Stronger Than Steel, Novel Metals Are as Moldable as Plastic

Now a team led by Jan Schroers, a materials scientist at Yale University, has shown that some recently developed bulk metallic glasses (BMGs)-metal alloys that have randomly arranged atoms as opposed to the orderly, crystalline structure found in ordinary metals-can be blow molded like plastics into complex shapes that can't be achieved using regular metal, yet without sacrificing the strength or durability that metal affords. Their findings are described online in the current issue of the journalMaterials Today.

"These alloys look like ordinary metal but can be blow molded just as cheaply and as easily as plastic," Schroers said. So far the team has created a number of complex shapes-including seamless metallic bottles, watch cases, miniature resonators and biomedical implants-that can be molded in less than a minute and are twice as strong as typical steel.

The materials cost about the same as high-end steel, Schroers said, but can be processed as cheaply as plastic. The alloys are made up of different metals, including zirconium, nickel, titanium and copper.

The team blow molded the alloys at low temperatures and low pressures, where the bulk metallic glass softens dramatically and flows as easily as plastic but without crystallizing like regular metal. It's the low temperatures and low pressures that allowed the team to shape the BMGs with unprecedented ease, versatility and precision, Schroers said. In order to carefully control and maintain the ideal temperature for blow molding, the team shaped the BMGs in a vacuum or in fluid.

"The trick is to avoid friction typically present in other forming techniques," Schroers said."Blow molding completely eliminates friction, allowing us to create any number of complicated shapes, down to the nanoscale."

Schroers and his team are already using their new processing technique to fabricate miniature resonators for microelectromechanical systems (MEMS)-tiny mechanical devices powered by electricity-as well as gyroscopes and other resonator applications.

In addition, by blow molding the BMGs, the team was able to combine three separate steps in traditional metal processing (shaping, joining and finishing) into one, allowing them to carry out previously cumbersome, time- and energy-intensive processing in less than a minute.

"This could enable a whole new paradigm for shaping metals," Schroers said."The superior properties of BMGs relative to plastics and typical metals, combined with the ease, economy and precision of blow molding, have the potential to impact society just as much as the development of synthetic plastics and their associated processing methods have in the last century."

Other authors of the paper include Thomas M. Hodges and Golden Kumar (Yale University); Hari Raman and A.J. Barnes (SuperformUSA); and Quoc Pham and Theodore A. Waniuk (Liquidmetal Technologies).

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3-D Nanoparticle in Atomic Resolution

New method developed

The chemical and physical properties of nanoparticles are determined by their exact three-dimensional morphology, atomic structure and especially their surface composition. In a study initiated by ETH Zurich scientist Marta Rossell and Empa researcher Rolf Erni, the 3D structure of individual nanoparticles has now successfully been determined on the atomic level. The new technique could help improve our understanding of the characteristic of nanoparticles, including their reactivity and toxicity.

Gentle imaging processing

For their electron-microscopic study, which was published recently in the journalNature,Rossell and Erni prepared silver nanoparticles in an aluminium matrix. The matrix makes it easier to tilt the nanoparticles under the electron beam in different crystallographic orientations whilst protecting the particles from damage by the electron beam. The basic prerequisite for the study was a special electron microscope that reaches a maximum resolution of less than 50 picometres. By way of comparison: the diameter of an atom measures about oneÅngström, i.e. 100 picometres.

To protect the sample further, the electron microscope was set up in such a way as to also yield images at an atomic resolution with a lower accelerating voltage, namely 80 kilovolts. Normally, this kind of microscope -- of which there are only a few in the world -- works at 200 -- 300 kilovolts. The two scientists used a microscope at the Lawrence Berkeley National Laboratory in California for their experiments. The experimental data was complemented with additional electron-microscopic measurements carried out at Empa.

Sharper images

On the basis of these microscopic images, Sandra Van Aert from the University of Antwerp created models that"sharpened" the images and enabled them to be quantified: the refined images made it possible to count the individual silver atoms along different crystallographic directions.

For the three-dimensional reconstruction of the atomic arrangement in the nanoparticle, Rossell and Erni eventually enlisted the help of the tomography specialist Joost Batenburg from Amsterdam, who used the data to tomographically reconstruct the atomic structure of the nanoparticle based on a special mathematical algorithm. Only two images were sufficient to reconstruct the nanoparticle, which consists of 784 atoms."Up until now, only the rough outlines of nanoparticles could be illustrated using many images from different perspectives," says Marta Rossell. Atomic structures, on the other hand, could only be simulated on the computer without an experimental basis.

"Applications for the method, such as characterising doped nanoparticles, are now on the cards," says Rolf Erni. For instance, the method could one day be used to determine which atom configurations become active on the surface of the nanoparticles if they have a toxic or catalytic effect. Rossell stresses that in principle the study can be applied to any type of nanoparticle. The prerequisite, however, is experimental data like that obtained in the study.

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Fingerprints of a Gold Cluster Revealed

However, the first definite information of their atomic structure became available only in 2007 when the group of Roger Kornberg (Chemistry Nobel Laureate 2006) at Stanford University succeeded in making single crystals for X-ray diffractometry containing only one type of a particle having 102 gold atoms and 44 thiolate ligands, the so called Au102(p-MBA)44 particle. The structure was reported inSciencein late 2007 {1}. The theoretical analysis of this and other thiolate-protected gold clusters, led by Professor Hannu Häkkinen at the University of Jyväskylä in Finland, resulted in a theoretical framework that can be used to understand the stability and electronic structure of these particles. This work was reported in theProceedings of the National Academy of Sciencesin 2008 {2}.

Now, researchers in the Department of Chemistry and the Nanoscience Center (NSC) at the University of Jyväskylä, in collaboration with the Kornberg group, report the first full spectroscopic characterisation of the absorption of electromagnetic radiation by the Au102(p-MBA)44 particle in solution and solid phases. The study was published in theJournal of the American Chemical Societyon 24 February 2011 {3}. The spectroscopic study was performed in a large range of electromagnetic spectrum from mid-infrared ("heat absorption") to ultraviolet light.

"The study was technically demanding and could only be made now when the Stanford group has succeeded in refining the synthesis to produce pure Au102(p-MBA)44 product in large quantities," explains Adjunct Professor Mika Pettersson, who led the experimental work at the NSC."We document clear"fingerprint" features in the absorbance spectrum that can be used in the future to benchmark chemical modifications of this particle for various applications. The work also establishes the molecular nature of the clusters by the observation of a band gap of 0.45 eV, in excellent agreement with theory. We were able to analyse these features from large-scale computations using the known structure of Au102(p-MBA)44 and thus fully understand the absorption characteristics of this particle," says Professor Häkkinen.

The other researchers involved in the work are Eero Hulkko, Jaakko Koivisto and Olga Lopez-Acevedo from the University of Jyväskylä. The pure samples of the Au102(p-MBA)44 particle were made by Yael Levi-Kalisman in the Kornberg group. The work at the NSC and the Department of Chemistry at the University of Jyväskylä is funded by the Academy of Finland. The massively parallel computations, using up to 2048 processor cores, were made in the Louhi supercomputer at CSC -- the IT Center for Science.

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Simpler Way of Making Proteins Could Lead to New Nanomedicine Agents

Led by Jianjun Cheng, a professor of materials science and engineering at the University of Illinois, the research team will publish its findings in the Feb. 22 edition of the journalNature Communications.

Materials scientists have been interested in designing large polymer molecules that could be used as building blocks for self-assembling structures. The challenge has been that the molecules generally adopt a globular, spherical shape, limiting their ability to form orderly aggregates. However, polypeptides -- chains of amino acids such as proteins -- can form helical structures. Short polypeptide chains that adopt a spiral shape act like cylindrical rods.

"If you have two rigid rods, one positive and one negative, right next to each other, they're going to stick to each other. If you have a way to put the charge on the surface then they can pack together in a close, compact way, so they form a three-dimensional structure," Cheng said.

However, it is difficult to make helical polypeptides that are water-soluble so they can be used in solution. Polypeptides gain their solubility from side chains -- molecular structures that stem from each amino acid link in the polypeptide chain. Amino acids with positive or negative charges in their side chains are needed to make a polypeptide disperse in water.

The problem arises when chains with charged side chains form helical structures. The charges cause a strong repulsion between the side chains, which destabilizes the helical conformation. This causes water-soluble polypeptides to form random coil structures instead of the desired helices.

In exploring solutions to the riddle of helical, water-soluble polypeptides, researchers have tried several complicated methods. For example, scientists have attempted grafting highly water-soluble chemicals to the side chains to increase the polypeptides' overall solubility, or creating helices with charges only on one side.

"You can achieve the helical structure and the solubility but you have to design the helical structure in a very special way. The peptide design needs a very specific sequence. Then you're very limited in the type of polypeptide you can build, and it's not easy to design or handle these polypeptides," Cheng said.

In contrast, Cheng's group developed a very straightforward solution. Since the close proximity of the charges causes the repulsion that disrupts the helix, the researchers simply elongated the side chains, moving the charges farther from the backbone and giving them more freedom to keep their distance from one another.

The researchers observed that as they increased the length of the side chains with charges on the end, the polypeptides' propensity for forming helices also increased.

"It's such a simple idea -- move the charge away from the backbone," Cheng said."It's not difficult at all to make the longer side chains, and it has amazing properties for winding up helical structures simply by pushing the distance between the charge and the backbone."

The group found that not only do polypeptides with long side chains form helices, they display remarkable stability even when compared to non-charged helices. The helices seem immune to temperature, pH, and other denaturing agents that would unwind most polypeptides.

This may explain why amino acids with large hydrophobic side chains are not found in nature. Such immutability would preclude dynamic winding and unwinding of protein structures, which is essential to many biological processes. However, rigid stability is a desirable trait for the types of applications Cheng's group explores: nanostructures for drug and gene delivery, particularly targeting cancerous tumors and stem cells.

