Directional self-locomotion of active droplets enabled by nematic environment
Directional self-locomotion of active droplets enabled by nematic environment
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DOI：
10.1038/s41567-020-01055-5
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发表时间：
2020-10-12
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：
Rajabi, Mojtaba;Baza, Hend;Lavrentovich, Oleg D.
由自我推进的相互作用单元组成的活性物质，在从其看似混乱的动力学中提取有用的功方面有着重大的希望。流线型的活性物质是特别重要的，在微观尺度上，粘性力战胜惯性和运输需要一个非往复运动。在这里，我们报告说，微观活性液滴代表水性分散体的游泳细菌枯草芽孢杆菌成为单向运动时，放置在一个非活性的液晶介质。微滴内细菌的随机运动通过微滴在其表面通过各向异性分子相互作用在周围微滴中产生的极性导向结构被纠正为微滴的定向自运动。没有主动游泳者的液滴没有净位移。活性液滴的轨迹可以通过图案化微滴的分子取向来预先设计。这种效应表明，介质的空间对称性被破坏可能是控制定向微尺度传输的原因和手段。活性物质粒子自推进，但控制它们的运动方向可能是具有挑战性的。在这里，作者将能动的细菌置于微滴中，并通过利用周围液晶的不对称指向矢结构来控制它们的推进。
Active matter composed of self-propelled interacting units holds a major promise for the extraction of useful work from its seemingly chaotic dynamics. Streamlining active matter is especially important at the microscale, where the viscous forces prevail over inertia and transport requires a non-reciprocal motion. Here we report that microscopic active droplets representing aqueous dispersions of swimming bacteriaBacillus subtilisbecome unidirectionally motile when placed in an inactive nematic liquid-crystal medium. Random motion of bacteria inside the droplet is rectified into a directional self-locomotion of the droplet by the polar director structure that the droplet creates in the surrounding nematic through anisotropic molecular interactions at its surface. Droplets without active swimmers show no net displacement. The trajectory of the active droplet can be predesigned by patterning the molecular orientation of the nematic. The effect demonstrates that broken spatial symmetry of the medium can be the reason for and the means to control directional microscale transport.Active matter particles self-propel but controlling their direction of motion can be challenging. Here the authors place motile bacteria inside microdroplets and control their propulsion by exploiting the asymmetric director structure of the surrounding liquid crystal.