Tracking Down Builders Of Homemade Bombs

Source:

http://www.sciencedaily.com/releases/2007/09/070917150439.htm

Science Daily — Researchers in Australia are reporting development of a portable device to help track down builders of improvised explosive devices (IEDs) -- those homemade fertilizer bombs that have wreaked such havoc in terrorist attacks around the world.

Paul R. Haddad and colleagues point out that IEDs have become a mainstay weapon for terrorists, resulting in an urgent need for new technology to identify and eliminate the sources of the explosives. However, quickly and reliably identifying the chemicals used in these crude but deadly bombs remains a major challenge to investigators. IEDs are often made with a diverse array of conventional, easy-to-obtain materials that require slow and painstaking analysis in the laboratory following an explosion.
The new technology streamlines that process, quickly and accurately identifying the chemical composition of blast residues from IEDs in the field. It consists of an instrument, about the size of a briefcase, based on a modified form of capillary electrophoresis, a mainstay technology for separating components in a mixture. In the study, researchers used it to identify major components of blast residues in less than 10 minutes.
Their study will appear in the Sept. 15 issue of ACS' Analytical Chemistry.
Article: "Identification of Inorganic Improvised Explosive Devices by Analysis of Postblast Residues Using Portable Capillary Electrophoresis Instrumentation and Indirect Photometric Detection with a Light-Emitting Diode"
Note: This story has been adapted from a news release issued by American Chemical Society.

Fausto Intilla

www.oloscience.com

Salmon DNA Points The Way To Green Electronics

Source:

http://www.sciencedaily.com/releases/2007/09/070913132937.htm

Science Daily — Professor Andrew Steckl, a leading expert in light-emitting diodes, is intensifying the properties of LEDs by introducing biological materials, specifically salmon DNA.

Electrons move constantly — think of tiny particles with a negative charge and attention deficit disorder. It is through the movement of these electrons that electric current flows and light is created.
Steckl is an Ohio Eminent Scholar in UC’s Department of Electrical and Computer Engineering. He believed that if the electrons’ mobility could be manipulated, then new properties could be revealed.
In considering materials to introduce to affect the movement of the electrons, Steckl evaluated the source of materials with an eye to supply, especially materials that do not harm the environment.
“Biological materials have many technologically important qualities — electronic, optical, structural, magnetic,” says Steckl. “But certain materials are hard for to duplicate, such as DNA and proteins.” He also wanted a source that was widely available, would not have to be mined, and was not subject to any organization or country’s monopoly. His answer?
Salmon sperm.
“Salmon sperm is considered a waste product of the fishing industry. It’s thrown away by the ton,” says Steckl with a smile. “It’s natural, renewable and perfectly biodegradable.” While Steckl is currently using DNA from salmon, he thinks that other animal or plant sources might be equally useful. And he points out that for the United States, the green device approach takes advantage of something in which we continue to be a world leader — agriculture.
Steckl is pursuing this research in collaboration with the Air Force Research Laboratory. The research was featured recently in Naturephotonics and Applied Physics Letters.
“The Air Force had already been working with DNA for other applications when they came to us and said, ‘We know that you know how to make devices,’” quotes Steckl. “They also knew that they had a good source of salmon DNA.” It was a match made in heaven.
So began Steckl’s work with BioLEDs, devices that incorporate DNA thin films as electron blocking layers. Most of the devices existing today are based on inorganic materials, such as silicon. In the last decade, researchers have been exploring using naturally occurring materials in devices like diodes and transistors.
“The driving force, of course, is cost: cost to the producer, cost to the consumer and cost to the environment” Steckl points out, “but performance has to follow.”
And what a performance — lights, camera, action!
“DNA has certain optical properties that make it unique,” Steckl says. “It allows improvements in one to two orders of magnitude in terms of efficiency, light, brightness — because we can trap electrons longer.”
When electrons collide with oppositely charged particles, they produce very tiny packets of light called “photons.”
“Some of the electrons rushing by have a chance to say ‘hello,’ and get that photon out before they pass out,” Steckl explains. “The more electrons we can keep around, the more photons we can generate.” That’s where the DNA comes in, thanks to a bunch of salmon.
BioLEDs make colors brighter.
“DNA serves as a barrier that affects the motion of the electrons,” says Steckl. It allows Steckl and his fellow researcher, the Air Force’s Dr. James Grote, to control the brightness of the light that comes out.
“The story continues,” says Steckl, again smiling. “I’m receiving salmon sperm from researchers around the world wanting to see if their sperm is good enough.” The next step is to now replace some other materials that go into an LED with biomaterials. The long-term goal is be able to make “green” devices that use only natural, renewable and biodegradable materials.
This research was funded by the United States Air Force.
Here we have the “yin” of biological materials in photonic devices. See Steckl’s “yang” research placing electronics in biological materials: UC Engineering Research Widens Possibilities for Electronic Devices: NSF-funded engineering research on microfluidics at the University of Cincinnati widens the possibilities on the horizon for electronic devices.
Note: This story has been adapted from a news release issued by University of Cincinnati.

