What's New in Nanotechnology? (Archive)   Email | Print

Better Brain Implants Using Conducting Polymer Nanotubes

This illustration depicts neurons firing (green structures in the foreground) and communicating with nanotubes in the background. Illustration courtesy of Mohammad Reza Abidian

Brain implants that can more clearly record signals from surrounding neurons in rats have been created at the University of Michigan. The findings could eventually lead to more effective treatment of neurological disorders such as Parkinson's disease and paralysis. Neural electrodes must work for time periods ranging from hours to years. When the electrodes are implanted, the brain first reacts to the acute injury with an inflammatory response. Then the brain settles into a wound-healing, or chronic, response. It's during this secondary response that brain tissue starts to encapsulate the electrode, cutting it off from communication with surrounding neurons. The new brain implants developed at U-M are coated with nanotubes made of poly(3,4-ethylenedioxythiophene) (PEDOT), a biocompatible and electrically conductive polymer that has been shown to record neural signals better than conventional metal electrodes. U-M researchers found that PEDOT nanotubes enhanced high-quality unit activity (signal-to-noise ratio >4) about 30 percent more than the uncoated sites. They also found that based on in vivo impedance data, PEDOT nanotubes might be used as a novel method for biosensing to indicate the transition between acute and chronic responses in brain tissue.
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IBM Scientists First to Image the 'Anatomy' of a Molecule

Imaging the "anatomy" of a pentacene molecule - 3D rendered view: By using a sharp metal tip terminated with a carbon monoxide molecule, scientists measured in the short-range regime of forces to obtain an image of the inner structure of the molecule. The colored surface represents experimental data. Image courtesy of IBM Research – Zurich

IBM scientists have been able to image the "anatomy" -- or chemical structure -- inside a molecule with unprecedented resolution, using a complex technique known as noncontact atomic force microscopy. The results push the exploration of using molecules and atoms at the smallest scale and could greatly impact the field of nanotechnology, which seeks to understand and control some of the smallest objects known to mankind. "Though not an exact comparison, if you think about how a doctor uses an x-ray to image bones and organs inside the human body, we are using the atomic force microscope to image the atomic structures that are the backbones of individual molecules," said IBM Researcher Gerhard Meyer. "Scanning probe techniques offer amazing potential for prototyping complex functional structures and for tailoring and studying their electronic and chemical properties on the atomic scale."
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Looking deeply into polymer solar cells

3D Electron tomography image of a polymer-metal oxide solar cell. The 3D nanoscopic morphology shows the interpenetrating metal oxide network in (yellow) inside a polymer matrix (black). Image Source: Eindhoven University of Technology

Researchers from the Eindhoven University of Technology (TU/e) have made the first high-resolution 3D images of the inside of a polymer solar cell. This gives them important new insights in the nanoscale structure of a polymer solar cell and the effect on its performance. The research was a joint effort of TU/e-researchers and colleagues at the University of Ulm, Germany. The investigations shed new light on the operational principles of polymer solar cells. This is expected to be very important for the development of better polymer solar cells. Polymer solar cells do not have the high efficiencies of their silicon counterparts yet. Polymer cells, however, can be printed in roll-to-roll processes, at very high speeds, which makes the technology potentially very cost-effective. Added to that, polymer cells are flexible and lightweight, and therefore suitable to be used on vehicles or clothing or to be incorporated in the design of objects. In these hybrid solar cells, a mixture of two different materials, a polymer and a metal oxide are used to create charges at their interface when the mixture is illuminated by the sun.
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IBM Scientists Use DNA Scaffolding To Build Tiny Circuit Boards

IBM scientists are using DNA origami to build tiny circuit boards; in this image, low concentrations of triangular DNA origami are binding to wide lines on a lithographically patterned surface. Credit: IBM

Scientists at IBM Research and the California Institute of Technology have announced a scientific advancement that could be a major breakthrough in enabling the semiconductor industry to pack more power and speed into tiny computer chips, while making them more energy efficient and less expensive to manufacture. They made an advancement in combining lithographic patterning with self assembly – a method to arrange DNA origami structures on surfaces compatible with today’s semiconductor manufacturing equipment. Today, the semiconductor industry is faced with the challenges of developing lithographic technology for feature sizes smaller than 22 nm and exploring new classes of transistors that employ carbon nanotubes or silicon nanowires. IBM’s approach of using DNA molecules as scaffolding  -- where millions of carbon nanotubes could be deposited and self-assembled into precise patterns by sticking to the DNA molecules – may provide a way to reach sub-22 nm lithography. The utility of this approach lies in the fact that the positioned DNA nanostructures can serve as scaffolds, or miniature circuit boards, for the precise assembly of components – such as carbon nanotubes, nanowires and nanoparticles – at dimensions significantly smaller than possible with conventional semiconductor fabrication techniques. This opens up the possibility of creating functional devices that can be integrated into larger structures, as well as enabling studies of arrays of nanostructures with known coordinates.
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POSTECH Synthesizes Nanometer-thin Lens

