When systems that can undergo phase separation between two coexisting phases in the bulk are confined in thin film geometry between parallel walls, the phase behavior can be profoundly modified. These phenomena shall be described and exemplified by computer simulations of the Asakura-Oosawa model for colloid-polymer mixtures, but applications to other soft matter systems (e.g. confined polymer blends) will also be mentioned. Typically a wall will prefer one of the phases, and hence the composition of the system in the direction perpendicular to the walls will not be homogeneous. If both walls are of the same kind, this effect leads to a distortion of the phase diagram of the system in thin film geometry, in comparison with the bulk, analogous to the phenomenon of "capillary condensation" of simple fluids in thin capillaries. In the case of "competing walls", where both walls prefer different phases of the two phases coexisting in the bulk, a state with an interface parallel to the walls gets stabilized. The transition from the disordered phase to this "soft mode phase" is rounded by the finite thickness of the film and not a sharp phase transition. However, a sharp transition can occur where this interface gets localized at (one of) the walls. The relation of this interface localization transition to wetting phenomena is discussed. Finally, an outlook to related phenomena is given, such as the effects of confinement in cylindrical pores on the phase behavior, and more complicated ordering phenomena (lamellar mesophases of block copolymers or nematic phases of liquid crystals under confinement).
We study equilibrium shapes and shape transformations of a confined semiflexible chain inside a soft lipid tubule using simulations and continuum theories. The deformed tubular shapes and chain conformations depend on the relative magnitude of their bending moduli. We characterise the collapsed macromolecular shapes by computing statistical quantities that probe the polymer properties at small length scales and report a prolate to toroidal coil transition for stiff chains. Deformed tubular shapes, calculated using elastic theories, agree with simulations. In conjunction with scattering studies…
We present a comparative computer simulation study of the phase diagrams and anomalous behavior of two-dimensional ($2D$) and quasi-two-dimensional ($q2D$) classical particles interacting with each other through isotropic core-softened potential which is used for a qualitative description of the anomalous behavior of water and some other liquids. We have shown that at the low density part of the phase diagram an increase in the width of the confining slit pore leads to a considerable decrease in the melting temperature while at high densities the melting temperature is almost unchanged.
Density-protected states in active matter under virtual confinement
Soochow University（苏州大学）；Sorbonne Université（索邦大学）；Università degli Studi dell’Insubria（因苏布里亚大学）；INFN sezione di Milano（意大利国家核物理研究所米兰分部）；Université de Montpellier（蒙彼利埃大学）；Max Planck Institute for Dynamics and Self-Organization (MPI-DS)（马克斯·普朗克动力学与自组织研究所）
Active matter broadly covers the dynamics of self-propelled particles. While the onset of collective behavior in homogenous active systems is relatively well understood, the effect of inhomogeneities such as obstacles and traps lacks overall clarity. Here, we study how interacting self-propelled particles become trapped and released from a trap. We have found that captured particles aggregate into an orbiting condensate with a crystalline structure. As more particles are added, the trapped condensate escape as a whole. Our results shed light on the effects of confinement and quenched disorder …
Geometric Limits of Mitotic Pressure Under Confinement
Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick（华威大学沃里克医学院生物医学科学系与机械化学细胞生物学中心）
Water shapes and defines the properties of biological systems. Therefore, understanding the nature of the mutual interaction between water and biological systems is of primary importance for a proper assessment of biological activity and the development of new drugs and vaccines. A handy way to characterize the interactions between biological systems and water is to analyze their impact on water density and dynamics in the proximity of the interfaces. It is well established that water bulk density and dynamical properties are recovered at distances in the order of $\sim1$~nm from the surface o…
Chirality, confinement and dimensionality govern re-entrant transitions in active matter
Indian Institute of Science Education and Research Mohali（印度科学教育研究所莫哈利分校）；Tata Institute of Fundamental Research（塔塔基础研究所）；University of Vermont（佛蒙特大学）；Institute of Physics（物理研究所）；Homi Bhabha National Institute（霍米·巴哈国家研究所）
This is an invited commentary on "Geometrically incompatible confinement of solids", B. Davidovitch, Y. Sun and G. M. Grason (PNAS, doi:10.1073/pnas.1815507116 , arxiv:1809.06919).
Macroscopic active matter under confinement: dynamical heterogeneity, bursts, and glassy behavior in a few-body system of self-propelling camphor surfers
Université Paris-Saclay（巴黎萨克雷大学）；CNRS, IJCLab（法国国家科学研究中心，原子核与亚原子物理实验室）；Dipartimento di Fisica, Sapienza Università di Roma（罗马大学物理系）；Department of Physics, California State University Fullerton（加州州立大学富勒顿分校物理系）；Department of Chemistry, California State University Fullerton（加州州立大学富勒顿分校化学系）；Université de Toulouse（图卢兹大学）；CNRS, Laboratoire de Physique Théorique（法国国家科学研究中心，理论物理实验室）；CNRS, Centre de Biologie Intégrative（法国国家科学研究中心，综合生物学中心）
