Self-organized dynamics and the transition to turbulence of confined active nematics
Self-organized dynamics and the transition to turbulence of confined active nematics
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DOI：
10.1073/pnas.1816733116
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发表时间：
2019-03-12
影响因子：
11.1
通讯作者：
Dogic, Zvonimir
中科院分区：
文献类型：
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作者：
Opathalage, Achini;Norton, Michael M.;Dogic, Zvonimir
我们研究限制如何将基于体微管的活性向列的混沌动力学转化为规则的时空模式。对于圆盘中的弱约束，多个连续成核和湮灭的拓扑缺陷自组织成任一旋性的持续循环流。限制强度的增加导致了独特动力学的出现，其中边界处拓扑缺陷的缓慢周期性成核叠加在一对缺陷的快速行进上。缺陷对在多个旋转周期内向约束核心迁移，而相关的向列指向矢场从独特的双螺旋演变为近乎圆形对称的配置。缺陷轨道的塌陷被另一个边界局域成核事件打断，该事件建立了长期双周期动力学。将实验数据与活性向列相的理论模型进行比较表明，该理论捕获了一对+1/2缺陷的快速行进，但没有捕获缓慢的螺旋转变，也没有捕获缺陷对的周期性成核。理论也未能预测弱约束机制中循环流的出现。所开发的限制方法可推广到更复杂的几何形状，为合理设计二维自主流提供强大的微流体平台。
We study how confinement transforms the chaotic dynamics of bulk microtubule-based active nematics into regular spatiotemporal patterns. For weak confinements in disks, multiple continuously nucleating and annihilating topological defects self-organize into persistent circular flows of either handedness. Increasing confinement strength leads to the emergence of distinct dynamics, in which the slow periodic nucleation of topological defects at the boundary is superimposed onto a fast procession of a pair of defects. A defect pair migrates toward the confinement core over multiple rotation cycles, while the associated nematic director field evolves from a distinct double spiral toward a nearly circularly symmetric configuration. The collapse of the defect orbits is punctuated by another boundary-localized nucleation event, that sets up long-term doubly periodic dynamics. Comparing experimental data to a theoretical model of an active nematic reveals that theory captures the fast procession of a pair of +1/2 defects, but not the slow spiral transformation nor the periodic nucleation of defect pairs. Theory also fails to predict the emergence of circular flows in the weak confinement regime. The developed confinement methods are generalized to more complex geometries, providing a robust microfluidic platform for rationally engineering 2D autonomous flows.