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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Small in Size, Big On Power: New Microbatteries the Most Powerful Yet

Small in Size, Big On Power: New Microbatteries the Most Powerful Yet

  9:32:00 AM    Science Lover

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Though they be but little, they are fierce. The most powerful batteries on the planet are only a few millimeters in size, yet they pack such a punch that a driver could use a cellphone powered by these batteries to jump-start a dead car battery -- and then recharge the phone in the blink of an eye. 

The graphic illustrates a high power battery technology from the University of Illinois. Ions flow between three-dimensional micro-electrodes in a lithium ion battery. (Credit: Image courtesy of the Beckman Institute for Advanced Science and Technology)

Developed by researchers at the University of Illinois at Urbana-Champaign, the new microbatteries out-power even the best supercapacitors and could drive new applications in radio communications and compact electronics.

Led by William P. King, the Bliss Professor of mechanical science and engineering, the researchers published their results in the April 16 issue of Nature Communications.

"This is a whole new way to think about batteries," King said. "A battery can deliver far more power than anybody ever thought. In recent decades, electronics have gotten small. The thinking parts of computers have gotten small. And the battery has lagged far behind. This is a microtechnology that could change all of that. Now the power source is as high-performance as the rest of it."

With currently available power sources, users have had to choose between power and energy. For applications that need a lot of power, like broadcasting a radio signal over a long distance, capacitors can release energy very quickly but can only store a small amount. For applications that need a lot of energy, like playing a radio for a long time, fuel cells and batteries can hold a lot of energy but release it or recharge slowly.

"There's a sacrifice," said James Pikul, a graduate student and first author of the paper. "If you want high energy you can't get high power; if you want high power it's very difficult to get high energy. But for very interesting applications, especially modern applications, you really need both. That's what our batteries are starting to do. We're really pushing into an area in the energy storage design space that is not currently available with technologies today."

The new microbatteries offer both power and energy, and by tweaking the structure a bit, the researchers can tune them over a wide range on the power-versus-energy scale.

The batteries owe their high performance to their internal three-dimensional microstructure. Batteries have two key components: the anode (minus side) and cathode (plus side). Building on a novel fast-charging cathode design by materials science and engineering professor Paul Braun's group, King and Pikul developed a matching anode and then developed a new way to integrate the two components at the microscale to make a complete battery with superior performance.

With so much power, the batteries could enable sensors or radio signals that broadcast 30 times farther, or devices 30 times smaller. The batteries are rechargeable and can charge 1,000 times faster than competing technologies -- imagine juicing up a credit-card-thin phone in less than a second. In addition to consumer electronics, medical devices, lasers, sensors and other applications could see leaps forward in technology with such power sources available.

"Any kind of electronic device is limited by the size of the battery -- until now," King said. "Consider personal medical devices and implants, where the battery is an enormous brick, and it's connected to itty-bitty electronics and tiny wires. Now the battery is also tiny."

Now, the researchers are working on integrating their batteries with other electronics components, as well as manufacturability at low cost.

"Now we can think outside of the box," Pikul said. "It's a new enabling technology. It's not a progressive improvement over previous technologies; it breaks the normal paradigms of energy sources. It's allowing us to do different, new things."

The National Science Foundation and the Air Force Office of Scientific Research supported this work. King also is affiliated with the Beckman Institute for Advanced Science and Technology; the Frederick Seitz Materials Research Laboratory; the Micro and Nanotechnology Laboratory; and the department of electrical and computer engineering at the U. of I.

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Self-Assembling Nanocubes for Lenses

Self-Assembling Nanocubes for Lenses

  8:39:00 PM    Science Lover

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Researchers at the University of California, San Diego Jacobs School of Engineering have developed a technique that enables metallic nanocrystals to self-assemble into larger, complex materials for next-generation antennas and lenses. The metal nanocrystals are cube-shaped and, like bricks or Tetris blocks, spontaneously organize themselves into larger-scale structures with precise orientations relative to one another.

UC San Diego nanoengineers have developed a 
technique that enables silver nanocubes to 
self-assemble into larger-scale structures for use in 
new optical chemical and biological sensors, and 
optical circuitry. (Credit: Image courtesy of 
University of California - San Diego)

Their findings were published online June 10 in the journal Nature Nanotechnology.

This research is in the new field of nanoplasmonics, where researchers are developing materials that can manipulate light using structures that are smaller than the wavelength of light itself. The nanocubes used in this study were less than 0.1 microns; by comparison, the breadth of a human hair is 100 microns. Precise orientation is necessary so that the cubes can confine light (for a nanoscale antenna) or focus light (for a nanoscale lens) at different wavelengths.

"Our findings could have important implications in developing new optical chemical and biological sensors, where light interacts with molecules, and in optical circuitry, where light can be used to deliver information," said Andrea Tao, a professor in the Department of NanoEngineering at the Jacobs School. Tao collaborated with nanoengineering professor Gaurav Arya and post-doctoral researcher Bo Gao.

To construct objects like antennas and lenses, Tao's team is using chemically synthesized metal nanocrystals. The nanocrystals can be synthesized into different shapes to build these structures; in this study, Tao's team created tiny cubes composed of crystalline silver that can confine light when organized into multi-particle groupings. Confining light into ultra-small volumes could allow optical sensors that are extremely sensitive and that could allow researchers to monitor how a single molecule moves, reacts, and changes with time.

To control how the cubes organize, Tao and her colleagues developed a method to graft polymer chains to the silver cube surfaces that modify how the cubes interact with each other. Normally when objects like cubes stack, they pack side-by-side like Tetris blocks. Using simulations, Tao's team predicted that placing short polymer chains on the cube surface would cause them to stack normally, while placing long polymer chains would cause the cubes to stack edge-to-edge. The approach is simple, robust, and versatile.

In demonstrating their technique, the researchers created macroscopic films of nanocubes with these two different orientations and showed that the films reflected and transmitted different wavelengths of light.

The research was supported by the National Science Foundation, the Hellman Foundation, and Jacobs School of Engineering at UC San Diego.

