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What's New in Nanotechnology?

January 27, 2010

Conventional theory says when films are being formed at the atomic scale, atoms land on top of each other and form mounds or "islands" and feel an energetic "pull" from other atoms that prevents them from hopping off the island's edges and crystallizing into smooth sheets. The result is rough spots on the thin films used to produce semiconductors. Cornell University-led researchers eliminated this pull by shortening the bonds between their particles. But they still saw particles hesitate at the island's edges.Image Credit: Rajesh Ganapathy, Sharon Gerbode, Mark Buckley, and Itai Cohen - Cornell University

The quest for faster electronic devices recently got something more than a little bump up in technological knowhow. Scientists at Cornell University, Ithaca, N.Y. discovered that the thin, smooth, crystalline sheets needed to make semiconductors, which are the foundation of modern computers, might be grown into smoother sheets by managing the random darting motions of the atomic particles that affect how the crystals grow. Led by assistant professor of physics Itai Cohen at Cornell, researchers recreated conditions of layer-by-layer crystalline growth using particles much bigger than atoms, but still small enough that they behave like atoms. Similar to using beach balls to model the behavior of sand, scientists used a solution of tiny plastic spheres 50 times smaller than a human hair to reproduce the conditions that lead to crystallization on the atomic scale. With this precise modeling, they could watch how crystalline sheets grow. Using an optical microscope, the scientists could watch exactly what their "atoms"--actually, micron-sized silica particles suspended in fluid--did as they crystallized. What's more, they were able to manipulate single particles one at a time and test conditions that lead to smooth crystal growth. The video below is sped up by a factor of about 20. Video Credit: John Savage, Rajesh Ganapathy, and Itai Cohen -  Cornell University.
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Categories : University News
January 26, 2010

One result of the new research is that scientists will now be able to exploit the COMPcc portion of a polymer to wrap around a Vitamin D molecule in order to stimulate its tissue-regenerating power. Genetically engineered copolymers have applications in everything from artificial therapeutics, biocatalysts, scaffolds, and cells for medicine, to sustainable energy and environmental remediation.Credit: New York University

Researchers are finding remarkable ways in which bioengineered paired macromolecules can be made to self-assemble, disassemble, and more -- and then biodegrade when they’ve finished their work. The key to these macromolecules -- called block copolymers -- is their ability to self-assemble when exposed to discrete external stimuli. Self-assembly can occur as a function of temperature or pH, for example. And it is not necessarily a permanent change; it can be reversed. Genetically engineered copolymers have applications in everything from artificial therapeutics, biocatalysts, scaffolds, and cells for medicine, to sustainable energy and environmental remediation. For four years, Jin Kim Montclare and researchers at the Polytechnic Institute of New York University have been developing block copolymers from scratch using recombinant DNA and putting them through biochemical hoops. The group’s work, published recently in the journal ChemBioChem, involves block copolymers comprising elastin alternating with COMPcc. The former is a pentapeptide whose amino-acid constituents can assemble into a beta spiral structure as a function of temperature, pH, or salinity. COMPcc, which stands for “cartilage oligomeric matrix protein coil coiled,” is a pentamer arranged as five helixes that can contort into an arrangement that produces a hydrophobic core the way one might create a cylindrical cavity by stacking garden hoses on a deck -- thus the odd “coiled coil” nomenclature. COMPcc has the ability to bind small water-insoluble molecules such as Vitamin D within its hydrophobic core. The possibilities are manifold. “That central pore can potentially bind chemicals that are hard to deliver as drugs because they are normally not water soluble,” says Montclare. For example COMPcc can bind to Vitamin D, a non-dissolving molecule that happens to have profound implications for regenerative tissue and serves as a signaling hormone for the promotion of tissue differentiation into cartilage and bone. And COMPcc can “live” in a copolymer with elastin, synthetics, or other coiled coil-based materials that self-assemble into gels or more organized forms like scaffolding, which can be used for tissue regeneration.
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Categories : University News
January 15, 2010

Image Credit: Rice University

The latest work in a series of molecular machines that began with 2005's nanocar has produced what Rice University scientists James Tour and Kevin Kelly call a nanodragster for its characteristic hot-rod shape, with small wheels on a short axle in the front and large wheels on a long axle in the back. Their research is another step toward functional nanomachines that can be custom-built and set to work in microelectronics and other applications. What those wheels are made of matters most. Early nanocars rolled on simple carbon 60 molecules, aka buckyballs. But they were a drag, literally, as they would only turn on a gold surface in high heat, about 200 degrees Celsius. The Rice team found in previous research that wheels made of p-carborane, a cluster of carbon and boron atoms, operate at much lower temperatures. But they're more difficult to image with a scanning tunneling microscope because of their much weaker interaction with metallic surfaces. The key to making nanodragsters was putting p-carborane wheels in the front and buckyballs in the back, getting the advantages of both. The front wheels roll easier, while the buckyballs grip the gold roadway well enough to be imaged. And the vehicle operates at a much lower temperature than previous nanovehicles.
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Categories : University News
January 08, 2010

