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Flexible Nanosensors for Wearable Devices

February 26, 2015 - 7:44am
Researchers from UPM have developed a manufacturing method of aluminum optical nanosensors on versatile substrates that can be used for wearable devices and smart labels. A new method developed at the Institute of Optoelectronics Systems and Microtechnology (http://www.isom.upm.es/eng/index.php) (ISOM) from the Universidad Politécnica de Madrid (http://www.upm.es/internacional) (UPM) will enable the fabrication of optical nanosensors capable of sticking on uneven surfaces and biological surfaces like human skin. This result can boost the use of wearable devices to monitor parameters such as temperature, breath and heart pressure. Besides, it is a low cost technology since they use materials like standard polycarbonate compact disks, aluminum films and adhesive tapes that would facilitate its implementation on the market.Researchers from Semiconductor Devices Group (http://www.upm.es/observatorio/vi/index.jsp?pageac=grupo.jsp idGrupo=260) of ISOM from UPM have not only designed a manufacturing method of optical nanosensors over a regular adhesive tape but also have shown their potential applications. These flexible nanosensors enable us to measure refractive index variations of the surrounding medium and this can be used to detect chemical substances. Besides, they display iridescent colors that can vary according to the viewing and illumination angle, this property facilitates the detection of position variations and surface topography to where they are stuck at a glance. Nanosensors consist of dimensional nanohole arrays (250 nm) which are drilled into an aluminum layer (100 nm thick). In order to cause sensitivity to the surrounding mediums and iridescence effects, these nanostructures confine and disperse light according to the will of the engineer who designs them. The creation method for flexible nanosensors consists, firstly, on manufacturing sensors over a compact disc (CDs) of traditional polycarbonate, and secondly, transferring these sensors to adhesive Scotch tapes by a simple stick-and-peel procedure. This way, the nanosensors go from the CD surface to the adhesive tape (flexible substrate). The stick-and-peel process can be watched at: http://1drv.ms/1Jgf6Hd (http://1drv.ms/1Jgf6Hd) This new technology uses low cost materials such as polycarbonate CDs, aluminum, and regular adhesive tapes. The usage of noble metals to develop these types of sensors is common, but it is difficult mass production due to the high cost. Aluminum is 25,000 times cheaper than gold and has excellent electrical and optical properties. Besides, CD surfaces provide adherence to aluminum that is strong enough to manufacture the sensors over the CDs and weak enough to be transferred to the adhesive tape. This research is led by Dr. Carlos Angulos Barrios, a researcher from ISOM and Professor at the Department of Photonics Technology and Bioengineering (http://www.tfo.upm.es/) (TFB) of the School of Telecommunications Engineering (http://www.etsit.upm.es/index.php/en/), and also led by Víctor Canalejas Tejero, a PhD student of ISOM. The results were published in the Nanoscale journal ("Compact discs as versatile cost-effective substratesfor releasable nanopatterned aluminium films" (http://pubs.rsc.org/en/Content/ArticleLanding/2015/NR/C4NR06271J#!divAbstract) ).Source: Universidad Politécnica de Madrid (http://www.upm.es/internacional/UPM/UPM_Channel/News/03db4bb9a70cb410VgnVCM10000009c7648aRCRD)

