Nanopore will make for speedy DNA sequencing

17:15 10 April 2006
NewScientist.com news service
Tom Simonite

A new technique harnessing a “nanopore” to detect electrical changes as a strand of DNA is passed through it could speed up DNA sequencing more than 200 times. The system could process the human genome in hours, researchers claim, compared with the 6 months it would take in today's best labs.
The technique has been tested theoretically by US physicists using a detailed computer simulation of over 100,000 interacting atoms. The DNA-sequencing nanopore is yet to be built, but you can view the simulation, here (mpeg format).
The device would work by running an electric current across a DNA strand as it is drawn through a nanopore, using electrodes built into the pore's sides. Detecting the changes in current that correspond to the four different bases, or "letters", that make up DNA would read off the sequence as it passed.
"Because we're all physicists working on this we've started at the very bottom – with atoms," explains Johan Lagerqvist, a physicist at the University of California, San Diego, US, who worked on the simulation. Lagerqvist and colleagues tested a virtual version of the system by modelling how 100,000 atoms in a short DNA strand, the silicon nitride nanopore, its electrodes and the surrounding chemical solution would all interact.
Multiple measurements
Because DNA is a kind of acid, it has a negative charge and can be drawn through a nanopore by a positive electrode on the other side. But the researchers found that to accurately record the sequence of the strand as it passes through, electrodes on the inside of the pore have to scan each base many times.
"The changes each base causes in the current are not always identical," explains Lagerqvist. "They overlap a little, but we can get around this by taking more than one measurement for each base as it passes." Taking the average of 70 readings from each base made the scanner 99.9% accurate.
In a lab dish, a piece of DNA like that used in the virtual model would take just microseconds to pass through a pore, but modelling the process took 40 high-powered computers around a week. "At a scale this small, each and every atom matters," said Lagerqvist. "We were able to prove that this system could work, and the components to make it already exist, all that's needed now is to put them together."
Nanotubes in nanopores
In fact, a separate team at Harvard University, Massachusetts, US, has been trying build such a nanopore. "Using a nanopore with a current running across it to look at DNA has enormous potential," says Daniel Branton, group leader of the nanopore group at Harvard.
"This technique could also be used for other polymers like proteins or for artificial molecules. And that information has all kinds of valuable uses. We and other groups have been interested in this for some time, but this new simulation gives specifics about how such a device might be used."
The Harvard group are experimenting with adding a carbon nanotube inside a nanopore – a pore left behind after depositing silicon nitride in a way that leaves a pore behind. The carbon nanotube would act as an electrode inside the pore. "We've managed to articulate these tubes and pores together," says Branton. "Because of the favourable electrical properties of the tubes they can function as the electrodes to run current across the molecule passing through the pore."
But although results are promising, rapid scanning of DNA is still dependent on solving a still difficult construction problem. "We have measured some proof of principle signals from molecules in pores," says Branton, "but we're talking about putting things together at the nano level, which is not easily done."

Scientists are meeting the technical challenges of OLED

In the race to create the roll-up TV (and a host of other devices), scientists are continually manipulating organic light-emitting diode (OLED) technology. Recently, researchers from Korea have designed a technique that is rigid enough to allow extremely high resolution and flexible enough to cover a large area in a simple process.


Because OLED technology is one of the newer methods to enter the flat panel display market, analysts initially predicted that OLED would have some catching up to do to compete with the popularity of LEDs, LCDs (liquid crystal devices) and plasma screens. However, scientists are meeting the technical challenges of OLEDs and designing technology that proves its worth in many regards: it’s brighter, faster, lighter, cheaper, bigger and smaller than other technologies in certain areas.

OLEDs, like LEDs, are electroluminescent, meaning they generate light when electrically stimulated. As opposed to LEDs that use superconductors to enable electron-hole recombination, OLEDs use carbon-based molecules (which vary depending on desired color). However, the two most prominent OLED techniques have limitations: the pattern transfer method has color constraints, and the shadow mask method can only cover small areas.

In a recent issue of Nanotechnology, scientists Jun-ho Choi et al. present a simple and effective method for OLED displays using rigiflex lithography, a technique that members of the team introduced last year.

