National Nanomanufacturing Network

Piezoelectricity in a 2D Semiconductor

National Nanomanufacturing Network - December 23, 2014 - 8:09am
Berkeley Lab Researchers Discovery of Piezoelectricty in Molybdenum Disulfide Holds Promise for Future MEMSA door has been opened to low-power off/on switches in micro-electro-mechanical systems (MEMS) and nanoelectronic devices, as well as ultrasensitive bio-sensors, with the first observation of piezoelectricity in a free standing two-dimensional semiconductor by a team of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab). Xiang Zhang, director of Berkeley Lab’s Materials Sciences Division and an international authority on nanoscale engineering, led a study in which piezoelectricity – the conversion of mechanical energy into electricity or vice versa – was demonstrated in a free standing single layer of molybdenum disulfide, a 2D semiconductor that is a potential successor to silicon for faster electronic devices in the future. “Piezoelectricity is a well-known effect in bulk crystals, but this is the first quantitative measurement of the piezoelectric effect in a single layer of molecules that has intrinsic in-plane dipoles,” Zhang says. “The discovery of piezoelectricity at the molecular level not only is fundamentally interesting, but also could lead to tunable piezo-materials and devices for extremely small force generation and sensing.”Zhang, who holds the Ernest S. Kuh Endowed Chair at the University of California (UC) Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley, is the corresponding author of a paper in Nature Nanotechnology describing this research. The paper is titled “Observation of Piezoelectricity in Free-standing Monolayer MoS2.” The co-lead authors are Hanyu Zhu and Yuan Wang, both members of Zhang’s UC Berkeley research group. (See below for a complete list of co-authors.) Since its discovery in 1880, the piezoelectric effect has found wide application in bulk materials, including actuators, sensors and energy harvesters. There is rising interest in using nanoscale piezoelectric materials to provide the lowest possible power consumption for on/off switches in MEMS and other types of electronic computing systems. However, when material thickness approaches a single molecular layer, the large surface energy can cause piezoelectric structures to be thermodynamically unstable. Over the past couple of years, Zhang and his group have been carrying out detailed studies of molybdenum disulfide, a 2D semiconductor that features high electrical conductance comparable to that of graphene, but, unlike graphene, has natural energy band-gaps, which means its conductance can be switched off. “Transition metal dichalcogenides such as molybdenum disulfide can retain their atomic structures down to the single layer limit without lattice reconstruction, even in ambient conditions,” Zhang says. “Recent calculations predicted the existence of piezoelectricity in these 2D crystals due to their broken inversion symmetry. To test this, we combined a laterally applied electric field with nano-indentation in an atomic force microscope for the measurement of piezoelectrically-generated membrane stress.”Zhang and his group used a free-standing molybdenum disulfide single layer crystal to avoid any substrate effects, such as doping and parasitic charge, in their measurements of the intrinsic piezoelectricity. They recorded a piezoelectric coefficient of 2.9×10-10 C/m, which is comparable to many widely used materials such as zinc oxide and aluminum nitride. “Knowing the piezoelectric coefficient is important for designing atomically thin devices and estimating their performance,” says Nature paper co-lead author Zhu. “The piezoelectric coefficient we found in molybdenum disulfide is sufficient for use in low-power logic switches and biological sensors that are sensitive to molecular mass limits.” Zhang, Zhu and their co-authors also discovered that if several single layers of molybdenum disulfide crystal were stacked on top of one another, piezoelectricity was only present in the odd number of layers (1,3,5, etc.) “This discovery is interesting from a physics perspective since no other material has shown similar layer-number sensitivity,” Zhu says. “The phenomenon might also prove useful for applications in which we want devices consisting of as few as possible material types, where some areas of the device need to be non-piezoelectric.” In addition to logic switches and biological sensors, piezoelectricity in molybdenum disulfide crystals might also find use in the potential new route to quantum computing and ultrafast data-processing called “valleytronics.” In valleytronics, information is encoded in the spin and momentum of an electron moving through a crystal lattice as a wave with energy peaks and valleys. “Some types of valleytronic devices depend on absolute crystal orientation, and piezoelectric anisotropy can be employed to determine this,’ says Nature paper co-lead author Wang. “We are also investigating the possibility of using piezoelectricity to directly control valleytronic properties such as circular dichroism in molybdenum disulfide.” In addition to Zhang, Zhu and Wang, other co-authors of the Nature paper were Jun Xiao, Ming Liu, Shaomin Xiong, Zi Jing Wong, Ziliang Ye, Yu Ye and Xiaobo Yin. This research was supported by Light-Material Interactions in Energy Conversion, an Energy Frontier Research Center (http://www.lmi.caltech.edu/) led by the California Institute of Technology, in which Berkeley Lab is a major partner. The Energy Frontier Research Center program is supported by DOE’s Office of Science.Source: Lawrence Berkeley National Laboratory (http://newscenter.lbl.gov/2014/12/22/piezoelectricity-2d-semiconductor/)

