Tunable Persistent Random Walk in Swimming Droplets
Tunable Persistent Random Walk in Swimming Droplets
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DOI：
10.1103/physrevx.10.021035
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发表时间：
2020-05-14
影响因子：
12.5
通讯作者：
Brujic, Jasna
中科院分区：
文献类型：
--
作者：
Izzet, Adrien;Moerman, Pepijn G.;Brujic, Jasna
我们的特点是在一个持久的随机游走的框架内的无热游泳液滴的运动。就像活性胶体一样，它们的轨迹可以用恒定的速度V和缓慢的角扩散来建模，但是方向的随机变化不是热驱动的。相反，V由沿液滴表面的界面张力梯度沿着确定，而表面活性剂梯度的重新取向导致方向随持续时间τ的变化。我们发现，运动的起源是在前面和后面的液滴，三角洲CMC的临界胶束浓度的差异。通过salt调节该参数可将V控制在3至15直径d/s之间。表面活性剂浓度对速度几乎没有影响，但导致tau急剧下降超过4个数量级。持久长度l = V τ的相应范围延伸到合成或活体游泳者的领域之外，其中V受到燃料消耗的限制，τ分别由热波动或生物活性设定。我们的可调游泳者是研究从平衡到高水平活动的理想候选人。我们表明，他们的集体行为表现出一个明确定义的大小的活性集群的形成。
We characterize the motility of athermal swimming droplets within the framework of a persistent random walk. Just like active colloids, their trajectories can be modeled with a constant velocity V and a slow angular diffusion, but the random changes in direction are not thermally driven. Instead, V is determined by the interfacial tension gradient along the droplet surface, while reorientation of the surfactant gradient leads to changes in direction with a persistence time tau. We show that the origin of locomotion is the difference in the critical micellar concentration in the front and the back of the droplet, Delta CMC. Tuning this parameter by salt controls V from 3 to 15 diameters d/s. Surfactant concentration has little effect on speed, but leads to a dramatic decrease in tau over 4 orders of magnitude. The corresponding range of the persistence length l = V tau extends beyond the realm of synthetic or living swimmers, in which V is limited by fuel consumption and tau is set by thermal fluctuations or biological activity, respectively. Our tunable swimmers are ideal candidates for the study of the departure from equilibrium to high levels of activity. We show that their collective behavior exhibits the formation of active clusters of a well-defined size.