Active Brownian motion of emulsion droplets: Coarsening dynamics at the interface and rotational diffusion
Active Brownian motion of emulsion droplets: Coarsening dynamics at the interface and rotational diffusion
复制标题
DOI：
10.1140/epje/i2016-16080-y
复制
发表时间：
2016-08
期刊：
影响因子：
--
通讯作者：
M. Schmitt;Holger Stark
中科院分区：
文献类型：
--
作者：
M. Schmitt;Holger Stark
[摘要]张建军，张建军，张建军，等。溴水微滴在含表面活性剂的油相中游动的研究[j] .环境科学学报，2003,13(4):526 - 526（2011）。溴与表面活性剂在液滴界面处反应生成表面活性剂混合物。由于溶液毛细管马兰戈尼流的作用，液滴可以自发相分离。我们用扩散-平流-反应方程对系统进行了建模，该方程包含了热噪声，并将其与流体流动耦合。超越以往的工作，我们说明了表面活性剂混合物在轴对称游动状态下走向相分离的粗化动力学。粗化过程分两个步骤进行：最初是区域尺寸的缓慢增长，然后是接近弹道的状态。在更大的时间尺度上，局部表面活性剂组成的热波动引发游动方向的随机变化，液滴进行持续的随机游动，如实验所观察到的那样。数值解表明，旋转相关时间尺度与噪声强度的平方成反比。我们通过混合序参量波动的微扰理论证实了这种标度，从而确定了活性乳状液滴为活性布朗粒子。图形抽象
AbstractA micron-sized droplet of bromine water immersed in a surfactant-laden oil phase can swim (S. Thutupalli, R. Seemann, S. Herminghaus, New J. Phys.13073021 (2011). The bromine reacts with the surfactant at the droplet interface and generates a surfactant mixture. It can spontaneously phase-separate due to solutocapillary Marangoni flow, which propels the droplet. We model the system by a diffusion-advection-reaction equation for the mixture order parameter at the interface including thermal noise and couple it to fluid flow. Going beyond previous work, we illustrate the coarsening dynamics of the surfactant mixture towards phase separation in the axisymmetric swimming state. Coarsening proceeds in two steps: an initially slow growth of domain size followed by a nearly ballistic regime. On larger time scales thermal fluctuations in the local surfactant composition initiates random changes in the swimming direction and the droplet performs a persistent random walk, as observed in experiments. Numerical solutions show that the rotational correlation time scales with the square of the inverse noise strength. We confirm this scaling by a perturbation theory for the fluctuations in the mixture order parameter and thereby identify the active emulsion droplet as an active Brownian particle.Graphical abstract