Multiscale Modeling of Liquid-Like Phase-Separated Chromatin in the Cell Nucleus, Dr. Rabia Laghmach, Department of Chemistry, Iowa State University, Ames Iowa

Eukaryotic nucleus confines nearly two-meter-long polymeric chromatin folding chains within its micron-sized membrane bounds while remaining dynamic and accessible for gene regulation machinery. The nucleus is compartmentalized through microphase separation of epigenetically decorated chromatin types into transcriptionally active euchromatin and silent heterochromatin compartments. The spatial arrangement of chromatin compartments is cell type-specific, which evolves along the lifetime of the cell. The three-dimensional structures of chromatin organization play an important role in regulating cellular function, and its disruption leads to diseases. Investigating the principles underlying the genome architecture and its dynamics could pave the way to identifying the relationship between chromatin structures, gene expression, and gene-regulatory machinery. The chromatin capture and imaging techniques have revealed a much more dynamic and stochastic nature of chromatin structures, which is reminiscent of multiphase fluid behavior. A natural question that emerges from the experimental observations is how much of large-scale chromatin ordering and dynamics could be explained away just by the liquid-like phase separation of chromatin. In this talk, I will present recent results on mesoscale nuclear dynamics of chromatin phase separation based on our developed multiphase liquid model of the nucleus called MELON-4D, which can resolve nuclear geometry, chromosomal territories, compartments, and nuclear lamina. The model enables rapid hypothesis-driven prototyping of nuclear dynamics in 4D, which facilitates comparison with whole nucleus imaging experiments. As an application, we model the Drosophila nucleus spanning the interphase and map phase diagram of nuclear morphologies. We shed light on the interplay of adhesive and cohesive interactions within the nucleus, giving rise to distinct radial organization seen in conventional, inverted, and senescent nuclear architectures. 

For more information, contact Erik Hobbie, erik.hobbie@ndsu.edu

Self-fitting, Shape Memory Polymer Scaffolds for Bone Defect Repair, Dr. Melissa A. Grunlan, Department of Biomedical Engineering, Texas A&M University, College Station Texas

Shape memory polymer (SMP) scaffolds were prepared having the capacity to conformally “self-fit” into and heal irregular bone defects. Initially, porous scaffolds were fabricated via photo-crosslinking of linear-poly(ε-caprolactone) (PCL) diacrylate using a solvent casting/particulate leaching (SCPL) method employing a fused salt template. Following exposure to warm saline at T > T_trans (T_trans = ~T_m of PCL), the scaffold became malleable and could be pressed into an irregular model defect. Subsequent cooling caused the scaffold to lock in its temporary shape within the defect. In this this talk, strategies to create a tissue-safe fitting temperature, accelerate the rate of degradation, and to enhance bioactivity will be discussed. These approaches include the use of a star PCL architecture, a semi-interpenetrating polymer (semi-IPN) design that incorporates poly(L-lactic acid) (PLLA), and the addition of Bioglass to form composites.

For more information, contact Dean Webster, Dean.Webster@ndsu.edu

Surface Polymerization: A Versatile Tool to Enable Novel Insights and Functionality in Colloidal Materials, Dr. Michael R. Bockstaller, Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh Pennsylvania

Surface Initiated Atom Transfer Radical Polymerization (SI- ATRP) in its various modifications has emerged as a versatile toolbox to control and tailor the properties and interactions of interfaces and to enable the synthesis of brush particle-based hybrid materials with unprecedented property combinations. The resulting materials have attracted interest because the high-level structural control of the architecture of polymer-tethered particles enables tailoring of the interactions, microstructure and properties of brush particle-based materials.

This contribution will present our recent progress to understand the effect of brush modification on the interactions between colloidal particles and applications of brush particle-based materials for the fabrication of functional materials. Surface-initiated atom transfer radical polymerization was used to synthesize a library of homo and gradient co-polymer brush particle systems, with varying molecular weight dispersity. In a first part of the presentation, the effect of brush architecture (particle size, grafting density, degree of polymerization and disparity) on small and large strain deformation will be presented and guidelines for the synthesis of one-component composites with maximum inorganic content and strength will be established. In a second part, the phase behavior and transformation in binary brush particle systems will be discussed. Recent neutron scattering data will be shown to reveal a unique phase separation kinetics that has not previously been observed in polymeric systems. Finally, it will be demonstrated how insights on interactions between brush particles can be harnessed for the design of copolymer-modified one-component hybrid materials with enhanced self-healing capability.

For more information, contact Mohi Quadir, mohiuddin.quadir@ndsu.edu

Understanding Interfacial Perturbations to the Glass Transition from Grafted and Surface Bound Chains, Dr. Connie B. Roth, Department of Physics, Emory University, Atlanta Georgia

Surface bound chains such as grafted and adsorbed polymers are widely used for modifying interfacial interactions in polymer materials and nanocomposites.  However, the underlying mechanisms by which changes to the material properties are conferred to the system are not well understood.  To isolate the physics behind local property changes, we focus on a single interface and use localized fluorescence to probe how end-grafted chains increase the local glass transition temperature Tg(z) next to an interface with varying grafting density, tethered chain length, and end functional group.  We also begin to address the more complicated system of adsorbed chains where non-specific interactions adhere polymer chains to surfaces forming “bound layers”.  This work builds on our group's recent work that demonstrated a local Tg(z) increase of 50 K in polystyrene (PS) matrices with PS end-grafted chains at low grafting densities [Huang, Roth, ACS Macro Letters 2018, 7, 269].  Possible underlying physical mechanisms for this behavior will be discussed.

For more information, contact Alexander Wagner,alexander.wagner@ndsu.edu

Quantifying Stresses in Polymer Composites via Mechanophores, Dr. Chelsea S. Davis, School of Materials Engineering, Purdue University, West Lafayette, Indiana

Many properties of polymeric systems are determined almost exclusively by the interfaces between various material components. The research in the Illuminating Interfacial Mechanics Lab focuses on the development of novel measurement tools to assess the micromechanical behavior of polymer surfaces and interfaces while observing the resulting deformation with various microscopy techniques. Following a brief introduction of the lab and our capabilities, this seminar will focus on the role of interfacial strength on the stress field developed in the matrix of a glass/polymer composite. Here, we utilize a mechanically-activated fluorescent dye molecule (referred to as a mechanophore, MP) to visualize stress gradients around a rigid inclusion upon mechanical deformation. By coupling our experimental observations of mechanophore activation with finite element analysis of the various stress states that develop in the loaded composites, a novel approach to quantitatively calibrate the MP fluorescent activation intensity has been established. We then apply our calibration to several test cases of silica/silicone composites with dramatically different levels of interfacial strength and geometries. This mechanophore/mechanical deformation approach enables stress fields to be observed in a powerful new way via fluorescence imaging in a mechanically loaded polymer composite.

