Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T26: Physics of Hierarchical and Multiscale Soft MatterFocus Recordings Available
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Sponsoring Units: DSOFT DPOLY Chair: Jonathan Singer, Rutgers University Room: McCormick Place W-187B |
Thursday, March 17, 2022 11:30AM - 11:42AM |
T26.00001: Scalable 3D printing for topological mechanical metamaterials Guido C Baardink, Achilles Bergne, Evripides G Loukaides, Anton Souslov Mechanical metamaterials are structures designed to have exotic response, for example topological soft modes at their edge. Using a combination of finite-element simulations and experimental prototyping, we show how to 3D print these structures from a single material. We begin with a 3D ball-and-spring lattice for which we compute all modes of deformation and a topological winding number. We then translate the lattice geometry into a 3D-printed structure by replacing springs by beams composed of polymerized resin, having varying cross-section, and being connected at the lattice nodes. We confirm in finite-element simulations that in the printed material, the surface is softer than the bulk. Within the linear and small non-linear regimes, the softest side is the one predicted by the ball-and-spring model. Surprisingly, we find the opposite side to be softest at large deformations. We print the structure using stereolithography (SLA) and use a universal testing machine to confirm the presence of edges that are softer than the bulk. We find the edge softness to be dependent on deformation amplitude, constituent material, and fabrication defects. Our work contextualizes the predictions of topological mechanics for real 3D materials and their potential for cushioning applications. |
Thursday, March 17, 2022 11:42AM - 12:18PM |
T26.00002: Architected Soft Matter and the 4th Dimension Invited Speaker: Howon Lee Soft matter promises great potential for autonomous and intelligent engineering systems when precisely manufactured in specific architectures with programmed responses. Emerging pathway to create such dynamic systems involves additive manufacturing (often called 3D printing) of stimuli-responsive and programmable soft matter. This approach has been recently termed “4D printing”, with the 4th dimension being time. In this talk, additive manufacturing of various soft matter using projection micro-stereolithography (PµSL) is presented. PµSL is a micro 3D printing technique that turns light into a complex 3D structure by utilizing digital light processing (DLP) technology. Combining rapid, versatile, and scalable micro 3D printing technique with various functional soft matter, design principles and mechanics inspired by exquisite motions and morphologies in nature are physically realized. Micro-architectures that can transform, move, and even jump are demonstrated by programming of dynamic response of various responsive hydrogels. In addition, unprecedented access to micro- and nano-scale afforded by precision micro 3D printing allows for implementation of mechanics-driven design principles in micro-architectures, leading to mechanical properties far superior to those found in nature, such as ultra-low density and high stiffness. Furthermore, geometrically reconfigurable, functionally deployable, and mechanically tunable lightweight material is created through 4D printing with shape memory polymers. Also presented will be some of biomedical applications of 4D printing including a microneedle array with enhanced tissue adhesion and transformable culture tubes for rapid histological analysis of spheroids/organoids. |
Thursday, March 17, 2022 12:18PM - 12:30PM |
T26.00003: Self-Limiting Assembly of CdS Nanoparticles into Complex Corrugated Microparticles Thi Vo, Lanqin Tang, Drew Vecchio, Tao Ma, Jun Lu, Harrison Hou, Sharon C Glotzer, Nicholas A Kotov Inorganic nanoscale materials have been shown to self-assemble into microscale particles with highly corrugated geometries. However, the mechanism governing their formation remains an open question. Here, we present a joint computational and experimental study of a model system of uniformly-sized CdS-based corrugated particles (HPs) that self-assemble from polydisperse nanoparticles (NPs). We show that the topologies of corrugated particles originate from the thermodynamic preference of polydisperse NPs to attach to a nanoscale cluster where electrostatic repulsion competes with van der Waals attraction. Theoretical models and simulations of the self-assembly accounting for the competition of attractive and repulsive interactions in electrolytes accurately describe experimentally observed particle morphology, growth stages, and the spectrum of products. Our theory provides unique mechanistic insights into HP formation, allowing for a priori design of structurally complex materials with applications in catalysis, sensing, environmental remediation, and optics. |