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Researchers Watch Tiny Living Machines Self-Assemble

Researchers Watch Tiny Living Machines Self-Assemble

  1:05:00 PM    Science Lover

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Enabling bioengineers to design new molecular machines for nanotechnology applications is one of the possible outcomes of a study by University of Montreal researchers that was published in Nature Structural and Molecular Biology June 10. The scientists have developed a new approach to visualize how proteins assemble, which may also significantly aid our understanding of diseases such as Alzheimer's and Parkinson's, which are caused by errors in assembly.

Vallée-Bélisle and Michnick have developed a new 
approach to visualize how proteins assemble, which may 
also significantly aid our understanding of diseases such 
as Alzheimer’s and Parkinson’s, which are caused by errors 
in assembly. Here shown are two different assembly stages 
(purple and red) of the protein ubiquitin and the fluorescent 
probe used to visualize these stage (tryptophan: see yellow).

"In order to survive, all creatures, from bacteria to humans, monitor and transform their environments using small protein nanomachines made of thousands of atoms," explained the senior author of the study, Prof. Stephen Michnick of the university's department of biochemistry. "For example, in our sinuses, there are complex receptor proteins that are activated in the presence of different odor molecules. Some of those scents warn us of danger; others tell us that food is nearby." Proteins are made of long linear chains of amino acids, which have evolved over millions of years to self-assemble extremely rapidly -- often within thousandths of a split second -- into a working nanomachine. "One of the main challenges for biochemists is to understand how these linear chains assemble into their correct structure given an astronomically large number of other possible forms," Michnick said.

"To understand how a protein goes from a linear chain to a unique assembled structure, we need to capture snapshots of its shape at each stage of assembly said Dr. Alexis Vallée-Bélisle, first author of the study. "The problem is that each step exists for a fleetingly short time and no available technique enables us to obtain precise structural information on these states within such a small time frame. We developed a strategy to monitor protein assembly by integrating fluorescent probes throughout the linear protein chain so that we could detect the structure of each stage of protein assembly, step by step to its final structure."

The protein assembly process is not the end of its journey, as a protein can change, through chemical modifications or with age, to take on different forms and functions. "Understanding how a protein goes from being one thing to becoming another is the first step towards understanding and designing protein nanomachines for biotechnologies such as medical and environmental diagnostic sensors, drug synthesis of delivery," Vallée-Bélisle said.

This research was supported by the Natural Sciences and Engineering Research Council of Canada and Le fond de recherché du Québec, Nature et Technologie. The article, "Visualizing transient protein folding intermediates by tryptophan scanning mutagenesis," published in Nature Structural & Molecular Biology, was coauthored by Alexis Vallée-Bélisle and Stephen W. Michnick of the Département de Biochimie de l'Université de Montréal. The University of Montreal is known officially as Université de Montréal.

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Replacing Electricity With Light: First Physical 'Metatronic' Circuit Created

Replacing Electricity With Light: First Physical 'Metatronic' Circuit Created

  8:15:00 PM    Science Lover

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The technological world of the 21^st century owes a tremendous amount to advances in electrical engineering, specifically, the ability to finely control the flow of electrical charges using increasingly small and complicated circuits. And while those electrical advances continue to race ahead, researchers at the University of Pennsylvania are pushing circuitry forward in a different way, by replacing electricity with light.

Figure A. When the plane of the electric field is
in line with the nanorods the circuit is wired in
parallel. Figure B. When the plane of the electric
field crosses both the nanorods and the gaps the
circuit is wired in series. (Credit: Image courtesy
of University of Pennsylvania)

"Looking at the success of electronics over the last century, I have always wondered why we should be limited to electric current in making circuits," said Nader Engheta, professor in the electrical and systems engineering department of Penn's School of Engineering and Applied Science. "If we moved to shorter wavelengths in the electromagnetic spectrum -- like light -- we could make things smaller, faster and more efficient."

Different arrangements and combinations of electronic circuits have different functions, ranging from simple light switches to complex supercomputers. These circuits are in turn built of different arrangements of circuit elements, like resistors, inductors and capacitors, which manipulate the flow of electrons in a circuit in mathematically precise ways. And because both electric circuits and optics follow Maxwell's equations -- the fundamental formulas that describe the behavior of electromagnetic fields -- Engheta's dream of building circuits with light wasn't just the stuff of imagination. In 2005, he and his students published a theoretical paper outlining how optical circuit elements could work.

Now, he and his group at Penn have made this dream a reality, creating the first physical demonstration of "lumped" optical circuit elements. This represents a milestone in a nascent field of science and engineering Engheta has dubbed "metatronics."

Engheta's research, which was conducted with members of his group in the electrical and systems engineering department, Yong Sun, Brian Edwards and Andrea Alù, was published in the journal Nature Materials.

In electronics, the "lumped" designation refers to elements that can be treated as a black box, something that turns a given input to a perfectly predictable output without an engineer having to worry about what exactly is going on inside the element every time he or she is designing a circuit.

"Optics has always had its own analogs of elements, things like lenses, waveguides and gratings," Engheta said, "but they were never lumped. Those elements are all much larger than the wavelength of light because that's all that could be easily built in the old days. For electronics, the lumped circuit elements were always much smaller than the wavelength of operation, which is in the radio or microwave frequency range."

Nanotechnology has now opened that possibility for lumped optical circuit elements, allowing construction of structures that have dimensions measured in nanometers. In this experiment's case, the structure was comb-like arrays of rectangular nanorods made of silicon nitrite.

The "meta" in "metatronics" refers to metamaterials, the relatively new field of research where nanoscale patterns and structures embedded in materials allow them to manipulate waves in ways that were previously impossible. Here, the cross-sections of the nanorods and the gaps between them form a pattern that replicates the function of resistors, inductors and capacitors, three of the most basic circuit elements, but in optical wavelengths.

"If we have the optical version of those lumped elements in our repertoire, we can actually make designs similar to what we do in electronics but now for operation with light," Engheta said. "We can build a circuit with light."

In their experiment, the researchers illuminated the nanorods with an optical signal, a wave of light in the mid-infrared range. They then used spectroscopy to measure the wave as it passed through the comb. Repeating the experiment using nanorods with nine different combinations of widths and heights, the researchers showed that the optical "current" and optical "voltage" were altered by the optical resistors, inductors and capacitors with parameters corresponding to those differences in size.