For more information, contact Wenjie Xia, (701) 231-5648, wenjie.xia@ndsu.edu

Programming Liquid-Liquid Phase Separation of Polymeric and Polypeptide Solutions, Dr. Nick Carroll, Department of Chemical Engineering, University of New Mexico, Albuquerque, NM

Aqueous multi-phase systems comprising immiscible biopolymer solutions are ubiquitous in biological cells. However, the structure-to-function relationship and the physics describing the behavior of these polymer systems are, in general, not well understood. For example, almost all proteins have a specific three-dimensional structure that maintains its specific activity in the cell. One class of phase separating proteins, which has flown under the radar for decades, do not. They are referred to as intrinsically disordered proteins (IDPs). Their role in the cell appears to be to spontaneously associate with other proteins and nucleic acids in phase separated compartments to activate them collectively. This is an important function to include in the design of a synthetic cell and for integration with cellular regulatory systems. Our work explores how we can leverage polymer physics combined with the blueprint provided by the cell to engineer biological systems comprising phase-separated liquids with applications spanning areas of tissue culture, gene delivery, microfluidic colloid synthesis and engineered synthetic cells. Potential advancements include understanding how these interactions affect the regulation of gene expression and cell metabolism, understanding how dysfunctional interactions are linked to neurodegenerative disorders, and the design of synthetic cellular systems to create membraneless organelles to control a variety of biological processes at the molecular level.

For Zoom link information, contact erik.hobbie@ndsu.edu

Using Processing Strategies to Engineer Structure and Mechanical Performance in Polymers, Nanocomposites, and Fiber Networks, Dr. Meisha L. Shofner, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA

The structure of polymeric materials is inherently multiscale, with length scales ranging from the molecular level up to the bulk. This structural complexity offers a rich area for producing structures with polymers and their composites that are present in nature, art, and human imagination. In the Shofner group, we are investigating how to realize some of these structures by using processing strategies that build the needed physical features. In this seminar, I will discuss three topics in our work that are included in this theme: constructing tensegrity-inspired structures, imparting auxetic behavior, and constructing charge-driven nanofiber assemblies in polymer-based materials. For tensegrity-inspired structures, we are mapping the concepts of tensegrity to the components in a polymer nanocomposite to produce microstructures with improved stiffness relative to other available microstructures. In this mapping, the nanoparticles are considered as the compressive elements and the polymer matrix serves as the tensioned web. For auxetic structures, we are achieving a large auxetic response in fiber networks in the form of bonded mats as well as physically entangled structures. These networks are produced at large scale as non-woven fabrics, providing opportunities to produce “commodity” auxetics. For nanofiber assemblies in polymer matrices, we are combining oppositely charged bio-based nanofibers, cellulose nanocrystals and chitin nanofibers, in composite films and hydrogels and exploring when these combinations can be beneficial to mechanical properties. The results indicate that at certain ratios the nanofibers can produce blended structures that improve interfacial interactions and load transfer.  Overall, the results of these studies provide pathways for achieving additional materials design options for polymers and composites that can be integrated with current processing/manufacturing methods.

For more information (and Zoom link), contact Erik Hobbie, (701) 231-6103, erik.hobbie@ndsu.edu

Novel Ice-Shedding Surfaces, Dr. Anish Tuteja, Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI

Ice accretion has a negative impact on critical infrastructure, as well as a range of commercial and residential activities. Icephobic surfaces are defined by an ice adhesion strength t_ice < 100 kPa. However, the passive removal of ice requires much lower values of t_ice, such as on airplane wings or power lines (t_ice  < 20 kPa). Such low t_ice values are scarcely reported, and robust coatings that maintain these low values have not been reported previously. In the first part of the talk, I will discuss how, irrespective of material chemistry, by tailoring the crosslink density of different elastomeric coatings, and by enabling interfacial slippage, it is possible to systematically design coatings with extremely low ice-adhesion (t_ice  < 0.2 kPa). By utilizing these mechanisms, we fabricate extremely durable coatings that maintain t_ice  < 10 kPa after severe mechanical abrasion, acid/base exposure, 100 icing/de-icing cycles, thermal cycling, accelerated corrosion, and exposure to Michigan wintery conditions over several months.

In the second portion of the talk, I will discuss how the force required to remove ice from a surface is typically considered to scale with the iced area. This imparts a scalability limit to the use of icephobic coatings for structures with large surface areas, such as power lines or ship hulls. I will then describe a class of materials that exhibit a low interfacial toughness with ice, resulting in systems for which the forces required to remove large areas of ice (few cm2 or greater) are both low and independent of the iced area. Coatings made of such materials allow ice to be shed readily from large areas (~1m²) merely by self-weight.

For more information, including Zoom link and password, contact either Erik Hobbie, (701) 231-6103, erik.hobbie@ndsu.edu, or Dean Webster, 701-231-88709, dean.webster@ndsu.edu

Polylactic Acid from Residual Woody Biomass: A Chemical Process Simulation, Techno-Economic Analysis and Life Cycle Assessment, Dr. Francesca Pierobon, University of Washington, Seattle, WA

Forest operations in the U.S. Pacific Northwest produce large amounts of residual woody biomass, mainly consisting of treetops and branches. This biomass is typically left on the forest floor to decompose or burned in prescribed fires to reduce the risk of wildfires. Using residual woody biomass as a raw material to produce biochemicals and bioenergy products may reduce the impact on global warming and human health as well as prevent wildfires and displace fossil fuels. This webinar will present the results of a USDA research project to explore the technical, economic and environmental viability of producing polylactic acid and lignin-based coproducts from residual woody biomass. The study includes a Chemical Process Simulation, Techno-Economic Analysis and Life Cycle Assessment.

For more information, including WebEx link and password, contact either Erik Hobbie, (701) 231-6103, erik.hobbie@ndsu.edu, or Dean Webster, 701-231-88709, dean.webster@ndsu.edu

MNT Doctoral graduate M. Reza Parsa published a paper in Physical Review Letters the flagship journal of the American Physical Society. Using the recently introduced molecular dynamics lattice gas approach, Dr. Parsa and his advisor, Physics/MNT professor Alexander Wagner, developed a new way to deal with large fluctuations of coarse-grained quantities. The paper entitled Large Fluctuations in Nonideal Coarse-Grained Systems appeared in the June 12, 2020 issue of PRL. Dr. Parsa is currently a postdoc in applied mathematics at UC-Merced.

Another recent MNT Doctoral graduate, Todd Pringle, just published a paper in ACS Nano demonstrating a new approach for making silicon quantum dots. The NDSU led effort used a liquid form of silicon (Si₆H₁₂) to make the tiny particles in a non-thermal plasma. Pringle is the president of Lumacept Inc., a company that produces the only available coating designed to reflect germ-killing ultraviolet light, called UV-C. Lumacept is currently helping health care providers decontaminate and re-use their personal protective equipment. The team included researchers from North Dakota State University, the University of Minnesota, Northwestern University, the National Institute of Standards and Technology, and Argonne National Laboratory. Their research paper Bright Silicon Nanocrystals from a Liquid Precursor: Quasi-Direct Recombination with High Quantum Yield was published by the American Chemical Society in the April 2020 edition of ACS Nano.

Biofunctional Surfaces from Protein-Polymer Self-Assemblies, Dr. Bradley Olsen, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Protein-based materials show a great deal of potential as catalysts, sensors, and optoelectronics, where the unique efficiency, selectivity, or activity of enzymes can be captured to improve the performance of these devices. Control over the structure and orientation of the protein in three dimensions is required to improve transport through the devices, increase the density of active sites, and optimize the stability of the protein. We are exploring two different methods to engineer protein-based biofunctional nanomaterials: self-assembly of globular protein-polymer conjugates and fusion proteins into nanostructured phases, and templating of protein nanostructures using coacervation with block copolymers. In particular, biosensors provide some of the most promising methods for the detection of different compounds of interest for the environment and health, enabling extremely high specificity and often high sensitivity through different modalities including both affinity and enzymatic biosensors. Here, we describe the technique of bioconjugate self-assembly and its application to improve affinity biosensing films via generating biofunctional surfaces with an extremely high density of active protein. Subsequently, the use of protein-polymer coacervates is presented as a technology that can be easily explored in surface coatings for both flat substrates and fabrics. We demonstrate the use of these technologies for protein encapsulation and heavy metal detection as well as fundamental studies of how the protein affects nanostructure within the copolymer films.