Thursday, March 17, 2022 12:30PM - 12:42PM |
T26.00004: Mechanical Tunability of Hierarchical Porous Polymer Thin Films Robert A Green-Warren, Abigail Ren, Noah M McAllister, Luc Bontoux, Asaad Shaikh, Jae-Hwang Lee, Assimina Pelegri, Jonathan P Singer This work explores the tunability of the mechanical properties of porous polymeric thin films produced via self-limiting electrospray deposition (SLED). In this SLED regime, charged monodispersed droplets of glassy insulating materials are sprayed onto conductive substrates. As the particles are deposited, charge accumulates and repels additional droplets from being deposited, resulting in a thickness limiting effect. This leads to uniform conformal coatings that are able to coat complex 2D and 3D geometries. In this study, we examine a model glassy material, polystyrene (PS), a model plasticized material, PS blended with styrene-butadiene-styrene block copolymer (Kraton), and a model crosslinked plastic, SU-8 epoxy resin crosslinked with Versamid 125 crosslinking agent. Key SLED parameters were then selectively altered, in which changes in particle morphology, film density, and film thickness were observed using both optical microscopy and SEM. To measure the effects of these modifications on the mechanical properties, a combination of nanoindentation and nanoballistic analysis was conducted across a wide range of strain-rates, revealing the importance of both the composition and the form on the final mechanical properties. |
Thursday, March 17, 2022 12:42PM - 12:54PM |
T26.00005: In-air Polymerization and Crosslinking of Monomers during Electrospray Deposition Jonathan P Singer, Catherine J Nachtigal, Michael Grzenda Electrospray deposition is a coating technique in which a solution is passed through a charged capillary, causing the solution to disperse into child droplets through a series of Coulomb fissions until the droplets reach a grounded target. This process is advantageous due to its ability to create nanostructured self-limiting electrospray deposition (SLED) coatings with certain solutions. A large disadvantage is its use of a large amount of solvent. This is wasteful and causes sprays to take a long time to deposit a film. To alleviate this, this study focuses on spraying monomers, which can be sprayed at a much higher weight percentage than their corresponding polymers, blended with a photoactivated polymerizing agent (Omnirad 819 and Esacure 1001M blends) and crosslinker (polyethylene glycol diacrylate) under ultraviolet light to create polymers mid-spray. It was found that the spray, using methyl methacrylate as the monomer, deposited a film consisting of oligomeric polymers that could be optionally crosslinked. Translating this to additional monomers will allow for a large reduction of waste and cost in the rapid, controlled coating of complex surfaces with hierarchical composites of tunable chemistry. |
Thursday, March 17, 2022 12:54PM - 1:06PM |
T26.00006: Tuning Stoichiometry to Kinetically Enhance the Self-Assembly of Binary Colloidal Crystals Ronald A LaCour, Timothy C Moore, Sharon C Glotzer Self-assembly in binary colloidal mixtures has enabled the fabrication of colloidal superlattices with diverse structures. However, compared to single-component systems, binary mixtures are more likely subject to kinetic constraints like the formation of glasses or metastable phases, so understanding the best conditions for self-assembly is important. Here we computationally investigate the influence of stoichiometry on self-assembly, finding that adding an excess of the smaller component relative to the stoichiometry of the superlattice can enhance its propensity for self-assembly. This contradicts the common assumption that self-assembly occurs best from a mixture at the same stoichiometry as the superlattice. For two systems we investigate, self-assembly can only be accomplished in the presence of excess small particles. We focus in particular on a system of repulsively soft spheres whose interparticle interaction closely resembles experiments with nearly hard spheres, finding strong agreement between simulation and previously conducted experiments. In general, we attribute the enhancement to increased particle mobility and disfavoring of possible competing phases. Our work provides a new way to overcome kinetic limitations and achieve binary self-assembly. |
