Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session E07: Self-and Directed Assembly (Equilibrium and Non-equilibrium) ILive
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Sponsoring Units: DSOFT Chair: Jessica Sun, Harvard University Room: 07 |
Tuesday, March 16, 2021 8:00AM - 8:12AM Not Participating |
E07.00001: Landau theories of Frank-Kasper spherical packing phases Sarah Dawson, Anchang Shi The Frank-Kasper phases are a group of complex spherical packing phases, a subset of which have been discovered in a wide range of soft condensed matter systems. Motivated by this universality, we investigated the (meta-)stability of these phases across a family of phase field crystal models - Landau theories that describe the formation of crystalline phases. This work illuminates the interplay between short and long-range interactions that influence the formation of these phases in many different systems. In this talk I will discuss the general mechanisms that are found to promote the stability of these complex phases. I will also demonstrate how these mechanisms relate to the microscopic parameters of a diblock-copolymer system in which several Frank-Kasper phases appear. |
Tuesday, March 16, 2021 8:12AM - 8:24AM Live |
E07.00002: Sticky sphere packings on a cone Abigail Plummer, Jessica Sun, Vinothan N Manoharan, David R. Nelson Inspired by experiments on the self-assembly of colloidal spheres on the surface of a cone, we use a greedy packing algorithm with extremely short-range attractive interactions to study how crystal growth is affected by both surface geometry and the nature of nucleation events. Since local crystal packings are unaware of the delta function of Gaussian curvature at the apex until they have encircled the cone, an initial seed composed of a ring of particles at a commensurate height leads to very different structures than a three-particle triangular seed, for example. We characterize the distribution of defects (sites with coordination number different from six) for a variety of initial seed types and locations, focusing on commensurate cone angles at which defect-free growth is possible and comparing crystallization on cones to the well-studied case of crystallization on spheres. We will discuss how our results can be used to guide experimental design and shed light on observed motifs such as disordered regions close to the cone apex and wedge-shaped voids far from the apex. |
Tuesday, March 16, 2021 8:24AM - 8:36AM Live |
E07.00003: Colloidal crystallization on a cone Jessica Sun, Nabila Tanjeem, David R. Nelson, Vinothan N Manoharan We study the self-assembly of colloidal spheres on the surface of a cone. For a flat surface with zero Gaussian curvature, colloidal monolayers form hexagonal crystals. However, a cone has zero Gaussian curvature everywhere except its apex -- a delta function of positive Gaussian curvature, which introduces a novel source of geometrical frustration for colloidal crystallization. |
Tuesday, March 16, 2021 8:36AM - 8:48AM Live |
E07.00004: Driven lock-and-key colloidal particles for directed assembly Tianyi Yao, Yimin Luo, Daniel A Beller, Francesca Serra, Edward Steager, Kathleen Joan Stebe In nematic lock-and-key interactions, as in biology, colloidal particles interact preferentially with particular sites. Nematic lock-and-key recognition, studied previously near wavy walls, relies on particles interacting elastically with curved boundaries to minimize their elastic energy. We extend this concept by introducing driven lock-and-key particles, inherently topologically distinct from the wavy wall. The driven lock-and-key particle is a multi-armed structure with curvature designed for multiple modes of interaction with passive colloidal particles including (i) lock-and-key interactions in a well with a hyperbolic hedgehog companion defect pointing outwards, (ii) lock-and-key interactions on a curved arm with companion defect pointing inwards, and (iii) disclination loop-dipole chaining. The lock-and-key particle’s design also promotes the formation of a disclination loop whose location can be managed by controlling the particle’s orientation, and whose stability can be manipulated for controlled release and for introduction of non-equilibrium structures for assembly. The mobility of the lock-and-key colloid provides new degrees of freedom for combined bottom up and top down materials assembly. |
Tuesday, March 16, 2021 8:48AM - 9:00AM Live |
E07.00005: Assembling pseudo-trimeric patchy colloids confined to a surface Piet JM Swinkels, Zhe Gong, Stefano Sacanna, Peter Schall 2D materials have attracted great interest in the past decades. For instance, graphene has exotic mechanical and electronic properties that are not typically found in bulk materials. Unfortunately, the assembly of 2D materials remains hard to study, as direct observation is challenging. However, by using patchy particles we can mimic atomic 2D structures using colloids, which can be studied in real time using microscopy. |
