Frontiers in Physics | Soft Matter Physics section | New and Recent Articles
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RSS Feed for Soft Matter Physics section in the Frontiers in Physics journal | New and Recent Articlesen-usFrontiers Feed Generator,version:12021-03-02T21:02:07.5781329+00:0060https://www.frontiersin.org/articles/10.3389/fphy.2020.627017
https://www.frontiersin.org/articles/10.3389/fphy.2020.627017
Thermodynamic Properties of the Parabolic-Well Fluid2021-02-26T00:00:00ZMariano López de HaroÁlvaro Rodríguez‐RivasThe thermodynamic properties of the parabolic-well fluid are considered. The intermolecular interaction potential of this model, which belongs to the class of the so-called van Hove potentials, shares with the square-well and the triangular well potentials the inclusion of a hard-core and an attractive well of relatively short range. The analytic second virial coefficient for this fluid is computed explicitly and an equation of state is derived with the aid of the second-order thermodynamic perturbation theory in the macroscopic compressibility approximation and taking the hard-sphere fluid as the reference system. For this latter, the fully analytical expression of the radial distribution function, consistent with the Carnahan-Starling equation of state as derived within the rational function approximation method, is employed. The results for the reduced pressure of the parabolic-well fluid as a function of the packing fraction and two values of the range of the parabolic-well potential at different temperatures are compared with Monte Carlo and Event‐driven molecular dynamics simulation data. Estimates of the values of the critical temperature are also provided.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.619320
https://www.frontiersin.org/articles/10.3389/fphy.2020.619320
Microscopic Model of Intermediate Phase in Flexible to Rigid Transition2021-02-05T00:00:00ZAldo Sayeg Pasos-TrejoAtahualpa S. KraemerWe introduce a lattice gas model with a modified Hamiltonian considering different energy for cycles of connected atoms. The system can be interpreted as a chalcogenide glass with pollutants forming floppy and rigid structures. We consider an energetic penalization for redundant bonds in the network. This penalization allows us to incorporate the topology constraints of rigidity in the network to study the thermodynamics of the system. We observe, depending on the parameter used for the penalization, that the system exhibits a typical first-order phase transition, or a stepped transition between the low and high density while varying the chemical potential. We also observe a hysteresis loop in the density and energy of the system. We use the area of these loops to calculate the irreversible enthalpy. There are two regimes, one where the enthalpy decreases linearly and the other with almost constant enthalpy. As the enthalpy is almost constant and very low, we interpreted this as the intermediate phase of the chalcogenide glasses.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.607480
https://www.frontiersin.org/articles/10.3389/fphy.2020.607480
The Concept of Cooperative Dynamics in Simulations of Soft Matter2020-11-27T00:00:00ZPiotr PolanowskiAndrzej SikorskiIn this review we compiled recent advances concerning the cooperative motion in crowded soft matter systems. We tried to answer the question how to perform dynamic Monte Carlo simulations of dense macromolecular systems effectively. This problem is not simple due to the fact that the movement in such systems is strictly correlated which leads to cooperative phenomena. The influence of crowding was found interesting especially for two-dimensional cases, e.g., in membranes where the presence of macromolecules, proteins and cytoskeleton often changed the mean-square displacement as a function of the lag time and anomalous diffusion appeared. Simple models are frequently used to shed a light on molecular transport in biological systems. The emphasis was given to the Dynamic Lattice Liquid model. The latter model became a basis for a parallel algorithm that takes into account coincidences of elementary molecular motion attempts resulting in local cooperative structural transformations. The emphasis is put on influence of the model of molecular transport on the diffusion. The comparison to alternative approaches like single agent model was carried out.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.579499
https://www.frontiersin.org/articles/10.3389/fphy.2020.579499