“While the rigid nature of the rigiflex mould allows resolution down to the sub-100 nm range, the flexible nature of the mould makes it possible for the transfer to be applied to large areas,” wrote the scientists. “A flat substrate is not necessarily flat in that there is always roughness at the nanometer scale if not the micrometer level….A flexible mould can make intimate contact with the underlying surface over a large area because of the flexibility, which makes large area applications possible.”

To enable large area applications, the method uses low pressure for the transfer of a mold made of poly (urethane acrylate) (PUA). After depositing organic multilayers on the mold, the design is transferred to a glass-coated (indium tin oxide) surface by a simple process based on the adhesion difference between the mold and the surface.

Compared with other OLED techniques, rigiflex lithography demonstrates equivalent luminance strength, but outperformed other techniques with its large size, flexibility and simplicity. The method allows a simple step-and-repeat transfer of each color (red, green and blue) OLED.

“There is no particular limit on the size in principle,” Hong Lee, coauthor, told PhysOrg.com. “With rigiflex OLED, you can 'print' the whole device in one process, whereas with other techniques, you have to do it one at a time, many times for many layers involved in the fabrication.”

Applications for OLED technology currently under investigation include "smart" light-emitting shades; video walls; and electronic displays on clothes, windshields and visors for pilots, drivers and scuba divers.

By Lisa Zyga, Copyright 2006 PhysOrg.com

Solar-powered retinal implant

AN IMPLANT that squirts chemicals into the back of your eye may not sound like much fun. But a solar-powered chip that stimulates retinal cells by spraying them with neurotransmitters could restore sight to blind people.
Unlike other implants under development that apply an electric charge directly to retinal cells, the device does not cause the cells to heat up. It also uses very little power, so it does not need external batteries.
The retina, which lines the back and sides of the eyeball, contains photoreceptor cells that release signalling chemicals called neurotransmitters in response to light. The neurotransmitters pass into nerve cells on top of the photoreceptors, from where the signals are relayed to the brain via a series of electrical and chemical reactions. In people with retinal diseases such as age-related macular degeneration and retinitis pigmentosa, the photoreceptors become damaged, ultimately causing blindness.
Last year engineer Laxman Saggere of the University of Illinois at Chicago unveiled plans for an implant that would replace these damaged photoreceptors with a set of neurotransmitter pumps that respond to light. Now he has built a crucial component: a solar-powered actuator that flexes in response to the very low intensity light that strikes the retina. Multiple actuators on a single chip pick up the details of the image focused on the retina, allowing some "pixels" to be passed on to the brain.
The prototype actuator consists of a flexible silicon disc just 1.5 millimetres in diameter and 15 micrometres thick. When light hits a silicon solar cell next to the disc it produces a voltage. The solar cell is connected to a layer of piezoelectric material called lead zirconate titanate (PZT), which changes shape in response to the voltage, pushing down on the silicon disc. In future, a reservoir will sit underneath the disc, and this action will squeeze the neurotransmitters out onto retinal cells.

From here we just need to be able to generate the neurotransmitter in the device.

NEWS, but not as we know it

It will mean stories can be defined, on the fly, with a precision greater than a library's card catalogue.
The News Engine Web Services (NEWS) platform is aimed at news agencies, governments and large enterprises and will enable them to develop highly advanced analysis to raw text, with a vast number of potential applications.
News agencies will be able to automatically create very highly personalised news profiles for readers. Governments will be able to analyse social and political trends through newspaper reports, at a much higher level of detail than was possible previously, and large businesses will be able to study market and product developments.
The project that developed the platform even managed to develop a proof-of-concept service for analysing audio, by combining their system with a commercial voice recognition programme.
At the heart of this functionality is the powerful classification and ontology-based annotation system that can work across languages. "News classifications up to now typically consisted of about 12 terms, like sport, world news, finance, that a journalist knew off by heart," says Dr Ansgar Bernardi, deputy head of the Knowledge Management Group at DFKI, the German Research Centre for Artificial Intelligence, and coordinator of the IST-funded NEWS project.
"That's not very precise. Our system can automatically analyse a story and access 1300 classification terms to define it," says Bernardi.
What's more it can access a large ontology of terms related to the specific story definitions within a class, terms like president, head-of-state and government in the politics class, for example. The end result is a very large data set of standardised terms that define the story's content.
That data set can then be used in a huge variety of ways to potentially answer almost any query a user can imagine. A simple example: "Show me news items about the US president in January 2006" will deliver news items about George W. Bush in this time frame.
"We expect that platform users will take the basic functionality and develop around it to respond to the information they want to analyse," says Bernardi. The system also needs to be 'trained' for analysis of specific topics.
To avoid 'false positives', where two people of the same name are confused, for example, or where two cities have the same name, the NEWS team developed IdentityRank, an adaptive algorithm for instance disambiguation.
"It really started out as a by-product of our main work, but it works well and I think it may generate quite a bit of scientific interest," says Bernardi.
It's only one of NEWS' many achievements, and work will not stop there. "We have developed a great network during the project and the consortium has agreed to offer mutual support for a further two years. In the meantime we are pursuing commercial opportunities, several news agencies are interested in the platform, and we had a lot of exposure at CEBIT '05 and '06," says Bernardi