"We want to test the correlation of the lengths of the helices and the circulation in the body to see what's the impact of the shape and the charge and the side chains for clearance in the body," Cheng said."Recent studies show that the aspect ratio of the nanostructures -- spherical structures versus tubes -- has a huge impact on their penetration of tumor tissues and circulation half-lives in the body."

Cheng plans to create a library of short helical polypeptides of varying backbone lengths, side chain lengths and types of charge. He hopes to simplify the chemistry even further and make the materials widely accessible. His lab already has demonstrated that helical structures can be effective gene delivery and membrane transduction agents, and building the library of soluble helical molecules will allow further investigation of tailoring such nanostructures for specific biomedical applications.

The National Science Foundation and the National Institutes of Health supported this work. Illinois co-authors were graduate students Hua Lu and Yugang Bai and undergraduate student Jason Lang."Hua Lu, a fifth year graduate student in my group, is the first author of the publication and made the most significant contribution to this work," Cheng said. Yao Lin and Jin Wang, of the University of Connecticut, and professor Shiyong Liu, of the University of Science and Technology of China, also collaborated with Cheng's group on the paper.

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New Stretchable Solar Cells Will Power Artificial Electronic 'Super Skin'

Super skin, indeed.

"With artificial skin, we can basically incorporate any function we desire," said Bao, a professor of chemical engineering."That is why I call our skin 'super skin.' It is much more than what we think of as normal skin."

The foundation for the artificial skin is a flexible organic transistor, made with flexible polymers and carbon-based materials. To allow touch sensing, the transistor contains a thin, highly elastic rubber layer, molded into a grid of tiny inverted pyramids. When pressed, this layer changes thickness, which changes the current flow through the transistor. The sensors have from several hundred thousand to 25 million pyramids per square centimeter, corresponding to the desired level of sensitivity.

To sense a particular biological molecule, the surface of the transistor has to be coated with another molecule to which the first one will bind when it comes into contact. The coating layer only needs to be a nanometer or two thick.

"Depending on what kind of material we put on the sensors and how we modify the semiconducting material in the transistor, we can adjust the sensors to sense chemicals or biological material," she said.

Bao's team has successfully demonstrated the concept by detecting a certain kind of DNA. The researchers are now working on extending the technique to detect proteins, which could prove useful for medical diagnostics purposes.

"For any particular disease, there are usually one or more specific proteins associated with it -- called biomarkers -- that are akin to a 'smoking gun,' and detecting those protein biomarkers will allow us to diagnose the disease," Bao said.

The same approach would allow the sensors to detect chemicals, she said. By adjusting aspects of the transistor structure, the super skin can detect chemical substances in either vapor or liquid environments.

Regardless of what the sensors are detecting, they have to transmit electronic signals to get their data to the processing center, whether it is a human brain or a computer.

Having the sensors run on the sun's energy makes generating the needed power simpler than using batteries or hooking up to the electrical grid, allowing the sensors to be lighter and more mobile. And having solar cells that are stretchable opens up other applications.

A recent research paper by Bao, describing the stretchable solar cells, will appear in an upcoming issue ofAdvanced Materials. The paper details the ability of the cells to be stretched in one direction, but she said her group has since demonstrated that the cells can be designed to stretch along two axes.

The cells have a wavy microstructure that extends like an accordion when stretched. A liquid metal electrode conforms to the wavy surface of the device in both its relaxed and stretched states.

"One of the applications where stretchable solar cells would be useful is in fabrics for uniforms and other clothes," said Darren Lipomi, a graduate student in chemical engineering in Bao's lab and lead author of the paper.

"There are parts of the body, at the elbow for example, where movement stretches the skin and clothes," he said."A device that was only flexible, not stretchable, would crack if bonded to parts of machines or of the body that extend when moved." Stretchability would be useful in bonding solar cells to curved surfaces without cracking or wrinkling, such as the exteriors of cars, lenses and architectural elements.

The solar cells continue to generate electricity while they are stretched out, producing a continuous flow of electricity for data transmission from the sensors.

Bao said she sees the super skin as much more than a super mimic of human skin; it could allow robots or other devices to perform functions beyond what human skin can do.

"You can imagine a robot hand that can be used to touch some liquid and detect certain markers or a certain protein that is associated with some kind of disease and the robot will be able to effectively say, 'Oh, this person has that disease,'" she said."Or the robot might touch the sweat from somebody and be able to say, 'Oh, this person is drunk.'"

Finally, Bao has figured out how to replace the materials used in earlier versions of the transistor with biodegradable materials. Now, not only will the super skin be more versatile and powerful, it will also be more eco-friendly.

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'Fingerprints' Match Molecular Simulations With Reality

ORNL's Jeremy Smith collaborated on devising a method -- dynamical fingerprints -- that reconciles the different signals between experiments and computer simulations to strengthen analyses of molecules in motion. The research will be published in theProceedings of the National Academy of Sciences.

"Experiments tend to produce relatively simple and smooth-looking signals, as they only 'see' a molecule's motions at low resolution," said Smith, who directs ORNL's Center for Molecular Biophysics and holds a Governor's Chair at the University of Tennessee."In contrast, data from a supercomputer simulation are complex and difficult to analyze, as the atoms move around in the simulation in a multitude of jumps, wiggles and jiggles. How to reconcile these different views of the same phenomenon has been a long-standing problem."

The new method solves the problem by calculating peaks within the simulated and experimental data, creating distinct"dynamical fingerprints." The technique, conceived by Smith's former graduate student Frank Noe, now at the Free University of Berlin, can then link the two datasets.

Supercomputer simulations and modeling capabilities can add a layer of complexity missing from many types of molecular experiments.

"When we started the research, we had hoped to find a way to use computer simulation to tell us which molecular motions the experiment actually sees," Smith said."When we were finished we got much more -- a method that could also tell us which other experiments should be done to see all the other motions present in the simulation. This method should allow major facilities like the ORNL's Spallation Neutron Source to be used more efficiently."

Combining the power of simulations and experiments will help researchers tackle scientific challenges in areas like biofuels, drug development, materials design and fundamental biological processes, which require a thorough understanding of how molecules move and interact.

"Many important things in science depend on atoms and molecules moving," Smith said."We want to create movies of molecules in motion and check experimentally if these motions are actually happening."

"The aim is to seamlessly integrate supercomputing with the Spallation Neutron Source so as to make full use of the major facilities we have here at ORNL for bioenergy and materials science development," Smith said.

The collaborative work included researchers from L'Aquila, Italy, Wuerzburg and Bielefeld, Germany, and the University of California at Berkeley. The research was funded in part by a Scientific Discovery through Advanced Computing grant from the DOE Office of Science.

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MIT Engineers Design New Nanoparticle That Could Lead to Vaccines for HIV, Malaria, Other Diseases

The new particles, described in the Feb. 20 issue ofNature Materials, consist of concentric fatty spheres that can carry synthetic versions of proteins normally produced by viruses. These synthetic particles elicit a strong immune response -- comparable to that produced by live virus vaccines -- but should be much safer, says Darrell Irvine, corresponding author of the paper and an associate professor of materials science and engineering and biological engineering.

Such particles could help scientists develop vaccines against cancer as well as infectious diseases. In collaboration with scientists at the Walter Reed Army Institute of Research, Irvine and his students are now testing the nanoparticles' ability to deliver an experimental malaria vaccine in mice.

Vaccines protect the body by exposing it to an infectious agent that primes the immune system to respond quickly when it encounters the pathogen again. In many cases, such as with the polio and smallpox vaccines, a dead or disabled form of the virus is used. Other vaccines, such as the diphtheria vaccine, consist of a synthetic version of a protein or other molecule normally made by the pathogen.

When designing a vaccine, scientists try to provoke at least one of the human body's two major players in the immune response: T cells, which attack body cells that have been infected with a pathogen; or B cells, which secrete antibodies that target viruses or bacteria present in the blood and other body fluids.

For diseases in which the pathogen tends to stay inside cells, such as HIV, a strong response from a type of T cell known as"killer" T cell is required. The best way to provoke these cells into action is to use a killed or disabled virus, but that cannot be done with HIV because it's difficult to render the virus harmless.

To get around the danger of using live viruses, scientists are working on synthetic vaccines for HIV and other viral infections such as hepatitis B. However, these vaccines, while safer, do not elicit a very strong T cell response. Recently, scientists have tried encasing the vaccines in fatty droplets called liposomes, which could help promote T cell responses by packaging the protein in a virus-like particle. However, these liposomes have poor stability in blood and body fluids.

Irvine, who is a member of MIT's David H. Koch Institute for Integrative Cancer Research, decided to build on the liposome approach by packaging many of the droplets together in concentric spheres. Once the liposomes are fused together, adjacent liposome walls are chemically"stapled" to each other, making the structure more stable and less likely to break down too quickly following injection. However, once the nanoparticles are absorbed by a cell, they degrade quickly, releasing the vaccine and provoking a T cell response.

In tests with mice, Irvine and his colleagues used the nanoparticles to deliver a protein called ovalbumin, an egg-white protein commonly used in immunology studies because biochemical tools are available to track the immune response to this molecule. They found that three immunizations of low doses of the vaccine produced a strong T cell response -- after immunization, up to 30 percent of all killer T cells in the mice were specific to the vaccine protein.

That is one of the strongest T cell responses generated by a protein vaccine, and comparable to strong viral vaccines, but without the safety concerns of live viruses, says Irvine. Importantly, the particles also elicit a strong antibody response. Niren Murthy, associate professor at Georgia Institute of Technology, says the new particles represent"a fairly large advance," though he says that more experiments are needed to show that they can elicit an immune response against human disease, in human subjects."There's definitely enough potential to be worth exploring it with more sophisticated and expensive experiments," he says.

