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  • richardmitnick 1:35 pm on April 5, 2019 Permalink | Reply
    Tags: , Center for Functional Nanomaterials (CFN), GISAXS-grazing-incidence small-angle x-ray scattering, NSLS-II synchrotron, Polymer self-assembly, Samantha Nowak,   

    From Brookhaven National Lab: Women in STEM- “Samantha Nowak: From CFN User to CFN Postdoc” 

    From Brookhaven National Lab

    April 5, 2019
    Ariana Tantillo
    atantillo@bnl.gov

    The chemist first came to Brookhaven Lab in 2017 as a graduate student user of the Center for Functional Nanomaterials (CFN) [below] and has since returned to do postdoctoral research in polymer self-assembly

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    Polymer chemist Samantha Nowak recently joined Brookhaven Lab’s Center for Functional Nanomaterials as a postdoctoral researcher studying polymer self-assembly. Here, she holds silicon wafers containing block copolymer thin films. In front of her is a plasma etch tool, which she uses to remove the domains of one of the “blocks,” or polymers, in the block copolymer. This removal is part of a process that helps Nowak better see the nanoscale self-assembled patterns (using a scanning electron microscope) formed by the block copolymer.

    When Samantha Nowak was growing up, her grandmother would complain about how she could not get her nail polish off. At the time, pure acetone—the solvent that dissolves nail polish—was not widely available. Nowak’s grandfather, a polymer chemist, would bring the “magic” nail polish remover home from his lab, explaining how solubility works. Nowak also vividly remembers her grandfather dropping metal salts into solution as she watched them rapidly crystallize to form interesting structures.

    Despite her interest in science, Nowak was set on being a lawyer up until the end of high school, when her honors chemistry teacher told her about The College of New Jersey’s forensic chemistry program that her daughter was enrolled in.

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    Nowak, a big fan of the television series Law & Order: Special Victims Unit, figured a career in forensic chemistry would allow her to combine her dual interests in science and law. But after declaring chemistry in her first semester at the College of New Jersey, Nowak decided that forensic chemistry was not for her. She decided to continue the general chemistry track, receiving her bachelor’s degree in 2014, with an interdisciplinary concentration in law and society.

    After graduating, Nowak entered a PhD program in chemistry at the University of Maryland (UMD), College Park, where she joined the Sita Research Group and began synthesizing and studying a new class of self-assembling materials called sugar-polyolefin conjugates.

    Self-assembly refers to the ability of certain molecules to spontaneously organize into ordered structures—such as spheres, cylinders, and lamellae (sheets)—as they try to achieve their lowest-energy state.

    “In general, block copolymer self-assembly relies on a chemical incompatibility between two different types of polymers, or “blocks,” linked together by chemical bonds,” explained Nowak. “In my PhD group, we were trying to overcome some of the limitations of block copolymer self-assembly—including the difficulty in obtaining very small feature sizes—by switching out one of the blocks with a sugar. For the other block, we used a low-molecular-weight polyolefin, which is a polymer made out of hydrogen and carbon (hydrocarbon). An extremely high incompatibility exists between the hydrophilic (water-loving) sugar and hydrophobic (water-hating) polyolefin, and the sugar molecule is extremely small with respect to the size of a typical block in a block copolymer. Because of these characteristics, there is a higher mobility that enables the reorganization of the polymer chains into multiple self-assembled structures with incredibly small feature sizes, as small as three nanometers.”

    3
    An illustration of the three-dimensional gyroid structure. This geometric configuration is found in butterfly wings and elsewhere in nature.

    For example, the sugar-polyolefin conjugates can self-assemble into stable “gyroids”—infinitely connecting structures with a minimal surface area containing no straight lines—that are lightweight yet extremely strong. These rare and complex nanostructures would be difficult to obtain and stabilize within traditional block copolymer thin films, especially those as thin as needed for electronic and optical devices. But if scientists can access gyroids and other structures with unique geometries (and thus properties), new applications may be enabled.

