On the absence of collective motion in a bulk suspension of spontaneously rotating dielectric particles
On the absence of collective motion in a bulk suspension of spontaneously rotating dielectric particles
复制标题
关于自发旋转介电粒子的本体悬浮液中不存在集体运动
DOI：
10.1039/d3sm00298e
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发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Saintillan, David
中科院分区：
文献类型：
--
作者：
Das, Debasish;Saintillan, David
在直流电场作用下，介电粒子在二维空间中自发旋转的悬浮体靠近无滑移电极，这已被证明是一种理想的活性物质模型[Bricard et al., Nature, 2013, 503, 95-98]。在这个系统中，一种被称为Quincke旋转的电流体动力学（EHD）不稳定性被利用来创造自推进粒子，这些粒子由于EHD相互作用而彼此对齐，从而在大长度尺度上产生集体运动。人们很自然地会质疑，这些粒子的悬浮液是否也会像细菌悬浮液那样表现出集体运动和自发流动。通过分子动力学模拟，我们发现，在常规电流变流体中，在外加电场方向上形成链的介电泳力以及这些链中相邻粒子的反旋转阻止了在进行自发粒子旋转的悬浮液中的集体运动。我们的模拟发现，昆克旋转下悬架的基本微观结构单元是一对在电场方向上排列的反向旋转球体。我们执行线性稳定性分析来解释这一观察结果。
A suspension of dielectric particles rotating spontaneously when subjected to a DC electric field in two dimensions next to a no-slip electrode has proven to be an ideal model for active matter [Bricard et al., Nature, 2013, 503, 95–98]. In this system, an electrohydrodynamic (EHD) instability called Quincke rotation was exploited to create self-propelling particles which aligned with each other due to EHD interactions, giving rise to collective motion on large length scales. It is natural to question whether a suspension of such particles in three dimensions will also display collective motion and spontaneously flow like bacterial suspensions do. Using molecular dynamics type simulations, we show that dielectrophoretic forces responsible for chaining in the direction of the applied electric field in conventional electrorheological fluids and the counter-rotation of neighboring particles in these chains prevent collective motion in suspensions undergoing spontaneous particle rotations. Our simulations discover that the fundamental microstructural unit of a suspension under Quincke rotation is a pair of counter-rotating spheres aligned in the direction of the electric field. We perform a linear stability analysis that explains this observation.