A centre for research on graphene, a material which has the potential to revolutionise numerous industries, ranging from healthcare to electronics, is to be created at the University of Cambridge. The University has been a hub for graphene engineering from the very start and now aims to make this “wonder material” work in real-life applications. The Cambridge Graphene Centre will start its activities on February 1st 2013, with a dedicated facility due to open at the end of the year. Its objective is to take graphene to the next level, bridging the gap between academia and industry. It will also be a shared research facility with state-of-the-art equipment, which any scientist researching graphene will have the opportunity to use. The Centre’s activities will be funded by a Government grant worth more than £12 million, which was allocated to the University in December by the Engineering and Physical Sciences Research Council (EPSRC). The rest of this money will support projects focusing both on how to manufacture high-quality graphene on an industrial scale, and on developing some of its potential applications.
What's New in Nanotechnology?
A close-up of spherical silicon nanoparticles about 10 nanometers in diameter. University at Buffalo scientists report that these particles could form the basis of new technologies that generate hydrogen for portable power applications. (Image Credit: Swihart Research Group, University at Buffalo)
Super-small particles of silicon react with water to produce hydrogen almost instantaneously, according to University at Buffalo researchers. In a series of experiments, the scientists created spherical silicon particles about 10 nanometers in diameter. When combined with water, these particles reacted to form silicic acid (a nontoxic byproduct) and hydrogen — a potential source of energy for fuel cells. The reaction didn’t require any light, heat or electricity, and also created hydrogen about 150 times faster than similar reactions using silicon particles 100 nanometers wide, and 1,000 times faster than bulk silicon, according to the study. The scientists were able to verify that the hydrogen they made was relatively pure by testing it successfully in a small fuel cell that powered a fan. “When it comes to splitting water to produce hydrogen, nanosized silicon may be better than more obvious choices that people have studied for a while, such as aluminum,” said researcher Mark T. Swihart, UB professor of chemical and biological engineering and director of the university’s Strategic Strength in Integrated Nanostructured Systems.
Scientists at Aalto University (Finland) have demonstrated results that show a huge improvement in the light absorption and the surface passivation of silicon nanostructures. This has been achieved by applying atomic layer coating. The results advance the development of devices that require high sensitivity light response such as high efficiency solar cells. The method provides extremely good surface passivation and simultaneously reduces the reflectance further at all wavelengths. These results are very promising considering the use of black silicon (b-Si) surfaces on solar cells to increase the efficiency to completely new levels, according to researcher scientist, Päivikki Repo. Black silicon (b-Si) can also be used in technologies other than solar cells. Numerous applications suggested for b-Si include drug analysis. Black silicon has been a subject of great interest in various fields including photovoltaics for its ability to reduce the surface reflectance even below 1 per cent. However, many b-Si applications - especially solar cells - suffer from increased surface recombination resulting in poor spectral response. This is particularly problematic at short wavelengths.
A recent NIST patent shows that nanopores, which may one day help doctors perform quick analysis of blood samples, are not harmed by the polymerization process that could help nanopores operate in biochips. Polymerization hardens and stabilizes the membrane surrounding the nanopores, both of which are beneficial effects. Image Credit: Robertson/NIST
Having blood drawn and analyzed to diagnose disease is a process that can take a few days, but what if your doctor could perform this analysis in moments, right before your eyes? That’s the promise of “lab on a chip” technology, and researchers are working on a variety of fronts to remove technical roadblocks. A new idea recently patented by the National Institute of Standards and Technology (NIST) and the Naval Research Laboratory (NRL) addresses the issue of sensor shelf life, showing how some such chips might be made to last for months or more until needed. NIST’s John Kasianowicz has spent decades trying to create technologies that will enable doctors to perform fast, real-time chemical analysis, and one promising approach involves building arrays of tiny pores, each small enough that only one protein or DNA molecule at a time can pass through and be identified. As our bodies respond to infection or other disease states, our cells release different proteins, and measuring the concentrations of these chemicals in a blood sample can provide a quick snapshot of our health. A membrane peppered with large numbers of these “nanopores” might give doctors a way to take that snapshot easily, if it could be mounted on a biochip compatible with electronics and computer technologies. The teams explored the possibility of turning the lipids into polymers, the sorts of molecular chains used in plastics. Polymerizing the lipids made them tougher, but the question was whether doing so would somehow render the nanopores ineffective at trapping and identifying the blood serum proteins, because the process either squeezes or stretches the tiny membrane holes dramatically. Tests at NIST showed the nanopores performed just as well as before, meaning polymerized membranes could work on a biochip.
