Polar jets of swimming bacteria condensed by a patterned liquid crystal
Polar jets of swimming bacteria condensed by a patterned liquid crystal
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DOI：
10.1038/s41567-020-0793-0
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发表时间：
2020-03-02
期刊：
影响因子：
19.6
通讯作者：
Lavrentovich, Oleg D.
中科院分区：
文献类型：
--
作者：
Turiv, Taras;Koizumi, Runa;Lavrentovich, Oleg D.
活性物质表现出显著的集体行为，其中由活性粒子不断产生的流动与这些粒子的取向顺序交织在一起。由于活动和顺序难以独立控制，因此对两者之间的关系仍知之甚少。在这里，我们通过探索在分子取向上预先设计的周期性伸展和弯曲的液晶环境中游动细菌的动力学，展示了这种相互作用的重要方面。细菌被从弯曲区域排出，并凝结成沿弯曲区域单向传播和运输货物的极性射流。细菌射流保持稳定，即使局部浓度超过弯曲不稳定的阈值在非图案系统。通过平流扩散模型和将系统视为两相主动向列的数值模拟，解释了集体极性推进以及弯曲和张开的不同作用。预先设计的液晶介质能够将游动细菌的混乱运动流线化，使其成为极地射流，从而可以沿着预先设计的轨迹携带货物，这为微型运输和软微型机器人的潜在应用打开了大门。动态和活动物质的空间秩序之间的关系产生了一个尚未完全理解的丰富现象学。一项对在有图案的液晶环境中游泳的细菌的研究就是一个很好的例子，它提供了一种将游泳细菌的混乱运动流线化成极地射流的方法。
Active matter exhibits remarkable collective behaviour in which flows, continuously generated by active particles, are intertwined with the orientational order of these particles. The relationship remains poorly understood as the activity and order are difficult to control independently. Here we demonstrate important facets of this interplay by exploring the dynamics of swimming bacteria in a liquid crystalline environment with predesigned periodic splay and bend in molecular orientation. The bacteria are expelled from the bend regions and condense into polar jets that propagate and transport cargo unidirectionally along the splay regions. The bacterial jets remain stable even when the local concentration exceeds the threshold of bending instability in a non-patterned system. Collective polar propulsion and the different roles of bend and splay are explained by an advection-diffusion model and by numerical simulations that treat the system as a two-phase active nematic. The ability of prepatterned liquid crystalline medium to streamline the chaotic movements of swimming bacteria into polar jets that can carry cargo along a predesigned trajectory opens the door for potential applications in microscale delivery and soft microrobotics.The relationship between the dynamics and spatial order of active matter gives rise to a rich phenomenology that is not fully understood. A study of bacteria swimming in a patterned liquid crystalline environment is a case in point, and provides a way to streamline the chaotic movements of swimming bacteria into polar jets.