POSTECH's research team, led by chemistry professor Kim Kwang-soo, said it has successfully synthesized lenses that are hundreds of times thinner than a single hair. The team discovered a new physics phenomenon. When the size of a lens shrinks to the level of the wavelength of light, it shows the ultra-resolution that thinner things than the half wavelength of light could be distinguished. The half-wavelength of light is theoretically limiting value of diffraction in traditional geometrical optics. Kim's team found that the organic matter Calix Hydro Quinon can shape a nanometer-thin cross-sectioned convex lens. The team found an ultra-refraction for the first time in which a light-wavelength-thin lens makes the light draw a curve through diffraction and interference and makes the nano-lens have a very short focal distance. The team proved the intriguing optical phenomenon of the nano-lens through the precise simulation of electromagnetic waves and established a new physical phenomenon theory. The optical features of a nanometer-thin lens can be used to analyze structures of nano and micro-bio substances, to improve technologies for the development of nano components, and to integrate light that is impossible to observe with traditional optical microscopes. Nanometerthin lenses can be also used for the development of next-generation nano-optical memories and detection components. The success of the research resulted from cooperation between academics in chemistry, physics, and mechanical and electronic engineering.
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Nanoparticles Explored for Preventing Cell Damage

Sudipta Seal, materials scientist and engineer at the University of Central Florida, holds a bottle containing billions of ultra-small, engineered nanoceria. Credit: Sudipta Seal, University of Central Florida

Sudipta Seal is enthralled by nanoparticles, particularly those of a rare earth metal called cerium. The particles are showing potential for a wide range of applications, from medicine to energy. Seal is a professor of materials science and engineering at the University of Central Florida (UCF), and several years ago, he and his colleagues engineered nanoparticles of cerium oxide (CeO2), a material long used in ceramics, catalysts, and fuel cells. The novel nanocrystalline form is non-toxic and biocompatible--ideal for medical applications. Since then, the researchers found that cerium oxide nanoparticles have two additional medical benefits: they behave like an antioxidant, protecting cells from oxidative stress, and they can be fine-tuned to potentially deliver medical treatments directly into cells.
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Nanosolar Looks to the Sun with Nanotechnology

Hoping to leave today's silicon solar cells behind, the Palo Alto company Nanosolar is creating paper-thin solar panels harnessing nanotechnology, a product that could revolutionize solar power. View the video below!

QUEST on KQED Public Media.

Searching for New Transistors

Semiconductor Research Corporation (SRC), a university-research consortium for semiconductors and related technologies, has teamed with the National Science Foundation (NSF) to announce funding of $2 million in new supplemental grants for nanoelectronics research. Researchers at six major NSF centers inside leading U.S. universities will contribute to the goal of finding a replacement for the transistor - the foundational building block of computing technology for decades - and discovering a new digital switching mechanism using nanoelectronics innovation. In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Until recently, manufacturers were able to double the number of transistors on a chip at half the power for each transistor by shrinking them smaller and smaller in each new generation of semiconductor technology. However, it is becoming increasingly difficult to continue decreasing the power needed to turn the device off and on, making it difficult to continue the pace of product innovation from scaling alone.
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Drexel Nanotechnology Research Paves the Way to Ever Smaller Electronic Devices

The alternating pattern of PE-b-PEO formed on SWNTs with a 12 nm period imaged using transmission electron microscopy. The dark and bright stripes represent the PEO and PE domains, respectively. Image Source: Drexel University

