Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session P54: Self and Directed Assembly II |
Hide Abstracts |
Sponsoring Units: GSOFT Chair: William Rogers, Brandeis Univ Room: LACC 514 |
Wednesday, March 7, 2018 2:30PM - 2:42PM |
P54.00001: Self-Assembly of Acoustically Levitated Granular Crystals Melody Lim, Heinrich Jaeger We acoustically levitate sub-millimeter particles to visually examine the structural rearrangements of self-assembled granular crystals. By tuning the interplay between acoustic and electrostatic forces, we are able to generate structures ranging from compact particle rafts with long-range crystalline order, to Wigner crystals where the electrostatic repulsion between particles enforces a minimum equilibrium distance. In particular, we observe and characterize the transitions between degenerate ground states in the free energy landscape of compact cluster configurations. Our results provide a macroscopic experimental model for self-assembly, as well as a means to probe tribocharging in assemblies of insulating grains, which may shed light on the formation of planetesimals in protoplanetary disks. |
Wednesday, March 7, 2018 2:42PM - 2:54PM |
P54.00002: Site-Specific Colloidal Crystal Nucleation by Template-enhanced Particle Transport Chandan Kumar, A K Sood, Rajesh Ganapathy The deliberate positioning of nano- and microstructures on surfaces is often a prerequisite for fabricating functional devices. While template-assisted nucleation is a promising route to self-assemble these structures, its success hinges on particles reaching target sites prior to nucleation and for nano/microscale particles, this is hampered by their small surface mobilities. We tailored surface features, which in the presence of attractive depletion interactions not only directed micrometer-sized colloids to specific sites but also subsequently guided their growth into ordered crystalline arrays of well-defined size and symmetry. By following the nucleation kinetics with single-particle resolution, we demonstrate control over nucleation density in a growth regime that has hitherto remained inaccessible. Our findings pave the way towards realizing non-trivial surface architectures composed of complex colloids/nanoparticles as well. |
Wednesday, March 7, 2018 2:54PM - 3:06PM |
P54.00003: Polar Colloidal Polymer on-the-go: from Aligning to Sliding Jie Zhang, Steve Granick We integrate anisotropic interactions and directional mobility into Janus colloids, which directed their non-equilibrium hierarchical assembly. The first-order assembly relies on the anisotropic attraction between single particles, polymerizing them into reversible head-to-tail chains. The second-order assembly proceeds as a result of the “on-the-go” interaction paradigm between moving polar chains, in which the direction of motion largely determines the fates of interacting chains (growth, fragmentation and ring closure). Depending on the moving directions, chains with strong head-repulsion are prone to alignment and fragmentation, whereas chains with tail-repulsion tend to grow while sliding on each other. Large-scale structure of many interacting chains is determined by the dynamic interaction paradigm as well as the particle concentration. |
Wednesday, March 7, 2018 3:06PM - 3:18PM |
P54.00004: Chemical Patterns for Directed Self-assembly Blue Phase Liquid Crystals with Equilibrated Morophologies Xiao Li, José Martínez-González, Juan De Pablo, Paul Nealey In this work, we show that geometrically simple chemical patterns, made of alternate stripe-like regions with either homeotropic and planar anchoring, can be used to direct the self-assembly of specific blue-phase lattice orientations in an unprecedented fast kinetics. We further analyze the process latitude of epitaxial BPs as single crystal, i.e., the range of periodicity of the stripe-like pattern that promotes the formation of uniform BPI and BPII over macroscopic scales. We focus our study on the phase morphology and the preferred lattice orientation of BPs on such stripe-like chemical patterns, such as the period of the chemical pattern, its relation to the natural period of the BP unit cell size, the width of the chemically patterned feature, and the free energy, including contributions from the elastic energy and the interfacial energy. A fundamental understanding of the equilibrated morphologies of BPs as a function of these parameters can better serve the current technologies and broaden the potential application of directed self-assembly BPs. |
Wednesday, March 7, 2018 3:18PM - 3:30PM |
P54.00005: Electron Beam-Induced Interaction of Metal Nanoparticles on an Ionic Liquid Surface Paul Kim, Yige Gao, David Hoagland, Thomas Russell The motions of ~10-~200-nm metallic nanoparticles on vacuum-ionic liquid interfaces were observed over several minutes by in-situ scanning electron microscopy, and regardless of metal and ligand chemistry, the particles slowly migrated to the center of the area imaged, typically 12 μm x 10 μm. As the image center was approached, motion became less directed but the arriving particles eventually formed a multi-particle aggregate. A particle approaching an existing aggregate was drawn toward the aggregate’s protuberances, and so, the aggregate was initially loose, although subsequent rearrangements made the object denser. This behavior was monitored under different experimental conditions, including varying particle size and beam current. We suggest that the directed particle motion reflects an interplay between the in-plane electric field created by charging of the liquid interface and the polarization of the metallic particles. Our observations underscore electron beam radiation as means to assemble nano-sized metallic objects into 2D hierarchical structures. |