Fausto Intilla

www.oloscience.com

Ability To Write And Store Information On Electronic Devices Improved

Source:

http://www.sciencedaily.com/releases/2007/09/070913165155.htm

Science Daily — New research led by the U.S. Department of Energy's Argonne National Laboratory physicist Matthias Bode provides a more thorough understanding of new mechanisms, which makes it possible to switch a magnetic nanoparticle without any magnetic field and may enable computers to more accurately write and store information.

Bode and four colleagues at the University of Hamburg used a special scanning tunneling microscope equipped with a magnetic probe tip to force a spin current through a small magnetic structure. The researchers were able to show that the structure's magnetization direction is not affected by a small current, but can be influenced if the spin current is sufficiently high.
Most computers today use dynamic random access memory, or DRAM, in which each piece of binary digital information, or bit, is stored in an individual capacitor in an integrated circuit. Bode's experiment focused on magneto-resistive random access memory, or MRAM, which stores data in magnetic storage elements consisting of two ferromagnetic layers separated by a thin non-magnetic spacer. While one of the two layers remains polarized in a constant direction, the other layer becomes polarized through the application of an external magnetic field either in the same direction as the top layer (for a "0") or in the opposite direction (for a "1").
Traditionally, MRAM are switched by magnetic fields. As the bit size has shrunk in each successive generation of computers in order to accommodate more memory in the same physical area, however, they have become more and more susceptible to "false writes" or "far-field" effects, Bode said. In this situation, the magnetic field may switch the magnetization not only of the target bit but of its neighbors as well. By using the tip of the Scanning Tunneling Microscope (STM), which has the potential to resolve structures down to a single atom, the scientists were able to eliminate that effect.
Bode and his colleagues were the first ones who did such work with an STM that generates high spatial-resolution data. "If you now push just a current through this bit, there's no current through the next structure over," Bode said. "This is a really local way of writing information."
The high resolution of the STM tip might enable scientists to look for small impurities in the magnetic storage structures and to investigate how they affect the magnet's polarization. This technique could lead to the discovery of a material or a method to make bit switching more efficient. "If you find that one impurity helps to switch the structure, you might be able to intentionally dope the magnet such that it switches at lower currents," Bode said.
Results of this research were published in the September 14 issue of Science and related research was published earlier this year in Nature.
Funding for this work was provided by Deutsche Forschungsgemeinschaft and the European Union project ASPRINT. This work was conducted prior to Bode's arrival at Argonne. His research at Argonne will be predominately funded by DOE's Office of Basic Energy Sciences.
Note: This story has been adapted from a news release issued by DOE/Argonne National Laboratory.