NanoBCA Interview with Dr. Michael A. Meador, Director, NNCO

February 26, 2015 - 7:32am
NanoBCA was fortunate to engage in a conversation with Dr. Michael A. Meador, the recently appointed Director of the National Nanotechnology Coordination Office (“NNCO”) on February 10, 2015. Dr. Meador, who is technically on loan from NASA to NNCO for this assignment, has a Ph.D. in Chemistry from Michigan State University where he began his career thinking about matter at the molecular scale. While at NASA, Dr. Meador’s efforts included development of “game-changing” technologies from the TRL 4 to TRL 6 levels with a focus on specific technologies such as carbon nanotube based structural composites, nano-based sensors for chemical and biotech detection, among others. The following excerpt, from the NNCO website, outlines Dr. Meador’s impressive credentials and background with regard to nanotechnology. Dr. Meador, chair of NASA’s Nanotechnology Roadmap Team, was instrumental in developing the NASA-wide Nanotechnology Project, and has been responsible for project planning and advocacy, overseeing technical progress, developing external partnerships to advance and transfer technology, coordinating with other nanotechnology related activities within NASA, and interacting with program and senior agency management. He has also played a key role in representing NASA in the NNI’s interagency activities, including co-chairing its Nanomanufacturing, Industry Liaison, and Innovation Working Group. During his long career at NASA, Dr. Meador has held a series of positions with increasing responsibility, including over twenty years as Chief of the Polymers Branch of the Materials Division at NASA Glenn Research Center, where he expanded the research portfolio of the branch from research in high-temperature stable polymers and composites for aircraft engines to include work in battery electrolytes, fuel cell membranes, and nonlinear optical and sensor materials. He also initiated the first nanotechnology program at NASA Glenn. Dr. Meador has been recognized as the NASA Glenn Small Disadvantaged Business Program Technical Advocate of the Year and NASA Small Business Program Technical Personnel of the Year. He has also received the NASA Equal Opportunity Employment Medal for his work to increase the involvement of faculty and students from minority serving institutions in NASA materials research, and last month was awarded the NASA Exceptional Service Medal for leading NASA's Nanotechnology R D activities and representing the agency as a proactive member of the NNI. NanoBCA How long have you been a devotee of the science of nanotechnology? Dr. Meador Dating back to my graduate studies, I have long been aware of the great potential of working with matter at the molecular level. I carried this interest with me to NASA where, as Chief of the Polymers Branch at the Glenn Research Center, I launched one of the first research efforts with NASA focused on the development of nanomaterials technologies. Around 1999 or so, NASA started a long-term relationship with Dr. Richard Smalley of Rice University to focus on scaling up his HiPCO process to produce single wall carbon nanotubes so that we could have a sufficient quantity to evaluate as an additive for polymers. We were fortunate to be a part of that activity. The scale up approach developed under this activity led to Carbon Nanotechnologies Inc. So, I guess you can say that I have been involved with the science of nanotechnology for over 30 years. NanoBCA From a career perspective, what led you to become the Director at NNCO? Dr. Meador Over the course of my career, I have been involved in all aspects of nanotech research and development at a variety of levels within NASA from managing activities in my branch to more recently managing a NASA-wide project in nanotechnology. For the past four years I also served as NASA’s principal representative to the NSET, which gave me a broader perspective on nanotech R D at the Federal government level. It seemed like a very natural progression to aspire to a position like this at NNCO where I could give back, in a leadership role, and utilize my unique career experience with regards to nanotechnology. Personally, it is very exciting for me to be in a position to help push the NNI forward, especially now that it is at a crossroads in that it is coming out of a research and development focused effort to a more defined commercialization effort. NanoBCA The 21st Century Nanotechnology Research and Development Act was signed into law on December 3, 2003. What do you see as the major successes of this Act and what needs to be done going forward? Dr. Meador If not for National Nanotechnology Initiative (“NNI”), which preceded and was then reauthorized by the 21st Century Nanotechnology Research and Development Act, certain industries would not have been created, or at a minimum, would have been created at a much later date. That alone is a very significant accomplishment of the NNI. For instance, the quantum dot industry would not be where it is today if not for the NNI. As you know, Sony announced a new TV recently at the Consumer Electronics Show that will incorporate quantum dots produced by QD Vision, Inc. to enhance picture quality. QD Vision won the 2014 Presidential Green Chemistry Challenge Award (http://www2.epa.gov/green-chemistry/presidential-green-chemistry-challenge-winners) from the U.S. Environmental Protection Agency, which is the highest domestic honor in the field, recognizing chemical technologies that incorporate the principles of green chemistry into chemical design, manufacture, and use. So, it is clear that the quantum dot industry is making an important