Professor Christopher Li in Drexel University’s Department of Materials Science and Engineering and colleagues are one step closer to making personal electronic devices even smaller.  Their research demonstrates that it is possible to manipulate a carbon nanotube, the building block of nanotechnology applications, for the future miniaturization of electronic devices, including computers, cell phones, and PDAs. Carbon nanotubes, or CNTs -- the diameter of only a few millionths of a human hair -- are favored in nanotechnology research and applications for their unusual properties.  To be able to use CNTs to create ever smaller electronic devices, a nanotube would have to be furnished with multiple transistors. To achieve this goal, one has to be able to fabricate uniform, large-scale, controllable patterns on CNTs at a few tenths of a nanometer scale, a difficult task which to date has not been successfully addressed.  Drexel researchers, led by Professor Li, have now demonstrated that it is possible to create periodic, alternating patterns on carbon nanotubes with a period of 12 nanometers by decorating carbon nanotubes with judiciously selected crystalline block copolymers (in this case polyethylene-block-poly(ethylene oxide)).  Block copolymers are comprised of two chemically different polymer chains that are covalently linked together at one end. The trick is to select two blocks of the copolymer so that one has a strong tendency to crystallize on the carbon nanotube surface and the other block can then be brought to the vicinity of the carbon nanotube. The period of the pattern can be easily controlled to be ~10-100 nanometers by simply varying the molecular weight of the block copolymers. 
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Nanotubes Boost Structural Integrity of Composites

Researchers at Rensselaer have discovered a new technique for provoking unusual crazing behavior in epoxy composites. The crazing, which causes the composite to deform into a network of nanoscale pillar-like fibers that bridge together both sides of a crack and slow its growth, could lead to tougher, more durable components for aircraft and automobiles. Image Source: Rensselaer Polytechnic Institute

A new research discovery at Rensselaer Polytechnic Institute could lead to tougher, more durable composite frames for aircraft, watercraft, and automobiles. Epoxy composites are increasingly being incorporated into the design of new jets, planes, and other vehicles. Composite material frames are extremely lightweight, which lowers the overall weight of the vehicle and boosts fuel efficiency. The downside is that epoxy composites can be brittle, which is detrimental to its structural integrity. Professor Nikhil Koratkar, of Rensselaer’s Department of Mechanical, Aerospace, and Nuclear Engineering, has demonstrated that incorporating chemically treated carbon nanotubes into an epoxy composite can significantly improve the overall toughness, fatigue resistance, and durability of a composite frame. When subjected to repetitive stress, a composite frame infused with treated nanotubes exhibited a five-fold reduction in crack growth rate as compared to a frame infused with untreated nanotubes, and a 20-fold reduction when compared to a composite frame made without nanotubes.
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Safer Nano Cancer Detector

Bright red-orange photoluminescence observed from porous silicon nanoparticles with human HeLa cells, magnified 1000x and viewed in the reflection from a silicon wafer. Prepared from high-purity silicon wafers, these nanoparticles provide a non-toxic and biodegradable alternative to conventional quantum dots for in-vitro and in-vivo fluorescence imaging. The cell nuclei are stained blue. Credit: Luo Gu, Ji-Ho Park, UCSD

The first biodegradable fluorescent nanoparticle to safely image tumors and organs in live mice could be used for cancer detection and treatment in humans. Chemistry professor Michael Sailor and a team including National Science Foundation supported researchers at the University of California, San Diego, report developing the first nanoscale "quantum dot" particle that glows brightly enough to allow physicians to examine internal organs and lasts long enough to release cancer drugs before breaking down into harmless by-products. The research is another step towards mainstreaming the use of nanotechnology in medicine. Many researchers say using nanomaterials for medical reasons is the health field's next major frontier. The payoff, they say, could be lower drug toxicity, lower treatment costs, more efficient drug use, and better patient diagnosis. "There are a lot of nanomaterials that have an ability to do fluorescence imaging," says Sailor, referring to a useful property that potentially could help doctors further see organs, diagnose patients and perform surgeries. "But they're generally toxic and not appropriate for putting into people." The problem results from toxic organic or inorganic chemicals used to make the materials glow. For example, fluorescent semiconductor nanoparticles known as quantum dots can release potentially harmful heavy metals when they break down. A paramount issue in determining the efficacy of nanomaterials is the body's ability to harmlessly get rid of residual leftovers after the nanomaterial helps diagnose or treat a disease. So Sailor's team designed a new, non-toxic quantum dot nanoparticle made from silicon wafers, the same high-purity wafers that go into the manufacture of computer chips. Reseachers took the thin wafers and ran electric current through them drilling billions of pores. They then used ultrasound waves to break the wafer into bits as small as 100 nanometers. The resulting spongy silicon particles contained nano-scale features capable of displaying quantum confinement effects, or the so-called "quantum dots." The ones in the UCSD experiment glowed a reddish color when exposed to red, blue, or ultraviolet light.
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"Fantastic Voyage" Not So Far-fetched

