Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session K16: Engineered Soft Materials: New Approaches, Mechanisms and Structures IFocus
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Sponsoring Units: DSOFT Chair: Laura Rossi, Delft University of Technology; Greg Van Anders, Queen's University Room: Room 208 |
Tuesday, March 7, 2023 3:00PM - 3:36PM |
K16.00001: Assembly Engineering and the Promise of Patchy Particles Invited Speaker: Sharon C Glotzer The last 20 years have seen significant advances in the theory, modeling, simulation, synthesis, fabrication and characterization of anisotropically interacting colloidal particle shapes self-assembling into complex structures. However, we have yet to realize the full promise of these patchy particles; namely, the ability to engineer the self-assembly of colloidal materials with precisely the structures we need for the combination of novel properties we want, and to do this both on demand and at scale. In this talk, we explore where another decade or two of research on patchy particles for assembly engineering may take us, what new developments are needed for progress, what exciting advances we are likely to see, and what the next generation of patchy particles might bring, both scientifically and technologically. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K16.00002: Hard particle self-assembly from the perspective of geometric frustration Philipp Schönhöfer, Kai Sun, Xiaoming Mao, Sharon C Glotzer It is well established that the appearance and properties of self-assembled structures are affected by the geometry of their constituents. This is especially true for hard polyhedrally shaped particles, which interact solely via excluded volume to form a plethora of entropically stabilized crystal structures. Yet, a priori prediction of these structures is non-trivial for anything but the simplest of space-filling shapes, such as cubes, especially when the thermodynamically preferred structure differs from the densest packing structure. By sufficiently curving space, however, we can eliminate the geometric constraints that prevent polyhedra from forming locally dense packings and theoretically create tessellations for all regular polyhedra. Using Monte Carlo simulations, we show that most hard polyhedra belonging to the family of Platonic solids can self-assemble into space-filling crystal structures when constrained to the surface of a hypersphere. By increasing the hypersphere radius to gradually flatten space, we introduce geometric frustration that prevents the particles from tessellating the hypersphere, and inevitably introduces defects. Lastly, we compare systems assembled in curved and flat space by applying different local environment metrics and show that all the observed assemblies of Platonic shapes in Euclidean space can be interpreted as shadows of tessellations and defects on the hypersphere. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K16.00003: Shaping the interaction behavior of mechanically linked colloids Terrence M Hopkins, stefano sacanna When engineering materials on any length scale, building block shape (and organization) determines properties and function of bulk material. One common challenge in colloidal synthesis is optimizing particle geometry design for specific particle-to-particle interactions. Herein, we investigate the relation between shape and interaction behavior by engineering the morphology of hexapod-shaped colloidal particles. The arms of hexapods can be finely tuned to be straight or winding and display unique mechanical-linkage interactions attributed to particle geometry. Upon particle packing, the mechanical interaction is characterized as reversible or irreversible, on short timescale, and display interaction behaviors visible on the macroscopic scale. |
Tuesday, March 7, 2023 4:00PM - 4:12PM Author not Attending |
K16.00004: Digital alchemy for the inverse design of patchy particles Tim Moore, Luis Y Rivera-Rivera, Sharon C Glotzer Patchy particles are colloidal building blocks whose shape and interaction anisotropy offer a strategic path to the self-assembly of complex structures with desirable properties. The many possible anisotropy dimensions of patchy particles leads to an enormous design space, making inverse design a crucial tool for the field. Of the inverse design methods available, digital alchemy (DA) is particularly attractive for patchy particles. DA is a generalized ensemble method that allows inverse design by treating particle attributes (e.g., shape and patchiness) as thermodynamic variables thereby allowing in situ updates to them. In this work, we extend the DA framework to the inverse design of triblock Janus patchy particles that self-assemble target crystal structures. We design symmetric triblock Janus particles that self-assemble the open 2D kagome and 3D pyrochlore lattices. To highlight the generality of our method, we also design asymmetric triblock Janus particles to self-assemble a snub square lattice. We find that particles designed based upon local valence considerations fail to assemble the target structure, whereas particles designed via DA succeed, highlighting the ability of the method to find nontrivial solutions to a deceptively complex design problem. