Latest News About Materials................

RADIOACTIVE MATERIALS IN NEW ZEALAND INDUSTRY

noreply@blogger.com (Pabath) — Mon, 30 Apr 2012 15:06:00 +0000

This is a materials related article about radio active materials in New Zealand industry.

Certain materials "decay" at the atomic level over a period of time, giving off "radiation"

in the form of energy or subatomic particles. This radiation can be harnessed and used for

a variety of industrial applications. Some of the commonest of these which are used in

New Zealand are listed below, although many others exist that are either only used to a

small extent or used exclusively overseas.

Thickness, density and level gauges car hire auckland By measuring the relative amounts of radiation reflected back and absorbed into a substance, it's thickness can be precisely determined. This is used for quality control in a

variety of industries. Using more penetrating radiation and a thicker sample, the same

technique can be used to determine the density of substances such as woodpulp or

ironsand slurries, and a similar technique is used to determine the level of liquid in a

closed container.

Elemental analysis

Different elements react differently when irradiated, thus changing the energy of the

radiation beam reflected back off a surface. The elemental composition of a substance can

be determined by comparing the initial radiation with the reflected radiation and

consulting charts that list the characteristic changes made by different elements.

Static elimination

Radiation can be used to reduce the number of ions present in the air. This is useful for

many industries, including the electronics and photography industries.

These examples are just a small selection, but this provides an idea of the scope of

situations in which radiation is useful. However, radiation is also harmful to humans and

thus it is important in all applications using radiation that this danger is minimised. This is

done by limiting the time of exposure, distancing people from the radiation source and

shielding them from it with a physical barrier. The substance the barrier is made of varies

depending on the type of radiation involved, as what blocks some emissions will not block

others, but is commonly lead. There is always a risk involved in using radiation (as there

is with the natural cosmic radiation to which we are constantly exposed), but with these

measures that risk can be minimised.

About Materials engineering

noreply@blogger.com (W.A.P.S.Madusanka) — Mon, 16 Apr 2012 19:19:00 +0000

Materials Engineering is a field of engineering that encompasses the spectrum of materials types and how to use them in manufacturing. Materials span the range: metals, ceramics, polymers (plastics), semiconductors, and combinations of materials called composites. We live in a world that is both dependent upon and limited by materials. Everything we see and use is made of materials: cars, airplanes, computers, refrigerators, microwave ovens, TVs, dishes, silverware, athletic equipment of all types, and even biomedical devices such as replacement joints and limbs. All of these require materials specifically tailored for their application. Specific properties are required that result from carefully selecting the materials and from controlling the manufacturing processes used to convert the basic materials into the final engineered product. Exciting new product developments frequently are possible only through new materials and/or processing.

Activities of materials engineers range from primary materials production, including recycling, through the design and development of new materials to the reliable and economical manufacturing for the final product. Such activities are found commonly in industries such as aerospace, transportation, electronics, energy conversion, and biomedical systems. The future will bring ever-increasing challenges and opportunities for new materials and better processing. Materials are evolving faster today than at any time in history. New and improved materials are an "underpinning technology" - one which can stimulate innovation and product improvement. High quality products result from improved processing and more emphasis will be placed on reclaiming and recycling. For these many reasons, most surveys name the materials field as one of the careers with excellent future opportunities.

INVESTMENT CASTING

noreply@blogger.com (W.A.P.S.Madusanka) — Sun, 15 Apr 2012 06:15:00 +0000

Advances in investment casting over the past several years have enabled cost reductions and improved reliability in complex components.

Engineers are finding ways to bypass timeconsuming and expensive production
routes by investment casting hundreds of parts that were never cast before. Technological progress has improved control at every stage of the process, spurred alloy development, effectively exploited the considerable design freedom of the process, and leveraged the unique features of investment casting to enhance capability, repeatability, and affordability. Foundries have steadily reduced variability through the application of microprocessor controls, automated equipment, statistical methods, and scientific management techniques.

Investment Casting Process
The investment casting, or “lost-wax” process is a production method for making parts from molten metal. The process begins with the manufacture of a pattern that is the same shape as the end product. Usually made of wax formed in custom tooling, the individual pattern elements are joined to form a wax-pattern assembly. The assembly is repeatedly dipped into a ceramic slurry and coated with sand stucco to build up a shell, which is then dried. When the shell is dry, the assembly is placed in an autoclave and the wax is melted out. When empty, the mold is heated to the proper temperature and molten metal is poured into the mold. As the metal cools, it solidifies into a casting. Subsequently, the mold is broken off and the casting undergoes a number of finishing operations.

Halting the attack

noreply@blogger.com (W.A.P.S.Madusanka) — Sat, 24 Mar 2012 15:30:00 +0000

Cancer cells must prepare for travel before invading new tissues, but new Cornell research has found a possible way to stop these cells from ever hitting the road.

Researchers have identified two key proteins that are needed to get cells moving and have uncovered a new pathway that treatments could block to immobilize mutant cells and keep cancer from spreading, said Richard Cerione, Goldwin Smith Professor of Pharmacology and Chemical Biology at Cornell's College of Veterinary Medicine.The study, co-authored by graduate student Lindsey Boroughs; Jared L. Johnson, Ph.D. '11; and Marc Antonyak, senior research associate, is published in the Journal of Biological Chemistry.Most adult cells stay stationary, but the ability for some to move helps embryos develop, wounds heal and immune responses mobilize. When migrating cells go astray they can cause developmental disorders, ranging from cardiovascular disease to mental retardation. Metastasis (the spread of cancer from one part of the body to another) also relies on cell migration. How exactly cancer cells migrate and invade tissues continues to be a mystery. However, Cerione's lab uncovered a potentially important clue when it noticed that cancer cells gearing up to move would collect a protein called tissue transglutaminase (tTG) into clusters near the cell membrane."tTG is turning up in many aspects of human cancer research and seems to be contributing to the process that turns cells cancerous," said Cerione. "Lindsey and Marc discovered that cells must gather tTG into a specific place in their membrane before they can move. But tTG is usually inactive, and we've been trying to understand how a cell gets this protein to the exact right place so that it can be activated to stimulate cell migration."Observing breast cancer cells in culture, Cerione's lab found a missing link in our understanding of cell migration: Cancerous cells become hyperactive invasion vehicles by using tTG together with other proteins like wheels, poking them through the surface to form a "leading edge" that pulls the cell forward. But to get the wheels to the leading edge, it turns out they need another protein to roll them there -- a "chaperone" protein called heat-shock-protein-70 (Hsp70)."We've known for years that Hsp70 acts as a chaperone to other proteins, ensuring that they assume the right structure and behave properly when a cell is under stress," said Cerione. "Heat shock proteins have also been implicated in cancer, although scientists have been trying to understand their exact role in cancer. Our research has uncovered a previously unknown role for these chaperones -- helping tTG get to the leading edge. tTG must be in this location for cancer to spread."When cells become stressed, Hsp70 influences the behavior of their "client" proteins, ensuring they keep the right shape. Cells need chaperones like Hsp70 to ensure that various proteins work correctly and don't warp, but these same chaperones can help cancer cells spread by helping move tTG to the membrane surface. Using inhibitors that block the function of chaperones, Cerione and his team paralyzed Hsp70s and stopped breast cancer cells in culture from gathering tTG into a leading edge, effectively immobilizing them.Exactly how Hsp70 gets tTG going remains unknown, but Cerione believes other proteins are involved."If we can better understand how Hsp70 influences tTG, we can figure out ways to modulate that interaction to immobilize cancer cells and keep them from becoming invasive," said Cerione. "We suspect Hsp70 is using a third kind of protein to move tTG, and that's what we're trying to figure out now. Finding the next link in this chain of events could have important consequences for preventing cancer migration and metastasis.

