Preparing for the ubiquitous technologies of tomorrow

 

NSF enlists National Academies experts to envision future multidisciplinary engineering research. August 5, 2015 What is needed to create ubiquitous future technologies that will enable new industries, and who will create them? Currently, NSF Engineering Research Centers address a variety of engineering and technological challenges as they pursue transformational research, education and innovation outcomes. This model has resulted in significant national returns on investment for 30 years. In consideration of significant, ongoing changes -- in science, engineering, education, economics, demographics, and the global landscape -- the National Science Foundation (NSF) seeks to ensure future engineering research centers will continue to benefit the nation. To do so, the NSF Directorate for Engineering has awarded a grant to the National Academy of Engineering (NAE) and the National Academies of Sciences, Engineering, and Medicine’s Division on Engineering and Physical Sciences for a study to determine what center-based research, education and innovation models could be the most effective as the U.S. and global landscapes undergo future shifts. “Our Engineering Research Centers, first developed nearly 30 years ago with the help of the National Academies, have yielded great advances in manufacturing, communications, biomedical, and other sectors,” said Pramod Khargonekar, NSF assistant director for engineering. “Now we are thinking of the next 30 years, and how to ensure that our center-scale investments in engineering research, innovation and education continue to create innovators and catalyze new technologies and industries for the benefit of all Americans.” "This announcement highlights a continuation of over three decades of collaboration between the National Science Foundation and National Academy of Engineering on multidisciplinary, center-based engineering research, development and innovation,” said NAE president C. D. Mote, Jr. “Collaborations that advance multidisciplinary engineering and develop talent for the great problems of our time are mandatory for leadership in this world of accelerating change." During the next two years, forward-thinking experts appointed by the presidents of the NAE and National Academy of Sciences will envision potential future opportunities, missions, measures and models for engineering research centers. The committee will evaluate center designs and features for their ability to achieve breakthrough, multidisciplinary discoveries and innovations and to prepare an inclusive, innovative engineering workforce for success. They will also anticipate forms of university-industry partnerships that will spur translational research and accelerate real-world deployment in the future, allowing centers to maximize their contributions to the innovation ecosystem in the coming decades. As part of their collection of data and perspectives, the committee of experts anticipates holding a public symposium in 2016. At the end of the project, the committee will publish a peer-reviewed report. Media Contacts Sarah Bates, NSF, (703) 292-7738, sabates@nsf.gov Nicole Flores, National Academy of Engineering, (202) 334-2226, nflores@nae.edu Program Contacts Garie Fordyce, NSF, (703) 292-4603, gfordyce@nsf.gov Sohi Rastegar, NSF, (703) 292-5379, srastega@nsf.gov Principal Investigator James Lancaster, National Academies of Sciences, Engineering, and Medicine, jlancaster@nas.edu Related Websites Previous engineering research center study by National Academies: http://www.nsf.gov/cgi-bin/good-bye?http://www.nap.edu/catalog/616/the-new-engineering-research-centers-purposes-goals-and-expectations "This announcement highlights a continuation of over three decades of collaboration between the National Science Foundation and National Academy of Engineering on multidisciplinary, center-based engineering research, development and innovation,” said NAE president C. D. Mote, Jr. “Collaborations that advance multidisciplinary engineering and develop talent for the great problems of our time are mandatory for leadership in this world of accelerating change." The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2015, its budget is $7.3 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 48,000 competitive proposals for funding, and makes about 11,000 new funding awards. NSF also awards about $626 million in professional and service contracts yearly.   Useful NSF Web Sites: NSF Home Page: http://www.nsf.gov NSF News: http://www.nsf.gov/news/ For the News Media: http://www.nsf.gov/news/newsroom.jsp Science and Engineering Statistics: http://www.nsf.gov/statistics/ Awards Searches: http://www.nsf.gov/awardsearch/

Study claims perovskite solar cells can recoup their energy cost within three months

 

Perovskite solar cells are reportedly able to recoup their energy cost much faster than normal silicon cells, although their short lifetime remains an issue (Credit: Northwestern University)

Scientists at Northwestern University and the U.S. Department of Energy have found that perovskite cells, one of the most promising solar technologies of recent years, can repay their energy cost over 10 times faster than traditional silicon-based solar cells. The finding confirms that, once issues related to cell longevity are ironed out, perovskite cells could soon bring us solar energy on the cheap, and do so with less impact on the environment over their lifetime.