Tuesday, March 16, 2021 9:00AM - 9:12AM Live |
E07.00006: Structure formation of colloids via capillarity at curved fluid interfaces alismari read, Sreeja Kutti Kandy, Iris B Liu, Ravi Radhakrishnan, Kathleen Joan Stebe Colloidal particles accumulate and organize at fluid interfaces via capillary interactions. We study pair interactions and structure formation around spherical particles with pinned contact lines. Particles attract to apparent contact and organize in near trapped structures that reflect the underlying curvature field. We have derived pair potentials to describe these interactions. The particles distort the surrounding interface in which we calculate the distortion area and hence capillary energy around a colloid and its dependence on proximity to neighbors and on the underlying interface curvature. Dimer formation alignment with respect to principal axes and dynamics compare favorably to prediction. We use this pair potential in Monte Carlo simulations to compare to the structures formed. Extensions to address elongated particles are discussed. |
Tuesday, March 16, 2021 9:12AM - 9:24AM Live |
E07.00007: Randomness in self-assembled colloidal crystals can widen photonic band gaps through particle shape and internal structure Duanduan Wan, Sharon C Glotzer Using computer simulations, we explore how thermal noise-induced randomness in a self-assembled photonic crystal affects its photonic band gaps (PBGs). We consider a two-dimensional photonic crystal comprised of a self-assembled array of parallel dielectric hard rods of infinite length with circular or square cross section. We find the PBGs can exist over a large range of intermediate packing densities. Counterintuitively, the largest band gap does not always appear at the packing density where the crystal is most ordered, despite the randomness inherent in any self-assembled structure. By considering hollow rods, we find the band gap of transverse electric (TE) modes can be substantially increased while that of TM modes show no obvious improvement over solid rods. Our study suggests that particle shape and internal structure can be used to engineer the PBG of a self-assembled system despite the positional and orientational randomness arising from thermal noise. |
Tuesday, March 16, 2021 9:24AM - 9:36AM Live |
E07.00008: Computational Reverse-Engineering Analysis for Scattering Experiments of Assembled Binary Colloidal Particle Mixtures Christian Heil, Arthi Jayaraman Assembly of nanoparticle mixtures is widely used to precisely design materials with controlled optical properties. This process often requires structural characterization to link the assembled structure with the macroscopic property of interest. Many researchers utilize small angle neutron scattering (SANS) to analyze the nanoparticle assembly. Once the scattering profile, I(q), is obtained, the general practice is to use analytical models to interpret the scattering profile and produce the real space structure. However, the choice of the appropriate model for fitting the scattering profile is not always trivial, particularly for close-packed nanoparticles. To overcome this limitation, we present our recently developed evolutionary algorithm-based method to analyze the structure of binary nanoparticle assemblies in both spherical and cubic geometries from the scattering profiles obtained from SANS of nanoparticle assemblies. The method requires the I(q), particle composition, and particle size distributions as inputs and outputs the real-space structure whose scattering profile most closely matches the experimental scattering profile. Our approach resolves the local packing around the nanoparticles as well as domain sizes for varying extents of inter-particle segregation/mixing. |
Tuesday, March 16, 2021 9:36AM - 9:48AM Live |
E07.00009: Physics and Evolution of Catalysis Maitane Muñoz Basagoiti, Olivier Rivoire, Zorana Zeravcic Catalysis is one of the most remarkable properties matter can exhibit: the ability to accelerate a reaction without being consumed in the process. Nature offers a vast collection of prominent catalysts, enzymes, whose high selectivity and transition state (TS) complementarity constitute key design principles for catalytic matter. Additionally, efficient catalysts must optimize the trade-off between strong substrate binding and product release (Sabatier's principle) while stabilizing the TS. Such trade-offs limit the set of possible catalyst designs and their efficiencies via non-trivial geometrical and physical constraints. Despite outstanding progress in the design of de novo catalysts [1], we do not fully understand the fundamental principles that lead to the emergence of catalytic activity. In our work, we search for the physical and geometrical elements at the origin of catalytic activity in matter using a model system of DNA-coated colloids. Combining coarse-grained computer simulations with theory, we build structures of increasing complexity to identify the simplest structure with the potential to cleave bonds. |