New and Improved Antimatter Spaceship for Mars Missions

Most self-respecting starships in science fiction stories use antimatter as fuel for a good reason – it’s the most potent fuel known. While tons of chemical fuel are needed to propel a human mission to Mars, just tens of milligrams of antimatter will do (a milligram is about one-thousandth the weight of a piece of the original M&M candy).
However, in reality this power comes with a price. Some antimatter reactions produce blasts of high energy gamma rays. Gamma rays are like X-rays on steroids. They penetrate matter and break apart molecules in cells, so they are not healthy to be around. High-energy gamma rays can also make the engines radioactive by fragmenting atoms of the engine material.
The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers working on a new design for an antimatter-powered spaceship that avoids this nasty side effect by producing gamma rays with much lower energy.
Antimatter is sometimes called the mirror image of normal matter because while it looks just like ordinary matter, some properties are reversed. For example, normal electrons, the familiar particles that carry electric current in everything from cell phones to plasma TVs, have a negative electric charge. Anti-electrons have a positive charge, so scientists dubbed them "positrons".
When antimatter meets matter, both annihilate in a flash of energy. This complete conversion to energy is what makes antimatter so powerful. Even the nuclear reactions that power atomic bombs come in a distant second, with only about three percent of their mass converted to energy.
Previous antimatter-powered spaceship designs employed antiprotons, which produce high-energy gamma rays when they annihilate. The new design will use positrons, which make gamma rays with about 400 times less energy.
The NIAC research is a preliminary study to see if the idea is feasible. If it looks promising, and funds are available to successfully develop the technology, a positron-powered spaceship would have a couple advantages over the existing plans for a human mission to Mars, called the Mars Reference Mission.
"The most significant advantage is more safety," said Dr. Gerald Smith of Positronics Research, LLC, in Santa Fe, New Mexico. The current Reference Mission calls for a nuclear reactor to propel the spaceship to Mars. This is desirable because nuclear propulsion reduces travel time to Mars, increasing safety for the crew by reducing their exposure to cosmic rays. Also, a chemically-powered spacecraft weighs much more and costs a lot more to launch. The reactor also provides ample power for the three-year mission. But nuclear reactors are complex, so more things could potentially go wrong during the mission. "However, the positron reactor offers the same advantages but is relatively simple," said Smith, lead researcher for the NIAC study.
Also, nuclear reactors are radioactive even after their fuel is used up. After the ship arrives at Mars, Reference Mission plans are to direct the reactor into an orbit that will not encounter Earth for at least a million years, when the residual radiation will be reduced to safe levels. However, there is no leftover radiation in a positron reactor after the fuel is used up, so there is no safety concern if the spent positron reactor should accidentally re-enter Earth's atmosphere, according to the team.
It will be safer to launch as well. If a rocket carrying a nuclear reactor explodes, it could release radioactive particles into the atmosphere. "Our positron spacecraft would release a flash of gamma-rays if it exploded, but the gamma rays would be gone in an instant. There would be no radioactive particles to drift on the wind. The flash would also be confined to a relatively small area. The danger zone would be about a kilometer (about a half-mile) around the spacecraft. An ordinary large chemically-powered rocket has a danger zone of about the same size, due to the big fireball that would result from its explosion," said Smith.
Another significant advantage is speed. The Reference Mission spacecraft would take astronauts to Mars in about 180 days. "Our advanced designs, like the gas core and the ablative engine concepts, could take astronauts to Mars in half that time, and perhaps even in as little as 45 days," said Kirby Meyer, an engineer with Positronics Research on the study.
Advanced engines do this by running hot, which increases their efficiency or "specific impulse" (Isp). Isp is the "miles per gallon" of rocketry: the higher the Isp, the faster you can go before you use up your fuel supply. The best chemical rockets, like NASA's Space Shuttle main engine, max out at around 450 seconds, which means a pound of fuel will produce a pound of thrust for 450 seconds. A nuclear or positron reactor can make over 900 seconds. The ablative engine, which slowly vaporizes itself to produce thrust, could go as high as 5,000 seconds.
One technical challenge to making a positron spacecraft a reality is the cost to produce the positrons. Because of its spectacular effect on normal matter, there is not a lot of antimatter sitting around. In space, it is created in collisions of high-speed particles called cosmic rays. On Earth, it has to be created in particle accelerators, immense machines that smash atoms together. The machines are normally used to discover how the universe works on a deep, fundamental level, but they can be harnessed as antimatter factories.
"A rough estimate to produce the 10 milligrams of positrons needed for a human Mars mission is about 250 million dollars using technology that is currently under development," said Smith. This cost might seem high, but it has to be considered against the extra cost to launch a heavier chemical rocket (current launch costs are about $10,000 per pound) or the cost to fuel and make safe a nuclear reactor. "Based on the experience with nuclear technology, it seems reasonable to expect positron production cost to go down with more research," added Smith.
Another challenge is storing enough positrons in a small space. Because they annihilate normal matter, you can't just stuff them in a bottle. Instead, they have to be contained with electric and magnetic fields. "We feel confident that with a dedicated research and development program, these challenges can be overcome," said Smith.
If this is so, perhaps the first humans to reach Mars will arrive in spaceships powered by the same source that fired starships across the universes of our science fiction dreams.
Source: NASA Goddard Space Flight Center, by Bill Steigerwald

