Hypothesis

Colloidal particles in a nematic liquid crystal (NLC) exhibit very different behaviour to that observed in an isotropic medium. Such differences arise principally due to the nematic-induced elastic stresses exerted due to the interaction of NLC molecules with interfaces, which compete with traditional fluid viscous stresses on the particle.

Theory

A systematic mathematical analysis of particles in an NLC microfluidic channel is performed using the continuum Beris–Edwards framework coupled to the Navier–Stokes equations. We impose strong homeotropic anchoring on the channel walls and weak homeotropic anchoring on the particle surfaces.

Findings

The viscous and NLC forces act on an individual particle in opposing directions, resulting in a critical location in the channel where the particle experiences zero net force in the direction perpendicular to the flow. For multi-particle aggregation we show that the final arrangement is independent of the initial configuration, but the path towards achieving equilibrium is very different. These results uncover new mechanisms for particle separation and routes towards self-assembly.

中文翻译：

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胶体自组装和运输现象的神经流体动力学

假设

向列液晶（NLC）中的胶体粒子表现出与各向同性介质中观察到的行为截然不同的行为。这种差异主要是由于NLC分子与界面的相互作用所引起的向列相诱导的弹性应力而产生的，该弹性应力与颗粒上的传统流体粘性应力竞争。

理论

使用连续的Beris-Edwards框架与Navier-Stokes方程耦合，对NLC微流体通道中的粒子进行了系统的数学分析。我们在通道壁上施加强的垂直锚固，而在粒子表面施加弱的垂直锚固。

发现

粘性力和NLC力沿相反的方向作用于单个颗粒，从而在通道中的一个关键位置处使颗粒在垂直于流的方向上受到零净力。对于多粒子聚集，我们表明最终的布置与初始构型无关，但是达到平衡的途径却大不相同。这些结果揭示了颗粒分离的新机制以及实现自组装的途径。