    Aligned research themes

    In Nowak’s third year, advisor and principal investigator Lawrence Sita contacted Kevin Yager—group leader of Electronic Nanomaterials at the Center for Functional Nanomaterials (CFN), a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory. Sita thought his group’s research on the sugar-polyolefin conjugates could progress even further with Yager’s expertise and the x-ray scattering capabilities available at Brookhaven Lab’s National Synchrotron Light Source II (NSLS-II) [below], another DOE Office of Science User Facility. At the time, Yager was in the process of developing new equipment and techniques and looking for users for the Complex Materials Scattering (CMS) beamline, which the CFN and NSLS-II operate in partnership.

    “The group’s results were intriguing to me—both because they were able to create very small self-assembled structures, and because their results seemed to violate my expectations for the kinds of structures those materials should form,” said Yager.

    Sita and Nowak wrote and submitted a proposal for beam time at CMS. Their proposal was accepted, and the research Nowak conducted at the beamline ended up becoming a large part of her PhD thesis. In particular, she used a scattering technique called grazing-incidence small-angle x-ray scattering (GISAXS). In GISAXS, a high-energy x-ray beam reflects off of a thin film or substrate at a very shallow angle. The pattern of the scattered x-rays provides information about the size, structure, and orientation of any self-assembled structures within and on the surface.

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    Atomic force microscope images of a sugar-polyolefin conjugate ultrathin film (30 nanometers) at room temperature that the Sita Research Group heated to 140 degrees Fahrenheit for different lengths of time: (a) original ultrathin film, (b) after 14 hours, (c) a zoomed-in region corresponding to the white square in (b), (d) after 24 hours, (e) zoomed-in region corresponding to the white square in (d), and (f) after 48 hours. The images reveal how the morphology evolves in response to heating over time. Source: Journal of the American Chemical Society 2017, 139, 5281–5284.

    “The University of Maryland has a lab-scale x-ray source but we would have never discovered all that we did about the behavior of these materials without the in situ studies at NSLS-II,” said Nowak. “Scans that would have taken an hour in our lab only took 10 seconds at NSLS-II. We were able to visualize in real time how the materials responded to changes in temperature, film thickness, and polymer chain length.”

    The conjugate materials in this case were made out of cellobiose (a sugar derived from cellulose in plants) and polypropylene with a low molecular weight. From their studies, they learned that increasing the temperature caused several different well-ordered morphologies (structural arrangements) with very tiny feature sizes to emerge in both the bulk material and ultrathin films. By jumping to a specific temperature or slowly increasing the temperature, they could control which morphology they ended up with. And if the polymer chain was too long, the structures that formed were more limited in variety.

    “The results were beyond my expectations,” said Yager. “We were able to measure the ordering of Sam’s materials during annealing—that is, watch them during the process of self-organization. Surprisingly, these materials not only organized but also reorganized into a succession of different configurations as we raised the temperature. This behavior would have been hard to see by any other measurement technique.”

    “When the collaboration began, I was just beginning my research project,” said Nowak. “I didn’t know how useful the technique at NSLS-II would be to build upon the work the group had already done with these materials. But once I learned what GISAXS with a synchrotron source could do, it was perfect.”

    From user to postdoc

    During one of her visits to the NSLS-II for beam time, Yager mentioned to Nowak that he was looking for a postdoctoral researcher at the CFN.

    “I was so impressed by Sam’s diligence and scientific insight that I reached out to her when the CFN had the open postdoc position,” said Yager. “I knew she would continue to do great things if she joined our team.”

    Nowak had all intentions of working for industry immediately following graduation, but the combination of her experience as a user and conversation with Yager changed her mind.

    “Kevin explained the differences between the academic postdoc that I was picturing in my head and a postdoc at a place like the CFN,” said Nowak. “I knew that coming here would open a lot of doors for me.”

    Nowak received her PhD in August 2018 and joined the CFN in October.

    “I love it here,” said Nowak. “The research is interesting, and I’m learning so many new techniques and ideas that I would have not otherwise been exposed to. The environment at the CFN is very collaborative, and I get to meet lots of people who are pursuing very different research projects.”

    4
    Samantha Nowak (front row, left) recently joined the Center for Functional Nanomaterials as a postdoctoral researcher in the Electronic Nanomaterials Group, led by Kevin Yager (back row, second from right).