"A section of the nanorod acts as both an inductor and resistor, and the air gap acts as a capacitor," Engheta said.

Beyond changing the dimensions and the material the nanorods are made of, the function of these optical circuits can be altered by changing the orientation of the light, giving metatronic circuits access to configurations that would be impossible in traditional electronics.

This is because a light wave has polarizations; the electric field that oscillates in the wave has a definable orientation in space. In metatronics, it is that electric field that interacts and is changed by elements, so changing the field's orientation can be like rewiring an electric circuit.

When the plane of the field is in line with the nanorods, as in Figure A, the circuit is wired in parallel and the current passes through the elements simultaneously. When the plane of the electric field crosses both the nanorods and the gaps, as in Figure B, the circuit is wired in series and the current passes through the elements sequentially.

"The orientation gives us two different circuits, which is why we call this 'stereo-circuitry,'" Engheta said. "We could even have the wave hit the rods obliquely and get something we don't have in regular electronics: a circuit that's neither in series or in parallel but a mixture of the two."

This principle could be taken to an even higher level of complexity by building nanorod arrays in three dimensions. An optical signal hitting such a structure's top would encounter a different circuit than a signal hitting its side. Building off their success with basic optical elements, Engheta and his group are laying the foundation for this kind of complex metatronics.

"Another reason for success in electronics has to do with its modularity," he said. "We can make an infinite number of circuits depending on how we arrange different circuit elements, just like we can arrange the alphabet into different words, sentences and paragraphs.

"We're now working on designs for more complicated optical elements," Engheta said. "We're on a quest to build these new letters one by one."

This work was supported in part by the U.S. Air Force Office of Scientific Research.

Andrea Alù is now an assistant professor at the University of Texas at Austin.

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More Powerful Supercomputers? New Device Could Bring Optical Information Processing

More Powerful Supercomputers? New Device Could Bring Optical Information Processing

  10:35:00 AM    Science Lover

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Researchers have created a new type of optical device small enough to fit millions on a computer chip that could lead to faster, more powerful information processing and supercomputers.

This illustration shows a new "all-silicon passive optical diode," a device small enough to fit millions on a computer chip that could lead to faster, more powerful information processing and supercomputers. The device has been developed by Purdue University researchers. (Credit: Birck Nanotechnology Center, Purdue University)

The "passive optical diode" is made from two tiny silicon rings measuring 10 microns in diameter, or about one-tenth the width of a human hair. Unlike other optical diodes, it does not require external assistance to transmit signals and can be readily integrated into computer chips.

The diode is capable of "nonreciprocal transmission," meaning it transmits signals in only one direction, making it capable of information processing, said Minghao Qi (pronounced Chee), an associate professor of electrical and computer engineering at Purdue University.

"This one-way transmission is the most fundamental part of a logic circuit, so our diodes open the door to optical information processing," said Qi, working with a team also led by Andrew Weiner, Purdue's Scifres Family Distinguished Professor of Electrical and Computer Engineering.

The diodes are described in a paper to be published online Dec. 22 in the journal Science. The paper was written by graduate students Li Fan, Jian Wang, Leo Varghese, Hao Shen and Ben Niu, research associate Yi Xuan, and Weiner and Qi.

Although fiberoptic cables are instrumental in transmitting large quantities of data across oceans and continents, information processing is slowed and the data are susceptible to cyberattack when optical signals must be translated into electronic signals for use in computers, and vice versa.

"This translation requires expensive equipment," Wang said. "What you'd rather be able to do is plug the fiber directly into computers with no translation needed, and then you get a lot of bandwidth and security."

Electronic diodes constitute critical junctions in transistors and help enable integrated circuits to switch on and off and to process information. The new optical diodes are compatible with industry manufacturing processes for complementary metal-oxide-semiconductors, or CMOS, used to produce computer chips, Fan said.

"These diodes are very compact, and they have other attributes that make them attractive as a potential component for future photonic information processing chips," she said.

The new optical diodes could make for faster and more secure information processing by eliminating the need for this translation. The devices, which are nearly ready for commercialization, also could lead to faster, more powerful supercomputers by using them to connect numerous processors together.

"The major factor limiting supercomputers today is the speed and bandwidth of communication between the individual superchips in the system," Varghese said. "Our optical diode may be a component in optical interconnect systems that could eliminate such a bottleneck."

Infrared light from a laser at telecommunication wavelength goes through an optical fiber and is guided by a microstructure called a waveguide. It then passes sequentially through two silicon rings and undergoes "nonlinear interaction" while inside the tiny rings. Depending on which ring the light enters first, it will either pass in the forward direction or be dissipated in the backward direction, making for one-way transmission. The rings can be tuned by heating them using a "microheater," which changes the wavelengths at which they transmit, making it possible to handle a broad frequency range.

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One of the World's Smallest Electronic Circuits Created

One of the World's Smallest Electronic Circuits Created

  9:48:00 AM    Science Lover

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A team of scientists, led by Guillaume Gervais from McGill's Physics Department and Mike Lilly from Sandia National Laboratories, has engineered one of the world's smallest electronic circuits. It is formed by two wires separated by only about 150 atoms or 15 nanometers (nm).

Scientists have engineered one of the world's smallest electronic
circuits. It is formed by two wires separated by only about 150
atoms or 15 nanometers (nm).
(Credit: Image courtesy of McGill University)

The discovery, published in the journal Nature Nanotechnology, could have a significant effect on the speed and power of the ever smaller integrated circuits of the future in everything from smartphones to desktop computers, televisions and GPS systems.

This is the first time that anyone has studied how the wires in an electronic circuit interact with one another when packed so tightly together. Surprisingly, the authors found that the effect of one wire on the other can be either positive or negative. This means that a current in one wire can produce a current in the other one that is either in the same or the opposite direction. This discovery, based on the principles of quantum physics, suggests a need to revise our understanding of how even the simplest electronic circuits behave at the nanoscale.