impact on our economy, and our environment, and it is an industry that is here to stay. Another example is the carbon nanotube sector, with companies like Nanocomp Technologies, Inc. that are producing materials that not only reduce weight but also greatly improve strength in all sorts of products. Moving forward, we are honing our focus on supporting and expanding success stories like these, particularly as they relate to the commercialization of nanotechnologies. To that end, Dr. Lisa Friedersdorf, NNCO Deputy Director, and I have plans to visit all NSET agencies to talk about their agency’s vision and the NNCO’s vision and to try to establish a plan to more effectively work together to achieve the collective goals of the NNI. We recently visited the NIST Center for Nanoscale Science and Technology, which is truly a world-class facility. This is yet another example of the success of the 21st Century Nanotechnology Research and Development Act and reflects the tangible return on investment from that piece of legislation. So, I think there are a number of examples where nanotechnologies have definitely established a presence in the marketplace, but there is much more that we can do to facilitate the commercialization of nanotechnologies. NanoBCA What is your plan to further impact commercialization? Dr. Meador Success will come from good communications and a focused effort to have NNI agencies work directly with industry to identify and address any roadblocks to commercialization. To that end, the NNCO has initiated a webinar series to highlight problems that industry is facing with regards to nanotech commercialization. This has proven to be a great communications vehicle to provide information, especially to small- and medium- sized business, on topics like insurance and regulations that could help them be more successful in their commercialization efforts. These webinars are scheduled to occur once every other month and are designed to be easily accessible to the broadest audience. NanoBCA One of the challenges that we see regularly at the NanoBCA, is to address the question of whether or not the over $20 billion, that was invested by the 21st Century Nanotechnology Research and Development Act, was worthwhile from a taxpayers’ perspective. Is this a question with which you are confronted? Dr. Meador Yes, this is a very important question that needs to be addressed loudly and clearly and provide a compelling justification for the past and continued investment in the NNI. Fortunately, I have benefitted from sitting on NSET through the critical years and have had a front row seat to witness the impact of this investment. As I mentioned before, there are tangible examples of the return on investment that can be seen in the establishment of new industries and new products which also, not insignificantly, mean new jobs. Also, there has been the establishment of critical new infrastructure, like the NIST Center for Nanoscale Science and Technology. However, it is critically important that the news of these returns be communicated clearly to all stakeholders, which includes the taxpayer, the media and the broader community beyond just those in industry and government who happen to be concerned with nanotechnology as a part of their daily function. That is the challenge that faces us today at NNCO. To address that challenge and to do a better job of communication, NNCO is taking action on several fronts, some of which are quite simple yet very effective. I have already mentioned our webinar series. We are also developing our YouTube channel and reaching out to stakeholders in government and industry to contribute video content that highlights their work. Our goal is to create a buzz about the great potential of nanotechnology commercialization. We are also reaching out directly to students and have established several contests that they can participate in to highlight their research projects (and even art projects). The winners of these contests will be duly recognized at national events. Which brings me to my final point on this matter, which is that we are expanding and improving the quality of our events across the board with the intent of improving the overall impact of our communications. NanoBCA Have you noticed, as we have at NanoBCA, that critics often have misconstrued the literal mandate of the 21st Century Nanotechnology Research and Development Act and perhaps not appreciated that the investment was designed to be on infrastructure and R D, as the name of the Act itself suggests? Dr. Meador Since the inception of the NNI, participating agencies within the Federal government have invested over $20B in nanotechnology related R D. So, I think it is a fair question to ask what the impact of that investment has been on the US economy and job creation. In fact, the President’s Council of Advisors on Science and Technology (“PCAST”) in its last two reviews, and the National Research Council (“NRC”), in its last review, have both called for a clear set of metrics to measure the success of the NNI. We are carefully considering how to develop these metrics by utilizing reports, such as the series of reports over the years by firms such as Lux Research on total revenues generated by nanotech products, as well as other studies which measure the impact of emerging technologies in other ways. Some of the inputs are not just on revenue data, but also on foundational impact such as the establishment of new technologies, sectors and even industries. The bottom line is that we all need to work together to create a better understanding, among the broadest audience possible, of the true impact of nanotechnologies on our society.

