Moran Shannon E, Bruss Isaac R, Schönhöfer Philipp W A, Glotzer Sharon C
Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA.
Soft Matter. 2022 Feb 2;18(5):1044-1053. doi: 10.1039/d0sm00913j.
Studies of active particle systems have demonstrated that particle anisotropy can impact the collective behavior of a system, motivating a systematic study. Here, we report a systematic computational investigation of the role of anisotropy in shape and active force director on the collective behavior of a two-dimensional active colloidal system. We find that shape and force anisotropy can combine to produce critical densities both lower and higher than those of disks. We demonstrate that changing particle anisotropy tunes what we define as a "collision efficiency" of inter-particle collisions in leading to motility-induced phase separation (MIPS) of the system. We use this efficiency to determine the relative critical density across systems. Additionally, we observe that local structure in phase-separated clusters is the same as the particle's equilibrium densest packing, suggesting a general connection between equilibrium behavior and non-equilibrium cluster structure of self-propelled anisotropic particles. In engineering applications for active colloidal systems, shape-controlled steric interactions such as those described here may offer a simple route for tailoring emergent behaviors.
对活性粒子系统的研究表明，粒子各向异性会影响系统的集体行为，从而推动了一项系统性研究。在此，我们报告了一项系统性计算研究，该研究探讨了形状和主动力指向矢方面的各向异性对二维活性胶体系统集体行为的作用。我们发现，形状和力的各向异性可以共同作用，产生低于和高于圆盘临界密度的临界密度。我们证明，改变粒子各向异性会调整我们所定义的粒子间碰撞的“碰撞效率”，从而导致系统的运动诱导相分离（MIPS）。我们利用这种效率来确定不同系统间的相对临界密度。此外，我们观察到相分离聚集体中的局部结构与粒子的平衡最密堆积相同，这表明自推进各向异性粒子的平衡行为与非平衡聚集体结构之间存在普遍联系。在活性胶体系统的工程应用中，此处所述的形状控制的空间相互作用可能为定制涌现行为提供一条简单途径。