In addition to the effect on the speed and efficiency of future electronic circuits, this discovery could also help to solve one of the major challenges facing future computer design. This is managing the ever-increasing amount of heat produced by integrated circuits

Well-known theorist Markus Büttiker speculates that it may be possible to harness the energy lost as heat in one wire by using other wires nearby. Moreover, Buttiker believes that these findings will have an impact on the future of both fundamental and applied research in nanoelectronics.

The research was funded by the Natural Sciences and Engineering Research Council of Canada, the Fonds de recherche Nature et Technologies of Quebec, the Canadian Institute for Advanced Research and the Center of Integrated Nanotechnologies at Sandia National Laboratories.

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Design Rules Will Enable Scientists to Use DNA to Build Nanomaterials With Desired Properties

Design Rules Will Enable Scientists to Use DNA to Build Nanomaterials With Desired Properties

  12:35:00 AM    Science Lover

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Nature is a master builder. Using a bottom-up approach, nature takes tiny atoms and, through chemical bonding, makes crystalline materials, like diamonds, silicon and even table salt. In all of them, the properties of the crystals depend upon the type and arrangement of atoms within the crystalline lattice.

Abstract rendering of a DNA strand.
(Credit: iStockphoto/Johan Swanepoel)

Now, a team of Northwestern University scientists has learned how to top nature by building crystalline materials from nanoparticles and DNA, the same material that defines the genetic code for all living organisms.

Using nanoparticles as "atoms" and DNA as "bonds," the scientists have learned how to create crystals with the particles arranged in the same types of atomic lattice configurations as some found in nature, but they also have built completely new structures that have no naturally occurring mineral counterpart.

The basic design rules the Northwestern scientists have established for this approach to nanoparticle assembly promise the possibility of creating a variety of new materials that could be useful in catalysis, electronics, optics, biomedicine and energy generation, storage and conversion technologies.

The new method and design rules for making crystalline materials from nanostructures and DNA will be published Oct. 14 by the journal Science.

"We are building a new periodic table of sorts," said Professor Chad A. Mirkin, who led the research. "Using these new design rules and nanoparticles as 'artificial atoms,' we have developed modes of controlled crystallization that are, in many respects, more powerful than the way nature and chemists make crystalline materials from atoms. By controlling the size, shape, type and location of nanoparticles within a given lattice, we can make completely new materials and arrangements of particles, not just what nature dictates."

Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and professor of medicine, chemical and biological engineering, biomedical engineering and materials science and engineering and director of Northwestern's International Institute for Nanotechnology (IIN).

"Once we have a certain type of lattice," Mirkin said, "the particles can be moved closer together or farther apart by changing the length of the interconnecting DNA, thereby providing near-infinite tunability."

"This work resulted from an interdisciplinary collaboration that coupled synthetic chemistry with theoretical model building," said coauthor George C. Schatz, a theoretician and the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern. "It was the back and forth between synthesis and theory that was crucial to the development of the design rules. Collaboration is a special aspect of research at Northwestern, and it worked very effectively for this project."



In the study, the researchers start with two solutions of nanoparticles coated with single-stranded DNA. They then add DNA strands that bind to these DNA-functionalized particles, which then present a large number of DNA "sticky ends" at a controlled distance from the particle surface; these sticky ends then bind to the sticky ends of adjacent particles, forming a macroscopic arrangement of nanoparticles.

Different crystal structures are achieved by using different combinations of nanoparticles (with varying sizes) and DNA linker strands (with controllable lengths). After a process of mixing and heating, the assembled particles transition from an initially disordered state to one where every particle is precisely located according to a crystal lattice structure. The process is analogous to how ordered atomic crystals are formed.

The researchers report six design rules that can be used to predict the relative stability of different structures for a given set of nanoparticle sizes and DNA lengths. In the paper, they use these rules to prepare 41 different crystal structures with nine distinct crystal symmetries. However, the design rules outline a strategy to independently adjust each of the relevant crystallographic parameters, including particle size (varied from 5 to 60 nanometers), crystal symmetry and lattice parameters (which can range from 20 to 150 nanometers). This means that these 41 crystals are just a small example of the near infinite number of lattices that could be created using different nanoparticles and DNA strands.

Mirkin and his team used gold nanoparticles in their work but note that their method also can be applied to nanoparticles of other chemical compositions. Both the type of nanoparticle assembled and the symmetry of the assembled structure contribute to the properties of a lattice, making this method an ideal means to create materials with predictable and controllable physical properties.

Mirkin believes that, one day soon, software will be created that allows scientists to pick the particle and DNA pairs required to make almost any structure on demand.

The Air Force Office of Scientific Research, the U.S. Department of Energy Office of Basic Energy Sciences and the National Science Foundation supported the research.

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Electricity from the nose: Engineers make power from human respiration

Electricity from the nose: Engineers make power from human respiration

  8:59:00 AM    Science Lover

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The same piezoelectric effect that ignites your gas grill with the push of a button could one day power sensors in your body via the respiration in your nose.

Graduate Student Jian Shi and Materials Science and
Engineering Assistant Professor Xudong Wang
demonstrate a material that could be used to
capture energy from respiration.

Writing in the September issue of the journal Energy and Environmental Science, Materials Science and Engineering Assistant Professor Xudong Wang, postdoctoral Researcher Chengliang Sun and graduate student Jian Shi report creating a plastic microbelt that vibrates when passed by low-speed airflow such as human respiration.

In certain materials, such as the polyvinylidene fluoride (PVDF) used by Wang’s team, an electric charge accumulates in response to applied mechanical stress. This is known as the piezoelectric effect. The researchers engineered PVDF to generate sufficient electrical energy from respiration to operate small electronic devices.



“Basically, we are harvesting mechanical energy from biological systems. The airflow of normal human respiration is typically below about two meters per second,” says Wang. “We calculated that if we could make this material thin enough, small vibrations could produce a microwatt of electrical energy that could be useful for sensors or other devices implanted in the face.”

Researchers are taking advantage of advances in nanotechnology and miniaturized electronics to develop a host of biomedical devices that could monitor blood glucose for diabetics or keep a pacemaker battery charged so that it would not need replacing. What’s needed to run these tiny devices is a miniscule power supply. Waste energy in the form or blood flow, motion, heat, or in this case respiration, offers a consistent source of power.

