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Soft Matter

Bo Zhao, Xizhong An, Haiyang Zhao, Lingling Shen, Xudong Sun, Zongyan Zhou
The formation and growth of local order clusters in a tetrahedral granular assembly driven by 3D mechanical vibration were captured in DEM (discrete element method) dynamic simulation using a multi-sphere model. Two important kinds of clusters, dimer and wagon wheel structures, were observed based on which the growth behavior and mechanism of each local cluster with different orientations/structures were investigated. The results show that during vibration, dimer clusters are formed first and then most of them grow into linear trimers and tetramers...
February 14, 2019: Soft Matter
Yudong Zhang, Aiguo Xu, Guangcai Zhang, Yanbiao Gan, Zhihua Chen, Sauro Succi
Entropy production during the process of thermal phase-separation of multiphase flows is investigated by means of a discrete Boltzmann kinetic model. The entropy production rate is found to increase during the spinodal decomposition stage and to decrease during the domain growth stage, attaining its maximum at the crossover between the two. Such behaviour provides a natural criterion to identify and discriminate between the two regimes. Furthermore, the effects of heat conductivity, viscosity and surface tension on the entropy production rate are investigated by systematically probing the interplay between non-equilibrium energy and momentum fluxes...
February 14, 2019: Soft Matter
Jian Qin
Interfacial charge polarization is ubiquitous in systems with sharp dielectric contrast. Fully resolving the interfacial charges often relies on demanding numerical algorithms to solve the boundary value problem. The recent development of an analytical multiple-scattering formalism to solve the interfacial charge polarization problem for particles carrying monopolar, dipolar, and multipolar charges is reviewed. Every term produced in this formalism has a simple interpretation, and terms for spherical particles can be rapidly evaluated using an image-line construction...
February 14, 2019: Soft Matter
Giovanni Ciccotti, Luigi Delle Site
Molecular dynamics (MD) has become one of the most powerful tools of investigation in soft matter. Despite such success, simulations of large molecular environments are mostly run using the approximation of closed systems without the possibility of exchange of matter. Due to the molecular complexity of soft matter systems, an optimal simulation strategy would require the application of concurrent multiscale resolution approaches such that each part of a large system can be considered as an open subsystem at a high resolution embedded in a large coarser reservoir of energy and particles...
February 14, 2019: Soft Matter
Soudamini Sahoo, Sunil Pratap Singh, Snigdha Thakur
Micro-swimmers often have to encounter a medium that exhibits non-Newtonian behaviour. To understand the effect of complex environments on the propulsion dynamics of swimmers, here we have investigated a self-propelled sphere-dimer in a viscoelastic medium, using a coarse-grained hybrid mesoscopic simulation technique. We have shown that a viscoelastic fluid can result in the enhancement of swimming speed, as compared to the speed in a Newtonian fluid with the same viscosity. A non-linear response in the dimer velocity is seen for higher Péclet numbers in viscoelastic fluids...
February 13, 2019: Soft Matter
Zezhou Liu, Katharine E Jensen, Qin Xu, Robert W Style, Eric R Dufresne, Anand Jagota, Chung-Yuen Hui
Recent experiments have reported that the surface stress of soft elastic solids can increase rapidly with surface strain. For example, when a small hard sphere in adhesive contact with a soft silicone gel is slowly retracted from its rest position, it was found that the retraction force versus displacement relation cannot be explained either by the Johnson-Kendall-Roberts (JKR) theory or a recent indentation theory based on an isotropic surface stress that is independent of surface strain. In this paper, we address this problem using a finite element method to simulate the retraction process...
February 13, 2019: Soft Matter
Alexandre Turani-I-Belloto, Nathan Meunier, Paola Lopez, Jacques Leng
In the process of fabricating porous polymers, we use dispersed calcite as a sacrificial solid that generates porosity after dissolution. To do this, we trap calcite particles in a hydrogel, dissolve the particles and dry the hydrogel; here, we describe in detail the dissolution kinetics. We prepare PEGDA [poly(ethylene glycol)-diacrylate] water solutions loaded with micron-sized calcite particles (containing mostly calcium carbonate) up to about 30% volume fraction; these dispersions are photo-polymerized into hydrogels as flat and shallow monoliths with a typical thickness of ≈100 μm and a lateral extent on the order of 1 cm...