Fausto Intilla

www.oloscience.com

Smallest Piece Of Art Ever Printed Could Herald Ultra-Tiny Nanowires, Biosensors And Optics For Future Chips

Source:

http://www.sciencedaily.com/releases/2007/09/070911210113.htm

Science Daily — IBM researchers in collaboration with scientists from the ETH Zurich have demonstrated a new, efficient and precise technique to “print” at the nanoscale.

The method, which allows the scientists to place individual particles precisely where they want them, could advance the development of nanoscale biosensors, ultra-tiny lenses that can bend light inside future optical chips, and the fabrication of nanowires that might be the basis of tomorrow’s computer chips.
Though still a few years from being used widely, the new technique shows promise for real world applications outside of the lab without major profound new inventions, and could lead to high-volume manufacturing techniques for nanostructures inside chips and other devices that are more efficient and cost less than today’s methods.
“This method opens up new ways to precisely and efficiently position various kinds of nanoparticles on different surfaces, a prerequisite for exploiting the unique properties of such nanoparticles and for making their use economically feasible,” explains Heiko Wolf, researcher in nanopatterning at IBM’s Zurich Research lab.
The achievement, published in the September issue of the journal Nature Nanotechnology, offers a promising and powerful new tool for use in a wide range of fields and industries such as biomedicine, electronics and IT that seek ways to exploit the often unique properties of so-called nanoparticles, which are defined as particles smaller than 100 nanometers.
Until now, standard top-down micro-fabrication techniques produce such tiny particles by in effect carving them out of a bigger piece of material. Printing, in contrast, adds ready-made nanoparticles onto a surface in a very efficient way and allows for different types of materials such as metals, polymers, semiconductors, and oxides to be combined in one process.
For the first time, the researchers printed particles as tiny as 60 nanometers -- roughly 100 times smaller than a human red blood cell -- with single-particle resolution to create nano-patterns ranging from simple lines to complex arrangements. Translating the resolution of these particles into a traditional printing term known as “dots per inch” or dpi, a standard measure that defines how many individual spots of ink can be printed on a certain area, the nanoprinting method yields 100,000 dots per inch, whereas common offset printing today operates at 1,500 dpi.
To demonstrate the efficiency and the versatility of their method, the researchers chose to print Robert Fludd’s 17th-century image of the sun, the alchemists’ symbol for gold. Quite fittingly, it is printed out of roughly 20,000 gold particles, each of them 60 nanometers in diameter. The printing method precisely placed one particle per dot, thus creating the smallest piece of artwork ever printed from single pigment particles.
Nanoprinting Applications
In biomedicine this printing process could, for example, be applied to the printing of large arrays of biofunctional beads that can detect and identify certain cells or markers in the body. One example could be rapid screening for cancer cells or heart attack markers. As part of new point-of-care diagnostic devices, regular arrays of functional beads could enable a fast and automated read-out that only needs the tiniest amounts of samples.
Nanoparticles can also interact with light. With the new method, optical materials with new properties could be printed, for example, for use in optoelectronic devices. So-called “metamaterials” could be created in which the printed structures are as small as the wavelength of the light and therefore act as if they were a single lens with unusual properties.
Moreover, the method holds promise for semiconductors. In one experiment, the researchers achieved the controlled placement of catalytic seed particles for growing semiconducting nanowires. Such nanowires are promising candidates for future transistors in microchips.
Printing on the Nanoscale
“In traditional gravure printing, a doctor blade is used to fill the recessed features of a printing plate with ink, in which pigment particles are randomly dispersed,” explains Tobias Kraus, of the nanopatterning team in Zurich. “In our high-resolution printing, a directed self-assembly process controls the arrangement of nanoparticles on the printing plate or template. The entire assembly is then printed onto a target surface, whereby the particle positions are precisely retained at a resolution that is three orders of magnitude higher than in conventional printing.”
The printing template geometries explored include lines to produce closely-packed nanoparticle wires, which could be used in molecular electronics; regularly spaced arrays of gold particles as seeds for nanowire growth; and arbitrary arrangements, such as the printed replica of the sun. The long-range accuracy, which measures the deviation from the desired arrangement on a large area, is similar to that of microcontact printing methods. The next steps will be to refine the method to achieve even higher accuracies, as would be required for large-scale integration in microelectronics, as well as to extend the method to print even smaller particles.
IBM’s Leadership in Nanotechnology
Today’s announcement builds on IBM’s leadership in nanotechnology: more than two decades after two IBM scientists won the Nobel Prize in Physics for their invention of the Scanning Tunneling Microscope (STM), which opened the door to the world of individual atoms for the first time, scientists and engineers from IBM Research continue to break new ground in nanoscience and technology.
The breakthrough also comes just two weeks after IBM unveiled two major scientific breakthroughs at the atomic scale: one a major step in understanding the ability for single atoms to maintain a specific magnetic direction, making them suitable for future data storage applications and the other a novel very robust and stable single-molecule switch that can be used as a modular building block for molecular computers.
Note: This story has been adapted from a news release issued by IBM.