For more information, contact Mohi Quadir, (701) 231-6283, mohiuddin.quadir [at] ndsu [dot] edu

Colloidal Silicon and Germanium Nanocrystals, Nanorods and Nanowires,Dr. Brian A. Korgel, McKetta Department of Chemical Engineering and Texas Materials Institute, University of Texas, Austin, TX

Compared to other types of semiconductor materials, several unique challenges face the solution-phase, colloidal synthesis of silicon (Si) and germanium (Ge) nanocrystals.  To obtain silicon (Si) and germanium (Ge) nanocrystals by solution-phase colloidal synthesis, it is first of all necessary to identify reactants and reaction schemes that produce high yields of zero valent Si and Ge.  This is not a trivial task.  The method must also yield materials that are crystalline, and not amorphous or oxidized.  Typical colloidal synthesis employs capping ligands that reversibly bond to the nanocrystal surface to control growth.  For the well-studied metal chalcogenides like CdSe and PbS, these issues are not particularly daunting, but in the case of Si and Ge, these are major challenges because of the relatively low temperatures of typical solution-phase chemistry compared to those typically needed to decompose Si and Ge reactants and to crystallize Si and Ge.  We have been able to circumvent these challenges in various ways, for example by using high temperature supercritical or solvothermal conditions and/or adding metal nanoparticles to induce crystallization of nanorods or nanowires.  In the case of Si, phenylsilane and various silanes, especially trisilane, have been very useful reactants.  For Ge nanomaterials, phenylgermane and GeI₂ have been especially useful.  This talk will describe several lessons learned over the years in the colloidal synthesis of crystalline Si and Ge nanocrystals, nanorods and nanowires. 

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Quantum Confined Semiconductors for Solar Photon Energy Conversion,Dr. Matthew C. Beard, Center for Advanced Solar Photophysics, National Renewable Energy Laboratory, Golden, CO

Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photon-to-free energy conversion step. In this discussion, I will present the current status of research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and photoelectrodes and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells and photoelectrodes are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. Different chemical treatments of the QD layer are employed in order to obtain good electrical communication while maintaining the quantum-confined properties of the individual QDs. A unique aspect of our devices is that the QDs exhibit multiple exciton generation (MEG) with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor. The efficiency of the MEG process can be further increased by increasing the complexity of the nanostructures.  We have synthesized Janus-like nanocrsytals that are spherical in shape yet asymmetric in composition.  These nano-heterostructures demonstrate an enhanced MEG efficiency relative to the spherical single-phase quantum dots.

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Thermosetting Polymers and Composites from Agricultural Oils,Dean Michael Kessler, College of Engineering, North Dakota State University, Fargo, ND

Renewable, bio-based thermosetting copolymer resins, ranging from tough and ductile rubbers to hard and glassy plastics to durable waterborne latex coatings, have been prepared by the polymerization of soybean, corn and linseed oils with various co-monomers. The development of these resin formulations with the right combination of processing viscosity, cure kinetics, and ultimate thermal mechanical properties for various manufacturing processes will be discussed. As expected, the thermal and mechanical properties, as well as the long term environmental durability of the material, are shown to be highly dependent on vegetable-oil composition, processing conditions, and co-monomer chemistry. These bioplastic composites are likely to have a tremendous impact economically, environmentally and energy-wise, since the oils are (1) readily available in huge quantities from a renewable natural resource, (2) much cheaper than petroleum-based resins used in many polymers and composites, and (3) able to provide properties not presently available in commercial plastics.

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Theory and Simulation of Dispersions with Competing Interactions Applied to Protein Solutions,Dr. Gerhard Nägele, Institute for Complex Systems, Forschungszentrum Jülich, Jülich, Germany

Dynamic clustering of globular particles in dispersions exhibiting competing short-range attraction and long-range repulsion (SALR) such as in low-salinity protein solutions has gained a lot of interest over the past years. We investigate the influence of clustering on the dynamics and structure of globular particle dispersions. For this purpose, we combine a semianalytic hybrid method where hydrodynamic interactions (HIs) are approximately included with multi-particle collision (MPC) simulations accounting for the full many-particles HIs. By this simulation-theory comparison, we establish the high accuracy of the hybrid method for calculating diffusion and viscosity properties of SALR systems in the dispersedfluid phase region. We show that a cluster peak is present also in the hydrodynamic function characterizing the short-time dynamics, in accord with neutron spin echo results on lysozyme solutions. Enhanced short-range attraction leads to a smaller self-diffusion coefficient and a larger dispersion viscosity. The behavior of the (generalized) sedimentation coefficient is more intricate showing, e.g., non-monotonic interaction strength dependence. Inter- and intraclusters dynamics in the equilibrium cluster phase region is analyzed using MPC simulations. Simulation results for the mean cluster lifetime, and the comparison with the dissociation time of an isolated particle pair reveal quantitative differences, pointing to the importance of many-particle HIs for the cluster dynamics. The cluster lifetime in the cluster-fluid phase increases far stronger with increasing attraction strength than in the dispersed-fluid phase. Significant changes in cluster shapes are observed in the course of time.

For more information, contact Alan Denton, 701-231-7036, alan.denton [at] ndsu [dot] edu

Flow Behaviors of Polymer Systems Manipulated by Particles,Professor Guangxian Li, College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, China

The incorporation of various kinds of inorganic particles into multiphase polymeric materials has produced great success in preparing novel materials with superior performance or functionalities. However, the key role of particles in the formation of hierarchical structures in multiphase systems during melt flow is far from unraveled. In this lecture, we will report on our recent work in particle-tailored structure in flowing polymer blends. Special emphasis will be devoted to demonstrating how particle parameters (including particle distribution, surface chemistry and concentration) and flow conditions affect the droplet dynamics under flow. Morphological stabilization mechanisms caused by particles will be discussed in terms of viscoelasticity, interfacial properties, crystallization and phase behavior. Finally, the role of particle shape will be demonstrated by an interesting vorticity alignment of the droplet phase under flow.

For more information, contact Long Jiang, 701-231-9512, long.jiang [at] ndsu [dot] edu

The Full Spectrum Boost Project in Nanoparticle Solar Cells: Downconversion, Upconversion, Transport,Professor Gergely Zimanyi, Department of Physics, University of California, Davis

Recent progress in nanoparticle solar cells is reviewed. Colloidal nanoparticles provide a versatile platform to implement genuinely pathbreaking physical processes for solar energy conversion. Examples include the downconversion process of multiple exciton generation, where a single incoming photon generates more than one electron. One of the most promising upconversion processes is the intermediate band mechanism, where two low energy photons cooperate to excite one electron to the conduction band. The grand scheme of "full spectrum boost" will be presented that uses this downconversion and upconversion process to boost the energy conversion efficiency across the entire solar spectrum. In the second half, transport phenomena will be reviewed and different classes of metal-insulator transitions in nanoparticle solar cells will be presented.