Solar panel installations are doubtlessly having a positive impact on the environment, but quantifying their carbon footprint with some degree of precision – which is useful for comparing them to other means of energy production, including other renewables – is not a straightforward process. To get a more complete picture, it's important to consider not only the carbon emissions saved during the panel's operating life, but also the amount of energy that goes into materials processing, manufacture, repair, maintenance and, once it is no longer useful, disposal of the panel.

According to this metric, called the cradle-to-grave life cycle assessment, a typical solar panel takes a fairly long time, between two and three years, to offset the energy costs that went into producing it. This is because silicon-based solar panels must be manufactured inside a clean room using high-purity crystalline silicon wafers that can only form inside specialized high-temperature furnaces.

Scientists at Northwestern University have now calculated that, by contrast,perovskite-based solar cells have an energy payback time (EPBT) of only two to three months. According to the researchers, this is not only much faster than a silicon-based cell, but also significantly better than any other type of commonly available solar cell.

Energy payback time, or EPBT, for some of the best-known types of solar cells

Perovskite cells are the fastest-growing technology in the solar arena. Although they aren't quite as efficient at converting sunlight into electricity as silicon-based cells, they are catching up very quickly. More importantly, they are much cheaper to produce than normal panels, meaning that their commercialization could lead to a drastic drop in the cost of clean electricity.

Unlike traditional silicon-based cells, perovskites can be manufactured at a very low energy cost, without the need for sophisticated equipment, and in very few steps. A solution containing the electrode materials is coated onto a substrate and, once it evaporates, this solution produces dense layers of crystallized perovskite at a fraction of the cost and energy expenditure of other common solar panels.

According to the study, which analyzed the detailed energy expenditure for two different types of perovskite cells, raw materials contribute about 80 percent of the primary energy consumption for making the panels, suggesting that a better choice of materials could reduce the energy costs even further.

There are indeed plenty of issues with the current choice of materials for perovskite cells, which often make use of potentially toxic lead to absorb sunlight and improve conversion efficiency. The researchers also found that the use of gold, another common raw material, was even more problematic, since the process of mining this precious metal is extremely damaging to the environment.

But perhaps the biggest issue that perovskite cells are currently facing is that they are unable to brave the environment, since they are partly made from organic molecules that degrade quickly when exposed to the elements. Most perovskite cell designs currently lack a protective layer that could lengthen their lifetime, as this would reduce conversion efficiency.

Because of their very short lifetime, the researchers found that the overall CO2 impact of perovskite cells is still significantly higher than that of traditional silicon-based cells, which are much more durable with a reported average lifetime of approximately 20 years.

But if these issues are solved (which the researchers say could happen in as little as two years), perovskite cells could indeed rise to take the lion's share of the solar landscape in the near future, providing clean energy while having an even lower impact on the environment than the solar cells of today.

A paper describing the study appears in the latest issue of the journal Energy & Environmental Science.

Source: Northwestern University

Evolve™ 512 Delta EMCCD Camera

 

Unprecedented speed and sensitivity for super resolution applications Discover a new way to evolve your science with the fastest and most productive EMCCD camera available in the world. The Evolve 512 Delta empowers you with the potential to obtain research results in about half the time of previous 512 EMCCD cameras. Designed specifically for demanding Super-Resolution applications, this camera delivers an unprecedented new level of speed and sensitivity.   Now with LightSpeed™ for 3,000 frames per second New Purchase Incentives Available Key Camera Features Datasheets and Technical Resources Imaging Software and Drivers Published Articles and Research Contact Us EMCCD Cameras   |   CCD Cameras   |   Multichannel Imaging Systems   |   Retired Demo Cameras Primary Applications Super-Resolution SMF and Tracking Spinning Disk Confocal - Live Cell Intrinsic Imaging source : http://www.photometrics.com/products/emccdcams/evolvedelta.php