These images of a mouse's blood vessels show the difference in resolution between traditional near-infrared fluorescence imaging (top) and Stanford's new NIR-II technique (bottom). (Image Credit: Stanford University)
Stanford University scientists have developed a fluorescence imaging technique that allows them to view the pulsing blood vessels of living animals with unprecedented clarity. Compared with conventional imaging techniques, the increase in sharpness is akin to wiping fog off your glasses. The technique, called near infrared-II imaging, or NIR-II, involves first injecting water-soluble carbon nanotubes into the living subject's bloodstream. The researchers then shine a laser (its light is in the near-infrared range, a wavelength of about 0.8 micron) over the subject; in this case, a mouse. The light causes the specially designed nanotubes to fluoresce at a longer wavelength of 1-1.4 microns, which is then detected to determine the blood vessels' structure. That the nanotubes fluoresce at substantially longer wavelengths than conventional imaging techniques is critical in achieving the stunningly clear images of the tiny blood vessels: longer wavelength light scatters less, and thus creates sharper images of the vessels. Another benefit of detecting such long wavelength light is that the detector registers less background noise since the body does not does not produce autofluorescence in this wavelength range. In addition to providing fine details, the technique – developed by Stanford scientists Hongjie Dai, professor of chemistry; John Cooke, professor of cardiovascular medicine; and Ngan Huang, acting assistant professor of cardiothoracic surgery – has a fast image acquisition rate, allowing researchers to measure blood flow in near real time. The ability to obtain both blood flow information and blood vessel clarity was not previously possible, and will be particularly useful in studying animal models of arterial disease, such as how blood flow is affected by the arterial blockages and constrictions that cause, among other things, strokes and heart attacks.
Seven-atom rings (in red) at the transition from graphene to nanotube make a new hybrid material from Rice University a seamless conductor. The hybrid may be the best electrode interface material possible for many energy storage and electronics applications. (Image Credit: Tour Group/Rice University)
A seamless graphene/nanotube hybrid created at Rice University may be the best electrode interface material possible for many energy storage and electronics applications. Led by Rice chemist James Tour, researchers have successfully grown forests of carbon nanotubes that rise quickly from sheets of graphene to astounding lengths of up to 120 microns. A house on an average plot with the same aspect ratio would rise into space. That translates into a massive amount of surface area, the key factor in making things like energy-storing supercapacitors. The Rice hybrid combines two-dimensional graphene, which is a sheet of carbon one atom thick, and nanotubes into a seamless three-dimensional structure. The bonds between them are covalent, which means adjacent carbon atoms share electrons in a highly stable configuration. The nanotubes aren’t merely sitting on the graphene sheet; they become a part of it. “Many people have tried to attach nanotubes to a metal electrode and it’s never gone very well because they get a little electronic barrier right at the interface,” Tour said. “By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it’s all one seamless material. "This gives us, effectively, a very high surface area of more than 2,000 square meters per gram of material. It’s a huge number,” said Tour. Tour said proof of the material’s hybrid nature lies in the seven-membered rings at the transition from graphene to nanotube, a structure predicted by theory for such a material and now confirmed through electron microscope images with subnanometer resolution.
Scotch tape, a versatile household staple and a mainstay of holiday gift-wrapping, may have a new scientific application as a shape-changing "smart material." Researchers used a laser to form slender half-centimeter-long fingers out of the tape. When exposed to water, the four wispy fingers morph into a tiny robotic claw that captures water droplets. The innovation could be used to collect water samples for environmental testing, said Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering. The Scotch tape - made from a cellulose-acetate sheet and an adhesive - is uniquely suited for the purpose. "It can be micromachined into different shapes and works as an inexpensive smart material that interacts with its environment to perform specific functions," he said. Doctoral student Manuel Ochoa came up with the idea. While using tape to collect pollen, he noticed that it curled when exposed to humidity. The cellulose-acetate absorbs water, but the adhesive film repels water. A laser was used to machine the tape to a tenth of its original thickness, enhancing this curling action. The researchers coated the graspers with magnetic nanoparticles so that they could be collected with a magnet. "Say you were sampling for certain bacteria in water," Ziaie said. "You could drop a bunch of these and then come the next day and collect them.”
