远离平衡态的剪切胶体液体：解缠结弛豫、平流和剪切诱导扩散
Far-from-equilibrium Sheared Colloidal Liquids: Disentangling Relaxation, Advection, and Shear-induced Diffusion
摘要：
使用高速共聚焦显微镜，我们测量的大振幅振荡剪切下的胶体悬浮液中的颗粒位置。使用粒子的位置，我们量化的原位各向异性的对-关联函数-布朗应力的措施。从这些数据中，我们发现两种不同类型的响应系统从平衡跨越到远离平衡态。第一种是由剪切诱导的平流引起的非线性振幅饱和，而第二种是由于悬浮液松弛和剪切速率之间的竞争引起的线性频率饱和。尽管其不同的基本机制，我们表明，所有的数据可以缩放到一个主曲线，跨越平衡和远离平衡制度，连接小振幅振荡连续剪切。这一观察结果说明了Cox-Merz规则的胶体类似物及其微观基础。布朗动力学模拟表明，粒子间的相互作用足以产生实验观察到的饱和度。
英文摘要：
Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large amplitude oscillatory shear. Using the particle positions we quantify the in situ anisotropy of the pair-correlation function -- a measure of the Brownian stress. From these data, we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian Dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations.
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