Self-propulsion against a moving membrane: Enhanced accumulation and drag force.
Self-propulsion against a moving membrane: Enhanced accumulation and drag force.
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DOI：
10.1103/physreve.96.032601
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发表时间：
2017-09
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影响因子：
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通讯作者：
U. Marconi;A. Sarracino;C. Maggi;A. Puglisi
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文献类型：
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作者：
U. Marconi;A. Sarracino;C. Maggi;A. Puglisi
自推进（SP）是活性粒子（AP）的主要特征，如细菌或生物微马达，将它们与被动胶体区分开来。SP的一个著名的后果是在静态界面处积累，即使在没有流体动力学相互作用的情况下。在这里，我们解决的作用SP之间的相互作用AP和移动的半透膜。特别是，我们实现了一个模型的非相互作用的AP在一个通道中穿过一个部分可穿透的墙壁，以恒定的速度C移动。相对于c>0的被动胶体和c=0的AP的情况，具有有限c的AP显示出在障碍物前方的积聚的增强，并且经历大大增加的拖曳力。这种效应可以理解为在颗粒和膜之间的界面处局部化的有效电势，其高度与cτ/π成比例，其中τ是AP的重定向时间，π是表征表面光滑度的宽度（对于硬核障碍物，π →0）。一个近似的分析方案是能够重现所观察到的密度分布和测量的阻力，在非常好的协议与数值模拟。这里讨论的效果可以用于自动选择和过滤AP与所需的参数。
Self-propulsion (SP) is a main feature of active particles (AP), such as bacteria or biological micromotors, distinguishing them from passive colloids. A renowned consequence of SP is accumulation at static interfaces, even in the absence of hydrodynamic interactions. Here we address the role of SP in the interaction between AP and a moving semipermeable membrane. In particular, we implement a model of noninteracting AP in a channel crossed by a partially penetrable wall, moving at a constant velocity c. With respect to both the cases of passive colloids with c>0 and AP with c=0, the AP with finite c show enhancement of accumulation in front of the obstacle and experience a largely increased drag force. This effect is understood in terms of an effective potential localised at the interface between particles and membrane, of height proportional to cτ/ξ, where τ is the AP's reorientation time and ξ the width characterizing the surface's smoothness (ξ→0 for hard core obstacles). An approximate analytical scheme is able to reproduce the observed density profiles and the measured drag force, in very good agreement with numerical simulations. The effects discussed here can be exploited for automatic selection and filtering of AP with desired parameters.