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K16.00005: Simulation of nanoparticle aggregation using experimental potentials Ugochukwu O Okoli, Greg Beaucage, Kabir Rishi, Vikram K Kuppa Vogtt (2017) proposed that the degree of aggregation for nanoparticles is determined by the energy of aggregation. Experimentally determined degrees of aggregation for nanoparticles are used to verify this theory as an input to molecular dynamics simulations using LAMMPS. It is determined that, while thermodynamics governs the equilibrium degree of aggregation, the details of the nanoaggregate structure (such as the number of branches, branch length, and tortuosity of the aggregate minimum path) are determined by a combination of the thermodynamic degree of aggregation and kinetic transport properties. This approach provides a more thorough and useful view of nanoparticle aggregation compared to the Smoluchwski and other kinetic theories. The impact on nanoaggregate structure is compared for free molecular, continuum and the transition transport regimes. This approach results in an understanding of how changes in thermodynamics and transport can lead to the formation of complex hierarchical structures and macroscopic networks from nanoparticles in polymer composites and in thin layers during drying and curing. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K16.00006: Low Refractive Index Binary Colloidal Crystals from Charged Fluorinated Polymers Shihao Zang, Adam W Hauser, stefano sacanna Under the right conditions, oppositely charged colloids in water can serve as model ions and form bulk ionic colloidal crystals [1]. To study structure and crystallization dynamics of these binary systems we developed low refractive index colloidal spheres that can be index matched in water:DMSO mixtures, thus enabling in situ 3D confocal microscopy. Our particles can be made both positively and negatively charged, with uniform sizes ranging from 100 nm and 500 nm. Here, demonstrated that even when dispersed in pure water, our model system crystallizes into nearly transparent ionic colloidal crystals that can be imaged in bulk with single-particle precision. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K16.00007: Principles of self-assembly of polydisperse chains of spheres Rabeya Hussaini, Maitane Muñoz Basagoiti, Zorana Zeravcic, Jasna Brujic Nature readily uses self-assembly to organize building blocks via programmable interactions into functional entities. These processes serve as an inspiration for materials science to develop a new generation of materials. Using numerical simulations, we study a model system of DNA-coated droplets that initially assemble into a one-dimensional sequence of flavors [1], which subsequently folds into predesigned two-dimensional rigid geometries [2]. Even though the number of possible folded geometries grows exponentially with the chain length, select structures (i.e., foldamers) can still be obtained in near-perfect yields by programming the order of secondary interactions. These foldamers then serve as building blocks for ternary self-assembly of complex supracolloidal architectures. Here, we use spheres of different sizes along the chain to encode a wider range of foldamer shapes. A simple example is the folding of a tetramer chain into a rhombus with a given aspect ratio. Combining rhombi with different aspect ratios according to prescribed matching rules (given by DNA interactions) may be sufficient to make quasicrystals. The study of self-assembling aperiodic tilings could yield general principles for encoding information on nonuniform length scales. |
Tuesday, March 7, 2023 4:48PM - 5:00PM |
K16.00008: A real-space method for describing, constructing and understanding quasicrystals Domagoj Fijan, Andrew T Cadotte, Sharon C Glotzer Quasicrystals (QC) are structures with perfect order but lacking translational symmetry. Consequently, they possess some very peculiar properties, such as self-similarity, and exhibit unique internal structural rearrangements called phason flips. The state-of-the-art in understanding quasicrystals today involves the use of higher-dimensional methods, of which the most important is the project-and-cut method. This method requires facility in mapping to 5-D or higher-dimensional space, which for many researchers poses a considerable obstacle to developing an intuitive understanding of the structural complexity of quasicrystals. Although simpler, real-space approaches to understand quasicrystal structure exist (such as inflation/deflation and covering), these approaches are intrinsically unable to describe phason flips. Here we propose a new quasi-unit cell framework for describing, categorizing, constructing and understanding quasicrystals based on their self-similarity. Our framework utilizes a newly developed concept we call layering, which can explain and predict phason flips based solely on the structure of the quasi-unit cell. We show how the new framework applies to several popular 2-dimensional QC models (Penrose tilings, Ammann-Beenker tiling, etc.). |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K16.00009: Programmable physical models for understanding complex self-assemblies and designing functional materials Qian-Ze Zhu, Chrisy Xiyu Du, Ella M King, Michael P Brenner Predicting functions from material microscopic structures is fundamental to both understanding the complex behaviors of biological self-assemblies and designing functional materials with desired properties. However, the design space of current models is too vast to efficiently search for the desired functional features. Here we present an end-to-end differentiable physical model with novel features that can reproduce the functional behaviors of some biological self-assemblies, such as the dynamical growth of microtubules. Furthermore, our proposed model can directly optimize desired properties in high-dimensional parameter space (building block geometry, interaction strength, etc) using automatic differentiation. These results advance a substantial step towards understanding the complex biological behavior and inverse design of functional materials. |
Tuesday, March 7, 2023 5:12PM - 5:24PM |
