Self-Propelled Colloidal Particle Near a Planar Wall: A Brownian Dynamics Study
Self-Propelled Colloidal Particle Near a Planar Wall: A Brownian Dynamics Study
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DOI：
10.1103/physrevfluids.3.014104
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发表时间：
2016-11
期刊：
影响因子：
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通讯作者：
A. Mozaffari;Nima Sharifi-Mood;J. Koplik;C. Maldarelli
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文献类型：
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作者：
A. Mozaffari;Nima Sharifi-Mood;J. Koplik;C. Maldarelli
小型化的自推进运动器使用化学机械转换机制将环境中的燃料转换为自主运动。最近的实验和理论研究表明，这些自主引擎可以被动地遵循它们遇到的固体边界的轮廓。然而，边界制导不一定是稳定的：机械干扰会导致发动机流体动力学地离开被动制导路径。此外，由于微型电机的尺寸缩小（通常为100 nm-10 $\mu$m），布朗热波动力必然是重要的，这些随机力可以随机被动转向轨迹。在这里，我们研究理论上的稳定性边界引导运动的微电机沿着无限平面壁机械干扰和布朗力。我们的目的是了解在什么条件下，这种被动引导的运动是稳定的。我们选择了一个运动设计，其中球形胶体部分涂覆有催化帽，与溶质反应产生的产品。产品从颗粒表面被排斥，导致颗粒以惰性面在前面移动（通过自扩散电泳的自主运动）。当被推向一个平面的墙壁，确定性的流体动力学研究表明，这些运动可以表现出，足够大的帽尺寸，稳定的轨迹中的颗粒要么单方向地沿沿着表面在一个恒定的距离从墙壁，或成为静止。我们首先通过展开这些状态的运动方程来研究这些状态的线性流体动力学稳定性，并发现线性扰动随时间呈指数衰减。然后，我们研究的热波动的影响，制定一个朗之万方程的粒子运动，其中包括布朗随机力…
Miniaturized, self-propelled locomotors use chemo-mechanical transduction mechanisms to convert fuel in the environment to autonomous motion. Recent experimental and theoretical studies demonstrate that these autonomous engines can passively follow the contours of solid boundaries they encounter. Boundary guidance, however, is not necessarily stable: Mechanical disturbances can cause the motor to hydrodynamically depart from the passively guided pathway. Furthermore, given the scaled-down size of micromotors (typically 100 nm -10 $\mu$m), Brownian thermal fluctuation forces are necessarily important and these stochastic forces can randomize passively-steered trajectories. Here we examine theoretically the stability of boundary guided motion of micromotors along infinite planar walls to mechanical disturbances and to Brownian forces. Our aim is to understand under what conditions this passively guided motion is stable. We choose a locomotor design in which spherical colloids are partially coated with a catalytic cap that reacts with solute to produce a product. The product is repelled from the particle surface, causing the particle to move with the inert face at the front (autonomous motion via self-diffusiophoresis). When propelled towards a planar wall, deterministic hydrodynamic studies demonstrate that these locomotors can exhibit, for large enough cap sizes, steady trajectories in which the particle either skims unidirectionally along the surface at a constant distance from the wall, or becomes stationary. We first investigate the linear hydrodynamic stability of these states by expanding the equations of motion about the states, and find that linear perturbations decay exponentially in time. We then study the effects of thermal fluctuations by formulating a Langevin equation for the particle motion which includes the Brownian stochastic force...