Researchers explore nanoscale structure of thin films

 

Tue, 08/04/2015 - 12:10pm Laura Mgrdichian, Brookhaven National Laboratory   Simon Billinge, author on the paper and a physicist with a joint position at Brookhaven National Laboratory and Columbia Univ.'s School of Engineering and Applied Science.The world’s newest and brightest synchrotron light source—the National Synchrotron Light Source II (NSLS-II) at the U.S. Dept. of Energy (DOE)’s Brookhaven National Laboratory—has produced one of the first publications resulting from work done during the facility's science commissioning phase. Published July 7 in the online edition of the International Union of Crystallography Journal, the paper discusses a new way to apply a widely used local-structure analysis tool—known as atomic pair distribution function (PDF) analysis—to x-ray scattering data from thin films, quickly yielding high-quality information on the films' atomic structure. The work creates new avenues for studies of nanocrystalline thin films. This work shows that NSLS-II—a DOE Office of Science User Facility with ultra-bright, ultra-concentrated x-ray beams—is already proving to be a game-changer in studies of thin films, which play a vital role in a large number of technologies, including computer chips and solar cells. Thin-film challenges In applications and during experiments, thin films (defined as having thicknesses from just a few to more than 1,000 nm, or billionths of a meter) are deposited onto a thick base, called a substrate, often made of crystalline wafers of silicon, silicon dioxide, or aluminum oxide. It is extremely difficult to study the structure of materials in this geometry because of the small amount of film material and large amount of substrate. To minimize the scattering of x-rays off the substrate, which tends to obscure the data from the tiny volume of sample, thin film x-ray studies are done using grazing incidence (GI) x-ray experiments. In GI studies, the x-ray beam grazes the surface of the film such that it reflects off the substrate, allowing the beam to illuminate as much of the film as possible while minimizing penetration through the film into the substrate. However, the small angle of incidence makes GI studies notoriously difficult to carry out and introduces serious complexities in data analysis. “Grazing-incidence diffraction experiments are tricky for crystalline materials, and have never successfully been done to obtain PDFs from films,” said one of the paper's authors, Simon Billinge, a physicist with a joint position at Brookhaven and Columbia Univ.'s School of Engineering and Applied Science. “The experiments are too painstaking and the data analysis is extremely challenging.” Studying the “atomic neighborhood” PDF provides local atomic structural information—that is, data for neighborhoods of atoms—by yielding the distances between all pairs of atoms in the sample. These distances appear as peaks in the data. In recent years, PDF has become a standard technique in structural studies of complex materials and can be used for samples that are bulk or nanoscale, amorphous or crystalline. The approach that Billinge and his colleagues devised leverages the high fluxes of photons coming from NSLS-II, which, together with novel data reduction methods recently developed in his group, creates data suitable for PDF analysis from a thin film. Essentially, it turns the standard GI experiment on its head: the beam is simply sent through the film from the back to the front. Eric Dooryhee, the lead scientist for the NSLS-II X-Ray Powder Diffraction (XPD) beamline, where the work was done, explained, “The first group of NSLS-II beamlines is now successfully transitioning from technical commissioning, which began back in the fall of 2014 when we first produced x-ray light, towards science commissioning, where we benchmark and test the beamline capabilities on real samples. Extracting the thin film's tiny signal from the substrate's large signal in this normal-incidence geometry is extremely technically difficult. Nonetheless, I told Simon that XPD should be up to the challenge.” Preview of future breakthroughs The group tested thin-film PDF (which they call tfPDF) with both crystalline and amorphous thin films, each about 360 nm thick. The collaboration includes the groups of Bo Iversen at Aarhus Univ. in Denmark and Dave Johnson from the Univ. of Oregon, who prepared the thin films. The first sample studied was an amorphous iron-antimony film on an amorphous borosilicate substrate mounted perpendicular to the x-ray beam. In order to isolate the contribution from the film, the substrate contribution was first determined by measuring the scattering pattern from a clean substrate. The signal from the film is barely visible in the raw data on top of the large substrate contribution, but could be clearly extracted during data processing. This allowed for a reliable, low-noise PDF that can be modeled successfully to yield the quantitative atomic structure of the film. The data led to high-quality PDFs for both amorphous and crystalline films—confirmed by comparison to control samples in a standard PDF setup. Based on the success of these first measurements, the Billinge group and the XPD team are now planning future experiments to watch the films crystallize in real time, in the beam. “The discovery that we can get PDFs from samples in thin-film geometry so readily will revolutionize this area of science,” said Kirsten Jensen, a postdoctoral researcher in Billinge’s group at Columbia. “The experiments don’t take any specialized equipment or expertise beyond the beamline setup at XPD and are quick, opening the way to time-resolved in-situ studies of changes in film structure under processing as well as spatially resolved studies of nanostructured films in place.”  Added Billinge, “This is an exciting new result by itself, but it only gives us a glimpse of the possibilities that NSLS-II will present as the power ramps up over the next few years. This is the tip of the iceberg of what will be possible when NSLS-II is operating at full power.” Source: Brookhaven National Laboratory