Graphite-based circuitry may be foundation for devices that handle electrons as waves

New electronics

A study of how electrons behave in circuitry made from ultrathin layers of graphite – known as graphene – suggests the material could provide the foundation for a new generation of nanometer scale devices that manipulate electrons as waves – much like photonic systems control light waves.
In a paper published April 13 in Science Express, an online advance publication of the journal Science, researchers at the Georgia Institute of Technology and the Centre National de la Recherche Scientifique (CNRS) in France report measuring electron transport properties in graphene that are comparable those seen in carbon nanotubes. Unlike carbon nanotubes, however, graphene circuitry can be produced using established microelectronics techniques, allowing researchers to envision a "road map" for future high-volume production.
"We have shown that we can make the graphene material, that we can pattern it, and that its transport properties are very good," said Walt de Heer, a professor in Georgia Tech's School of Physics. "The material has high electron mobility, which means electrons can move through it without much scattering or resistance. It is also coherent, which means electrons move through the graphene much like light travels through waveguides."  The results should encourage further development of graphene-based electronics, though de Heer cautions that practical devices may be a decade away.
"This is really the first step in a very long path," he said. "We are at the proof-of principle stage, comparable to where transistors were in the late 1940s. We have a lot to do, but I believe this technology will advance rapidly."
The research, begun by de Heer's team in 2001, is supported by the U.S. National Science Foundation and the Intel Corporation.
In their paper, the researchers report seeing evidence of quantum confinement effects in their graphene circuitry, meaning electrons can move through it as waves. "The graphene ribbons we create are really like waveguides for electrons," de Heer said.
Because carbon nanotubes conduct electricity with virtually no resistance, they have attracted strong interest for use in transistors and other devices. However, the discrete nature of nanotubes – and variability in their properties – pose significant obstacles to their use in practical devices. By contrast, continuous graphene circuitry can be produced using standard microelectronics processing techniques.
"Nanotubes are simply graphene that has been rolled into a cylindrical shape," de Heer explained. "Using narrow ribbons of graphene, we can get all the properties of nanotubes because those properties are due to the graphene and the confinement of the electrons, not the nanotube structures."
De Heer envisions using the graphene electronics for specialized applications, potentially within conventional silicon-based systems.
"We have shown that we can interconnect graphene, put current into it, and take current out," he said. "We have a very promising electronic material. We see graphene as a platform, a canvas on which we can work."
De Heer and collaborators Claire Berger, Zhimin Song, Xuebin Li, Xiaosong Wu, Nate Brown, Tianbo Li, Joanna Hass, Alexei Marchenkov, Edward Conrad and Phillip First of Georgia Tech and Didier Mayou and Cecile Naud of CNRS start with a wafer of silicon carbide, a material made up of silicon and carbon atoms. By heating the wafer in a high vacuum, they drive silicon atoms from the surface, leaving a thin continuous layer of graphene.
Next, they spin-coat onto the surface a photo-resist material of the kind used in established microelectronics techniques. Using electron-beam lithography, they produce patterns on the surface, then use conventional etching processes to remove unwanted graphene.
"We are doing lithography, which is completely familiar to those who work in microelectronics," said de Heer. "It's exactly what is done in microelectronics, but with a different material. That is the appeal of this process."
Using electron beam lithography in Georgia Tech's Microelectronics Research Center, they've created feature sizes as small as 80 nanometers. The graphene circuitry demonstrates high electron mobility – up to 25,000 square centimeters per volt-second, showing that electrons move with little scattering. The researchers expect to see ballistic transport at room temperature when they make structures small enough.
So far, they have built an all graphene planar field-effect transistor. The side-gated device produces a change in resistance through its channel when voltage is applied to the gate. However, this first device has a substantial current leak, which the team expects to eliminate with minor processing adjustments.
