Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session C17: Self-Assembly I: Nanoparticles and Colloids |
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Sponsoring Units: GSOFT Chair: Greg van Anders, University of Michigan Room: 276 |
Monday, March 13, 2017 2:30PM - 2:42PM |
C17.00001: Entropically Stabilized Colloidal Crystals Hold Entropy in Collective Modes James Antonaglia, Greg van Anders, Sharon Glotzer Ordered structures can be stabilized by entropy if the system has more ordered microstates available than disordered ones. However, ``locating" the entropy in an ordered system is challenging because entropic ordering is necessarily a collective effort emerging from the interactions of large numbers of particles. Yet, we can characterize these crystals using simple traditional tools, because entropically stabilized crystals exhibit collective motion and effective stiffness. For a two-dimensional system of hard hexagons, we calculate the dispersion relations of both vibrational and librational collective modes. We find the librational mode is gapped, and the gap provides an emergent, macroscopic, and density-dependent length scale. We quantify the entropic contribution of each collective mode and find that below this length scale, the dominant entropic contributions are librational, and above this length scale, vibrations dominate. This length scale diverges in the high-density limit, so entropy is found predominantly in libration near dense packing. [Preview Abstract] |
Monday, March 13, 2017 2:42PM - 2:54PM |
C17.00002: Insights into Inverse Materials Design from Phase Transitions in Shape Space Rose Cersonsky, Greg van Anders, Paul M. Dodd, Sharon C. Glotzer In designing new materials for synthesis, the inverse materials design approach posits that, given a structure, we can predict a building block optimized for self- assembly. How does that building block change as pressure is varied to maintain the same crystal structure? We address this question for entropically stabilized colloidal crystals by working in a generalized statistical thermodynamic ensemble where an alchemical potential variable is fixed and its conjugate variable, particle shape, is allowed to fluctuate. We show that there are multiple regions of shape behavior and phase transitions in shape space between these regions. Furthermore, while past literature has looked towards packing arguments for proposing shape-filling candidate building blocks for structure formation, we show that even at very high pressures, a structure will attain lowest free energy by modifying these space-filling shapes. [Preview Abstract] |
Monday, March 13, 2017 2:54PM - 3:06PM |
C17.00003: Structure and Symmetry of Ground States of Colloidal Clusters Ellen D Klein, W. Benjamin Rogers, Vinothan N. Manoharan We experimentally study colloidal clusters consisting of 6 to 100 spherical particles bound together with short range, DNA-mediated attractions. These clusters are a model system for understanding colloidal self-assembly and dynamics, since the positions and motion of all particles can be observed in real space. For 10 particles and fewer, the ground states are degenerate, and, as shown in previous work [1], the probabilities of observing specific clusters depend primarily on their rotational entropy, which is determined by symmetry. Thus less symmetric structures are more frequently observed. However, for larger numbers of particles the ground states appear to be subsets of close-packed lattices, which tend to have higher symmetry. To understand how this transition occurs as a function of the number of particles, we coat colloidal particles with complementary DNA strands that induce a short-range, temperature-dependent interparticle attraction. We then assemble and anneal an ensemble of clusters with 10 or more particles. We characterize the number of apparent ground states, their symmetries, and their probabilities as a function of the size of the cluster using confocal microscopy. 1. The Free-Energy Landscape of Clusters of Attractive Hard Spheres, G. Meng, et. al. Science [Preview Abstract] |
Monday, March 13, 2017 3:06PM - 3:18PM |
C17.00004: Self-assembly of patchy particles: role of patch number Debra Audus, Francis Starr, Jack Douglas The canonical model of patchy particles, a hard sphere decorated with attractive patches, has been used to describe solutions of small globular proteins, as well as micron-size particles with attractive patches. Previously, we extended the canonical model by introducing an isotropic, attractive interaction. Using Monte Carlo simulations and an analytic, Wertheim based mean-field theory, we found that although the location of the self-assembly transition lines were dependent on the isotropic interaction strength, the nature of the self-assembly was unaffected. Specifically, we developed a formalism to describe a master curve for the average molecular mass by combining Flory-Stockmayer theory with an analysis of the thermodynamics of association. We also found that the self-assembled clusters have a fractal dimension of two; this value is consistent with randomly branched polymers swollen by repulsive self-excluded volume interactions. Extending this work, we consider the role of patch number and find that the formalism still holds but becomes dependent on the number of patches. We explore the experimental implications of this finding and investigate the role of patch number on cluster shape. [Preview Abstract] |