Carbon nanotubes show feasibility for practical devices

February 19, 2015 - 4:38am
While carbon nanotubes (CNTs) have long attracted interest for nanoscale electronics, practical deployment of the technology requires a level of device consistency that is still a long way from being achieved. Now researchers at IBM in the US have identified the main source of device variability in CNT transistors and ways of reducing it. In recent years, silicon transistors have been fast approaching their minimum size. Short channel effects and increasing chip power density may halt the trend in constantly decreasing transistor sizes described in 'Moore’s Law'. Fortunately, there is an alternative. "The goal of our research is to develop carbon nanotube transistors into a practical technology that can replace silicon in future generations of high-performance microprocessor chips," says Qing Cao (http://researcher.ibm.com/researcher/view.php?person=us-qcao), who led the IBM research team behind these latest results. Carbon nanotubes have excellent short channel control, a low resistivity between the CNTs and metal contacts, and transport behaviour that allows much lower power consumption for the same on-current density. However where they have fallen short so far is in the uniformity between CNT devices. "Ultimately we want to integrate billions of nanotube transistors into functional circuits," says Cao. "To do this, we need good consistency from one transistor to the next, so they can all work together at the same voltage." Their latest study demonstrates that the device variability does not originate from the nanotubes themselves, and that it may be reduced by improved deposition processes and better materials for the dielectric components.Finding the root of the problem The researchers fabricated hundreds of bottom-gated field-effect transistors, each made from a p-channel single-walled CNT with a 10nm HfO2 layer deposited as the gate dielectric. Systematic experiments with the devices identified the amount of variability from device to device. The measurements also confirmed that variation in carbon nanotube diameter was not a dominant source of variability in device performance. The IBM team then built pairs of devices, where the same nanotube was used as the channel for both transistors. Observations of the performance of device pairs revealed that the dominant source was random, and so likely material-related rather than a systematic process-related contribution. Further analysis indicated that trapped charges fixed at the oxide/air interface were the prime suspect. "I think the results show that it is possible to build practical circuits based on nanotube transistors, but we still need to reduce the variability by several-fold," Cao tells nanotechweb.org. "We have identified the major source as the oxide surface, not anything intrinsic to the nanotubes, so we think we can make it happen with a better fabrication process." He suggests that the variability may be reduced by better control over the nanotube source and the deposition process. "The current nanotube solution isn’t really electronic grade, so we may introduce charges on the oxide during the nanotube deposition process," says Cao. He also suggests that using high quality dielectrics with no free surface near the nanotube may also help. From working to working well Cao describes how far CNT electronics has come in the past few decades. "In the beginning, it was an achievement just to make a few good transistors," he says. The fabrication techniques for these devices are now so advanced that it is possible to fabricate a large enough number of high-quality semiconducting nanotubes to study their random behaviour. He adds, "As it gets closer to becoming a practical technology, the device variability becomes an increasingly important issue." Next the team will work to try and find where the trapped charges come from, and whether they are mainly from dangling bonds at the oxide surface, damage to the oxide during the fabrication process, or residue left by the nanotube solution do that they can eliminate them. Full details are reported in nanotechweb.org (http://nanotechweb.org/cws/article/tech/60243)

Nanotechnology discoveries move from lab to marketplace with CNT fabrication process

