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What's New in Nanotechnology?

May 03, 2016
Flexible electrocaloric fabric of nanowire array can cool. (Image Credit: Qing Wang/Penn State)

Firefighters entering burning buildings, athletes competing in the broiling sun and workers in foundries may eventually be able to carry their own, lightweight cooling units with them, thanks to a nanowire array that cools, according to Penn State materials researchers. "Most electrocaloric ceramic materials contain lead," said Qing Wang, professor of materials science and engineering. "We try not to use lead. Conventional cooling systems use coolants that can be environmentally problematic as well. Our nanowire array can cool without these problems." Electrocaloric materials are nanostructured materials that show a reversible temperature change under an applied electric field. Previously available electrocaloric materials were single crystals, bulk ceramics or ceramic thin films that could cool, but are limited because they are rigid, fragile and have poor processability. Ferroelectric polymers also can cool, but the electric field needed to induce cooling is above the safety limit for humans. Wang and his team looked at creating a nanowire material that was flexible, easily manufactured and environmentally friendly and could cool with an electric field safe for human use. Such a material might one day be incorporated into firefighting gear, athletic uniforms or other wearables.

Categories : University News
April 14, 2016
Rice University researchers have discovered a simple method to make films of highly aligned carbon nanotubes. The films can be separated from their backgrounds and show potential for use in electronic and photonic applications. (Credit: Jeff Fitlow/Rice University)

A simple filtration process helped Rice University researchers create flexible, wafer-scale films of highly aligned and closely packed carbon nanotubes. Scientists at Rice, with support from Los Alamos National Laboratory, have made inch-wide films of densely packed, chirality-enriched single-walled carbon nanotubes. In the right solution of nanotubes and under the right conditions, the tubes assemble themselves by the millions into long rows that are aligned better than once thought possible, the researchers reported. The thin films offer possibilities for making flexible electronic and photonic (light-manipulating) devices, said Rice physicist Junichiro Kono, whose lab led the study. Think of a bendable computer chip, rather than a brittle silicon one, and the potential becomes clear, he said. The Rice lab is closing in, Kono said, but the films reported in the current paper are “chirality-enriched” rather than single-chirality. A carbon nanotube is a cylinder of graphene, with its atoms arranged in hexagons. How the hexagons are turned sets the tube’s chirality, and that determines its electronic properties. Some are semiconducting like silicon, and others are metallic conductors. A film of perfectly aligned, single-chirality nanotubes would have specific electronic properties. Controlling the chirality would allow for tunable films, Kono said, but nanotubes grow in batches of random types.

March 17, 2016
A common over-the-counter drug, chopped down into nanoparticle size, stopped growth in a cancer tumor. Image Credit: Washington University in St. Louis

Engineers at Washington University in St. Louis found a way to keep a cancerous tumor from growing by using nanoparticles of the main ingredient in common antacid tablets. The research team, led by Avik Som, an MD/PhD student, and Samuel Achilefu, PhD, professor of radiology and of biochemistry & molecular biophysics in the School of Medicine and of biomedical engineering in the School of Engineering & Applied Science, in collaboration with two labs in the School of Engineering & Applied Science, used two novel methods to create nanoparticles from calcium carbonate that were injected intravenously into a mouse model to treat solid tumors. The compound changed the pH of the tumor environment, from acidic to more alkaline, and kept the cancer from growing. With this work, researchers showed for the first time that they can modulate pH in solid tumors using intentionally designed nanoparticles. “Cancer kills because of metastasis,” said Som, who is working on a doctorate in biomedical engineering in addition to a medical degree. “The pH of a tumor has been heavily correlated with metastasis. For a cancer cell to get out of the extracellular matrix, or the cells around it, one of the methods it uses is a decreased pH.”

Categories : University News
March 10, 2016
Image Credit: McGill University, Thomas Edwardson

Gold nanoparticles have unusual optical, electronic and chemical properties, which scientists are seeking to put to use in a range of new technologies, from nanoelectronics to cancer treatments. Some of the most interesting properties of nanoparticles emerge when they are brought close together – either in clusters of just a few particles or in crystals made up of millions of them.  Yet particles that are just millionths of an inch in size are too small to be manipulated by conventional lab tools, so a major challenge has been finding ways to assemble these bits of gold while controlling the three-dimensional shape of their arrangement. One approach that researchers have developed has been to use tiny structures made from synthetic strands of DNA to help organize nanoparticles. Researchers from McGill University’s Department of Chemistry are working on a procedure for making a DNA structure with a specific pattern of strands coming out of it; at the end of each strand is a chemical “sticky patch.”  When a gold nanoparticle is brought into contact to the DNA nanostructure, it sticks to the patches. The scientists then dissolve the assembly in distilled water, separating the DNA nanostructure into its component strands and leaving behind the DNA imprint on the gold nanoparticle. 

