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


Circular (a), square (b), and non-regular maze (c) used in Brownian dynamics simulations. The disks indicate the initial particle positions, where simulations start. In (a) and (b) green refers to the outwards case and red to the inwards case, respectively. Arrows indicate the initial velocity direction and numbers show the opening index.
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f1: Circular (a), square (b), and non-regular maze (c) used in Brownian dynamics simulations. The disks indicate the initial particle positions, where simulations start. In (a) and (b) green refers to the outwards case and red to the inwards case, respectively. Arrows indicate the initial velocity direction and numbers show the opening index.

Mentions: In this article, we present such a strategy by investigating active particles in suitable geometries analogous to mazes, which are illustrated in Fig. 1. Mazes or labyrinths are interesting complex geometries and solving them, i.e., proceeding from the entrance to the exit, has been a challenging problem for many centuries. For example, using chemotaxis, active particles are able to solve mazes and find the shortest path towards the exit575859. Here, we consider non-interacting ABPs and RTPs inside the different two-dimensional mazes of Fig. 1, but without any chemical field. Using computer simulations to determine mean first-passage times and stationary probability distributions, we demonstrate that ABPs are faster than RTPs in moving from the center to the rim of circular and square mazes, while RTPs reach the center more easily. This suggests the nested regular mazes of Fig. 1(a) and (b) as excellent tools for separating active particles from each other, with an advantage for the circular shape as we will demonstrate.


Active Brownian particles and run-and-tumble particles separate inside a maze
Circular (a), square (b), and non-regular maze (c) used in Brownian dynamics simulations. The disks indicate the initial particle positions, where simulations start. In (a) and (b) green refers to the outwards case and red to the inwards case, respectively. Arrows indicate the initial velocity direction and numbers show the opening index.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Circular (a), square (b), and non-regular maze (c) used in Brownian dynamics simulations. The disks indicate the initial particle positions, where simulations start. In (a) and (b) green refers to the outwards case and red to the inwards case, respectively. Arrows indicate the initial velocity direction and numbers show the opening index.
Mentions: In this article, we present such a strategy by investigating active particles in suitable geometries analogous to mazes, which are illustrated in Fig. 1. Mazes or labyrinths are interesting complex geometries and solving them, i.e., proceeding from the entrance to the exit, has been a challenging problem for many centuries. For example, using chemotaxis, active particles are able to solve mazes and find the shortest path towards the exit575859. Here, we consider non-interacting ABPs and RTPs inside the different two-dimensional mazes of Fig. 1, but without any chemical field. Using computer simulations to determine mean first-passage times and stationary probability distributions, we demonstrate that ABPs are faster than RTPs in moving from the center to the rim of circular and square mazes, while RTPs reach the center more easily. This suggests the nested regular mazes of Fig. 1(a) and (b) as excellent tools for separating active particles from each other, with an advantage for the circular shape as we will demonstrate.

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.