Algae Bloom in Lake St. Clair

 

On July 28, 2015, the Operational Land Imager (OLI) on the Landsat 8 satellite captured images of algal blooms around the Great Lakes, visible as swirls of green in this image of Lake St. Clair and in western Lake Erie.

Earlier in July, NOAA scientists predicted that the 2015 season for harmful algal blooms would be severe in western Lake Erie. They suggest that algae growth in western Lake Erie could rival the blooms of 2011. Algae in this basin thrive when there is an abundance of nutrients (many from agricultural runoff) and sunlight, as well as warm water temperatures. The season runs through summer and peaks in September.

Research confirmed that in 2011, phosphorus from farm runoff combined with favorable weather and lake conditions to produce a bloom three times larger than previously observed. The researchers noted that if land management practices and climate change trends continue, the lake is likely to see more blooms like the 2011 event.

Harmful algal blooms can lead to fish kills. They also can affect the safety of water for recreation and for consumption (as was the case in Toledo, Ohio, and southeast Michigan during a 2014 bloom). As of July 30, 2015, drinking water was reported to be safe in these areas.

In April 2015, NASA and several partners announced a new multi-agency effort to develop an early warning indicator for harmful algal blooms in fresh water. The system is expected to make ocean color satellite imagery more easily available to environmental and water quality managers.

More information and annotated images: NASA Earth Observatory

Image Credit: NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey
Caption: Kathryn Hansen

Last Updated: Aug. 4, 2015

Editor: Sarah Loff

Some funny pics

 

22 fotos incríveis de pais e filhos na mesma idade

 

O trabalho que vou compartilhar hoje é de origem desconhecida, porém incrivelmente interessante e com um toque de emoção.

Na galeria abaixo você vai se impressionar com a semelhança de pais e filhos, mães e filhas, avôs e netos e por aí vai! Algumas das fotos foram tiradas nas mesmas posições que seus antecessores tiraram e com a mesma idade. O resultado é simplesmente impressionante, inspire-se!