Experiments at Purdue's Birck Nanotechnology Center were conducted by Ochoa, doctoral student Girish Chitnis and Ziaie. The grippers close underwater within minutes and can sample one-tenth of a milliliter of liquid. "Although brittle when dry, the material becomes flexible when immersed in water and is restored to its original shape upon drying, a crucial requirement for an actuator material because you can use it over and over," Ziaie said. "Various microstructures can be carved out of the tape by using laser machining. This fabrication method offers the capabilities of rapid prototyping and batch processing without the need for complex clean-room processes."
Electronic circuits are typically integrated in rigid silicon wafers, but flexibility opens up a wide range of applications. In a world where electronics are becoming more pervasive, flexibility is a highly desirable trait, but finding materials with the right mix of performance and manufacturing cost remains a challenge. Now a team of researchers from the University of Pennsylvaniahas shown that nanoscale particles, or nanocrystals, of the semiconductor cadmium selenide can be "printed" or "coated" on flexible plastics to form high-performance electronics. Besides speed, another advantage cadmium selenide nanocrystals have over amorphous silicon is the temperature at which they are deposited. Whereas amorphous silicon uses a process that operates at several hundred degrees, cadmium selenide nanocrystals can be deposited at room temperature and annealed at mild temperatures, opening up the possibility of using more flexible plastic foundations.
Another innovation that allowed the researchers to use flexible plastic was their choice of ligands, the chemical chains that extend from the nanocrystals’ surfaces and helps facilitate conductivity as they are packed together into a film. Because the nanocrystals are dispersed in an ink-like liquid, multiple types of deposition techniques can be used to make circuits. In their study, the researchers used spincoating, where centrifugal force pulls a thin layer of the solution over a surface, but the nanocrystals could be applied through dipping, spraying or ink-jet printing as well. On a flexible plastic sheet a bottom layer of electrodes was patterned using a shadow mask — essentially a stencil — to mark off one level of the circuit. The researchers then used the stencil to define small regions of conducting gold to make the electrical connections to upper levels that would form the circuit. An insulating aluminum oxide layer was introduced and a 30-nanometer layer of nanocrystals was coated from solution. Finally, electrodes on the top level were deposited through shadow masks to ultimately form the circuits.
The IEEE International Nanoelectronics Conference, IEEE INEC 2013 will be held in Singapore, on 2-4 January 2013. The theme of the conference will be "Sustainable Nanoelectronics," focusing on nanoelectronics for the future. This conference also aims to identify the paths between fundamental research and potential electronics, photonics and nano-science applications. This conference has become an important symposium on nanoelectronics linking academics and engineers in industry.
UT Dallas researchers have made artificial muscles from carbon nanotube yarns that have been infiltrated with paraffin wax and twisted until coils form along their length. The diameter of this coiled yarn is about twice the width of a human hair. (Source UT Dallas)
New artificial muscles made from nanotech yarns and infused with paraffin wax can lift more than 100,000 times their own weight and generate 85 times more mechanical power than the same size natural muscle, according to scientists at The University of Texas at Dallas and their international team from Australia, China, South Korea, Canada and Brazil. The artificial muscles are yarns constructed from carbon nanotubes, which are seamless, hollow cylinders made from the same type of graphite layers found in the core of ordinary pencils. Individual nanotubes can be 10,000 times smaller than the diameter of a human hair, yet pound-for-pound, can be 100 times stronger than steel.The new artificial muscles are made by infiltrating a volume-changing “guest,” such as the paraffin wax used for candles, into twisted yarn made of carbon nanotubes. Heating the wax-filled yarn, either electrically or using a flash of light, causes the wax to expand, the yarn volume to increase, and the yarn length to contract. The combination of yarn volume increase with yarn length decrease results from the helical structure produced by twisting the yarn. A child’s finger cuff toy, which is designed to trap a person’s fingers in both ends of a helically woven cylinder, has an analogous action. To escape, one must push the fingers together, which contracts the tube’s length and expands its volume and diameter. In the video below, Dr. Ray Baughman of UT Dallas’s NanoTech Institute explains carbon nanotube yarns.