Promising New Method Found for Rapidly Screening Cancer Drugs

National Nanomanufacturing Network - December 17, 2014 - 6:45am
UMass Amherst researchers invent fast, accurate new nanoparticle-based sensor system Traditional genomic, proteomic and other screening methods currently used to characterize drug mechanisms are time-consuming and require special equipment, but now researchers led by chemist Vincent Rotello at the University of Massachusetts Amherst offer a multi-channel sensor method using gold nanoparticles that can accurately profile various anti-cancer drugs and their mechanisms in minutes. As Rotello and his doctoral graduate student Le Ngoc, one of the lead authors, explain, to discover a new drug for any disease, researchers must screen billions of compounds, which can take months. One of the added keys to bringing a new drug to market, they add, is to identify how it works, its chemical mechanism. “Rapid determination of drug mechanism would greatly streamline the drug discovery process, opening the pipeline of new therapeutics,” Ngoc says. She adds, “Drugs with different mechanisms cause changes in the surface of cells that can be read out using the new sensor system. We found that each drug mechanism generated a unique pattern, and we used these cell surface differences to quickly profile different drug mechanisms.” Details of this work appear in the current issue of Nature Nanotechnology. To expedite drug screening, the research team, which in addition to the chemists includes a UMass Amherst cognitive scientist and a materials scientist from Imperial College, London, developed a new, signature-based approach using a gold nanoparticle sensor system and three differently labeled proteins by color: blue, green and red. Using an engineered nanoparticle and three fluorescent proteins provides “a three-channel sensor that can be trained to detect subtle changes in cell surface properties,” the authors note. Drug-induced cell surface changes trigger different sets of fluorescent proteins to turn on together, offering patterns that identify specific cell death mechanisms. The new nanosensor is generalizable to different cell types and does not require processing steps before analysis. So, it offers a simple, effective way to expedite research in drug discovery, toxicology and cell-based sensing, the researchers add. Some signature-based drug screening using traditional biomarkers exists today, but it requires multi-step cell processing and special equipment, limiting its usefulness the authors point out. With their three-channel, gold nanoparticle sensor platform, Rotello and colleagues solve those challenges and enhance accuracy. Further, they say, “the information-rich output allows the determination of a chemotherapeutic mechanism from a single measurement, providing answers far more quickly (in minutes) than current methods, using standard laboratory instrumentation.” This invention could have a substantial potential impact on the drug discovery pipeline, says Ngoc. “The sensor is not only able to profile mechanisms for individual drugs but also determine the mechanisms of drug mixtures, that is, drug ‘cocktails’ that are an emerging tool with many therapies,” she adds. Rotello emphasizes, “While we have decent knowledge of individual drugs, we still have a lot to learn about the mechanisms of combination therapies. In addition to drug screening, the simplicity and speed of this enabling technology holds the promise to greatly accelerate the search for effective cancer treatments, and provides a step forward in areas such as toxicology, where the safety of thousands of uncategorized chemicals needs to be assessed. The researchers point out that their new sensor system offers “a potential way forward for toxicology, providing a viable method to classify the tens of thousands of commercial chemicals for which no data are available."Source: UMass Amherst (http://www.umass.edu/newsoffice/article/promising-new-method-found-rapidly)Image credit: Vincent Rotello, Department of Chemistry, University of Massachusetts-Amherst