In addition to the malaria studies with scientists at Walter Reed, Irvine is also working on developing the nanoparticles to deliver cancer vaccines and HIV vaccines. Translation of this approach to HIV is being done in collaboration with colleagues at the Ragon Institute of MIT, Harvard and Massachusetts General Hospital. The institute, which funded this study along with the Gates Foundation, Department of Defense and National Institutes of Health, was established in 2009 with the goal of developing an HIV vaccine.

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World's Smallest Magnetic Field Sensor: Researchers Explore Using Organic Molecules as Electronic Components

For the first time, a team of scientists from KIT and the Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS) have now succeeded in combining the concepts of spin electronics and molecular electronics in a single component consisting of a single molecule. Components based on this principle have a special potential, as they allow for the production of very small and highly efficient magnetic field sensors for read heads in hard disks or for non-volatile memories in order to further increase reading speed and data density.

Use of organic molecules as electronic components is being investigated extensively at the moment. Miniaturization is associated with the problem of the information being encoded with the help of the charge of the electron (current on or off). However, this requires a relatively high amount of energy. In spin electronics, the information is encoded in the intrinsic rotation of the electron, the spin. The advantage is that the spin is maintained even when switching off current supply, which means that the component can store information without any energy consumption.

The German-French research team has now combined these concepts. The organic molecule H₂-phthalocyanin that is also used as blue dye in ball pens exhibits a strong dependence of its resistance, if it is trapped between spin-polarized, i.e. magnetic electrodes. This effect was first observed in purely metal contacts by Albert Fert and Peter Grünberg. It is referred to as giant magnetoresistance and was acknowledged by the Nobel Prize for Physics in 2007.

The giant magnetoresistance effect on single molecules was demonstrated at KIT within the framework of a combined experimental and theoretical project of CFN and a German-French graduate school in cooperation with the IPCMS, Strasbourg. The results of the scientists are now presented in the journalNature Nanotechnology.

Karlsruhe Institute of Technology (KIT) is a public corporation and state institution of Baden-Wuerttemberg, Germany. It fulfills the mission of a university and the mission of a national research center of the Helmholtz Association. KIT focuses on a knowledge triangle that links the tasks of research, teaching, and innovation.

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Manipulating Molecules for a New Breed of Electronics

Such control may eventually play a role in the design of ultra-tiny electrical gadgets, created to perform myriad useful tasks, from biological and chemical sensing to improving telecommunications and computer memory.

Tao leads a research team used to dealing with the challenges entailed in creating electrical devices of this size, where quirky effects of the quantum world often dominate device behavior. As Tao explains, one such issue is defining and controlling the electrical conductance of a single molecule, attached to a pair of gold electrodes.

"Some molecules have unusual electromechanical properties, which are unlike silicon-based materials. A molecule can also recognize other molecules via specific interactions." These unique properties can offer tremendous functional flexibility to designers of nanoscale devices.

In the current research, Tao examines the electromechanical properties of single molecules sandwiched between conducting electrodes. When a voltage is applied, a resulting flow of current can be measured. A particular type of molecule, known as pentaphenylene, was used and its electrical conductance examined.

Tao's group was able to vary the conductance by as much as an order of magnitude, simply by changing the orientation of the molecule with respect to the electrode surfaces. Specifically, the molecule's tilt angle was altered, with conductance rising as the distance separating the electrodes decreased, and reaching a maximum when the molecule was poised between the electrodes at 90 degrees.

The reason for the dramatic fluctuation in conductance has to do with the so-called pi orbitals of the electrons making up the molecules, and their interaction with electron orbitals in the attached electrodes. As Tao notes, pi orbitals may be thought of as electron clouds, protruding perpendicularly from either side of the plane of the molecule. When the tilt angle of a molecule trapped between two electrodes is altered, these pi orbitals can come in contact and blend with electron orbitals contained in the gold electrode -- a process known as lateral coupling. This lateral coupling of orbitals has the effect of increasing conductance.

In the case of the pentaphenylene molecule, the lateral coupling effect was pronounced, with conductance levels increasing up to 10 times as the lateral coupling of orbitals came into greater play. In contrast, the tetraphenyl molecule used as a control for the experiments did not exhibit lateral coupling and conductance values remained constant, regardless of the tilt angle applied to the molecule. Tao says that molecules can now be designed to either exploit or minimize lateral coupling effects of orbitals, thereby permitting the fine-tuning of conductance properties, based on an application's specific requirements.

A further self-check on the conductance results was carried out using a modulation method. Here, the molecule's position was jiggled in 3 spatial directions and the conductance values observed. Only when these rapid perturbations specifically changed the tilt angle of the molecule relative to the electrode were conductance values altered, indicating that lateral coupling of electron orbitals was indeed responsible for the effect. Tao also suggests that this modulation technique may be broadly applied as a new method for evaluating conductance changes in molecular-scale systems.

The research was supported by the Department of Energy -- Basic Energy Science program.

In addition to directing the Biodesign Institute's Center for Bioelectronics and Biosensors, Tao is a professor in the School of Electrical, Computer, and Energy Engineering, at ASU's Ira A. Fulton Schools of Engineering, and an affiliated professor of chemistry and biochemistry, physics and material engineering.

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Atom-Thick Sheets Unlock Future Technologies

An international team, led by Oxford University and Trinity College Dublin scientists, has invented a versatile method for creating these one-atom thick 'nanosheets' from a range of materials using mild ultrasonic pulses, like those generated by jewellery cleaning devices, and common solvents. The new method is simple, fast, and inexpensive, and could be scaled up to work on an industrial scale.

The team publish a report of the research in this week'sScience.

Each one-millimetre-thick layer of graphite is made up of around three million layers of graphene -- a flat sheet of carbon one atom thick -- stacked one on top of the other.

'Because of its extraordinary electronic properties graphene has been getting all the attention, including a recent Nobel Prize, as physicists hope that it might, one day, compete with silicon in electronics,' said Dr Valeria Nicolosi of Oxford University's Department of Materials, who led the research with Professor Jonathan Coleman of Trinity College Dublin. 'But in fact there are hundreds of other layered materials that could enable us to create powerful new technologies.'

Professor Coleman, of Trinity College Dublin, said: 'These novel materials have chemical and electronic properties which are well suited for applications in new electronic devices, super-strong composite materials and energy generation and storage. In particular, this research represents a major breakthrough towards the development of efficient thermoelectric materials.'

There are over 150 of these exotic layered materials -- such as Boron Nitride, Molybdenum disulfide, and Tungsten disulfide -- that have the potential to be metallic, semi-metallic or semiconducting depending on their chemical composition and how their atoms are arranged.

For decades researchers have tried to create nanosheets of these kind of materials as arranging them in atom-thick layers would enable us to unlock their unusual electronic and thermoelectric properties. However, all previous methods were extremely time consuming and laborious and the resulting materials were fragile and unsuited to most applications.

'Our new method offers low-costs, a very high yield and a very large throughput: within a couple of hours, and with just 1 mg of material, billions and billions of one-atom-thick graphene-like nanosheets can be made at the same time from a wide variety of exotic layered materials,' said Dr Nicolosi.

Nanosheets created using this method can be sprayed onto the surface of other materials, such as silicon, to produce 'hybrid films' which, potentially, enable their exotic abilities to be integrated with conventional technologies. Such films could be used to construct, among other things, new designs of computing devices, sensors or batteries.

The work was conducted by a team including scientists from Oxford University, Trinity College Dublin, Imperial College London, Korea University, and Texas A&M University (USA).

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Low-Cost, Nanometer-Sized Drug Holds Promise for Treatment of Chronic Diabetes and Burn Wounds

Diabetes is a rapidly growing medical problem affecting close to 3 percent of the world’s population. Poor blood circulation arising from diabetes often results in skin wounds which do not heal, causing pain, infection and at times amputation of limbs. 

Several proteins, called growth factors, have been found to speed up the healing process, however purifying these growth factor proteins is very expensive, and they do not last long on the injured site. 

Now, scientists at the Hebrew University and Harvard involved in the project have used genetic engineering to produce a“robotic” growth factor protein that responds to temperature. Increasing the temperature causes dozens of these proteins to fold together into a nanoparticle that is more than 200 times smaller than a single hair.

This behavior greatly simplifies protein purification, making it very inexpensive to produce. It also enables the growth factor to be confined and to remain at the burn or wound site. The scientists refer to their discovery as robotic, since just as robots are machines that respond to their environment by carrying out a specific activity, so too this protein they have developed responds and reacts to heat. 

The experimental drug, which ha been developed by the research group as a topical ointment, has been patented and thus far has been used to treat chronic wounds in diabetic mice, dramatically increasing the healing rate.  The goal is to proceed to human clinical trials at some future date after future tests and refinements.

An article on the project has been published online in theProceedings of the National Academy of Sciences. The authors are Dr. Yaakov Nahmias, director of the Center for Bioengineering in the Service of Humanity at the Hebrew University of Jerusalem; Dr. Zaki Megeed, Prof. Robert Sheridan and Prof. Martin L. Yarmush of the Harvard Medical School and Shriners Hospitals for Children; Prof. Piyush Koria of the University of South Florida; and Dr. Hiroshi Yagi and Dr. Yuko Kitagawa of the Keio University School of Medicine in Japan.

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Scientists Elevate Warfighter Readiness Against Invisible Threats

A research team, led by Drs. Joshua Caldwell and Orest Glembocki, scientists at the U.S. Naval Research Laboratory, Electronic Science and Technology Division, has overcome this limitation with surface enhanced Raman scattering (SERS) using optically stimulated plasmon oscillations in nanostructured substrates.

