensive search led the researchers to produce the first-ever lithium battery involving aqueous iodine—an element with high water solubility and a pair of ions, known as the triiodide/iodide redox couple, that readily undergo aqueous electrochemical reactions.

The team constructed a prototype aqueous cathode device and found the energy density to be nearly double that of a conventional lithium-ion battery, thanks to the high solubility of the triiodide/iodide ions. Their battery had high and near-ideal power storage capacities and could be successfully recharged hundreds of times, avoiding a problem that plagues other alternative high-energy-density lithium-ion batteries. Microscopy analysis revealed that the cathode collector remained untouched after 100 charge/discharge cycles with no observable corrosion or precipitate formation.

Byon and colleagues now plan to develop a three-dimensional, microstructured current collector that could enhance the diffusion-controlled triiodide/iodide process and accelerate charge and discharge. They are also seeking to raise energy densities even further by using a flowing-electrode configuration that stores aqueous 'fuel' in an external reservoir—a modification that should make this low-cost, heavy metal-free design more amenable to electric vehicle specifications.
More information: 1.Zhao, Y., Wang, L. & Byon, H. R. High-performance rechargeable lithium-iodine batteries using triiodide/iodide redox couples in an aqueous cathode. Nature Communications 4, 1896 (2013). dx.doi.org/10.1038/ncomms2907

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More data storage? Here's how to fit 1,000 terabytes on a DVD

More data storage? Here's how to fit 1,000 terabytes on a DVD

  1:17:00 AM    Science Lover

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We live in a world where digital information is exploding. Some 90% of the world's data was generated in the past two years. The obvious question is: how can we store it all?

Using nanotechnology, researchers have developed a technique to increase the data storage capacity of a DVD from a measly 4.7GB to 1,000TB. Credit: Nature Communications

In Nature Communications today, we, along with Richard Evans from CSIRO, show how we developed a new technique to enable the data capacity of a single DVD to increase from 4.7 gigabytes up to one petabyte (1,000 terabytes). This is equivalent of 10.6 years of compressed high-definition video or 50,000 full high-definition movies.

So how did we manage to achieve such a huge boost in data storage? First, we need to understand how data is stored on optical discs such as CDs and DVDs.

The basics of digital storage

Although optical discs are used to carry software, films, games, and private data, and have great advantages over other recording media in terms of cost, longevity and reliability, their low data storage capacity is their major limiting factor.

The operation of optical data storage is rather simple. When you burn a CD, for example, the information is transformed to strings of binary digits (0s and 1s, also called bits). Each bit is then laser "burned" into the disc, using a single beam of light, in the form of dots.

The storage capacity of optical discs is mainly limited by the physical dimensions of the dots. But as there's a limit to the size of the disc as well as the size of the dots, many current methods of data storage, such as DVDs and Blu-ray discs, continue to have low level storage density.

To get around this, we had to look at light's fundamental laws.
On the basis of this law, the diameter of a spot of light, obtained by focusing a light beam through a lens, cannot be smaller than half its wavelength – around 500 nanometres (500 billionths of a metre) for visible light.

And while this law plays a huge role in modern optical microscopy, it also sets up a barrier for any efforts from researchers to produce extremely small dots – in the nanometre region – to use as binary bits.

In our study, we showed how to break this fundamental limit by using a two-light-beam method, with different colours, for recording onto discs instead of the conventional single-light-beam method.

Both beams must abide by Abbe's law, so they cannot produce smaller dots individually. But we gave the two beams different functions:

• The first beam (red, in the figure right) has a round shape, and is used to activate the recording. We called it the writing beam
• The second beam – the purple donut-shape – plays an anti-recording function, inhibiting the function of the writing beam

The two beams were then overlapped. As the second beam cancelled out the first in its donut ring, the recording process was tightly confined to the centre of the writing beam.

This new technique produces an effective focal spot of nine nanometres – or one ten thousandth the diameter of a human hair.

The technique, in practical terms

Our work will greatly impact the development of super-compact devices as well as nanoscience and nanotechnology research.

The exceptional penetration feature of light beams allow for 3D recording or fabrication, which can dramatically increase the data storage – the number of dots – on a single optical device.

The technique is also cost-effective and portable, as only conventional optical and laser elements are used, and allows for the development of optical data storage with long life and low energy consumption, which could be an ideal platform for a Big Data centre.

As the rate of information generated worldwide continues to accelerate, the aim of more storage capacity in compact devices will continue. Our breakthrough has put that target within our reach.

 

More information: www.nature.com/ncomms/2013/130619/ncomms3061/full/ncomms3061.html 

 

Story from: http://phys.org/news/2013-06-storage-terabytes-dvd.html#ajTabs

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Beyond Silicon: Transistors, No Semiconductors

Beyond Silicon: Transistors, No Semiconductors

  11:59:00 PM    Science Lover

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For decades, electronic devices have been getting smaller, and smaller, and smaller. It's now possible -- even routine -- to place millions of transistors on a single silicon chip.

Electrons flash across a series of gold quantum dots on boron 
nitride nanotubes. Michigan Tech scientists made the quantum
-tunneling device, which acts like a transistor at room 
temperature, without using semiconducting materials. 
(Credit: Yoke Khin Yap graphic)

But transistors based on semiconductors can only get so small. "At the rate the current technology is progressing, in 10 or 20 years, they won't be able to get any smaller," said physicist Yoke Khin Yap of Michigan Technological University. "Also, semiconductors have another disadvantage: they waste a lot of energy in the form of heat."

Scientists have experimented with different materials and designs for transistors to address these issues, always using semiconductors like silicon. Back in 2007, Yap wanted to try something different that might open the door to a new age of electronics.