February 12, 2015 - 4:50am
A recent agreement between The University of Texas at Dallas and Lintec of America is expected to propel scientific discoveries from the University’s laboratories into the global marketplace and create jobs in North Texas. UT Dallas’ Office of Technology Commercialization (http://www.utdallas.edu/research/otc/) has licensed to Lintec of America a process developed over several years by Dr. Ray Baughman (http://www.utdallas.edu/chairs/profiles/baughman.html), the Robert A. Welch Distinguished Chair in Chemistry, and his colleagues at the University’s Alan G. MacDiarmid NanoTech Institute (http://nanotech.utdallas.edu/about/index.html), which he directs. The patented process transforms tiny tubes of carbon — 10,000 times thinner than the width of a human hair — into useful large-scale structures, such as sheets and yarns, that are super-strong and extremely light. The carbon nanotube materials have unique thermal, mechanical and electrical properties, making them potentially suitable for use in areas such as wearable electronics, electronic displays, solar panels, sound projectors, batteries and harvesters of waste energy. Lintec of America is a subsidiary of Japan-based Lintec Corporation (http://www.lintec-global.com/), a leading manufacturer of pressure-sensitive adhesives. The company’s advanced materials and industrial products are used in items ranging from electronic devices and computer displays to building and automotive materials. Lintec recently opened the Nano-Science Technology Center (http://lintec-nstc.com/) in Richardson. Less than 5 miles from the UT Dallas campus, it is devoted specifically to the manufacture and commercialization of the carbon nanotube structures. Dr. David E. Daniel, president of UT Dallas, said the whole process — from lab to marketplace — exemplifies how research universities impact the economy and society. “One of the important roles a research university plays in the community is to translate the creativity and human talent developed on campus into the private sector,” he said. “This agreement is an example of UT Dallas doing exactly what it should be doing — fostering an ecosystem of hugely creative faculty who educate and train exceptional students, who then contribute significantly to business and add value to society.” Additionally, two UT Dallas alumni are leading efforts at the Nano-Science Technology Center: Dr. Kanzan Inoue MS’01 PhD’05 is managing director of the facility, and his wife, Dr. Raquel Ovalle-Robles MS’06 PhD’08, is the chief research and intellectual properties strategist. Both worked in the NanoTech Institute with Baughman and Dr. Anvar Zakhidov (http://nanotech.utdallas.edu/personnel/staff/zakhidov.html), professor of physics. Inoue said proximity to the University and access to its intellectual resources were primary factors in locating the new facility in Richardson. “The Nano-Science Technology Center was created to bridge the gaps between laboratory research, pilot production and ultimately full production processes,” he said. “Individual carbon nanotubes (CNTs) are much lighter, stronger and more thermally conducting than metals or diamond. However, applying CNTs in practical applications requires scalable and controllable processing methods for assembling them into products without losing the unique properties of individual CNTs.”Inoue also said that a critical factor for the controllable device fabrication is the ability to assemble CNTs in different forms, such as free-standing or on a substrate.“The technology developed at UT Dallas delivers an efficient and elegant solution to these key issues,” he said. “The electrically conducting CNT sheets that we can now make are lighter than air, transparent and much stronger per pound than steel.” Lintec has been an industrial affiliate of the NanoTech Institute for many years, and Baughman said the pairing of the UT Dallas science and technology with the company’s manufacturing capabilities was a natural match. “Lintec has expertise in technologies that will be critically important for economically manufacturing carbon nanotube sheets and converting these sheets into a wide range of products,” said Baughman, a National Academy of Engineering member who joined the UT Dallas faculty in 2001 after a 30-year career in private industry. “They invested in UT Dallas technology because they saw potential for valuable end products and because their manufacturing capabilities are particularly well-suited for upscaling the production of these materials to industrial levels.” Baughman said the licensing agreement will enable “teaming” that eliminates barriers between scientific and technological breakthroughs and products, which is an important goal of the NanoTech Institute. “I’m very happy that Lintec decided to open its new facility in Richardson in order to be close to and work collaboratively with our NanoTech Institute, and that they are creating jobs in Texas,” he said. “I’m also delighted that the leaders of this new business venture are UT Dallas alumni from our institute. I know how brilliant they are and look forward to their accomplishments.” Source: The University of Texas at Dallas (http://www.utdallas.edu/news/2015/2/9-31409_Nanotech-Discoveries-Move-from-Lab-to-Marketplace-_story-wide.html?WT.mc_id=NewsHomepageFeature)

New PEN Inc. Surface Cleaning Product to Redefine Personal Health and Safety

February 6, 2015 - 3:13am
Entry Planned Into $50 Billion Global Cleaning MarketIn direct response to the apparent failure of current cleaners and disinfectants to prevent the spread of illness, PEN Inc. (OTCQB: PENC) is developing a new category of cleaning products intended to clean and fortify surfaces at the nanoscale-level. Unlike traditional harsh pesticide-containing disinfectants, PEN products will incorporate natural elements and sustainable chemistry to keep surfaces safe. The company's aim is to revolutionize the $50 billion global market for industrial and institutional cleaning, which includes lodging, retail outlets, and workplaces. The product is also ideal for the $80 billion global household cleaning market."The news is filled with stories of people being sickened on cruise ship vacations, amusement park visits, and at other public venues," noted Scott E. Rickert, PEN's Chairman, President and CEO. "This PEN product aims to redefine personal health and safety, so consumers can stop worrying about germs and disease every time they touch a restaurant table, airplane armrest, bank ATM machine, or hotel room door." Dr. Rickert added, "Just as important, the patent-pending product will use only safe, sustainable ingredients -- no pesticides or harsh chemicals. In fact the primary ingredient, as listed on the label, is a food additive." Dr. Rickert also addressed the market opportunity. "I expect PEN's first product to expand into a family of products to tackle the problem of safe, healthy surfaces, worldwide. My vision for PEN is to harness the vast potential of nanotechnology to create innovative, breakthrough products for a global marketplace. In PEN we have both the R D expertise and the commercialization experience to begin the process of bringing this product to market." About PEN Inc. (OTCQB: PENC)PEN Inc. (PENC) is a global leader in developing, commercializing and marketing enhanced-performance products enabled by nanotechnology. The company focuses on innovative and advanced product solutions in safety, health and sustainability. For more information about PEN Inc, visit www.pen-technology.com (http://www.pen-technology.com/). Source: PEN Inc. (http://my.mwnewsroom.com/pennewsroom/New-PEN-Inc-Surface-Cleaning-Product-to-Redefine-Personal-Health-and-Safety--11G032156-001)