Pai e filha

Vó e neta

Mãe e filha

Mãe e filha e neta

Vó, filha e neta

Mãe e filha

Pai e filho

Pai e filha

Mãe e filha

Pai e filha

Pai e filho

Pai e filho

Pai, filho e neto

Mãe e filha

Mãe e filha

Pai e filho

Vó e neta

Mãe e filha

Pai e filha

Pai e filho

Mãe e filha

source:

http://www.fotoshot.com.br/22-fotos-incriveis-de-pais-e-filhos-na-mesma-idade/

GE atomic swimmer robot keeps tabs on nuclear reactors

 

The Stinger is designed to inspect nuclear reactors without the need of a human team inside the containment vessel (Credit: GE Hitachi) One truism of nuclear reactors is that you really don't want to be next to one. Unfortunately, reactor cores need to be inspected and maintained, which means teams of workers going inside the containment vessel. It's an operation that's not only hazardous, but expensive and time consuming. In an effort to make such inspections safer, cheaper, and faster, GE Hitachi Nuclear Energy has developed the Stinger; a free-swimming, remote-controlled robot that replaces humans for cleaning and inspecting reactor vessels. Nuclear reactors are not the easiest thing in the world to inspect. Immersed in a pool of water for coolant and to moderate the nuclear reaction, the reactor and the water vessel that contains it requires periodic cleaning and inspection to ensure that it's safe and operating efficiently. The trouble is, such inspections are expensive and surprisingly labor intensive. Part of the problem is that special bridges need to be hauled in and installed over the pool, so workers can walk out with poles tipped with tools and instruments to do their job. This operation is not only burdensome, but it also exposes the team to radiation, which the industry obviously tries to avoid, and interrupts the on-going operations to remove and replace spent fuel rods. The GE Hitachi Stinger is designed to simplify the whole inspection task by replacing the team and the bridge with a free-swimming robot that looks a bit like a gigantic mechanical seahorse. Instead of using a rail or a track, the robot swims about using an advanced camera and remote positioning technology while being controlled by an operator in a tent away from the radiation area. This not only removes the need for a bridge, but also allows refueling operations to continue uninterrupted. "Stinger performs inspections of welds within nuclear reactors. It remotely operated and swims to these welds within this highly irradiated area," said Jerry Dolan, Senior Tooling Manager at GE in an interview with Gizmag. "Stinger uses a hydrolaser to blast welds with water before it shoots HD video of the weld. This video is then beamed near real-time to Nuclear Regulatory Commission-approved inspectors at our global Center of Excellence in Wilmington, NC, where they are analyzed. "Stinger literally replaces eight people standing on the bridge of the reactor lowering cameras and brushes with ropes and pulleys. It is much faster and more accurate than previous methods while also significantly reducing radiation dose." Dolan went on to explain that the robot uses multiple thrusters to navigate, and depth, pitch, and roll sensors stabilize and position itself. In a separate interview, John Lizzi, Manager of the Distributed Intelligent Systems Laboratory at GE Global Research, sites the Stinger as one example of the company's service robotics strategy. The robot been in operation for 1½ to 2 years, and in the future it may be upgraded to carry out maintenance and repair operations as well as inspections. Source: GE Hitachi

Innovations from the wild world of optics and photonics

 

