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Following up on previous theoretical predictions, researchers now have demonstrated two high-yield methods for fabricating antimonenes - wide-band-gap semiconductors that under strain become direct band-gap semiconductors. Such dramatic transitions of electronic properties could open a new door for nanoscale transistors with high on/off ratio, blue/UV optoelectronic devices, and nanomechanical sensors based on new ultrathin semiconductors. The new approach is generic for various transparent conducting oxides as well as other oxide nanocrystal inks.
Plastics NewsGrant will support development of flexible electronics at UMass ...Plastics NewsResearchers from the UMass Lowell Nanomanufacturing Center and Raytheon Integrated Defense Systems are using a $1.89 million Nextflex grant to advance ...NextFlex awards $1.9m to UMass Lowell - The Boston GlobeThe Boston Globeall 2 news articles »
Whitman, Lloyd J. and Henderson, Lori A. and Meador, Michael A. and Friedersdorf, Lisa E. and Standridge, Stacey and Thomas, Treye and Howard, John and Biaggi-Labiosa, Azlin M. and Madsen, Lynnette D. and Cannizzaro, Chris and Jillavenkatesa, Ajit and Bobalek, John F.. National Science and Technology Council, Office of Science and Technology Policy, Nanoscale Science, Engineering, and Technology Subcommittee. (2016) 2016 National Nanotechnology Initiative Strategic Plan. Technical Report. United States National Nanotechnology Initiative. (Unpublished)
MIT has been honored with the UNESCO Medal for contributions to the development of nanoscience and nanotechnologies by the United Nations Educational, Scientific and Cultural Organization (UNESCO). Established in 2010, the UNESCO Medal has awarded over 30 prominent scientists and public figures for their individual contributions to advancing the fields of nanoscience and nanotechnologies. This year MIT shares the distinction, along with St. Petersburg State University of Information Technologies in Russia, of being the first organization to be recognized. In addition to the two universities, four eminent scientists from Korea, the United Arab Emirates, Ukraine, and the United Kingdom, were recipients of the medal. An awards ceremony was held on Oct. 11 at the UNESCO headquarters in Paris, France. Institute Professor Mildred (Millie) Dresselhaus, a nanoscience pioneer who herself has won many recognitions including the U.S. Presidential Medal of Freedom and the L'Oreal-UNESCO Award for Women in Science, made the trip at the invitation of President Rafael Reif to accept the medal on behalf of MIT. “Using science and technology as a way to bring people together is something MIT has learned to do really well,” says Dresselhaus. “Our faculty, staff, and students come together from countries all over the world with diverse technical backgrounds to work across the many academic departments and laboratories on campus. This culture of interdisciplinary collaboration enables us to work for common goals, so it made sense to me that MIT was recognized as an institution. This should serve as encouragement to move forward as rapidly as possible to complete MIT.nano and to achieve some exceptionally great outcomes through this initiative as it comes to fruition.” The award will eventually be displayed within the public spaces of MIT.nano — the 214,000-square-foot center for nanoscience and nanotechnology that is currently under construction in the heart of the MIT campus — after the building opening in June 2018, says Vladimir Bulović, faculty lead of the project. The UNESCO Medal is an initiative of the International Commission responsible for developing the Encyclopedia of Life Support Systems theme on nanoscience and nanotechnologies. Each year, the medal recognizes those making significant contributions in the field in an effort to showcase the tremendous benefits of progress being made. MIT joins a distinguished group of scientists who have received the medal thus far, including Nobel Prize-winners in physics Zhores Alferov and Isamu Akasaki.