Image Credit: MIT

Researchers at MIT and Harvard Medical School have built targeted nanoparticles that can cling to artery walls and slowly release medicine, an advance that potentially provides an alternative to drug-releasing stents in some patients with cardiovascular disease. The particles, dubbed “nanoburrs” because they are coated with tiny protein fragments that allow them to stick to target proteins, can be designed to release their drug payload over several days. The nanoburrs are targeted to a specific structure, known as the basement membrane, which lines the arterial walls and is only exposed when those walls are damaged. Therefore, the nanoburrs could be used to deliver drugs to treat atherosclerosis and other inflammatory cardiovascular diseases. They are one of the first such targeted particles that can precisely home in on damaged vascular tissue, says Omid Farokhzad, associate professor at Harvard Medical School. Farokhzad and MIT Institute Professor Robert Langer have previously developed nanoparticles that seek out and destroy tumorsThe researchers hope the particles could become a complementary approach that can be used with vascular stents, which are the standard of care for most cases of clogged and damaged arteries, or in lieu of stents in areas not well suited to them, such as near a fork in the artery.

Categories : University News
December 07, 2009

Stanford University scientists are harnessing nanotechnology to quickly produce ultra-lightweight, bendable batteries and supercapacitors in the form of everyday paper. Simply coating a sheet of paper with ink made of carbon nanotubes and silver nanowires makes a highly conductive storage device, said Yi Cui, assistant professor of materials science and engineering. "Society really needs a low-cost, high-performance energy storage device, such as batteries and simple supercapacitors," he said. Like batteries, capacitors hold an electric charge, but for a shorter period of time. However, capacitors can store and discharge electricity much more rapidly than a battery.
httpvh://www.youtube.com/watch?v=QPTcQJPbGHw
Above: Post doctoral students in the lab of Prof. Yi Cui, Materials Science and Engineering, light up a diode from a battery made from treated paper, similar to what you would find in a copy machine. The paper batteries are treated with a nanotube ink, baked and folded into electrical generating sources like the one wrapped in foil seen here. (Video Credit: Stanford University)

"These nanomaterials are special," Cui said. "They're a one-dimensional structure with very small diameters." The small diameter helps the nanomaterial ink stick strongly to the fibrous paper, making the battery and supercapacitor very durable. The paper supercapacitor may last through 40,000 charge-discharge cycles – at least an order of magnitude more than lithium batteries. The nanomaterials also make ideal conductors because they move electricity along much more efficiently than ordinary conductors, Cui said. Cui had previously created nanomaterial energy storage devices using plastics. His new research shows that a paper battery is more durable because the ink adheres more strongly to paper (answering the question, "Paper or plastic?").
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Categories : University News
December 03, 2009

This illustration shows the tip of a scanning tunneling microscope approaching an undulating sheet of perfect graphene. The exotic substance is 10 times stronger than steel and conducts electricity better than any known material at room temperature. Both physicists and nanoscientists are studying graphene and exploring its potential applications. (Image Source: Vanderbilt Univeristy; Image Credit: Calvin Davidson, British Carbon Group)

First, it was the soccer-ball-shaped molecules dubbed buckyballs. Then it was the cylindrically shaped nanotubes. Now there is graphene: a remarkably flat molecule made of carbon atoms arranged in hexagonal rings much like molecular chicken wire.  It is 10 times stronger than steel and conducts electricity better than any other known material at room temperature. These and graphene’s other exotic properties have attracted the interest of physicists, who want to study them, and nanotechnologists, who want to exploit them to make novel electrical and mechanical devices. Although graphene is the first truly two-dimensional crystalline material that has been discovered, over the years scientists have put considerable thought into how two-dimensional gases and solids should behave. They have also succeeded in creating a close approximation to a two-dimensional electron gas by bonding two slightly different semiconductors together. Electrons are confined to the interface between the two and their motions are restrained to two dimensions. When such a system is cooled down to less than one degree above absolute zero and a strong magnetic field is applied, then the fractional quantum Hall effect appears. Since scientists figured out how to make graphene five years ago, they have been trying to get it to exhibit this effect with only marginal success. The best way to understand it is to think of the electrons in graphene as a forming a (very thin) sea of charge. When the magnetic field is applied, it generates whirlpools in the electron fluid. Because electrons carry a negative charge, these vortices have a positive charge.
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Categories : University News
November 26, 2009

As depicted in this illustration, tiny particles of a gold-aluminum alloy were alternately heated and cooled inside a vacuum chamber, and then silicon and germanium gases were alternately introduced. As the gold-aluminum bead absorbed the gases, it became "supersaturated" with silicon and germanium, causing them to precipitate and form wires. (Image Source: Purdue University, Birck Nanotechnology Center/Seyet LLC)