Wang’s team used an ion-etching process to carefully thin material while preserving its piezoelectric properties. With improvements, he believes the thickness can be controlled down to the submicron level. Because PVDF is biocompatible, he says the development represents a significant advance toward creating a practical micro-scale device for harvesting energy from respiration.

Provided by University of Wisconsin-Madison

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Etch-a-sketch with superconductors

Etch-a-sketch with superconductors

  10:26:00 AM    Science Lover

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Reporting in Nature Materials this week, researchers from the London Centre for Nanotechnology and the Physics Department of Sapienza University of Rome have discovered a technique to 'draw' superconducting shapes using an X-ray beam. This ability to create and control tiny superconducting structures has implications for a completely new generation of electronic devices.

In future, X-ray beams could be used to write superconducting circuits, such as those depicted in the image. Here, solid lines indicate electrical connections while semicircles denote superconducting junctions, whose states are indicated by red arrows. Credit: UCL Press Office

Superconductivity is a special state where a material conducts electricity with no resistance, meaning absolutely zero energy is wasted.

The research group has shown that they can manipulate regions of high temperature superconductivity, in a particular material which combines oxygen, copper and a heavier, 'rare earth' element called lanthanum. Illuminating with X-rays causes a small scale re-arrangement of the oxygen atoms in the material, resulting in high temperature superconductivity, of the type originally discovered for such materials 25 years ago by IBM scientists. The X-ray beam is then used like a pen to draw shapes in two dimensions.

A well as being able to write superconductors with dimensions much smaller than the width of a human hair, the group is able to erase those structures by applying heat treatments. They now have the tools to write and erase with high precision, using just a few simple steps and without the chemicals ordinarily used in device fabrication. This ability to re-arrange the underlying structure of a material has wider applications to similar compounds containing metal atoms and oxygen, ranging from fuel cells to catalysts.



Prof. Aeppli, Director of the London Centre for Nanotechnology and the UCL investigator on the project, said: "Our validation of a one-step, chemical-free technique to generate superconductors opens up exciting new possibilities for electronic devices, particularly in re-writing superconducting logic circuits. Of profound importance is the key to solving the notorious 'travelling salesman problem', which underlies many of the world's great computational challenges. We want to create computers on demand to solve this problem, with applications from genetics to logistics. A discovery like this means a paradigm shift in computing technology is one step closer."

Prof Bianconi, the leader of the team from Sapienza, added: "It is amazing that in a few simple steps, we can now add superconducting 'intelligence' directly to a material consisting mainly of the common elements copper and oxygen."

More information: The X-ray experiments were performed at the Elettra (Trieste) synchrotron radiation facility. The work is published in Nature Materials, 21 August 2011 (doi:1038/nmat3088) and follows on from previous discovery of fractal-like structures in superconductors (doi:10.1038/nature09260).

Provided by University College London

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Future of energy storage with Graphite + Water

Future of energy storage with Graphite + Water

  1:56:00 PM    Science Lover

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A combination of two ordinary materials – graphite and water – could produce energy storage systems that perform on par with lithium ion batteries, but recharge in a matter of seconds and have an almost indefinite lifespan.

Graphene sheets. Credit: Gengping Jiang

Dr. Dan Li, of the Monash University Department of Materials Engineering, and his research team have been working with a material called graphene, which could form the basis of the next generation of ultrafast energy storage systems.

“Once we can properly manipulate this material, your iPhone, for example, could charge in a few seconds, or possibly faster.” said Dr. Li.

Graphene is the result of breaking down graphite, a cheap, readily available material commonly used in pencils, into layers one atom thick. In this form, it has remarkable properties.

Graphene is strong, chemically stable, an excellent conductor of electricity and, importantly, has an extremely high surface area.

Dr. Li said these qualities make graphene highly suitable for energy storage applications.



“The reason graphene isn’t being used everywhere is that these very thin sheets, when stacked into a usable macrostructure, immediately bond together, reforming graphite. When graphene restacks, most of the surface area is lost and it doesn’t behave like graphene anymore.”

Now, Dr. Li and his team have discovered the key to maintaining the remarkable properties of separate graphene sheets: water. Keeping graphene moist – in gel form – provides repulsive forces between the sheets and prevents re-stacking, making it ready for real-world application.

“The technique is very simple and can easily be scaled up. When we discovered it, we thought it was unbelievable. We’re taking two basic, inexpensive materials – water and graphite – and making this new nanomaterial with amazing properties,” said Dr. Li.

When used in energy devices, graphene gel significantly outperforms current carbon-based technology, both in terms of the amount of charge stored and how fast the charges can be delivered.

Dr. Li said the benefits of developing this new nanotechnology extend beyond consumer electronics.

“High-speed, reliable and cost-effective energy storage systems are critical for the future viability of electricity from renewable resources. These systems are also the key to large-scale adoption of electrical vehicles.

“Graphene gel is also showing promise for use in water purification membranes, biomedical devices and sensors.”

Provided by Monash University

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U of T researchers build an antenna for light

U of T researchers build an antenna for light

  9:53:00 AM    Science Lover

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University of Toronto researchers have derived inspiration from the photosynthetic apparatus in plants to engineer a new generation of nanomaterials that control and direct the energy absorbed from light.

Their findings are reported in a forthcoming issue of Nature Nanotechnology, which will be released on July 10, 2011.

The U of T researchers, led by Professors Shana Kelley and Ted Sargent, report the construction of what they term "artificial molecules."

"Nanotechnologists have for many years been captivated by quantum dots – particles of semiconductor that can absorb and emit light efficiently, and at custom-chosen wavelengths," explained co-author Kelley, a Professor at the Leslie Dan Faculty of Pharmacy, the Department of Biochemistry in the Faculty of Medicine, and the Department of Chemistry in the Faculty of Arts & Science. "What the community has lacked – until now – is a strategy to build higher-order structures, or complexes, out of multiple different types of quantum dots. This discovery fills that gap."

The team combined its expertise in DNA and in semiconductors to invent a generalized strategy to bind certain classes of nanoparticles to one another.