James Tour and coworkers at Rice University synthesized a molecular car with four carbon-based wheels that roll on axles made from linked carbon atoms. The nano-car's molecular wheels are 5,000 times smaller than a human cell. A powerful technique that allows viewing objects at the atomic level called scanning tunneling microscopy reveals the wheels roll perpendicular to the axles, rather than sliding about like a car on ice as the car moves back and forth on a surface. Credit: Y. Shirai/Rice University

A recent paper published in Scientific American, asks readers to imagine producing vehicles so small they would be about the size of a molecule and powered by engines that run on sugar. To top it off, a penny would buy a million of them. The concept is nearly unthinkable, but it's exactly the kind of thing occupying National Science Foundation supported researchers at Penn State and Rice universities. For several years, Ayusman Sen, who heads Penn State's department of chemistry, and his colleague Thomas E. Mallouk, director of the Center for Nanoscale Science at Penn State, have investigated technologies that could realize these remarkable machines whose uses might include delivering medicine to specific tissue, accomplishing surgeries or communicating with the outside world from inside the human body. Though researchers consistently have improved ways to build nano-machines, the stumbling block has been finding a way to power them. Shrinking energy producers--internal combustion engines, electric motors or jet engines--below millimeter dimensions is not an easy task, but researchers may be closer to a fantastic solution. In the 1966 movie Fantastic Voyage, scientists shrink a submarine to microscopic size and inject it into the blood stream of a brilliant scientist, who has a blood clot forming in his brain. The nano-sized surgeons then set out to remove the blood clot. Today, researchers can steer nano-machines, use them to convey cargo, and guide them using electromagnetic forces or chemical interactions. All of this, they say, makes the world seen in Fantastic Voyage not so far-fetched.
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An atom-level view of the nanoscale interface between amorphous carbon and diamond. At such a small scale, the surfaces are rough, although researchers have been treating them as smooth. Image source: University of Wisconsin-Madison

Models Present a New View of Nanoscale Friction

To understand friction on a very small scale, a team of University of Wisconsin-Madison engineers had to think big. Friction is a force that affects any application where moving parts come into contact; the more surface contact there is, the stronger the force. At the nanoscale—mere billionths of a meter—friction can wreak havoc on tiny devices made from only a small number of atoms or molecules. With their high surface-to-volume ratio, nanomaterials are especially susceptible to the forces of friction. Yet, researchers have trouble describing friction at such small scales because existing theories are not consistent with how nanomaterials actually behave. Through computer simulations, the group demonstrated that friction at the atomic level behaves similarly to friction generated between large objects. Five hundred years after Leonardo da Vinci discovered the basic friction laws for large objects, the UW-Madison team has shown that similar laws apply at the nanoscale. Current nanoscale friction theories are based on the idea that nanoscale surfaces are smooth—yet in reality, the surfaces resemble a mountain range, where each peak corresponds to an atom or a molecule. The researchers discovered simple laws of nanoscale friction. They found that friction is proportional to the number of atoms that interact between two nanoscale surfaces. The researchers’ simulations showed that, at the nanoscale, materials in contact behave more like large rough objects rubbing against each other, rather than as two perfectly smooth surfaces, as was previously imagined. 
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Understanding How Nanoparticles Change Form May Help Solve Energy Needs

Credit: Cornell University

Researchers at Cornell University recently made a major breakthrough when they invented a method to test and demonstrate a long-held hypothesis that some very, very small metal particles work much better than others in various chemical processes such as converting chemical energy to electricity in fuel cells or reducing automobile pollution. Nanoscale metal particles naturally have a wide variety of shapes and sizes and chemists long suspected that some particles work much better than others when it comes to catalyzing chemical processes. Researchers at Cornell University recently confirmed the hypothesis and discovered that some nanoparticles randomly change from good particles to bad particles. The breakthrough, reported in this week's edition of the journal Nature Materials, also came with a surprise. By devising a way to watch individual molecules react with a single nanoscale particle of gold in real time, researchers confirmed that some gold particles are better at increasing the rate of a chemical reaction than others, but they also found that a good catalyst sometimes spontaneously turns bad. Understanding why these particles change and how to stabilize the "good" particles may lead to solutions for a wide range of problems such as the current global energy challenge. 
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