A new generation of ultrasmall transistors and more powerful computer chips using tiny structures called semiconducting nanowires is closer to reality after a key discovery by researchers at IBM, Purdue University and the University of California at Los Angeles.  The researchers have learned how to create nanowires with layers of different materials that are sharply defined at the atomic level, which is a critical requirement for making efficient transistors out of the structures. "Having sharply defined layers of materials enables you to improve and control the flow of electrons and to switch this flow on and off," said Eric Stach, an associate professor of materials engineering at Purdue. Electronic devices are often made of "heterostructures," meaning they contain sharply defined layers of different semiconducting materials, such as silicon and germanium. Until now, however, researchers have been unable to produce nanowires with sharply defined silicon and germanium layers. Instead, this transition from one layer to the next has been too gradual for the devices to perform optimally as transistors. The new findings point to a method for creating nanowire transistors. Whereas conventional transistors are made on flat, horizontal pieces of silicon, the silicon nanowires are "grown" vertically. Because of this vertical structure, they have a smaller footprint, which could make it possible to fit more transistors on an integrated circuit, or chip, Stach said. New technologies will be needed for industry to maintain Moore's law, an unofficial rule stating that the number of transistors on a computer chip doubles about every 18 months, resulting in rapid progress in computers and telecommunications. Doubling the number of devices that can fit on a computer chip translates into a similar increase in performance. However, it is becoming increasingly difficult to continue shrinking electronic devices made of conventional silicon-based semiconductors . 
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Categories : University News
November 25, 2009

Scanning electron micrograph of two thin, flat rings of silicon nitride, each 190 nanometers thick and mounted a millionth of a meter apart. Under the right conditions optical forces between the two rings are enough to bend the thin spokes and pull the rings toward one another, changing their resonances enough to act as an optical switch. Image Credit: Cornell Nanophotonics Group

With a bit of leverage, researchers have used a very tiny beam of light with as little as 1 milliwatt of power to move a silicon structure up to 12 nanometers. That’s enough to completely switch the optical properties of the structure from opaque to transparent, they report.

The technology could have applications in the design of nanoscale devices with moving parts—known as micro-electromechanical systems (MEMS)—and micro-optomechanical systems (MOMS), which combine moving parts with photonic circuits, says Michal Lipson, associate professor of electrical and computer engineering at Cornell University. Light can be thought of as a stream of particles that can exert a force on whatever they strike. The sun doesn’t knock you off your feet because the force is very small, but at the nanoscale it can be significant. “The challenge is that large optical forces are required to change the geometry of photonic structures,” Lipson explained.
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Categories : University News
November 09, 2009

Mouse tumor cells stain red, showing penetration of anti-cancer drug after 24 hours. Image Credit: Pratt School of Engineering, Duke University

Going smaller could bring better results, especially when it comes to cancer-fighting drugs. Duke University bioengineers have developed a simple and inexpensive method for loading cancer drug payloads into nano-scale delivery vehicles and demonstrated in animal models that this new nanoformulation can eliminate tumors after a single treatment. After delivering the drug to the tumor, the delivery vehicle breaks down into harmless byproducts, markedly decreasing the toxicity for the recipient. Nano-delivery systems have become increasingly attractive to researchers because of their ability to efficiently get into tumors. Since blood vessels supplying tumors are more porous, or leaky, than normal vessels, the nanoformulation can more easily enter and accumulate within tumor cells. This means that higher doses of the drug can be delivered, increasing its cancer-killing abilities while decreasing the side effects associated with systematic chemotherapy.
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Categories : University News
October 29, 2009

For the first time, researchers can use infrared spectroscopy to determine what type of bonds protein molecules contain and to identify materials. The new technique has been sought to overcome several limitations of the current, standard technique.Image Credit: Hatice Altug, Electrical Engineering Department, Boston University

An interdisciplinary team of researchers has created a new, ultra-sensitive technique to analyze life-sustaining protein molecules. The technique may profoundly change the methodology of biomolecular studies and chart a new path to effective diagnostics and early treatment of complex diseases. Researchers from Boston University and Tufts University near Boston recently demonstrated an infrared spectroscopy technique that can directly identify the "vibrational fingerprints" of extremely small quantities of proteins, the machinery involved in maintaining living organisms. The new technique exploits nanotechnology to overcome several limitations of current, conventional techniques used to study biomolecules. Previous bio-molecular study methods commonly use fluorescence spectroscopy, where biomolecules are labeled with very bright fluorescence tags to track how efficiently they interact with each other. Understanding interactions is important for medical drug research. Molecules consist of atoms bonded to each other with springs. Depending on the mass of atoms, how stiff these springs are, or how the atoms' springs are arranged, the molecules rotate and vibrate at specific frequencies similar to a guitar string that vibrates at specific frequencies depending on the string length. These resonant frequencies are molecule specific and they mostly occur in the infrared frequency range of the electromagnetic spectrum. The sensitivity of infrared spectroscopy previously had been too low to detect these vibrations, particularly from small quantities of samples.
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