    The perfect blend

    Under the co-advisement of Yager and CFN Director Charles (Chuck) Black, Nowak is studying self-assembly using thin films of well-established polymers (polystyrene (PS) and poly(methyl methacrylate) (PMMA)) to create novel “non-native” morphologies (i.e., those that deviate from the bulk morphologies). Mainly, she is blending block copolymers with different intrinsic morphologies—the morphology they prefer to adopt based on the volume fraction, molecular weight, and surface energy of the respective blocks. For example, one block copolymer may form cylindrical nanostructures and the other lamellae. But when the block copolymers are blended, they adopt morphologies that are completely different than those of the individual components.

    After forming block copolymer thin films by spin casting them from solution onto a flat surface, Nowak heats them on a hot plate. Introducing heat provides energy for the block copolymer film to spontaneously order into patterns with nanoscale features. In order to more easily see the structure of the films, Nowak then converts the PMMA domains into an inorganic replica through sequential infiltration synthesis—a chemical method in which a polymer is infused with an inorganic material by exposure to gaseous metal precursors in multiple cycles—and etches away the polymer with oxygen plasma.

    “With this approach, I have better contrast when I look at the films in the scanning electron microscope,” said Nowak.

    Most recently, Nowak has been seeing what happens when she changes the composition of the block copolymer blend. One unexpected result so far was the formation of hexagonally perforated lamellae from cylinder and lamellae block copolymers.

    “This morphology is not very common and is difficult to obtain,” explained Nowak. “There’s a very narrow region of the phase diagram where it is stable, so the fact that we expanded accessibility to this phase is very exciting.”

    In another experiment, Nowak used the same exact blend of block copolymers but changed the surface energy. The result was either a single nanostructure or a combination of line and dot patterns, hexagonally perforated lamellae, and horizontal lamellae. Nowak is also exploring how to chemically pattern substrates as a way to “program” which morphologies appear in particular regions of the substrate. She is in the process of getting training in the cleanroom of the CFN Nanofabrication Facility to perform this patterning.

    “We’re creating new nanostructures from already existing materials,” explained Nowak. “We don’t have to synthesize new types of block copolymers; we can use two easily obtainable ones and broaden what we can do with them.”

    The combination of different nanostructures within a single substrate in a predetermined fashion could expand the range of applications—something that Nowak had not previously thought much about.

    5
    Conventionally, block copolymers self-assemble into a limited range of morphologies, such as spheres and lamellae. But by using appropriate block copolymer blends and a chemically patterned substrate that contains the “instructions” for which morphologies appear where, scientists can significantly expand this range. Nowak, Yager, and other CFN scientists recently obtained four different nanostructures—dots, lines, horizontal lamellae, and hexagonally perforated lamellae—in predetermined regions of a single substrate.

    “As a chemist, I tend to focus on the very specific details of the research,” said Nowak. “That is where my brain is trained to stop. But, Chuck—who I meet with every other week to discuss my research and goals—has helped me broaden my viewpoint. He has me consider how we could use these nanostructures in different ways, how we can benefit society with them. I’ve always been interested in the fundamental science part, but now I’m retraining my mind to see the bigger picture. I’ll need to be able to look beyond my individual research projects for a career in industry.”

    After her postdoc, Nowak plans to enter industry as a polymer chemist. She has not yet decided which industry, but she is currently considering cosmetics or consumer goods.

    “One of my grandfather’s inventions was a way to stabilize color in paints and coatings,” said Nowak. “Before his invention, paint darkened or discolored exponentially faster than paints today. Now almost all paints today have this stabilizer in it. It would be great to follow in my grandfather’s footsteps.”

    See the full article here .


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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 6:02 pm on November 21, 2017 Permalink | Reply
    Tags: , , , Center for Functional Nanomaterials (CFN), , , , , Plasma-facing material   

    From BNL: “Designing New Metal Alloys Using Engineered Nanostructures” 

    Brookhaven Lab

    Stony Brook University assistant professor Jason Trelewicz brings his research to design and stabilize nanostructures in metals to Brookhaven Lab’s Center for Functional Nanomaterials.