Jell-o mold?

noreply@blogger.com (W.A.P.S.Madusanka) — Sat, 24 Mar 2012 03:30:00 +0000

Inspired by nature’s ability to shape a petal, and building on simple techniques used in photolithography and printing, researchers at the University of Massachusetts Amherst have developed a new tool for manufacturing three-dimensional shapes easily and cheaply, to aid advances in biomedicine, robotics and tunable micro-optics.

Ryan Hayward, Christian Santangelo and colleagues describe their new method of halftone gel lithography for photo-patterning polymer gel sheets in the current issue of Science. They say the technique, among other applications, may someday help biomedical researchers to direct cells cultured in a laboratory to grow into the correct shape to form a blood vessel or a particular organ.

"We wanted to develop a strategy that would allow us to pattern growth with some of the same flexibility that nature does," Hayward explains. Many plants create curves, tubes and other shapes by varying growth in adjacent areas. While some leaf or petal cells expand, other nearby cells do not, and this contrast causes buckling into a variety of shapes, including cones or curly edges. A lily petal’s curve, for example, arises from patterned areas of elongation that define a specific three-dimensional shape. Building on this concept, Hayward and colleagues developed a method for exposing ultraviolet-sensitive thin polymer sheets to patterns of light. The amount of light absorbed at each position on the sheet programs the amount that this region will expand when placed in contact with water, thus mimicking nature’s ability to direct certain cells to grow while suppressing the growth of others. The technique involves spreading a 10-micrometer-thick layer (about 5 times thinner than a human hair) of polymer onto a substrate before exposure.

Areas of the gel exposed to light become crosslinked, restricting their ability to expand, while nearby unexposed areas will swell like a sponge as they absorb water. As in nature, this patterned growth causes the gel to buckle into the desired shape. Unlike in nature, however, these materials can be repeatedly flattened and re-shaped by drying out and rehydrating the sheet. To date, the UMass Amherst researchers have made a variety of simple shapes including spheres, saddles and cones, as well as more complex shapes such as minimal surfaces. Creating the latter represents a fundamental challenge that demonstrates basic principles of the method, Hayward says.He adds, "Analogies to photography and printing are helpful here." When photographic film is exposed to patterns of light, a chemical pattern is encoded within the film. Later, the film is developed using several solvents that etch the exposed and unexposed regions differently to provide the image we see on the photographic negative. A very similar process is used by UMass Amherst researchers to pattern growth in gel sheets.

Santangelo and Hayward also borrowed an idea from the printing industry that allows them to make complicated patterns in a very simple way. In photolithography, just as in printing, it is expensive to print a picture using different color shades because each shade requires a different ink. Thus, most high-volume printing relies on "halftoning," in which only a few ink colors are used to print varied-sized dots. Smaller dots take up less space and allow more white light to reflect from the paper, so they appear as a lighter color shade than larger dots.

An important discovery by the UMass Amherst team is that this concept applies equally well to patterning the growth of their gel sheets. Rather than trying to make smooth patterns with many different levels of growth, they were able to simply print dots of highly restricted growth and vary the dot size to program a patterned shape. "We’re discovering new ways to plan or pattern growth in a soft polymer gel that’s spread on a substrate to get any shape you want," Santangelo says. "By directly transferring the image onto the soft gel with half-tones of light, we direct its growth."

He adds, "We aren’t sure yet how many shapes we can make this way, but for now it’s exciting to explore and we’re focused on understanding the process better. A model system like this helps us to watch how it unfolds. For biomedicine or bioengineering, one of the questions has been how to create tissues that could help to grow you a new blood vessel or a new organ. We now know a little more about how to go from a flat sheet of cells to a complex organism."

Magnetic currents in graphene now simple to detect

noreply@blogger.com (W.A.P.S.Madusanka) — Fri, 23 Mar 2012 03:30:00 +0000

Researchers from the University of Groningen and the Foundation for Fundamental Research on Matter (FOM) have developed a technique to simply measure the magnetic moment of electrons (the spin) using non-magnetic contacts. They demonstrated the technique in graphene, a layer of carbon one atom thick. The use of non-magnetic contacts could yield simpler designs for nano-devices that use spin current. Such equipment is currently used in hard discs to make these faster and more efficient. The researchers published their results online in the journal Nature Physics.

Graphene is a two-dimensional material with superb characteristics for the transport of charge and spin, the two fundamental properties of an electron. Graphene is not magnetic and therefore magnetic information must first of all be 'added' before spin transport can be studied in it. The researchers did this by transmitting electric current through magnetic contacts, which set the spin of all the electrons in the graphene in the same direction. As the electrons move, this results in a spin current, which can only be used in devices if it is detected. Previously this could only be done using other magnetic contacts further up in the circuit. Now simpler non-magnetic contacts can also be used for this.The detection technology is based on a new physical mechanism that converts spin current back into voltage again in the graphene, which can be measured directly using non-magnetic contacts. This translation step is similar to the conversion of heat into an electric current, as happens in thermoelectric generators that use waste heat to drive electronic circuits. Both processes make use of the energy-dependent conduction of electrons. This means that the energy of the electrons determines how easily these move, and so how well the material (in this case graphene) conducts. The energy of the electrons is in turn dependent on their magnetic properties or – in the case of thermoelectric generators – the heat of the material.The results are important for the development of spintronics (spin electronics) a new research area that studies the role of the magnetic moment of electrons in electronic equipment. Equipment based on these magnetic characteristics is potentially faster and more efficient.