"The idea was to make a transistor using a nanoscale insulator with nanoscale metals on top," he said. "In principle, you could get a piece of plastic and spread a handful of metal powders on top to make the devices, if you do it right. But we were trying to create it in nanoscale, so we chose a nanoscale insulator, boron nitride nanotubes, or BNNTs for the substrate."

Yap's team had figured out how to make virtual carpets of BNNTs,which happen to be insulators and thus highly resistant to electrical charge. Using lasers, the team then placed quantum dots (QDs) of gold as small as three nanometers across on the tops of the BNNTs, forming QDs-BNNTs. BNNTs are the perfect substrates for these quantum dots due to their small, controllable, and uniform diameters, as well as their insulating nature. BNNTs confine the size of the dots that can be deposited.

In collaboration with scientists at Oak Ridge National Laboratory (ORNL), they fired up electrodes on both ends of the QDs-BNNTs at room temperature, and something interesting happened. Electrons jumped very precisely from gold dot to gold dot, a phenomenon known as quantum tunneling.

"Imagine that the nanotubes are a river, with an electrode on each bank. Now imagine some very tiny stepping stones across the river," said Yap. "The electrons hopped between the gold stepping stones. The stones are so small, you can only get one electron on the stone at a time. Every electron is passing the same way, so the device is always stable."

Yap's team had made a transistor without a semiconductor. When sufficient voltage was applied, it switched to a conducting state. When the voltage was low or turned off, it reverted to its natural state as an insulator.

Furthermore, there was no "leakage": no electrons from the gold dots escaped into the insulating BNNTs, thus keeping the tunneling channel cool. In contrast, silicon is subject to leakage, which wastes energy in electronic devices and generates a lot of heat.

Other people have made transistors that exploit quantum tunneling, says Michigan Tech physicist John Jaszczak, who has developed the theoretical framework for Yap's experimental research. However, those tunneling devices have only worked in conditions that would discourage the typical cellphone user.

"They only operate at liquid-helium temperatures," said Jaszczak.

The secret to Yap's gold-and-nanotube device is its submicroscopic size: one micron long and about 20 nanometers wide. "The gold islands have to be on the order of nanometers across to control the electrons at room temperature," Jaszczak said. "If they are too big, too many electrons can flow." In this case, smaller is truly better: "Working with nanotubes and quantum dots gets you to the scale you want for electronic devices."

"Theoretically, these tunneling channels can be miniaturized into virtually zero dimension when the distance between electrodes is reduced to a small fraction of a micron," said Yap.

Yap has filed for a full international patent on the technology.

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New Light On Possible 'Fifth Force of Nature'

New Light On Possible 'Fifth Force of Nature'

  7:52:00 PM    Science Lover

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In a breakthrough for the field of particle physics, Professor of Physics Larry Hunter and colleagues at Amherst College and The University of Texas at Austin have established new limits on what scientists call "long-range spin-spin interactions" between atomic particles. These interactions have been proposed by theoretical physicists but have not yet been seen. Their observation would constitute the discovery of a "fifth force of nature" (in addition to the four known fundamental forces: gravity, weak, strong and electromagnetic) and would suggest the existence of new particles, beyond those presently described by the Standard Model of particle physics.

This picture depicts the long-range spin-spin interaction (blue wavy lines) in which the spin-sensitive detector on Earth’s surface interacts with geoelectrons (red dots) deep in Earth’s mantle. The arrows on the geoelectrons indicate their spin orientations, opposite that of Earth’s magnetic field lines (white arcs). (Credit: Illustration: Marc Airhart (University of Texas at Austin) and Steve Jacobsen (Northwestern University).)

The new limits were established by considering the interaction between the spins of laboratory fermions (electrons, neutrons and protons) and the spins of the electrons within Earth. To make this study possible, the authors created the first comprehensive map of electron polarization within Earth induced by the planet's geomagnetic field.

Hunter -- along with emeritus Amherst physics professor Joel Gordon; postdoctoral fellow Stephen Peck; student researcher Daniel Ang '15; and Jung-Fu "Afu" Lin, associate professor of geosciences at UT Austin -- co-authored a paper about their work that appears in this week's issue of the journal Science. The highly interdisciplinary research relies on geophysics, atomic physics, particle physics, mineral physics, solid-state physics and nuclear physics to reach its conclusions.

The paper describes how the team combined a model of Earth's interior with a precise map of the planet's geomagnetic field to produce a map of the magnitude and direction of electron spins throughout Earth. Their model was based in part on insights gained from Lin's studies of spin transitions at the high temperatures and pressures of Earth's interior.

Every fundamental particle (every electron, neutron and proton, to be specific), explained Hunter, has the intrinsic atomic property of "spin." Spin can be thought of as a vector -- an arrow that points in a particular direction. Like all matter, Earth and its mantle -- a thick geological layer sandwiched between the thin outer crust and the central core -- are made of atoms. The atoms are themselves made up of electrons, neutrons and protons that have spin. Earth's magnetic field causes some of the electrons in the mantle's minerals to become slightly spin-polarized, meaning the directions in which their spins point are no longer completely random, but have some net orientation.

Earlier experiments, including one in Hunter's laboratory, explored whether their laboratory spins prefer to point in a particular direction. "We know, for example, that a magnetic dipole has a lower energy when it is oriented parallel to the geomagnetic field and it lines up with this particular direction -- that is how a compass works," he explained. "Our experiments removed this magnetic interaction and looked to see if there might be some other interaction that would orient our experimental spins. One interpretation of this 'other' interaction is that it could be a long-range interaction between the spins in our apparatus, and the electron spins within the Earth, that have been aligned by the geomagnetic field. This is the long-range spin-spin interaction we are looking for."

