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Carbon nanotubes (CNTs) being highly electrically conductive along the tube axis, have gained great research interests in recent years for connecting two conducting electrodes at the nanoscale - where the CNTs can be integrated into a micro- or nanoelectronic system. Therefore, the orientational control of CNTs has drawn a great deal of research interest in nanotechnology. Researchers now have developed a technique to bridge two electrical conductors by assembling CNTs guided by liquid crystals.
Date: Fri, 10/14/2016Paul Weiss, Editor-in-Chief of ACS Nano, discusses the exciting potential impacts of nanotechnology at the intersection of other fields. This video was produced by the American Chemical Society. Education center: 0Education center weight: 0Research centers & networks: 0Research centers & networks weight: 0Connect with Nano.gov: 0Connect with Nano.gov weight: 0Stay connected with the NNI: 0News: Nano TV/RadioStay connected with the NNI weight: 0Nanotechnology facts: 0Nanotechnology facts weight: 0Catch all weight: 0Featured: 0Dr. Weiss discusses nanotechnology's impact on other fields. This video was produced by the American Chemical Society.
Date: Fri, 10/14/2016Chad Mirkin, Director of the International Institute for Nanotechnology, discusses his research and some promising areas of nanotechnology. This video was produced by the American Chemical Society. Education center: OffEducation center weight: 0Research centers & networks: OffResearch centers & networks weight: 0Connect with Nano.gov: OffConnect with Nano.gov weight: 0Stay connected with the NNI: OffNews: Nano TV/RadioStay connected with the NNI weight: 0Nanotechnology facts: OffNanotechnology facts weight: 0Catch all weight: 0Featured: offDr. Mirkin discusses some promising areas of nanotechnology. This video was produced by the American Chemical Society.
<?xml version="1.0" encoding="UTF-8"?> Self-made DNA scaffold could make the production of single-electron devices far more scalable Illustration: Nanoscience Center/University of Jyväskylä and BioMediTech/University of Tampere To organize nanoparticles into structures that are useful in electronics, researchers have turned to DNA scaffolds that self-assemble into patterns and attract the nanoparticles into functional arrangements. Now researchers at the Nanoscience Center (NSC) of the University of Jyväskylä and BioMediTech (BMT) of the University of Tampere, both in Finland, have used these DNA scaffolds to organize three gold nanoparticles into a single-electron transistor. DNA scaffolds have previously been used to organize gold nanoparticles into patterns. But this work represents the first time that these DNA scaffolds have been used to construct precise, controllable DNA-based assemblies that are fully electrically characterized for use in single-electron nanoelectronics. The immediate benefit: There’s no longer a need to keep these structures at cryogenic temperatures in order for them to work. The way that electron transport occurs in single-electron devices is altogether different than in conventional electronics. With single-electron devices, the electron is governed by quantum mechanics. In these devices, there is what is known as an “island” where electrons are contained and isolated by tunnel junctions that control electron tunneling. The tunnel junctions operate under the quantum mechanical phenomenon known as the Coulomb Blockade, in which electrons inside the device produce a strong repulsion preventing other electrons from circulating. The Finland-based scientists observed a clear Coulomb Blockade phenomenon with their device—all the way up to room temperature. While this is not the first time that Coulomb Blockade has been observed at temperatures that high, its demonstration in a single-electron device should prove significant for these devices. But, more importantly, the use of a self-assembling DNA scaffold could make the production of these devices far more scalable. “Such a device based on DNA self-assembly would be a vast improvement due to fully parallel fabrication easily scaled for mass-production, which is the property not possible with previous methods demonstrating Coulomb Blockade up to room temperature,” explained Jussi Toppari, a Senior Lecturer at the NSC and a member of the research team, in an e-mail interview with IEEE Spectrum. In research described in the journal Nano Letters , the researchers fabricated a single-electron transistor (SET) that can visualize the effect of single electrons leaving or arriving to the islands of the device via tunneling. “The device was electrically characterized and proven to work at a basic level,” says Toppari. “However, gate dependency could not be fully demonstrated due to technical reasons. A fully working device could be utilized as a transistor or an extremely sensitive electrometer at the nanoscale.” Of course, realizing a full-fledged single-electron device is still going to require some substantial efforts. The main sticking point preventing the full utilization of this method for builing single electron nanoelectronic circuits is the difficulty associated with growing gold nanoparticles, says Toppari. “Otherwise only the DNA-self-assembly sets the limits, and those have been pushed very far already.”