Thursday, March 17, 2022 1:06PM - 1:18PM |
T26.00007: Neutron dark-field imaging of hierarchical structures using INFER Daniel S Hussey, Caitlyn M Wolf, Youngju Kim, M. Cyrus Daugherty, Sarah M Robinson, Ryan P Murphy, David L Jacobson, Jacob M LaManna, Peter Bajcsy, Paul Kienzle, Nikolai N Klimov, Kathleen M Weigandt, Michael G Huber Neutrons are an essential tool for understanding the microstructure of soft matter. Due to the underlying theory of existing neutron scattering instruments, neutron studies have been limited to volume averages which precludes studying the evolution of hierarchical structures such as those found in many biological, geological and electrochemical systems. NIST is developing a prototype neutron dark-field imaging instrument, dubbed "INFER", based on far-field grating interferometers [1,2]. Dark-field images directly contain information of the pair-correlation function G(ξ) revealing microstructural information of the sample material [3]. The mathematics of dark-field image formation are analogous to transmission imaging, thus INFER will generate multi-scale data sets spanning length scales from the nm to the cm, in 3D with a voxel size 0.05 mm. To acquire these data sets (100+ tomograms) in a reasonable time (<1 day) requires new neutron optical components, including a novel neutron source grating. To analyze the more than 1 billion independent G(ξ) requires novel artificial intelligence based segmentation and curve fitting models. We will present simulated and measured results from model colloidal systems using a prototype INFER and discuss the outlook for future user experiments. |
Thursday, March 17, 2022 1:18PM - 1:30PM |
T26.00008: Controlling the porous structures of block copolymer based carbon fibers Guoliang Liu Block copolymer (BCP)-derived porous carbon fibers (PCFs) are emerging versatile materials that show great potential for applications ranging from energy storage to separation and to purification. To prepare PCFs from polyacrylonitrile (PAN)-based BCP, oxidative stabilization of PAN is a critical step to ensure successful carbon fiber synthesis. To investigate the effect of oxidation on the PAN-based BCP fibers, as well as the final PCFs, poly(methyl methacrylate)-block-polyacrylonitrile (PMMA-b-PAN) with varying compositions (PMMA-rich and PAN-rich) were synthesized, oxidized, and pyrolyzed. The oxidized BCP fibers exhibited improved thermal stability at ~500-800 °C compared to the as-spun BCP fibers. PCFs derived from PMMA-rich BCPs displayed mesopores within 8 h of oxidation time. The porous structures became better-defined and the pore widths and surface areas increased with oxidation time. Differently, PCFs derived from PAN-rich BCPs developed mesopores after 15 h of oxidation time and the surface area reached a plateau. The pore widths of PCFs were nearly identical when the oxidation time of BCP fibers was over 8 h. The findings highlight the importance of tuning the oxidation time to tailor the properties of BCP-derived PCFs. |
Thursday, March 17, 2022 1:30PM - 1:42PM |
T26.00009: Polybutadiene Copolymers via Atomistic and Systematic Coarse-Grained Simulations Anastassia Rissanou, Antonis Chazirakis, Patrycja Polinska, Craig Burkhart, Manolis Doxastakis, Vagelis Harmandaris The systematic coarse graining of polymeric systems is a usual route to extend the range of spatio-temporal scales and systems accessible to molecular simulations. We present a bottom-up methodology to obtain coarse-grained (CG) models for butadiene copolymers, derived from more than one species of monomers, via detailed atomistic simulations. Each monomer type is represented as a different CG particle. The effective CG interactions are obtained via a dual stage, multi-component, iterative Boltzmann inversion (IBI) optimization scheme, whereby the single component terms of the CG model are obtained from homopolymer simulations. The CG interactions between different CG type particles are obtained from simulation of a symmetric composition copolymer. The proposed optimization scheme is applied on polybutadiene (PB) copolymers consisting of cis-1,4, trans-1,4 and vinyl-1,2 isomers. The derived CG PB copolymer model is examined with respect to its transferability across molecular weights and copolymer compositions. In addition, various PB copolymers across a broad range of compositions are examined. The vinyl component is found to have a large impact on the conformational properties of PB copolymer melts due to the packing imposed by these side groups. |