Shown to provide enhancements of the Raman signal, large-area gold (Au) coated silicon (Si) nanopillar arrays are over 100 million times (10⁸) more sensitive than Raman scattering sensing alone, while maintaining a very uniform response with less than 30 percent variability across the sensor area.

"These arrays are over an order-of-magnitude more sensitive than the best reported SERS sensors in the literature and the current state-of-the-art large-area commercial SERS sensors," said Caldwell."These arrays can be a key component of fully integrated, autonomously operating chemical sensors that detect, identify and report the presence of a threat at trace levels of exposure."

Raman devices use laser light to excite molecular vibrations, which in turn causes a shift in the energy of the scattered laser photons, up or down, creating a unique visual pattern. In the case of trace amounts of molecules in gases or liquids, detection through ordinary Raman scattering is virtually impossible. However, the Raman signal can be enhanced via the SERS effect using metal nanoparticles.

Despite surface-enhanced Raman scattering being first observed in the late 1970s, efforts to provide reproducible SERS-based chemical sensors has been hindered by the inability to make large-area devices with a uniform SERS response. The ability to reproducibly pattern nanometer-sized particles in periodic arrays has finally allowed this requirement to be met.

"While many tools are currently available to detect trace amounts of chemical warfare and biological agents and explosive compounds, a device using SERS can be used to identify these minute quantities of the chemicals of interest by providing a 'fingerprint' of the material, which all but eliminates the prevalence of false alarms," says Glembocki.

SERS offers several potential advantages over other spectroscopic techniques because of its measurement speed, high sensitivity, portability, and simple maneuverability. SERS can additionally be used to enhance existing Raman technologies, such as the hand held and standoff units that are already in use in field applications.

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Ultrafast Quantum Computer Closer: Ten Billion Bits of Entanglement Achieved in Silicon

The researchers used high magnetic fields and low temperatures to produce entanglement between the electron and the nucleus of an atom of phosphorus embedded in a highly purified silicon crystal. The electron and the nucleus behave as a tiny magnet, or 'spin', each of which can represent a bit of quantum information. Suitably controlled, these spins can interact with each other to be coaxed into an entangled state -- the most basic state that cannot be mimicked by a conventional computer.

An international team from the UK, Japan, Canada and Germany, report their achievement in the journalNature.

'The key to generating entanglement was to first align all the spins by using high magnetic fields and low temperatures,' said Stephanie Simmons of Oxford University's Department of Materials, first author of the report. 'Once this has been achieved, the spins can be made to interact with each other using carefully timed microwave and radiofrequency pulses in order to create the entanglement, and then prove that it has been made.'

The work has important implications for integration with existing technology as it uses dopant atoms in silicon, the foundation of the modern computer chip. The procedure was applied in parallel to a vast number of phosphorus atoms.

'Creating 10 billion entangled pairs in silicon with high fidelity is an important step forward for us,' said co-author Dr John Morton of Oxford University's Department of Materials who led the team. 'We now need to deal with the challenge of coupling these pairs together to build a scalable quantum computer in silicon.'

In recent years quantum entanglement has been recognised as a key ingredient in building new technologies that harness quantum properties. Famously described by Einstein as"spooky action at distance" -- when two objects are entangled it is impossible to describe one without also describing the other and the measurement of one object will reveal information about the other object even if they are separated by thousands of miles.

Creating true entanglement involves crossing the barrier between the ordinary uncertainty encountered in our everyday lives and the strange uncertainties of the quantum world. For example, flipping a coin there is a 50% chance that it comes up heads and 50% tails, but we would never imagine the coin could land with both heads and tails facing upwards simultaneously: a quantum object such as the electron spin can do just that.

Dr Morton said: 'At high temperatures there is simply a 50/50 mixture of spins pointing in different directions but, under the right conditions, all the spins can be made to point in two opposing directions at the same time. Achieving this was critical to the generation of spin entanglement.'

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Getting Cars Onto the Road Faster

The auto industry faces major challenges. New models are entering the market at ever shorter intervals, products are becoming more complex, and the trend towards electric cars requires modified vehicle structures. European production sites are coming under increasing cost pressure from low-wage countries. Cost reductions, shorter production times, new materials and innovative assembly techniques are needed if companies are to remain competitive. To achieve these goals, 23 business and research organizations are participating in the EU's Pegasus project (www.pegasus-eu.net). One of the research partners is the Fraunhofer Institute for Chemical Technology ICT in Pfinztal, which is contributing its expertise in the polymer engineering sector. The project partners have jointly developed a software platform to reduce development times and costs.

The Integrated Design and Engineering Environment (IDEE) is a CAD/CAE/CAM software system which is connected to an intelligent database. It analyzes the functional requirements of a product and identifies appropriate materials at an early stage of the development process. If, for example, a car roof is to be made in a different material than before, it is not necessary to conduct a new development process. Instead, the design engineers enter the component data into the software system, which assesses the information and then selects suitable materials and manufacturing processes. The platform also provides engineering guidelines for designing the tools that will be used to produce the component. The project partners have demonstrated how this platform could work on the example of a fender with integrated LED tail light."We used the original fender from a Smart. Our project demonstrates how this complex component can be produced more quickly and cheaply with new processing techniques, materials, bonding agents and tools," says Timo Huber, a scientist at Fraunhofer ICT. Instead of conventional lamps, the project partners fitted LED tail lights to the fender. This reduced the number of separate parts from eight to five, and the number of processing steps from twelve to five. Material and cost savings were also achieved by using conductor paths made of electrically conductive polymer. The conductive carbon nanotubes conduct the electricity from the connector to the LEDs and render metallic conductor structures superfluous.

A further example application: So that components such as the LED tail lights can be dismantled more quickly, they are bonded using a special adhesive. For this the research scientists at Fraunhofer ICT and their project partners developed a new microwave-active adhesive bonding system. When irradiated with microwaves the individual components lose their adhesion and can be easily taken apart. This means that parts can be efficiently recycled into different categories."In addition, we dyed the fender using newly developed pigments based on special nanoparticles," states Huber. These nanostructures can be worked in particularly evenly, to dye plastics such as polypropylene. This means fewer pigments are needed than usual."We have also taken the importance of protecting the climate into account. Further developments in local fiber reinforcement of structural vehicle components will reduce weight and therefore emissions of CO2," the scientist adds, and sums up:"All in all the IDEE system will shorten development times, cut the number of assembly steps and reduce the amount of material consumed." IDEE is still under development, but it can already be used to produce simple components. The software should be ready and available to the auto industry in about a year's time.

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Next-Generation Electronic Devices: Conduction, Surface States in Topological Insulator Nanoribbons Controlled

Perhaps most importantly, the surfaces of topological insulators enable the transport of spin-polarized electrons while preventing the"scattering" typically associated with power consumption, in which electrons deviate from their trajectory, resulting in dissipation.

Because of such characteristics, these materials hold great potential for use in future transistors, memory devices and magnetic sensors that are highly energy efficient and require less power.

In a study published Feb. 13 inNature Nanotechnology, researchers from UCLA's Henry Samueli School of Engineering and Applied Science and from the materials division of Australia's University of Queensland show the promise of surface-conduction channels in topological insulator nanoribbons made of bismuth telluride and demonstrate that surface states in these nanoribbons are"tunable" -- able to be turned on and off depending on the position of the Fermi level.

"Our finding enables a variety of opportunities in building potential new-generation, low-dissipation nanoelectronic and spintronic devices, from magnetic sensing to storage," said Kang L. Wang, the Raytheon Professor of Electrical Engineering at UCLA Engineering, whose team carried out the research.

Bismuth telluride is well known as a thermoelectric material and has also been predicted to be a three-dimensional topological insulator with robust and unique surface states. Recent experiments with bismuth telluride bulk materials have also suggested two-dimensional conduction channels originating from the surface states. But it has been a great challenge to modify surface conduction, because of dominant bulk contribution due to impurities and thermal excitations in such small-band-gap semiconductors.

The development of topological insulator nanoribbons has helped. With their large surface-to-volume ratios, these nanoribbons significantly enhance surface conditions and enable surface manipulation by external means.

Wang and his team used thin bismuth telluride nanoribbons as conducting channels in field-effect transistor structures. These rely on an electric field to control the Fermi level and hence the conductivity of a channel. The researchers were able to demonstrate for the first time the possibility of controlling surface states in topological insulator nanostructures.

"We have demonstrated a clear surface conduction by partially removing the bulk conduction using an external electric field," said Faxian Xiu, a UCLA staff research associate and lead author of the study."By properly tuning the gate voltage, very high surface conduction was achieved, up to 51 percent, which represents the highest values in topological insulators."

"This research is very exciting because of the possibility to build nanodevices with a novel operating principle," said Wang, who is also associate director of the California NanoSystems Institute (CNSI) at UCLA."Very similar to the development of graphene, the topological insulators could be made into high-speed transistors and ultra-high-sensitivity sensors."

The new findings shed light on the controllability of the surface spin states in topological insulator nanoribbons and demonstrate significant progress toward high surface electric conditions for practical device applications. The next step for Wang's team is to produce high-speed devices based on their discovery.

"The ideal scenario is to achieve 100 percent surface conduction with a complete insulating state in the bulk," Xiu said."Based on the current work, we are targeting high-performance transistors with power consumption that is much less than the conventional complementary metal-oxide semiconductors (CMOS) technology used typically in today's electronics."

Study collaborators Jin Zou, a professor of materials engineering at the University of Queensland; Yong Wang, a Queensland International Fellow; and Zou's team at the division of materials at the University of Queensland contributed significantly to this work. A portion of the research was also done in Alexandros Shailos' lab at UCLA.