Making memories

noreply@blogger.com (W.A.P.S.Madusanka) — Thu, 22 Mar 2012 15:30:00 +0000

Studying tiny bits of genetic material that control protein formation in the brain, Johns Hopkins scientists say they have new clues to how memories are made and how drugs might someday be used to stop disruptions in the process that lead to mental illness and brain wasting diseases.In a report recently published in Cell, the researchers said certain microRNAs—genetic elements that control which proteins get made in cells— are the key to controlling the actions of so-called brain-derived neurotrophic factor (BDNF), long linked to brain cell survival, normal learning and memory boosting.During the learning process, cells in the brain’s hippocampus release BDNF, a growth-factor protein that ramps up production of other proteins involved in establishing memories. Yet, by mechanisms that were never understood, BDNF is known to increase production of less than 4 percent of the different proteins in a brain cell.That led Mollie Meffert, M.D., Ph.D., associate professor of biological chemistry and neuroscience at the Johns Hopkins University School of Medicine to track down how BDNF specifically determines which proteins to turn on, and to uncover the role of regulatory microRNAs.MicroRNAs are small molecules that bind to and block messages that act as protein blueprints from being translated into proteins. Many microRNAs in a cell shut down protein production, and, conversely, the loss of certain microRNAs can cause higher production of specific proteins.The researchers measured microRNA levels in brain cells treated with BDNF and compared them to microRNA levels in neurons not treated with BDNF. The researchers noticed that levels of certain microRNAs were lower in brain cells treated with BDNF, suggesting that BDNF controls the levels of these microRNAs and, through this control, also affects protein production. Homing in on those specific microRNAS that disappeared when cells were treated with BDNF, the team found all were of the same type, so-called Let-7 microRNAs, and that all shared a common genetic sequence.“This short genetic sequence has been shown by other researchers to behave like a bar code that can selectively prevent production of Let-7 microRNAs,” says Meffert.To test if the loss of Let-7 microRNAs lets BDNF increase production of specific proteins, Meffert’s team genetically engineered neurons so they could no longer decrease Let-7 microRNAs. They found that treating these neurons with BDNF no longer resulted in decreased microRNA levels or an increase in learning and memory proteins.In measuring microRNA levels in cells treated with BDNF, the researchers also found more than 174 microRNAs that increased with BDNF treatment. This suggested to the research team that BNDF treatment also can increase other microRNAs and, thereby, decrease production of certain proteins. Says Meffert, some of these proteins may need to be decreased during learning and memory, whereas others may not contribute to the process at all.To confirm that BDNF, via microRNA action, halts the production of certain proteins, the researchers monitored living brain cells to find out where messages go in response to BDNF. Messages that aren’t translated into proteins can accumulate inside small formations within cells. Using a microscope, the researchers watched a lab dish containing brain cells that had been marked with a fluorescent molecule that labels these formations as glowing spots. Treating cells with BDNF caused the number and size of the glowing spots to increase. The researchers determined that BDNF uses microRNA to send messages to these spots where they can be exiled away from the translating machinery that turns them into protein.“Monitoring these fluorescent complexes gave us a window that we needed to understand how BDNF is able to target the production of only certain proteins that help neurons to grow and make learning possible,” Meffert says.Adds Meffert, “Now that we know how BDNF boosts production of learning and memory proteins, we have an opportunity to explore whether therapeutics can be designed to enhance this mechanism for treatment of patients with mental disorders and neurodegenerative diseases like Alzheimer’s disease

Metatronic Circuit

noreply@blogger.com (W.A.P.S.Madusanka) — Thu, 22 Mar 2012 03:30:00 +0000

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

“Looking at the success of electronics over the last century, I have always wondered why we should be limited to electric current in making circuits,” said NaderEngheta, professor in the electrical and systems engineering department of Penn’s School of Engineering and Applied Science. “If we moved to shorter wavelengths in the electromagnetic spectrum, like light, we could make things smaller, faster and more efficient.”Different arrangements and combinations of electronic circuits have different functions, ranging from simple light switches to complex supercomputers. These circuits are in turn built of different arrangements of circuit elements, like resistors, inductors and capacitors, which manipulate the flow of electrons in a circuit in mathematically precise ways. And because both electric circuits and optics follow Maxwell’s equations the fundamental formulas that describe the behavior of electromagnetic fields, Engheta’s dream of building circuits with light wasn’t just the stuff of imagination. In 2005, he and his students published a theoretical paper outlining how optical circuit elements could work.Now, he and his group at Penn have made this dream a reality, creating the first physical demonstration of “lumped” optical circuit elements. This represents a milestone in a nascent field of science and engineering Engheta has dubbed “metatronics.”Engheta’s research, which was conducted with members of his group in the electrical and systems engineering department, Yong Sun, Brian Edwards and Andrea Alù, was published in the journal Nature Materials.In electronics, the “lumped” designation refers to elements that can be treated as a black box, something that turns a given input to a perfectly predictable output without an engineer having to worry about what exactly is going on inside the element every time he or she is designing a circuit.“Optics has always had its own analogs of elements, things like lenses, waveguides and gratings,” Engheta said, “but they were never lumped. Those elements are all much larger than the wavelength of light because that’s all that could be easily built in the old days. For electronics, the lumped circuit elements were always much smaller than the wavelength of operation, which is in the radio or microwave frequency range.”Nanotechnology has now opened that possibility for lumped optical circuit elements, allowing construction of structures that have dimensions measured in nanometers. In this experiment’s case, the structure was comb-like arrays of rectangular nanorods made of silicon nitrite.The “meta” in “metatronics” refers to metamaterials, the relatively new field of research where nanoscale patterns and structures embedded in materials allow them to manipulate waves in ways that were previously impossible. Here, the cross-sections of the nanorods and the gaps between them form a pattern that replicates the function of resistors, inductors and capacitors, three of the most basic circuit elements, but in optical wavelengths.“If we have the optical version of those lumped elements in our repertoire, we can actually make designs similar to what we do in electronics but now for operation with light,” Engheta said. “We can build a circuit with light.”In their experiment, the researchers illuminated the nanorods with an optical signal, a wave of light in the mid-infrared range. They then used spectroscopy to measure the wave as it passed through the comb. Repeating the experiment using nanorods with nine different combinations of widths and heights, the researchers showed that the optical “current” and optical “voltage” were altered by the optical resistors, inductors and capacitors with parameters corresponding to those differences in size. “A section of the nanorod acts as both an inductor and resistor, and the air gap acts as a capacitor,” Engheta said. Beyond changing the dimensions and the material the nanorods are made of, the function of these optical circuits can be altered by changing the orientation of the light, giving metatronic circuits access to configurations that would be impossible in traditional electronics.This is because a light wave has polarizations; the electric field that oscillates in the wave has a definable orientation in space. In metatronics, it is that electric field that interacts and is changed by elements, so changing the field’s orientation can be like rewiring an electric circuit. When the plane of the field is in line with the nanorods, as in Figure A, the circuit is wired in parallel and the current passes through the elements simultaneously. When the plane of the electric field crosses both the nanorods and the gaps, as in Figure B, the circuit is wired in series and the current passes through the elements sequentially.“The orientation gives us two different circuits, which is why we call this ‘stereo-circuitry,’” Engheta said. “We could even have the wave hit the rods obliquely and get something we don’t have in regular electronics: a circuit that’s neither in series or in parallel but a mixture of the two.”This principle could be taken to an even higher level of complexity by building nanorod arrays in three dimensions. An optical signal hitting such a structure’s top would encounter a different circuit than a signal hitting its side. Building off their success with basic optical elements, Engheta and his group are laying the foundation for this kind of complex metatronics.“Another reason for success in electronics has to do with its modularity,” he said. “We can make an infinite number of circuits depending on how we arrange different circuit elements, just like we can arrange the alphabet into different words, sentences and paragraphs. “We’re now working on designs for more complicated optical elements,” Engheta said. “We’re on a quest to build these new letters one by one.”

MRIs on a Nanoscale

noreply@blogger.com (W.A.P.S.Madusanka) — Wed, 21 Mar 2012 15:30:00 +0000

Magnetic resonance imaging (MRI) on the nanoscale and the ever-elusive quantum computer are among the advancements edging closer toward the realm of possibility, and a new study co-authored by a UC Santa Barbara researcher may give both an extra nudge. The findings appear in Science Express, an online version of the journal Science.

