Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session M25: Self- and Directed Assembly IIRecordings Available
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Sponsoring Units: DSOFT Chair: Chris Santangelo, Syracuse University Room: McCormick Place W-187A |
Wednesday, March 16, 2022 8:00AM - 8:12AM |
M25.00001: Monte Carlo simulations of heteroaggregation of colloidal plastic particles Bahadir Rusen Argun, Antonia Statt Nano- and microplastics are an emergent threat for human health and the environment, especially for marine and riverine habitats. To assess the influence on the ecosystem and provide possible solutions, it is necessary to investigate the "fate" of nano plastics in environmental conditions. However, the polydispersity in size, and shape of nano plastics, low concentration levels, different chemistries and the various environmental conditions make it difficult to predict how those particles behave in the environment. To address this challenge, we perform Monte Carlo Simulations and aim to understand the effect of size, shape and solvent conditions on phase behavior of nanoplastic particles. Our studies focus on the heteroaggregation of nanoplastics of different shapes with suspended particulate matter (SPM) that is ubiquitous in natural waters. We mimic different solvent conditions (salt concentration and valency) and SPM surface chemistries by using a generic pair potential with short-range attraction and long-range repulsion.We aim to gain insights into the stability, size and structure of resulting aggregates of nanoplastics in different environmental settings. |
Wednesday, March 16, 2022 8:12AM - 8:24AM |
M25.00002: Using Symmetry to Direct Two-dimensional Colloidal Crystal Self-assembly Nathan A Mahynski, Vincent K Shen We investigate self-assembling rings that can template the organization of an arbitrary colloidal unit into any desired periodic symmetry at a planar interface. By viewing this as a tiling problem, we illustrate how the shape and chemical functionality of these rings may be derived from symmetry, rather than through iterative computational methods such as inverse design. Moreover, we illustrate how these features are reflected by their orbifold symbol, which provides a natural language to express them. We performed molecular dynamics simulations to observe the self-assembly of these rings and found 5 different characteristics which could be easily rationalized based on their orbifold. These include systems which (1) undergo chiral phase separation, (2) are addressably complex, (3) exhibit self-limiting growth into clusters, (4) may form a smectic phase, and (5) those from symmetry groups which allow one to select rings which exhibit different self-assembly behaviors. We discuss how a ring's curvature plays an integral role in achieving correct self-assembly, in practice, and we illustrate how to derive these ring shapes. This provides a method for patterning colloidal systems at interfaces without explicitly programming this information onto the colloidal unit itself. |
Wednesday, March 16, 2022 8:24AM - 8:36AM |
M25.00003: Diffusionless rotator-crystal transitions in colloidal truncated cubes: lattice distortion and kinetic pathways Abhishek K Sharma, Fernando A Escobedo Rotationally symmetric, hard faceted particles can form rotator mesophases with particles arranged on a lattice with significant orientational disorder. We study the mechanism of entropy-driven rotator-crystal transitions in such systems focusing on the role of lattice distortion. Monte Carlo simulations are conducted for two selected truncations of cubes: s=0.527 (TC52) & s=0.572 (TC57) that are known to form rotator phases. These systems are chosen because the rotator & crystal lattices are identical for TC57 but dissimilar for TC52. While TC57 rotator phase successfully transitions to crystal upon compression, the TC52 rotator phase transitions to an orientational salt intermediate with particles forming alternating layers of opposite orientations. The salt lattice is much closer to the rotator than the crystal. Thus, the penalty to accommodate distortion steers the TC52 rotator phase along a pathway where the salt forms before the crystal, at least for moderate supersaturations. We develop order parameters to track rotator-crystal & rotator-salt transitions to calculate the associated free energy barriers via umbrella sampling. This work paves the way for further study of diffusionless transformations in nanoparticles & highlights the role of lattice-distortion on kinetics. |
Wednesday, March 16, 2022 8:36AM - 8:48AM |
