Hydrodynamic rot- let dipole driven by spinning chiral liquid crystal droplets
Hydrodynamic rot- let dipole driven by spinning chiral liquid crystal droplets
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旋转手性液晶液滴驱动的流体动力旋转偶极子
DOI：
10.1103/physreve.99.022704
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
and M. Sano:
中科院分区：
文献类型：
--
作者：
T. Yamamoto;and M. Sano:
手性是游泳微生物基本的进化保守的物理方面。然而，手性在这类微游泳分子流体动力学中的作用仍有待阐明。迄今为止，流体力学理论预测，在微游泳系统满足无力矩条件下，产生扭转流的小波偶极子是手性流场的一级奇点。然而，这种手性流场从未在实验中被检测到。本文研究了手性微游泳体系统中产生的水动力场，其中胆甾液晶（CLC）液滴在表面活性剂溶液中由于旋转和马兰戈尼流之间的手性非平衡交叉耦合而表现出螺旋和自旋运动。结合旋转液滴周围的流场测量和计算流模型，我们发现CLC液滴产生了一个小波偶极子流场。值得注意的是，我们发现流场的手性成分随着距离的增加而衰减，这与由罗特雷偶极子点奇点产生的流场的理论预测是一致的。我们的发现将促进对手性在活性物质和液晶流体动力学中的作用的理解。
Chirality is an essential evolutionary-conserved physical aspect of swimming microorganisms. However, the role of chirality on the hydrodynamics of such microswimmers is still being elucidated. Hydrodynamic theories have so far predicted that, under a torque-free condition satisfied in the system of microswimmers, a rotlet dipole generating a twisting flow is the leading-order singularity of the chiral flow field. Nevertheless, such a chiral flow field has never been experimentally detected. Here we explore a hydrodynamic field generated in a system of a chiral microswimmer, where a droplet of a cholesteric liquid crystal (CLC) exhibits helical and spinning motions in surfactant solutions due to a chiral nonequilibrium cross coupling between the rotation and the Marangoni flow. Combining measurement of the flow field around the spinning CLC droplets and a computational flow modeling, we revealed that the CLC droplets generate a flow field of a rotlet dipole. Remarkably, we found that the chiral component of the flow field decays with distanceas, which is consistent with the theoretical prediction for the flow field produced by a point singularity of a rotlet dipole. Our findings will promote the understanding of roles of chirality on the hydrodynamics in active matter as well as liquid crystals.