Detecting gases wirelessly and cheaply

National Nanomanufacturing Network - December 12, 2014 - 4:28am
New sensor can transmit information on hazardous chemicals or food spoilage to a smartphone.MIT chemists have devised a new way to wirelessly detect hazardous gases and environmental pollutants, using a simple sensor that can be read by a smartphone. These inexpensive sensors could be widely deployed, making it easier to monitor public spaces or detect food spoilage in warehouses. Using this system, the researchers have demonstrated that they can detect gaseous ammonia, hydrogen peroxide, and cyclohexanone, among other gases. “The beauty of these sensors is that they are really cheap. You put them up, they sit there, and then you come around and read them. There’s no wiring involved. There’s no power,” says Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT. “You can get quite imaginative as to what you might want to do with a technology like this.” Swager is the senior author of a paper describing the new sensors in the Proceedings of the National Academy of Sciences the week of Dec. 8. Chemistry graduate student Joseph Azzarelli is the paper’s lead author; other authors are postdoc Katherine Mirica and former MIT postdoc Jens Ravnsbaek. Versatile gas detection For several years, Swager’s lab has been developing gas-detecting sensors based on devices known as chemiresistors, which consist of simple electrical circuits modified so that their resistance changes when exposed to a particular chemical. Measuring that change in resistance reveals whether the target gas is present. Unlike commercially available chemiresistors, the sensors developed in Swager’s lab require almost no energy and can function at ambient temperatures. “This would allow us to put sensors in many different environments or in many different devices,” Swager says. The new sensors are made from modified near-field communication (NFC) tags. These tags, which receive the little power they need from the device reading them, function as wirelessly addressable barcodes and are mainly used for tracking products such as cars or pharmaceuticals as they move through a supply chain, such as in a manufacturing plant or warehouse. NFC tags can be read by any smartphone that has near-field communication capability, which is included in many newer smartphone models. These phones can send out short pulses of magnetic fields at radio frequency (13.56 megahertz), inducing an electric current in the circuit on the tag, which relays information to the phone. To adapt these tags for their own purposes, the MIT team first disrupted the electronic circuit by punching a hole in it. Then, they reconnected the circuit with a linker made of carbon nanotubes that are specialized to detect a particular gas. In this case, the researchers added the carbon nanotubes by “drawing” them onto the tag with a mechanical pencil they first created in 2012 (http://newsoffice.mit.edu/2012/drawing-with-a-carbon-nanotube-pencil-1009), in which the usual pencil lead is replaced with a compressed powder of carbon nanotubes. The team refers to the modified tags as CARDs: chemically actuated resonant devices. When carbon nanotubes bind to the target gas, their ability to conduct electricity changes, which shifts the radio frequencies at which power can be transferred to the device. When a smartphone pings the CARD, the CARD responds only if it can receive sufficient power at the smartphone-transmitted radio frequencies, allowing the phone to determine whether the circuit has been altered and the gas is present. Current versions of the CARDs can each detect only one type of gas, but a phone can read multiple CARDs to get input on many different gases, down to concentrations of parts per million. With the current version of the technology, the phone must be within 5 centimeters of the CARD to get a reading, but Azzarelli is currently working with Bluetooth technology to expand the range. Widespread deployment The researchers have filed for a patent on the sensing technology and are now looking into possible applications. Because these devices are so inexpensive and can be read by smartphones, they could be deployed nearly anywhere: indoors to detect explosives and other harmful gases, or outdoors to monitor environmental pollutants. Once an individual phone gathers data, the information could be uploaded to wireless networks and combined with sensor data from other phones, allowing coverage of very large areas, Swager says. The researchers are also pursuing the possibility of integrating the CARDs into “smart packaging” that would allow people to detect possible food spoilage or contamination of products. Swager’s lab has previously developed sensors (http://newsoffice.mit.edu/2012/fruit-spoilage-sensor-0430) that can detect ethylene, a gas that signals ripeness in fruit. “Avoiding food waste currently is a very hot topic; however, it requires cheap, easy-to-use, and reliable sensors for chemicals, e.g., metabolites such as ammonia that could indicate the quality of raw food or the status of prepared meals,” says Wolfgang Knoll, a managing director of the Austrian Institute of Technology, who was not part of the research team. “The concept presented in this paper could lead to a solution for a long-lasting need in food quality control.” The CARDs could also be incorporated into dosimeters to help monitor worker safety in manufacturing plants by measuring how much gas the workers are exposed to. “Since it’s low-cost, disposable, and can easily interface with a phone, we think it could be the type of device that someone could wear as a badge, and they could ping it when they check in in the morning and then ping it again when they check out at night,” Azzarelli says. The research was funded by the U.S. Army Research Laboratory and the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies; the MIT Deshpande Center for Technological Innovation; and the National Cancer Institute. Source: MIT News Office (http://newsoffice.mit.edu/2014/wireless-chemical-sensor-for-smartphone-1208)