February 13, 2019: Soft Matter
Qi Li, Xiaoguang Peng, Gregory B McKenna
Diffusing wave spectroscopy (DWS)-based micro-rheology has been used in different optical geometries (backscattering and transmission) as well as different sample thicknesses in order to probe system dynamics at different length scales [D. J. Pine, D. A. Weitz, J. X. Zhu, E. Herbolzheimer. J. Phys., 1990, 51(18), 2101-2127]. Previous study from this lab [Q. Li, X. Peng, G. B. McKenna. Soft Matter, 2017, 13(7), 1396-1404] indicates the DWS-based micro-rheology observes the system non-equilibrium behaviors differently from macro-rheology...
February 13, 2019: Soft Matter
Jiaqian Li, Yuxin Song, Huanxi Zheng, Shile Feng, Wanghai Xu, Zuankai Wang
Just as the innovation of electronic diodes that allow the current to flow in one direction provides a foundation for the development of digital technologies, the engineering of surfaces or devices that allow the directional and spontaneous transport of fluids, termed liquid diodes, is highly desired in a wide spectrum of applications ranging from medical microfluidics, advanced printing, heat management and water collection to oil-water separation. Recent advances in manufacturing, visualization techniques, and biomimetics have led to exciting progress in the design of various liquid diodes...
February 13, 2019: Soft Matter
Emma Lejeune, Berkin Dortdivanlioglu, Ellen Kuhl, Christian Linder
The cerebellum is a tightly folded structure located at the back of the head. Unlike the folds of the cerebrum, the folds of the cerebellum are aligned such that the external surface appears to be covered in parallel grooves. Experiments have shown that anchoring center initiation drives cerebellar foliation. However, the mechanism guiding the location of these anchoring centers, and subsequently cerebellar morphology, remains poorly understood. In particular, there is no definitive mechanistic explanation for the preferential emergence of parallel folds instead of an irregular folding pattern like in the cerebral cortex...
February 13, 2019: Soft Matter
Fahimeh Karimi Pour Haddadan, Ali Naji, Rudolf Podgornik
We analyze the transverse intersubstrate Casimir-like force, arising as a result of thermal fluctuations of the liquid crystalline layers of a smectic-A film confined between two planar substrates in a bookshelf geometry, in which the equidistant smectic layers are placed perpendicular to the bounding surfaces. We discuss the variation of the interaction force as a function of the intersubstrate separation in the presence of surface anchoring to the substrates, showing that the force induced by confined fluctuations is attractive and depends on the penetration length as well as the layer spacing...
February 13, 2019: Soft Matter
Katja Steck, Jan H van Esch, David K Smith, Cosima Stubenrauch
Gelled lyotropic liquid crystals (LLCs) are highly tunable multi-component materials. By studying a selection of low molecular weight gelators (LMWGs), we find gelators that form self-assembled gels in LLCs without influencing their phase boundaries. We studied the system H2O/NaCl-Genapol LA070 in the presence of (a) the organogelators 12-hydroxyoctadecanoic acid (12-HOA) and 1,3:2,4-dibenzylidene-d-sorbitol (DBS) and (b) the hydrogelators N,N'-dibenzoyl-l-cystine (DBC) and a tris-amido-cyclohexane derivative (HG1)...
February 13, 2019: Soft Matter
Alejandro Cuetos, Effran Mirzad Rafael, Daniel Corbett, Alessandro Patti
By computer simulation, we model the phase behaviour of colloidal suspensions of board-like particles under the effect of an external field and assess the still disputed occurrence of the biaxial nematic (NB) liquid crystal phase. The external field promotes the rearrangement of the initial isotropic (I) or uniaxial nematic (NU) phase and the formation of the NB phase. In particular, very weak field strengths are sufficient to spark a direct I-NB or NU-NB phase transition at the self-dual shape, where prolate and oblate particle geometries fuse into one...