Categories : University News
March 02, 2016
An illustration shows a nanocar design by scientists at Rice University. The first nanocars, invented at Rice, consisted of a chassis, two axles and four wheels, all part of a single molecule. (Credit: Tour Group/Rice University)

Rice University will send an entry to the first international NanoCar Race, which will be held next October at Pico-Lab CEMES-CNRS in Toulouse, France. No one will see this miniature grand prix, at least not directly. But cars from five teams, including a collaborative effort by the Rice lab of chemist James Tour and scientists at the University of Graz, Austria, will be viewable through sophisticated microscopes developed for the event. Time trials will determine which nanocar is the fastest, though there may be head-to-head races with up to four cars on the track at once, according to organizers. A nanocar is a single-molecule vehicle of 100 or so atoms that incorporates a chassis, axles and freely rotating wheels. Each of the entries will be propelled across a custom-built gold surface by an electric current supplied by the tip of a scanning electron microscope. The track will be cold at 5 kelvins (minus 450 degrees Fahrenheit) and in a vacuum. Rice’s entry will be a new model and the latest in a line that began when Tour and his team built the world’s first nanocar more than 10 years ago. The race was first proposed in a 2013 ACS Nano paper by Christian Joachim, a senior researcher at CNRS, and Gwénaël Rapenne, a professor at Paul Sabatier University. Joining Rice are teams from Ohio University; Dresden University of Technology; the National Institute for Materials Science, Tsukuba, Japan; and Paul Sabatier. 

February 26, 2016

Common coaxial cables could be made 50 percent lighter with a new nanotube-based outer conductor developed by Rice University scientists. The Rice lab of Professor Matteo Pasquali has developed a coating that could replace the tin-coated copper braid that transmits the signal and shields the cable from electromagnetic interference. The metal braid is the heaviest component in modern coaxial data cables. Replacing the outer conductor with Rice’s flexible, high-performance coating would benefit airplanes and spacecraft, in which the weight and strength of data-carrying cables are significant factors in performance.Rice research scientist Francesca Mirri made three versions of the new cable by varying the carbon-nanotube thickness of the coating. She found that the thickest, about 90 microns – approximately the width of the average human hair – met military-grade standards for shielding and was also the most robust; it handled 10,000 bending cycles with no detrimental effect on the cable performance. “Current coaxial cables have to use a thick metal braid to meet the mechanical requirements and appropriate conductance,” Mirri said. “Our cable meets military standards, but we’re able to supply the strength and flexibility without the bulk.”

Categories : University News
January 26, 2016
Stanford and IBM researchers inserted chain-like molecules of polystyrene—the same material in a styrofoam coffee cup—between layers of nanocomposites to make these materials tougher and more flexible. (Image Credit: Dauskardt Lab, Stanford University)b, Stanford University)

Stanford and IBM researchers inserted chain-like molecules of polystyrene—the same material in a styrofoam coffee cup—between layers of nanocomposites to make these materials tougher and more flexible.(Image Credit: Dauskardt Lab, Stanford University)

By slipping springy polystyrene molecules between layers of tough yet brittle composites, researchers made materials stronger and more flexible, in the process demonstrating the theoretical limits of how far this toughening technique could go. Researchers at Stanford and IBM have tested the upper boundaries of mechanical toughness in a class of lightweight nanocomposites toughened by individual molecules, and offered a new model for how they get their toughness. The potential applications for nanocomposites cut across many industries, from computer circuitry to transportation to athletics. They could even revolutionize spaceflight with their ability to withstand tension and extreme temperatures. The study was led by Reinhold Dauskardt, a professor of materials science and engineering at Stanford University, and Geraud Dubois, of IBM's Almaden Research Center. The study was sponsored by the Air Force Office of Scientific Research.