The researchers have also built a working quantum interference device, a ring-shaped structure that would be useful in manipulating electronic waves.
The key to properties of the new circuitry is the width of the ribbons, which confine the electrons in a quantum effect similar to that seen in carbon nanotubes. The width of the ribbon controls the material's band-gap. Other structures, such as sensing molecules, could be attached to the edges of the ribbons, which are normally passivated by hydrogen atoms.
Beyond coherence and high electron mobility, the researchers note that the speed of electrons through the graphene is independent of energy – just like light waves. The electrons also possess the properties of Dirac particles, which allow them to travel significant distances without scattering.
Among the challenges ahead is improving the techniques for patterning the graphene, since electron transport is affected by the smoothness of edges in the circuitry. Researchers will also have to understand the material's fundamental properties, which could still contain "show-stoppers" that might make the material impractical.
De Heer has seen hints that graphene may offer some surprises. "We already have indications of some new and surprising electronic properties of this material," he said. "It is doing things that we have never seen in two-dimensional materials before."

Sonofusion in question

University to Investigate Fusion Study
by Kenneth Chang
The New York Times
Purdue University has opened an investigation into “extremely serious” concerns regarding the research of a professor who said he had produced nuclear fusion in a tabletop experiment, the university announced yesterday.
Fusion is the process the sun uses to produce heat and light, and scientists led by Rusi P. Taleyarkhan, a professor of nuclear engineering at Purdue, said they were able to achieve the same feat by blasting a container of liquid solvent with strong ultrasonic vibrations.
The vibrations, they said, collapsed tiny gas bubbles in the liquid, heating them to millions of degrees, hot enough to initiate fusion. If true, the phenomenon, often called sonofusion or bubble fusion, could have far-reaching applications, including the generation of energy.
The research first appeared in 2002 in the journal Science, but controversy had erupted even before publication. Dr. Taleyarkhan, then a senior scientist at Oak Ridge National Laboratory in Tennessee, reported the detection of neutrons, which are the telltale signs of fusion, but two other scientists at Oak Ridge, using their own detectors, said they saw no signs of neutrons.
Dr. Taleyarkhan, who joined the Purdue faculty in 2003, and his colleagues have published two additional papers in major physics journals, amid the continuing skepticism of other scientists. No other scientists have been able to reproduce the findings.
The university began a review of the research and the accusations last week, Sally Mason, the university provost, said in a statement. “The research claims involved are very significant,” Dr. Mason said, “and the concerns expressed are extremely serious.”
Dr. Mason said that the review was being conducted by Purdue’s Office of the Vice President of Research and that the results would be announced publicly.
Dr. Taleyarkhan did not return phone calls or respond to an e-mail message seeking comment.
Meanwhile, Brian Naranjo, a graduate student at the University of California, Los Angeles, said his analysis of data from the last scientific paper that was published by Dr. Taleyarkhan’s group showed a chance of less than one in 10 million that the emission pattern could have been generated by fusion.
Instead, Mr. Naranjo said that the pattern of particles seen in the experiment much more closely matched that given off by californium, a radioactive element that is used in Dr. Taleyarkhan’s laboratory. With $350,000 from the Defense Department, Seth J. Putterman, a professor of physics at U.C.L.A. and the thesis adviser to Mr. Naranjo, has tried to build a replica of Dr. Taleyarkhan’s apparatus and has not seen any signs of fusion.
Dr. Putterman said he told Dr. Taleyarkhan of the calculations last week on a visit to Purdue. “He didn’t have any clear answers,” Dr. Putterman said. “From my perspective, his answers were not satisfactory.”
Californium is present in Dr. Taleyarkhan’s laboratory, stored in a closet about 15 feet from the experiment – close enough to generate the results reported in Dr. Taleyarkhan’s paper if it had been stored improperly.