<?xml version="1.0" encoding="UTF-8"?> Fractals and biomimetics just helped to surpass the performance of today’s transparent electrode materials Image: M. Giersig/HZB If you take a close look at a leaf from a tree and you’ll notice the veins that run through it. The structure these veins take are what’s called a quasi-fractal hierarchical networks. Fractals are geometric shapes in which each part has the same statistical character of the whole. Fractal science is used to model everything from snowflakes and the veins of leaves to crystal growth. Now an international team of researchers led by Helmholtz-Zentrum Berlin have mimicked leaves’ quasi-fractal structure and used it to create a network of nanowires for solar cells and touch screen displays. Indium tin oxide (ITO) has been the go-to material for transparent conductors in displays and solar cells. While the costs associated with ITO have been one of the main knocks against it, it’s been difficult for the various nanomaterials proposed as alternatives to replace it. Nanomaterials—including silver nanowires, carbon nanotubes and graphene—have not only been handicapped by their own relative high costs, but their performance has been somewhat lacking as well. With this new method of distribution, nanowires are able to surpass the performance of traditional ITO layers. The reason for this becomes a little clearer when you go back and look at the leaf. The distribution of veins in the leaf is determined in part by the amount of shade and sunlight the leaf receives. With ITO, the material is spread out in one continuous, uniform film. However, the way the sunlight strikes a solar cell or the way a finger presses on a touch-screen display are not uniform. This reduces the ITO layer’s efficiency. In research described in the journal Nature Communications , the international research team used a quasi-fractal hierarchical network to optimize the distribution of the nanowires on a solar cell according to three conditions: provide maximum surface coverage, achieve a uniform current density, and have a minimal overall resistance. “On the basis of our studies, we were able to develop an economical transparent metal electrode," Michael Giersig, a professor at Helmholtz-Zentrum Berlin and who led the research, said in a press release. “We obtain this by integrating two silver networks. One silver network is applied with a broad mesh spacing between the micron-diameter main conductors that serve as the ‘highway’ for electrons transporting electrical current over macroscopic distances.” Next to this broad highway for the electrons, the researchers added randomly distributed nanowire networks that serve as local conductors to cover the surface between the large mesh elements. “These smaller networks act as regional roadways beside the highways to randomize the directions and strengths of the local currents, and also create refraction effects to improve transparency,” according to Giersig. Solar cells with the leaf-vein network had an efficiency of 5.91 percent in experiments. Those with a standard ITO had 5.37 percent.
A transparent flexible thin-film triboelectric nanogenerator for scalable electricity generationGuang Zhu; Xiao Yan Wei; Zhong Lin WangInternational Journal of Nanomanufacturing, Vol. 12, No. 3/4 (2016) pp. 396 - 403We report a flexible thin-film-based triboelectric nanogenerator (TF-TENG) that has a one-component laminated structure as thin as 100 µm. The electricity-generating process of the TF-TENG takes advantage of the interaction between the TF-TENG and an external object that carries triboelectric charge on the surface. The motion of the object creates electric potential difference between two electrodes on the TF-TENG, which then produces electron flow in the external circuit. When triggered by foot stomping, a TF-TENG (20 cm by 20 cm) spread on the floor could generate an open-circuit voltage of 700 V, a short-circuit current of 3 mA, and an instantaneous power of 168 mW that corresponds to a power density of 4.2 W/m<SUP align="right">2</SUP>. The generated electricity could simultaneously power 1,000 LEDs. The TF-TENG can be tailored to any desired size and shape that are suitable in a variety of circumstances as long as contacts with external objects take place. When the TF-TENG is scaled up in area and used in places that have large flows of people such as subway stations and shopping malls, the produced electric energy in total may become considerable.
