The motion of micro-swimmers over a cavity in a micro-channel.

Hu, Xiao; Chen, Weijin; Lin, Jianzhong; Nie, Deming; Zhu, Zuchao; Lin, Peifeng · Soft Matter · 2024

basic_science · Level V

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Abstract

This article combines the lattice Boltzmann method (LBM) with the squirmer model to investigate the motion of micro-swimmers in a channel-cavity system. The study analyses various influential factors, including the value of the squirmer-type factor (<i>β</i>), the swimming Reynolds number (Re<sub>p</sub>), the size of the cavity, initial position and particle size on the movement of micro-swimmers within the channel-cavity system. We simultaneously studied three types of squirmer models, Puller (<i>β</i> > 0), Pusher (<i>β</i> < 0), and Neutral (<i>β</i> = 0) swimmers. The findings reveal that the motion of micro-swimmers is determined by the value of <i>β</i> and Re<sub>p</sub>, which can be classified into six distinct motion modes. For Puller and Pusher, when the <i>β</i> value is constant, an increase in Re<sub>p</sub> will lead to transition in the motion mode. Moreover, the appropriate depth of cavity within the channel-cavity system plays a crucial role in capturing and separating Neutral swimmers. This study, for the first time, explores the effect of complex channel-cavity systems on the behaviour of micro-swimmers and highlights their separation and capture ability. These findings offer novel insights for the design and enhancement of micro-channel structures in achieving efficient separation and capture of micro-swimmers.