Easy Up, Not-So-Easy Down - Composite bridge building

Using new fiberglass-polymer materials, contractors in Springfield, Mo., have just subjected a decaying, 70-year-old bridge to a makeover that was as quick as it was dramatic.
Instead of snarling traffic for two to three weeks while they repaired the crumbling deck, girders and guardrails by conventional methods--laying plywood, tying steel rebar and pouring concrete--the workers used pre-fabricated plates and cages developed by a National Science Foundation (NSF)-supported university-industry partnership to finish the job in a mere five days. 
The NSF's Repair of Buildings and Bridges with Composites Industry-University Cooperative Research Center is based at the University of Missouri at Rolla and North Carolina State University.  The Missouri researchers joined with their industry partners and colleagues at the University of Wisconsin at Madison to develop the new construction solution.
The target of the makeover, an old bridge on Farm Road 148 near Springfield, was one of as many as 156,000 U.S. bridges in need of repair. In fact, it was posted, meaning that local officials had imposed a vehicle weight limit due to the dangerous bridge conditions. Now, however, a fresh layer of concrete conceals the technology responsible for the rapid replacement of the bridge’s crumbling deck and guardrails.
"A key to tackling the challenge of making thousands of deficient bridges in the nation fully operational and safe again is the development of convenient solutions for the rapid construction of long-lasting bridges," says Fabio Matta, a Ph.D. candidate in structural engineering who helped develop the new construction system.  "Advanced composites make the margin for improvements exceptional," he added.
The fiberglass-polymer composites are strong enough to endure several decades of traffic--and unlike steel, will resist the ravages of salt and other corrosive de-icers for just as long. Due to the lightweight and prefabricated nature of the materials, moreover, workers can put the structures in place quickly, saving both time and commuter headaches.
"Since its inception in 1998, we have worked with our NSF I/UCRC partners to provide solutions for our ageing infrastructure," says Antonio Nanni, director of the Missouri center.
"We have demonstrated the economical and technical feasibility of several very attractive technologies," Nanni added. "Their full deployment will become possible only with the modification of existing codes and standards.  It is a long process, but we are seeing light at the end of the tunnel."
The original news release can be found here.

Professor Predicts Human Time Travel This Century

from PhysOrg.com
With a brilliant idea and equations based on Einstein’s relativity theories, Ronald Mallett from the University of Connecticut has devised an experiment to observe a time traveling neutron in a circulating light beam. While his team still needs funding for the project, Mallett calculates that the possibility of time travel using this method could be verified within a decade. [...]

Scientist Creates Liquid Crystals with High Metal Content

Researchers at North Carolina State University have successfully engineered liquid crystals that contain very high concentrations of metals – potentially paving the way toward the creation of “magnetic liquids” and liquid crystals that may have important ramifications for semi-conductor and solar energy research.