So far, no experiment has been able to detect any such interaction. But in Hunter's paper, the researchers describe how they were able to infer that such so-called spin-spin forces, if they exist, must be incredibly weak -- as much as a million times weaker than the gravitational attraction between the particles. At this level, the experiments can constrain "torsion gravity" -- a proposed theoretical extension of Einstein's Theory of General Relativity. Given the high sensitivity of the technique Hunter and his team used, it may provide a useful path for future experiments that will refine the search for such a fifth force. If a long-range spin-spin force is found, it not only would revolutionize particle physics but might eventually provide geophysicists with a new tool that would allow them to directly study the spin-polarized electrons within Earth.

"If the long-range spin-spin interactions are discovered in future experiments, geoscientists can eventually use such information to reliably understand the geochemistry and geophysics of the planet's interior," said Lin.

Possible future discoveries aside, Hunter said that he was pleased that this particular project enabled him to work with Lin. "When I began investigating spin transitions in the mantle, all of the literature led to him," he explained. "I was thrilled that he was interested in the project and willing to sign on as a collaborator. He has been a good teacher and has had enormous patience with my ignorance about geophysics. It has been a very fruitful collaboration."

Lin had his own take: "The most rewarding and surprising thing about this project was realizing that particle physics could actually be used to study the deep Earth."

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Scientists Create Nanoscale Window to Biological World

Scientists Create Nanoscale Window to Biological World

  9:13:00 AM    Science Lover

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If the key to winning battles is knowing both your enemy and yourself, then scientists are now well on their way toward becoming the Sun Tzus of medicine by taking a giant step toward a priceless advantage -- the ability to see the soldiers in action on the battlefield.

A novel microfluidics platform allowed viewing of structural 
details of rotavirus double-layered particles; the 3-D graphic 
of the virus, in purple, was reconstructed from data gathered by 
the new technique. (Credit: Virginia Tech)

Investigators at the Virginia Tech Carilion Research Institute have invented a way to directly image biological structures at their most fundamental level and in their natural habitats. The technique is a major advancement toward the ultimate goal of imaging biological processes in action at the atomic level.

"It's sort of like the difference between seeing Han Solo frozen in carbonite and watching him walk around blasting stormtroopers," said Deborah Kelly, an assistant professor at the VTC Research Institute and a lead author on the paper describing the first successful test of the new technique. "Seeing viruses, for example, in action in their natural environment is invaluable."

The technique involves taking two silicon-nitride microchips with windows etched in their centers and pressing them together until only a 150-nanometer space between them remains. The researchers then fill this pocket with a liquid resembling the natural environment of the biological structure to be imaged, creating a microfluidic chamber.

Then, because free-floating structures yield images with poor resolution, the researchers coat the microchip's interior surface with a layer of natural biological tethers, such as antibodies, which naturally grab onto a virus and hold it in place.

In a recent study in Lab on a Chip, Kelly joined Sarah McDonald, also an assistant professor at the VTC Research Institute, to prove that the technique works. McDonald provided a pure sample of rotavirus double-layered particles for the study.

"What's missing in the field of structural biology right now is dynamics -- how things move in time," said McDonald. "Debbie is developing technologies to bridge that gap, because that's clearly the next big breakthrough that structural biology needs."

Rotavirus is the most common cause of severe diarrhea among infants and children. By the age of 5, nearly every child in the world has been infected at least once. And although the disease tends to be easily managed in the developed world, in developing countries rotavirus kills more than 450,000 children a year.

At the second step in the pathogen's life cycle, rotavirus sheds its outer layer, which allows it to enter a cell, and becomes what is called a double-layered particle. Once its second layer is exposed, the virus is ready to begin using the cell's own infrastructure to produce more viruses. It was the viral structure at this stage that the researchers imaged in the new study.

Kelly and McDonald coated the interior window of the microchip with antibodies to the virus. The antibodies, in turn, latched onto the rotaviruses that were injected into the microfluidic chamber and held them in place. The researchers then used a transmission electron microscope to image the prepared slide.

The technique worked perfectly.

The experiment gave results that resembled those achieved using traditional freezing methods to prepare rotavirus for electron microscopy, proving that the new technique can deliver accurate results.

"It's the first time scientists have imaged anything on this scale in liquid," said Kelly.

The next step is to continue to develop the technique with an eye toward imaging biological structures dynamically in action. Specifically, McDonald is looking to understand how rotavirus assembles, so as to better know and develop tools to combat this particular enemy of children's health.

The researchers said their ongoing collaboration is an example of the cross-disciplinary work that is becoming a hallmark of the VTC Research Institute.

"It's an ideal collaboration because Sarah provides a phenomenal model system by which we can develop new technologies to move the field of microstructural biology forward," said Kelly.

"It's very win-win," McDonald added. "While the virus is a great tool for Debbie to develop her techniques, her technology is critical for allowing me to understand how this deadly virus assembles and changes dynamically over time."

The paper "Visualizing viral assemblies in a nanoscale biosphere" was published online and will appear in a 2013 edition of Lab on a Chip.

The authors are Brian Gilmore, a research associate at the VTC Research Institute; Shannon Showalter, a research assistant at the VTC Research Institute; Madeline Dukes, an applications scientist at Protochips; Justin Tanner, a postdoctoral associate at the VTC Research Institute; Andrew Demmert, a student at the Virginia Tech Carilion School of Medicine; McDonald, in addition to her position at the VTC Research Institute, is an assistant professor of biomedical sciences and pathobiology in the Virginia-Maryland Regional College of Veterinary Medicine; and Kelly, in addition to her position at the VTC Research Institute, is an assistant professor of biological sciences in Virginia Tech's College of Science.

