Bacterial scattering in microfluidic crystal flows reveals giant active Taylor-Aris dispersion
Bacterial scattering in microfluidic crystal flows reveals giant active Taylor-Aris dispersion
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DOI：
10.1073/pnas.1819613116
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发表时间：
2019-06-04
影响因子：
11.1
通讯作者：
Guasto, Jeffrey S.
中科院分区：
文献类型：
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作者：
Dehkharghani, Amin;Waisbord, Nicolas;Guasto, Jeffrey S.
从海洋中的藻类到生活在土壤或肠道中的细菌，浮游和游泳微生物的自然栖息地的特征是高度异质的流体流动。流场拓扑结构、自推进和多孔微结构的复杂相互作用对于广泛的生物物理和生态过程（包括海洋氧气生产、有机物的生物矿化和生物膜形成）是必不可少的。虽然在过去的十年中，微生物流体动力学和表面相互作用的理解已经取得了很大的进展，在复杂的流动环境中的活性悬浮液的分散仍然提出了未解决的基本问题，排除了预测模型的微生物运输和传播在现实条件下。在这里，我们结合联合收割机实验和模拟，以确定关键的物理机制和标度律的理想化多孔介质流中的游泳细菌的分散。通过追踪微流体晶格中游动细菌的散射动力学，我们发现流体动力学梯度阻碍了细菌的横向分散，从而增强了类似于100倍以上的典型泰勒-阿里斯分散的被动布朗粒子的顺流分散。我们的分析进一步揭示，流体动力学细胞的重新取向和拉格朗日流结构诱导丝状密度模式，依赖于入射角的流动和介质的无序，在惊人的类比经典的光散射实验。
The natural habitats of planktonic and swimming microorganisms, from algae in the oceans to bacteria living in soil or intestines, are characterized by highly heterogeneous fluid flows. The complex interplay of flow-field topology, self-propulsion, and porous microstructure is essential to a wide range of biophysical and ecological processes, including marine oxygen production, remineralization of organic matter, and biofilm formation. Although much progress has been made in the understanding of microbial hydrodynamics and surface interactions over the last decade, the dispersion of active suspensions in complex flow environments still poses unsolved fundamental questions that preclude predictive models for microbial transport and spreading under realistic conditions. Here, we combine experiments and simulations to identify the key physical mechanisms and scaling laws governing the dispersal of swimming bacteria in idealized porous media flows. By tracing the scattering dynamics of swimming bacteria in microfluidic crystal lattices, we show that hydrodynamic gradients hinder transverse bacterial dispersion, thereby enhancing stream-wise dispersion similar to 100-fold beyond canonical Taylor-Aris dispersion of passive Brownian particles. Our analysis further reveals that hydrodynamic cell reorientation and Lagrangian flow structure induce filamentous density patterns that depend upon the incident angle of the flow and disorder of the medium, in striking analogy to classical light-scattering experiments.