M25.00004: Ostwald Rule of Stages of Close-packed Spherical Colloids Sangwoo Lee, Liwen Chen The initial structure of nucleating and growing crystal domains of equal spherical colloids has been reported fluctuation-induced randomly-stacked layers of two-dimensional hexagonal close-packed (RHCP) arrays until the crystal domains adopt face-centered cubic (FCC) symmetry with sufficiently large translational entropic gains. Contrary to this belief, our experimental investigation of metastable close-packed structures of soft micellar colloids reveals that the initial close-packed structure at the nucleation step is close to hexagonally close-packed (HCP) structures, gradually transforming to FCC through intermediate RHCP states as the crystal grains grow. This observation suggests that growing domains of a new phase pass through a series of thermodynamic states over a temperature or density pathway in the phase space. |
Wednesday, March 16, 2022 8:48AM - 9:00AM |
M25.00005: Directing Particle Assembly with Light and Sound Dustin P Kleckner, Dominique Davenport, Nicholas St. Clair It is well known that focussed beams of light or sound can be used to trap individual particles (i.e. optical or acoustic tweezers). Less well known is that light and sound can also be used to create forces between multiple particles via "binding" effects. In principle, these binding effects could be used to program the assembly of colloidal structures, but there are significant practical barriers to doing so. I will discuss our experimental, theoretical, and numerical efforts aimed at better understanding optical and acoustic binding effects, as well as the challenges which remain. |
Wednesday, March 16, 2022 9:00AM - 9:12AM |
M25.00006: Colloidal Self-Organization using Light Dominique Davenport, Nicholas St. Clair, Dustin P Kleckner Light can be used to generate inter-particle interactions between colloidal particles. Through mutual scattering of the light, two particles can become optically-bound and multi-particle systems can self-organize into optically-bound matter. We find that it is in the formation of optically-bound matter that unexpected dynamics are observed. Underlying the emergent dynamics, such as the formation of quasi-stable and driven structures, is the complexity of the interaction due to a feedback mechanism that is not found in most self-assembly interactions. We share what we are learning about the feedback mechanism and discuss ways in which the complexity of the self-organization can be tuned. |
Wednesday, March 16, 2022 9:12AM - 9:24AM |
M25.00007: Acoustically Mediated Self-Organization Nicholas St Clair, Dominique Davenport, Dustin P Kleckner, Arnold Kim Acoustic fields can produce trapping forces on single particles, analogous to the optical trapping effect. However, sound can also induce forces between particles due to multiple scattering events. This inter-particle force -- which we refer to as acoustic binding -- can be used to guide the long-range assembly of particles on wavelength scales. Here we describe how numerical modelling is used to study these forces and the structures that they produce. We will also discuss some unexpected behavior which arises as a consequence of the non-linear and non-pairwise nature of these interaction forces. |
Wednesday, March 16, 2022 9:24AM - 9:36AM |
M25.00008: A two-step method to engineer the self-assembly of large colloidal crystals using DNA-programmed interactions Alexander Hensley, William M Jacobs, William B Rogers Recent work has shown that a wide variety of crystalline structures can be self-assembled from DNA-coated colloids. However, making large, monodisperse, single crystals with high yield remains an unsolved challenge despite it being a crucial step in moving colloidal self-assembly from fundamental science to practical applications, like the assembly of photonic or plasmonic devices. In this talk, I will present a simple two-step method for making large single crystals from DNA-coated colloids, which decouples nucleation and growth. First, we use microfluidics to create an emulsion of droplets filled with DNA-coated colloids and slowly lower the temperature, leading to the nucleation and growth of a single colloidal crystal in each droplet. The size of these crystals is dictated by the number of particles contained in each droplet and can therefore be finely tuned. Next, we recover the single crystals by breaking the emulsion and use them as seeds to grow much larger single crystals than have been previously possible, including single crystals with millions of particles that can be seen by the naked eye. |