Princeton research team explores ways of communicating and processing signals with light waves A silicon photonics platform connecting excitable lasers to form a photonic neural network. July 31, 2015 Traditional computers manipulate electrons to turn our keystrokes and Google searches into meaningful actions. But as components of the computer processor shrink to only a few atoms across, those same electrons become unpredictable and our ability to shuttle them across long and short distances diminishes. With support from the National Science Foundation (NSF), the Lightwave Communications Laboratory at Princeton University, led by Paul Prucnal, seeks to understand, build, and design the next generation of communication systems that process information far faster than today's devices using photonics, or the manipulation of light. The field of photonics began, roughly, with the invention of the laser in the late 1950s and found widespread applications in the 1990s with the explosive growth of the Internet. Photonics not only made high-speed long-distance data transmission via fiber optic cables feasible and affordable, it has also enabled advances in laser manufacturing, chemical sensing, medical diagnostics, display technologies and many other fields. But scientists are betting that not all of light's secret abilities have been discovered yet. In his lab at Princeton, Prucnal and his team have been experimenting with a variety of optics and photonics-based applications, creating systems to carry hidden messages, detect malicious cyber-attacks and improve the quality and capacity of wireless communications using light. They are even exploring whether it may be possible to create a network of photonic "neurons" to perform functions our brain does well--like pattern recognition--but significantly faster. Through partnership with industry, their innovations are moving quickly from the lab to the factory. Coping with billions of devices Currently, there are more mobile communication devices than humans on the planet, and this proliferation is expected to continue. However, the radio bandwidth on which wireless communications depend is a limited resource. As more and more devices compete for bandwidth, we can expect more bottlenecks and more interference from nearby competing antennas, said Matthew Chang, a Ph.D. student in Prucnal's lab. To handle the constant growth in demand for capacity and bandwidth, optical solutions are needed. "With a frequency 1 million times bigger than radio waves, optics sees the entire current radio-wave spectrum as practically a single frequency," Chang said. "In terms of its ability to provide the bandwidth for a growing army of mobile phones, we say it's future proof." In the near term, the lab is working on technologies that harness optical signal processing to improve the efficiency of the cell towers and mobile antennas already in place. One such technology the lab developed is called photonic beamforming. It involves encoding wireless signals on light waves to allow antennas to selectively detect signals from a desired spatial direction, operating with precision and over bandwidths that exceed what is possible with electronics. The phenomenon is akin to "the cocktail party effect," where one is able to tune in to the frequency and direction of a friend's voice in a crowded room. The human brain is adept at de-noising signals, Chang explained. "We know what direction the voice is coming from and can train our ears to sense in that direction." We also know what a friend's voice sounds like and can even read lips if we need to, he said. Radio antennas can't do that. "We want to design processors that give radio antennas the ability to sense a signal, lock on its spatial direction, and follow it to the source," Chang said. The technology that the team developed utilizes an array of antennas coupled to an adaptive processor to filter signals in both space and frequency. The technology allows the processor to steer the beam of radio waves while rejecting interfering directional noise sources. Their techniques can even apply algorithms that let the antenna system adapt to rapidly changing environments in order to track fast moving targets or rapidly switch between a wide-angle search and detailed inspection. Not surprisingly, many of the group's technologies are current of interest to the military. However, they imagine that one day every cell phone will contain a beamforming chip to better manage wireless inputs and outputs, the way many of today's phones contain a small component to switch between different wireless channels. Working with partners L3 Telemetry East and Bascom Hunter Technologies, which Prucnal helped found, the researchers are transferring the beamforming technology from the laboratory to the marketplace. Bascom Hunter received Phase 1 Small Business Innovation Research (SBIR) support from NSF in 2013 and 2015 to adapt their technologies for public safety radio networks and to improve the intermediate links between the core networks. They hope to see the technology improving the performance of cellphone towers and military