<?xml version="1.0" encoding="UTF-8"?> A novel molecule changes the game in flexible nonvolatile memory, potentially ushering a new era in wearable electronics Illustration: Paolo Samori/University of Strasbourg & CNRS Irradiation with either blue or green light is used to respectively "write" or "erase" information on a flexible transistor device. The molecular switch contained in a semiconducting polymer matrix undergoes reversible interconversion between its two forms, interacting (trapping) or not with the current flowing through the semiconductor. A regular stream of breakthroughs with organic nanomaterials for use in flexible electronics has observers scratching their heads as to why we aren’t seeing more of these technologies in applications such as wearable electronics. The problem has been that although organic nanomaterials have made flexible logic circuits and displays possible, they have pretty much failed to yield flexible, nonvolatile memories with write/erase speeds that would make them practical. Now a team of researchers hailing from the University of Strasbourg and the Centre National de la Recherche Scientifique (CNRS) in France, along with collaborators from Humboldt University of Berlin and the University of Nova Gorica, in Slovenia, has developed a flexible nonvolatile optical memory thin-film transistor device made from organic nanomaterials that may change the game in wearable electronics. To date, the major challenge in developing flexible organic memories has been creating a stable system that doesn’t lose data over time (volatility), is flexible, and offers an acceptable number of write/erase cycles (endurance). The international research team overcame all of those hurdles, but they wanted more. “We wanted every single device to be able to store more than just a single bit (multilevel operation); we achieved 8 bits,” said Emanuele Orgiu, a researcher at CNRS and one of the authors of the paper, in an email interview with IEEE Spectrum. “In addition, our devices can be made from solutions directly on a plastic substrate, and they feature very fast response times (within nanoseconds)—an intensely sought-after property for organic semiconductors, which usually exhibit very long response times (greater than a millisecond),” added Orgiu. In a paper published in the journal Nature Nanotechnology , the team explains that it was able to achieve all of this by fabricating the device from molecules known as diarylethenes (DAEs), which can be switched between two states (called either open or closed form). Switching from writing to erasing was as simple as adjusting the wavelength of the light hitting the material (blue light for writing, green for erasing). “The DAEs used in our work are particularly suited for nonvolatile data storage, since their two forms are stable at ambient conditions,” explained Tim Leydecker, another researcher from CNRS who is a member of the research team. “Plus, they can be switched even when embedded within a semiconducting polymer matrix, making them an ideal candidate for flexible films.” explains that the molecules’ fast response to a 3-nanosecond laser pulse is relevant to modern electronics. Another benefit of the DAE molecules is that the amount of molecules that are switched in reaction to the light can be precisely controlled, which is a key requirement for multi-level storage that improves the data density. Paolo Samorì, another team member from CRNS, explained that the molecules’ fast response to a 3-nanosecond laser pulse brings them right in line with modern electronics. Samorì added that another benefit of the DAE molecules is that the number of molecules that are switched in reaction to the light can be precisely controlled—a key requirement for improved data density in multilevel storage. The devices they have fabricated so far are laboratory prototypes, and thus are relatively large at 1 square millimeter. Needless to say, miniaturization and encapsulation will need to be addressed in order for these memories to become a commercial product. However, the rearchers already have these issues in their sights, and plan to continue testing the performance and stability of the devices after encapsulation. The team will also be examining fabrication processes compatible with industrial output, such as roll-to-roll manufacturing and inkjet printing. Stefan Hecht, a team member from Humboldt University of Berlin, added: “Implementation into electronics featuring other organic components (organic light-emitting diodes and organic field-effect transistors) is an important step, as the entire system would benefit from the advantages of organic electronics.”
<?xml version="1.0" encoding="UTF-8"?> Ultrafast synthesis of high-quality graphene films combined with roll-to-roll processes ushers in a new era in graphene production Image: Peking University/Nature Nanotechnology The adaptation of chemical vapor deposition (CVD) production of graphene so that it’s compatible with roll-to-roll processing is transforming graphene manufacturing. That effort is being led by companies like Graphene Frontiers, based in Philadelphia. However, the production of single-crystal graphene on copper foils in a CVD process remains a fairly time consuming procedure. Fabrication of centimeter-size single crystals of graphene still takes as much as a day. Now researchers at Hong Kong Polytechnic University and Peking University have developed a technique that accelerates the process so that the growth happens at 60 micrometers per second—far faster than the typical 0.4 µm per second. The key to this 150-fold speed increase was adding a little oxygen directly to the copper foils. In the research, which is described in the journal Nature Nanotechnology , the China-based researchers placed an oxide substrate 15 micrometers below the copper foil. The result: a continuous supply of oxygen that lowers the energy barrier to the decomposition of the carbon feedstock, thereby increasing the graphene growth rate. The expectations were that the oxide substrate would release the oxygen at the high temperatures inside the CVD surface (over 800 degrees Celsius). The researchers confirmed this through the use of electron spectroscopy. While the measurements indicated that oxygen was indeed being released, the amount was still fairly minimal. Nevertheless, this minuscule amount of oxygen proved sufficient for their purposes because the very small space between the oxide substrate and the copper foil created a trapping effect that multiplied the effect of the oxygen. In their experiments, the researchers were able to successfully produce single-crystal graphene materials as large as 0.3 millimeter in just five seconds. That, according to the researchers, is more than two orders of magnitude faster than other methods in which graphene is grown on copper foils. The researchers believe that this ultrafast synthesis of graphene makes possible a new era of scalable production of high-quality, single-crystal graphene films by combining this process with roll-to-roll methods. Counterintuitively, speeding up the process of producing single-crystal graphene films may not automatically lead to wider adoption of graphene in various devices. Just a few years ago, graphene production was stuck at around a 25-percent utilization rate, and there is no reason to believe that demand has increased enough to have dramatically changed those figures. (Graphene producers will tell you that if demand for CVD-produced graphene suddenly spiked, volume could be doubled nearly overnight.) Nonetheless, speed in manufacturing is always an attractive option for any product. It just might not offer a change to the graphene landscape as much as a few “killer apps” might.