Selenium (Se) is a metalloid element found in trace amounts in the earth’s crust and which has found extensive application due to its semiconducting properties. The use in photocopiers, microelectronic circuits and other applications has created a demand which makes selenium a valuable element. Selenium also shows biological activity with a strong dependence on concentration: it is essential in low doses for mammalian organisms but becomes strongly toxic to humans over a certain intake threshold. Efficient removal of selenium from wastewater being discharged in the environment is imperative and the development of cost-effective procedures to achieve this needs to be addressed. Under typical environmental conditions Se can be found in a variety of oxidation states (-II, 0, IV, and VI). The former two are insoluble and give rise to little toxicity on account of their low mobility in aqueous phases. The latter two however are found as highly mobile oxyanions which are the principal targets for Se removal. Finding the right reagent Ling et al have used an established strategy involving the reduction of Se(IV) to the insoluble Se(0) form, but their choice of nanoscale zero-valent iron (nZVI) as the reagent has led to a superior method of wastewater decontamination being developed. As little as 0.2 g L-1 nZVI can achieve over 99% removal of high levels of Se(IV) within 5 hours. Additionally, on account of the magnetic properties of the nZVI its recovery could be achieved simply with the use of a magnet, leaving pure elemental selenium as the product. The potential for elemental selenium recovery and recycling provides grounding for the method becoming cost-neutral or even profitable. Furthermore, in depth studies were conducted to elucidate the pathway taken by the decontamination process, with attention focused on the nano- and microstructure of the resulting Se particles and of the nZVI before and after reaction. The nZVI particles consist of a metallic iron core surrounded by an oxide layer which under aqueous conditions is capable of performing adsorption of Se oxyanions, thus paving the way for their reduction by the metallic core. Two types of Se structures result following the reductive process: almost perfectly spherical nanoparticles and nano-needles, both being attributed to known forms of elemental Se: amorphous and trigonal, respectively. A complete account of the Se(IV) reduction and Se(0) structure formation mechanisms operating in this process is available in the full article, free to view for a limited time:* Genesis of pure Se(0) nano- and micro-structures in wastewater with nanoscale zero-valent iron (nZVI) Environ. Sci.: Nano, 2016, Advance Article DOI: 10.1039/C6EN00231E About the webwriter Dan Mercea is a PhD student in the Fuchter group at Imperial College London. He is working on developing enantioselective FLP catalysis. —————- *Access is free until 9th December 2016 through a registered RSC account – register here
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.
Three UT Austin Professors Named Fellows of the National Academy of Inventors - UT News | The University of Texas at Austin
UT News | The University of Texas at AustinThree UT Austin Professors Named Fellows of the National Academy of InventorsUT News | The University of Texas at AustinSreenivasan has published more than 100 technical articles and holds more than 100 U.S. patents in the area of nanomanufacturing. He has received several awards for his work including the Technology Pioneer Award by the World Economic Forum (2005), ...and more »
A successful production trial by Australian battery technology innovator Nano-Nouvelle has proved its pioneering nanotechnology supports industrial-scale manufacture, with output rates...
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: 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. 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 ...
Duane Boning has been named the Clarence J. LeBel Professor of Electrical Engineering. The chair is named for Clarence Joseph LeBel '26, SM '27, who co-founded Audio Devices in 1937, and was a pioneer in recording discs, magnetic media for tapes, and in hearing aids and stethoscopes. “Boning’s teaching is recognized as outstanding at both the undergraduate and graduate levels, and he is a leader in the field of manufacturing and design,” said Anantha Chandrakasan, the Vannevar Bush Professor of Electrical Engineering and head of the Department of Electrical Engineering and Computer Science (EECS). “This is fitting recognition of his outstanding contributions to research, teaching, mentoring, and service.” Boning’s research focuses on manufacturing and design, with emphasis on statistical modeling, control, and variation reduction in semiconductor, MEMS, photonic, and nanomanufacturing processes. His early work developed computer integrated manufacturing approaches for flexible design of IC fabrication processes. He also drove the development and adoption of run-by-run, sensor-based, and real-time model-based control methods in the semiconductor industry. He is a leader in the characterization and modeling of spatial variation in IC and nanofabrication processes, including plasma etch and chemical-mechanical polishing (CMP), where test mask design and modeling tools developed in his group have been commercialized and adopted in industry. Boning served as editor in chief for the IEEE Transactions on Semiconductor Manufacturing from 2001 to 2011, and was named a fellow of the IEEE for contributions to modeling and control in semiconductor manufacturing in 2005. In addition to creating the graduate-level course 6.780J/2.830J (Control of Manufacturing Process), he has lectured in several core EECS subjects, including 6.003 (Signals and Systems) and 6.001 (Structure and Interpretation of Computer Programs), and is also an outstanding recitation and laboratory instructor. His teaching has been recognized with the MIT Ruth and Joel Spira Teaching Award. Boning won the Best Advisor Award from the MIT ACM/IEEE student organization in 2012 and the 2016 Capers and Marion McDonald Award for Excellence in Mentoring and Advising in the School of Engineering. Boning served as associate head from Electrical Engineering in EECS from 2004 to 2011. He has previously and presently serves as associate director in the Microsystems Technology Laboratories, where he oversees the information technology and computer-aided design services organization in the laboratories. He is a long-standing and active participant in the MIT Leaders for Global Operations program. Since 2011, he has served as the director for the MIT/Masdar Institute Cooperative Program, fostering many joint activities between MIT and Masdar Institute. From 2011 through 2013, he served as founding faculty lead in the MIT Skoltech Initiative, working to launch the Skolkovo Institute of Science and Technology (Skoltech). Within MIT, Boning has served on several Institute committees, including as chair of the Committee on Undergraduate Admissions and Financial Aid (CUAFA) in 2007, and he will serve as chair of the Committee on the Undergraduate Program (CUP) in 2016-2017.