Thursday, March 17, 2022 1:42PM - 1:54PM |
T26.00010: Frustrated liquid crystalline phases: Compatibility conditions for three-dimensional director fields Luiz C. B. da Silva, Efi Efrati The geometry of the space in which a director-field lies imposes restrictions on the admissible orientational order fields; for example, a field of constant bend and vanishing splay and twist cannot reside in R3. These restrictions give rise to compatibility conditions relating the quantities describing the director to the geometry of the embedding space. It was previously shown that in two dimensions, the splay and bend fields suffice to uniquely determine a director and are subject to a single compatibility condition relating their first derivatives to the Gaussian curvature of the embedding space. In this talk, we will show that in three dimensions five local fields are required to uniquely describe a director field and that these fields are related to each other and to the curvature tensor of the embedding space through six compatibility conditions. Characterizing and understanding the compatibility conditions allows us to construct previously unknown solutions, and predict the super-extensive energy growth rate as a frustrated phase grows in size without the need to solve for its ground state. |
Thursday, March 17, 2022 1:54PM - 2:06PM |
T26.00011: Cumulative Geometric Frustration and the Intrinsic Approach in Continuous Systems Efi Efrati Geometric frustration results from an incompatibility between the locally favored arrangement of the constituents in a system and the geometric properties of the space in which it resides. It naturally arises in a variety of fields ranging from macro-molecular assemblies to liquid crystals to spin models, yet in distinct systems geometric frustration may be associated with different phenomena. For example, in liquid crystals frustration may lead to spontaneous size limitation and to a unique ground state whose energy grows super-extensively, while for the Ising antiferromagnet on triangular lattice frustration leads to a highly degenerate ground state of extensive energy. |
Thursday, March 17, 2022 2:06PM - 2:18PM |
T26.00012: The effects of discretization on geometric frustration;a study of a Potts-like spin lattice system. Snir Meiri, Efi Efrati Geometric frustration arises whenever the geometry and/or the topology of the space a system is embedded in forbids the motifs locally favored by the constituents’ interactions, from being propagated. Geometric frustration arises naturally in a range of systems and displays a variety of responses from local resolution of the frustration to complex highly cooperative ground states with super extensive energy. A recent work focusing on frustration in continuous systems allowed predicting the energy exponent of frustrated systems from studying their compatibility conditions. However, systems with discrete DOF show dramatically different behavior. |
Thursday, March 17, 2022 2:18PM - 2:30PM |
T26.00013: Self-Limitation and Condensation in Geometrically Frustrated Assembly Nicholas Hackney, Chris Amey, Gregory M Grason Geometric frustration has become an important paradigm for understanding a wide range of self-assembling systems whose behavior is controlled by intra-assembly strain gradients. This strain, which scales super-extensively with domain size, prevents the system from assembling into a uniform, defect-free bulk state and drives the system, instead, towards either a dispersed, a self-limited or a defect-riddled condensed phase. Which of these states a particular system exhibits is determined by the interplay of five key parameters: frustration, inter-particle cohesion and elasticity, concentration and temperature. In this talk, we use a minimal lattice model of geometrically frustrated assembly to investigate how the ratio between frustration and cohesion mediates a transition between the self-limited and the defect-riddled condensed phases. We investigate this using both analytic and numerical methods through the use of a continuum version of our model that was developed alongside an algorithm for performing numerical Monte Carlo simulations on the original lattice model. We present the phase diagram for finite temperature geometrically frustrated assembly, delineating the boundaries between dispersed, (finite width) aggregates and bulk condensed states. |
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