Temporal Coarse-Graining in a Slip Link Model for Polydisperse Polymer Melts2020-10-14T00:00:00ZSachin ShanbhagFor ecoSLM—an ultra coarse-grained slip link model—the ability to use a time-step that increases with chain molecular weight is an important source of efficiency in modeling the linear rheology of monodisperse chains. This feature is labeled “temporal coarse-graining” in this paper. It is compromised for blends of linear chains, where the time-step is set by the short chains, but the length of the simulation run is determined by the long chains. The problem is present for any polydisperse sample, and is particularly acute for binary blends with widely separated molecular weights. To recover temporal coarse-graining, we propose an adaptive time-step algorithm, where the time-step is determined by the shortest unrelaxed chains in the ensemble, which increases as the simulation proceeds. It involves two additional steps: recalibration, which is triggered when any component relaxes completely, and re-equilibration, in which slip links on completely relaxed components are renewed. We obtain reasonable settings for these steps, and validate the adaptive time-step algorithm by comparing it with the original, constant time-step ecoSLM for binary, ternary, and polydisperse blends. Speedups ranging from 50 to 1,500% are obtained when molecular weights of the components are widely separated, without a significant loss of accuracy. Conversely, the adaptive time-step algorithm is not recommended when molecular weights are not well-separated, since it can be slower than the constant time-step method.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.00373
https://www.frontiersin.org/articles/10.3389/fphy.2020.00373
Editorial: Topological Soft Matter2020-09-11T00:00:00ZFrancesca SerraUroš TkalecTeresa Lopez-Leonhttps://www.frontiersin.org/articles/10.3389/fphy.2020.00361
https://www.frontiersin.org/articles/10.3389/fphy.2020.00361
Chemical Design Model for Emergent Synthetic Catch Bonds2020-09-09T00:00:00ZMartijn van GalenJasper van der GuchtJoris SprakelAll primary chemical bonds inherently weaken under increasing tension. Interestingly, nature is able to combine such bonds into protein complexes that accomplish the opposite behavior: they strengthen with increasing tensional force. These complexes known as catch bonds are increasingly considered a general feature in biological systems subjected to mechanical stress. Despite their prevalence in nature however, no truly synthetic realizations of catch bonds have been accomplished so far, as it is a profound challenge to synthetically mimic the allosteric mechanisms employed by protein catch bonds. In this work we propose a computational model that shows how a synthetic catch bond could be accomplished with the help of existing supramolecular motifs and mechanophores, each of which individually act as slip bonds. This model allows us to identify the limits of catch bonding in terms of a number of experimentally measurable parameters. This knowledge could be used to suggest potential molecular candidates, thereby providing a foothold in the ongoing pursuit to realize synthetic catch bonds.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.00184
https://www.frontiersin.org/articles/10.3389/fphy.2020.00184
Microbial Active Matter: A Topological Framework2020-06-23T00:00:00ZAnupam SenguptaTopology transcends boundaries that conventionally delineate physical, biological, and engineering sciences. Our ability to mathematically describe topology, combined with recent access to precision tracking and manipulation approaches, has triggered a fresh appreciation of topological ramifications in biological systems. Microbial ecosystems, a classic example of living matter, offer a rich test bed for exploring the role of topological defects in shaping community compositions, structure, and functions spanning orders in length and time scales. Microbial activity—characteristic of such structured, out-of-equilibrium systems—triggers emergent processes that endow evolutionary and ecological benefits to microbial communities. The scene stealer of this developing cross-disciplinary field of research is the topological defects: singularities that nucleate due to spontaneous symmetry breaking within the microbial system or within the surrounding material field. The interplay of geometry, order, and topology elicit novel, if not unexpected dynamics that are at the heart of active and emergent processes in such living systems. In this short review, I have put together a summary of the key recent advances that highlight the interface of active liquid crystal physics and the physical ecology of microbes; and combined it with original data from experiments on sessile species as a case to demonstrate how this interface offers a biophysical framework that could help to decode and harness active microbial processes in true ecological settings. Topology and its functional manifestations—a crucial and well-timed topic—offer a rich opportunity for both experimentalists and theoreticians willing to take up an exciting journey across scales and disciplines.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.00212
https://www.frontiersin.org/articles/10.3389/fphy.2020.00212