For more information, contact Andrei Kryjevski, 701-231-7046, andrei.kryjevski [at] ndsu [dot] edu

Droplet Assisted Vapor Phase Polymerization (DA-VPP) for Controlling Low Dimensionality in Nanostructures and Microstructures of Conducting Polymers,Professor Julio M. D'Arcy, Department of Chemistry, Washington University in St. Louis

The D’Arcy laboratory develops vapor phase polymerization strategies for nanostructured conducting polymers and investigates fundamental structure-property relationships of low dimensional organic electronics for electrochemical energy storage applications. Here, droplet-assisted vapor phase polymerization (DA-VPP) results in low dimensional structures of conducting polymers such as nanofibers, nanowires and microtubes without the use of templates. In DA-VPP, monomer vapor is oxidized by a ferric chloride aqueous droplet to initiate oxidative radical polymerization and promote step-growth assembly of a conjugated polymer backbone. Water evaporation and condensation processes, that stabilize the three-phase solid-water-air interface present on a resting droplet, control polymerization kinetics during DA-VPP. Furthermore, concentration, temperature, pH of aqueous droplet, and the rate of mass transfer of reactant vapors are chemical handles that enable the synthesis of a conducting polymer with high electronic conductivity and superior electrochemical stability. Grafting on aromatic groups present on a hard carbon fiber substrate is carried out by Friedel-Crafts alkylation using iron chloride as a catalyst and nitromethane as a catalyst activator. Poly(3,4-ethylenedioxythiophene) grafted on carbon fiber current collectors affords electrochemical capacitors retaining 90% of their initial capacitance over 350,000 cycles in 1 M H₂SO₄ at 5 A/g current density in a 1 V window. Moreover, low temperature DA-VPP leads to polypyrrole nanobrushes and pseudocapacitors that undergo 200,000 cycles while retaining 70% of their initial capacitance. A coating of polypyrrole microtubes possesses a sheet resistance of 70.2 ohm/sq and serves as a mechanically robust electrode architecture characterized by a high reversible capacitance of 342 F/g throughout 5,000 cyclic voltammetric cycles.   

For more information, contact Mohi Quadir, 701-231-6283,  mohiuddin.quadir [at] ndsu [dot] edu

Nanocellulosic Materials: From Preparation to Applications,Professor Yulin Deng, School of Chemical & Biomolecular Engineering, Georgia Institute of Technology

In this talk, I will briefly discuss our recent research as well as some published works from other groups related to cellulosic nanomaterials. The applications of CNF (cellulose nanofibrials) and CNC (cellulose nanocrystals), such as barrier films for packaging, aerogels from oil/water separation, 3D printed aerogels for bioscaffold, porous electrode for supercapacitor, chemical surface modification for polymer composites, will be discussed.

For more information, contact Long Jiang, 701-231-9512, long.jiang [at] ndsu [dot] edu

DNA Topology and Genomic Information Processing, Professor Laura Finzi, Department of Physics, Emory University

DNA is a right-handed, double helical polymer that encodes genetic information. Its topology is dynamically changed by proteins and enzymes. In this talk, I will describe our use of single molecule techniques to understand critical topological changes that regulate genomic function.

For more information, contact Yongki Choi, 701-231-8968, yongki.choi [at] ndsu [dot] edu

Conformational Dynamics Dictate Normal and Abberant Function of Protein Kinase A, Professor Gianluigi Veglia, Department of Biochemistry, Molecular Biology and Biophysics, Department of Chemistry, University of Minnesota

Eukaryotic protein kinases (EPKs) constitute a class of allosteric switches that mediate several signaling events. Protein kinase A is a prototypical kinase of paramount biological importance as it is involved in a myriad of cellular processes. In this talk, I will show how state-of-the-art nuclear magnetic resonance (NMR) techniques can trace the intramolecular allosteric network responsible for activation and deactivation of kinase A. In particular, I will emphasize to role of hydrophobic spines within the catalytic core that are essential for the catalytic turnover. In the apo form, the C-spine is disassembled, with the two lobes of the enzyme dynamically uncommitted. Nucleotide binding locks the architecture of the catalytic spine, synchronizing the motions (committed dynamics) in the hydrophobic core. While pseudo-substrate binding further rigidifies of the spines, the conformational dynamics of the core are retained with natural substrates. Since the C-subunit is highly conserved within the kinase family, the present study offers novel mechanistic insights into intramolecular signaling of protein kinases that can serve for the design of novel activators or inhibitors of kinases.

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Carbon Nanomaterial Microelectrodes for Neurotransmitter Detection, Professor B. Jill Venton, Department of Chemistry, University of Virginia

Carbon nanotubes have interesting electrochemical properties including fast electron transfer kinetics and high surface areas. Common acid purification techniques also result in oxidative functional groups which can serve as adsorption sites for neurotransmitters. The use of CNTs in fabricating larger electrodes has been widely demonstrated but the reproducible production of small, sensitive CNT-based sensors is not as well studied. My lab has investigated several different techniques for making CNT-based microelectrodes and tested their response using fast-scan cyclic voltammetry. This talk will compare CNT-modified carbon-fiber microelectrodes, CVD grown aligned CNTs, CNT yarns, and CNT fibers for use as microelectrodes. In general, alignment of CNTs and chemical functional groups determine the sensitivity of the electrode for neurotransmitters. Also, CNT yarns and fibers have different adsorption properties that allow them to be used with higher temporal resolution without a decrease in sensitivity. We have also studied other types of carbon nanomaterials including carbon nanospikes and amorphous carbon on nanopipettes. Our work reveals that carbon nanomaterial-based microelectrodes are advantageous as electrochemical sensors for neurotransmitters. 

For more information, contact Yongki Choi, 701-231-8968, yongki.choi [at] ndsu [dot] edu

Out-of-the-Box Solutions to Silicon Crystal Growth Problems, Harold Korb, Korb Consulting, LLC

The Czochralski process for growing silicon crystals is capable of producing high quality crystals at high yield and reasonable cost. The expectation is that every wafer produced from those crystals will be free from measurable defects, and the manufacturing process will be error-free. If straightforward engineering changes can’t provide solutions to quality problems, a more basic attack may help. I will describe three problems that benefitted from a different angle of attack: a) The creation of a method to pump liquid silicon using electromagnetic means; b) The identification of the mechanism by which small spherical bubbles can be grown into a silicon crystal, and c) (if time permits) The determination of the conditions under which electrical breakdown (arcing) in Ar should occur at high temperature and low pressure.

For more information, contact Sylvio May, 701-231-7088, sylvio.may [at] ndsu [dot] edu

Impact of Chain Conformation and Dynamics on Macroscopic Properties of Polymer Melts and Nanocomposites, Professor Gerald Schneider, Department of Chemistry, Louisiana State University

Intense research has led to substantial progress towards understanding the fundamentals of polymer melts and polymer-based nanocomposites. Characterizing the polymer dynamics at micro- and mesoscopic scales is often of particular interest. For example, it is important for modeling the macroscopic material response needed for the target-oriented engineering of new hybrid materials. It may lead to optimized materials ranging from the classical car tire to battery or fuel cell applications. This presentation highlights research on model nanocomposites well suited to act as interlinks between a theoretical understanding and technical applications, while shedding light on the influence of hard impenetrable surfaces on polymer melts. It presents a link from the morphology and dynamics at microscopic and mesoscopic scales to material properties, such as those measured by rheology experiments.

