Avalanche dynamics for active matter in heterogeneous media

Reichhardt, C.

doi:10.1088/1367-2630/aaa392

Cited by 43 publications

(35 citation statements)

References 47 publications

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“…Previous studies of active particle motion in two-dimensional (2D) random media suggest that pore-scale confinement does not merely rescale long-time diffusive behavior, but fundamentally changes how active particles move; [52][53][54][55] our work provides an experimental complement to this body of work. Moreover, the revised picture of motility we present yields a way to predict the long-time bacterial diffusivity through a random walk model of hopping between traps.…”

Section: Discussionmentioning

confidence: 70%

Bacterial hopping and trapping in porous media

2019

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Diverse processes—e.g. bioremediation, biofertilization, and microbial drug delivery—rely on bacterial migration in disordered, three-dimensional (3D) porous media. However, how pore-scale confinement alters bacterial motility is unknown due to the opacity of typical 3D media. As a result, models of migration are limited and often employ ad hoc assumptions. Here we reveal that the paradigm of run-and-tumble motility is dramatically altered in a porous medium. By directly visualizing individual Escherichia coli , we find that the cells are intermittently and transiently trapped as they navigate the pore space, exhibiting diffusive behavior at long time scales. The trapping durations and the lengths of “hops” between traps are broadly distributed, reminiscent of transport in diverse other disordered systems; nevertheless, we show that these quantities can together predict the long-time bacterial translational diffusivity. Our work thus provides a revised picture of bacterial motility in complex media and yields principles for predicting cellular migration.

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Section: Discussionmentioning

confidence: 70%

Bacterial hopping and trapping in porous media

2019

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“…We anticipate that our data could help to test current models, and could motivate the development of new models, of motility in heterogeneous environments. [58][59][60][61][62][63][64][65][66][67] Indeed, the process of hopping and trapping bears striking similarities with the entropic trapping of thermally-activated polymers in disordered porous media; thus, by analogy, we hypothesize that bacterial trapping can be described by the parameter β ≡ X/C 0 , analogous to T /T g for thermally-equilibrated systems. Consistent with this hypothesis, we find that the power-law exponent α ≡ 1 + β decreases with decreasing pore size, which increases C 0 , and with decreasing swimming speed, which decreases X.…”

Section: Discussionmentioning

confidence: 99%

Confinement and activity regulate bacterial motion in porous media

Bhattacharjee

Datta

2019

Soft Matter

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Understanding how bacteria move in porous media is critical to applications in healthcare, agriculture, environmental remediation, and chemical sensing. Recent work has demonstrated that E. coli, which moves by run-and-tumble dynamics in a homogeneous medium, exhibits a new form of motility when confined in a disordered porous medium: hopping-and-trapping motility, in which cells perform rapid, directed hops punctuated by intervals of slow, undirected trapping. Here, we use direct visualization to shed light on how these processes depend on pore-scale confinement and cellular activity. We find that hopping is determined by pore-scale confinement, and is independent of cellular activity; by contrast, trapping is determined by the competition between pore-scale confinement and cellular activity, as predicted by an entropic trapping model. These results thus help to elucidate the factors that regulate bacterial motion in porous media, and could help aid the development of new models of motility in heterogeneous environments.

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“…The onset of clustering or swarming can strongly affect the overall mobility of the particles when obstacles or pinning are present [39][40][41][42][43][44] . In studies of active matter moving under a drift force through obstacles, the mobility is maximized at an optimal run length since small levels of activity can break apart the clogging or jamming induced by the quenched disorder, but high levels of activity generate self-induced clustering that reduces the mobility 44,45 .…”

Section: Introductionmentioning

confidence: 99%

Laning and clustering transitions in driven binary active matter systems

2018

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It is well known that a binary system of nonactive disks that experience driving in opposite directions exhibits jammed, phase separated, disordered, and laning states. In active matter systems, such as a crowd of pedestrians, driving in opposite directions is common and relevant, especially in conditions which are characterized by high pedestrian density and emergency. In such cases, the transition from laning to disordered states may be associated with the onset of a panic state. We simulate a laning system containing active disks that obey run-and-tumble dynamics, and we measure the drift mobility and structure as a function of run length, disk density, and drift force. The activity of each disk can be quantified based on the correlation timescale of the velocity vector. We find that in some cases, increasing the activity can increase the system mobility by breaking up jammed configurations; however, an activity level that is too high can reduce the mobility by increasing the probability of disk-disk collisions. In the laning state, the increase of activity induces a sharp transition to a disordered strongly fluctuating state with reduced mobility. We identify a novel drive-induced clustered laning state that remains stable even at densities below the activity-induced clustering transition of the undriven system. We map out the dynamic phase diagrams highlighting transitions between the different phases as a function of activity, drive, and density.

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Avalanche dynamics for active matter in heterogeneous media

Cited by 43 publications

References 47 publications

Bacterial hopping and trapping in porous media

Bacterial hopping and trapping in porous media

Confinement and activity regulate bacterial motion in porous media

Laning and clustering transitions in driven binary active matter systems

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