Fausto Intilla

www.oloscience.com

Drawing Nanoscale Features The Fast And Easy Way

Source:

http://www.sciencedaily.com/releases/2007/09/070910110717.htm

Science Daily — Scientists at the Georgia Institute of Technology have developed a new technique for nanolithography that is extremely fast and capable of being used in a range of environments including air (outside a vacuum) and liquids.

Researchers have demonstrated the technique, known as thermochemical nanolithography, as a proof of concept. The technique may allow industry to produce a variety of nanopatterned structures, including nanocircuits, at a speed and scale that could make their manufacture commercially viable. The research, which has potential applications for fields ranging from the electronics industry to nanofluidics to medicine, appeared earlier this year in the journal Nano Letters.
The technique is surprisingly simple. Using an atomic force microscope (AFM), researchers heat a silicon tip and run it over a thin polymer film. The heat from the tip induces a chemical reaction at the surface of the film. This reaction changes the film’s chemical reactivity and transforms it from a hydrophobic substance to a hydrophilic one that can stick to other molecules. The technique is extremely fast and can write at speeds faster than millimeters per second. That’s orders of magnitude faster than the widely used dip-pen nanolithography (DPN), which routinely clocks at a speed of 0.0001 millimeters per second.
Using the new technique, researchers were able to pattern with dimensions down to 12 nanometers in width in a variety of environments. Other techniques typically require the addition of other chemicals to be transferred to the surface or the presence of strong electric fields. TCNL doesn’t have these requirements and can be used in humid environments outside a vacuum. By using an array of AFM tips developed by IBM, TCNL also has the potential to be massively scalable, allowing users to independently draw features with thousands of tips at a time rather than just one.
“Thermochemical nanolithography is a rapid and versatile technique that puts us much closer to achieving the speeds required for commercial applications,” said Elisa Riedo, assistant professor in Georgia Tech’s School of Physics. “Because we’re not transferring any materials from the AFM tip to the polymer surface (we are only heating it to change its chemical structure) this method can be intrinsically faster than other techniques.”
It’s the heated AFM tips that are one key to the new technique. Designed and fabricated by a group led by William King at the University of Illinois, the tips can reach temperatures hotter than 1,000 degrees Celsius. They can also be repeatedly heated and cooled 1 million times per second.
“The heated tip is the world’s smallest controllable heat source,” said King.
TCNL is also tunable. By varying the amount of heat, the speed and the distance of the tip to the polymer, researchers can introduce topographical changes or modulate the range of chemical changes produced in the material.
“By changing the chemistry of the polymer, we’ve shown that we can selectively attach new substances, like metal ions or dyes to the patterned regions of the film in order to greatly increase the technique’s functionality,” said Seth Marder, professor in Tech’s School of Chemistry and Biochemistry and director of the Center for Organic Photonics and Electronics. Marder’s group developed the thermally switchable polymers used in this study.
“We expect thermochemical nanolithography to be widely adopted because it’s conceptually simple and can be broadly applied,” said Marder. “The scope is limited only by one’s imagination to develop new chemistries and applications.”
For nanolithography to be commercially viable, it must be able to write at high speeds, be used in a variety of environments and write on a variety of materials. While the technique demonstrated here doesn’t yet allow writing at the centimeters per second rate that would be ideal, it does put researchers much closer to the goal than previous techniques. Once perfected, nanolithography could be used to draw nanocircuits for the electronics industry, create nanochannels for nanofluidics devices or be adapted for drug delivery or biosensing technologies. The research was supported by the National Science Foundation’s Center for Materials and Devices for Information Technology Research, the U.S. Department of Energy, the National Science Foundation, the Georgia Institute of Technology Research Foundation, the GT College of Sciences Cutting Edge Research Award and ONR Nanoelectronics. In addition to Riedo, Marder and King, the interdisciplinary research team consisted of Robert Szoszkiewicz, Takashi Okada, Simon Jones and Tai-De Li from Georgia Tech.
Note: This story has been adapted from a news release issued by Georgia Institute of Technology.