MIT researchers have developed low-cost chemical sensors, made from chemically altered carbon nanotubes, that enable smartphones or other wireless devices to detect trace amounts of toxic gases. Using the sensors, the researchers hope to design lightweight, inexpensive radio-frequency identification (RFID) badges to be used for personal safety and security. Such badges could be worn by soldiers on the battlefield to rapidly detect the presence of chemical weapons — such as nerve gas or choking agents — and by people who work around hazardous chemicals prone to leakage. “Soldiers have all this extra equipment that ends up weighing way too much and they can’t sustain it,” says Timothy Swager, the John D. MacArthur Professor of Chemistry and lead author on a paper describing the sensors that was published in the Journal of the American Chemical Society. “We have something that would weigh less than a credit card. And [soldiers] already have wireless technologies with them, so it’s something that can be readily integrated into a soldier’s uniform that can give them a protective capacity.” The sensor is a circuit loaded with carbon nanotubes, which are normally highly conductive but have been wrapped in an insulating material that keeps them in a highly resistive state. When exposed to certain toxic gases, the insulating material breaks apart, and the nanotubes become significantly more conductive. This sends a signal that’s readable by a smartphone with near-field communication (NFC) technology, which allows devices to transmit data over short distances. The sensors are sensitive enough to detect less than 10 parts per million of target toxic gases in about five seconds. “We are matching what you could do with benchtop laboratory equipment, such as gas chromatographs and spectrometers, that is far more expensive and requires skilled operators to use,” Swager says. Moreover, the sensors each cost about a nickel to make; roughly 4 million can be made from about 1 gram of the carbon nanotube materials. “You really can’t make anything cheaper,” Swager says. “That’s a way of getting distributed sensing into many people’s hands.” The paper’s other co-authors are from Swager’s lab: Shinsuke Ishihara, a postdoc who is also a member of the International Center for Materials Nanoarchitectonics at the National Institute for Materials Science, in Japan; and PhD students Joseph Azzarelli and Markrete Krikorian. Wrapping nanotubes In recent years, Swager’s lab has developed other inexpensive, wireless sensors, called chemiresistors, that have detected spoiled meat and the ripeness of fruit, among other things. All are designed similarly, with carbon nanotubes that are chemically modified, so their ability to carry an electric current changes when exposed to a target chemical. This time, the researchers designed sensors highly sensitive to “electrophilic,” or electron-loving, chemical substances, which are often toxic and used for chemical weapons. To do so, they created a new type of metallo-supramolecular polymer, a material made of metals binding to polymer chains. The polymer acts as an insulation, wrapping around each of the sensor’s tens of thousands of single-walled carbon nanotubes, separating them and keeping them highly resistant to electricity. But electrophilic substances trigger the polymer to disassemble, allowing the carbon nanotubes to once again come together, which leads to an increase in conductivity. In their study, the researchers drop-cast the nanotube/polymer material onto gold electrodes, and exposed the electrodes to diethyl chlorophosphate, a skin irritant and reactive simulant of nerve gas. Using a device that measures electric current, they observed a 2,000 percent increase in electrical conductivity after five seconds of exposure. Similar conductivity increases were observed for trace amounts of numerous other electrophilic substances, such as thionyl chloride (SOCl2), a reactive simulant in choking agents. Conductivity was significantly lower in response to common volatile organic compounds, and exposure to most nontarget chemicals actually increased resistivity. Creating the polymer was a delicate balancing act but critical to the design, Swager says. As a polymer, the material needs to hold the carbon nanotubes apart. But as it disassembles, its individual monomers need to interact more weakly, letting the nanotubes regroup. “We hit this sweet spot where it only works when it’s all hooked together,” Swager says. Resistance