The study was funded by the Focus Center Research Program -- Center on Functional Engineered Nano Architectonics (FENA) at UCLA Engineering; the U.S. Defense Advanced Research Projects Agency (DARPA); and the Australian Research Council. The research on topological insulators was pioneered by FENA's Shoucheng Zhang, a professor of physics at Stanford University.

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Paperweight for Platinum: Bracing Catalyst in Material Makes Fuel Cell Component Work Better and Last Longer

"Fuel cells are an important area of energy technology, but cost and durability are big challenges," said chemist Jun Liu."The unique structure of this material provides much needed stability, good electrical conductivity and other desired properties."

Liu and his colleagues at the Department of Energy's Pacific Northwest National Laboratory, Princeton University in Princeton, N.J., and Washington State University in Pullman, Wash., combined graphene, a one-atom-thick honeycomb of carbon with handy electrical and structural properties, with metal oxide nanoparticles to stabilize a fuel cell catalyst and make it better available to do its job.

"This material has great potential to make fuel cells cheaper and last longer," said catalytic chemist Yong Wang, who has a joint appointment with PNNL and WSU."The work may also provide lessons for improving the performance of other carbon-based catalysts for a broad range of industrial applications."

Muscle Metal Oxide

Fuel cells work by chemically breaking down oxygen and hydrogen gases to create an electrical current, producing water and heat in the process. The centerpiece of the fuel cell is the chemical catalyst -- usually a metal such as platinum -- sitting on a support that is often made of carbon. A good supporting material spreads the platinum evenly over its surface to maximize the surface area with which it can attack gas molecules. It is also electrically conductive.

Fuel cell developers most commonly use black carbon -- think pencil lead -- but platinum atoms tend to clump on such carbon. In addition, water can degrade the carbon away. Another support option is metal oxides -- think rust -- but what metal oxides make up for in stability and catalyst dispersion, they lose in conductivity and ease of synthesis. Other researchers have begun to explore metal oxides in conjunction with carbon materials to get the best of both worlds.

As a carbon support, Liu and his colleagues thought graphene intriguing. The honeycomb lattice of graphene is porous, electrically conductive and affords a lot of room for platinum atoms to work. First, the team crystallized nanoparticles of the metal oxide known as indium tin oxide -- or ITO -- directly onto specially treated graphene. Then they added platinum nanoparticles to the graphene-ITO and tested the materials.

Platinumweight

The team viewed the materials under high-resolution microscopes at EMSL, DOE's Environmental Molecular Sciences Laboratory on the PNNL campus. The images showed that without ITO, platinum atoms clumped up on the graphene surface. But with ITO, the platinum spread out nicely. Those images also showed catalytic platinum wedged between the nanoparticles and the graphene surface, with the nanoparticles partially sitting on the platinum like a paperweight.

To see how stable this arrangement was, the team performed theoretical calculations of molecular interactions between the graphene, platinum and ITO. This number-crunching on EMSL's Chinook supercomputer showed that the threesome was more stable than the metal oxide alone on graphene or the catalyst alone on graphene.

But stability makes no difference if the catalyst doesn't work. In tests for how well the materials break down oxygen as they would in a fuel cell, the triple-threat packed about 40% more of a wallop than the catalyst alone on graphene or the catalyst alone on other carbon-based supports such as activated carbon.

Last, the team tested how well the new material stands up to repeated usage by artificially aging it. After aging, the tripartite material proved to be three times as durable as the lone catalyst on graphene and twice as durable as on commonly used activated carbon. Corrosion tests revealed that the triple threat was more resistant than the other materials tested as well.

The team is now incorporating the platinum-ITO-graphene material into experimental fuel cells to determine how well it works under real world conditions and how long it lasts.

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Nanonets Give Rust a Boost as Agent in Water Splitting's Hydrogen Harvest

Assistant Professor of Chemistry Dunwei Wang and his clean energy lab pioneered the development of Nanonets in 2008 and have since shown them to be a viable new platform for a number of energy applications by virtue of the increased surface area and improved conductivity of the nano-scale netting made from titanium disilicide, a readily available semiconductor.

Wang and his team report that coating the Nanonets with hematite, the plentiful mineral form of iron oxide, showed the mineral could absorb light efficiently and without the added expense of enhancing the material with an oxygen evolving catalyst.

The results flow directly from the introduction of the Nanonet platform, Wang said. While constructed of wires 1/400th the size of a human hair, Nanonets are highly conductive and offer significant surface area. They serve dual roles as a structural support and an efficient charge collector, allowing for maximum photon-to-charge conversion, Wang said.

"Recent research has shown that the use of a catalyst can boost the performance of hematite," said Wang."What we have shown is the potential performance of hematite at its fundamental level, without a catalyst. By using this unique Nanonet structure, we have shed new light on the fundamental performance capabilities of hematite in water splitting."

On its own, hematite faces natural limits in its ability to transport a charge. A photon can be absorbed, but has no place to go. By giving it structure and added conductivity, the charge transport abilities of hematite increase, said Wang. Water splitting, a chemical reaction that separates water into oxygen and hydrogen gas, can be initiated by passing an electric current through water. But that process is expensive, so gains in efficiency and conductivity are required to make large-scale water splitting an economically viable source for clean energy, Wang said.

"The result highlights the importance of charge transport in semiconductor-based water splitting, particularly for materials whose performance is limited by poor charge diffusion," the researchers report in the journal."Our design introduces material components to provide a dedicated charge transport pathway, alleviates the reliance on the materials' intrinsic properties, and therefore has the potential to greatly broaden where and how various existing materials can be used in energy-related applications."

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Nanoparticles May Enhance Circulating Tumor Cell Detection

The detection of circulating tumor cells (CTCs) is an emerging technique that can allow oncologists to monitor patients with cancer for metastasis or to evaluate the progress of their treatment. The gold particles, which are embedded with dyes allowing their detection by laser spectroscopy, could enhance this technique's specificity by reducing the number of false positives.

The results are published online in the journalCancer Research.

One challenge with detecting CTCs is separating out signals from white blood cells, which are similarly sized as tumor cells and can stick to the same antibodies normally used to identify tumor cells. Commercially available devices trap CTCs using antibody-coated magnetic beads, and technicians must stain the trapped cells with several antibodies to avoid falsely identifying white blood cells as tumor cells.

Emory and Georgia Tech researchers show that polymer-coated and dye-studded gold particles, directly linked to a growth factor peptide rather than an antibody, can detect circulating tumor cells in the blood of patients with head and neck cancer.

"The key technological advance here is our finding that polymer-coated gold nanoparticles that are conjugated with low molecular weight peptides such as EGF are much less sticky than particles conjugated to whole antibodies," says Shuming Nie, PhD, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University."This effect has led to a major improvement in discriminating tumor cells from non-tumor cells in the blood."

The particles are linked to EGF (epithelial growth factor), whose counterpart EGFR (epithelial growth factor receptor) is over-produced on the surfaces of several types of tumor cells.

Upon laser illumination, the particles display a sharp fingerprint-like pattern that is specific to the dye, because the gold enhances the signal coming from the dyes. This suggests that several types of nanoparticles could be combined to gain more information about the growth characteristics of the tumor cells. In addition, measuring CTC levels may be sensitive enough to distinguish patients with localized disease from those with metastatic disease.

"Nanoparticles could be instrumental in modifying the process so that circulating tumor cells can be detected without separating the tumor cells from normal blood cells," Nie says."We've demonstrated that one tumor cell out of approximately one to ten million normal cells can be detected this way."

In collaboration with oncologists at Winship Cancer Institute, researchers used nanoparticles to test for CTCs in blood samples from 19 patients with head and neck cancer. Of these patients, 17 had positive signals for CTCs in their blood. The two with low signals were verified to have no circulating cells by a different technique.

"Although the results have not been compared or validated with current CTC detection methods, our 'one-tube' SERS technology could be faster and lower in costs than other detection methods," says Dong Moon Shin, MD, professor of hematology and oncology and otolaryngology, associate director of academic development for Winship Cancer Institute and director of the Winship Cancer Institute Chemoprevention Program."We need to validate this pilot study by continuing with larger groups of patients and comparing with other tests."

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Making a Point: Method Prints Nanostructures Using Hard, Sharp 'Pen' Tips Floating on Soft Polymer Springs

Hard-tip, soft-spring lithography (HSL) rolls into one method the best of scanning-probe lithography -- high resolution -- and the best of polymer pen lithography -- low cost and easy implementation.

HSL could be used in the areas of electronics (electronic circuits), medical diagnostics (gene chips and arrays of biomolecules) and pharmaceuticals (arrays for screening drug candidates), among others.

To demonstrate the method's capabilities, the researchers duplicated the pyramid on the U.S. one-dollar bill and the surrounding words approximately 19,000 times at 855 million dots per square inch. Each image consists of 6,982 dots. (They reproduced a bitmap representation of the pyramid, including the"Eye of Providence.") This exercise highlights the sub-50-nanometer resolution and the scalability of the method.

The results will be published Jan. 27 by the journalNature.

"Hard-tip, soft-spring lithography is to scanning-probe lithography what the disposable razor is to the razor industry," said Chad A. Mirkin, the paper's senior author."This is a major step forward in the realization of desktop fabrication that will allow researchers in academia and industry to create and study nanostructure prototypes on the fly."

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.

Micro- and nanolithographic techniques are used to create patterns and build surface architectures of materials on a small scale.

Scanning probe lithography, with its high resolution and registration accuracy, currently is a popular method for building nanostructures. The method is, however, difficult to scale up and produce multiple copies of a device or structure at low cost.

Scanning probe lithographies typically rely on the use of cantilevers as the printing device components. Cantilevers are microscopic levers with tips, typically used to deposit materials on surfaces in a printing experiment. They are fragile, expensive, cumbersome and difficult to implement in an array-based experiment.