    1
    Materials scientist Jason Trelewicz in an electron microscopy laboratory at Brookhaven’s Center for Functional Nanomaterials, where he characterizes nanoscale structures in metals mixed with other elements.

    Materials science is a field that Jason Trelewicz has been interested in since he was a young child, when his father—an engineer—would bring him to work. In the materials lab at his father’s workplace, Trelewicz would use optical microscopes to zoom in on material surfaces, intrigued by all the distinct features he would see as light interacted with different samples.

    Now, Trelewicz—an assistant professor in the College of Engineering and Applied Sciences’ Department of Materials Science and Chemical Engineering with a joint appointment in the Institute for Advanced Computational Science at Stony Brook University and principal investigator of the Engineered Metallic Nanostructures Laboratory—takes advantage of the much higher magnifications of electron microscopes to see tiny nanostructures in fine detail and learn what happens when they are exposed to heat, radiation, and mechanical forces. In particular, Trelewicz is interested in nanostructured metal alloys (metals mixed with other elements) that incorporate nanometer-sized features into classical materials to enhance their performance. The information collected from electron microscopy studies helps him understand interactions between structural and chemical features at the nanoscale. This understanding can then be employed to tune the properties of materials for use in everything from aerospace and automotive components to consumer electronics and nuclear reactors.

    Since 2012, when he arrived at Stony Brook University, Trelewicz has been using the electron microscopes and the high-performance computing (HPC) cluster at the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory—to perform his research.

    “At the time, I was looking for ways to apply my idea of stabilizing nanostructures in metals to an application-oriented problem,” said Trelewicz. “I’ve long been interested in nuclear energy technologies, initially reading about fusion in grade school. The idea of recreating the processes responsible for the energy we receive from the sun here on earth was captivating, and fueled my interest in nuclear energy throughout my entire academic career. Though we are still very far away from a fusion reactor that generates power, a large international team on a project under construction in France called ITER is working to demonstrate a prolonged fusion reaction at a large scale.”

    Plasma-facing materials for fusion reactors

    Nuclear fusion—the reaction in which atomic nuclei collide—could provide a nearly unlimited supply of safe, clean energy, like that naturally produced by the sun through fusing hydrogen nuclei into helium atoms. Harnessing this carbon-free energy in reactors requires generating and sustaining a plasma, an ionized gas, at the very high temperatures at which fusion occurs (about six times hotter than the sun’s core) while confining it using magnetic fields. Of the many challenges currently facing fusion reactor demonstrations, one of particular interest to Trelewicz is creating viable materials to build a reactor.

    2
    A model of the ITER tokamak, an experimental machine designed to harness the energy of fusion. A powerful magnetic field is used to confine the plasma, which is held in a doughnut-shaped vessel. Credit: ITER Organization.

    “The formidable materials challenges for fusion are where I saw an opportunity for my research—developing materials that can survive inside the fusion reactor, where the plasma will generate high heat fluxes, high thermal stresses, and high particle and neutron fluxes,” said Trelewicz. “The operational conditions in this environment are among the harshest in which one could expect a material to function.”

    A primary candidate for such “plasma-facing material” is tungsten, because of its high melting point—the highest one among metals in pure form—and low sputtering yield (number of atoms ejected by energetic ions from the plasma). However, tungsten’s stability against recrystallization, oxidation resistance, long-term radiation tolerance, and mechanical performance are problematic.

    Trelewicz thinks that designing tungsten alloys with precisely tailored nanostructures could be a way to overcome these problems. In August, he received a $750,000 five-year award from the DOE’s Early Career Research Program to develop stable nanocrystalline tungsten alloys that can withstand the demanding environment of a fusion reactor. His research is combining simulations that model atomic interactions and experiments involving real-time ion irradiation exposure and mechanical testing to understand the fundamental mechanisms responsible for the alloys’ thermal stability, radiation tolerance and mechanical performance. The insights from this research will inform the design of more resilient alloys for fusion applications.

    In addition to the computational resources they use at their home institution, Trelewicz and his lab group are using the HPC cluster at the CFN—and those at other DOE facilities, such as Titan at Oak Ridge Leadership Computing Facility (a DOE Office of Science User Facility at Oak Ridge National Laboratory)—to conduct large-scale atomistic simulations as part of the project.