January 19, 2016

With the world population expected to reach 9 billion by 2050, engineers and scientists are looking for ways to meet the increasing demand for food without also increasing the strain on natural resources, such as water and energy — an initiative known as the food-water-energy nexus. Ramesh Raliya, PhD, a postdoctoral researcher, and Pratim Biswas, PhD, the Lucy & Stanley Lopata Professor and chair of the Department of Energy, Environmental & Chemical Engineering, both at the School of Engineering & Applied Science at Washington University in St. Louis, are addressing this issue by using nanoparticles to boost the nutrient content and growth of tomato plants. Taking a clue from their work with solar cells, the team found that by using zinc oxide and titanium dioxide nanoparticles, the tomato plants better absorbed light and minerals, and the fruit had higher antioxidant content. Zinc is an essential nutrient for plants, helps other enzymes function properly and is an ingredient in conventional fertilizer. Titanium is not an essential nutrient for plants, Raliya said, but boosts light absorption by increasing chlorophyll content in the leaves and promotes photosynthesis, properties Biswas’ lab discovered while creating solar cells. “When a plant grows, it signals the soil that it needs nutrients,” Biswas said. “The nutrient it needs is not in a form that the plant can take right away, so it secretes enzymes, which react with the soil and trigger bacterial microbes to turn the nutrients into a form that the plant can use. We’re trying to aid this pathway by adding nanoparticles.”

Categories : University News
January 12, 2016
 An artist’s rendering shows the layers of a new, onion-like nanoparticle whose specially crafted layers enable it to efficiently convert invisible near-infrared light to higher energy blue and UV light. Credit: Kaiheng Wei - University at Buffalo

A new, onion-like nanoparticle could open new frontiers in biomaging, solar energy harvesting and light-based security techniques. The research was led by the Institute for Lasers, Photonics, and Biophotonics at the State University of New York University at Buffalo and the Harbin Institute of Technology in China, with contributions from the Royal Institute of Technology in Sweden, Tomsk State University in Russia, and the University of Massachusetts Medical School.  The particle’s innovation lies in its layers: a coating of organic dye, a neodymium-containing shell, and a core that incorporates ytterbium and thulium. Together, these strata convert invisible near-infrared light to higher energy blue and UV light with record-high efficiency, a trick that could improve the performance of technologies ranging from deep-tissue imaging and light-induced therapy to security inks used for printing money. When it comes to bioimaging, near-infrared light could be used to activate the light-emitting nanoparticles deep inside the body, providing high-contrast images of areas of interest. In the realm of security, nanoparticle-infused inks could be incorporated into currency designs; such ink would be invisible to the naked eye, but glow blue when hit by a low-energy laser pulse — a trait very difficult for counterfeiters to reproduce.

Categories : University News
January 05, 2016
 Schematic showing a new engineered surface that can repel liquids in any state of wetness.<br />Image: Xianming Dai, Chujun Zeng and Tak-Sing Wong/Penn State

The leaves of the lotus flower, and other natural surfaces that repel water and dirt, have been the model for many types of engineered liquid-repelling surfaces. As slippery as these surfaces are, however, tiny water droplets still stick to them. Now, Penn State researchers have developed nano/micro-textured, highly slippery surfaces able to outperform these naturally inspired coatings, particularly when the water is a vapor or tiny droplets. Enhancing the mobility of liquid droplets on rough surfaces could improve condensation heat transfer for power-plant heat exchangers, create more efficient water harvesting in arid regions, and prevent icing and frosting on aircraft wings. "This represents a fundamentally new concept in engineered surfaces," said Tak-Sing Wong, assistant professor of mechanical engineering and a faculty member in the Penn State Materials Research Institute. "Mobility of liquid droplets on rough surfaces is highly dependent on how the liquid wets the surface. We have demonstrated for the first time experimentally that liquid droplets can be highly mobile when in the Wenzel state." Liquid droplets on rough surfaces come in one of two states: Cassie, in which the liquid partially floats on a layer of air or gas, and Wenzel, in which the droplets are in full contact with the surface, trapping or pinning them. "Through careful, systematic analysis, we found that the Wenzel equation does not apply for highly wetting liquids," said Birgitt Boschitsch Stogin, graduate student in Wong's group. In order to make Wenzel state droplets mobile, the researchers etched micrometer scale pillars into a silicon surface using photolithography and deep reactive-ion etching, and then created nanoscale textures on the pillars by wet etching. They then infused the nanotextures with a layer of lubricant that completely coated the nanostructures, resulting in greatly reduced pinning of the droplets. The nanostructures also greatly enhanced lubricant retention compared to the microstructured surface alone. The same design principle can be easily extended to other materials beyond silicon, such as metals, glass, ceramics and plastics. The authors believe this work will open the search for a new, unified model of wetting physics that explains wetting phenomena on rough surfaces.

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