For more information, contact Sylvio May, 701-231-7088, sylvio.may [at] ndsu [dot] edu

From Self-Assembly to Electrokinetics: Novel Predictive Capabilities for Dielectric Effects, Professor Erik Luijten, Materials Science and Engineering, Northwestern University

The ability of matter to self-organize in complex dynamic structures is increasingly used to generate new, active materials. Progress in this field critically depends on the predictive capabilities of reliable and efficient computer simulation strategies. Here, I will introduce new, computational methodologies for dielectric effects, and demonstrate that these methods make it possible to perform dynamic simulations that fully incorporate self-consistently calculated polarization charges. Notably, I will discuss how the impact of these developments ranges from the prediction and control of colloidal and nanoscale self-assembly and aggregation to the understanding of dynamical properties of self-propelled particles that form the basic building blocks of active matter. I will also show how these ideas have the potential to find application in the understanding of supercapacitors and other energy-related problems.

For more information, contact Sylvio May, 701-231-7088, sylvio.may [at] ndsu [dot] edu

Exciton Dynamics and Optical Properties of Single Semiconductor Carbon Nanotubes and Nanotube Bundles, Dr. Andrei Piryatinski, Los Alamos National Laboratory

Semiconductor single-walled carbon nanotubes (CNTs) are near-perfect 1D materials with great potential for applications in opto-electronic and photonic devices. Their unique optical properties are determined by highly mobile interacting excitons. Motivated by experiment, we examine competition between exciton diffusion dynamics and their local interactions resulting in the exciton-exciton annihilation. Our model explains experimentally observed dependence of the exciton emission profile on the intensity of the optical pump and further allows for the interpret of the photon counting statistics probed by measuring the 2nd order photon number correlation function. We also examine the effect of exciton states modulation by external periodic potential due to the acoustic wave propagating along CNT substrate, and demonstrate that the potential induces Floquet sub-bands separated by dynamical gaps in the single particle spectrum. This leads to redistribution of the exciton oscillator strength and subsequent fluorescence quenching. Finally, motivated by experimental studies, we examine spectral signatures of interacting intratube and intertube exciton states formed in bundles of CNTs. For this purpose, an exciton scattering model is developed. Considering optimized geometry hexagonal lattice CNT bundle, we identified the sites participating in the formation of the intertube excitons. These sites are treated as an interacting “impurity centers” giving rise to the delocalized intratube exciton scattering. Modeling of the Raman resonance excitation profiles in (6,5) CNTs demonstrates an appearance of a sharp feature at the red shoulder of the spectrum that has been observed experimentally. The model-based analysis confirms that the feature is due to the weakly coupled interband exciton states.

For more information, contact Svetlana Kilina, 701-231-5622, svetlana.kilina [at] ndsu [dot] edu

Polymer-Based Nanocoatings Applied to Fabric Substrates for Flame Retardancy and Thermoelectric Energy Generation, Professor Jaime Grunlan, Texas A&M University

Layer-by-layer (LbL) assembly is a conformal coating “platform” technology capable of imparting a multiplicity of functionalities on nearly any type of surface in a relatively environmentally friendly way. At its core, LbL is a solution deposition technique in which layers of cationic and anionic materials (e.g. nanoparticles, polymers and even biological molecules) are built up via electrostatic attractions in an alternating fashion, while controlling process variables such as pH, coating time, and concentration. Here we are producing nanocomposite multilayers (50-1000 nm thick), having 10-96 wt % clay, that are completely transparent and exhibit oxygen transmission rates below 0.005 cm³/m²·day.  Phosphorus and nitrogen-rich molecules can also be used to impart intumescent behavior.  These multilayer assemblies are very conformal and able to impart flame resistance to highly flammable woven and nonwoven fabric substrates without altering other beneficial properties intrinsic to the fibers themselves (strength, breathability, etc.).  Nylon-cotton and polyester-cotton blends have passed standard vertical flame tests (ASTM D6413) with 12-18 wt % coating deposited.  Similar nanocoatings produced with graphene and carbon nanotubes have a surprisingly high Seebeck coefficient (> 100 mV/K) and exhibit very high thermoelectric power factor (up to 3000 mW/m·K²).  We hope to eventually produce fabric that can generate voltage from body heat.  Our work in these areas has been highlighted in C&EN, ScienceNews, Nature, Smithsonian Magazine, Chemistry World and various scientific news outlets worldwide.

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Novel Poly(vinyl ether)s Derived from Renewable Resources such as Plant Oils, Lignin, and other Natural Products:  An Overview, Dr. Bret Chisholm, Renuvix

Novel vinyl ether monomers were produced from a variety of compounds that can be obtained from renewable resources, such as plant oils, lignin decomposition products, and essential oils.  Using an appropriate cationic polymerization system, novel linear homopolymers and copolymers were produced that retained double bonds derived from the renewable resource.  This unsaturation was utilized to provide crosslinked networks either directly or through derivatization of the double bonds. Select polymer compositions were shown to provide substantial utility for a variety of applications including paints and coatings, personal care products, ground water remediation, and rubber compounds. This presentation will provide an overview of the chemistry and potential applications associated with this technology platform.

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

New Hybrid Materials Based on Element-Blocks, Professor Yoshiki Chujo, Department of Polymer Chemistry, Kyoto University

We recently proposed the idea of polymeric materials based on “element-blocks” or structural units consisting of various groups of elements. This is a new concept for hybrid materials that can be expected to promote new research and ideas in materials design involving all elements in the periodic table. In this talk, we show the concept of “element-block polymers” with several examples from our recent work. As a representative element block, we select boron dipyrromethene (BODIPYs) dyes, o-carborane, polyhedral oligomeric silsesquioxane (POSS) derivatives and illustrate their roles in the material properties. Initially, electric and optical functional materials are illustrated with the organoboron element blocks. The electron-transport (ET) materials and the aggregation-induced emission (AIE)-active materials are introduced based on BODIPY dyes and o-carborane, respectively. Next, the recent works for evolving organic-inorganic hybrids are demonstrated. By regarding POSS as an inorganic element block, the organic-inorganic hybrid gels were prepared and applied for the bio-relating materials. The superior properties of the POSS-containing hybrid dendrimers for the molecular recognition are presented.

For more information, contact Dean Webster, 701-231-8709, dean.webster [at] ndsu [dot] edu

On How Being Soft and Squishy Affects Phase Behavior:  The Case of Charged-Microgel Suspensions, Professor Alberto Fernandez-Nieves, School of Physics, Georgia Institute of Technology

Microgels are an interesting class of mesoscopic soft particles that can deform and compress. When suspended in a solvent at large number density, they are able to crystallize and form glasses. However, for microgels, this depends on single-particle stiffness. We will discuss recent results with charged microgel particles with different stiffness. We will first show that the suspension osmotic pressure is controlled by those counterions in solution that are able to escape from the electrostatic attraction exerted by the microgel particles. We will then exploit this fact to obtain the particle volume fraction, f, and the microgel volume as a function of particle concentration, even in highly overpacked states, where the particles are forced to both change shape and compress. In terms of f, we find that the width of the fluid-crystal coexistence region decreases with decreasing microgel stiffness to eventually disappear for sufficiently soft microgels; in these cases, the suspensions remains fluid-like at all explored concentrations. By comparing our results with expectations from computer simulations, we propose possible interparticle-interactions that could potentially capture our experimental observations.

