论文标题
粘弹性流体中的迁移率和摩擦如何？
How are mobility and friction related in viscoelastic fluids?
论文作者
论文摘要
粘弹性流体中胶体探针的运动是通过摩擦或迁移率描述的，具体取决于探针是以速度或感觉到的力移动。尽管爱因斯坦的关系描述了对牛顿溶剂有效的反相关关系，但两个概念都概括为粘弹性流体中时间依赖的记忆内核。我们从理论上和实验地研究了它们的关系，通过考虑两个可观察物：释放通过流体移动的探针和平衡平均平方位移（MSD）后的后坐力。采用线性响应理论的概念，我们概括了爱因斯坦的关系，从而将后坐力和MSD介绍，这两者都提供了对移动性内核的访问。然而，随着浓度的增加，MSD和后坐力显示出不同的行为，植根于两个内核的不同行为。使用两个理论模型，即通过模式耦合理论处理的线性两浴粒子模型和硬球，我们发现了两个内核之间的Volterra关系，解释了在浓度变化下的摩擦和迁移率的不同时间尺度。
The motion of a colloidal probe in a viscoelastic fluid is described by friction or mobility, depending on whether the probe is moving with a velocity or feeling a force. While the Einstein relation describes an inverse relationship valid for Newtonian solvents, both concepts are generalized to time-dependent memory kernels in viscoelastic fluids. We theoretically and experimentally investigate their relation by considering two observables: the recoil after releasing a probe that was moved through the fluid and the equilibrium mean squared displacement (MSD). Applying concepts of linear response theory, we generalize Einstein's relation and thereby relate recoil and MSD, which both provide access to the mobility kernel. With increasing concentration, however, MSD and recoil show distinct behaviors, rooted in different behaviors of the two kernels. Using two theoretical models, a linear two-bath particle model and hard spheres treated by mode-coupling theory, we find a Volterra relation between the two kernels, explaining differing timescales in friction and mobility kernels under variation of concentration.