applications within one or two years. More importantly, as data rates climb exponentially, the group sees optics and photonics as a way to provide gigabit or faster Internet to everyone, without the use of optical fiber. "The current processing of radio signals is akin to trying to sense and map the changing surface of the ocean by slowly sucking water through a single straw," said Prucnal. "Photonic processing makes it possible to process radio signals with greater precision and parallelism, and with greater speed, than electronics." Building a laser-fast brain If light-encoded Wi-Fi signals sounds far-out, another of the projects in Prucnal's lab is truly at the distant frontiers of research: the photonic neuron. The project came out of conversations between Prucnal and David Rosenbluth, a neuroscientist at Lockheed Martin, with which the lab collaborates. Prucnal noticed that the differential equations that describe the behavior of neurons have the same forms as the equations for lasers. Furthermore, in biological neurons, each has an internal voltage. If that voltage reaches a certain point, the neuron emits a spike, signaling the neurons to which it is connected. Likewise, a laser gets pumped with current, exciting more electrons from one state to another; at a certain point, the laser reaches its threshold and outputs an optical spike. The dynamics, they noted, were astonishingly similar, but lasers have the potential to perform the same action a billion times faster than the chemical signaling in the brain. This led the researchers to wonder if it was possible to design a synthetic system made of optical and photonic materials that could perform some of the functions of a physiological neuron. After developing a single photonic neuron in 2009, the research team has been working to build sophisticated, ultrafast signal processing circuits that mimic the visual, auditory, and motor functions found in biological organisms. Their initial implementation was inspired by the crayfish tailflip response--a natural wonder of high-speed sensing. Crayfish have a neuronal circuit in their brain that is networked in such a way that, if it senses danger, a specific set of neurons fire simultaneously, causing the creature to flip its tail to swim away with amazing speed. With this biological model in mind, Prucnal and his team designed a system that uses several excitable lasers, pre-loaded in such a way that if a particular signal comes in, the lasers recognize the specific pattern and fire a spike together. In the future, the researchers say such a device could be capable of making nearly instantaneous calculations in life-or-death situations, such as deciding whether to eject a fighter pilot from a jet. "When thousands of photonic neurons are networked together and working in unison, we believe we can build a processor that can sense patterns and cues with an almost human-like quality, but a billion times faster," said Bhavin Shastri, a post-doctoral fellow at Princeton working on the project. For example, the team imagines being able to peer into all the wireless signals around you, lock onto one of interest, and take action on it--all in an instant as the signal zooms across your antenna. The lab's research was featured on the cover of the IEEE Photonics Society Newsletter in June 2014; and in November 2014, the group published an article in IEEE's Journal of Lightwave Technology describing how to scale the signal-processing platform to large numbers of neurons. By finding new ways to encode and process light and by applying these methods to existing and brand new applications, Prucnal's group is helping to solve the looming bandwidth shortage while imagining entirely new capabilities for photonic systems. "With all the information that can be obtained using photonic processing of the radio image, we could track signals coming from all directions and all frequencies, separating multiple signals of interest from multiple interferers, quickly finding holes in the radio spectrum available for transmission, and mapping out spatial features of the radio environment in real-time," Prucnal said. "This vision is not only exciting, but will be necessary as the use of wireless communications proliferates in the future." -- Aaron Dubrow, NSF (703) 292-4489 adubrow@nsf.gov Investigators Paul Prucnal Related Institutions/Organizations Princeton University Locations Princeton , New Jersey Related Programs Networking Technology and System Enhancing Access to the Radio Spectrum Related Awards #1217435 NeTS: Small: Collaborative Research: OSTARA: An Optically-based Simultaneous Transmit and Receive Architecture for Enhancing Wireless Communications #1247298 EARS: Collaborative Research: Big Bandwidth: Finding Anomalous Needles in the Spectrum Haystack Years Research Conducted 2012 - 2015 Total Grants $450,000 Related Websites International Year of Light: http://www.light2015.org/Home.html Lightwave Communication Laboratory: http://ee.princeton.edu/research/prucnal/node?destination=node source : http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=135842&WT.mc_id=USNSF_51&WT.mc_ev=click

