Villada-Balbuena Alejandro, Jung Gerhard, Zuccolotto-Bernez Angel B, Franosch Thomas, Egelhaaf Stefan U
Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, 6020 Innsbruck, Austria.
Soft Matter. 2022 Jun 29;18(25):4699-4714. doi: 10.1039/d2sm00412g.
Confinement modifies the properties of a fluid. The particle density is no longer uniform but depends on the distance from the walls; parallel to the walls, layers with different particle densities form. This affects the particle packing in the layers. We investigated colloidal fluids with volume fractions between 0.19 and 0.32 confined between rough walls. The particle-particle interactions were dominated by hard-sphere interactions but also contained some electrostatic interactions. The particle locations were determined using confocal microscopy and served to calculate the density profile, radial distribution function, anisotropic and generalized structure factors but also to characterize the arrangement of the wall particles leading to the roughness of the walls. The experiments are complemented by molecular dynamics simulations and fundamental-measure theory. While the particle arrangements are mainly controlled by hard-core interactions, electrostatic interactions become more important as the volume fraction decreases. Furthermore, the structure of the rough walls was varied and found to have a significant effect on the fluid structure. An appropriate representation of the rough walls in the simulations is thus crucial to successfully mimic the experiments.
受限会改变流体的性质。粒子密度不再均匀，而是取决于与壁面的距离；平行于壁面会形成具有不同粒子密度的层。这会影响层内的粒子堆积。我们研究了体积分数在0.19至0.32之间的胶体流体，它们被限制在粗糙壁面之间。粒子间相互作用以硬球相互作用为主，但也包含一些静电相互作用。使用共聚焦显微镜确定粒子位置，用于计算密度分布、径向分布函数、各向异性和广义结构因子，还用于表征导致壁面粗糙度的壁面粒子排列。实验通过分子动力学模拟和基本测量理论进行补充。虽然粒子排列主要由硬核相互作用控制，但随着体积分数降低，静电相互作用变得更加重要。此外，粗糙壁面的结构发生了变化，发现对流体结构有显著影响。因此在模拟中对粗糙壁面进行适当表示对于成功模拟实验至关重要。