Fausto Intilla

www.oloscience.com

Single-Atom Data Storage, Single-Molecule Switching Could Lead To New Computer Devices

Source:

http://www.sciencedaily.com/releases/2007/09/070904081912.htm

Science Daily — IBM has announced two major scientific achievements in the field of nanotechnology that could one day lead to new kinds of devices and structures built from a few atoms or molecules.

Although still far from making their way into products, these breakthroughs will enable scientists at IBM and elsewhere to continue driving the field of nanotechnology, the exploration of building structures and devices out of ultra-tiny, atomic-scale components. Such devices might be used as future computer chips, storage devices, sensors and for applications nobody has imagined yet.
The work will be unveiled tomorrow in two reports being published by the journal Science.
In the first report, IBM scientists describe major progress in probing a property called magnetic anisotropy in individual atoms. This fundamental measurement has important technological consequences because it determines an atom’s ability to store information. Previously, nobody had been able to measure the magnetic anisotropy of a single atom.
With further work it may be possible to build structures consisting of small clusters of atoms, or even individual atoms, that could reliably store magnetic information. Such a storage capability would enable nearly 30,000 feature length movies or the entire contents of YouTube – millions of videos estimated to be more than 1,000 trillion bits of data – to fit in a device the size of an iPod. Perhaps more importantly, the breakthrough could lead to new kinds of structures and devices that are so small they could be applied to entire new fields and disciplines beyond traditional computing.
In the second report, IBM researchers unveiled the first single-molecule switch that can operate flawlessly without disrupting the molecule's outer frame -- a significant step toward building computing elements at the molecular scale that are vastly smaller, faster and use less energy than today's computer chips and memory devices.
In addition to switching within a single molecule, the researchers also demonstrated that atoms inside one molecule can be used to switch atoms in an adjacent molecule, representing a rudimentary logic element. This is made possible partly because the molecular framework is not disturbed.
The Science of The Small: Understanding the Magnetic Properties of Atoms
In the paper titled “Large Magnetic Anisotropy of a Single Atomic Spin Embedded in a Surface Molecular Network,” the researchers used IBM’s special scanning tunneling microscope (STM) to manipulate individual iron atoms and arranged them with atomic precision on a specially prepared copper surface. They then determined the orientation and strength of the magnetic anisotropy of the individual iron atoms.
Anisotropy is an important property for data storage because it determines whether or not a magnet can maintain a specific orientation. This in turn allows the magnet to represent either a “1” or “0,” which is the basis for storing data in computers.
“One of the major challenges for the IT industry today is shrinking the bit size used for data storage to the smallest possible features, while increasing the capacity,” said Gian-Luca Bona, manager of science and technology at the IBM Almaden Research Center in San Jose, California. “We are working at the ultimate edge of what is possible – and we are now one step closer to figuring out how to store data at the atomic level. Understanding the specific magnetic properties of atoms is the cornerstone of progressing toward new, more efficient ways to store data.”
Lilliputian Scale Devices: Single Molecule Logic Switching
In the paper titled “Current-Induced Hydrogen Tautomerization and Conductance Switching of Naphthalocyanine Molecules,” IBM researchers describe the ability to switch a single molecule “on” and “off,” a basic element of computer logic, using two hydrogen atoms within a naphthalocyanine organic molecule. Previously, researchers at IBM and elsewhere have demonstrated switching within single molecules, but the molecules would change their shape when switching, making them unsuitable for building logic gates for computer chips or memory elements.