World's highest-performance single-molecule diode created

 

The creation of a single-molecule diode that is 50 times more efficient than anything produced before may help pave the way for much more practical molecular electronic components (Credit: Latha Venkataraman/Columbia University) As electronics miniaturization heads towards a theoretical physical limit in the tens of nanometers, new methods of manufacturing are required to produce transistors, diodes, and other fundamental electronic components. In this vein, a new range of molecule-sized devices have been created in the laboratory, though with varying results in terms of efficiency and practicality. Now a group of researchers from Berkeley Lab and Columbia University claims to have created the highest-performing, single-molecule diode ever made, which is said to be 50 times better in performance and efficiency than anything previously produced. Ordinary diodes are usually constructed from silicon with a p-n (positive-negative) junction created at the point of contact between a positively "doped" semiconductor (that is, one that has had its electrical properties altered with additives) and a negatively doped one. Flanked by connecting electrodes (an anode on one side and a cathode on the other), the most common function of such a diode is to permit electric current to flow in one direction only, whilst blocking current from flowing in the reverse direction. As such, a diode used in this way can be seen as a type of flow-control valve that is either "on" or "off". Technically, this one-way behavior is known as rectification as it can, for example, be used to rectify alternating current to direct current, and so these types of diodes are known as rectifiers. This on/off – asymmetric – behavior in the nascent field of molecule-sized electronics, on the other hand, is usually achieved by the creation of molecules that chemically emulate the p-n junction. However, these synthesized molecular junctions have generally resulted in poor forward current flow capabilities and inefficient or patchy rectification. This is where the Columbia university scientists claim to have made significant improvements with their new single-molecule diode. Diagram of the molecular junction that functions as a diode, allowing current to flow in one direction only "Using a single symmetric molecule, an ionic solution and two gold electrodes of dramatically different exposed surface areas, we were able to create a diode that resulted in a rectification ratio, the ratio of forward to reverse current at fixed voltage, in excess of 200, which is a record for single-molecule devices," said Jeffrey Neaton, director of the Berkeley Lab’s Molecular Foundry and professor at the University of California Berkeley. "The asymmetry necessary for diode behavior originates with the different exposed electrode areas and the ionic solution. This leads to different electrostatic environments surrounding the two electrodes and superlative single-molecule device behavior." First mooted in 1974 by Mark Ratner and Arieh Aviram, an asymmetric molecule that could act as a rectifier has been a long sought after goal, particularly as diodes form the basis of many microminiature electronic devices. Since then, a range of devices have been constructed, including single molecule diodes and transistors. Operating at this nanoscale, though, such devices may emulate their macro counterparts, but that behavior is merely a simulation; at such scales the electronic operation of these devices is governed more by quantum influences. "Electron flow at molecular length-scales is dominated by quantum tunneling," said professor "The efficiency of the tunneling process depends intimately on the degree of alignment of the molecule’s discrete energy levels with the electrode’s continuous spectrum. In a molecular rectifier, this alignment is enhanced for positive voltage, leading to an increase in tunneling, and is reduced for negative voltage. At the Molecular Foundry we developed an approach to accurately compute energy-level alignment and tunneling probability in single-molecule junctions. This method allowed myself and Zhenfei Liu to understand the diode behavior quantitatively." Zhenfei Liu – a postdoctoral fellow at Berkeley Lab – and professor Neaton worked with Latha Venkataraman and Luis Campos from Columbia University to create their high-performance rectifier diode using junctions prepared from symmetric molecules attached to gold electrodes. To achieve the necessary asymmetric properties required to operate as a diode, the researchers then altered the surface area of the electrodes as they were exposed to an ionic solution. As a result, a positive voltage increased the current significantly, whilst a negative voltage reduced current flow in an equally significant manner. "The ionic solution, combined with the asymmetry in electrode areas, allows us to control the junction’s electrostatic environment simply by changing the bias polarity," said professor Neaton. "In addition to breaking symmetry, double layers formed by ionic solution also generate dipole differences at the two electrodes, which is the underlying reason behind the asymmetric shift of molecular resonance. The Columbia group’s experiments showed that with the same molecule and electrode setup, a non-ionic solution yields no rectification at all." The combined Berkeley Lab-Columbia University research team is convinced that the way they have managed to produce a single-molecule diode sets the benchmark for future nonlinear nanoscale device tuning and development, with applications above and beyond just junctions of single-molecule components. "We expect the understanding gained from this work to be applicable to ionic liquid gating in other contexts, and mechanisms to be generalized to devices fabricated from two-dimensional materials," said professor Neaton. "Beyond devices, these tiny molecular circuits are petri dishes for revealing and designing new routes to charge and energy flow at the nanoscale. What is exciting to me about this field is its multidisciplinary nature – the need for both physics and chemistry – and the strong beneficial coupling between experiment and theory. With the increasing level of experimental control at the single-molecule level, and improvements in theoretical understanding and computational speed and accuracy, we’re just at the tip of the iceberg with what we can understand and control at these small length scales." The results of this research were recently published in the journal Nature Nanotechnology. Source: Berkeley Lab