Anisotropy and probe-medium interactions in the microrheology of nematic fluids
Anisotropy and probe-medium interactions in the microrheology of nematic fluids
复制标题
向列液微流变学中的各向异性和探针-介质相互作用
作者：
Andrés Córdoba;Tillmann Stieger;M. Mazza;M. Schoen;J. Pablo
提出了一种理论形式来分析和解释具有向列序的各向异性流体中的微流变实验。该方法的预测是在一个简单的粗粒度分子模型的背景下进行检查的，该模型是使用非平衡分子动力学计算进行模拟的。所提出的形式用于研究约束的影响、探针颗粒表面的锚定类型以及向列场的强度对从探针颗粒活性微流变学获得的流变响应函数的影响。正如预期的那样，更强的向列场会导致材料流变响应的各向异性增加。研究还发现，探针颗粒周围出现的缺陷结构（由锚定类型和颗粒尺寸决定）对微观流变学模拟中观察到的流变响应具有显着影响。这里考虑的模型向列流体的体积动态模量的独立估计是通过 Lees-Edwards 边界条件的小振幅振荡剪切模拟获得的。模拟结果表明，从颗粒探针微流变学中提取的动态模量与不存在颗粒时获得的动态模量不同，但随着缺陷尺寸的减小，差异也随之减小。重要的是，这里提出的向列微观流变学理论的结果与模拟结果比早期为各向同性流体设想的形式主义的结果更加一致。因此，预计本研究中提出的理论框架可以为解释液晶和受限大分子溶液或凝胶等系统中的微流变学实验提供有用的工具。
A theoretical formalism is presented to analyze and interpret microrheology experiments in anisotropic fluids with nematic order. The predictions of that approach are examined in the context of a simple coarse-grained molecular model which is simulated using nonequilibrium molecular dynamics calculations. The proposed formalism is used to study the effect of confinement, the type of anchoring at the probe-particle surface, and the strength of the nematic field on the rheological response functions obtained from probe-particle active microrheology. As expected, a stronger nematic field leads to increased anisotropy in the rheological response of the material. It is also found that the defect structures that arise around the probe particle, which are determined by the type of anchoring and the particle size, have a significant effect on the rheological response observed in microrheology simulations. Independent estimates of the bulk dynamic modulus of the model nematic fluid considered here are obtained from small-amplitude oscillatory shear simulations with Lees–Edwards boundary conditions. The results of simulations indicate that the dynamic modulus extracted from particle-probe microrheology is different from that obtained in the absence of the particle, but that the differences decrease as the size of the defect also decreases. Importantly, the results of the nematic microrheology theory proposed here are in much closer agreement with simulations than those from earlier formalisms conceived for isotropic fluids. As such, it is anticipated that the theoretical framework advanced in this study could provide a useful tool for interpretation of microrheology experiments in systems such as liquid crystals and confined macromolecular solutions or gels.
影响因子：
3.4
作者：
Kas, J;Strey, H;Janmey, PA
通讯作者：
Janmey, PA
影响因子：
4.4
作者：
Melle, Michael;Schlotthauer, Sergej;Schoen, Martin
通讯作者：
Schoen, Martin
影响因子：
3.4
作者：
Yamada, S;Wirtz, D;Kuo, SC
通讯作者：
Kuo, SC