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A Wrinkle in Space-Time: Math Shows How Shockwaves Could Crinkle Space

A Wrinkle in Space-Time: Math Shows How Shockwaves Could Crinkle Space

  11:20:00 AM    Science Lover

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Mathematicians at UC Davis have come up with a new way to crinkle up the fabric of space-time -- at least in theory.

Illustration of twisted space-time around Earth. (Credit: NASA)

"We show that space-time cannot be locally flat at a point where two shock waves collide," said Blake Temple, professor of mathematics at UC Davis. "This is a new kind of singularity in general relativity."

The results are reported in two papers by Temple with graduate students Moritz Reintjes and Zeke Vogler, respectively, both published in the journal Proceedings of the Royal Society A.

Einstein's theory of general relativity explains gravity as a curvature in space-time. But the theory starts from the assumption that any local patch of space-time looks flat, Temple said.

A singularity is a patch of space-time that cannot be made to look flat in any coordinate system, Temple said. One example of a singularity is inside a black hole, where the curvature of space becomes extreme.

Temple and his collaborators study the mathematics of how shockwaves in a perfect fluid can affect the curvature of space-time in general relativity. In earlier work, Temple and collaborator Joel Smoller, Lamberto Cesari professor of mathematics at the University of Michigan, produced a model for the biggest shockwave of all, created from the Big Bang when the universe burst into existence.

A shockwave creates an abrupt change, or discontinuity, in the pressure and density of a fluid, and this creates a jump in the curvature. But it has been known since the 1960s that the jump in curvature created by a single shock wave is not enough to rule out the locally flat nature of space-time.

Vogler's doctoral work used mathematics to simulate two shockwaves colliding, while Reintjes followed up with an analysis of the equations that describe what happens when shockwaves cross. He found this created a new type of singularity, which he dubbed a "regularity singularity."

What is surprising is that something as mild as interacting waves could create something as extreme as a space-time singularity, Temple said.

Temple and his colleagues are investigating whether the steep gradients in the space-time fabric at a regularity singularity could create any effects that are measurable in the real world. For example, they wonder whether they might produce gravity waves, Temple said. General relativity predicts that these are produced, for example, by the collision of massive objects like black holes, but they have not yet been observed in nature. Regularity singularities could also be formed within stars as shockwaves pass within them, the researchers theorize.

Reintjes, now a postdoctoral scholar at the University of Regensburg, Germany presented the work at the International Congress on Hyperbolic Problems in Padua, in June.

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Quantum Computers Move Closer to Reality, Thanks to Highly Enriched and Highly Purified Silicon

Quantum Computers Move Closer to Reality, Thanks to Highly Enriched and Highly Purified Silicon

  2:57:00 PM    Science Lover

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The quantum computer is a futuristic machine that could operate at speeds even more mind-boggling than the world's fastest super-computers.

SFU physicist Mike Thewalt and grad student Kamyar 
Saeedi with a sample of highly isotopically enriched silicon - 
its unique properties could advance quantum computing. 
(Credit: Image courtesy of Simon Fraser University)

Research involving physicist Mike Thewalt of Simon Fraser University offers a new step towards making quantum computing a reality, through the unique properties of highly enriched and highly purified silicon.

Quantum computers right now exist pretty much in physicists' concepts, and theoretical research. There are some basic quantum computers in existence, but nobody yet can build a truly practical one -- or really knows how.

Such computers will harness the powers of atoms and sub-atomic particles (ions, photons, electrons) to perform memory and processing tasks, thanks to strange sub-atomic properties.

What Thewalt and colleagues at Oxford University and in Germany have found is that their special silicon allows processes to take place and be observed in a solid state that scientists used to think required a near-perfect vacuum.

And, using this 28Si they have extended to three minutes -- from a matter of seconds -- the time in which scientists can manipulate, observe and measure the processes.

"It's by far a record in solid-state systems," Thewalt says. "If you'd asked people a few years ago if this was possible, they'd have said no. It opens new ways of using solid-state semi-conductors such as silicon as a base for quantum computing.

"You can start to do things that people thought you could only do in a vacuum. What we have found, and what wasn't anticipated, are the sharp spectral lines (optical qualities) in the 28Silicon we have been testing. It's so pure, and so perfect. There's no other material like it."

But the world is still a long way from practical quantum computers, he notes.

Quantum computing is a concept that challenges everything we know or understand about today's computers.

Your desktop or laptop computer processes "bits" of information. The bit is a fundamental unit of information, seen by your computer has having a value of either "1" or "0."

That last paragraph, when written in Word, contains 181 characters including spaces. In your home computer, that simple paragraph is processed as a string of some 1,448 "1"s and "0"s.

But in the quantum computer, the "quantum bit" (also known as a "qubit") can be both a "1" and a "0" -- and all values between 0 and 1 -- at the same time.

Says Thewalt: "A classical 1/0 bit can be thought of as a person being either at the North or South Pole, whereas a qubit can be anywhere on the surface of the globe -- its actual state is described by two parameters similar to latitude and longitude."

Make a practical quantum computer with enough qubits available and it could complete in minutes calculations that would take today's super-computers years, and your laptop perhaps millions of years.

The work by Thewalt and his fellow researchers opens up yet another avenue of research and application that may, in time, lead to practical breakthroughs in quantum computing.

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Searching for Spin Liquids: Much-Sought Exotic Quantum State of Matter Can Exist

Searching for Spin Liquids: Much-Sought Exotic Quantum State of Matter Can Exist

  12:33:00 AM    Science Lover

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The world economy is becoming ever more reliant on high tech electronics such as computers featuring fingernail-sized microprocessors crammed with billions of transistors. For progress to continue, for Moore's Law -- according to which the number of computer components crammed onto microchips doubles every two years, even as the size and cost of components halves -- to continue, new materials and new phenomena need to be discovered.