Lawrence Livermore researchers develop efficient method to produce nanoporous metals

National Nanomanufacturing Network - December 12, 2014 - 4:17am
Nanoporous metals — foam-like materials that have some degree of air vacuum in their structure — have a wide range of applications because of their superior qualities. They posses a high surface area for better electron transfer, which can lead to the improved performance of an electrode in an electric double capacitor or battery. Nanoporous metals offer an increased number of available sites for the adsorption of analytes, a highly desirable feature for sensors. Lawrence Livermore National Laboratory (LLNL) and the Swiss Federal Institute of Technology (ETH) researchers have developed a cost-effective and more efficient way to manufacture nanoporous metals over many scales, from nanoscale to macroscale, which is visible to the naked eye. The process begins with a four-inch silicon wafer. A coating of metal is added and sputtered across the wafer. Gold, silver and aluminum were used for this research project. However, the manufacturing process is not limited to these metals. Next, a mixture of two polymers is added to the metal substrate to create patterns, a process known as diblock copolymer lithography (BCP). The pattern is transformed in a single polymer mask with nanometer-size features. Last, a technique known as anisotropic ion beam milling (IBM) is used to etch through the mask to make an array of holes, creating the nanoporous metal. During the fabrication process, the roughness of the metal is continuously examined to ensure that the finished product has good porosity, which is key to creating the unique properties that make nanoporous materials work. The rougher the metal is, the less evenly porous it becomes. “During fabrication, our team achieved 92 percent pore coverage with 99 percent uniformity over a 4-in silicon wafer, which means the metal was smooth and evenly porous,” said Tiziana Bond, an LLNL engineer who is a member of the joint research team. The team has defined a metric — based on a parametrized correlation between BCP pore coverage and metal surface roughness — by which the fabrication of nanoporous metals should be stopped when uneven porosity is the known outcome, saving processing time and costs. “The real breakthrough is that we created a new technique to manufacture nanoporous metals that is cheap and can be done over many scales avoiding the lift-off technique to remove metals, with real-time quality control,” Bond said. “These metals open the application space to areas such as energy harvesting, sensing and electrochemical studies.” The lift-off technique is a method of patterning target materials on the surface of a substrate by using a sacrificial material. One of the biggest problems with this technique is that the metal layer cannot be peeled off uniformly (or at all) at the nanoscale. Other applications of nanoporous metals include supporting the development of new metamaterials (engineered materials) for radiation-enhanced filtering and manipulation, including deep ultraviolet light. These applications are possible because nanoporous materials facilitate anomalous enhancement of transmitted (or reflected) light through the tunneling of surface plasmons, a feature widely usable by light-emitting devices, plasmonic lithography, refractive-index-based sensing and all-optical switching. The other team members include ETH researcher Ali Ozhan Altun and professor Hyung Gyu Park. The team’s findings were reported in an article titled “Manufacturing over many scales: High fidelity macroscale coverage of nanoporous metal arrays via lift-off-free nanofrabication.” (http://onlinelibrary.wiley.com/doi/10.1002/admi.201400084/abstract) It was the cover story in a recent issue of Advanced Materials Interfaces. Source: Lawrence Livermore National Laboratory (https://www.llnl.gov/news/lawrence-livermore-researchers-develop-efficient-method-produce-nanoporous-metals)