Wednesday, March 16, 2022 9:36AM - 9:48AM |
M25.00009: Design rules of two-dimensional colloidomer folding Maitane Muñoz Basagoiti, Angus McMullen, Zorana Zeravcic, Jasna Brujic Folding of a protein into a final structure is a reversible process governed by the amino-acid sequence of the protein backbone. Similarly, through the control of particle-particle interactions, colloidomers — flexible chains of colloidal particles [1] — can assemble into well-defined structures, allowing us to exploit folding as a design strategy for self-assembly. Here we study the effect of switching on/off nearest-neighbor and next-nearest neighbor interactions on the folding of a colloidomer chain. Inspired by proteins, we develop an algorithm that selects unique folds of a particulate chain in two dimensions by searching in sequence, particle species and interaction space [2]. For an alternate sequence of two particle species, i.e., ABABAB…, we find 10 unique solutions for chain sizes ranging from N = 6 to N = 12 particles. We show that some of the solutions rely on the hierarchy of interactions. We use experiments and simulations to verify the existence of these solutions and characterize their yield. Our study suggests design rules for interactions along the chain leading to assembly of structures with a particular geometrical motif. This strategy opens the door to the design of novel supra-colloidal building blocks. |
Wednesday, March 16, 2022 9:48AM - 10:00AM |
M25.00010: Self-assembly of Colloidal Hematite in Evaporating Droplets Sarah N Schyck, Janne-Mieke Meijer, Max Schelling, Andrei V Petukhov, Laura Rossi The self-assembly of materials by utilizing the inherent directionality of the constituent particles is of both practical and fundamental interest. By employing evaporation assisted self-assembly, we assemble micro-sized magnetic and non-magnetic superball particles into ordered structures. We study the assembly process by drying dispersion droplets in the presence and absence of an external magnetic field with in-situ small angle x-ray scattering (SAXS), and we compare the assemblies of magnetic and non-magnetic superballs with the same shape. The resulting assemblies geometry is investigated by altering the magnetic field strength, magnetic interparticle interactions, and particle shape. Tuning these interactions provides insights for the controllable formation of colloidal clusters as functional materials. |
Wednesday, March 16, 2022 10:00AM - 10:12AM |
M25.00011: Shape Influences Flexibility and Valence in Flexible Colloidal Molecules. Yogesh P Shelke, Daniela J Kraft, Ruben W Verweij Colloidal molecules are ideal building blocks for bottom-up self-assembly of flexible smart materials. The recent realization of microscopic flexible joints in experimental studies has enabled the study of the behaviour of colloidal flexible structures. However, the full range of motion that is provided by a spherical colloidal flexible joint may be incapable to achieve constraint flexibility. In this work, using colloidal joints and geometric principles, we design flexible colloidal molecules with controlled flexibility and valences. We achieve this by mixing complementarily functionalized spheres and cubes in a high number ratio to obtained specific valence molecules. Depending on the size of the sphere and cube we obtained molecules with different valence. These flexible colloidal molecules can be used as building blocks for assembling flexible higher-order structures. |
Wednesday, March 16, 2022 10:12AM - 10:24AM |
M25.00012: Inverse Design of Two-dimensional Self-assembly of Patchy Particles Uyen T Lieu, Natsuhiko Yoshinaga Patchy particles are the particles with anisotropic surface patterns or patches on specific positions on the surface. The interaction of such particles is not only dependent on the distance, but also on their mutual orientations. Therefore, the patchy particles are capable of organising themselves into complex structures, which are important for the generation of novel materials. Even for the case of spherical particle, there are countless ways designing patchy particle. If one tries the self-assembly of any possible particle design, it consumes exhausting time and cost due to uncountable design of the patchy particle. |
Wednesday, March 16, 2022 10:24AM - 10:36AM |
