标题： 活性微泳者在受限流中的增强分散 显示英文标题

标题： Enhanced dispersion of active microswimmers in confined flows

摘要： 在层流剪切流存在的情况下，被动胶体粒子的扩散在平行于流动方向上得到增强。 这一经典现象被称为泰勒-阿利斯弥散。 此外，微生物，如主动微泳生物，在长时间尺度上表现出有效的扩散行为。 结合上述两种因素，一个自然的问题随之出现：在剪切流中，主动微泳生物的有效扩散是如何被改变的——这在自然环境中是普遍存在的，具有实际意义，例如关于生物膜形成的问题。 在本文中，我们研究了衣藻微藻在矩形微流控通道中的运动和弥散，该通道受到正弦波泊肃叶流的影响。 利用高分辨率光学显微镜和粒子追踪算法，我们在各种流动条件下重建了个体轨迹，并通过矩理论和小波分解对其进行统计分析。 我们发现，随着流动振幅的增加，速度波动和弥散系数都会增加，仅对流动周期性有较弱的依赖性。 重要的是，我们的结果表明，将泰勒-阿利斯定律推广到主动粒子是有效的。 显示英文摘要

摘要： In the presence of a laminar shear flow, the diffusion of passive colloidal particles is enhanced in the direction parallel to the flow. This classical phenomenon is known as Taylor-Aris dispersion. Besides, microorganisms, such as active microswimmers, exhibit an effective diffusive behavior at long times. Combining the two ingredients above, a natural question then emerges on how the effective diffusion of active microswimmers is altered in shear flows - a widespread situation in natural environments with practical implications, e.g. regarding biofilm formation. In this Letter, we investigate the motility and dispersion of Chlamydomonas reinhardtii microalgae, within a rectangular microfluidic channel subjected to a sinusoidal Poiseuille flow. Using high-resolution optical microscopy and a particle-tracking algorithm, we reconstruct individual trajectories in various flow conditions and statistically analyze them through moment theory and wavelet decomposition. We find that the velocity fluctuations and the dispersion coefficient increase as the flow amplitude is increased, with only weak dependencies on the flow periodicity. Importantly, our results demonstrate that the generalization of Taylor-Aris law to active particles is valid.