Diagram depicting anti-ferromagnetic order (upper) compared to a spin liquid phase (lower). In an anti-ferromagnet, the spins are anti-aligned. A spin liquid has no order and the spins can be viewed as bobbing about like water molecules in liquid water. (Credit: E. Edwards)

Furthermore, as the sizes of electronic components shrink, soon down to the size of single atoms or molecules, quantum interactions become ever more important. Consequently, enhanced knowledge and exploitation of quantum effects is essential. Researchers at the Joint Quantum Institute (JQI) in College Park, Maryland, operated by the University of Maryland and the National Institute of Standards and Technology (NIST), and at Georgetown University have uncovered evidence for a long-sought-after quantum state of matter, a spin liquid.

The research was performed by JQI postdoctoral scientists Christopher Varney and Kai Sun, JQI Fellow Victor Galitski, and Marcos Rigol of Georgetown University. The results appear in an editor-recommended article in the 12 August issue of the journal Physical Review Letters.

You can't pour a spin liquid into a glass. It's not a material at all, at least not a material you can touch. It is more like a kind of magnetic disorder within an ordered array of atoms. Nevertheless, it has many physicists excited.

To understand this exotic state of matter, first consider the concept of spin, which is at the heart of all magnetic phenomena. For instance, a refrigerator magnet, at the microscopic level, consists of trillions of trillions of iron atoms all lined up. Each of these atoms can be thought of loosely as a tiny spinning ball. The orientation of that spin is what makes the atom into a tiny magnet. The refrigerator magnet is an example of a ferromagnet, the ferro part coming from the Latin word for iron. In a ferromagnet, all the atomic spins are lined up in the same way, producing a large cooperative magnetic effect.

Important though they may be, ferromagnets aren't the only kind of material where magnetic interactions between spins are critical. In anti-ferromagnets, for instance, the neighboring spins are driven to be anti-aligned. That is, the orientations of the spins alternate up and down (see top picture in figure). The accumulative magnetic effect of all these up and down spins is that the material has no net magnetism. The high-temperature superconducting materials discovered in the 1980s are an important example of an anti-ferromagnetic structure.

More complicated and potentially interesting magnetic arrangements are possible, which may lead to a quantum spin liquid. Imagine an equilateral triangle, with an atom (spin) at each corner. Anti-ferromagnetism in such a geometry would meet with difficulties. Suppose that one spin points up while a second spin points down. So far, so good. But what spin orientation can the third atom take? It can't simultaneously anti-align with both of the other atoms in the triangle. Physicists employ the word "frustration" to describe this baffling condition where all demands cannot be satisfied.

In everyday life frustration is, well, frustrating, and actually this condition is found throughout nature, from magnetism to neural networks. Furthermore, understanding the different manifestations of a collection of magnetically interacting spins might help in designing new types of electronic circuitry.

One compromise that a frustrated spin system makes is to simultaneously exist in many spin orientations. In a quantum system, this simultaneous existence, or superposition, is allowed.

Here's where the JQI researchers have tried something new. They have studied what happens when frustration occurs in materials with a hexagonal (six sided) unit cell lattice.

What these atoms do is interact via their respective spins. The strength of the interaction between nearest neighbor (NN) atoms is denoted by the parameter J1. Similarly, the force between next nearest neighbors (NNN) -- that is, pairs of atoms that have at least one intervening atom between them -- is denoted by J2. Letting this batch of atoms interact among themselves, even on a pretend lattice as small as this, entails an immense calculation. Varney and his colleagues have calculated what happens in an array of hexagons consisting of 30 sites where the spins are free to swing about in a two-dimensional plane (this kind of approach is called an XY model).



Christopher Varney, who has appointments at Maryland and Georgetown, said that the interactions of atoms can be represented by a matrix (essentially a two-dimensional spreadsheet) with 155 million entries on each side. This huge number corresponds to the different spin configurations that can occur on this honeycomb-structured material.

What the researchers found were a "kaleidoscope" of phases, which represent the lowest-energy states that are allowed given the magnetic interactions. Just as water can exist in different phases -- steam, liquid, and ice -- as the temperature is changed, so here a change in the strengths of the interactions among the spins (the J1 and J2 parameters) results in different phases. For example, one simple solution is an antiferromagnet (upper picture in figure).

But one phase turns out to be a true quantum spin liquid having no order at all. When J2 is between about 21% and 36% of the value of J1, frustration coaxes the spins into disorder; the entire sample co-exists in millions of quantum states simultaneously.

It's difficult for the human mind to picture a tiny two-dimensional material in so many states at the same time. JQI fellow, Victor Galitski, suggests that one shouldn't think of the spins as residing at the original atomic sites but rather as free ranging particle-like entities dubbed "spinons." These spinons bob about, just as water molecules bob about in liquid water (see lower picture in figure). Hence the name quantum spin liquid.

Another reason for using the word liquid, Galitski says, is this 'bobbing about' is analogous to what happens inside a metal. There, the outer electrons of most atoms tend to leave their home atoms and drift through the metal sample as if they constituted a fluid, called a "Fermi liquid."

Electrons in a metal are able to drift since it takes only an infinitesimal amount of energy to put them into motion. The same is true for the fluctuating spins in the hexagonal model studied by the JQI scientists. Indeed, their spin model assumes a temperature of absolute zero, where quantum effects abound.

Writing in an essay that accompanied the article in Physical Review Letters, Tameem Albash and Stephan Haas, scientists at the University of Southern California, say that the JQI/Georgetown team "present a convincing example" of the new spin liquid state.