M25.00013: Tuning assembly pattern of nanoparticle droplet deposits by varying nanoscale interaction Sunita Srivastava Evaporation based self-assembly technique offers easy and affordable methods for ordering nanoparticles in crystalline structures and design complex materials. Investigating nanoscale interactions are essential for tunable assembly of colloidal nanoparticles on solid substrates. Using in-situ contact angle meter and ex-situ scanning electron microscopy, we present a direct correlation of the drying profile of nanoparticle suspension with observed deposition pattern on hydrophilic silicon substrate. The assembly pattern of DNA-coated nanoparticles via stick-slip motion gives rise to periodic concentric rings in a stripe-like micropattern for a certain nanoparticle concentration range. The results indicate that the interplay between “stick-slip” motion of the droplet contact line and coulombic and steric NP interactions control the formation of the observed structures. The change in nanoparticle shape to gold nanorods leads to mixed mode of evaporation and formation of surface pattern that exhibits multiscale assembly. Further, we will present the plasmonic application of the deposit pattern in determination of surface-enhanced Raman scattering signal of Rhodamine B analyte showing signal enhancement by factor of 7.6 * 105 and detection limit to concentration as low as 10−8M. |
Wednesday, March 16, 2022 10:36AM - 10:48AM |
M25.00014: Revealing the Emergence of Moiré Pattern and the Dynamics in Layered Superlattices at the Nanoscale Chang Liu, Lehan Yao, Tawfiqur Rakib, Harley T Johnson, Qian Chen Moiré patterns from misaligned periodic structures can bring merit to not only artistic designs but to material properties, a salient example being magic angle graphene where superconducting phase can be observed. Here, with liquid-phase transmission electron microscope (TEM), we construct superlattices with nanoparticles and observe for the first time Moiré pattern formation at the nanoscale in real time and space. To be specific, we observed layers of hexagonal lattices assembled from individual gold nanoparticles and control the nanoparticle shape to manipulate the interlayer and intralayer interactions, which leads to different Moiré patterns. We apply neural network-based machine learning to study the structures and single particle dynamics with high spatiotemporal resolution, which further helps to reveal the interplay between the Moiré pattern and the grain boundary evolution. Furthermore, calculations based on Lennard-Jones potential show distinct local position adjustment in different Moiré patterns both in plane and out of plan, resulting in normal, reduced order and disordered Moiré patterns. This work provides better understandings on nanoscale interactions which can serve as a guideline for bottom-up material design and helps to study related optical properties. |
Wednesday, March 16, 2022 10:48AM - 11:00AM |
M25.00015: Cellular Micro-Masonry: Assembling Perfect Tissue Models Cell-by-Cell Thomas E Angelini, Sarah V Ellison The different cell types that constitute living tissue are often structured into highly heterogeneous and complex spatial patterns; cell type can differ over length-scales as small as a single cell within a given tissue. For example, to maintain high rates of molecular exchange in the liver, a network of endothelial cells, called the sinusoid, permeates the periportal zone where every hepatocyte can be found within one or two cell diameters of an endothelial capillary. Another dramatic example is found in the pancreatic islet, where the five main cell types of the islet are located within a few cell diameters of one another. Small-scale structural heterogeneity is also exhibited by glandular acini in vitro. These hollow spheres are made from single epithelial monolayers surrounded by a basement membrane. While glandular acini represent an in vitro system in which the link between tissue structure and function can be studied in detail, it remains exceedingly challenging to reproduce the complex cellular patterns found more generally in vivo. Spontaneous or guided processes of multi-cellular self-assembly and advanced 3D bioprinting methods cannot precisely reproduce the detailed structural and functional heterogeneity at the single-cell scale found within in vivo tissues. In this talk we will describe a method for creating tissue models that exhibit the small-scale spatial heterogeneities found within in vivo tissue. With this method, 3D structures are built cell-by-cell, like a mason would build with stones or bricks. Thus, we call this method "Cellular Micro-Masonry." We will show that single-cell precision can be achieved with cellulular micro-masonry and that the micro-fabricated cellular structures are functional. |
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