Monday, March 13, 2017 3:18PM - 3:30PM |
C17.00005: Plastic crystal to crystal transition in mesoscopic colloidal plates Binbin Luo, Zixuan Wu, Ahyoung Kim, Zihao Ou, Juyeong Kim, Qian Chen We introduce mesoscopic colloidal plates as a new type of building blocks that integrate micron-sized plate edge length to facilitate optical microscopy imaging and nano-sized thickness to allow fast diffusion and fluctuation dynamics comparable to nanoscale objects. The mesoscopic nature of plate and interaction length scales together complicate the free energy landscape for the self-assembly of plates. We observe experimentally the formation of a three-dimensional closely-packed honeycomb lattice, and more notably, the relaxation of that lattice upon expansion into a positionally ordered and orientationally disordered plastic crystal. Direct optical microscopy imaging and single-particle tracking allow us to elucidate the entropy origin of the plastic crystal as well as the lattice relaxation. [Preview Abstract] |
Monday, March 13, 2017 3:30PM - 3:42PM |
C17.00006: DNA Origami Wrapped Colloids for Programmable Self-Assembly Xiaojin He, Matan Yah Ben Zion, Ruojie Sha, Yin Zhang, Nadrian Seeman, Paul Chaikin Here we demonstrate a strategy for functionalizing colloids to realize fully addressable, oriented binding sites on the colloidal surface using DNA origami belts as cages to wrap over colloidal particles. DNA origami, as a print-board, provides great directionality and flexibility in assembling particles. In order to match the microscopic particles, we first assemble DNA origami tiles into micro-sized DNA origami linear or cross-shape belts. Short single-stranded handles, decorated on one side of the DNA origami belt, can hybridize to complementary strands coating on the particle and wrap around the particle. By placing sticky ends on different positions on the other side of the DNA origami belts, we can assemble the DNA origami wrapped colloids with complementary particles into finite clusters with different symmetries or arbitrary configurations. These DNA origami wrapped colloids can also serve as building units to directionally and specifically organize themselves into higher-ordered architectures via origami-origami interactions. [Preview Abstract] |
Monday, March 13, 2017 3:42PM - 3:54PM |
C17.00007: Amplified Self-replication of DNA Origami Nanostructures through Multi-cycle Fast-annealing Process Feng Zhou, Rebecca Zhuo, Xiaojin He, Ruojie Sha, Nadrian Seeman, Paul Chaikin We have developed a non-biological self-replication process using templated reversible association of components and irreversible linking with annealing and UV cycles. The current method requires a long annealing time, up to several days, to achieve the specific self-assembly of DNA nanostructures. In this work, we accomplished the self-replication with a shorter time and smaller replication rate per cycle. By decreasing the ramping time, we obtained the comparable replication yield within 90 min. Systematic studies show that the temperature and annealing time play essential roles in the self-replication process. In this manner, we can amplify the self-replication process to a factor of 20 by increasing the number of cycles within the same amount of time. [Preview Abstract] |
Monday, March 13, 2017 3:54PM - 4:06PM |
C17.00008: Characterizing the dynamics of phase transitions of DNA-grafted colloidal particles Alexander Hensley, W. Benjamin Rogers Grafting DNA onto colloidal particles can `program' them with information that tells them exactly how to self-assemble. Advances in our understanding of these specific interactions have enabled the assembly of many crystal phases and could be extended to the assembly of prescribed structures. However, structure is just one piece of the puzzle; self-assembly describes a phase transition between a disordered state and an ordered state, or a pathway on a phase diagram. In this talk I present an experimental study of the dynamics of these phase transitions in suspensions of polystyrene particles grafted with single-stranded DNA. Hybridization of complementary DNA grafted to particles, as well as binding of free DNA strands in solution, drives colloids to aggregate in a tunable manner. By varying the concentration of free strands in solution, colloid volume fraction, and interaction strength, we explore the roles of the pair interaction and binding kinetics on the dynamics of assembly. Using differential dynamic microscopy we extract the changing hydrodynamic size of clusters of colloids as the system evolves with time. These experiments could provide useful insights into dynamics of phase transitions, such as the presence and heights of barriers to assembly. [Preview Abstract] |