How can this new frustration calculation be tested? The experimental verification of the spin liquid state in a 2-dimenstional hexagonal lattice, Albash and Haas suggest, "will probably be tested using cold atoms trapped in optical lattices. In the past few years, this technology has become a reliable tool to emulate quantum many body lattice systems with tunable interactions." Indeed the authors propose such an experiment.

What would such a spin liquid material be good for? It's too early to tell. But some speculations include the idea that these materials could support some exotic kind of superconductivity or would organize particle-like entities that possessed fractional electric charge.

"Kaleidoscope of Exotic Quantum Phases in a Frustrated XY Model" by Christopher N. Varney, Kai Sun, Victor Galitski, and Marcos Rigol, Physical Review Letters, 107, 077201, (12 August 2011).

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Artificial leaves make fuel from sunlight

Artificial leaves make fuel from sunlight

  10:06:00 AM    Science Lover

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Two teams of researchers in the US have taken important steps towards the creation of commercially viable "artificial leaf" – a hypothetical device that can turn sunlight into electrical energy or fuel by mimicking some aspects of photosynthesis.

Daniel Nocera in his lab at the
Massachusetts Institute of Technology.
(Courtesy: Donna Coveney/MIT)

Earlier this year, the chemist Daniel Nocera at the Massachusetts Institute of Technology (MIT) announced artificial-leaf prototypes at the annual meeting of the American Chemical Society in California. Now, working with two different teams of researchers, he has published two papers on different devices that represent progress towards effective and commercially viable versions of the artificial leaf.

Here comes the Sun

Both teams made their devices from silicon wafers that are coated with catalytic metals and protective layers. The prototype solar cells are about the size of a credit card and can capture sunlight and then use the energy to split water into its constituent oxygen and hydrogen. This is different to conventional photovoltaic cells, which convert light directly into electricity. With these new devices, the ultimate plan is to recombine the two gases in an integrated fuel cell, thus converting the chemical energy to electrical energy. Producing fuel rather than electricity has the advantage that the fuel can be easily stored until it is needed.

Both artificial leaves use a silicon n–p junction: a bilayer of n-type and p-type silicon. An incident photon is absorbed to create an electron–hole pair in the semiconductor. The electrons migrate to the n-side and the holes to the p-side. The holes then drive the splitting of water in a process mediated by the outermost layer of the cell, which is a photocatalyst. Unlike some of the exotic photocatalysts used in earlier devices, the catalyst in these new devices are made of cobalt phosphate, which is an abundant and cheap material.

The main challenge in creating both devices was how to prevent the silicon from reacting with the water. The two teams took different approaches to the problem. One group led by electrical engineer Vladimir Bulovic used the catalyst itself as a protective layer, binding a thin film of pure cobalt firmly to the silicon before converting it to the phosphate form. The other team, led by mechanical engineer Tonio Buonassisi, used a thin film of conductive indium tin oxide in front of the p-type silicon as the protective layer.

Bubbles needed



Buonassisi and colleagues connected two of their cells in series and managed to split water with a solar-to-oxygen conversion efficiency of 0.25%. While this does not sound like much, the efficiency of photosynthesis is only a few per cent. However, the cells make hydrogen ions, and turning this into gas could add considerable cost to the device. "Platinum electrodes are good catalysts for reducing hydrogen ions to hydrogen gas", says Devens Gust of Arizona State University, who was not involved in the research. "However, the rarity of platinum limits its usefulness."

Gust describes the MIT work as "very important in that it demonstrates a workable, inexpensive water-oxidation catalyst". However, he says that the technology is entering a crowded market, pointing out that there is already a production technology for solar fuel that is "pretty much ready to go now". This system uses photovoltaic cells coupled to an electrolyzer that splits water into oxygen and hydrogen. "Electrolyzer efficiencies can be as high as 70–80%, and currently available photovoltaic efficiencies are as high as 15–20%", he points out. "None of the artificial photosynthetic systems can compete with this at the moment."

The MIT technology must also compete with other water-splitting systems based on silicon solar cells coated with photocatalysts. These have been in development since at least 1998 and some have reached solar-to-hydrogen conversion efficiencies of 7% or better.

"Challenges remain"

One of these cells was developed at California Institute of Technology by Nathan Lewis and Harry Atwater. Atwater told physicsworld.com that "Nocera's work is interesting, but many challenges remain." It is not clear, for example, whether the catalyst and devices remain stable beyond the few days of operation for which they have so far been tested. Atwater also thinks there is room for improvement in the materials themselves.

Gust agrees, pointing out that while cobalt and other catalysts based on common materials are promising, researchers have yet to develop an inexpensive catalyst that works near the thermodynamic potential for water oxidation/reduction. This property would help to optimize the performance of an artificial-leaf system. Nocera hopes to have a fully working device within about three years, and he has formed a company called SunCatalytix to develop it.

The work by Bulovic's group is published in Energy & Environmental Science, while the research by Buonassisi's group is outlined in Proceedings of the National Academy of Sciences USA.

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Breakthrough in Quantum Computing: Researchers Develop System That Resists 'Quantum Bug'

Breakthrough in Quantum Computing: Researchers Develop System That Resists 'Quantum Bug'

  10:36:00 PM    Science Lover

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Scientists have taken the next major step toward quantum computing, which will use quantum mechanics to revolutionize the way information is processed.

Quantum computing uses quantum bits, or qubits, to 
encode information. (Credit: © Anterovium / Fotolia)

Quantum computers will capitalize on the mind-bending properties of quantum particles to perform complex calculations that are impossible for today's traditional computers.

Using high magnetic fields, Susumu Takahashi, assistant professor in the USC Dornsife College of Letters, Arts and Sciences, and his colleagues managed to suppress decoherence, which is one of the key stumbling blocks in quantum computing.