is readable To build their wireless system, the researchers created an NFC tag that turns on when its electrical resistance dips below a certain threshold. Smartphones send out short pulses of electromagnetic fields that resonate with an NFC tag at radio frequency, inducing an electric current, which relays information to the phone. But smartphones can’t resonate with tags that have a resistance higher than 1 ohm. The researchers applied their nanotube/polymer material to the NFC tag’s antenna. When exposed to 10 parts per million of SOCl2 for five seconds, the material’s resistance dropped to the point that the smartphone could ping the tag. Basically, it’s an “on/off indicator” to determine if toxic gas is present, Swager says. According to the researchers, such a wireless system could be used to detect leaks in Li-SOCl2 (lithium thionyl chloride) batteries, which are used in medical instruments, fire alarms, and military systems. Alexander Star, a professor of chemistry and bioengineering and clinical and translational science at the University of Pittsburgh, says the researchers’ design for a wireless sensor (or dosimeter) for electrophilic substances could improve soldier safety. “The authors were able to synthesize a [carbon nanotube] composite sensitive to … a class of chemicals of high interest for sensing,” Star says. “This type of device architecture is important for real-life application, due to the fact that a chemical weapon dosimeter worn by military and security personnel requires rapid reading.” The next step, Swager says, is to test the sensors on live chemical agents, outside of the lab, which are more dispersed and harder to detect, especially at trace levels. In the future, there’s also hope for developing a mobile app that could make more sophisticated measurements of the signal strength of an NFC tag: Differences in the signal will mean higher or lower concentrations of a toxic gas. “But creating new cell phone apps is a little beyond us right now,” Swager says. “We’re chemists.” The work was supported by the National Science Foundation and the Japan Society for the Promotion of Science.
<?xml version="1.0" encoding="UTF-8"?> Could safe, durable and high-temperature Li-S batteries lead to EV applications? Image: iStockphoto Lithium-sulfur (Li-S) batteries have been pursued as an alternative to lithium-ion (Li-ion) batteries for powering electric vehicles due to their ability to hold up to four times as much energy per unit mass as Li-ion. However, Li-S batteries don’t come without some problems. For instance, the sulfur in the electrode can become depleted after just a few charge-discharge cycles, or polysulfides can pass through the cathode and foul the electrolyte. Another issue Li-S batteries face is the difficulty of ensuring that they operate safely at high temperatures due to their low boiling and flash temperatures. Now, researchers at the University of Western Ontario, in collaboration with a team from the Canadian Light Source, have leveraged a relatively new coating technique dubbed molecular layer deposition (MLD) that promises to lead to safe and durable high-temperature Li-S batteries. This MLD technique is essentially an adaptation of the conventional atomic layer deposition (ALD) techniques that have been used to deposit thin inorganic oxide films. Where MLD departs from its predecessor is that it can incorporate organic components into the films, making it possible to create hybrid organic-inorganic thin films. MLD is a technique that has proven itself applicable for use in energy storage systems; it provides a high level of control over film thickness and the chemical composition of the target material at a molecular scale. In research described in the journal Nano Letters , the Canadian researchers were able to fabricate safe, high-temperature Li–S batteries on universal carbon–sulfur electrodes using an MLD alucone coating “We demonstrated that MLD alucone coating offers a safe and versatile approach toward lithium-sulfur batteries at elevated temperature,” said Andy Xueliang Sun, who led the research at the University of Western Ontario, in a press release. In the experiments, the researchers demonstrated that the MLD alucone coated carbon-sulfur electrodes remained stable and even showed improved performance at temperatures as high as 55 degrees Celsius. The researchers expect that these performance figures should significantly prolong battery life for high-temperature Li-S batteries.