Dr. James Martin, professor of chemistry in NC State’s College of Physical and Mathematical Sciences, along with departmental colleague Dr. Jaap Folmer and a team of graduate students, engineered liquid crystals with an inorganic content of up to 80 percent, more than twice the ratio of previously observed organic liquid crystals with incorporated metals, or metallomesogens.

The findings appear in the April edition of Nature Materials.

Liquid crystals are prized for their unique optical and self-healing properties. They generally consist of toothpick- or pancake-shaped molecules that align in the liquid state because of their shape. By using electric fields to manipulate the orientation of liquid crystal molecules, scientists can control whether or not light can pass through the liquid crystalline material. Without such liquid crystals, everyday items we take for granted – such as flat-panel computer displays or LCD watches – would not exist.

The most commonly known liquid crystals are organic molecules composed of carbon,
nitrogen or oxygen. Adding inorganic materials, or metals, to these liquid crystals in order to potentially access electronic or magnetic properties was problematic because the structure of these molecules made it difficult to achieve a metallic concentration high enough to be useful.

Martin’s team recognized that to achieve high metal content in liquid crystals, it was necessary to start with an inorganic network from which liquid-crystalline molecules could be designed. They have achieved success with this strategy by using surfactants, like those in laundry detergent, to help engineer liquid crystalline structure from various inorganic networks. The ratios of surfactant and inorganic components used in preparation of these materials give the scientists a great deal of control over the structure of liquids.

The research could lead not only to the creation of new liquid crystals, but also to a new understanding of the ways in which all liquid structures – even membranes and proteins – are organized.

“Liquids are not random structures, but rather highly organized structures that we can control and shape at the atomic and molecular levels,” says Martin. “When we start exploring the ways in which we can organize these liquids, we can create totally new materials, and access different properties within each material.”

Source: North Carolina State University

Smart glasses switch focus in an instant

NewScientist.com news service
Stu Hutson

This prototype might get their wearer noticed, but future designs aim to be indistinguishable from regular glasses (Image: PixelOptics)
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Glasses that change from "long distance" to "reading" mode at the flick of a switch could prove a revelation for many wearers.
Researchers have developed a prototype that uses liquid crystals to change focus in an instant, thus preventing the eye strain induced by wearing conventional bifocal glasses. Focusing through specific portions of a bifocal lens causes many users to become dizzy or disoriented, while others report increased eye fatigue.
"Bifocals effectively work the same way they have since they were invented by Benjamin Franklin," says Nasser Peyghambarian, a professor of optical sciences at Arizona State University, US, who helped develop the "dynamic" glasses. "But as any of more than 40 million people in America who need bifocals know, they're a pain."
Fresnel lens
The dynamic glasses change focus using a 5-micron-thick layer of nematic liquid crystal, sandwiched between two pieces of glass. Molecules of the liquid crystal reorient themselves when exposed to an electric field and the researchers used this to create a type of dynamic Fresnel lens.
In a normal Fresnel lens, concentric rings are carved into a piece of glass causing light to become focused in a similar way to a conventional lens. Dynamic glasses mimic the Fresnel effect using concentric circles of clear electrodes on the pieces of glass containing the crystal. Activating these electrodes causes the liquid crystal to align into rings and focus light passing through the lens.
A company called PixelOptics, based in Virginia, US, plans to sell glasses containing dynamic lenses commercially within two years. "The prototype is pretty bulky, but when these hit the streets they’ll be virtually indistinguishable from other, very stylish glasses," says Ronald Blum, CEO of PixelOptics.
Infrared laser
PixelOptics first developed the idea of dynamic focusing while working on large lenses for computer screens. Ideally, these would have allowed near-sighted and far-sighted people to read their monitors without their spectacles. "As screens got thinner and thinner, though, the idea became less practical," Blum says. "So instead we decided to move the technology from the computer to the computer user."
The first commercial dynamic glasses will only be able to switch between a person’s normal vision and their "reading" prescription. However, by applying different voltages and by changing the number of current-carrying rings within each lens it should be possible to produce different magnifications using the same lens, researchers say.
Peyghambarian is now working on glasses that can dynamically refocus on whatever the wearer is looking at. These will most probably use an infrared laser built into the bridge of the glasses to determine how far away an object is. "The idea is to put the focusing power found in the lens of a camera on your face all the time," Peyghambarian told New Scientist.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0600850103)