    ORNL Cray Titan XK7 Supercomputer

    “The length scales of the structures we want to design into our materials are on the order of a few nanometers to 100 nanometers, and a single simulation can involve up to 10 million atoms,” said Trelewicz. “Using HPC clusters, we can build a system atom-by-atom, representative of the structure we would like to explore experimentally, and run simulations to study the response of that system under various external stimuli. For example, we can fire a high-energy atom into the system and watch what happens to the material and how it evolves, hundreds or thousands of times. Once damage has accumulated in the structure, we can simulate thermal and mechanical forces to understand how defect structure impacts other behavior.”

    These simulations inform the structures and chemistries of experimental alloys, which Trelewicz and his students fabricate at Stony Brook University through high-energy milling. To characterize the nanoscale structure and chemical distribution of the engineered alloys, they extensively use the microscopy facilities at the CFN—including scanning electron microscopes, transmission electron microscopes, and scanning transmission electron microscopes. Imaging is conducted at high resolution and often combined with heating within the microscope to examine in real time how the structures evolve with temperature. Experiments are also conducted at other DOE national labs, such as Sandia through collaboration with materials scientist Khalid Hattar of the Ion Beam Laboratory. Here, students in Trelewicz’s research group simultaneously irradiate the engineered alloys with an ion beam and image them with an electron microscope over the course of many days.

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    Trelewicz and his students irradiated a nanostructured tungsten-titanium alloy with high-energy gold ions to explore the radiation tolerance of this novel material.

    “Though this damage does not compare to what the material would experience in a reactor, it provides a starting point to evaluate whether or not the engineered material could indeed address some of the limitations of tungsten for fusion applications,” said Trelewicz.

    Electron microscopy at the CFN has played a key role in an exciting discovery that Trelewicz’s students recently made: an unexpected metastable-to-stable phase transition in thin films of nanostructured tungsten. This phase transition drives an abnormal “grain” growth process in which some crystalline nanostructure features grow very dramatically at the expense of others. When the students added chromium and titanium to tungsten, this metastable phase was completely eliminated, in turn enhancing the thermal stability of the material.

    “One of the great aspects of having both experimental and computational components to our research is that when we learn new things from our experiments, we can go back and tailor the simulations to more accurately reflect the actual materials,” said Trelewicz.

    Other projects in Trelewicz’s research group.

    The research with tungsten is only one of many projects ongoing in the Engineered Metallic Nanostructures Laboratory.

    “All of our projects fall under the umbrella of developing new metal alloys with enhanced and/or multifunctional properties,” said Trelewicz. “We are looking at different strategies to optimize material performance by collectively tailoring chemistry and microstructure in our materials. Much of the science lies in understanding the nanoscale mechanisms that govern the properties we measure at the macroscale.”

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    Jason Trelewicz (left) with Olivia Donaldson, who recently graduated with her PhD from Trelewicz’s group, and Jonathan Gentile, a current doctoral student, in front of the scanning electron microscope/focused-ion beam at Stony Brook University’s Advanced Energy Center. Credit: Stony Brook University.

    Through a National Science Foundation CAREER (Faculty Early Career Development Program) award, Trelewicz and his research group are exploring another class of high-strength alloys—amorphous metals, or “metallic glasses,” which are metals that have a disordered atomic structure akin to glass. Compared to everyday metals, metallic glasses are often inherently higher strength but usually very brittle, and it is difficult to make them in large parts such as bulk sheets. Trelewicz’s team is designing interfaces and engineering them into the metallic glasses—initially iron-based and later zirconium-based ones—to enhance the toughness of the materials, and exploring additive manufacturing processes to enable sheet-metal production. They will use the Nanofabrication Facility at the CFN to fabricate thin films of these interface-engineered metallic glasses for in situ analysis using electron microscopy techniques.