For more information, contact Alan Denton, 701-231-7036, alan.denton [at] ndsu [dot] edu

Electrical Double Layer Structure at the Water-Silica Interface: Role of Counterion Size, pH and Hydration Interactions, Professor Matthew A. Brown, Laboratory of Surface Science and Technology, Department of Materials, ETH Zürich

The structure of the electrical double layer has been debated for well over a century, since it mediates colloidal interactions, regulates surface structure, controls reactivity, sets capacitance and represents the central element of electrochemical supercapacitors. The surface potential of such surfaces generally exceeds the electrokinetic potential, often substantially. Traditionally, a Stern layer of non-specifically adsorbed ions has been invoked to rationalize the difference between these two potentials; however, the inability to directly measure the surface potential of dispersed systems has rendered quantitative measurements of the Stern Layer potential, and other quantities associated with the Outer Helmholtz Plane, impossible. Here we describe our development of X-ray photoelectron spectroscopy (XPS) from a liquid microjet to measure the absolute surface potentials of silica nanoparticles dispersed in aqueous electrolytes. We quantitatively determine the impact of specific cations (Li⁺, Na⁺, K⁺, and Cs⁺) in chloride electrolytes on the surface potential, the location of the shear plane and the capacitance of the Stern layer. We find that the magnitude of the surface potential increases linearly with hydrated cation radius. Interpreting our data using the simplest assumptions and most straightforward understanding of Gouy-Chapman-Stern theory reveals a Stern layer (bounded by the Outer Helmholtz Plane) whose thickness corresponds to a single layer of water molecules hydrating the silica surface, plus the radius of the hydrated cation. We describe a modified Poisson-Boltzmann (PB) model that adds hydration repulsion between counterions to their Coulomb interaction. While retaining much of the simplicity of the classical PB model, this modified model predicts surface potentials and Stern layer thicknesses for the different counterions that are in excellent agreement with the experiments.

For more information, contact Sylvio May, 701-231-8968, sylvio.may [at] ndsu [dot] edu

Mixed Valence State Nanoceria and it's Role in Angiogenesis, Professor Sudipta Seal, Pegasus Professor and University Distinguished Professor, Director of AMPAC and NanoScience Technology Center (NSTC), University of Central Florida

Angiogenesis is the formation of new blood vessels from existing blood vessels and is critical for many physiological and pathophysiological processes. In this study we have shown the unique property of redox active nanoparticles (Re-NPs) to induce angiogenesis, observed using both in vitro and in vivo model systems. In particular, Re-NPs trigger angiogenesis by modulating the intracellular oxygen environment and stabilizing hypoxia inducing factor 1alpha endogenously. Furthermore, correlations between angiogenesis induction and Re-NPs physicochemical properties including: surface valence state ratio, surface charge, size, and shape were also explored. High surface area and mixed valence states make these nanoparticles more catalytically active towards regulating intracellular oxygen, which in turn led to more robust induction of angiogenesis. Atomistic simulation was also used, in partnership with in vitro and in vivo experimentation, to reveal that the surface reactivity of NPs and facile oxygen transport promotes pro-angiogenesis. (This research is funded by USA National Science Foundation and National Institute of Health) At the end, I will conclude the talk describing our research activities at Materials and Nano Center at UCF.

For more information, contact Kalpana Katti, 701-231-9504, kalpana.katti [at] ndsu [dot] edu

Ultra-Resolution Photoluminescence Spectroscopy and Electron Microscopy to Probe the Spatial Distribution of Emitted Photons from Semiconductor Nanocrystalline Higher Order Structures, Professor Alan Van Orden, Department of Chemistry, Colorado State University

This presentation will report new techniques to investigate excited state electronic energy transport in semiconductor nanocrystalline quantum dot (QD) higher order structures, from small aggregates to macroscopic thin films. QDs have attracted considerable scientific interest because of their unique size-tunable optical and electronic properties, and their ability to be used as nanometer scale building blocks in a broad range of optoelectronic devices and biological labelling applications. In many cases, a large ensemble of quantum dots must be organized into higher order structures. QD higher order structures have characteristic optical properties that are distinct from isolated QDs, due to the ability of the QDs to interact with each other through electronic coupling and/or energy transfer. Researchers attempting to characterize or model this coupling normally must rely on spectroscopic information that averages over large ensembles of QDs. However, the coupled QDs often exist in heterogeneous surroundings, with wide variations in cluster sizes, interparticle spacings, and local environments. Thus, ensemble averaging techniques have a limited ability to uncover the detailed interactions involved in the coupling. Furthermore, ensemble methods do not have the ability to investigate the single molecule dynamics of the QDs, or the impact of these dynamics on the optical and electronic properties of the higher order structures. To overcome these limitations, we have developed novel super-resolution imaging microscopy techniques to spatially resolve the photoluminescence coming from individual QDs within higher order structures. We have also developed novel methods to spatially correlate the super-resolution imaging data with ultra-resolution scanning and transmission electron microscope images. Using these techniques, we can trace the energy transport pathways among the QDs and precisely measure, with sub-nanometer precision, the QD sizes, structural arrangements, inter-QD distances, and crystal lattice orientations. We are using these combined methods to investigate the intricate relationships between structure, electronic energy transport, and function in these important systems.

For more information, contact Erik Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Probing Single-Molecule Protein Conformational Dynamics in Enzymatic Reactions and Cell Signaling, Professor H. Peter Lu, Ohio Eminent Scholar and Professor, Department of Chemistry, Bowling Green State University

Enzymatic reactions are traditionally studied at the ensemble level, despite significant static and dynamic inhomogeneities.  Subtle conformational changes play a crucial role in protein functions, and these protein conformations are highly dynamic rather than being static. We applied single-molecule spectroscopy to study the mechanisms and dynamics of enzymatic reactions involved with kinase and lysozyme proteins.  Enzymatic reaction turnovers and the associated structure changes of individual protein molecules were observed simultaneously in real-time by single-molecule FRET detections.  We obtained the rates for single-molecule conformational active-site open-close fluctuation and correlated enzymatic reactions.  Our new approach is applicable to a wide range of single-molecule FRET measurements for protein conformational changes under enzymatic reactions and protein-protein interactions in cell signaling.  Using this approach, we analyzed enzyme-substrate complex formation dynamics to reveal (1) multiple intermediate conformational states, (2) conformational motions involving in active complex formation and product releasing from the enzymatic active site, and (3) conformational memory effects in the chemical reaction process. Furthermore, we have applied AFM-enhanced single-molecule spectroscopy to study the mechanisms and dynamics of enzymatic reactions.  We obtained the rates for single-molecule conformational active-site open-close fluctuation and correlated enzymatic reactions.  We have demonstrated a specific statistical analysis to reveal single-molecule FRET anti-correlated fluctuations from a high background of fluorescence correlated thermal fluctuations.  Our new approach is applicable to a wide range of single-molecule AFM-FRET measurements for protein conformational changes under enzymatic reactions, including AFM-FRET control of enzymatic reactivity by mechanical-force manipulating protein conformations.