A Logistic Model for Counting Crowds and Flowing Particles2020-06-17T00:00:00ZByung Mook WeonCounting how many people or particles pass through a specific space within a specific time is an interesting question in applied physics and social science. Here a logistic model is developed to estimate the total number of moving crowds or flowing particles. This model sheds light on a collective contribution of crowd or particle growth rate and transient probability within a specific space. This model may offer a basic concept to understand transport dynamics of moving crowds and flowing particles.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.00112
https://www.frontiersin.org/articles/10.3389/fphy.2020.00112
Topological Point Defects of Liquid Crystals in Quasi-Two-Dimensional Geometries2020-05-25T00:00:00ZKirsten HarthRalf StannariusWe review the interactions and dynamics of topological defects in liquid crystals (LCs) in quasi-two-dimensional (2D) geometries. Such spatial restrictions can be realized in thin freely suspended smectic C films, in thin sandwich cells filled with nematic LCs, and under specific boundary conditions in LC shells embedded in aqueous solutions. Random defect patterns can be created by thermal quenching of the samples from lower ordered into higher ordered phases. On the other hand, well-defined isolated defect configurations for the study of elementary interaction steps can be prepared by using simple mechanical techniques. Observation by polarizing microscopy is straightforward. Spatial dimensions of the experimental systems as well as time scales are convenient for observation. The continuum theory of LCs is well-developed so that, in addition to the experimental characterization, an analytical or numerical description is feasible. From interactions and dynamic features observed in these LC systems, general conclusions on defect dynamics can be drawn.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.00094
https://www.frontiersin.org/articles/10.3389/fphy.2020.00094
Geometric-Phase Waveplates for Free-Form Dark Hollow Beams2020-04-21T00:00:00ZBruno PiccirilloEster PiedipalumboEnrico SantamatoWe demonstrate the possibility of creating optical beams with phase singularities engraved into exotic intensity landscapes imitating the shapes of a large variety of diverse plane curves. To achieve this aim, we have developed a method for directly encoding the geometric properties of a selected curve into a single azimuthal phase factor without passing through indirect encryption methods involving lengthy numerical procedures. The outcome is utilized to mold the optic axis distribution of a liquid-crystal-based inhomogeneous waveplate. The latter is finally used to sculpt the wavefront of an input optical gaussian beam via the Pancharatnam-Berry phase.]]>https://www.frontiersin.org/articles/10.3389/fphy.2020.00018
https://www.frontiersin.org/articles/10.3389/fphy.2020.00018
Editorial: Non-local Modeling and Diverging Lengthscales in Structured Fluids2020-02-11T00:00:00ZAbram H. ClarkJoshua A. Dijksmanhttps://www.frontiersin.org/articles/10.3389/fphy.2019.00234
https://www.frontiersin.org/articles/10.3389/fphy.2019.00234
Interactions Between Topological Defects and Nanoparticles2020-02-06T00:00:00ZSyou-P'heng DoAmine MissaouiAlessandro CoatiAndrea RestaNicolas GoubetSébastien RoyerGeraldine GuidaEmrick BriandEmmanuel LhuillierYves GarreauDavid BabonneauMichel GoldmannDoru ConstantinBernard CrosetBruno GallasEmmanuelle LacazeLiquid Crystal (LC) topological defects have been shown to trap nanoparticles (NPs) in the defect cores. The LC topological defects may thus be used as a matrix for new kinds of NP organizations templated by the defect geometry. We here study composites of LC smectic dislocations and gold NPs. Straight NP chains parallel to the dislocations are obtained leading to highly anisotropic optical absorption of the NPs controlled by light polarization. Combining Grazing Incidence Small Angle X-ray scattering (GISAXS), Rutherford Back Scattering (RBS), Spectrophotometry and the development of a model of interacting NPs, we explore the role of the Np size regarding the dislocation core size. We use NPs of diameter D = 6 nm embedded in an array of different kinds of dislocations. For dislocation core larger than the NP size, stable long chains are obtained but made of poorly interacting NPs. For dislocation core smaller than the NP size, the disorder is induced outside the dislocation cores and the NP chains are not equilibrium structures. However we show that at least half of these small dislocations can be filled, leading to chains with strongly enhanced electromagnetic coupling between the NPs. These chains are more probably stabilized by the elastic distortions around the defect cores, the distortion being enhanced by the presence of the grain boundary where the dislocations are embedded.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00239
https://www.frontiersin.org/articles/10.3389/fphy.2019.00239