"High magnetic fields reduce the level of the noises in the surroundings, so they can constrain the decoherence very efficiently," Takahashi said. Decoherence has been described as a "quantum bug" that destroys fundamental properties that quantum computers would rely on.

This research will appear in the online version of Nature magazine on June 20.

Quantum computing uses quantum bits, or qubits, to encode information in the form of ones and zeros. Unlike a traditional computer that uses traditional bits, a quantum computer takes advantage of the fact seemingly impossible fact that qubits can exist in multiple states at the same time, which is called "superposition."

While can a bit can represent either a one or a zero, a qubit can represent a one and a zero at the same time due to superposition. This allows for simultaneous processing of calculations in a truly parallel system, skyrocketing computing ability.

Though the concepts underpinning quantum computing are not new, problems such as decoherence have hindered the construction of a fully functioning quantum computer.

Think of decoherence as a form of noise or interference, knocking a quantum particle out of superposition -- robbing it of that special property that makes it so useful. If a quantum computer relies on a quantum particle's ability to be both here and there, then decoherence is the frustrating phenomenon that causes a quantum particle to be either here or there.

The researchers calculated all sources of decoherence in his experiment as a function of temperature, magnetic field, and by nuclear isotopic concentrations, and suggested the optimum condition to operate qubits, reducing decoherence by approximately 1,000 times.

Qubits in his experiment lasted about 500 microseconds at the optimum condition -- ages, relatively speaking.

Decoherence in qubit systems falls into two general categories. One is an intrinsic decoherence caused by constituents in the qubit system, and the other is an extrinsic decoherence caused by imperfections of the system, for example, impurities and defects.

In their study, Takahashi and his colleagues investigated single crystals of molecular magnets. Because of their purity, molecular eliminate the extrinsic decoherence, allowing researchers to calculate intrinsic decoherence precisely.

"For the first time we've been able to predict and control all the environmental decoherence mechanisms in a very complex system -- in this case a large magnetic molecule," said Phil Stamp, UBC professor of physics and astronomy and director of the Pacific Institute of Theoretical Physics.

Using crystalline molecular magnets allowed researchers to build qubits out of multiple quantum particles, rather than a single quantum object -- the way most proto-quantum computers are built at the moment.

"This will obviously increase signals from the qubit drastically, so the detection of the qubit in the molecular magnets is much easier," Takahashi said.

Takahashi conducted his research as a project scientist in the Institute of Terahertz Science and Technology and Department of Physics at the University of California Santa Barbara and analyzed the data while at UCSB and USC. Takahashi has been in the USC Dornsife College since 2010.

Research for the article was performed in collaboration with Phil Stamp and Igor Tupitsyn of the University of British Columbia, Johan van Tol of Florida State University, and David Hendrickson of UC San Diego.

This work was supported by the National Science Foundation, the W. M. Keck Foundation, the Pacific Institute of Theoretical Physics at UBC, by the Natural Sciences and Engineering Research Council of Canada, the Canadian Institute for Advanced Research and the USC startup funds.

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Physicists take steps toward delivering quantum information to the home

Physicists take steps toward delivering quantum information to the home

  10:36:00 AM    Science Lover

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Today, fiber optics technology transports information in the form of classical data to homes and businesses. But researchers are currently working on ways to combine quantum data with the classical data in fiber optics networks in order to increase security. In a new study, scientists have shown how quantum and classical data can be interlaced in a real-world fiber optics network, taking a step toward distributing quantum information to the home, and with it a quantum internet.

A tree network is often used to distribute classical data to homes via fiber optics. Researchers are working on co-propagating quantum information with the classical data to improve security. Image copyright: Iris Choi, et al. ©2011 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

The physicists, Iris Choi, Robert J. Young, and Paul D. Townsend, from the Tyndall National Institute at the University College Cork in Cork, Ireland, have published their study on combining quantum and classical signals in a recent issue of the New Journal of Physics. While the feasibility of transferring qubits on modern fiber-to-the-home (FTTH) networks has previously been demonstrated, this is the first time that researchers have investigated how the operation would work in a real-world network.

“I believe that our work constitutes the first really hard-nosed, pragmatic attempt to address the question of whether quantum key distribution (QKD) can work on a real fiber-to-the-home (FTTH) network,” Townsend told PhysOrg.com. “The new scheme that we have developed and tested demonstrates that the answer is ‘yes it can.’ I say pragmatic and hard-nosed because we have taken a widely deployed classical FTTH system and have adapted QKD to interwork with it, leaving the design of the classical part of the system essentially unchanged. The alternative approach, sometimes taken in QKD research, is to leave out the classical system completely or to adapt it to work with the QKD. In our view this is not very practical for cost reasons.”

The biggest challenge in transferring qubits in real-world networks is overcoming the crosstalk between the classical and quantum channels. Crosstalk is induced by spontaneous Raman scattering of photons in the optical fiber. Since the classical channels involve strong laser pulses while the quantum information is carried by single photons, the crosstalk primarily affects the quantum channel, making the error rate so high that the quantum channel is unable to operate.



Previous research has shown that the Raman noise level can be reduced by optical filtering, although this technique is too expensive for practical use. So Choi, Young, and Townsend have developed and demonstrated a novel noise suppression scheme that involves creating gaps in the scattering, and sending quantum data in these gaps.

First, the researchers chose a configuration that used two different wavelengths for transmitting the quantum and classical channels. In this configuration, only the Raman-scattered light in the “upstream” channel (going away from a user’s house) can generate crosstalk for that user. Then, the researchers identified quiet periods between the bursts of noise generated by Raman scattering in the upstream channel. Using a time and wavelength-multiplexing scheme, the researchers demonstrated that quantum data generated by a quantum key distribution (QKD) scheme can be transmitted during these quiet periods with high fidelity.