"The credit for this remarkable result actually goes to DNA: its high degree of specificity – its willingness to bind only to a complementary sequence – enabled us to build rationally-engineered, designer structures out of nanomaterials," said Sargent, a Professor in The Edward S. Rogers Sr. Department of Electrical & Computer Engineering at the University of Toronto, who is also the Canada Research Chair in Nanotechnology. "The amazing thing is that our antennas built themselves – we coated different classes of nanoparticles with selected sequences of DNA, combined the different families in one beaker, and nature took its course. The result is a beautiful new set of self-assembled materials with exciting properties."



Traditional antennas increase the amount of an electromagnetic wave – such as a radio frequency – that is absorbed, and then funnel that energy to a circuit. The U of T nanoantennas instead increased the amount of light that is absorbed and funneled it to a single site within their molecule-like complexes. This concept is already used in nature in light harvesting antennas, constituents of leaves that make photosynthesis efficient. "Like the antennas in radios and mobile phones, our complexes captured dispersed energy and concentrated it to a desired location. Like the light harvesting antennas in the leaves of a tree, our complexes do so using wavelengths found in sunlight," explained Sargent.

"Professors Kelley and Sargent have invented a novel class of materials with entirely new properties. Their insight and innovative research demonstrates why the University of Toronto leads in the field of nanotechnology," said Professor Henry Mann, Dean of the Leslie Dan Faculty of Pharmacy.

"This is a terrific piece of work that demonstrates our growing ability to assemble precise structures, to tailor their properties, and to build in the capability to control these properties using external stimuli," noted Paul S. Weiss, Fred Kavli Chair in NanoSystems Sciences at UCLA and Director of the California NanoSystems Institute.

Kelley explained that the concept published in today's Nature Nanotechnology paper is a broad one that goes beyond light antennas alone.

"What this work shows is that our capacity to manipulate materials at the nanoscale is limited only by human imagination. If semiconductor quantum dots are artificial atoms, then we have rationally synthesized artificial molecules from these versatile building blocks."

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New Laser Technology Could Kill Viruses and Improve DVDs

New Laser Technology Could Kill Viruses and Improve DVDs

  10:16:00 AM    Science Lover

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A team led by a professor at the University of California, Riverside Bourns College of Engineering has made a discovery in semiconductor nanowire laser technology that could potentially do everything from kill viruses to increase storage capacity of DVDs.

From left, Guoping Wang, a graduate student, Jianlin Liu, a professor of electrical engineering, and Sheng Chu, a graduate student. (Credit: Image courtesy of University of California - Riverside)

Ultraviolet semiconductor diode lasers are widely used in data processing, information storage and biology. Their applications have been limited, however, by size, cost and power. The current generation of ultraviolet lasers is based on a material called gallium nitride, but Jianlin Liu, a professor of electrical engineering, and his colleagues have made a breakthrough in zinc oxide nanowire waveguide lasers, which can offer smaller sizes, lower costs, higher powers and shorter wavelengths.

Until now, zinc oxide nanowires couldn't be used in real world light emission applications because of the lack of p-type, or positive type, material needed by all semiconductors. Liu solved that problem by doping the zinc oxide nanowires with antimony, a metalloid element, to create the p-type material.

The p-type zinc oxide nanowires were connected with n-type, or negative type, zinc oxide material to form a device called p-n junction diode. Powered by a battery, highly directional laser light emits only from the ends of the nanowires.

"People in the zinc oxide research community throughout the world have been trying hard to achieve this for the past decade," Liu said. "This discovery is likely to stimulate the whole field to push the technology further."

Liu's findings have been published in the July issue of Nature Nanotechnology. Co-authors are: Sheng Chu, Guoping Wang, Jieying Kong, Lin Li and Jingjian Ren, all graduate students at UC Riverside; Weihang Zhou, a student at Fudan University in China; Leonid Chernyak, a professor of physics at the University of Central Florida; Yuqing Lin, a graduate student at the University of Central Florida; and Jianze Zhao, a visiting student from Dalian University of Technology in China.

The discovery could have a wide-range of impacts.



For information storage, the zinc oxide nanowire lasers could be used to read and process much denser data on storage media such as DVDs because the ultraviolet has shorter wavelength than other lights, such as red. For example, a DVD that would store two hours of music could store four or six hours using the new type of laser.

For biology and medical therapeutics, the ultra-small laser light beam from a nanowire laser can penetrate a living cell, or excite or change its function from a bad cell to a good cell. The light could also be used to purify drinking water.

For photonics, the ultraviolet light could provide superfast data processing and transmission. Reliable small ultraviolet semiconductor diode lasers may help develop ultraviolet wireless communication technology, which is potentially better than state-of-the-art infrared communication technologies used in various electronic information systems.

While Liu and the students in his laboratory have demonstrated the p-type doping of zinc oxide and electrically powered nanowire waveguide lasing in the ultraviolet range, he said more work still needs to be done with the stability and reliability of the p-type material.

The work on the ZnO device was in part supported by Army Research Office Young Investigator Program and the National Science Foundation. The work on p-type ZnO was supported by the Department of Energy.

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IBM scientists demonstrate computer memory breakthrough

IBM scientists demonstrate computer memory breakthrough

  8:47:00 PM    Science Lover

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For the first time, scientists at IBM Research have demonstrated that a relatively new memory technology, known as phase-change memory (PCM), can reliably store multiple data bits per cell over extended periods of time. This significant improvement advances the development of low-cost, faster and more durable memory applications for consumer devices, including mobile phones and cloud storage, as well as high-performance applications, such as enterprise data storage.

With a combination of speed, endurance, non-volatility and density, PCM can enable a paradigm shift for enterprise IT and storage systems within the next five years. Scientists have long been searching for a universal, non-volatile memory technology with far superior performance than flash – today’s most ubiquitous non-volatile memory technology. The benefits of such a memory technology would allow computers and servers to boot instantaneously and significantly enhance the overall performance of IT systems. A promising contender is PCM that can write and retrieve data 100 times faster than flash, enable high storage capacities and not lose data when the power is turned off. Unlike flash, PCM is also very durable and can endure at least 10 million write cycles, compared to current enterprise-class flash at 30,000 cycles or consumer-class flash at 3,000 cycles. While 3,000 cycles will out live many consumer devices, 30,000 cycles are orders of magnitude too low to be suitable for enterprise applications (see chart for comparisons).