"Scaling cantilever-based architectures at low cost is not trivial and often leads to devices that are difficult to operate and limited with respect to the scope of application," Mirkin said.

Hard-tip, soft-spring lithography uses a soft polymer backing that supports sharp silicon tips as its"print head." The spring polymer backing allows all of the tips to come in contact with the surface in a uniform manner and eliminates the need to use cantilevers. Essentially, hard tips are floating on soft polymeric springs, allowing either materials or energy to be delivered to a surface.

HSL offers a method that quickly and inexpensively produces patterns of high quality and with high resolution and density. The prototype arrays containing 4,750 tips can be fabricated for the cost of a single cantilever-based tip and made in mass, Mirkin said.

Mirkin and his team demonstrated an array of 4,750 ultra-sharp silicon tips aligned over an area of one square centimeter, with larger arrays possible. Patterns of features with sub-50-nanometer resolution can be made with feature size controlled by tip contact time with the substrate.

They produced patterns"writing" with molecules and showed that as the tips push against the substrate the flexible backing compresses, indicating the tips are in contact with the surface and writing is occurring. (The silicon tips do not deform under pressure.)

"Eventually we should be able to build arrays with millions of pens, where each pen is independently actuated," Mirkin said.

The researchers also demonstrated the ability to use hard-tip, soft-spring lithography to transfer mechanical and electrical energy to a surface.

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World's First Programmable Nanoprocessor: Nanowire Tiles Can Perform Arithmetic and Logical Functions

The groundbreaking prototype computer system, described in a paper appearing in the journalNature, represents a significant step forward in the complexity of computer circuits that can be assembled from synthesized nanometer-scale components.

It also represents an advance because these ultra-tiny nanocircuits can be programmed electronically to perform a number of basic arithmetic and logical functions.

"This work represents a quantum jump forward in the complexity and function of circuits built from the bottom up, and thus demonstrates that this bottom-up paradigm, which is distinct from the way commercial circuits are built today, can yield nanoprocessors and other integrated systems of the future," says principal investigator Charles M. Lieber, who holds a joint appointment at Harvard's Department of Chemistry and Chemical Biology and School of Engineering and Applied Sciences.

The work was enabled by advances in the design and synthesis of nanowire building blocks. These nanowire components now demonstrate the reproducibility needed to build functional electronic circuits, and also do so at a size and material complexity difficult to achieve by traditional top-down approaches.

Moreover, the tiled architecture is fully scalable, allowing the assembly of much larger and ever more functional nanoprocessors.

"For the past 10 to 15 years, researchers working with nanowires, carbon nanotubes, and other nanostructures have struggled to build all but the most basic circuits, in large part due to variations in properties of individual nanostructures," says Lieber, the Mark Hyman Professor of Chemistry."We have shown that this limitation can now be overcome and are excited about prospects of exploiting the bottom-up paradigm of biology in building future electronics."

An additional feature of the advance is that the circuits in the nanoprocessor operate using very little power, even allowing for their miniscule size, because their component nanowires contain transistor switches that are"nonvolatile."

This means that unlike transistors in conventional microcomputer circuits, once the nanowire transistors are programmed, they do not require any additional expenditure of electrical power for maintaining memory.

"Because of their very small size and very low power requirements, these new nanoprocessor circuits are building blocks that can control and enable an entirely new class of much smaller, lighter weight electronic sensors and consumer electronics," says co-author Shamik Das, the lead engineer in MITRE's Nanosystems Group.

"This new nanoprocessor represents a major milestone toward realizing the vision of a nanocomputer that was first articulated more than 50 years ago by physicist Richard Feynman," says James Ellenbogen, a chief scientist at MITRE.

Co-authors on the paper included four members of Lieber's lab at Harvard: Hao Yan (Ph.D. '10), SungWoo Nam (Ph.D. '10), Yongjie Hu (Ph.D. '10), and doctoral candidate Hwan Sung Choe, as well as collaborators at MITRE.

The research team at MITRE comprised Das, Ellenbogen, and nanotechnology laboratory director Jim Klemic. The MITRE Corporation is a not-for-profit company that provides systems engineering, research and development, and information technology support to the government. MITRE's principal locations are in Bedford, Mass., and McLean, Va.

The research was supported by a Department of Defense National Security Science and Engineering Faculty Fellowship, the National Nanotechnology Initiative, and the MITRE Innovation Program.

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Hydrogels Used to Make Precise New Sensor

The"diffraction-based" sensors are made of thin stripes of a gelatinous material called a hydrogel, which expands and contracts depending on the acidity of its environment.

Recent research findings have demonstrated that the sensor can be used to precisely determine pH -- a measure of how acidic or basic a liquid is -- revealing information about substances in liquid environments, said Cagri Savran (pronounced Chary Savran), an associate professor of mechanical engineering at Purdue University.

The sensor's simple design could make it more practical than other sensors in development, he said.

"Many sensors being developed today are brilliantly designed but are too expensive to produce, require highly skilled operators and are not robust enough to be practical," said Savran, whose work is based at Purdue's Birck Nanotechnology Center in the university's Discovery Park.

New findings show the technology is highly sensitive and might be used in chemical and biological applications including environmental monitoring in waterways and glucose monitoring in blood.

"As with any novel platform, more development is needed, but the detection principle behind this technology is so simple that it wouldn't be difficult to commercialize," said Savran, who is collaborating with another team of researchers led by Babak Ziaie, a Purdue professor of electrical and computer engineering and biomedical engineering.

Findings are detailed in a paper presented during the IEEE Sensors 2010 Conference in November and also published in the conference proceedings. The paper was written by postdoctoral researcher Chun-Li Chang, doctoral student Zhenwen Ding, Ziaie and Savran.

The flexible, water-insoluble hydrogel is formed into a series of raised stripes called a"diffraction grating," which is coated with gold on both the stripe surfaces and the spaces in between. The stripes expand and contract depending on the pH level of the environment.

Researchers in Ziaie's lab fabricated the hydrogel, while Savran's group led work in the design, development and testing of the diffraction-based sensor.

The sensors work by analyzing laser light reflecting off the gold coatings. Reflections from the stripes and spaces in between interfere with each other, creating a"diffraction pattern" that differs depending on the height of the stripes.

These diffraction patterns indicate minute changes in the movement of the hydrogel stripes in response to the environment, in effect measuring changes in pH.

"By precise measurement of pH, the diffraction patterns can reveal a lot of information about the sample environment," said Savran, who by courtesy is an associate professor of biomedical engineering and electrical and computer engineering."This technology detects very small changes in the swelling of the diffraction grating, which makes them very sensitive."

The pH of a liquid is recorded on a scale from 0 to 14, with 0 being the most acidic and 14 the most basic. Findings showed the device's high sensitivity enables it to resolve changes smaller than one-1,000th on the pH scale, measuring swelling of only a few nanometers. A nanometer is about 50,000 times smaller than the finest sand grain.

"We know we can make them even more sensitive," Savran said."By using different hydrogels, gratings responsive to stimuli other than pH can also be fabricated."

The work is ongoing.

"It's a good example of collaborations that can blossom when labs focusing on different research are located next to each other," Savran said."Professor Ziaie's lab was already working with hydrogels, and my group was working on diffraction-based sensors. Hearing about the hydrogels work next door, one of my postdoctoral researchers, Chun-Li Chang thought of making a reflective diffraction grating out of hydrogels."

The Office of Technology Commercialization of the Purdue Research Foundation has filed for U.S. patent protection on the concept.

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‘Cornell Dots’That Light Up Cancer Cells Go Into Clinical Trials

"The FDA approval finally puts a federal approval stamp on all the assumptions we have been working under for years. This is really, really nice," said Ulrich Wiesner, the Spencer T. Olin Professor of Materials Science and Engineering, who has devoted eight years of research to developing the nanoparticles."Cancer is a terrible disease, and my family has a long history of it. I, thus, have a particular personal motivation to work in this area."

The trial with five melanoma patients at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City will seek to verify that the dots, also known as C dots, are safe and effective in humans, and to provide data to guide future applications."This is the first product of its kind. We want to make sure it does what we expect it to do," said Michelle Bradbury, M.D., radiologist at MSKCC and assistant professor of radiology at Weill Cornell Medical College.

C dots are silica spheres less than 8 nanometers in diameter that enclose several dye molecules. (A nanometer is one-billionth of a meter, about the length of three atoms in a row.) The silica shell, essentially glass, is chemically inert and small enough to pass through the body and out in the urine. For clinical applications, the dots are coated with polyethylene glycol so the body will not recognize them as foreign substances.

To make the dots stick to tumor cells, organic molecules that bind to tumor surfaces or even specific locations within tumors can be attached to the shell. When exposed to near-infrared light, the dots fluoresce much brighter than unencapsulated dye to serve as a beacon to identify the target cells. The technology, the researchers say, can show the extent of a tumor's blood vessels, cell death, treatment response and invasive or metastatic spread to lymph nodes and distant organs. The safety and ability to be cleared from the body by the kidneys has been confirmed by studies in mice at MSKCC, reported in the January 2009 issue of the journal Nano Letters (Vol. 9 No. 1).

For the human trials, the dots will be labeled with radioactive iodine, which makes them visible in PET scans to show how many dots are taken up by tumors and where else in the body they go and for how long.

"We do expect it to go to other organs," Bradbury said."We get numbers, and from that curve derive how much dose each organ gets. And we need to find out how fast it passes through. Are they cleared from the kidney at the same rate as in mice?"

One of many advantages of C dots, Bradbury noted, is that they remain in the body long enough for surgery to be completed."Surgeons love optical," she said."They don't need the radioactivity, but {our study} confirms what the optical signal is. As you learn that, eventually you no longer need the radioactivity."