While building a purely quantum network could avoid the problem of crosstalk altogether, the researchers explain that combining quantum channels with classical channels is by far the more practical option.

“I see this as an absolute requirement – a ‘must have,’ Townsend said. “That’s because optical fiber network infrastructure is enormously expensive to deploy, so it must last for a long time – perhaps 25 years or more – and be able to support a wide range of current and future, yet to be defined, systems and services. So it is extremely unlikely that an operator would ever deploy a network, or even dedicate fibers within an existing network, purely for quantum communications – it’s just too expensive to do so. Consequently, we have to develop techniques that enable classical and quantum channels to work together on the same network if we want quantum communication systems to become a practical reality.”

By demonstrating that both quantum and classical information can be transmitted on a single optical fiber network in a way that satisfies real-world requirements, the researchers hope to bring quantum information technology one step closer to commercial applications.

“As we have demonstrated, in principle the technology to do this is available now,” Townsend. “However, in reality further research is likely to be required to reduce the cost and improve the performance of certain key parts of the system such as the single photon detectors, before widespread applications emerge. In general, the ‘value proposition’ for QKD on FTTH and other networks is under intensive discussion today, but at the moment no clear consensus has emerged concerning if and when it might be adopted to replace classical encryption techniques. However, as demonstrated by this research, the QKD field is not standing still and systems are continuing to evolve to become more practical, improving the potential for adoption of the technology in the future.”

More information: Iris Choi, et al. “Quantum information to the home.” New Journal of Physics 13 (2011) 063039 DOI:10.1088/1367-2630/13/6/063039

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Camera fits on the head of a pin

Camera fits on the head of a pin

  9:44:00 AM    Science Lover

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While tiny cameras are now found in just about every mobile phone and laptop, a camera that can fit on the head of a pin and that costs just a few pennies takes miniaturization to a new level. Researchers in the US have developed a micro-camera with no lens, no focusing optics and no moving parts. Just 500 µm across and 10 µm thick, the device could have a number of applications in areas that range from surgery to robotics and imaging.

The planar Fourier capture array obtains images via an array of angle-sensitive pixels. Above are reconstructed images of the Mona Lisa and simpler images such as a stripe and a spot. (Courtesy: Alyosha Molnar Lab/Cornell University)

The micro-camera was developed by postdoctoral associate Patrick Gill and colleagues at Cornell University's Alyosha Molnar Lab in New York. The camera can resolve images about 20 pixels across, so while it will not be used to obtain high resolution images, its size offers immense scientific and technological possibilities. "It's not going to be a camera with which people take family portraits, but there are a lot of applications out there that require just a little bit of dim vision," says Gill.

Traditional cameras use focusing optics such as lenses or mirrors, which map incoming light based on its incident angle to a sensor plane made up of photosensitive pixels. But this means that they are bulky, have off-chip optics and require precision manufacturing. To avoid these complications, the Cornell team uses an array of angle sensitive pixels (ASP), each of which is composed of a photodiode under two metal gratings formed using standard semiconductor-processing techniques. Light incident on the upper grating produces an interference pattern that in turn interacts with the second grating. Light is either passed or blocked depending on the alignment of the interference pattern and the second grating. As the alignment is sensitive to changes in the incident angle of the incoming light, the net effect is that the light passed by an ASP depends sinusoidally on the incident angle.

Picket fences

Gill says that a simple explanation of how the light passes through both gratings is the analogy of driving down a street and looking at two aligned fences on the same side of the road. "We have made each pixel of our camera angle sensitive. Consider two picket fences, one behind the other. They have slats and gaps at the same spacing. Looking through the fences, at some angles the gaps of the two fences align, while at other angles the slats of one align with the gaps of the other. The overall effect is that the amount of light coming through the fences is a sinusoidal function of the incident angle. The creation of sinusoidal patterns as a result of two periodic apertures is known as the Moiré effect and that is basically what happens with our gratings too," explains Gill.



Then, using a Fourier transformation technique commonly used in image processing, each pixel provides one component of the Fourier transform of the image being detected and the various components are then assembled into an image. The researchers call their camera a planar Fourier capture array (PFCA) and while they have only produced an initial prototype of the device, Gill feels that it worked better than expected.

A photograph of the whole array of the micro-camera; each pixel has a unique set of optical gratings that radiate from the centre. (Courtesy: Alyosha Molnar Lab/Cornell University)

"What is exciting about the PFCA is that it does not require any special manufacturing at all, what we have used is a commercially produced semiconductor. I honestly feel that the uses of the PFCA are limited only by one's creativity, especially considering how cheap it is," claims Gill.

In fact, Gill says that he himself became interested in making this micro-camera because as he is a neuroscientist he was looking for ways to introduce an optical system into the brain without causing much damage. "The array could be fashioned into a probe for imaging neurons that have been modified to glow when they are active, which would mean that we could study how the brain's neurons fire under certain stimuli. And because of its microscopic nature, the damage would be minimal," says Gill.
Smaller and better

Although the current camera is already microscopic, being produced using a 180 nm CMOS process, Gill believes a 32 nm process could be used, which could mean a factor of two improvement in the resolution. "There was a fair amount of redundancy in our current camera as it is a prototype. Now, after testing the initial design, we know how to improve the resolution and make it more efficient. We could achieve a 40 × 40 pixel resolution," says Gill. The camera could feature as a component in any cheap electronic system – in devices that detect the angle of the Sun or a micro-robot that requires a simple visual system to navigate.

The research has been accepted for publication in Optics Letters.

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