Abstract.

Rod-shaped active micro/nano-particles, such as bacterial and bipolar metallic micro/nano-motors, demonstrate novel collective phenomena far from the equilibrium state compared to passive particles. We apply a simulation approach --dissipative particle dynamics (DPD)-- to explore the collectively ordered states of self-propelled rods (SPRs). The SPRs are confined in a finite circular zone and repel each other when two rods touch each other. It is found that for a long enough rods system, the global vortex patterns, dynamic pattern oscillation between hedgehog pattern and vortex pattern, and hedgehog patterns are observed successively with increasing active force F_a. For the vortex pattern, the total interaction energy between the rods U is linear with active force F_a, i.e., U ∼ F_a . While the relation U ∼ F_a² is obtained for the hedgehog structure. It is observed that a new hedgehog pattern with one defect core is created by two ejections of polar cluster in opposite directions from the original hedgehog pattern, and then merges into one through the diffusion of the two aggregates, i.e., the creation and annihilation of topological charges.

Graphical abstract

中文翻译：

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圆形约束中自推杆簇中的缺陷动力学。

摘要。

杆状活性微粒/纳米粒子，例如细菌和双极金属微粒/纳米电动机，与被动粒子相比，表现出远离平衡状态的新颖的集体现象。我们采用一种模拟方法-耗散粒子动力学（DPD）-探索自推进杆（SPR）的集体有序状态。SPR限制在有限的圆形区域中，并且当两个杆相互接触时会相互排斥。发现对于足够长的杆系统，随着主动力F _a的增加，依次观察到整体涡旋图，刺猬与旋涡图之间的动态图振荡以及刺猬图。对于涡旋模式，杆U之间的总相互作用能与作用力F _a成线性关系，即，ü〜˚F_一个。尽管关系ü〜˚F_一个²为刺猬结构获得。可以观察到，具有两个缺陷核心的新刺猬图案是通过从原始刺猬图案的相反方向两次喷出极性簇而产生的，然后通过两种聚集体的扩散合并成一个刺猬图案，即拓扑的创建和an灭收费。

图形概要