Topological chaos in active nematics
Topological chaos in active nematics
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DOI：
10.1038/s41567-019-0600-y
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发表时间：
2019-08
期刊：
影响因子：
19.6
通讯作者：
Amanda J. Tan;Eric Roberts;Spencer A. Smith;Ulyses Alvarado Olvera;Jorge Arteaga;Sam Fortini;K. Mitchell;L. Hirst
中科院分区：
文献类型：
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作者：
Amanda J. Tan;Eric Roberts;Spencer A. Smith;Ulyses Alvarado Olvera;Jorge Arteaga;Sam Fortini;K. Mitchell;L. Hirst
活性向列相是由棒状亚基组成的非平衡流体，其可以产生大规模的自驱动流动。我们研究了一个微管驱动蛋白为基础的活性微泡局限于两个维度，表现出混乱的流动与移动拓扑缺陷。应用混沌理论的工具，我们研究了不同长度尺度上的自驱动平流和混合。局部流体拉伸由李雅普诺夫指数量化。全局混合量化的拓扑熵，计算从缺陷编织和曲线延伸率。我们发现这些独立的措施之间的混沌非常一致，表明微管之间的延伸拉伸直接转化为宏观编织的积极缺陷。值得注意的是，增加伸展活性（通过ATP浓度）不会增加无量纲拓扑熵。这项研究代表了一个应用程序的混沌平流的新兴领域的积极向列和量化的集体运动的一个合奏的缺陷（通过拓扑熵）在液晶。
Active nematics are out-of-equilibrium fluids composed of rod-like subunits, which can generate large-scale, self-driven flows. We examine a microtubule-kinesin-based active nematic confined to two dimensions, exhibiting chaotic flows with moving topological defects. Applying tools from chaos theory, we investigate self-driven advection and mixing on different length scales. Local fluid stretching is quantified by the Lyapunov exponent. Global mixing is quantified by the topological entropy, calculated from both defect braiding and curve extension rates. We find excellent agreement between these independent measures of chaos, demonstrating that the extensile stretching between microtubules directly translates into macroscopic braiding of positive defects. Remarkably, increasing extensile activity (through ATP concentration) does not increase the dimensionless topological entropy. This study represents an application of chaotic advection to the emerging field of active nematics and quantification of the collective motion of an ensemble of defects (through topological entropy) in a liquid crystal.