Wednesday, March 7, 2018 3:30PM - 3:42PM |
P54.00006: Understanding the Assembly of Proteins into Sheets with Coarse-Grained Models Irem Altan, Patrick Charbonneau Proteins can self-assemble into a wide variety of structures from amorphous aggregates and crystals to complex virus capsids. Understanding the rich assembly behavior of proteins benefits not only the field of structural biology, but also has applications in biopharmaceutical industry and materials science. Recent studies even suggest that liquid-liquid phase separation of protein droplets within cells might have a biological function. This rich phenomenology is ultimately the product of the short-ranged, anisotropic protein-protein interactions. Using elementary soft matter models to elucidate links between the microscopic properties of proteins and their assembly has met with some success but more complex behaviors have not yet been fully investigated. Here, we investigate the phase behavior of a protein that self-assembles into a single-layer sheet. Understanding this process will help explore possibilities for biomaterial applications. |
Wednesday, March 7, 2018 3:42PM - 3:54PM |
P54.00007: Free Energy Calculation in Hydrocarbon-Functionalized Nanocrystal Superlattices Xun Zha, Alex Travesset I present a calculation of the free energy of nanocrystal superlattices and compare to the resulting free energy using a potential of mean force of pair nanocrystals. The simulations, consist of hydrocarbon-functionalized nanocrystal modeled with a gold-based nanocore, passivated with grafted hydrocarbon ligands. We also discuss the intricacies of the definition of pressure in these systems. Thermodynamic integration of the pressure over volume is applied to obtain free energy. |
Wednesday, March 7, 2018 3:54PM - 4:06PM |
P54.00008: Robust nonequilibrium pathways to microcompartment assembly Grant Rotskoff, Phillip Geissler Bacterial microcompartments, organelle-like, proteinaceous structures found in photosynthetic bacteria, assemble to encapsulate enzymes crucial for carbon fixation. Geometric similarities between microcompartment shells and viral capsids have inspired models of the assembly process that posit that the microcompartment represents a stable, equilibrium arrangement of its constituent proteins. This assumption does not hold, however, for shells that lack intrinsic curvature. I will discuss a microscopic model of the assembly process that is fundamentally nonequilibrium but, nevertheless, can robustly and reliably produce microcompartment structures. The essence of the dynamics of this process can be understood from a minimal mathematical model that resolves the kinetics of the protein shell and its fluctuating, internal cargo. These results highlight experimentally controllable parameters for modulating the size and shape of bacterial microcompartments in the lab. |
Wednesday, March 7, 2018 4:06PM - 4:18PM |
P54.00009: Abstract Withdrawn
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Wednesday, March 7, 2018 4:18PM - 4:30PM |
P54.00010: Hyperuniformity and the universal scaling of spectral densities of a generalized random organization model Zheng Ma, Salvatore Torquato The random organization model provides a means to produce hyperuniform state of matter at criticality. Previous studies focus on models based on monodisperse particles. We generalize the model to account for particle size disparity to investigate to what extent hyperuniformity can be preserved in such multicomponent systems. We begin with binary particles and find that the system is not multihyperuniform (each species is hyperuniform) at criticality but is hyperuniform as a two-phase medium. Specifically, the large-particle configuration is more ordered than the small-particle one. Moreover, when the particle size ratio tends to unity, the former becomes more disordered, while the later becomes more ordered. We show that the critical packing fraction shifts as the composition is varied, and so does the spectral density profile at the critical point. Interestingly, our simulations suggest that the spectral density profiles at the critical point can be rescaled to a single curve up to the first peak, implying a type of universal scaling of the large scale structures of these configurations. Finally, we extend our model to particles with a continuous size distribution. Our results suggest that random organization can be a robust way to produce hyperuniform multicomponent materials. |
Wednesday, March 7, 2018 4:30PM - 4:42PM |
P54.00011: Formation of supported lipid membranes onto solid surfaces: Effect of substrate, lipid, electrolyte and external factors Patricia Losada Perez Artificial lipid membranes are useful model systems for many processes taking place at the cell membrane. When supported into solid materials, they have the potential to generate biosensing platforms of enhanced sensitivity. Moreover, lipid-coated nanostructured materials can be used for controlled drug delivery purposes giving the high drug loading capacity of the nanostructured system, whose release could be modulated by the supported lipid bilayer. In this work, we address different strategies for forming planar lipid layers onto solid surfaces, namely vesicle fusion, surface functionalization by self-assembled monolayers, solvent exchange and interactions with fusing agents [1,2]. Specifically, we focus on the effect of the morphology of the substrate, lipid type, solvent, fusing agent and buffer ionic strength. A versatile surface-sensitive technique quartz crystal microbalance with dissipation (QCM-D) is used, highligthing its usefulness as a tool to monitor phase transitions in solid-supported lipid layers. |
