Abstract
Numerical prediction of out-of-equilibrium processes in soft and bio matter containing liquids is highly desirable. However, it is quite challenging primarily because the motions of the components at different hierarchical levels (e.g., large colloids and small solvent molecules) are spatio-temporally coupled in a complicated manner via momentum conservation. Here we critically examine the predictability of numerical simulations for colloidal phase separation as a prototype example of self-organization of soft materials containing a liquid. We use coarse-grained hydrodynamic simulations to tackle this problem, and succeed in almost perfectly reproducing the structural and topological evolution experimentally observed by three-dimensional confocal microscopy without any adjustable parameters. Furthermore, comparison with non-hydrodynamic simulations shows the fundamental importance of many-body hydrodynamic interactions in colloidal phase separation. The predictive power of our computational approach may significantly contribute to not only the basic understanding of the dynamical behavior and self-organization of soft, bio and active matter but also the computer-aided design of colloidal materials.
Highlights
Nonequilibrium self-organization in colloidal suspensions includes fundamental physical phenomena, such as crystallization,[1] phase separation including gelation[2,3,4] and sedimentation.[5,6,7] These phenomena are important for materials science, and for our understanding of self-organization in active[8] and bio matter.[9]
We show that once we match the intercolloid potential and temperature in the simulations to reproduce the thermodynamic behavior of the experimental systems, such a rigorous numerical prediction of nonequilibrium structural evolution without any arbitrary parameter is possible for colloidal phase separation, which may be regarded as a typical example of nonequilibrium self-organization of colloidal matter.[2,3,31,32,33,34,35]
For ordinary binary liquid mixtures, the physics of phase separation is rather well understood on the basis of the concept of dynamic scaling,[36] and we can predict the process in a universal framework
Summary
Nonequilibrium self-organization in colloidal suspensions includes fundamental physical phenomena, such as crystallization,[1] phase separation including gelation[2,3,4] and sedimentation.[5,6,7] These phenomena are important for materials science, and for our understanding of self-organization in active[8] and bio matter.[9] To understand the physics behind these nonequilibrium phenomena, numerical simulation methods that are able to precisely describe out-of-equilibrium dynamics towards the final state is highly desirable. We show that once we match the intercolloid potential and temperature in the simulations to reproduce the thermodynamic behavior of the experimental systems, such a rigorous numerical prediction of nonequilibrium structural evolution without any arbitrary parameter is possible for colloidal phase separation, which may be regarded as a typical example of nonequilibrium self-organization of colloidal matter.[2,3,31,32,33,34,35]
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