Ania Bleszynski Jayich, spent a year at Harvard working on an experiment that coupled nitrogen-vacancy centers in diamond to nanomechanical resonators. That project is the basis for the new paper, "Coherent sensing of a mechanical resonator with a single spin qubit."A nitrogen-vacancy (NV) center is a specific defect in diamond that exhibits a quantum magnetic behavior known as spin. When a single spin in diamond is coupled with a magnetic mechanical resonator –– a device used to generate or select specific frequencies –– it points toward the potential for a new nanoscale sensing technique with implications for biology and technology, Jayich explained.Among those possible future applications of such a technique is magnetic resonance imaging on a scale small enough to image the structure of proteins –– an as-yet unaccomplished feat that Jayich called "one of the holy grails of structural biology.""The same physics that will allow the NV center to detect the magnetic field of the resonator, hopefully, will allow MRI on the nanoscale," Jayich said. "It could make MRI more accurate, and able to see more. It's like having a camera with eight megapixels versus one with two megapixels and taking a picture of someone's face. You can't see features that are smaller than the size of a pixel. So do they have three freckles, or do they all look like one big freckle?"That's the idea," Jayich continued. "To resolve individual freckles, so to speak, to see what a protein is made up of. What we found in this paper suggests that it is possible, although a significant amount of work still needs to be done."Though further into the future based on the approach used for this paper, Jayich said, there is also the potential for such a coupling to be advanced and exploited as a possible route toward the development of a hybrid quantum system, or quantum computer.

Nanoforrest harvest

noreply@blogger.com (W.A.P.S.Madusanka) — Wed, 21 Mar 2012 03:30:00 +0000

University of California, San Diego electrical engineers are building a forest of tiny nanowire trees in order to cleanly capture solar energy without using fossil fuels and harvest it for hydrogen fuel generation. Reporting in the journal Nanoscale, the team said nanowires, which are made from abundant natural materials like silicon and zinc oxide, also offer a cheap way to deliver hydrogen fuel on a mass scale.

“This is a clean way to generate clean fuel,” said Deli Wang, professor in the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering.

The trees’ vertical structure and branches are keys to capturing the maximum amount of solar energy, according to Wang. That’s because the vertical structure of trees grabs and adsorbs light while flat surfaces simply reflect it, Wang said, adding that it is also similar to retinal photoreceptor cells in the human eye. In images of Earth from space, light reflects off of flat surfaces such as the ocean or deserts, while forests appear darker. Wang’s team has mimicked this structure in their “3D branched nanowire array” which uses a process called photoelectrochemical water-splitting to produce hydrogen gas. Water splitting refers to the process of separating water into oxygen and hydrogen in order to extract hydrogen gas to be used as fuel. This process uses clean energy with no green-house gas byproduct. By comparison, the current conventional way of producing hydrogen relies on electricity from fossil fuels

“Hydrogen is considered to be clean fuel compared to fossil fuel because there is no carbon emission, but the hydrogen currently used is not generated cleanly,” said Ke Sun, a PhD student in electrical engineering who led the project.

By harvesting more sun light using the vertical nanotree structure, Wang’s team has developed a way to produce more hydrogen fuel efficiently compared to planar counterparts. Wang is also affiliated with the California Institute of Telecommunications and Information Technology and the Material Science and Engineering Program at UC San Diego.The vertical branch structure also maximizes hydrogen gas output, said Sun. For example, on the flat wide surface of a pot of boiling water, bubbles must become large to come to the surface. In the nanotree structure, very small gas bubbles of hydrogen can be extracted much faster. “Moreover, with this structure, we have enhanced, by at least 400,000 times, the surface area for chemical reactions,” said Sun.

In the long run, what Wang’s team is aiming for is even bigger: artificial photosynthesis. In photosynthesis, as plants absorb sunlight they also collect carbon dioxide (CO2) and water from the atmosphere to create carbohydrates to fuel their own growth. Wang’s team hopes to mimic this process to also capture CO2 from the atmosphere, reducing carbon emissions, and convert it into hydrocarbon fuel.

“We are trying to mimic what the plant does to convert sunlight to energy,” said Sun. “We are hoping in the near future our ‘nanotree’ structure can eventually be part of an efficient device that functions like a real tree for photosynthesis."

The team is also studying alternatives to zinc oxide, which absorbs the sun’s ultraviolet light, but has stability issues that affect the lifetime usage of the nanotree structure.

Nano-health

noreply@blogger.com (W.A.P.S.Madusanka) — Tue, 20 Mar 2012 15:30:00 +0000

Researchers at Oregon State University have tapped into the extraordinary power of carbon “nanotubes” to increase the speed of biological sensors, a technology that might one day allow a doctor to routinely perform lab tests in minutes, speeding diagnosis and treatment while reducing costs.

The new findings have almost tripled the speed of prototype nano-biosensors, and should find applications not only in medicine but in toxicology, environmental monitoring, new drug development and other fields. The research was just reported in Lab on a Chip, a professional journal. More refinements are necessary before the systems are ready for commercial production, scientists say, but they hold great potential.

“With these types of sensors, it should be possible to do many medical lab tests in minutes, allowing the doctor to make a diagnosis during a single office visit,” said Ethan Minot, an OSU assistant professor of physics. “Many existing tests take days, cost quite a bit and require trained laboratory technicians. This approach should accomplish the same thing with a hand-held sensor, and might cut the cost of an existing $50 lab test to about $1,” he said.

The key to the new technology, the researchers say, is the unusual capability of carbon nanotubes. An outgrowth of nanotechnology, which deals with extraordinarily small particles near the molecular level, these nanotubes are long, hollow structures that have unique mechanical, optical and electronic properties, and are finding many applications. In this case, carbon nanotubes can be used to detect a protein on the surface of a sensor. The nanotubes change their electrical resistance when a protein lands on them, and the extent of this change can be measured to determine the presence of a particular protein – such as serum and ductal protein biomarkers that may be indicators of breast cancer.

The newest advance was the creation of a way to keep proteins from sticking to other surfaces, like fluid sticking to the wall of a pipe. By finding a way to essentially “grease the pipe,” OSU researchers were able to speed the sensing process by 2.5 times. Further work is needed to improve the selective binding of proteins, the scientists said, before it is ready to develop into commercial biosensors.

“Electronic detection of blood-borne biomarker proteins offers the exciting possibility of point-of-care medical diagnostics,” the researchers wrote in their study. “Ideally such electronic biosensor devices would be low-cost and would quantify multiple biomarkers within a few minutes.”

New "pendulum" for the atomic clock

noreply@blogger.com (W.A.P.S.Madusanka) — Tue, 20 Mar 2012 03:30:00 +0000

The faster a clock ticks, the more precise it can be. Due to the fact that lightwaves vibrate faster than microwaves, optical clocks can be more precise than the caesium atomic clocks which presently determine time. The Physikalisch-Technische Bundesanstalt (PTB) is even working on several of such optical clocks simultaneously. The model with one single ytterbium ion caught in an ion trap is now experiencing another increase in accuracy. At PTB, scientists have succeeded in exciting a quantum-mechanically strongly "forbidden" transition of this ion and - in particular - in measuring it with extreme accuracy. The optical clock based on it is exact to 17 digits after the decimal point.

Optical transitions are the modern counterpart of the pendulum of a mechanical clock. In atomic clocks, the "pendulum" is the radiation which excites the transition between two atomic states of different energy. In the case of caesium atomic clocks, it lies in the microwave range, in the case of optical clocks in the range of laser light so that their "pendulum" oscillates with higher velocity and optical clocks are - consequently - regarded as the atomic clocks of the future.