The Impact of Nanomanufacturing on the Flexible Electronics Opportunity

January 30, 2015 - 10:17am
The National Academy of Engineering report that was just released in 2014 on “The Flexible Electronics Opportunity (http://www.nap.edu/catalog/18812/the-flexible-electronics-opportunity) ” has re-established interest in this growing area which includes strategic opportunities for several future technology platforms, including the Internet of Things, and wearable sensors and systems. The key recommendations are well aligned with strategies, goals and public-private partnerships that have been developing over the past decade. Key recommendations from the report are consistent with the challenges and opportunities that the relevant committees have determined, with the committee recommending the following: The United States should increase funding of basic research related to flexible electronics and augment support for university-based consortia to develop prototypes, manufacturing processes, and products in close collaboration with contributing industrial partners. Consortia, bringing together industry, universities, and various levels of government, should be used as a means of fostering precompetitive applied research in flexible electronics. The United States should establish and support a network of user facilities dedicated to flexible electronics. Where possible, federal efforts to support the growth of competitive flexible electronics industries should leverage state and regional developmental efforts, with the objective of establishing co-located local supply chains and capturing the associated cluster synergies.Agency mission needs should help drive demand for flexible electronics technologies, while lowering costs, improving capabilities, and contributing to the development of a skilled workforce. These recommendations build upon the developments by numerous institutions in establishing industry consortia user facilities to transition the innovations in materials, processes, and integration to industrially meaningful platforms. As such, innovations in nanomaterials and nanomanufacturing processes emerging from NSF Nanoscale Science and Engineering Centers (NSECS) and Nanosystems Engineering Research Centers (NERCs) will play a pivotal role in the innovation cycle to accelerate developments in flexible-hybrid electronics technologies and manufacturing platforms. Complimenting this are the manufacturing demonstration facilities that have been established at various universities as industry user facilities to take advantage of these emerging processes and cutting edge tools that are unavailable elsewhere. Examples include the Center for Advanced Microelectronics Manufacturing (CAMM) at Binghamton University, the Flexible Display Center at Arizona State University, and the Center for Advanced Roll-to-Roll Manufacturing at the University of Massachusetts Amherst. The examples of academic driven public-private partnerships provide leading edge capabilities accessible to industry for acceleration of innovative product development.

'Bulletproof' battery: Kevlar membrane for safer, thinner lithium rechargeables

January 29, 2015 - 9:19am
New battery technology from the University of Michigan should be able to prevent the kind of fires that grounded Boeing 787 Dreamliners in 2013. The innovation is an advanced barrier between the electrodes in a lithium-ion battery. Made with nanofibers extracted from Kevlar, the tough material in bulletproof vests, the barrier stifles the growth of metal tendrils that can become unwanted pathways for electrical current. A U-M team of researchers also founded Ann Arbor-based Elegus Technologies to bring this research from the lab to market. Mass production is expected to begin in the fourth quarter 2016. "Unlike other ultra strong materials such as carbon nanotubes, Kevlar is an insulator," said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering. "This property is perfect for separators that need to prevent shorting between two electrodes."Lithium-ion batteries work by shuttling lithium ions from one electrode to the other. This creates a charge imbalance, and since electrons can't go through the membrane between the electrodes, they go through a circuit instead and do something useful on the way. But if the holes in the membrane are too big, the lithium atoms can build themselves into fern-like structures, called dendrites, which eventually poke through the membrane. If they reach the other electrode, the electrons have a path within the battery, shorting out the circuit. This is how the battery fires on the Boeing 787 are thought to have started. "The fern shape is particularly difficult to stop because of its nanoscale tip," said Siu On Tung, a graduate student in Kotov's lab, as well as chief technology officer at Elegus. "It was very important that the fibers formed smaller pores than the tip size." While the widths of pores in other membranes are a few hundred nanometers, or a few hundred-thousandths of a centimeter, the pores in the membrane developed at U-M are 15-to-20 nanometers across. They are large enough to let individual lithium ions pass, but small enough to block the 20-to-50-nanometer tips of the fern-structures. The researchers made the membrane by layering the fibers on top of each other in thin sheets. This method keeps the chain-like molecules in the plastic stretched out, which is important for good lithium-ion conductivity between the electrodes, Tung said. "The special feature of this material is we can make it very thin, so we can get more energy into the same battery cell size, or we can shrink the cell size," said Dan VanderLey, an engineer who helped found Elegus through U-M's Master of Entrepreneurship program. "We've seen a lot of interest from people looking to make thinner products." Thirty companies have requested samples of the material. Kevlar's heat resistance could also lead to safer batteries as the membrane stands a better chance of surviving a fire than most membranes currently in use. While the team is satisfied with the membrane's ability to block the lithium dendrites, they are currently looking for ways to improve the flow of loose lithium ions so that batteries can charge and release their energy more quickly. The study, "A dendrite-suppressing solid ion conductor from aramid nanofibers," (http://www.nature.com/ncomms/2015/150127/ncomms7152/full/ncomms7152.html) appeared online Jan. 27 in Nature Communications. Source: University of Michigan (http://ns.umich.edu/new/multimedia/slideshows/22645-bulletproof-battery-kevlar-membrane-for-safer-thinner-lithium-rechargeables)

