Magnetic Actuation of Surface Walkers: The Effects of Confinement and Inertia
Magnetic Actuation of Surface Walkers: The Effects of Confinement and Inertia
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DOI：
10.1021/acs.langmuir.9b03487
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发表时间：
2020-06-30
期刊：
影响因子：
3.9
通讯作者：
Tao, Wen-Quan
中科院分区：
文献类型：
--
作者：
Fang, Wen-Zhen;Ham, Seokgyun;Tao, Wen-Quan
在磁场的驱动下，靠近壁面的粒子的旋转可以被纠正为净平移。这样驱动的粒子，或表面步行者，是一种活性胶体，在生物学和微流体学中有应用。在这里，我们调查的运动球面步行者之间的两个墙壁使用模拟的基础上浸入边界格子玻尔兹曼方法。限制的程度和限制壁的性质（滑移与非滑移）显著影响粒子的平移速度，甚至可以反转其平移方向。当旋转雷诺数Re ω大于1时，惯性效应降低了磁场的临界频率，超过该临界频率，球体不再能够跟随外部旋转场。当球体被限制在无滑移壁附近时，临界频率的降低尤其明显。当Re-ω增加到超过1时，即使当球体仍然可以在同步状态下旋转时，其平移雷诺数Re-T也不再与Re-ω线性增加，并且当Re-ω超过类似于10时甚至减小。
Driven by a magnetic field, the rotation of a particle near a wall can be rectified into a net translation. The particles thus actuated, or surface walkers, are a kind of active colloid that finds application in biology and microfluidics. Here, we investigate the motion of spherical surface walkers confined between two walls using simulations based on the immersed-boundary lattice Boltzmann method. The degree of confinement and the nature of the confining walls (slip vs no-slip) significantly affect a particle's translational speed and can even reverse its translational direction. When the rotational Reynolds number Re-omega, is larger than 1, inertia effects reduce the critical frequency of the magnetic field, beyond which the sphere can no longer follow the external rotating field. The reduction of the critical frequency is especially pronounced when the sphere is confined near a no-slip wall. As Re-omega, increases beyond 1, even when the sphere can still rotate in the synchronous regime, its translational Reynolds number Re-T no longer increases linearly with Re-omega, and even decreases when Re-omega exceeds similar to 10.