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Curvature-induced defect unbinding and dynamics in active nematic toroids
Nature Physics ( IF 19.6 ) Pub Date : 2017-10-23 , DOI: 10.1038/nphys4276
Perry W. Ellis , Daniel J. G. Pearce , Ya-Wen Chang , Guillermo Goldsztein , Luca Giomi , Alberto Fernandez-Nieves

Nematic order on curved surfaces is often disrupted by the presence of topological defects, which are singular regions in which the orientational order is undefined. In the presence of force-generating active materials, these defects are able to migrate through space like swimming microorganisms. We use toroidal surfaces to show that despite their highly chaotic and non-equilibrium dynamics, pairs of defects unbind and segregate in regions of opposite Gaussian curvature. Using numerical simulations, we find that the degree of defect unbinding can be controlled by tuning the system activity, and even suppressed in strongly active systems. Furthermore, by using the defects as active microrheological tracers and quantitatively comparing our experimental and theoretical results, we are able to determine material properties of the active nematic. Our results illustrate how topology and geometry can be used to control the behaviour of active materials, and introduce a new avenue for the quantitative mechanical characterization of active fluids.



中文翻译:

主动向列环的曲率引起的缺陷解脱和动力学

曲面缺陷上的向列顺序通常会由于拓扑缺陷的存在而中断,这些缺陷是方向顺序不确定的奇异区域。在产生力的活性物质的存在下,这些缺陷能够像游泳微生物一样在太空中迁移。我们使用环形曲面来显示,尽管它们具有高度混沌和非平衡的动力学特性,但成对的缺陷在高斯曲率相反的区域解开并隔离。使用数值模拟,我们发现可以通过调整系统活动来控制缺陷解除绑定的程度,甚至在强活动系统中也可以将其抑制。此外,通过使用缺陷作为活性微流变示踪剂,并定量比较我们的实验结果和理论结果,我们能够确定活性向列型的材料性质。

更新日期:2017-10-30
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