Living liquid crystals
Living liquid crystals
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DOI：
10.1073/pnas.1321926111
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
Shuang Zhou;A. Sokolov;O. Lavrentovich;I. Aranson
中科院分区：
文献类型：
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作者：
Shuang Zhou;A. Sokolov;O. Lavrentovich;I. Aranson
意义我们提出了一类活性物质，活液晶（LLC），代表运动的杆状细菌放置在水基无毒液晶。液晶的长程取向顺序和细菌的游泳活动表现出强烈的耦合，极大地改变了个体和集体的细菌动力学。例如，游动的细菌扰乱了液晶的取向顺序，甚至导致其局部熔化，使鞭毛运动在光学上可见。第二，自组织纹理出现从初始的均匀的LLC排列与细菌活性和液晶的各向异性粘弹性之间的平衡控制的特征长度。第三，局部液晶取向控制细菌的运动方向。LLC可以导致有价值的生物传感和生物医学应用。自推进生物体或合成粒子的集体运动，通常被称为“活性流体”，由于其基本的非平衡性质，在广泛的科学界引起了极大的关注。能量输入以及运动单元和介质之间的相互作用导致复杂的动力学。在这里，我们介绍了一类活性物质-活液晶（LLC）-将活的游泳细菌与溶致液晶结合在一起。LLC的物理性质可以通过细菌可用的氧气量、成分浓度或温度来控制。我们的研究揭示了大量有趣的动力学现象，引起的活动触发流和长程取向秩序的介质之间的耦合。其中包括（i）由非均匀指向矢引导的细菌运动的非线性轨迹，（ii）由细菌产生的剪切流引起的液晶的局部熔化，（iii）从非流动的均匀状态到流动的一维周期性图案的活性触发转变及其演变为拓扑缺陷的湍流阵列，和（iv）纳米厚细菌鞭毛产生的微流的双折射使能的可视化。与它们的各向同性对应物不同，LLC在非常低的细菌体积分数下显示出集体动态效应，大约为0.2%。我们的工作提出了一个非正统的设计概念，以控制和操纵软活性物质的动态行为，并打开了潜在的生物传感和生物医学应用的大门。
Significance We propose a class of active matter, the living liquid crystal (LLC), representing motile rod-shaped bacteria placed in water-based nontoxic liquid crystal. Long-range orientational order of the liquid crystal and the swimming activity of bacteria demonstrate a strong coupling that dramatically alters individual and collective bacterial dynamics. For example, swimming bacteria perturb the orientational order of the liquid crystal or even cause its local melting, making the flagella motion optically visible. Second, self-organized textures emerge from the initial uniform LLC alignment with a characteristic length controlled by a balance between bacteria activity and anisotropic viscoelasticity of liquid crystal. Third, the local liquid crystal orientation controls the direction of motion of bacteria. LLC can lead to valuable biosensoring and biomedical applications. Collective motion of self-propelled organisms or synthetic particles, often termed “active fluid,” has attracted enormous attention in the broad scientific community because of its fundamentally nonequilibrium nature. Energy input and interactions among the moving units and the medium lead to complex dynamics. Here, we introduce a class of active matter––living liquid crystals (LLCs)––that combines living swimming bacteria with a lyotropic liquid crystal. The physical properties of LLCs can be controlled by the amount of oxygen available to bacteria, by concentration of ingredients, or by temperature. Our studies reveal a wealth of intriguing dynamic phenomena, caused by the coupling between the activity-triggered flow and long-range orientational order of the medium. Among these are (i) nonlinear trajectories of bacterial motion guided by nonuniform director, (ii) local melting of the liquid crystal caused by the bacteria-produced shear flows, (iii) activity-triggered transition from a nonflowing uniform state into a flowing one-dimensional periodic pattern and its evolution into a turbulent array of topological defects, and (iv) birefringence-enabled visualization of microflow generated by the nanometers-thick bacterial flagella. Unlike their isotropic counterpart, the LLCs show collective dynamic effects at very low volume fraction of bacteria, on the order of 0.2%. Our work suggests an unorthodox design concept to control and manipulate the dynamic behavior of soft active matter and opens the door for potential biosensing and biomedical applications.