Institute of Physics, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland.
Soft Matter. 2023 Mar 29;19(13):2297-2310. doi: 10.1039/d2sm00957a.
Many motile microorganisms communicate with each other and their environments chemical signaling which leads to long-range interactions mediated by self-generated chemical gradients. However, consequences of the interplay between crowding and chemotactic interactions on their collective behavior remain poorly understood. In this work, we use Brownian dynamics simulations to investigate the effect of packing fraction on the formation of non-equilibrium structures in a monolayer of diffusiophoretic self-propelled colloids as a model for chemically active particles. Focusing on the case when a chemical field induces attractive positional and repulsive orientational interactions, we explore dynamical steady-states of active colloids of varying packing fractions and degrees of motility. In addition to collapsed, active gas, and dynamical clustering steady-states reported earlier for low packing fractions, a new phase-separated state emerges. The phase separation results from a competition between long-range diffusiophoretic interactions and motility and is observed at moderate activities and a wide range of packing fractions. Our analysis suggests that the fraction of particles in the largest cluster is a suitable order parameter for capturing the transition from an active gas and dynamical clustering states to a phase-separated state.
许多运动微生物通过化学信号进行彼此之间以及与环境的交流，从而导致由自产生化学梯度介导的长程相互作用。然而，拥挤和趋化相互作用之间的相互作用对它们的集体行为的影响仍然知之甚少。在这项工作中，我们使用布朗动力学模拟来研究包装分数对扩散驱动自推进胶体单层中非平衡结构形成的影响，作为化学活性粒子的模型。我们关注的是当化学场诱导吸引位置和排斥方向相互作用时，我们探索了不同包装分数和运动程度的活性胶体的动态稳定状态。除了先前在低包装分数下报道的坍塌、活性气体和动态聚类稳态之外，还出现了新的相分离状态。相分离是长程扩散相互作用和运动之间竞争的结果，在中等活性和广泛的包装分数范围内观察到。我们的分析表明，最大簇中的粒子分数是捕捉从活性气体和动态聚类状态到相分离状态的转变的合适序参量。