<?xml version="1.0" encoding="UTF-8"?> By applying a voltage to graphene sandwiching a piece of paper, researchers have created a new display technology Images: Bilkent University Graphene has been building quite a reputation for itself in flexible displays. Among the ways graphene has been used in this field is as an alternative to the relatively scarce indium tin oxide (ITO), a transparent conductor that controls display pixels. Graphene has also been used in a display’s pixel electronics, or backplane, where a solution-processed graphene is used as an electrode. Now researchers at Bilkent University in Ankara, Turkey, have demonstrated that an ordinary sheet of paper that is sandwiched between two films of multilayer graphene can act as a rudimentary flexible electronic display. In an interview with Nature Photonics , the corresponding author, Coskun Kocabas, says that this system could serve as a framework for turning ordinary printing paper into an optoelectronic display. Kocabas explained: We would like to fabricate a display device that can reconfigure the displayed information electronically on a sheet of printing paper. Several technologies based on electrophoretic motion of particles, thermochromic dyes and electrowetting of liquids have been developed to realize electronic paper, or e-paper, which has great potential for consumer electronics. Contrasting with the primary aim of e-paper, these technologies, however, are not compatible with conventional cellulose-based printing papers. The researchers described their device in the journal ACS Photonics. It operates by applying a bias voltage to the graphene to trigger an intercalation of ions so that the optical absorption of the graphene layers is altered. That turns them from transparent to dark and back again. (Intercalation is the reversible inclusion of a molecule or ions between two other molecules in multilayered structures or compounds.) In the experiments, the display’s transition to transparent takes a bit of time— about 4 seconds; reverting to its darker form takes under half a second. While this may be suitable for signs that don’t need to change their images that often, the lapse is still too long for display applications that require quick refresh times. The multilayer graphene was produced through chemical vapor deposition in which the graphene is grown on a metal surface inside a furnace. After it’s removed from the furnace, the metal is etched away, leaving a thin film of graphene on the surface of the water in which the etching occurs. Then the paper is simply submersed into the liquid, which transfers the thin film of graphene onto the paper. While the initial experiments showed that there were some issues with oxidation of the doped graphene layers, the researchers believe that this hiccup can be overcome with the addition of a simple polymer coating. In future research, Kocabas and his colleagues are planning to make a fully functional sheet of e-paper with pixels and an integrated driving circuit. They would like to see the process they have developed adapted into a roll-to-roll-compatible manufacturing process.
At UChicago's Nanofabrication Facility, Innovation Happens on a Molecular ScaleChicago InnoThis February UChicago's Institute for Molecular Engineering (IME) opened the 10,000 square foot Pritzker Nanofabrication Facility, which features fabrication tools that allow researchers and industry to create and experiment with materials that make ...
Novel platform detects cancers by exploiting the abnormal "leakiness" of tumour blood vessels.
Breakthrough with a chain of gold atoms: In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Heat transport is of similar fundamental importance and its control is for instance necessary to efficiently cool the ever smaller chips. An international team including theoretical physicists from Ko...
Engineers at the University of California San Diego have developed a material that could reduce signal losses in photonic devices. The advance has the potential to boost the efficiency of various ligh...
You may not realize it but alien subatomic particles raining down from outer space are wreaking low-grade havoc on your smartphones, computers and other personal electronic devices.
Liquid metal nano printing set to revolutionize electronics: Creating integrated circuits just atoms thick
A new technique using liquid metals to create integrated circuits that are just atoms thick could lead to the next big advance for electronics.
Researchers at The University of Texas at Dallas have created an atomic force microscope on a chip, dramatically shrinking the size -- and, hopefully, the price tag -- of a high-tech device commonly u...
Francis (Frank) Alexander, a physicist with extensive management and leadership experience in computational science research, has been named Deputy Director of the Computational Science Initiative at...
Silicon nanocrystals are efficient materials for luminescent solar concentrators.
A new graphene and nanomaterials research centre, known as MackGraphe, has officially opened in São Paulo
University of Sydney has unveiled the country’s first purpose-built nanoscience institute