In the experiment performed at PTB, the scientists devoted themselves to a special forbidden transition. In quantum mechanics, "forbidden" means that the jump between the two energy states of the atoms is almost impossible due to the conservation of symmetry and angular momentum. The excited state can then be very persistent: In the case investigated here, the lifetime of the so-called F-state in the ytterbium ion Yb+ amounts to approx. 6 years. Due to this long lifetime, an extremely narrow resonance - whose linewidth only depends on the quality of the laser used - can be observed during the laser excitation of this state. A narrow resonance line is an important prerequisite for an exact optical clock. At the British National Physical Laboratory (NPL), the sister institute of PTB, the laser excitation of this Yb+-F state from the ground state was achieved for the first time in 1997. As the transition is, however, strongly forbidden, a relatively high laser intensity is required for its excitation. This disturbs the electron structure of the ion as a whole and leads to a shift of the resonance frequency so that an atomic clock based on it would exhibit a rate depending on the laser intensity.

At PTB it has now been possible to show that alternating excitation of the ion with two different laser intensities allows the unperturbed resonance frequency to be determined with high accuracy. Due to this, it has become possible to investigate other frequency shifts often occurring in atomic clocks - e.g. by electric fields or the thermal radiation of the environment. It has turned out that these are unexpectedly small in the case of the Yb+-F state, which can be attributed to the special electronic structure of the state. This is a decisive advantage for the further development of this atomic clock. In the experiments at PTB, the relative uncertainty of the Yb+ frequency was determined with 7 · 10-17. This corresponds to an uncertainty of the atomic clock of only approx. 30 seconds over the age of the universe.

Both groups at NPL and PTB have measured the frequency of the Yb+ transition with their caesium clocks and the results agree within the scope of the uncertainties (1 · 10-15 and 8 · 10-16) which are mainly determined by the caesium clocks. In a research project recently approved within the scope of the European Metrology Research Programme, the two institutes will in future cooperate with other European partners even more intensively in the development of this optical clock. In the case of the Yb+ ion, it is of particular interest that it has two transitions which are suitable for optical clocks: Less strongly forbidden, but also very precise, the excitation of the D-level can be used at a wavelength of 436 nm. This opens up the possibility of investigating the accuracy of the optical clock by frequency comparisons of the two transitions in one ion, without having to refer to a caesium clock.

New Form of Carbon Nanotube

noreply@blogger.com (W.A.P.S.Madusanka) — Mon, 19 Mar 2012 15:30:00 +0000

Next-generation body armor and batteries could be within reach according to a group of Drexel University engineers who recently presented their work with a sophisticated weave of carbon nanotubes, commonly called buckypaper, in ACS NanoThe researchers, led by Dr. Christopher Li, a professor in Drexel’s Materials Science and Engineering Department, reported the process to fabricate a new form of buckypaper using a nano hybrid structure resembling a shish kebab. In the shish kebab the “skewers” are nanotubes and polymer crystal are the “kebabs” that hold the nanotubes apart. Li demonstrated that the crystals allow researchers to control the pores’ sizes and change the buckypaper’s conductivities, surface roughness and abilities to shed water.“This research shows that we can use this ‘shish-kebab’ instead of the carbon nanotube itself to build a three-dimensional membrane with controlled pore size, so this opens up a playground for using it for electrochemical devices such as batteries,” Li said.Standard buckypaper is formed by depositing a very thin layer of entangled carbon nanotubes to create a fiber mat akin to office paper. Li and colleagues note that no existing post-processing method allows researchers to increase the size of the tiny holes, or pores, between the carbon nanotubes after they form the buckypaper. Li’s group looked for a way to do that and to introduce other substances to buckypaper that could make it more useful in electronics or as sensors.

Nuclear clean-up

noreply@blogger.com (W.A.P.S.Madusanka) — Mon, 19 Mar 2012 09:30:00 +0000

Scientists have produced a previously unseen uranium molecule, in a development that could help improve clean-up processes for nuclear waste. The distinctive butterfly-shaped compound is similar to radioactive molecules that scientists had proposed to be key components of nuclear waste, but were thought too unstable to exist for long.

Researchers have shown the compound to be robust, which implies that molecules with a similar structure may be present in radioactive waste. Scientists at the University of Edinburgh, who carried out the study, say this suggests the molecule may play a role in forming clusters of radioactive material in waste that are difficult to separate during clean-up. Improving treatment processes for nuclear waste, including targeting this type of molecule, could help the nuclear industry move towards cleaner power generation, in which all the radioactive materials from spent fuel can be recovered and made safe or used again. This would reduce the amount of waste and curb risks to the environment.

The Edinburgh team worked in collaboration with scientists in the US and Canada to verify the structure of the uranium compound. They made the molecule by reacting a common uranium compound with a nitrogen and carbon-based material. Scientists used chemical and mathematical analyses to confirm the structure of the molecule’s distinctive butterfly shape.Professor Polly Arnold of the University of Edinburgh’s School of Chemistry, who took part in the research, said: “We have made a molecule that, in theory, should not exist, because its bridge-shaped structure suggests it would quickly react with other chemicals. This discovery that this particular form of uranium is so stable could help optimise processes to recycle valuable radioactive materials and so help manage the UK’s nuclear legacy.”

Origami-inspired sensor

noreply@blogger.com (W.A.P.S.Madusanka) — Mon, 19 Mar 2012 03:30:00 +0000

Inspired by the paper-folding art of origami, chemists at The University of Texas at Austin have developed a 3-D paper sensor that may be able to test for diseases such as malaria and HIV for less than 10 cents a pop.

This origami-inspired paper sensor, developed by chemists Hong Liu and Richard Crooks, can be easily assembled by hand. It may soon be able to inexpensively test for diseases like malaria and HIV. Such low-cost, “point-of-care” sensors could be incredibly useful in the developing world, where the resources often don’t exist to pay for lab-based tests, and where, even if the money is available, the infrastructure often doesn’t exist to transport biological samples to the lab.“This is about medicine for everybody,” says Richard Crooks, the Robert A. Welch Professor of Chemistry.

One-dimensional paper sensors, such as those used in pregnancy tests, are already common but have limitations. The folded, 3-D sensors, developed by Crooks and doctoral student Hong Liu, can test for more substances in a smaller surface area and provide results for more complex tests.“Anybody can fold them up,” says Crooks. “You don’t need a specialist, so you could easily imagine an NGO with some volunteers folding these things up and passing them out. They’re easy to produce, so the production could be shifted to the clientele as well. They don’t need to be made in the developed world.”

The results of the team’s experiments with the origami Paper Analytical Device, or oPAD, were published in October in the Journal of the American Chemical Society and last week in Analytical Chemistry. The inspiration for the sensor came when Liu read a pioneering paper by Harvard University chemist George Whitesides. Whitesides was the first to build a three-dimensional “microfluidic” paper sensor that could test for biological targets. His sensor, however, was expensive and time-consuming to make, and was constructed in a way that limited its uses.

“They had to pattern several pieces of paper using photolithography, cut them with lasers, and then tape them together with two-sided tape,” says Liu, a member of Crooks’ lab. “When I read the paper, I remembered when I was a child growing up in China, and our teacher taught us origami. I realized it didn’t have to be so difficult. It can be very easy. Just fold the paper, and then apply pressure.” Within a few weeks of experiments, Liu had fabricated the sensor on one simple sheet using photolithography or simply an office printer they have in the lab. Folding it over into multiple layers takes less than a minute and requires no tools or special alignment techniques. Just fingers.