    In a similar project, they are seeking to understand how introducing a crystalline phase into a zirconium-based amorphous alloy to form a metallic glass matrix composite (composed of both amorphous and crystalline phases) augments the deformation process relative to that of regular metallic glasses. Metallic glasses usually fail catastrophically because strain becomes localized into shear bands. Introducing crystalline regions in the metallic glasses could inhibit the process by which strain localizes in the material. They have already demonstrated that the presence of the crystalline phase fundamentally alters the mechanism through which the shear bands form.

    Trelewicz and his group are also exploring the deformation behavior of metallic “nanolaminates” that consist of alternating crystalline and amorphous layers, and are trying to approach the theoretical limit of strength in lightweight aluminum alloys through synergistic chemical doping strategies (adding other elements to a material to change its properties).

    5
    Trelewicz and his students perform large-scale atomistic simulations to explore the segregation of solute species to grain boundaries (GBs)—interfaces between grains—in nanostructured alloys, as shown here for an aluminum-magnesium (Al-Mg) system, and its implications for the governing deformation mechanisms. They are using the insights gained through these simulations to design lightweight alloys with theoretical strengths.

    “We leverage resources of the CFN for every project ongoing in my research group,” said Trelewicz. “We extensively use the electron microscopy facilities to look at material micro- and nanostructure, very often at how interfaces are coupled with compositional inhomogeneities—information that helps us stabilize and design interfacial networks in nanostructured metal alloys. Computational modeling and simulation enabled by the HPC clusters at the CFN informs what we do in our experiments.”

    Beyond his work at CFN, Trelewicz collaborates with his departmental colleagues to characterize materials at the National Synchrotron Light Source II—another DOE Office of Science User Facility at Brookhaven.

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    BNL NSLS II

    “There are various ways to characterize structural and chemical inhomogeneities,” said Trelewicz. “We look at small amounts of material through the electron microscopes at CFN and on more of a bulk level at NSLS-II through techniques such as x-ray diffraction and the micro/nano probe. We combine this local and global information to thoroughly characterize a material and use this information to optimize its properties.”

    Future of next-generation materials

    When he is not doing research, Trelewicz is typically busy with student outreach. He connects with the technology departments at various schools, providing them with materials engineering design projects. The students not only participate in the engineering aspects of materials design but are also trained on how to use 3D printers and other tools that are critical in today’s society to manufacture products more cost effectively and with better performance.

    Going forward, Trelewicz would like to expand his collaborations at the CFN and help establish his research in metallic nanostructures as a core area supported by CFN and, ultimately, DOE, to achieve unprecedented properties in classical materials.

    “Being able to learn something new every day, using that knowledge to have an impact on society, and seeing my students fill gaps in our current understanding are what make my career as a professor so rewarding,” said Trelewicz. “With the resources of Stony Brook University, nearby CFN, and other DOE labs, I have an amazing platform to make contributions to the field of materials science and metallurgy.”

    Trelewicz holds a bachelor’s degree in engineering science from Stony Brook University and a doctorate in materials science and engineering with a concentration in technology innovation from MIT. Before returning to academia in 2012, Trelewicz spent four years in industry managing technology development and transition of harsh-environment sensors produced by additive manufacturing processes. He is the recipient of a 2017 Department of Energy Early Career Research Award, 2016 National Science Foundation CAREER award, and 2015 Young Leaders Professional Development Award from The Minerals, Metals & Materials Society (TMS), and is an active member of several professional organizations, including TMS, the Materials Research Society, and ASM International (the Materials Information Society).

    See the full article here .

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  • richardmitnick 3:08 pm on January 3, 2017 Permalink | Reply
    Tags: , , Center for Functional Nanomaterials (CFN), Nanoscale 'Conversations' Create Complex and Multi-Layered Structures,   

    From BNL: “Nanoscale ‘Conversations’ Create Complex, Multi-Layered Structures” 

    Brookhaven Lab

    December 22, 2016
    Justin Eure

    1
    Study co-authors Pawel Majewski and Kevin Yager preparing nanoscale films of self-assembling materials.

    Building nanomaterials with features spanning just billionths of a meter requires extraordinary precision. Scaling up that construction while increasing complexity presents a significant hurdle to the widespread use of such nano-engineered materials.

    Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have developed a way to efficiently create scalable, multilayer, multi-patterned nanoscale structures with unprecedented complexity.

    The Brookhaven team exploited self-assembly, where materials spontaneous snap together to form the desired structure. But they introduced a significant leap in material intelligence, because each self-assembled layer now guides the configuration of additional layers.

    The results, published in the journal Nature Communications, offer a new paradigm for nanoscale self-assembly, potentially advancing nanotechnology used for medicine, energy generation, and other applications.

    “There’s something amazing and rewarding about creating structures no one has ever seen before,” said study coauthor Kevin Yager, a scientist at Brookhaven Lab’s Center for Functional Nanomaterials (CFN). “We’re calling this responsive layering—like building a tower, but where each brick is intelligent and contains instructions for subsequent bricks.”

    The technique was pioneered entirely at the CFN, a DOE Office of Science User Facility.

    “The trick was chemically ‘sealing’ each layer to make it robust enough that the additional layers don’t disrupt it,” said lead author Atikur Rahman, a Brookhaven Lab postdoc during the study and now an assistant professor at the Indian Institute of Science Education and Research, Pune. “This granted us unprecedented control. We can now stack any sequence of self-organized layers to create increasingly intricate 3D structures.”

    Guiding nanoscale conversations

    2
    The added color in this scanning electron microscope (SEM) image showcases the discrete, self-assembled layers within these novel nanostructures. The pale blue bars are each roughly 4,000 times thinner than a single human hair. No image credit.

    Other nano-fabrication methods—such as lithography—can create precise nano-structures, but the spontaneous ordering of self-assembly makes it faster and easier. Further, responsive layering pushes that efficiency in new directions, enabling, for example, structures with internal channels or pockets that would be exceedingly difficult to make by any other means.

    “Self-assembly is inexpensive and scalable because it’s driven by intrinsic interactions,” said study coauthor and CFN scientist Gregory Doerk. “We avoid the complex tools that are traditionally used to carve precise nano-structures.”

    The CFN collaboration used thin films of block copolymers (BCP)—chains of two distinct molecules linked together. Through well-established techniques, the scientists spread BCP films across a substrate, applied heat, and watched the material self-assemble into a prescribed configuration. Imagine spreading LEGOs over a baking sheet, sticking it in the oven, and then seeing it emerge with each piece elegantly snapped together in perfect order.

    However, these materials are conventionally two-dimensional, and simply stacking them would yield a disordered mess. So the Brookhaven Lab scientists developed a way to have self-assembled layers discretely “talk” to one another.

    The team infused each layer with a vapor of inorganic molecules to seal the structure—a bit like applying nanoscale shellac to preserve a just-assembled puzzle.

    “We tuned the vapor infiltration step so that each layer’s structure exhibits controlled surface contours,” Rahman said. “Subsequent layers then feel and respond to this subtle topography.”

    Coauthor Pawel Majewski added, “Essentially, we open up a ‘conversation’ between layers. The surface patterns drive a kind of topographic crosstalk, and each layer acts as a template for the next one.”

    Exotic configurations

    4
    An aerial view of a complete, self-assembled, multilayer nanostructure. In this instance, parallel bars of block copolymers with varying thickness were criss-crossed. No image credit.

    As often occurs in fundamental research, this crosstalk was an unexpected phenomenon.

    “We were amazed when we first saw templated ordering from one layer to the next, Rahman said. “We knew immediately that we had to exhaustively test all the possible combinations of film layers and explore the technique’s potential.”

    The collaboration demonstrated the formation of a broad range of nano-structures—including many configurations never before observed. Some contained hollow chambers, round pegs, rods, and winding shapes.

    “This was really a Herculean effort on the part of Atikur,” Yager said. “The multi-layer samples covered a staggering range of combinations.”

    Mapping never-before-seen structures

    5
    This image shows the range of multilayer morphologies achieved through this new technique. The first column shows a cross section of the novel 3D nanostructures as captured by scanning electron microscopy (SEM). The computer renderings in the second column highlight the integrity and diversity of each distinct layer, while the overhead SEM view of the third column reveals the complex patterns achieved through the “intelligent” layering. No image credit.

    See the full article here .

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