For more information, contact Yongki Choi, 701-231-8968, yongki.choi [at] ndsu [dot] edu

Mechanics of Ultrathin Polymer Films: Viscoelasticity, Dynamics and Rubbery Response of Membranes, Professor Greg McKenna, Department of Chemical Engineering, Texas Tech University

Determination of the mechanical response of polymeric materials with dimensions less than 100 nm is a continuing challenge. Here we describe a novel membrane (“nano-bubble”) inflation method we have developed for the purpose of making measurements of the creep response of ultrathin polymer films and show two major findings. The first is that the material dynamics as measured by the creep response of the membranes depends dramatically on film thickness. For example, in polystyrene films, the dynamics is accelerated so much that the glass transition temperature of a 11 nm thick film is reduced by approximately 50 K relative to the macroscopic value. Furthermore, we have discovered that the nominal rubbery plateau in ultrathin films is stiffened by upwards of two orders of magnitude relative to the macroscopic state and the rate of stiffening (stiffening index S) correlates with the shape of the segmental relaxation in accordance with a recent model proposed by Ngai, Prevosto and Grassia. We have elaborated this finding further and observe a strong correlation with the fragility index m that is related to glass formation according to the Angell categorization of super cooled liquids. These results will be discussed in terms of current understanding of the impact of nanoconfinement on the glass transition behavior of polymers. In addition to being able to characterize the creep response of the ultrathin polymer films, we have also succeeded in adapting the bubble inflation method to make measurements on a graphene/polymer nano-sandwich structure and show that the method can be used to not only extract the stiffness of the graphene inner layer of the composite but that the method can be used to extract the interfacial shear strength of the polymer-graphene couple.

For more information, contact Andrew Croll, 701-231-8974, andrew.croll [at] ndsu [dot] edu

Ab Initio Electron Dynamics at Metal-Semiconductor Nanointerfaces, Professor Dmitri Kilin, Department of Chemistry, University of South Dakota

Photo-induced charge transfer at the interface of two materials is a fundamental process in (i) photovoltaic and (ii) photocatalytic applications. The photo-induced time-dependent electron dynamics are computed for different interfaces by a combination of ab initio electronic structure and time-dependent density matrix methodology. A dissipative equation of motion for the reduced density matrix for electronic degrees of freedom is used to study the phonon-induced relaxation of hot electrons in the simulated systems. Non-adiabatic couplings between electronic orbitals are computed on-the-fly along nuclear trajectories. Equations are solved in a basis set of orbitals generated ab initio from a density functional.  For an application to photovoltaic effect, one explores light-induced electric current in a model of a simplified photovoltaic cell composed of a Si nano-crystal co-doped with p-and n- type doping, interfacing with Au electrodes. Charge carrier dynamics induced by selected photo-excitations show that hole relaxation in energy and in space is much faster than electron relaxation. Use of the continuity equation for electric current allows us to identify substantial local currents at the Si/Au interfaces and small overall net charge transfer across the slab. For an application to photocatalytic water splitting, charge transfer dynamics is explored at the interface of supported metal nanocluster and liquid water. The metal cluster introduces new states into the band gap of semiconductor TiO₂ surface, narrows the band gap of TiO₂, and enhances the absorption strength. The H₂O adsorption significantly enhances the intensity of photon absorption, which is due to the formation of metal-oxygen (water) coordination bonds at the interfaces. The metal cluster promotes the dissociation of water, facilitates charge transfer, and increases the relaxation rates of holes and electrons. Reported results help in understanding basic photophysical and protochemical processes contributing to harvesting solar energy by photovoltaics and photoelectrochemical water splitting.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Ruga Mechanics of Folding Atomic-Layer Nanostructures, Professor Kyung-Suk Kim, Institute of Molecular and Nanoscale Innovation, Brown University

When one folds a thin solid film that is only a few atoms thick, such as graphene, the film properties can be controlled for various functions. For example, a simple compression of the folded film can change optical, electrical, wetting and adhesion characteristics of the film, and can be used for making multifunctional materials such as transparent electric circuits, self-cleaning surfaces, oil-spill cleaning cloths and self-adjusting friction grips. Such atomic-layer nanostructures can be folded and self-organized by nonlinear large deformation of soft material substrates. In particular, nano science and technology has enabled us to explore new functional properties of hierarchically ruga-structured materials through folding or wrapping thin atomic-layer structures with nanometer scale features. The Latin word ruga means a state of a “large-amplitude” wrinkle, crease, fold or ridge to form various 1-D or 2-D patterns. As multi-scale surface morphologies of rugae determine effective properties such as wetting, adhesion, friction, flexoelectric and optoelectronic properties, ruga state control is considered as a viable method for real-time regulation of effective material properties. It is found that graded or layered elastic properties of the substrate can provide diverse bifurcation paths of the attached atomic-layer deformation under lateral compression, producing various atomic-layer ruga states. Nonlinear mechanics of soft-material substrate enables us to construct ruga-phase diagrams. As an example, a mathematical analysis of sequential bifurcation processes of hyper-elastic neo-Hookean substrates is used to construct generic ruga-phase diagrams. When an atomically layered structure such as multi-layer graphene is folded by ruga control, nano-scale crinkles are generated. In general, nano-scale crinkle ridges are invisible to conventional AFM due to its peculiar flexoelectric properties. Here, a new invention of “Dual-Tip AFM Interferometer” (DT-AFMI) will be introduced, which makes the invisible visible. The DT-AFMI image reveals that the crinkle ridge of a multi-layer graphene has its ridge width less than 1.8nm. The nano-crinkle ridges have strong flexoelectric characteristics, and the crinkle ridge networks of the top graphene layer exhibit high molecular adsorptivity. Potential applications of such high molecular adsorptivity localized along the nano-ridges will be discussed as well.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

Encapsulation of Solutes in Lipid Vesicles: Origins of Life Considerations, Dr. Tereza Pereira de Souza, Rowland Institute, Harvard University

In the past years we have investigated the entrapment of macromolecules inside vesicle by analyses of cryo-transmission electron microscopy of liposome populations created in the presence of ferritin, ribosomes and small macromolecular aggregates. And surprisingly, results reveal that the local (intra-liposomal) macromolecules concentration in these liposomes largely exceeds the bulk concentration. This seminar aims to summarize and discuss these results under the light of the origins of life scenario and synthetic biology, addressing question as: What is the minimal size of a minimal cell? Is the number of entrapped macromolecules inside vesicles homogeneous? Lipid compartments are frequently addressed as agents of confinement and protection, but could these compartments have a more active role in the pre-biotical scenario? In another words, does the formation of lipid compartments play a role in concentrating the "entrapped to be" macromolecules?

For more information, contact Sylvio May, 701-231-7048, sylvio.may [at] ndsu [dot] edu

Transdermal Therapeutic Systems: Structure, Function and Exelon(r) as a Convincing Example, Prof. Dr. Alfred Fahr, Department of Pharmaceutics, Friedrich-Schiller-University Jena, Germany

Transdermal Therapeutic Systems (TTS) have made their way over the last decades as an alternative to oral formulations not only for circumvention of the first pass effect as for example delivering nitroglycerine, but also for maintaining steady plasma level values and for reducing serious side effects during therapy. A very good example for the latter case is the Exelon TTS(r) with its active ingredient rivastigmine, which is used in therapies against Alzheimer's disease.