3D printed nanostructures made entirely of graphene

National Nanomanufacturing Network - December 12, 2014 - 3:49am
Graphene has received a great deal of attention for its promising potential applications in electronics, biomedical and energy storage devices, sensors and other cutting-edge technological fields, mainly because of its fascinating properties such as an extremely high electron mobility, a good thermal conductivity and a high elasticity.The successful implementation of graphene-based devices invariably requires the precise patterning of graphene sheets at both the micrometer and nanometer scale. Finding the ideal technique to achieve the desired graphene patterning remains a major challenge. 3D printing, also known as additive manufacturing, is becoming a viable alternative to conventional manufacturing processes in an increasing number of applications ranging from children toys to cars, fashion, architecture, military, biomedical science, and aerospace, to name a few. For the first time, researchers have now demonstrated 3D printed nanostructures composed entirely of graphene using a new 3D printing technique. The research team, led by Professor Seung Kwon Seol from Korea Electrotechnology Research Institute (KERI), has published their findings in the November 13, 2014 online edition of Advanced Materials ("3D Printing of Reduced Graphene Oxide Nanowires" (http://dx.doi.org/doi:10.1002/adma.201404380)) "We developed a nanoscale 3D printing approach that exploits a size-controllable liquid meniscus to fabricate 3D reduced graphene oxide (rGO) nanowires," Seol explains. "Different from typical 3D printing approaches which use filaments or powders as printing materials, our method uses the stretched liquid meniscus of ink. This enables us to realize finer printed structures than a nozzle aperture, resulting in the manufacturing of nanotructures." The researchers note that their novel solution-based approach is quite effective in 3D printing of graphene nanostructures as well as in multiple-materials 3D nanoprinting. "We are convinced that this approach will present a new paradigm for implementing 3D patterns in printed electronics," says Seol. For their technique, the team grew graphene oxide (GO) wires at room temperature using the meniscus formed at the tip of a micropipette filled with a colloidal dispersion of GO sheets, then reduced it by thermal or chemical treatment (with hydrazine). The deposition of GO was obtained by pulling the micropipette as the solvent rapidly evaporated, thus enabling the growth of GO wires. The researchers were able to accurately control the radius of the rGO wires by tuning the pulling rate of the pipette; they managed to reach a minimum value of ca. 150 nm. Using this technique, they were able to produce arrays of different freestanding rGO architectures, grown directly at chosen sites and in different directions: straight wires, bridges, suspended junctions, and woven structures. "So far, to the best of our knowledge, nobody has reported 3D printed nanostructures composed entirely of graphene," says Seol. "Several results reported the 3D printing (millimeter- or centimeter-scale) of graphene or carbon nanotube/plastic composite materials by using a conventional 3D printer. In such composite system, the graphene (or CNT) plays an important role for improving the properties of plastic materials currently used in 3D printers. However, the plastic materials used for producing the composite structures deteriorate the intrinsic properties of graphene (or CNT)." He points out that this 3D nanoprinting approach can be used for manufacturing 2D patterns and 3D architectures in diverse devices such as printed circuit boards, transistors, light emitting devices, solar cells, sensors and so on. Reducing the 3D printable size to below 10 nm and increasing the production yield still remain challenges, though. Source: Nanowerk (http://www.nanowerk.com/spotlight/spotid=38253.php)

Inviting articles: Special issue on Nanoinformatics (Beilstein Journal of Nanotechnology)