Monday, March 13, 2017 4:06PM - 4:18PM |
C17.00009: Self-Assembly of Janus Colloids under Flow Arash Nikoubashman Functionalized colloids have attracted an increasing amount of attention due to their inherent capacity to self-assemble into complex hierarchical structures, such as micelles, vesicles, or lamellar phases. The majority of previous studies has focused on the equilibrium behavior of these systems in the bulk, where self-assembly occurs as the result of the interplay between the particle interactions and diffusive transport. However, equilibrium is often never reached in many biological and physical systems due to external fields or dynamic arrest. To study these non-equilibrium situations, we performed molecular dynamics simulations of Janus colloids under flow. At rest, the Janus colloids spontaneously assembled into spherical micelles. Under strong shear, they broke up into smaller fragments and isolated particles. Nonetheless, an intermediate shear rate regime was found where the growth of the micelles was favored. The simulations revealed that clusters composed of either 6 or 13 particles were most stable towards shear due to the high geometric symmetry of these aggregates. Furthermore, a sizable fraction of free particles and small clusters with 3 and 4 members was found at the walls when the channel was made out of a comparably solvophobic material as the colloids. [Preview Abstract] |
Monday, March 13, 2017 4:18PM - 4:30PM |
C17.00010: Self-assembly of colloids under periodically-reversed sedimentation. Coline Bretz, Jean Baudry, Denis Bartolo, Arjun Yodh, Remi Dreyfus Hyperuniform materials have attracted increasing interest over the past decade due to their potential exciting photonic properties. Motivated by the exploration of novel ways of assembling hyperuniform materials, we are performing an echo protocol on micrometer-sized colloidal particles under sedimentation in a Hele-Shaw cell. Using a combination of static light scattering, differential dynamics microscopy and direct imaging, we will show how we can follow the structural and dynamical changes of these systems and characterize their hyperuniformity. [Preview Abstract] |
Monday, March 13, 2017 4:30PM - 4:42PM |
C17.00011: Tunable Gaussian modulus directs catenoid formation from 2D colloidal membranes Andrew Balchunas, Prerna Sharma, Zvonimir Dogic Monodisperse, chiral rod-like particles assemble into one rod-length thick smectic layers, named colloidal membranes, when mixed with a non-adsorbing depleting polymer. It has been shown, using polarization microscopy, that a membrane assembled from rods of similar chirality will exhibit a uniform twist along its edge, while the bulk remains untwisted. When rods of opposite chiralities are mixed, a membrane may have the edge twist of either handedness. This resolves itself as a membrane with scalloped edges, where two adjacent lobes exhibit opposite handedness. As a result, the membrane becomes a 3 dimensional structure. The energetic penalty for creating scalloped edges is compensated by the deformation energy due to Gaussian curvature. Since the overall mean curvature is zero but the structure exhibits an overall negative Gaussian curvature, the Gaussian modulus for a colloidal membrane must be positive to minimize its energy. In this research, we show that the Gaussian modulus can be tuned using a system of two rod types with different lengths and similar handedness. Using this system, self-assembly can be directed to form flat membranes, saddles, and catenoids by changing the Gaussian modulus. The magnitude of the modulus is controlled by varying the fraction of short to long rods, and depletant concentration. [Preview Abstract] |
Monday, March 13, 2017 4:42PM - 4:54PM |
C17.00012: Programmable Self-assembly of Hydrocarbon-capped Nanoparticles: Role of Chain Conformations Curt Waltmann, Nathan Horst, Alex Travesset Nanoparticle superlattices (NPS), i.e. crystalline arrangements of nanoparticles, are materials with fascinating structures, which in many cases are not possible to attain from simple atoms or molecules. They also span a wide range of possible applications such as metamaterials, new energy sources, catalysis, and many others. In this talk, we present a theoretical and computational description of the self-assembly of nanoparticles with hydrocarbons as capping ligands. Usually, these systems have been described with hard sphere packing models. In this talk, we show that the conformations of the hydrocarbon chains play a fundamental role in determining the equilibrium phases, including and especially in binary systems. [Preview Abstract] |