February 13, 2019: Soft Matter
Na Qi, Hui Zhao, Qiaozhi Wang, Yan Qin, Hao Yuan, Ying Li
Quantum dots (QDs) are of great interest due to their excellent fluorescence properties and thus, they have been widely studied. Compared with the typical organometallic synthetic routes and hydrothermal methods usually carried out under high temperatures, methods employing colloidal templates can be used for preparing QDs in mild conditions and have gained increasing attention. In this prospect, a hydrogel is an ideal colloidal template for the preparation of QDs in an aqueous medium, while the related study for in situ preparation of QDs in a gel and the consequent functionalization of QDs are in demand...
February 12, 2019: Soft Matter
C Buffone
We present a fascinating experimental investigation of the formation, stability and thermal patterns of evaporating liquid lenses deposited on an evaporating or non-evaporating liquid pool. The use of infra-red allowed measuring the key parameters of the lens and the pool surface temperature. We unveil the significant interaction of the lens with the underlying liquid in the pool. In particular, the contact line of the lens is deformed very significantly and we ascribe this to the combined buoyancy-thermocapillary convection cells on the surface of the liquid pool, generated by a self-induced evaporative cooling effect...
February 12, 2019: Soft Matter
Nicholas B Tito, Costantino Creton, Cornelis Storm, Wouter G Ellenbroek
Reversible crosslinking is a design paradigm for polymeric materials, wherein they are microscopically reinforced with chemical species that form transient crosslinks between the polymer chains. Besides the potential for self-healing, recent experimental work suggests that freely diffusing reversible crosslinks in polymer networks, such as gels, can enhance the toughness of the material without substantial change in elasticity. This presents the opportunity for making highly elastic materials that can be strained to a large extent before rupturing...
February 12, 2019: Soft Matter
Wenwen Huang, Vasily Zaburdaev
Loop geometry is a frequent encounter in synthetic and biological polymers. Here we provide an analytical theory to characterize the shapes of polymer loops subjected to an external force field. We show how to calculate the polymer density, gyration radius and its distribution. Interestingly, the distribution of the gyration radius shows a non-monotonic behavior as a function of the external force. Furthermore, we analyzed the gyration tensor of the polymer loop characterizing its overall shape. Two parameters called asphericity and the nature of asphericity derived from the gyration tensor, along with the gyration radius, can be used to quantify the shape of polymer loops in theory and experiments...
February 12, 2019: Soft Matter
Maria Valldeperas, Aleksandra P Dabkowska, Gunnar K Pálsson, Sarah Rogers, Najet Mahmoudi, Anna Carnerup, Justas Barauskas, Tommy Nylander
The advantage of using nonlamellar lipid liquid crystalline phases has been demonstrated in many applications, such as drug delivery, protein encapsulation and crystallisation. We have recently reported that a mixture of mono- and diglycerides is able to form sponge-like nanoparticles (L3-NPs) with large enough aqueous pores to encapsulate macromolecules such as proteins. Here we use small angle neutron scattering (SANS) to reveal morphology, structural and chemical composition of these polysorbate 80 (P80) stabilized sponge phase nanoparticles, not previously known...
February 11, 2019: Soft Matter
Ajay Katiyar, Tandra Nandi, Priyanka Katiyar, Purbarun Dhar, N Eswara Prasad
Herein, we report a novel nanosilica-based shear-thickening fluid, whose shear-thickening performance has been largely augmented by surface functionalizing silica employing silane chains. The functionalized shear-thickening colloids were transparent; this suggested that they have promise for application. An enhancement in viscosity was observed by over an order of magnitude by the usage of functionalized particles, which could be explained on the basis of enhanced hydroclustering and an order-to-disorder transition of the particles due to physical bonding of the silane with the base polymer...
February 11, 2019: Soft Matter
Jacopo Ciambella, Paola Nardinocchi
We introduce a continuum model for a fibre reinforced material in which the reference orientation of the fibre may evolve with time, under the influence of external stimuli. The model is formulated in the framework of large strain hyperelasticity and the kinematics of the continuum is described by both a position vector and by a remodelling tensor which, in the present context, is an orthogonal tensor representing the fibre reorientation process. By imposing suitable thermodynamical restrictions on the constitutive equation, we obtain an evolution equation of the remodelling tensor governed by the Eshelby torque, whose stationary solutions are studied in absence of any external source terms...
February 11, 2019: Soft Matter
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