Wednesday, March 7, 2018 4:42PM - 4:54PM |
P54.00012: Unoccupied Interface and Molecular States of Thiol and Dithiol Monolayers on Gold. Jonathan Correa-Puerta, Valeria del Campo, Ricardo Henriquez, Vladimir Esaulov, Hicham Hamoudi, Marcos Flores, Patricio Haberle The electronic structure of self-assembled monolayers (SAMs) formed by thiols of different lengths and dithiol molecules bound to Au(111) has been characterized. Inverse photoemission spectroscopy (IPES) and density functional theory have been used to describe the molecule/Au substrate system. All molecular layers display a clear signal in the IPES data at the edge of the lowest unoccupied system orbital (LUSO), roughly 3 eV above the Fermi level. There is also evidence, in both experiment and calculation, of a finite density of states just below the LUSO edge, which has been recognized as localized at the Au-substrate interface. Regardless of the molecular lengths and in addition to this induced density of interface states, an apparent antibonding Au−S state has been identified in the IPES data for both molecular systems. The main difference between the electronic structures of thiol and dithiol SAMs is a shift in the energy of the antibonding state. The results presented here complements previous reports for alkanethiols and provide new data for the case of aromatic dithiols on Au. |
Wednesday, March 7, 2018 4:54PM - 5:06PM |
P54.00013: Long-range single domain array of sub- 5 nm pattern of dendrimer in a double-sandwich cell Kiok Kwon, kangho Park, Heetae Jung Developing large-area, single domain of organic soft-building blocks such as block copolymers, colloids and dendrimers is one of the most important issues in the materials science and nanotechnology. Owing to their small sizes, complex molecular architectures and high mobility, dendrimer are not well suited for building large area, single domain structures. In the study, we report a simple and general method to create ultra-dense, single domain arrays of dendrimer cylinders over large areas. In this technique, perfectly ordered single domains of cylinders are generated by utilizing double-sandwich system. This discovery is significant in terms of the manipulation of organic soft-building blocks. Firstly, feature sizes of self-assembled dendrimers are much smaller (ca. 4.5 nm diameter) than those generated by existing soft-building blocks. Secondly, it is possible to create macroscopic array of dendrimer columns (>cm scale) by precisely controlling the preparation conditions. Finally, readily prepared dendrimers can be utilized in this process. We believe that the observations made in this effort should serve as the foundation for the design of new routes for bottom-up lithography based on dendrimers. |
Wednesday, March 7, 2018 5:06PM - 5:18PM |
P54.00014: Distortion Controlled Differential Growth Carlos Duque, Christian Santangelo, Bryan Chen Non-Euclidean plates, thin elastic sheets that grow or shrink inhomogeneously, can be thought of surfaces which are unable to completely eliminate in-plane stress. This geometrical frustration forces them to adopt interesting rest configurations as a way of reducing the elastic energy of the system. In this work, we study conformal flattening as a tool for prescribing desirable patterns of nonuniform growth on elastic sheets as a way of making them buckle into a given target shape. In particular, we explore how to design a planar shape that requires the least amount of inhomogeneous growth to buckle into a sphere. We tune the ratio of maximal to minimal area distortion required by modifying where the seams of the final spherical shape will be. We then discuss the optimality of the cuts and make some conjectures about the best possible cuts on arbitrary surfaces. |
Wednesday, March 7, 2018 5:18PM - 5:30PM |
P54.00015: In-pore solidification: from nanoscale origin to mesoscale damage Katerina Ioannidou, Edmond Zhou, Martin Bazant, Roland Pellenq Mechanical and viscoelastic behavior of concrete crucially depends on cement hydrates, the glue of cement. Even more than the atomistic structure, the mesoscale amorphous texture of cement hydrates over hundreds of nanometers plays a crucial role for material properties. Common degradation mechanisms of concrete are Freeze-Thaw, Alkali-silica-Reaction and Delayed Ettringite Formation. These damage mechanisms occur under different thermodynamic conditions, nevertheless with necessary condition the suffiient saturation of cement's pore network with water. The damage occurs when a new phase solidifies inside the pore network of cement paste. In this talk, I present a unified computational framework that links the nanoscale origin of in pore crystallization to mesoscale damage in cement. Grand Canonical Monte Carlo and Molecular Dynamics simulations of in-pore crystallization were performed in the realistic structure and pore network of cement hydrates [1]. The results provide a new insight on how in-pore solidification creates cracks in cement paste and suggest solutions to mitigate the problem. 1. Ioannidou K. et al, The mesoscale texture of cement hydrates, Proceedings of National Academy of Science USA, 113 (8), 2029-2034 (2016) |
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