On the other hand, she added, the dots also may serve as a carrier to deliver radioactivity or drugs to tumors."This is step one to jump-start a process we think will do multiple things with one platform," she said.

First-generation Cornell dots were developed in 2005 by Hooisweng Ow, then a graduate student working with Wiesner. Wiesner, Ow and Kenneth Wang '77 have co-founded the company Hybrid Silica Technologies to commercialize the invention. The dots, Wiesner said, also have possible applications in displays, optical computing, sensors and such microarrays as DNA chips.

Wiesner's original research was funded by the National Science Foundation, New York state and Phillip Morris USA.

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Engineers Grow Nanolasers on Silicon, Pave Way for on-Chip Photonics

They describe their work in a paper to be published Feb. 6 in an advanced online issue of the journalNature Photonics.

"Our results impact a broad spectrum of scientific fields, including materials science, transistor technology, laser science, optoelectronics and optical physics," said the study's principal investigator, Connie Chang-Hasnain, UC Berkeley professor of electrical engineering and computer sciences.

The increasing performance demands of electronics have sent researchers in search of better ways to harness the inherent ability of light particles to carry far more data than electrical signals can. Optical interconnects are seen as a solution to overcoming the communications bottleneck within and between computer chips.

Because silicon, the material that forms the foundation of modern electronics, is extremely deficient at generating light, engineers have turned to another class of materials known as III-V (pronounced"three-five") semiconductors to create light-based components such as light-emitting diodes (LEDs) and lasers.

But the researchers pointed out that marrying III-V with silicon to create a single optoelectronic chip has been problematic. For one, the atomic structures of the two materials are mismatched.

"Growing III-V semiconductor films on silicon is like forcing two incongruent puzzle pieces together," said study lead author Roger Chen, a UC Berkeley graduate student in electrical engineering and computer sciences."It can be done, but the material gets damaged in the process."

Moreover, the manufacturing industry is set up for the production of silicon-based materials, so for practical reasons, the goal has been to integrate the fabrication of III-V devices into the existing infrastructure, the researchers said.

"Today's massive silicon electronics infrastructure is extremely difficult to change for both economic and technological reasons, so compatibility with silicon fabrication is critical," said Chang-Hasnain."One problem is that growth of III-V semiconductors has traditionally involved high temperatures -- 700 degrees Celsius or more -- that would destroy the electronics. Meanwhile, other integration approaches have not been scalable."

The UC Berkeley researchers overcame this limitation by finding a way to grow nanopillars made of indium gallium arsenide, a III-V material, onto a silicon surface at the relatively cool temperature of 400 degrees Celsius.

"Working at nanoscale levels has enabled us to grow high quality III-V materials at low temperatures such that silicon electronics can retain their functionality," said Chen.

The researchers used metal-organic chemical vapor deposition to grow the nanopillars on the silicon."This technique is potentially mass manufacturable, since such a system is already used commercially to make thin film solar cells and light emitting diodes," said Chang-Hasnain.

Once the nanopillar was made, the researchers showed that it could generate near infrared laser light -- a wavelength of about 950 nanometers -- at room temperature. The hexagonal geometry dictated by the crystal structure of the nanopillars creates a new, efficient, light-trapping optical cavity. Light circulates up and down the structure in a helical fashion and amplifies via this optical feedback mechanism.

The unique approach of growing nanolasers directly onto silicon could lead to highly efficient silicon photonics, the researchers said. They noted that the miniscule dimensions of the nanopillars -- smaller than one wavelength on each side, in some cases -- make it possible to pack them into small spaces with the added benefit of consuming very little energy

"Ultimately, this technique may provide a powerful and new avenue for engineering on-chip nanophotonic devices such as lasers, photodetectors, modulators and solar cells," said Chen.

"This is the first bottom-up integration of III-V nanolasers onto silicon chips using a growth process compatible with the CMOS (complementary metal oxide semiconductor) technology now used to make integrated circuits," said Chang-Hasnain."This research has the potential to catalyze an optoelectronics revolution in computing, communications, displays and optical signal processing. In the future, we expect to improve the characteristics of these lasers and ultimately control them electronically for a powerful marriage between photonic and electronic devices."

The Defense Advanced Research Projects Agency and a Department of Defense National Security Science and Engineering Faculty Fellowship helped support this research.

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Nanoscale Micorscopy and AFM Positioning: Shining Light on a Needle in a Haystack

The atomic force microscope (AFM) has become one of the standard tools of nanotechnology. The concept is deceptively simple. A needle -- not unlike an old-fashioned phonograph stylus, but much smaller with a tip at most only a couple of atoms wide -- moves across the surface of the specimen. A laser measures tiny deflections of the tip as it is pushed or pulled by atomic scale forces, such as electrostatic forces or chemical attraction. Scanning the tip back and forth across the sample yields a three-dimensional image of the surface. The resolution can be astonishing -- in some cases showing individual atoms, a resolution a thousand times smaller than the best optical microscopes can achieve.

Such amazing sensitivity incurs a technical problem: if your probe can image an object of, say, 100 square nanometers, how exactly do you find that object if it could be nearly anywhere on a microscope stage a million times that size? That's not an unusual case in biological applications. The brute-force answer is, you scan the probe back and forth, probably at a higher speed, until it runs into something interesting. Like the coffee table in the dark, this has problems. The AFM tip is not only very delicate and easy to damage, but it can be degraded by picking up unwanted atoms or molecules from the surface. Also, in the biosciences, where the AFM is becoming increasingly important, research specimens usually are"soft" things like proteins or membranes that can be damaged by an uncontrolled collision with the tip. One solution has been to"label" the target molecule with a small fluorescent compound or quantum dot, so that it lights up and is easy to find, but that means chemically altering the subject, which may not be desirable.

Instead, the JILA team opted to use a flashlight. Building upon an earlier innovation for stabilizing the position of an AFM tip, the group uses a tightly focused, low-power laser beam to optically scan the area, identifying target locations by minute changes in the scattered light. This laser is scanned across the sample to form an image, analogous to forming an AFM image.

The same laser -- and detection technique -- is used to locate the AFM tip. Hence, the laser serves as a common frame of reference and it's relatively straightforward to align the optical and the AFM image. In experiments with patches of cell membrane from single-cell organisms,* the group has demonstrated that they can locate these protein complexes and align the AFM tip with a precision of about 40 nanometers. Relying solely on scattered light, their technique requires no prior chemical labeling or modification of the target molecules.

"You solve a couple of problems," says NIST physicist Thomas Perkins."You solve the problem of finding the object you want to study, which is sort of a needle in a haystack problem. You solve the problem of not contaminating your tip. And, you solve the problem of not crashing your tip into what you were looking for. This prevents damaging your tip and, for soft biological targets, not damaging your sample." And, he says, it's much more efficient."From a practical perspective, instead of my grad student starting to do real science at 4 p.m., she can start doing science at 10 a.m."

* The team used"purple membrane," which is cell membrane from certain single-cell organisms and contains bacteriorhodopsin, a protein that captures light energy. Bacteriorhodopsin is embedded in purple membrane and is a common protein for research in the biosciences.

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High-Efficiency Photovoltaic Cells Developed

The cells developed by the UPC researchers have surpassed the 15% barrier -- the average efficiency of the most common photovoltaic cells. Specifically, a conversion efficiency (of incident light to electric power) of 20.5% has been achieved, which means the energy produced per unit of area can be increased by one third.

For example, thanks to the high efficiency of this new cell type, only 4.8 m² of photovoltaic panels would be needed to meet one family's annual energy needs (an average of about 4 kWh per day). This compares to an area of 6.5 m² for traditional cells.

The cells are made of crystalline silicon and work in a simple way, much as conventional cells do. The light captured by the cells generates charges that are drawn off at the panel contacts and transformed into an electric current."The goal is to generate a lot of charges that don't get lost -- that make it to the contacts," says Alcubilla, a member of the research group. Finally, after the light from the sun has been converted into electric current, it is fed into the power grid for domestic and industrial use.

The key to the success of the project was therefore to minimize losses, and by pursuing this approach the UPC researchers have managed to produce the most efficient silicon cells in Spain."We've done a lot of work on the conception and development of new materials and structures, and on the technology needed to optimize the entire process and achieve high levels of efficiency," says Alcubilla. The next step is to develop procedures that facilitate large-scale production.

The result achieved in this research (which has involved 38 trials since 2002) is comparable to those obtained in other research projects carried out in countries that are taking the lead in the field of photovoltaic energy. The maximum efficiency obtained for cells of this type is 24.7%, a record set by an Australian group at the University of New South Wales.

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Quantum Quirk: Scientists Pack Atoms Together to Prevent Collisions in Atomic Clock

JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.

JILA scientists demonstrated the new approach using their experimental clock made of about 4,000 strontium atoms. Instead of loading the atoms into a stack of pancake-shaped optical traps as in their previous work, scientists packed the atoms into thousands of horizontal optical tubes. The result was a more than tenfold improvement in clock performance because the atoms interacted so strongly that, against all odds, they stopped hitting each other. The atoms, which normally like to hang out separately and relaxed, get so perturbed from being forced close together that the ensemble is effectively frozen in place.

"The atoms used to have the whole dance floor to move around on and now they are confined in alleys, so the interaction energy goes way up," says NIST/JILA Fellow Jun Ye, leader of the experimental team.

How exactly does high interaction energy -- the degree to which an atom's behavior is modified by the presence of others -- prevent collisions? The results make full sense in the quantum world. Strontium atoms are a class of particles known as fermions. If they are in identical energy states, they cannot occupy the same place at the same time -- that is, they cannot collide. Normally the laser beam used to operate the clock interacts with the atoms unevenly, leaving the atoms dissimilar enough to collide. But the interaction energy of atoms packed in optical tubes is now higher than any energy shifts that might be caused by the laser, preventing the atoms from differentiating enough to collide.