Crooks says that the principles underlying the sensor, which they’ve successfully tested on glucose and a common protein, are related to the home pregnancy test. A hydrophobic material, such as wax or photoresist, is laid down into tiny canyons on chromatography paper. It channels the sample that’s being tested — urine, blood, or saliva, for instance — to spots on the paper where test reagents have been embedded. If the sample has whatever targets the sensor is designed to detect, it’ll react in an easily detectable manner. It might turn a specific color, for instance, or fluoresce under a UV light. Then it can be read by eye. “Biomarkers for all kinds of diseases already exist,” says Crooks. “Basically you spot-test reagents for these markers on these paper fluidics. They’re entrapped there. Then you introduce your sample. At the end you unfold this piece of paper, and if it’s one color, you’ve got a problem, and if not, then you’re probably OK.”

Crooks and Liu have also engineered a way to add a simple battery to their sensor so that it can run tests that require power. Their prototype uses aluminum foil and looks for glucose in urine. Crooks estimates that including such a battery would add only a few cents to the cost of producing the sensor.

“You just pee on it and it lights up,” says Crooks. “The urine has enough salt that it activates the battery. It acts as the electrolyte for the battery.”

Scientists revolutionise electron microscope

noreply@blogger.com (W.A.P.S.Madusanka) — Sun, 18 Mar 2012 21:30:00 +0000

For over 70 years, transmission electron microscopy (TEM), which `looks through´ an object to see atomic features within it, has been constrained by the relatively poor lenses which are used to form the image.

The new method, called electron ptychography, dispenses with the lens and instead forms the image by reconstructing the scattered electron-waves after they have passed through the sample using computers.

Scientists involved in the scheme consider their findings to be a `first step´ in a `completely new epoch of electron imaging´. The process has no fundamental experimental boundaries and it is thought it will transform sub-atomic scale transmission imaging.

Project leader Professor John Rodenburg, of the University of Sheffield´s Department of Electronic and Electrical Engineering, said: "To understand how material behaves, we need to know exactly where the atoms are. This approach will enable us to look at how atoms sit next to one another in a solid object as if we´re holding them in our hands.

"We´ve shown we can improve upon the resolution limit of an electron lens by a factor of five. An extension of the same method should reach the highest resolution transmission image ever obtained; about one tenth of an atomic diameter. No longer does TEM have to be bound by the paradigm of the lens, its Achilles´ heel since its invention in 1933."

The technique is applicable to microscopes using any type of wave and has other key advantages over conventional methods. For example, when used with visible light, the new technology forms a type of image that means scientists can see living cells very clearly without the need to stain them, a process which usually kills the cells.

The new method also disposes of the need to put a lens very close to a living sample, meaning that cells can be seen through thick containers like petri dishes or flasks. This means that as they develop and grow over days or weeks, they do not have to be disturbed.

Plans are even being put into place with the European Space Agency to take the new, more robust, microscope technology to the moon in 2018 to examine the structure of moon soil.

Professor Rodenburg added: "We measure diffraction patterns rather than images. What we record is equivalent to the strength of the electron, X-ray or light waves which have been scattered by the object – this is called their intensity. However, to make an image, we need to know when the peaks and troughs of the waves arrive at the detector – this is called their phase.

"The key breakthrough has been to develop a way to calculate the phase of the waves from their intensity alone. Once we have this, we can work out backwards what the waves were scattered from: that is, we can form an aberration-free image of the object, which is much better than can be achieved with a normal lens.

"A typical electron or X-ray microscope image is about one hundred times more blurred than the theoretical limit defined by the wavelength. In this project, the eventual aim is to get the best-ever pictures of individual atoms in any structure seen within a three-dimensional object."

The ground-breaking results were part of a three-year study costing £4.3 million which was funded by the Engineering and Physical Sciences Research Council (EPSRC).

The investigation was carried out with the help of Phase Focus Ltd, a University of Sheffield spin-out company, and Gatan Inc.

Ptychographic electron microscopy using high-angle dark-field scattering for sub-nanometre resolution imaging was published in Nature Communications.

This story is reprinted from material from the University of Sheffield, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.

Seaweed biofuels

noreply@blogger.com (W.A.P.S.Madusanka) — Sun, 18 Mar 2012 15:30:00 +0000

As scientists continue the hunt for energy sources that are safer, cleaner alternatives to fossil fuel, an ever-increasing amount of valuable farmland is being used to produce bioethanol, a source of transportation fuel. And while land-bound sources are renewable, economists and ecologists fear that diverting crops to produce fuel will limit food resources and drive up costs.

Now, Prof. Avigdor Abelson of Tel Aviv University's Department of Zoology and the new Renewable Energy Center, and his colleagues Dr. Alvaro Israel of the Israel Oceanography Institute, Prof. Aharon Gedanken of Bar-Ilan University, Dr. Ariel Kushmaro of Ben-Gurion University, and their Ph.D. student Leor Korzen, have gone to the seas in the quest for a renewable energy source that doesn't endanger natural habitats, biodiversity, or human food sources. He says that marine macroalgae — common seaweed — can be grown more quickly than land-based crops and harvested as fuel without sacrificing usable land. It's a promising source of bioethanol that has remained virtually unexplored until now.

The researchers are now developing methods for growing and harvesting seaweed as a source of renewable energy. Not only can the macroalgae be grown unobtrusively along coastlines, Prof. Abelson notes, they can also clear the water of excessive nutrients — caused by human waste or aquaculture — which disturb the marine environment.

While biomasses grown on land have the potential to inflict damage on the environment, the researchers believe that producing biofuel from seaweed-based sources could even solve problems that already exist within the marine environment. Many coastal regions, including the Red Sea in the south of Israel, have suffered from eutrophication — pollution caused by human waste and fish farming, which leads to excessive amounts of nutrients and detrimental algae, ultimately harming endangered coral reefs.

Encouraging the growth of seaweed for eventual conversion into biofuel could solve these environmental problems. The system that the researchers are developing, called the "Combined Aquaculture Multi-Use Systems" (CAMUS), takes into account the realities of the marine environment and human activity in it. Ultimately, all of these factors function together to create a synthetic "man-made ecosystem," explains Prof. Abelson.

Man-made fish feeders, which produce pollution in the form of excess nutrients and are generally considered harmful to the marine environment, would become a positive link in this chain. Used alongside an increased population of filter feeders such as oysters, which suck in extra particles and convert them food that the microalgae can consume, this "pollution" could be used to sustain a much greater yield of seaweed, which is needed for seaweed to become a sustainable source of fuel."By employing multiple species, CAMUS can turn waste into productive resources such as biofuel, at the same time reducing pollution's impact on the local ecosystem," he says.

The researchers are now working to increase the carbohydrate and sugar contents of the seaweed for efficient fermentation into bioethanol, and they believe that macroalgae will be a major source for biofuel in the future. The CAMUS system could turn seaweed into a sustainable bioethanol source that is productive, efficient, and cost-effective.

