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arXiv 2011.03175cond-mat.soft
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通过转向更高密度区域的活性相分离

Active phase separation by turning toward regions of higher density

Jie Zhang, Ricard Alert, Jing Yan, Ned S. Wingreen, Steve Granick

摘要:

对从分子组装到动物群体的活性物质的研究揭示了两大类行为:排列的趋势产生取向有序和集体运动,而粒子排斥导致自捕获和运动诱导的相分离。在这里,我们报告的第三类行为:取向的相互作用,产生积极的相分离。结合理论和实验的自推进Janus胶体,我们表明,较强的排斥力的后方比这些粒子的前面产生非互易性的扭矩,重定向粒子运动向高密度区域。因此,颗粒会向拥挤的区域自我推进,从而导致相分离。团簇保持流动性,并表现出快速的颗粒周转,与通常由自捕获产生的堵塞的团簇相反,并且界面足够宽,它们跨越整个团簇。总的来说,我们的工作确定了一个基于扭矩的机制,在活性流体中的相分离,我们的理论预测,这些取向的相互作用产生共存的阶段,缺乏内部的取向秩序。

英文摘要:

Studies of active matter, from molecular assemblies to animal groups, have revealed two broad classes of behavior: a tendency to align yields orientational order and collective motion, whereas particle repulsion leads to self-trapping and motility-induced phase separation. Here, we report a third class of behavior: orientational interactions that produce active phase separation. Combining theory and experiments on self-propelled Janus colloids, we show that stronger repulsion on the rear than on the front of these particles produces non-reciprocal torques that reorient particle motion toward high-density regions. Particles thus self-propel toward crowded areas, which leads to phase separation. Clusters remain fluid and exhibit fast particle turnover, in contrast to the jammed clusters that typically arise from self-trapping, and interfaces are sufficiently wide that they span entire clusters. Overall, our work identifies a torque-based mechanism for phase separation in active fluids, and our theory predicts that these orientational interactions yield coexisting phases that lack internal orientational order.

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