“As organizations and consumers increasingly embrace cloud-computing models and services, whereby most of the data is stored and processed in the cloud, ever more powerful and efficient, yet affordable storage technologies are needed,” states Dr. Haris Pozidis, Manager of Memory and Probe Technologies at IBM Research – Zurich. “By demonstrating a multi-bit phase-change memory technology which achieves for the first time reliability levels akin to those required for enterprise applications, we made a big step towards enabling practical memory devices based on multi-bit PCM.”

Multi-level Phase Change Memory Breakthrough

To achieve this breakthrough demonstration, IBM scientists in Zurich used advanced modulation coding techniques to mitigate the problem of short-term drift in multi-bit PCM, which causes the stored resistance levels to shift over time, which in turn creates read errors. Up to now, reliable retention of data has only been shown for single bit-per-cell PCM, whereas no such results on multi-bit PCM have been reported.

PCM leverages the resistance change that occurs in the material — an alloy of various elements — when it changes its phase from crystalline — featuring low resistance — to amorphous — featuring high resistance — to store data bits. In a PCM cell, where a phase-change material is deposited between a top and a bottom electrode, phase change can controllably be induced by applying voltage or current pulses of different strengths. These heat up the material and when distinct temperature thresholds are reached cause the material to change from crystalline to amorphous or vice versa.

In addition, depending on the voltage, more or less material between the electrodes will undergo a phase change, which directly affects the cell's resistance. Scientists exploit that aspect to store not only one bit, but multiple bits per cell. In the present work, IBM scientists used four distinct resistance levels to store the bit combinations “00”, “01” 10” and “11”.



To achieve the demonstrated reliability, crucial technical advancements in the “read” and “write” process were necessary. The scientists implemented an iterative “write” process to overcome deviations in the resistance due to inherent variability in the memory cells and the phase-change materials: “We apply a voltage pulse based on the deviation from the desired level and then measure the resistance. If the desired level of resistance is not achieved, we apply another voltage pulse and measure again — until we achieve the exact level,” explains Pozidis.

Despite using the iterative process, the scientists achieved a worst-case write latency of about 10 microseconds, which represents a 100× performance increase over even the most advanced Flash memory on the market today.

For demonstrating reliable read-out of data bits, the scientists needed to tackle the problem of resistance drift. Because of structural relaxation of the atoms in the amorphous state, the resistance increases over time after the phase change, eventually causing errors in the read-out. To overcome that issue, the IBM scientists applied an advanced modulation coding technique that is inherently drift-tolerant. The modulation coding technique is based on the fact that, on average, the relative order of programmed cells with different resistance levels does not change due to drift.

Using that technique, the IBM scientists were able to mitigate drift and demonstrate long- term retention of bits stored in a subarray of 200,000 cells of their PCM test chip, fabricated in 90-nanometer CMOS technology. The PCM test chip was designed and fabricated by scientists and engineers located in Burlington, Vermont; Yorktown Heights, New York and in Zurich. This retention experiment has been under way for more than five months, indicating that multi-bit PCM can achieve a level of reliability that is suitable for practical applications.

The PCM research project at IBM Research – Zurich will continue to be studied at the recently opened Binnig and Rohrer Nanotechnology Center. The center, which is jointly operated by IBM and ETH Zurich as part of a strategic partnership in nanosciences, offers a cutting-edge infrastructure, including a large cleanroom for micro- and nanofabrication as well as six “noise-free” labs, especially shielded laboratories for highly sensitive experiments.

A History of Pioneering Memory Technology

In 1966, IBM Fellow, Dr. Robert Dennard invented dynamic random access memory — DRAM — which, when combined with the first low-cost microprocessors, opened the door to small personal computers. Today, every PC, notebook computer, game console and other computing device is loaded with DRAM chips. DRAM also powers mainframes, data center servers and most of the machines that run the Internet. In 1988, Dennard was awarded the US National Medal of Technology for the invention of DRAM. As IBM celebrates its Centennial this year, the company celebrates DRAM as one of its 100 greatest innovations.

More information: The paper “Drift-tolerant Multilevel Phase-Change Memory” by N. Papandreou, H. Pozidis, T. Mittelholzer, G.F. Close, M. Breitwisch, C. Lam and E. Eleftheriou, was recently presented by Haris Pozidis at the 3rd IEEE International Memory Workshop in Monterey, CA.

Provided by IBM

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Tiny Ring Laser Accurately Detects and Counts Nanoparticles

Tiny Ring Laser Accurately Detects and Counts Nanoparticles

  8:05:00 PM    Science Lover

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A tiny doughnut-shaped laser is the latest marvel of silicon microminiaturization, but instead of manipulating bits it detects very small particles. Small particles play a big -- and largely unnoticed -- role in our everyday lives. Virus particles make us sick, salt particles trigger cloud formation, and soot particles sift deep into our lungs and make it harder to breathe.

Whispering-gallery microlasers can count 
and measure nano-scale synthetic or biological 
particles. As this conceptual illustration shows, 
a particle disturbs the lasing "mode" to split 
into two frequencies (shown here as two different 
colors) and the frequency split acts a ruler that 
allows the particle to be measured. The inset 
at the top right shows a particle landing on the 
microlaser (a torus supported by a pedestal). 
Lina He, a graduate student in electrical and 
systems engineering at Washington University 
in St. Louis, and her co-workers demonstrated 
that the microlasers can detect particles 10 
nanometers in radius. Their resolution limit is 
about one nanometer. (Credit: J. Zhu, L. He, 
S. K. Ozdemir, and L. Yang/WUSTL)

The sensor belongs to a category called whispering gallery resonators, which work like the famous whispering gallery in St. Paul's Cathedral in London, where someone on the one side of the dome can hear a message spoken to the wall by someone on the other side. Unlike the dome, which has resonances or sweet spots in the audible range, the sensor resonates at light frequencies.