Spider silk conduction

noreply@blogger.com (W.A.P.S.Madusanka) — Sun, 18 Mar 2012 09:30:00 +0000

Xinwei Wang had a hunch that spider webs were worth a much closer look. So he ordered eight spiders - Nephila clavipes, golden silk orbweavers - and put them to work eating crickets and spinning webs in the cages he set up in an Iowa State University greenhouse.
Wang, an associate professor of mechanical engineering at Iowa State, studies thermal conductivity, the ability of materials to conduct heat. He's been looking for organic materials that can effectively transfer heat. It's something diamonds, copper and aluminum are very good at; most materials from living things aren't very good at all. But spider silk has some interesting properties: it's very strong, very stretchy, only 4 microns thick (human hair is about 60 microns) and, according to some speculation, could be a good conductor of heat. But nobody had actually tested spider silk for its thermal conductivity.

Wang, with partial support from the Army Research Office and the National Science Foundation, decided to try some lab experiments. Xiaopeng Huang, a post-doctoral research associate in mechanical engineering; and Guoqing Liu, a doctoral student in mechanical engineering, helped with the project. "I think we tried the right material," Wang said of the results. What Wang and his research team found was that spider silks - particularly the draglines that anchor webs in place - conduct heat better than most materials, including very good conductors such as silicon, aluminum and pure iron. Spider silk also conducts heat 1,000 times better than woven silkworm silk and 800 times better than other organic tissues.

A paper about the discovery - "New Secrets of Spider Silk: Exceptionally High Thermal Conductivity and its Abnormal Change under Stretching" - has just been published online by the journal Advanced Materials. "Our discoveries will revolutionize the conventional thought on the low thermal conductivity of biological materials," Wang wrote in the paper. The paper reports that using laboratory techniques developed by Wang - "this takes time and patience" - spider silk conducts heat at the rate of 416 watts per meter Kelvin. Copper measures 401. And skin tissues measure .6. "This is very surprising because spider silk is organic material," Wang said. "For organic material, this is the highest ever. There are only a few materials higher - silver and diamond." Even more surprising, he said, is when spider silk is stretched, thermal conductivity also goes up. Wang said stretching spider silk to its 20 percent limit also increases conductivity by 20 percent. Most materials lose thermal conductivity when they're stretched. That discovery "opens a door for soft materials to be another option for thermal conductivity tuning," Wang wrote in the paper. And that could lead to spider silk helping to create flexible, heat-dissipating parts for electronics, better clothes for hot weather, bandages that don't trap heat and many other everyday applications.

What is it about spider silk that gives it these unusual heat-carrying properties? Wang said it's all about the defect-free molecular structure of spider silk, including proteins that contain nanocrystals and the spring-shaped structures connecting the proteins. He said more research needs to be done to fully understand spider silk's heat-conducting abilities. Wang is also wondering if spider silk can be modified in ways that enhance its thermal conductivity. He said the researchers' preliminary results are very promising. And then Wang marveled at what he's learning about spider webs, everything from spider care to web unraveling techniques to the different silks within a single web. All that has one colleague calling him Iowa State's Spiderman.

"I've been doing thermal transport for many years," Wang said. "This is the most exciting thing, what I'm doing right now."

Super(capacitor) storage

noreply@blogger.com (W.A.P.S.Madusanka) — Sun, 18 Mar 2012 03:30:00 +0000

Drexel UniversityElsevier Ltd is not responsible for the content of external websites.Nano bundles pack a powerful punch

Solid-state energy storage takes a leap forward at Rice University Seaweed polymer electrodes
Improved lithium-ion batteries Graphene nanosheet electrodes
Superior energy capacity for lithium-oxygen batteries Supercapacitors take power
In a paper published in the April journal of Science, titled “Monolithic Carbide-Derived Carbon Films for Micro-Supercapacitors”, Chmiola and Yury Gogotsi of Drexel University, along with other co-authors, [Chmiola et al., Science (2010) 328, 480] describe a unique new technique for integrating high performance micro-sized supercapacitors into a variety of portable electronic devices through common microfabrication techniques. Printable power using carbon nanotube supercapacitors
Portable electronic devices such as mobile phones, netbooks, and cameras are becoming increasingly more important to our society. How rarely we leave the house without our trusty iPhone or Blackberry!

An international team of materials researchers including Drexel University’s Dr. Yury Gogotsi has given the engineering world a better look at the inner functions of the electrodes of supercapacitors – the low-cost, lightweight energy storage devices used in many electronics, transportation and many other applications. In a piece published in Nature Materials, Gogotsi, and his collaborators from universities in France and England, take another step toward finding a solution to the world’s demand for sustainable energy sources. Gogotsi, a professor in Drexel’s College of Engineering and director of the A.J. Drexel Nanotechnology Institute, teamed with Mathieu Salanne, Céline Merlet and Benjamin Rotenberg from the Université Paris 06, Paul A. Madden from Oxford University and Patrice Simon and Pierre-Louis Taberna of Université Paul Sabatier. What the group has produced is the first quantitative picture of the structure of ionic liquid absorbed inside disordered microporous carbon electrodes in supercapacitors. Supercapacitors have the capability of storing and delivering more power than batteries; moreover, they can last for up to a million of charge-discharge cycles. These characteristics are significant because of the intermittent nature of renewable energy production.According to the researchers, the excellent performance of supercapacitors is due to ion adsorption in porous carbon electrodes. The molecular mechanism of ion behavior in pores smaller than one nanometer-one billionth of a meter- remains poorly understood. The mechanism proposed in this research opens the door for the design of materials with improved energy storage capabilities.The authors suggest that in order to build higher-performance materials, researchers should know whether the increase in energy storage is due to only a large surface area or if the pore size and geometry also play a role. The results of this study provide guidance for development of better electrical energy storage devices that will ultimately enable wide utilization of renewable energy sources. “This breakthrough in understanding of energy storage mechanisms became possible due to collaboration between research groups from four universities in three countries,” Gogotsi said. “Moreover, the team used carbon structure models developed by our colleagues Dr. Jeremy Palmer and Dr. Keith Gubbins from the North Carolina State University. This is a clear demonstration of the importance of collaboration between scientists working in different disciplines and even in different countries.”

Supersticky nanoglue

noreply@blogger.com (W.A.P.S.Madusanka) — Sat, 17 Mar 2012 15:22:00 +0000

Engineers at the University of California, Davis, have invented a superthin “nanoglue” that could be used in new-generation microchip fabrication. “The material itself (say, semiconductor wafers) would break before the glue peels off,” said Tingrui Pan, professor of biomedical engineering. He and his fellow researchers have filed a provisional patent.Conventional glues form a thick layer between two surfaces. Pan’s nanoglue, which conducts heat and can be printed, or applied, in patterns, forms a layer the thickness of only a few molecules. The nanoglue is based on a transparent, flexible material called polydimethylsiloxane, or PDMS, which, when peeled off a smooth surface usually leaves behind an ultrathin, sticky residue that researchers had mostly regarded as a nuisance. Pan and his colleagues realized that this residue could instead be used as glue, and enhanced its bonding properties by treating the residue surface with oxygen.The nanoglue could be used to stick silicon wafers into a stack to make new types of multilayered computer chips. Pan said he thinks it could also be used for home applications — for example, as double-sided tape or for sticking objects to tiles. The glue only works on smooth surfaces and can be removed with heat treatment.The National Science Foundation supported the work.

Fatigue Crack Propagation

noreply@blogger.com (W.A.P.S.Madusanka) — Tue, 13 Mar 2012 08:26:00 +0000

Basically, fatigue crack propagation can be divided into three stages: stage I (short cracks), stage II (long cracks) and stage III (final fracture).