National Nanomanufacturing Network - December 12, 2014 - 3:16am
The Beilstein Journal of Nanotechnology (BJNANO, http://www.beilstein-journals.org/bjnano (http://www.beilstein-journals.org/bjnano)) invites you to submit papers on any aspect of Nanoinformatics to a Thematic Issue of BJNANO. BJNANO is a High Impact (SCI: 2.3) Open Access journal with No Publication Fees in the broad areas of Nanosciences and Nanotechnology. The BJNANO Thematic issue on Nanoinformatics will include, but are not limited to, the following topics: Data management and database development for nanomaterialsOntology and meta-data design for nanomaterial data Nanomaterial data standards and interoperation/sharing protocols Nanomaterial characterization (i.e., physicochemical/structural properties) Text/Literature mining for nanomaterial data collection and integrationAnalysis/Quantification for nano-images (e.g., TEM images of nanomaterials, images generated from in-vivo high-throughput screening of nano-bioactivity)Assessment of the value of information in nanomaterial dataData mining/Machine learning for nanomaterial data, particularly the development of (quantitative) structure-activity relationships for nanomaterialsSimulation for nanomaterial fate transport, nano-bio interactionsComputing applications for nanomedicine (e.g., drug delivery systems (nano-excipient), diagnosis and prevention, and safe disposal of nanomedicine as household goods)Visualization of nanomaterials dataEnvironmental and health risk assessment, life-cycle analysis, and regulatory decision making for nanomaterialsAssessment of ethical and social issues of nanotechnologyInfrastructure (frameworks/software/tools/resources) for nanoinformatics If you're interested in submitting papers to the thematic issue on Nanoinformtics, the deadline for the submission is: March 31, 2015. Submission instructions can be found at: http://www.beilstein-journals.org/bjnano/submission/submissionOverview.htm (http://www.beilstein-journals.org/bjnano/submission/submissionOverview.htm). When submitting, please also indicate in your cover letter that your paper is submitted for consideration by the thematic issue on Nanoinformatics. For further information regarding the thematic issue on nanoinformatics please contact Dr. Rong Liu (rliu.pro@gmail.com (mailto:rliu.pro@gmail.com)).

Registration Open for 2015 Nanoinformatics Workshop

National Nanomanufacturing Network - December 8, 2014 - 4:31am
Nanoinformatics Workshop: Enabling successful discovery and applications January 26-28, 2015Holiday Inn National Airport Hotel Arlington, VA REGISTER FOR THE WORKSHOP TODAY (https://umass.irisregistration.com/Auth/Authenticate/Index?ReturnUrl=%2fRegister%3fcode%3dNanoinformatics code=Nanoinformatics) Regular attendees: $200, Students: FREE Registration for the Nanoinformatics 2015 workshop (http://nanoinformatics.org/2015/overview) is now available. Registration is open until January 16, 2015, but please note that discounted hotel reservations (http://nanoinformatics.org/2015/venue) have a December 29, 2014 deadline. The purpose of the NanoInfo 2015 workshop is to bring together stakeholders in order to assess the state of informatics relevant to the all aspects of the nanotechnology enterprise and to set priority targets for the future. From materials to processes to products; accessible data, information, models, and simulations will enable innovators to optimize performance and accelerate the innovation cycle from concept to product. Scientists and engineers will be able to efficiently assess the safety of new nanomaterials and quantitatively implement best practices of safe manufacturing and usage of nanomaterials throughout product lifecycles. Scientists will share predictive models and data that enable the design and discovery of nanomaterials and the resulting performance of systems that use them.Workshop Structure and Highlights NanoInfo 2015 will begin with a pre-workshop half-day tutorial, held on Monday, January 26 in the afternoon. The technical sessions will be held from Tuesday January 27 through Wednesday January 28. Accepted abstracts will be assigned to either a formal presentation session or to the poster presentation and discussion session on Tuesday.Workshop Exhibit and Sponsorship OpportunitiesNanoInfo 2015 is accepting sponsorship applications (http://nanoinformatics.org/node/54), offering marketing and workshop participation for those interested in supporting the event. Workshop Call for AbstractsThe NanoInfo 2015 online submission system is now open. Authors wishing to submit an abstract for review may do so by clicking on the 2015 Call for Presentations and Posters link (http://nanoinformatics.org/nidocuments/add). All submissions must be submitted using this online interface, and the deadline for Abstract submissions is December 15, 2014. Important Dates Abstract Submission Deadline December 15, 2014 Notification to Presenters December 17, 2014 Hotel Reservation Deadline December 29, 2014 Registration December - January 16, 2015 NanoInfo 2015 January 26-28, 2015