Switches inside computer chips act like a light switch to turn the flow of electrons on and off and, when put together, make up the logic gates, which in turn make up electrical circuits. Having ever smaller switches allows the circuits to be shrunk to ever smaller sizes, making it possible to pack more circuits into a processor and boosting speed and performance.
These molecular switches could one day lead to computer chips with speeds as fast as today's fastest supercomputers, but much smaller in size; with some speculating even building computer chips so small they could be the size of a speck of dust or fit on the tip of a needle.
Development of conventional silicon-based CMOS chips is approaching its physical limits, and the IT industry is exploring new, truly disruptive technologies to achieve further increases in computer performance. Modular molecular logic is a possible candidate, though still several years from reality. The next step for the Research team is to build a series of these molecules into a circuit, then figure out how to network those together into a molecular chip.
The concept of using molecules as electronic components is still in its infancy. Only a few examples of individual molecules serving as switches or memory elements have been demonstrated to date. Most of these molecules are complex, three-dimensional structures and change their shape when switching. Placing them on a surface while maintaining their function is extremely difficult, making them unsuitable as building blocks for computer logic.
The switching within the molecule used by the IBM researchers is well-defined, highly-localized, reversible, intrinsic to the molecule, and does not involve changes in the molecular frame. Therefore, this molecule could be used as a building block for more complex molecular devices that serve as logic elements. As the shape of the molecule does not change during switching, single switches can be coupled in a controlled way. The switching process should also work with molecules embedded in more complex structures.
"Accidental" Science
Although the IBM Research team had been screening various molecules to discover if they would be suitable for molecular switches, in the case of naphthalocyanine, the tests being performed were not to observe switching but rather to examine molecular vibrations, since understanding vibrations of molecules is important for devices operating at the atomic level. During those tests, team members were surprised to observe results that were intriguing for switching at the molecular scale, and they shifted their focus from studying vibrations to studying switching, leading to this breakthrough.
“One of the beauties of doing exploratory science is that by researching one area, you sometimes stumble upon other areas of major significance,” said Gerhard Meyer, senior researcher in the nanoscale science group at the IBM Zurich lab. “Although the discovery of this breakthrough was accidental, it may prove to be significant for building the computers of the future.”
IBM’s Nanotechnology Leadership
These new results are the latest in a series of achievements in nanoscale science at IBM Research. Two IBM scientists in Switzerland won the 1986 Nobel Prize in physics for their early 1980s invention of the STM. Over the past 20 years, IBM Almaden researchers have pioneered the use of STMs for positioning atoms into precisely designed structures that reveal fundamental atomic-scale properties and may have potential uses in information storage, transmission and processing.
Note: This story has been adapted from a news release issued by IBM.

Fausto Intilla

www.oloscience.com

Low-cost Recipe For Patterning Microchips Developed

Source:

http://www.sciencedaily.com/releases/2007/09/070902193635.htm

Science Daily — Creating ultrasmall grooves on microchips -- a key part of many modern technologies -- is about to become as easy as making a sandwich, using a new process invented by Princeton engineers.