• Stage I: Once initiated, a fatigue crack propagates along high shear stress planes (45 degrees), as schematically represented in Fig. 1. This is known as stage I or the short crack growth propagation stage. The crack propagates until it is decelerated by a microstructural barrier such as a grain boundary, inclusions, or pearlitic zones, which cannot accommodate the initial crack growth direction. Therefore, grain refinement is capable of increasing fatigue strength of the material by the insertion of a large quantity of microstructural barriers, i.e. grain boundaries, which have to be overcome in the stage I of propagation. Surface mechanical treatments such as shot peening and surface rolling, contribute to the increase in the number of microstructural barriers per unit of length due to the flattening of the grains.

• Stage II: When the stress intensity factor K increases as a consequence of crack growth or higher applied loads, slips start to develop in different planes close to the crack tip, initiating stage II. While stage I is orientated 45 degrees in relation to the applied load, propagation in stage II is perpendicular to the load direction, as depicted in Fig. 1. An important characteristic of stage II is the presence of surface ripples known as “striations,” which are visible with the aid of a scanning electron microscope. Not all engineering materials exhibit striations. They are clearly seen in pure metals and many ductile alloys such as aluminum. In steels, they are frequently observed in cold-worked alloys. Figure 2 shows examples of fatigue striations in an interstitial-free steel and in aluminum alloys. The most accepted mechanism for the formation of striations on the fatigue fracture surface of ductile metals, is the successive blunting and re-sharpening of the crack tip.

• Stage III: Finally, stage III is related to unstable crack growth as Kmax approaches KIC. At this stage, crack growth is controlled by static modes of failure and is very sensitive to the microstructure, load ratio, and stress state (plane stress or plane strain loading). Macroscopically, the fatigue fracture surface can be divided into two distinct regions, as shown by Fig. 4.The first region corresponds to the stable fatigue crack growth and presents a smooth aspect due to the friction between the crack wake faces. Sometimes, concentric marks known as “beach marks” can be seen on the fatigue fracture surface, as a result of successive arrests or decrease in the rate of fatigue crack growth due to a temporary load drop, or due to an overload that introduces a compressive residual stress field ahead of the crack tip.

• Final fracture: The other region corresponds to the final fracture and presents a fibrous and irregular aspect. In this region, the fracture can be either brittle or ductile, depending on the mechanical properties of the material, dimensions of the part, and loading conditions. The exact fraction of area of each region depends on the applied load level. High applied loads result in a small stable crack propagation area, as depicted in Fig. 4. On the other hand, if lower loads are applied, the crack will have to grow longer before the applied stress intensity factor K, reaches the fracture toughness value of the material, resulting in a smaller area of fast fracture, Fig. 4b.

• Ratcheting marks: Ratcheting

marks are another macroscopic feature that can be observed in fatigue fracture surfaces. These marks originate when multiple cracks, nucleated at different points, join together, creating steps on the fracture surface. Therefore, counting the number of ratchet marks is a good indication of the number of nucleation sites. Figure 5 presents in

detail some ratchet marks found on the fracture surface of a large SAE 1045 rotating shaft fractured by fatigue.

Shrimp-like crustacean makes underwater silk

noreply@blogger.com (W.A.P.S.Madusanka) — Wed, 07 Mar 2012 04:00:00 +0000

Oxford University (UK) researchers discovered a novel silk production system in a marine

amphipod that provides insights into the wider potential of natural silks. The tube-building corophioid amphipod Crassicorophium bonellii produces a material that is sort of a combination between the cement barnacles use to affix themselves to rocks and ship hulls, and spider silk. If duplicated in an industrial process, it could lead to beneficial materials for use in medical implant products. www.ox.ac.uk.

High-tech spider for hazardous missions

noreply@blogger.com (W.A.P.S.Madusanka) — Tue, 06 Mar 2012 04:38:00 +0000

Researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA, Germany, designed a mobile robot modeled on the same principle that moves spider legs. Created using a 3-D printing process, it can explore terrain that is beyond human reach; making its way through grounds rendered off-limits to humans as the result of a chemical accident. With a camera and measurement equipment on board, it provides emergency responders with an image of the situation on the ground, along with any data about poisonous substances.

www.ipa.fraunhofer.de.

Materials science & engineering is a challenging field in the world

noreply@blogger.com (W.A.P.S.Madusanka) — Mon, 05 Mar 2012 16:03:00 +0000

Materials Science and Engineering (MS&E) is a broad, multidisciplinary field devoted to understanding and manipulating the mechanical, electrical, optical and magnetic properties of materials. Materials science focuses on understanding fundamental mechanisms that determine and define these properties, and the influence that various processes have on them. Materials engineering, in contrast, involves the deliberate synthesis, chemical and physical modification, and processing of natural materials to meet specific requirements for advanced technologies.

For many engineering fields, ultimate product capabilities are often determined by the underlying materials' limits — for example, the strength-to-weight ratio of a carbon fiber composite in a tennis racket or the wear resistance and biocompatability of materials for hip joint replacements. Materials engineers are often at the core of new product development, from initial design through manufacturing. For these reasons, professionals in MS&E are employed today in almost every industry, from aerospace giants such as Boeing to microelectronics manufacturers including Intel and Motorola.

The field of materials science and engineering is broad and diverse. Students majoring in the field normally specialize in one or two areas. These areas include general materials science, metallurgy, optical and electronic materials, ceramics, polymers, biomaterials, chemical synthesis, or solid state physics. Specialization comes with selecting technical breadth and depth elective courses in the junior and senior years. These courses are chosen from both MS&E and related fields such as electrical and computer engineering, or chemical engineering.

An attractive and challenging program combines materials science and engineering with electrical or mechanical engineering, leading to a double major. The MS&E double major with electrical engineering is particularly well suited to students with an interest in working the electronic materials industry. The double major with mechanical engineering will prepare students for positions that will call on all skills in both mechanical design and the complex properties of the material used in building advanced devices.

In professional practice, MS&E requires strong laboratory skills. Students in the field are strongly encouraged to become involved in research at some point in their undergraduate careers, either in a paid position or for academic credit. During a typical academic year, sixty or more MS&E undergraduate students are engaged in state-of-the-art research working directly with the faculty and graduate students. source :

http://www.engineering.cornell.edu/academics/undergraduate/curriculum/Majors/mse.cfm

Fool’s gold (NOT GOLD) leads to new options for cheap solar energy

noreply@blogger.com (W.A.P.S.Madusanka) — Mon, 05 Mar 2012 04:30:00 +0000

Pyrite (iron sulphide), better known as fool’s gold, helped researchers at Oregon State Univer sity, Corvallis, discover related compounds that offer new, inexpensive, and promising options for solar energy. The new compounds, unlike some solar cell materials made of rare, expensive, or toxic elements, are benign and could be processed from some of the most abundant ele-ments on Earth.

Pyrite was of interest early in the solar en-ergy era because it had an enormous capacity to absorb solar energy, was abundant, and could be used in layers 2000 times thinner than some of its competitors, such as silicon. However, it did not effectively convert the solar energy into elec-tricity because, in extreme heat, it starts to de-compose and forms products that prevent the creation of electricity. Because of this understanding, researchers sought and found com-pounds that had the same capabilities of pyrite but didn’t decompose. One of them was iron silicon sulfide. www.oregonstate.edu.