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arXiv 1704.08400cond-mat.softcond-mat.stat-mechphysics.flu-dyn
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基于图像应力测量的胶体悬浮液Green-Kubo关系的实验实现

Experimental Realization of the Green-Kubo Relation in Colloidal Suspensions Enabled by Image-based Stress Measurements

Neil Y. C. Lin, Matthew Bierbaum, Itai Cohen

摘要:

通过结合共聚焦显微镜和局部结构各向异性应力评估(SALSA),我们直接测量三维静态胶体液体中的应力。我们的非侵入性和非微扰的方法使我们能够测量力$\lesssim$ 50 fN与一个小的和可调的探测体积,使我们能够解决由粒子热运动产生的应力波动。我们使用Green-Kubo关系将这些测得的应力波动与不同体积分数下的体布朗粘度联系起来,并与模拟和常规流变测量进行比较。我们证明,绿色久保分析给出了很好的协议与这些先前的结果。这一协议提供了一个强有力的证明,几乎硬球悬浮液中的格林-久保关系的适用性,并打开了大门,调查当地的流动性质在许多知之甚少的远离平衡系统,包括悬浮液是玻璃状的,强烈剪切,或高度限制。

英文摘要:

By combining confocal microscopy and Stress Assessment from Local Structural Anisotropy (SALSA), we directly measure stresses in 3D quiescent colloidal liquids. Our non-invasive and non-perturbative method allows us to measure forces $\lesssim$ 50 fN with a small and tunable probing volume, enabling us to resolve the stress fluctuations arising from particle thermal motions. We use the Green-Kubo relation to relate these measured stress fluctuations to the bulk Brownian viscosity at different volume fractions and comparing against simulations and conventional rheometry measurements. We demonstrate that the Green-Kubo analysis gives excellent agreement with these prior results. This agreement provides a strong demonstration of the applicability of the Green-Kubo relation in nearly hard-sphere suspensions and opens the door to investigations of local flow properties in many poorly understood far-from-equilibrium systems, including suspensions that are glassy, strongly-sheared, or highly-confined.

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