The simple, low-cost technique results in the self-formation of periodic lines, or gratings, separated by as few as 60 nanometers -- less than one ten-thousandth of a millimeter -- on microchips. Features of this size have many uses in optical, biological and electronic devices, including the alignment of liquid crystals in displays.
"It's like magic," said electrical engineer Stephen Chou, the Joseph C. Elgin Professor of Engineering. "This is a fundamentally different way of making nanopatterns."
The process, called fracture-induced structuring, is as easy as one-two-three. First, a thin polymer film is painted onto a rigid plate, such as a silicon wafer. Then, a second plate is placed on top, creating a polymer sandwich that is heated to ensure adhesion. Finally, the two plates are pried apart. As the film fractures, it automatically breaks into two complementary sets of nanoscale gratings, one on each plate. The distance between the lines, called the period, is four times the film thickness.
The ease of creating these lines is in marked contrast to traditional fabrication methods, which typically use a beam of electrons, ions, or a mechanical tip to "draw" the lines into a surface. These methods are serial processes which are extremely slow and therefore only suitable for areas one square millimeter or smaller. Other techniques suitable for larger areas have difficulties achieving small grating periods or producing a high yield, or they require complex and expensive processes. Fracture-induced structuring is not only simple and fast, but it enables patterning over a much larger area. The researchers have already demonstrated the ability of the technique to create gratings over several square centimeters, and the patterning of much large areas should be possible with further optimization of the technique.
"It's remarkable -- and counterintuitive -- that fracturing creates these regular patterns," said chemical engineering professor and dean of Princeton's graduate school William Russel. Russel and his graduate student Leonard Pease III teamed with Chou and his graduate students Paru Deshpande and Ying Wang to develop the technique.
A patent application has been filed on the process, which the researchers say is economically feasible for large-scale use in industry. The gratings generated by the fracturing process also could be used in conjunction with existing patterning methods. For example, the nanoimprinting method invented by Chou in the 1990s can use the gratings generated by fracture-induced structuring to create a mold that enables mass duplication of patterns with high precision at low cost.
As with many scientific discoveries, the fracture-induced structuring process was happened upon accidentally. Graduate students in the Chou and Russel groups were trying to use instabilities in various molten polymers (in essence, melted plastic) to create patterns when they discovered instead that fracturing a solid polymer film can generate the gratings automatically. The team seized upon this finding and established the optimal conditions for grating formation.
Next, the group plans to explore the fundamental science behind the process and investigate the interplays of various forces at such a small scale, according to Chou.
"And, we want to push the limit and see how small we can go," he said.
The researchers will publish their findings Sept. 2 in the online version of Nature Nanotechnology.
Abstract :
Self-formation of sub-60-nm half-pitch gratings with large areas through fracturing.
Periodic micro- and nanostructures (gratings) have many significant applications in electronic, optical, magnetic, chemical and biological devices and materials. Traditional methods for fabricating gratings by writing with electrons, ions or a mechanical tip are limited to very small areas and suffer from extremely low throughput. Interference lithography can achieve relatively large fabrication areas, but has a low yield for small-period gratings.
Photolithography, nanoimprint lithography, soft lithography and lithographically induced self-construction all require a prefabricated mask, and although electrohydrodynamic instabilities can self-produce periodic dots without a mask, gratings remain challenging.
Here, we report a new low-cost maskless method to self-generate nano- and microgratings from an initially featureless polymer thin film sandwiched between two flat relatively rigid plates. By simply prying apart the plates, the film fractures into two complementary sets of nonsymmetrical gratings, one on each plate, of the same period. The grating period is always four times the thickness of the glassy film, regardless of its molecular weight and chemical composition. Periods from 120 nm to 200 mm have been demonstrated across areas as large as two square centimeters.
Note: This story has been adapted from a news release issued by Princeton University, Engineering School.

Fausto Intilla

www.oloscience.com