Fully transparent, rollable electronics built with a graphene/carbon nanotube backbone

January 29, 2015 - 9:00am
The coming age of wearable, highly flexible and transparent electronic devices will rely on essentially invisible electronic and optoelectronic circuits. In order to have close to invisible circuitry, one must have optically transparent thin-film transistors (TFTs). In order to have flexibility, one needs bendable substrates. Both flexible electronics and transparent electronics have been demonstrated before, but never rollable electronics that are also fully transparent at the same time. This has now been achieved by a team of researchers in Korea, who have successfully built rollable and transparent electronic devices that are not only lightweight, but also don't break easily. To manufacture flexible electronics, one needs a starting material – the substrate – on which to build-up the device. In order for the final product to be flexible, the substrate of course also has to be flexible. In fact, it is the substrate that determines, to a large extent, the overall flexibility of the final product. So if the substrate is flexible to an extent of being rollable – which can be achieved making it very thin – the final product will also, to some extent, be rollable. Of course, the semiconductors, dielectrics, and metals making up the electronic device, should also be similarly flexible (or soft), otherwise faults will occur. Plastics are the obvious choice for flexible substrates as the substrates are also required to be insulating (nonconductive) in most applications. Other obvious advantages of plastics are that they are lightweight and non-breakable. A team led by Professor Jin Jang, Director of the Department of Information Display (http://display.khu.ac.kr/) at Kyung Hee University, has achieved this by overcoming two major challenges associated with the manufacture of flexible electronics: The temperature restriction of plastic substrates (<100°C) and the difficulty of handling flexible electronics during the fabrication process. They reported their findings in ACS Applied Materials Interfaces ("Fully Transparent and Rollable Electronics" (http://dx.doi.org/doi:10.1021/am506937s)). "To overcome the temperature restriction we chose our plastic substrate to be polyimide (PI), which is a polymer of imide monomers," Jang explains to Nanowerk. "PI has high chemical and heat resistance and when it is colorless, which is the case of this research, it withstands processing temperatures around 300°C." The researchers also chose an amorphous oxide semiconductor – amorphous-indium-gallium-zinc-oxide (a-IGZO) – which assures good device performance even when sputter-deposited at low temperatures. For consistency, they also chose a zinc-based metal, indium-zinc-oxide (IZO), for the metal electrodes – i.e. the gate, source, and drain electrodes of the field-effect transistors making up the electronic devices. "Both the a-IGZO and IZO have large band-gaps, and therefore, are transparent to visible light," says Jang. "As the dielectrics are also transparent and the substrate (PI) is colorless, the final product is see-through with a transmittance of 70% for the full circuit device. The colorless PI (CPI) is 15 µm thick and the thickness of the electronic devices is ∼1 µm, resulting in a total thickness of the fabricated thin-film transistor of only ∼16 µm. Hence, the electronic devices are rollable." In order to deal with the second major challenge – the difficulty of handling flexible electronics during the fabrication process – the researchers used a carrier glass substrate on which the CPI is first spin-coated from solution, and then detached from after device fabrication. Being around 0.7 mm in thickness, the carrier glass is rigid enough to provide mechanical support for the CPI, without which accurate layer registration is impossible during photolithography. This is because standalone plastics substrates can warp, shrink, or bulge at high temperatures. "A rigid carrier substrate is, therefore, a necessity when vacuum processes and photolithography are involved," Jang notes. "However, the way the flexible substrate is attached to the rigid carrier substrate is important as it has to be detached from the carrier substrate after device fabrication. The use of adhesive materials/glues to attach flexible substrates to carrier substrates is not recommended as most adhesives cannot withstand high processing temperatures." An alternative method is to spin-coat the flexible substrate from solution onto the carrier substrate. Although this method avoids the use of adhesive materials, it is very difficult to detach the flexible substrate from the carrier substrate afterwards because bonds between the two have a tendency of strengthening during the fabrication process. "The current solution is to deposit a thin layer such as amorphous-silicon between the flexible substrate and the carrier substrate, which can be evaporated by a laser to release the flexible substrate from the carrier substrate after device fabrication," says Jang. "Given the high cost of installing laser equipment, the complexity of the laser detachment process, and the limitations of the laser beam size, we felt their was a need for a better method." In their research, Jang's team do not use adhesive material or lasers. Neither do they deposit a layer of amorphous-silicon between the carrier glass and the CPI. Instead, they spin coat a mixture of carbon nanotubes (CNT) and graphene oxide (GO) to a thickness of 1 nm from solution onto of the carrier glass before spin coating the CPI. "As the CNT/GO layer has a flake like structure with CNT links, it decreases the area where the CPI contacts the glass, thereby reducing its adhesion to glass," explains Jang. "Inserting the CNT/GO layer also doesn't cost much because only a few drops are required to achieve a thickness around 1 nm." After fabrication, only a small amount of mechanical force is required to detach the CPI from the glass. According to the scientists, the beauty of having the CNT/GO layer is that it bonds stronger with the CPI compared to the glass, such that it remains embedded to the backside of the CPI after detachment – providing mechanical support to the flexible electronics and making the rollable electronics wrinkle-free. Electronic devices built on plastic substrates are prone to electrostatic discharge (ESD) damage because plastics are usually associated with the generation of electrostatic charge. By contrast, the CPI in this present work is ESD-free because localized ESD can be released via the conductive CNT. In their experiments, the team rolled the TFT devices 100 times on a cylinder with radius of 4 mm, without significantly degrading their performance. Integrated circuits also operated without degradation, while being bent to a radius of 2 mm, making these devices suitable for transparent and rollable displays. Source: Nanowerk (http://www.nanowerk.com/spotlight/spotid=38815.php)