A Concise Review of Gradient Models in Mechanics and Physics2020-02-05T00:00:00ZElias C. AifantisThe various mathematical models developed over the years to interpret the behavior of materials and corresponding processes they undergo were based on observations and experiments made at that time. Classical laws for solids (Hooke) and fluids (Navier–Stokes) form the basis of current technology. The discovery of new phenomena with the aid of newly developed experimental probes have led to various modifications of these laws, especially at small scales. The emergence of nanotechnology is ultimately connected with the design of novel tools for observation and measurements, as well as with the development of new methods and approaches for quantification and understanding. This paper first reviews the author's previously developed weakly non-local or gradient models for elasticity, diffusion, and plasticity. It then proposes a similar extension for fluids and electrodynamics. Finally, it suggests a gradient modification of Newton's law of gravity, with a possible connection to the strong force of elementary particle physics.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00246
https://www.frontiersin.org/articles/10.3389/fphy.2019.00246
Non-local Effects in Shear Banding of Polymeric Flows2020-01-17T00:00:00ZSandra LerougePeter D. OlmstedMany fluids undergo shear banding, in which two states of different apparent viscosity coexist for a given shear rate (or for a given stress). In the idealized case of an infinite gap between shearing plates the selection of the conditions for shear banding has been shown to depend on the spatial structure and shape of the interface between shear bands. With the advent of microfluidic design for processing and additive manufacturing, the processing of many complex fluids often occurs in situations where this idealized limit doesn't apply, and the gap between walls, in either shearing flow or more often for pressure driven flow, is no longer “infinite” compared to the structural scales. It is increasingly clear that the effective rheology and structure of flowing fluids in these conditions requires information about the entire sample size, i.e., that the rheology is intrinsically non-local. In this review we discuss some recent attempts (both theoretical and experimental) to address non-local rheology and its implications for shear-banding flows of polymeric fluids. This manifests itself in rheology extracted from velocity profiles, as well as the dependence of shear-banding conditions on the position of the interface between shear bands, as well as the system size.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00238
https://www.frontiersin.org/articles/10.3389/fphy.2019.00238
On Generation, Motions, and Collisions of Dowsons2020-01-14T00:00:00ZPawel PieranskiMaria Helena GodinhoDowsons are ±2π point singularities of the unitary complex order parameter e^{iφ} characterizing the so-called dowser texture in a thin nematic layer with homeotropic boundary conditions. Dowsons are therefore similar to disclinations in freely-standing smectic C films or to vortices in two-dimensional superfluids or superconductors. Using especially tailored setups called dowsons' colliders, pairs of dowsons of opposite signs are generated and set into motion on counter-rotating trajectories leading to collisions. In a first approximation, the velocity of dowsons is orthogonal and proportional to the local phase gradient ∇⃗φ. The outcome of collisions, i.e., either annihilation or bypass, depends on the distance of trajectories Δφ in terms of the phase: for Δφ < π a collision of a pair of dowsons leads to their annihilation, while for Δφ > π the dowsons are passing by. This rule is valid only for quasi-static stationary wound up textures and can be easily broken by application of a Poiseuille flow in an appropriate direction.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00204
https://www.frontiersin.org/articles/10.3389/fphy.2019.00204
Fast, Scalable, and Interactive Software for Landau-de Gennes Numerical Modeling of Nematic Topological Defects2019-12-03T00:00:00ZDaniel M. SussmanDaniel A. BellerNumerical modeling of nematic liquid crystals using the tensorial Landau-de Gennes (LdG) theory provides detailed insights into the structure and energetics of the enormous variety of possible topological defect configurations that may arise when the liquid crystal is in contact with colloidal inclusions or structured boundaries. However, these methods can be computationally expensive, making it challenging to predict (meta)stable configurations involving several colloidal particles, and they are often restricted to system sizes well below the experimental scale. Here we present an open-source software package that exploits the embarrassingly parallel structure of the lattice discretization of the LdG approach. Our implementation, combining CUDA/C++ and OpenMPI, allows users to accelerate simulations using both CPU and GPU resources in either single- or multiple-core configurations. We make use of an efficient minimization algorithm, the Fast Inertial Relaxation Engine (FIRE) method, that is well-suited to large-scale parallelization, requiring little additional memory or computational cost while offering performance competitive with other commonly used methods. In multi-core operation we are able to scale simulations up to supra-micron length scales of experimental relevance, and in single-core operation the simulation package includes a user-friendly GUI environment for rapid prototyping of interfacial features and the multifarious defect states they can promote. To demonstrate this software package, we examine in detail the competition between curvilinear disclinations and point-like hedgehog defects as size scale, material properties, and geometric features are varied. We also study the effects of an interface patterned with an array of topological point-defects.