Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
Phys Rev E. 2019 Jan;99(1-1):012610. doi: 10.1103/PhysRevE.99.012610.
Experiments have shown that self-propelled particles can slide along the surface of a circular obstacle without becoming trapped over long times. Using simulations and theory, we study the impact of boundary conditions on the diffusive transport of active particles in an obstacle lattice. We find that particle dynamics with sliding boundary conditions result in large diffusivities even at high obstacle density, unlike classical specular reflection. These dynamics are very well described by a model based on run-and-tumble particles with microscopically derived reorientation functions arising from obstacle-induced tumbles. This model, however, fails to describe fine structure in the diffusivity at high obstacle density predicted by simulations for pusherlike collisions. Using a simple deterministic model, we show that this structure results from particles being guided by the lattice. Our results thus show how nonclassical surface scattering introduces a dependence on the lattice geometry at high densities. We discuss implications for the study of bacteria in complex environments.
实验表明，自推进粒子可以在长时无阻碍地沿圆形障碍物表面滑动。我们使用模拟和理论研究了在障碍物晶格中，边界条件对主动粒子扩散输运的影响。我们发现，与经典的镜面反射不同，具有滑动边界条件的粒子动力学导致即使在高障碍物密度下也具有大的扩散率。这些动力学可以通过基于运行和翻转粒子的模型很好地描述，该模型基于障碍物诱导的翻转产生微观推导的重新定向函数。然而，该模型无法描述模拟预测的推斥碰撞中高障碍物密度下扩散率的精细结构。使用简单的确定性模型，我们表明这种结构是由粒子被晶格引导引起的。因此，我们的结果表明，非经典的表面散射如何在高密度下引入对晶格几何形状的依赖性。我们讨论了这对在复杂环境中研究细菌的影响。