Light traveling round the micro-laser is disturbed by a particle that lands on the ring, changing the light's frequency. The ring can count the touch-down of as many as 800 nanoparticles before the signals begin to be lost in the noise. By exciting more than one mode in the ring, scientists can double-check the accuracy of the count. And by changing the "gain medium," they can adapt the sensor for water rather than air.

Lan Yang, PhD, assistant professor of electrical and systems engineering at Washington University in St. Louis who leads the team that fabricated the new sensor, says that there is already lively interest in its commercialization in fields ranging from biology to aerosol science. The sensor is described and characterized in the June 26 online edition of Nature Nanotechnology.

Whispering gallery resonator becomes microlaser

A whispering gallery resonator supports "frequency degenerate modes" (modes, or patterns of excitation in the ring, with the same frequency, one traveling clockwise and the other counterclockwise around the ring.

The mode fields have "evanescent tails" that penetrate the surface of the ring and probe the surrounding medium. When a particle lands on one of the "hot spots" it scatters energy from one of the modes into the other, and the modes adopt slightly different resonance frequencies. This is referred to as mode splitting.

In an earlier work, Yang team used mode splitting in a simple glass ring that functioned as a waveguide for light coupled into it from outside. Because the ring was passive, the external-laser had to be an expensive tunable laser so that it could scan a frequency range looking for the ring's resonances to measure mode splitting. (For more information on this sensor see "Tiny sensor takes measure of nanoparticles.")

The new sensor differs from earlier whispering gallery resonators in that it is itself a miniature laser rather than the resonating cavity of an external laser.

The new sensor is also glass but glass laced with atoms of the rare earth elements that serve as a "gain medium." The glass is doped with rare-earth atoms and when an external light source boosts enough of them into an excited state, the ring begins to lase at its own preferred frequency.

When a particle lands on the microlaser, a single lasing line splits into two slightly different frequencies.

A simple way of measuring the frequency splitting is to mix the split laser modes in a photodetector, which produces a "beat frequency" that corresponds to the frequency difference.

"The tiny sensors are mass produced by sol-gel method on silicon wafer, and it is easy to switch the gain medium" says Lina He, a graduate student and first author of the paper. "The resonators are made by mixing the rare-earth ions of choice into a solution of tetraethoxysilane, water and hydrochloric acid. The solution is heated until it becomes viscous and then spin-coated on a silicon wafer and annealed to remove solvents and complete the transition to amorphous glass. The thin film of glass is then etched to create silica disks supported underneath by silicon pillars. As a final step, the rough silica disks are reflowed into smooth toroids by laser annealing."

Active sensor outperforms passive one



"The light used for sensing is generated inside the resonator itself, and so it is purer than the light in the passive sensor," says Yang "When the light is not that pure, you might not be able to see small frequency changes. But the active sensor hits one frequency -- it has a really narrow linewidth -- and so it is much more sensitive."

The microlaser is orders of magnitude more sensitive than the passive resonator, she says. Its effective resolution limit is about one nanometer. One nanometer is to a meter, what a marble is to Earth.

Moreover, because the laser is now in the ring rather than coupled to it, the entire system is simpler and more self contained. "Now you just need a light source to excite the optical medium," says Yang, "and you can use a cheap laser diode for that instead of an expensive tunable laser."

Detecting many particles

The effect of a particle on a lasing mode depends on the particle's "polarizability," which is a function of its size and refractive index. To cover the possibilities, the Washington University team tested the micro-laser's performance with nanoparticles of various sizes made of various materials, including polystyrene (packing peanuts), virions (virus particles) and gold.

As particles enter the "mode volume" of the micro-laser one by one, the scientists can see a discrete upward or downward jump in the beat frequency. Each discrete jump signals the binding of a particle on the ring, and the number of the jumps reflects the number of particles.

Because the "resonator field" traps the particles on the resonator, once landed, they rarely drop off. But the team found they were able to count many particles before the losses induced by the particles made the laser linewidths so broad they couldn't detect changes in frequency splitting due to the latest arrival.

For example, they were able to detect and count as many as 816 gold nanoparticles using the same laser mode.

"When the line broadening is comparable to the change in splitting, then you're done," says Yang. "However, the whole resonator is fabricated on the chip, so you could just move on to the next resonator if necessary."

Doubling up for accuracy

The micro-laser can support more than one laser mode at a time. "By controlling the overlap of the pump light with the gain medium, you can excite more than one laser line," says Sahin Kaya Ozdemir, PhD, a research associate and co-author. "Then when a particle lands on the ring, each laser line will split into two, and generate a beat frequency. So you will have two beat frequencies instead of one."

That's an advantage, he explains, because the beat frequency depends in part on where the particle lands on the ring. If there is only one laser line and the particle falls between "hot spots" it might not be detected. The second beat frequency prevents these "false negatives," ensuring that every particle produces a detectable beat frequency.

Detecting particles in water

The microlasers intended to sense particles in air had been doped with erbium, a rare-earth element whose optical properties are well matched with those of air. In a final experiment designed to see whether this technique could be used to sense particles in water or blood, the team fabricated sensors that were doped with ytterbium rather than erbium.Ytterbium lases at wavelengths with low absorption of light by water

Yang's team has already begun working to make use of the enhanced sensitivity provided by the microlaser for studying various problems. In terms of applications, "the near-term use will be the monitoring of dynamic behaviors of particles in response to environmental and chemical changes at single particle resolution," says Yang.

The next step, the team see is to engineer the surface of these tiny microlasers to detect DNA and individual biological molecules. If the DNA is tagged with engineered nanoparticles, the micro-laser sensor can count individual DNA molecules or fragments of molecules.

Listening to Yang it is hard to escape the impression that you're hearing for the first time about an astonishing device that will one day be as ubiquitous -- and probably as underappreciated -- as the logic gates in our microwaves, cellphones and cars.

The Washington University in St. Louis team behind these results includes: L. He, W. Kim and J. Zhu, graduate students; S. K. Ozdemir, PhD, a research associate, and L. Yang, PhD, assistant professor in electrical and systems engineering.

This work is supported by National Science Foundation.

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