Tuesday, March 16, 2021 9:48AM - 10:00AM Live |
E07.00010: Colloidal Diamond Photonic Bands Johnathon Gales, Mingxin He, David Pine We have designed a new set of patchy tetrahedral colloidal clusters that can self-assemble into a diamond lattice. Like the conventional colloidal diamond of spheres, we find that the diamond lattice of clusters we have assembled exhibits a strong photonic band gap for appropriate parameters. Inverting the lattice leads to a particularly strong band gap after optimizing a few geometric parameters. We also provide a method for achieving the inverse lattice. |
Tuesday, March 16, 2021 10:00AM - 10:12AM Live |
E07.00011: Controlling Stratification of Colloids Using a Mixed Binary Solvent Binghan Liu, Gary Grest, Shengfeng Cheng Stratification in drying suspensions of polydisperse colloids has recently attracted attention as it may lead to a facile method of fabricating layered coatings and thin films. To make it technologically viable, it is important to control the structures that result from the drying process. With large scale molecular dynamics simulations, we show that stratification of suspended colloids can be controlled by using a mixed binary solvent with each component possessing a different relative volatility. When the solvent evaporates, the two components evaporate at different rates and exhibit opposite concentration gradients in the solution phase, with the less volatile component enriched at the evaporating surface. For a binary colloidal mixture suspended in the mixed solvent with each colloidal species having opposite preferences to the two solvent components, the two colloids naturally stratify with the one on top that is more strongly coupled to the less volatile solvent component, even if the two colloidal species have the same size and interparticle interaction. Our results thus reveal a useful method of controlling stratification that can be easily implemented and scaled up. |
Tuesday, March 16, 2021 10:12AM - 10:24AM Live |
E07.00012: Self-Assembly Kinetics of Colloidal Liquid Crystals Louise Head, Tyler N Shendruk Nematic colloids’ ability to interact through topological defects and form self-assembled structures provides a pathway for engineering novel soft nanotechnology. In this work, we employ a nematic Multi-Particle Collision Dynamics (MPCD) algorithm to simulate the self-assembly of such structures. Since MPCD-based algorithms intrinsically contain fluid flow and stochastic thermal noise, we are able to predict the kinetics of colloid-colloid interactions via the probability of passing through metastable configurations and rate of successful self-assembly. Our results reproduce the equilibrium zig-zag and linear-chained colloidal structures observed in experiments. By studying the influence of anchoring on the surface of the colloid, we show that defects play a crucial role on the creation of equilibrium structures and kinetic pathways. Our findings map the underlying mechanisms and timescales involved in the self-assembly process, indicating design principles for engineering rapidly assembling structures. |
Tuesday, March 16, 2021 10:24AM - 10:36AM Live |
E07.00013: Anisotropic phononic bandgaps in colloidal crystals of dumbbell-shaped nanoparticles Hojin Kim, Eric M Furst, Zuyuan Wang, George Fytas, Bahram Djafari-Rouhani Nanoparticles are excellent building blocks for creating crystalline structures. Using an electric-filed-directed self-assembly technique, we fabricate colloidal crystals of dumbbell-shaped nanoparticles. The base-centered monoclinic lattice structure exhibits phononic bandgaps due to the periodicity of the elastic properties. The phonon dispersion recorded by Brillouin light spectroscopy (BLS) reveals direction-dependent Bragg gaps resulting from the anisotropic lattice structure. In addition, a hybridization bandgap robust to disorder is also observed in the disordered films of three different dumbbell-shape nanoparticles. We present theoretical calculations of the BLS-measured particle vibrational eigenmode spectra and the band structure of the phononic crystal. The calculation results elucidate the origin of the hybridization bandgap and its relation to the particle vibrational eigenmodes. |
Tuesday, March 16, 2021 10:36AM - 10:48AM Live |
E07.00014: Motile Crystals in Active Colloids Amir Nourhani, Seyed Amin Nabavizadeh We present the collective dynamics of active colloids capable of self-assembly into a polar motile crystal. We study the effect of system parameters on the polar order-disorder transition. Within a motile polar phase, we discuss how the translational and orientational symmetry and order change in the parameter space. The length scale of the local order shows the dependence of the interparticle interactions and their density. We investigate the effect of noise on the phase diagram and polar order. |
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