The idea was proposed by JILA theorist Ana Maria Rey and demonstrated in the lab by Ye's group.

Given the new knowledge, Ye believes his clock and others based on neutral atoms will become competitive in terms of accuracy with world-leading experimental clocks based on single ions (electrically charged atoms). The JILA strontium clock is currently the best performing experimental clock based on neutral atoms and, along with several NIST ion and neutral atom clocks, a possible candidate for a future international time standard. The devices provide highly accurate time by measuring oscillations (which serve as"ticks") between the energy levels in the atoms.

In addition to preventing collisions, the finding also means that the more atoms in the clock, the better."As atom numbers increase, both measurement precision and accuracy increase accordingly," Ye says.

To trap the atoms in optical tubes, scientists first use blue and red lasers to cool strontium atoms to about 2 microKelvin in a trap that uses light and magnetic fields. A vertical lattice of light waves is created using an infrared laser beam that spans and traps the atom cloud. Then a horizontal infrared laser beam is turned on, creating optical tube traps at the intersection with the vertical laser.

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New Nanoparticles Make Blood Clots Visible

Now, researchers at Washington University School of Medicine in St. Louis report that they have designed nanoparticles that find clots and make them visible to a new kind of X-ray technology.

According to Gregory Lanza, MD, PhD, a Washington University cardiologist at Barnes-Jewish Hospital, these nanoparticles will take the guesswork out of deciding whether a person coming to the hospital with chest pain is actually having a heart attack.

"Every year, millions of people come to the emergency room with chest pain. For some of them, we know it's not their heart. But for most, we're not sure," says Lanza, a professor of medicine. When there is any doubt, the patient must be admitted to the hospital and undergo tests to rule out or confirm a heart attack.

"Those tests cost money and they take time," Lanza says.

Rather than an overnight stay to make sure the patient is stable, this new technology could reveal the location of a blood clot in a matter of hours.

Spectral CT

The nanoparticles are designed to be used with a new type of CT scanner that is capable of"seeing" metals in color. The new technology, called spectral CT, uses the full spectrum of the X-ray beam to differentiate objects that would be indistinguishable with a regular CT scanner that sees only black and white.

Lanza says the new scanner takes advantage of the same physics that astronomers use to look at the light from a star and tell what metals it contains.

"They're looking at the X-ray spectrum, and the X-ray spectrum tells them what metals are there," he says."That's exactly what we do."

Bismuth nanoparticles

In this case, the metal in question is bismuth. Dipanjan Pan, PhD, research assistant professor of medicine, designed a nanoparticle that contains enough bismuth for it to be seen by the spectral CT scanner.

"Each nanoparticle is carrying a million atoms of bismuth," Lanza says. Since CT is a relatively insensitive imaging technique, this sheer quantity of metal is necessary for the particles to be visible to the scanner.

But bismuth is a toxic heavy metal, Pan says. It can't be injected into the body on its own. Instead, Pan used a compound made of bismuth atoms attached to fatty acid chains that can't come apart in the body. He then dissolved this compound in a detergent and encapsulated the mixture in a phospholipid membrane. Much like oil droplets suspended in a shaken vinaigrette, these particles self-assemble with the bismuth compound at the core.

As Pan showed in a mouse model, the design of the nanoparticles also allows the body to break them apart and release the inner bismuth compound in a safe form.

Once the nanoparticles carried enough bismuth to be visible to the scanner, Pan added a molecule to the particles' surface that seeks out a protein called fibrin. Fibrin is common in blood clots but is not found elsewhere in the vasculature.

"If you're having a heart attack, the lining of your coronary artery has ruptured, and a clot is forming to repair it," Lanza says."But that clot is starting to narrow the vessel so blood can't get by. Now we have a nanoparticle that will see that clot."

A spectral CT image with the bismuth nanoparticles targeted to fibrin will provide the same information as a traditional black and white CT image, but the fibrin in any blood clots will show up in a color, such as yellow or green, solving the problem of calcium interference common to traditional CT scanners.

The spectral CT scanner used in this study is still a prototype instrument, developed by Philips Research in Hamburg, Germany. The nanoparticles have only been tested in rabbits and other animal models, but early results show success in distinguishing blood clots from calcium interference.

Saving lives

More than simply confirming a heart attack, the new nanoparticles and spectral CT scanner can show a clot's exact location.

Today, even if doctors determine the patient is having a heart attack, they can't locate the clot without admitting the patient to the cardiac catheterization lab, inserting a dye and looking for narrow plaque-filled arteries they could open with stents. But Lanza says looking for narrow arteries doesn't solve all the problems.

"The ones that have very narrow openings are not the worrisome ones," Lanza says."We find those in the cardiac catheterization lab and we open them up."

What is worrisome is when blood is free to flow through the arteries, but there is unstable plaque on the artery wall, what Lanza calls"moderate-grade disease."

"Most people's heart attacks or strokes are from moderate-grade disease that breaks off and all of a sudden blocks an artery," Lanza says."It's what happened to NBC newsman Tim Russert. You need something that tells you there is ruptured plaque even when the vessel isn't very narrow."

Since this nanoparticle finds and sticks to fibrin in the vessels, it would allow doctors to see problems that were previously difficult or impossible to detect.

With this imaging technique, Lanza predicts new approaches to treating coronary disease. Unstable plaque that doesn't restrict much blood flow does not require an expensive stent to prop the vessel open. Instead, Lanza foresees technologies that might act like Band-Aids, sealing weak spots in the vessel walls.

"Today, you wouldn't know where to stick the Band-Aid," Lanza says."But spectral CT imaging with bismuth nanoparticles would show the exact location of clots in the vessels, making it possible to prevent the dangerous rupture of unstable plaque."

This work was supported by grants from the American Heart Association, National Cancer Institute, Bioengineering Research Partnership and the National Heart, Lung, and Blood Institute.

The spectral CT prototype is on loan to Washington University from Philips Research in Hamburg, Germany, for codevelopment of the scanner, software and nanoparticles.

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Scientists Model Tiny Rotors, Key to Future Nanomachines

Kolomeisky, a Rice University associate professor of chemistry, was offering a peek into a molecular midway where atoms dip, dive and soar according to a set of rules he is determined to decode.

Kolomeisky and Rice graduate student Alexey Akimov have taken a large step toward defining the behavior of these molecular whirligigs with a new paper in the American Chemical Society'sJournal of Physical Chemistry C. Through molecular dynamics simulations, they defined the ground rules for the rotor motion of molecules attached to a gold surface.

It's an extension of their work on Rice's famed nanocars, developed primarily in the lab of James Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science, but for which Kolomeisky has also constructed molecular models.

Striking out in a different direction, the team has decoded several key characteristics of these tiny rotors, which could harbor clues to the ways in which molecular motors in human bodies work.

The motion they described is found everywhere in nature, Kolomeisky said. The most visible example is in the flagella of bacteria, which use a simple rotor motion to move."When the flagella turn clockwise, the bacteria move forward. When they turn counterclockwise, they tumble." On an even smaller level, ATP-synthase, which is an enzyme important to the transfer of energy in the cells of all living things, exhibits similar rotor behavior -- a Nobel Prize-winning discovery.

Understanding how to build and control molecular rotors, especially in multiples, could lead to some interesting new materials in the continuing development of machines able to work at the nanoscale, he said. Kolomeisky foresees, for instance, radio filters that would let only a very finely tuned signal pass, depending on the nanorotors' frequency.

"It would be an extremely important, though expensive, material to make," he said."But if I can create hundreds of rotors that move simultaneously under my control, I will be very happy."

The professor and his student cut the number of parameters in their computer simulation to a subset of those that most interested them, Kolomeisky said. The basic-model molecule had a sulfur atom in the middle, tightly bound to a pair of alkyl chains, like wings, that were able to spin freely when heated. The sulfur anchored the molecule to the gold surface.

While working on a previous paper with researchers at Tufts University, Kolomeisky and Akimov saw photographic evidence of rotor motion by scanning tunneling microscope images of sulfur/alkyl molecules heated on a gold surface. As the heat rose, the image went from linear to rectangular to hexagonal, indicating motion. What the pictures didn't indicate was why.

That's where computer modeling was invaluable, both on the Kolomeisky lab's own systems and through Rice's SUG@R platform, a shared supercomputer cluster. By testing various theoretical configurations -- some with two symmetrical chains, some asymmetrical, some with only one chain -- they were able to determine a set of interlocking characteristics that control the behavior of single-molecule rotors.

First, he said, the symmetry and structure of the gold surface material (of which several types were tested) has a lot of influence on a rotor's ability to overcome the energy barrier that keeps it from spinning all the time. When both arms are close to surface molecules (which repel), the barrier is large. But if one arm is over a space -- or hollow -- between gold atoms, the barrier is significantly smaller.

Second, symmetric rotors spin faster than asymmetric ones. The longer chain in an asymmetric pair takes more energy to get moving, and this causes an imbalance. In symmetric rotors, the chains, like rigid wings, compensate for each other as one wing dips into a hollow while the other rises over a surface molecule.

Third, Kolomeisky said, the nature of the chemical bond between the anchor and the chains determines the rotor's freedom to spin.

Finally, the chemical nature of rotating groups is also an important factor.

Kolomeisky said the research opens a path for simulating more complex rotor molecules. The chains in ATP-synthase are far too large for a simulation to wrangle,"but as computers get more powerful and our methods improve, we may someday be able to analyze such long molecules," he said.

The Welch Foundation, the National Science Foundation and the National Institutes of Health funded the research.

An animation of a rotor simulation:http://www.youtube.com/watch?v=GJJxSs6AkeM

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