Nanowire clothing could keep people warm — without heating everything else

January 29, 2015 - 8:49am
To stay warm when temperatures drop outside, we heat our indoor spaces — even when no one is in them. But scientists have now developed a novel nanowire coating for clothes that can both generate heat and trap the heat from our bodies better than regular clothes. They report on their technology, which could help us reduce our reliance on conventional energy sources, in the ACS journal Nano Letters ("Personal Thermal Management by Metallic Nanowire-Coated Textile" (http://dx.doi.org/doi:10.1021/nl5036572)). Yi Cui and colleagues note that nearly half of global energy consumption goes toward heating buildings and homes. But this comfort comes with a considerable environmental cost – it's responsible for up to a third of the world's total greenhouse gas emissions. Scientists and policymakers have tried to reduce the impact of indoor heating by improving insulation and construction materials to keep fuel-generated warmth inside. Cui's team wanted to take a different approach and focus on people rather than spaces. The researchers developed lightweight, breathable mesh materials that are flexible enough to coat normal clothes. When compared to regular clothing material, the special nanowire cloth trapped body heat far more effectively. Because the coatings are made out of conductive materials, they can also be actively warmed with an electricity source to further crank up the heat. The researchers calculated that their thermal textiles could save about 1,000 kilowatt hours per person every year — that's about how much electricity an average U.S. home consumes in one month. Source: American Chemical Society (http://www.acs.org/content/acs/en/pressroom/presspacs/2015/acs-presspac-january-28-2015/nanowire-clothing-could-keep-people-warm-without-heating-everything-else.html)