The problem of measuring nontrivial static correlations in deeply supercooled liquids made recently some progress thanks to the introduction of amorphous boundary conditions, in which a set of free particles is subject to the effect of a different set of particles frozen into their (low temperature) equilibrium positions. In this way, one can study the crossover from nonergodic to ergodic phase, as the size of the free region grows and the effect of the confinement fades. Such crossover defines the so-called point-to-set correlation length, which has been measured in a spherical geometry, or cavity. Here, we make further progress in the study of correlations under amorphous boundary conditions by analyzing the equilibrium properties of a glass-forming liquid, confined in a planar ("sandwich") geometry. The mobile particles are subject to amorphous boundary conditions with the particles in the surrounding walls frozen into their low temperature equilibrium configurations. Compared to the cavity, the sandwich geometry has three main advantages: (i) the width of the sandwich is decoupled from its longitudinal size, making the thermodynamic limit possible; (ii) for very large width, the behaviour off a single wall can be studied; (iii) we can use "anti-parallel" boundary conditions to force a domain wall and measure its excess energy. Our results confirm that amorphous boundary conditions are indeed a very useful new tool in the study of static properties of glass-forming liquids, but also raise some warning about the fact that not all correlation functions that can be calculated in this framework give the same qualitative results.
Soft microcapsules moving in a cylindrical capillary deform from quasi-spherical shapes to elongated shapes with an inversion of curvature at the rear. We investigated the perturbation of the flow by particle tracking velocimetry around deformed microcapsules in confined flow. These experiments are completed by numerical simulations. Microcapsules are made of a thin membrane of polymerized human albumin and their shear elastic moduli are previously characterized in a cross flow chamber. Firstly, the velocity of the microcapsule can be calculated by theoretical predictions for rigid spheres, even for large deformations as 'parachute-like' shapes, if a relevant definition of the ratio of confinement is chosen. Secondly, at the rear and the front of the microcapsule, the existence of multiple recirculation regions is governed by the local curvature of the membrane. The amplitudes of these perturbations increase with the microcapsule deformation, whereas their axial extents are comparable to the radius of the capillary whatever the confinement and the capillary number. We conclude that whereas the motion of microcapsules in confined flow has quantitative similitudes with rigid spheres in term of velocity and axial extent of the perturbation, their presence induces variations in the flow field that are related to the local deformation of the membrane as in droplets.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.