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00198
https://www.frontiersin.org/articles/10.3389/fphy.2019.00198
Connecting the Drops: Observing Collective Flow Behavior in Emulsions2019-11-26T00:00:00ZJoshua A. DijksmanThoroughly mixing immiscible fluids creates droplets of one phase dispersed in a continuum of the other phase. In such emulsions, the individual droplets have rather mundane mechanical behavior. However, densely confining these suspended droplets generates a packing of particles with a spectacular diversity of mechanical behavior whose origins we are only beginning to understand. This mini review serves to survey a non-exhaustive range of experimental dense slow flow emulsion work. To embed these works in the context of the flow behavior of other structured fluids, we also discuss briefly the related non-local flow modeling attempts as one of the approaches that has been used successfully in describing emulsion flow properties and other materials.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00178
https://www.frontiersin.org/articles/10.3389/fphy.2019.00178
Chiral Topological Phases in Designed Mechanical Networks2019-11-08T00:00:00ZHenrik RonellenfitschJörn DunkelMass-spring networks (MSNs) have long been used as approximate descriptions of biological and engineered systems, from actomyosin networks to mechanical trusses. In the last decade, MSNs have re-attracted theoretical interest as models for phononic metamaterials with exotic properties such as negative Poisson's ratio, negative effective mass, or gapped vibrational spectra. A numerical advantage of MSNs is their tuneability, which allows the inverse design of materials with pre-specified bandgaps. Building on this fact, we demonstrate here that designed MSNs, when subjected to Coriolis forces, can host topologically protected chiral edge modes at predetermined frequencies, thus enabling robust unidirectional transmission of mechanical waves. Similar to other recently discovered topological materials, the topological phases of MSNs can be classified by a Chern invariant related to time-reversal symmetry breaking.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00176
https://www.frontiersin.org/articles/10.3389/fphy.2019.00176
Why the Crackling Deformations of Single Crystals, Metallic Glasses, Rock, Granular Materials, and the Earth's Crust Are So Surprisingly Similar2019-11-07T00:00:00ZKarin A. DahmenJonathan T. UhlWendelin J. WrightRecent experiments show that the deformation properties of a wide range of solid materials are surprisingly similar. When slowly pushed, they deform via intermittent slips, similar to earthquakes. The statistics of these slips agree across vastly different structures and scales. A simple analytical model explains why this is the case. The model also predicts which statistical quantities are independent of the microscopic details (i.e., they are “universal”), and which ones are not. The model provides physical intuition for the deformation mechanism and new ways to organize experimental data. It also shows how to transfer results from one scale to another. The model predictions agree with experiments. The results are expected to be relevant for failure prediction, hazard prevention, and the design of next-generation materials.]]>https://www.frontiersin.org/articles/10.3389/fphy.2019.00165
https://www.frontiersin.org/articles/10.3389/fphy.2019.00165
Dynamics of Ring Disclinations Driven by Active Nematic Shells2019-10-31T00:00:00ZJérôme HardoüinPau GuillamatFrancesc SaguésJordi Ignés-MullolWhen dispersed in thermotropic nematic liquid crystal oils, surfactant-ladden aqueous droplets often lead to the formation of a equatorial ring disclination in the nearby nematic matrix as a result of a balance between elasticity and interfacial energy. In this experimental work, the aqueous phase contains an extract of cytoskeletal proteins that self-assemble into an active quasi-two-dimensional shell featuring self-sustained periodic flows. The ensuing hydrodynamic coupling drives the surrounding liquid crystal and triggers oscillations in the disclinations. We describe the dynamic modes of the disclinations under different driving conditions, and explore their pathway to collapse under flow conditions.]]>