K16.00010: Targeted Assembly of Colloidal Co-Crystals from Radical Voronoi Particles and the Importance of Radius Ratio Yuan Zhou, Allen LaCour, Sharon C Glotzer The additional degrees of freedom afforded to colloidal crystals by the introduction of a second particle type diversify potential applications if co-crystallization is possible. Often, however, co-crystallization is hindered in the absence of complementary attractive interactions. This is especially so in binary mixtures of hard shapes, where entropy may be maximized through demixing rather than co-crystallization. Here we report an inverse design protocol for assemblies of CsCl-, NaCl-, and cubic ZnS-type binary colloidal crystals based on the radical Voronoi tessellation [1]. Previous works show that particles whose shapes match those obtained from a simple Voronoi tessellation of the target structure [2] rarely self-assemble that structure at kinetically accessible particle volume fractions [3]. Using hard particle Monte Carlo simulation, we show how judicious choice of particle size ratio and stoichiometry of the fluid phase [4] can result in reliable self-assembly of target co-crystals. We further show that, at the optimum size ratio, the radical Voronoi shapes and those designed using the digital alchemy method [5] are similar. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K16.00011: Architecting soft materials using fluidic gates: A practical analogy to Boolean logic Alexandra V Bayles, Tazio Pleij, Matthew Murdock, Jan Vermant Soft materials often derive their functionality from the hierarchical arrangement of disparate phases. While hierarchy can develop spontaneously after certain systems are perturbed, self-assembled micron-scale structures are rather limited to particular architectures, such as the fractal aggregates found in colloidal gels and the tortuous pores found in bijels. To gain access to designer hierarchies, we engineered serpentine, millifluidic devices to assemble advecting materials into voxelated patterns. The `advective assembly' devices include three basic elements: (1) T-junctions which combine flows, (2) T-junctions which split flow, and (3) corners which rotate flow. These elements are combined in modular sequences as one would combine "AND", "OR", and "NOT" gates to form a Boolean circuit. The Boolean-inspired formalism is implemented in MATLAB Simulink and validated experimentally using viscoplastic suspensions. Within appropriate rheological constraints, the assembled architectures are determined by the contours of the device rather than the composition of the constituents. We highlight the utility of this geometrically-dictated process in two different applications: patterning hydrogel cross-linking density to program shape actuation [10.1021/acsami.2c02069], and intensifying emulsification of high-viscosity ratio systems [10.1002/aic.17192]. This work exemplifies advective assembly's broad potential to encode useful soft material structure using modular flows. |
Tuesday, March 7, 2023 5:36PM - 5:48PM |
K16.00012: Shape and interaction decoupling for colloidal pre-assembly Erin G Teich, Lucia Baldauf, Peter Schall, Greg Van Anders, Laura Rossi Creating materials with structure that is independently controllable at a range of scales requires breaking naturally occurring hierarchies. Breaking these hierarchies can be achieved via the decoupling of building block attributes from structure during assembly. Here, we demonstrate, through computer simulations and experiments, that shape and interaction decoupling occur in colloidal cuboids suspended in evaporating emulsion droplets. The resulting colloidal clusters serve as ``pre-assembled" mesoscale building blocks for larger-scale structures. We show that clusters of up to nine particles form mesoscale building blocks with geometries that are independent of the particles' degree of faceting and dipolar magnetic interactions. To highlight the potential of these superball clusters for hierarchical assembly, we demonstrate, using computer simulations, that clusters of six to nine particles can assemble into higher-order structures that differ from bulk self-assembly of individual particles. Our results suggest that pre-assembled building blocks present a viable route to hierarchical materials design. |
Tuesday, March 7, 2023 5:48PM - 6:00PM |
K16.00013: Multilayered ordered arrays self-assembled from a mixed population of nanoparticles Camila Faccini de Lima, Fanbo Sun, Vikram Jadhao Ordered self-assembled structures composed of multiple building blocks are ubiquitous in nature and have inspired many bottom-up strategies for the synthesis of nanomaterials with applications in drug delivery, biomimetic catalysts, and sensing, among others. We explore the synthesis of bio-inspired nanomaterials through the self-assembly of up to 4 different types of nanoscale virus-like particles (VLPs) derived from bacteriophage P22, which can be genetically engineered to express different surface charges. We develop a coarse-grained model to capture the assembly behavior over a broad range of VLP surface charges (-500e to -2000e) and salt concentrations (10 mM to 1000 mM). Molecular dynamics simulations based on this experimentally-validated model are used to probe the self-assembly of mixtures of multiple types of VLPs in the presence of oppositely-charged dendrimers that act as linkers. Through different combinations of two-component mixtures, we demonstrate that the self-assembly of multilayered ordered arrays, where each layer is composed of a single type of building block, can be engineered over a broad range of salt concentrations. The coarse-grained model also enables the investigation of three- and four-component mixtures, which are presented. The reversible nature of assembly and the effects of gradual vs rapid lowering of ionic strength are also discussed. |
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