Monday, March 13, 2017 4:54PM - 5:06PM |
C17.00013: Flash NanoPrecipitation as a scalable platform for the production of structured and hybrid nanocolloids Victoria Lee, Chris Sosa, Rui Liu, Robert Prud'homme, Rodney Priestley Geometrically-structured polymer nanocolloids have been widely investigated for their unique properties, which are derived from their anisotropy. Decoration with inorganic nanoparticles in a controlled manner could induce another level of functionality into structured nanocolloids that could enable applications in fields such as re-writeable electronics and biphasic catalysis. Here, Flash NanoPrecipitation (FNP) is demonstrated as a one-step and scalable process platform to manufacture hybrid polymer-inorganic nanocolloids in which one phase is selectively decorated with a metal nanocatalyst by tuning the interactions between the feed ingredients. For instance, by modifying polymer end-group functionality, we are able to tune the location of the metal nanocatalyst, including placement at the Janus nanocolloid circumference. Moreover, the addition of surfactant to the system is shown to transform the Janus nanocolloid structure from spherical to dumbbell or snowman while still maintaining control over nanocatalyst location. Considering the flexibility and continuous nature of the FNP process, it offers an industrial-scale platform for manufacturing of nanomaterials that are anticipated to impact many technologies. [Preview Abstract] |
Monday, March 13, 2017 5:06PM - 5:18PM |
C17.00014: The Role of Ligand in the Structural Properties of Self-Assembled Nanoparticle Films Melanie Calabro, Sean Griesemer, Quan Peiyu, Wei Bu, Stuart A. Rice, Binhua Lin Thiol-functionalized self-assembled films of gold nanoparticles (NPs) at the air/water interface assemble into monolayers with particular properties as a function of thiol concentration and chain length. Previous studies have shown that such films exhibit diverse mechanical responses as a function of these parameters, but a conception of what the responsible underlying structure is has not been elucidated. We use grazing incidence X-ray diffraction (GIXD) to perform a comprehensive study of the interparticle spacing and correlation length of our films for a range of thiol concentrations, and for several different thiol chain lengths. Further, we provide a novel interpretation of how the nanometer-scale structure of our thiol-ligated NP films evolves with different thiol parameters, based on an understanding of the process and controlling parameters of thiol adsorption on to the gold itself. Our experiments and interpretation reveal that even at traditionally considered ``high'' thiol concentrations, gold NPs are not fully covered by a monolayer of ligands, thus allowing thiol molecules freedom to crumple and/or interdigitate and thereby enabling the ligand-based interactions that contribute to the observed unusual strength and mechanical properties of the films. [Preview Abstract] |
Monday, March 13, 2017 5:18PM - 5:30PM |
C17.00015: Hyperuniform Disordered photonic bandgap materials, from 2D to 3D, and their applications Weining Man, Marian Florescu, Shervin Sahba, Steven Sellers Recently, hyperuniform disordered systems attracted increasing attention due to their unique physical properties and the potential possibilities of self-assembling them. We had introduced a class of 2D hyperuniform disordered (HUD) photonic bandgap (PBG) materials enabled by a novel constrained optimization method for engineering the material's isotropic photonic bandgap. The intrinsic isotropy in these disordered structures is an inherent advantage associated with the lack of crystalline order, offering unprecedented freedom for functional defect design impossible to achieve in photonic crystals. Beyond our previous experimental work using macroscopic samples with microwave radiation, we demonstrated functional devices based on submicron-scale planar hyperuniform disordered PBG structures further highlight their ability to serve as highly compact, flexible and energy-efficient platforms for photonic integrated circuits. We further extended the design, fabrication, and characterization of the disordered photonic system into 3D. We also identify local self-uniformity as a novel measure of a disordered network's internal structural similarity, which we found crucial for photonic band gap formation. [Preview Abstract] |
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