For more information, contact Sylvio May, 701-231-7048, sylvio.may [at] ndsu [dot] edu

Elasticity-Based Mechanism for Collective Motion in Natural and Artificial Swarms,  Dr. Cristián Huepe, Department of Applied Mathematics, Northwestern University

Collective motion is one of the simplest forms of self-organization in systems of active components such as cell colonies, bird flocks, fish schools, or groups of autonomous robots.  Its emergence in fluid-like swarms with aligning interactions has been the focus of much research activity. In this talk, I will introduce a different model for collective motion, consisting of self-propelled particles connected by linear springs without explicit aligning dynamics. In this system, a simple elasticity-based mechanism drives the particles to self-organize by cascading self-propulsion energy towards lower-energy modes. Given its ubiquity, this mechanism could play a relevant role in various natural and artificial swarms.

For more information, contact Thomas Ihle, 701-231-7045, thomas.ihle [at] ndsu [dot] edu

Infectious Diseases, Auto-Immune Diseases, and Opportunities for Biophysics, Professor Gerard Wong, Department of Bioengineering, Department of Chemistry & Biochemistry, California Nanosystems Institute, UCLA

We present examples from our group where biophysics impacts unsolved medical problems. We start with bacterial biofilms, which are structured multi-cellular communities that are fundamental to the biology and ecology of bacteria. The first step in biofilm formation, adaptation to life on a surface, requires the coordination of biochemical signaling, polysaccharide production, and molecular motility motors. These crucial early stages of biofilm formation are at present poorly understood. By adapting tracking algorithms from colloid physics, we dissect bacterial social behavior at the single cell level.  We will also discuss how we can learn from innate immunity peptides, and renovate antibiotic design via the biophysics of peptide-membrane interactions. Finally, we examine the pathological role of antimicrobial peptides in autoimmune diseases.

For more information, contact Sylvio May, 701-231-7048, sylvio.may [at] ndsu [dot] edu

Making Non Stick Coatings out of Thin Air, Professor Robert Lamb, Canadian Light Source Inc. Canada &
The University of Melbourne Australia

Non stick coatings are everywhere in nature and these have stimulated numerous practical applications. For example leaf surfaces have been the inspiration for novel waterproof textile coatings. Insect wings may hold the key to strategies for antifouling on marine vessels and the associated energy savings that go hand in hand with such developments. The latest “green” nanotechnology approach to fabricating extremely non stick surfaces involves self-organized and chemically cross linked nanoparticles. These generate exceptionally rough multi scale hierarchical interfaces that simultaneously possess a unique ability to self-clean themselves. But what is behind such an effect? Why does a lotus leaf stay clean in nature but when freshly cut it rapidly contaminates? Washing inert “dirt” from textiles is enhanced if the surface has multi scale roughness yet biological (live) contaminants “sense” subtle nanoscale features and may “hold on” despite such rinsing. Furthermore what are the requirements to turn such a curiosity into a practical technology? Shining the bright light of a synchrotron on the problem may be the answer.

For more information, contact Dean Webster, 701-231-8709, dean.webster [at] ndsu [dot] edu

Structure, Dynamics and Properties of Block Polymer Dispersions, Professor Frank S. Bates, Department of Chemical Engineering and Materials Science, University of Minnesota

Block copolymers belong to a broad class of amphiphilic compounds that includes soaps, lipids and nonionic surfactants. These macromolecules assemble into micelles with molecular dimensions on the order of 5 to 50 nm in size when mixed with excess solvent that preferentially solvates one block type. This presentation will explore two different aspects of block copolymer micelle formation.The fundamental thermodynamic and kinetic factors that control micelle shape and dynamics will be discussed based on small-angle x-ray and neutron scattering (SAXS and SANS) experiments and cryogenic transmission and scanning electron microscopy results. Although the structural features displayed by amphiphilic block copolymers resemble those associated with the self-assembly of lipids and simple surfactants (e.g., spherical and cylindrical micelles and vesicles) a macromolecular architecture leads to remarkably different dynamic properties, linked to a vanishingly small critical micelle concentration. As a consequence, molecular exchange is rapidly extinguished with increasing molecular weight resulting in non-ergotic behavior. These concepts have been exploited in developing a recently commercialized technology that provides immense improvements in the fracture toughness of thermosetting epoxy plastics, which also will be described.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu

A New Path for Nanoparticles: Toward Fully Synthetic Protein Mimics and Beyond, Professor Alfredo Alexander-Katz, Department of Materials Science and Engineering, MIT

Drug-delivery depends crucially on the ability to translocate drugs across the cell membrane. While some drugs do this naturally, most of the promising new therapies require a vehicle (or vector) that will deliver the drugs into the cytosol. Such is the way also how natural infections work. In this talk I will introduce a new counterintuitive way to bypass the membrane by exploiting fusion pathways. This work is inspired by the recent discovery that a particular class of nanoparticles can enter the cell through non-endocytotic pathways without disrupting the membrane. These nanoparticle are composed of Au protected with a multi component ligand shell. Such nanoparticles essentially behave a “nano chamaleons” altering on-the-fly their surface chemistry to mimic that of the membrane. I will discuss the origins of such behavior and uncover the pathway by which such nanoparticles enter cells. In particular, I will explain in detail how one can control the interfacial properties of the nanoparticle and potentially target different membrane compositions.  These nanoparticles can mimic several different functions performed by membrane proteins such as fusion proteins and lipid shuttling proteins, opening new possibilities in delivering drugs, as well as serving as artificial proteins themselves. Thus, understanding and controlling such a system can potentially be utilized in a wide variety of fields.

For more information, contact Alexander Wagner, 701-231-9582, alexander.wagner [at] ndsu [dot] edu

A Robust Nonlinear Block Copolymer Nanoreactor-Based Strategy to Monodisperse Hairy Nanocrystals with Precisely Controlled Dimensions, Compositions and Architectures, Professor Zhiqun Lin, School of Materials Science and Engineering, Georgia Institute of Technology

Nanocrystals exhibit a wide range of unique properties (e.g., electrical, optical, and optoelectronic) that depend sensitively on their size and shape, and are of both fundamental and practical interest. Breakthrough strategies that will facilitate the design and synthesis of a large diversity of nanocrystals with different properties and controllable size and shape in a simple and convenient manner are of key importance in revolutionarily advancing the use of nanocrystals for a myriad of applications in lightweight structural materials, optics, electronics, photonics, optoelctronics, magnetic technologies, sensory materials and devices, catalysis, drug delivery, biotechnology, and among other emerging fields. In this talk, I will elaborate a general and robust strategy for crafting a large variety of functional nanocrystals with precisely controlled dimensions (i.e., plain, core/shell, and hollow nanoparticles) by capitalizing on a new class of unimolecular star-like block copolymers as nanoreactors. This strategy is effective and able to produce organic solvent-soluble and water-soluble monodisperse nanoparticles, including metallic, ferroelectric, magnetic, luminescent, semiconductor, and their core/shell nanoparticles, which represent a few examples of the kind of nanoparticles that can be produced using this technique. The applications of these functional nanocrystals in energy-related applications (i.e., solar cells and photocatalysis) will also be discussed.

For more information, contact Erik K. Hobbie, 701-231-6103, erik.hobbie [at] ndsu [dot] edu