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Active Brownian particles and run-and-tumble particles separate inside a maze

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ABSTRACT

A diverse range of natural and artificial self-propelled particles are known and are used nowadays. Among them, active Brownian particles (ABPs) and run-and-tumble particles (RTPs) are two important classes. We numerically study non-interacting ABPs and RTPs strongly confined to different maze geometries in two dimensions. We demonstrate that by means of geometrical confinement alone, ABPs are separable from RTPs. By investigating Matryoshka-like mazes with nested shells, we show that a circular maze has the best filtration efficiency. Results on the mean first-passage time reveal that ABPs escape faster from the center of the maze, while RTPs reach the center from the rim more easily. According to our simulations and a rate theory, which we developed, ABPs in steady state accumulate in the outermost region of the Matryoshka-like mazes, while RTPs occupy all locations within the maze with nearly equal probability. These results suggest a novel technique for separating different types of self-propelled particles by designing appropriate confining geometries without using chemical or biological agents.

No MeSH data available.


ABP and RTP inside the non-regular maze.(a) MFPT versus Pr. Error bars have the same size as the symbols. (b) Stationary probability distributions of an ABP (first row) and an RTP (second row). The color bar shows the logarithmic scale for probability covering five orders of magnitude.
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f7: ABP and RTP inside the non-regular maze.(a) MFPT versus Pr. Error bars have the same size as the symbols. (b) Stationary probability distributions of an ABP (first row) and an RTP (second row). The color bar shows the logarithmic scale for probability covering five orders of magnitude.

Mentions: Finally, we investigated the non-regular maze of Fig. 1(c). In contrast to the nested mazes, no significant difference between the MFPTs of an ABP and an RTP are observable in Fig. 7(a). This is due to two features: first of all, the pattern is irregular and second, nested structures as in the regular mazes are absent. In particular, the second feature generated the difference between both types of active particle. For example, whenever an ABP, starting from the outermost zone of the circular maze, enters the 4th opening at large Pr, it is more probable for it to return to the outermost zone rather than to enter the 3rd opening, since for most of the time its orientation points radially outwards. Therefore, the nested structure of Matryoshka-like mazes drastically decreases the probability for the ABP to enter the inner regions of the maze and amplifies the difference between the two active-particle types. This feature is missing in the non-regular maze.


Active Brownian particles and run-and-tumble particles separate inside a maze
ABP and RTP inside the non-regular maze.(a) MFPT versus Pr. Error bars have the same size as the symbols. (b) Stationary probability distributions of an ABP (first row) and an RTP (second row). The color bar shows the logarithmic scale for probability covering five orders of magnitude.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120314&req=5

f7: ABP and RTP inside the non-regular maze.(a) MFPT versus Pr. Error bars have the same size as the symbols. (b) Stationary probability distributions of an ABP (first row) and an RTP (second row). The color bar shows the logarithmic scale for probability covering five orders of magnitude.
Mentions: Finally, we investigated the non-regular maze of Fig. 1(c). In contrast to the nested mazes, no significant difference between the MFPTs of an ABP and an RTP are observable in Fig. 7(a). This is due to two features: first of all, the pattern is irregular and second, nested structures as in the regular mazes are absent. In particular, the second feature generated the difference between both types of active particle. For example, whenever an ABP, starting from the outermost zone of the circular maze, enters the 4th opening at large Pr, it is more probable for it to return to the outermost zone rather than to enter the 3rd opening, since for most of the time its orientation points radially outwards. Therefore, the nested structure of Matryoshka-like mazes drastically decreases the probability for the ABP to enter the inner regions of the maze and amplifies the difference between the two active-particle types. This feature is missing in the non-regular maze.

View Article: PubMed Central - PubMed

ABSTRACT

A diverse range of natural and artificial self-propelled particles are known and are used nowadays. Among them, active Brownian particles (ABPs) and run-and-tumble particles (RTPs) are two important classes. We numerically study non-interacting ABPs and RTPs strongly confined to different maze geometries in two dimensions. We demonstrate that by means of geometrical confinement alone, ABPs are separable from RTPs. By investigating Matryoshka-like mazes with nested shells, we show that a circular maze has the best filtration efficiency. Results on the mean first-passage time reveal that ABPs escape faster from the center of the maze, while RTPs reach the center from the rim more easily. According to our simulations and a rate theory, which we developed, ABPs in steady state accumulate in the outermost region of the Matryoshka-like mazes, while RTPs occupy all locations within the maze with nearly equal probability. These results suggest a novel technique for separating different types of self-propelled particles by designing appropriate confining geometries without using chemical or biological agents.

No MeSH data available.