Crowding-Enhanced Diffusion: An Exact Theory for Highly Entangled Self-Propelled Stiff Filaments,Physical Review Letters

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Crowding-Enhanced Diffusion: An Exact Theory for Highly Entangled Self-Propelled Stiff Filaments
Physical Review Letters ( IF 8.1 ) Pub Date : 2020-09-23 , DOI: 10.1103/physrevlett.125.138002
Suvendu Mandal ₁ , Christina Kurzthaler _{2,

3} , Thomas Franosch ₃ , Hartmut Löwen ₁

Affiliation

We study a strongly interacting crowded system of self-propelled stiff filaments by event-driven Brownian dynamics simulations and an analytical theory to elucidate the intricate interplay of crowding and self-propulsion. We find a remarkable increase of the effective diffusivity upon increasing the filament number density by more than one order of magnitude. This counterintuitive “crowded is faster” behavior can be rationalized by extending the concept of a confining tube pioneered by Doi and Edwards for highly entangled, crowded, passive to active systems. We predict a scaling theory for the effective diffusivity as a function of the Péclet number and the filament number density. Subsequently, we show that an exact expression derived for a single self-propelled filament with motility parameters as input can predict the nontrivial spatiotemporal dynamics over the entire range of length and timescales. In particular, our theory captures short-time diffusion, directed swimming motion at intermediate times, and the transition to complete orientational relaxation at long times.

中文翻译：

拥挤增强扩散：高度缠结自驱动硬丝的精确理论

我们通过事件驱动的布朗动力学模拟和分析理论研究了自驱动刚性丝的强相互作用拥挤系统，以阐明拥挤和自推进的复杂相互作用。我们发现，当丝数密度增加一个数量级以上时，有效扩散率显着增加。这种违反直觉的“拥挤速度更快”行为可以通过将 Doi 和 Edwards 首创的限制管概念扩展到主动系统来合理化，该限制管用于高度纠缠、拥挤、被动的系统。我们预测了有效扩散率作为佩克莱数和细丝数密度函数的比例理论。随后，我们表明，以运动参数作为输入，为单个自驱动细丝导出的精确表达式可以预测整个长度和时间尺度范围内的非平凡时空动力学。特别是，我们的理论捕获了短时扩散、中间时间的定向游泳运动以及长时间向完全定向松弛的过渡。

更新日期：2020-09-23

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