Chemokinetic Scattering, Trapping, and Avoidance of Active Brownian Particles

Kromer, Justus A.; Cruz, Noelia de la; Friedrich, Benjamin M.

doi:10.1103/physrevlett.124.118101

Cited by 10 publications

(26 citation statements)

References 40 publications

(88 reference statements)

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“…We derive approximations for the rate of target encounters and the scaling of the optimal time spent in inner search (‘giving‐up time’) with target density for three exemplary inner search strategies. We find that a recently suggested inner search strategy, which exploits a chemotactic scattering effect, performs better than ballistic or Brownian inner search; yet, this advanced strategy requires that the ABP possess internal memory of recent search attempts [5] . Independent of the chosen inner search strategy, the optimal giving‐up time decreases with target density ρ as ∼ ρ −2/3 , reflecting an exploration‐exploitation trade‐off [42] between continuing inner search to eventually find the nearest target, or searching elsewhere for other targets.…”

Section: Figurementioning

confidence: 92%

“…[5], a minimal model of an Active Brownian Particle (ABP) that regulates its directional persistence in response to local cues was proposed. For ABPs without internal states or memory, such a chemokinesis strategy does not provide any advantage compared to simple ballistic motion [5] . Yet, a single binary or tertiary internal state allows these agents to increase their rate of target encounters substantially.…”

Section: Figurementioning

confidence: 99%

“…We first consider the case of a single spherical target of radius R 0 located at

R = 0

. Due to spherical symmetry, the time‐dependent distance

R (t) = |R (t)|

of the agent to the origin, and the time‐dependent angle

ψ (t)

enclosed by the tangent t and the radial direction

{bolde}_{R} = - R / R

, decouple from other coordinates [5,44,45]

true \overset{R}{true} = - v \cos ψ,

true \overset{ψ}{true} = \frac{v}{R} \sin ψ + \sqrt{2 D_{rot}} ξ ((), t) + D_{rot} \cot ψ .

…”

Section: Figurementioning

confidence: 99%

“…Intriguingly, the case of a position‐dependent speed

v (boldx)

( orthokinesis ) [6] , and the case of a position‐dependent rotational diffusion coefficient

D_{rot} (boldx)

( klinokinesis ) can be mapped onto each other using a local re‐parameterization of time: [5] if we formally re‐scale local time by a factor

Φ = v_{0} / v (boldx)

, then ABPs apparently move with constant speed

v_{0} = v (boldx) Φ

, while the new rotational diffusion coefficient reads

D_{rot} Φ

. Thus, the case of a position‐dependent speed can be mapped on the case of a position‐dependent rotational diffusion coefficient, and vice versa.…”

Section: Figurementioning

confidence: 99%

“…We emphasize that the shapes of trajectories do not change under such time re‐parametrization. For ABP with constant speed, it is known that the steady‐state probability distribution

p^{*} (boldx)

is spatially homogeneous, even if the rotational diffusion coefficient

D_{rot} (boldx)

depends on position [5,46,47] …”

Section: Figurementioning

confidence: 99%

See 4 more Smart Citations

Composite Search of Active Particles in Three‐dimensional Space Based on Non‐directional Cues

2021

Self Cite

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We theoretically address minimal search strategies of self‐propelled particles towards hidden targets in three‐dimensional space. The particles can sense if targets are close, e. g., by detecting released signaling molecules, but they cannot deduce directional cues. We investigate composite search strategies, where particles switch between extensive outer search and intensive inner search; inner search is started when proximity of a target is detected and ends when a certain inner search time has elapsed. In the simplest strategy, active particles move ballistically during outer search, and transiently reduce their directional persistence during inner search. In a second, adaptive strategy, particles exploit a dynamic scattering effect by reducing directional persistence only outside a well‐defined target zone. These two search strategies require only minimal information processing capabilities, yet increase target encounter rates substantially. The optimal inner search time scales as power‐law with exponent −2/3 with target density, reflecting a trade‐off between exploration and exploitation.

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Section: Figurementioning

confidence: 92%

Section: Figurementioning

confidence: 99%

“…We first consider the case of a single spherical target of radius R 0 located at

R = 0

. Due to spherical symmetry, the time‐dependent distance

R (t) = |R (t)|

of the agent to the origin, and the time‐dependent angle

ψ (t)

enclosed by the tangent t and the radial direction

{bolde}_{R} = - R / R

, decouple from other coordinates [5,44,45]

true \overset{R}{true} = - v \cos ψ,

true \overset{ψ}{true} = \frac{v}{R} \sin ψ + \sqrt{2 D_{rot}} ξ ((), t) + D_{rot} \cot ψ .

…”

Section: Figurementioning

confidence: 99%

“…Intriguingly, the case of a position‐dependent speed

v (boldx)

( orthokinesis ) [6] , and the case of a position‐dependent rotational diffusion coefficient

D_{rot} (boldx)

( klinokinesis ) can be mapped onto each other using a local re‐parameterization of time: [5] if we formally re‐scale local time by a factor

Φ = v_{0} / v (boldx)

, then ABPs apparently move with constant speed

v_{0} = v (boldx) Φ

, while the new rotational diffusion coefficient reads

D_{rot} Φ

. Thus, the case of a position‐dependent speed can be mapped on the case of a position‐dependent rotational diffusion coefficient, and vice versa.…”

Section: Figurementioning

confidence: 99%

“…We emphasize that the shapes of trajectories do not change under such time re‐parametrization. For ABP with constant speed, it is known that the steady‐state probability distribution

p^{*} (boldx)

is spatially homogeneous, even if the rotational diffusion coefficient

D_{rot} (boldx)

depends on position [5,46,47] …”

Section: Figurementioning

confidence: 99%

See 3 more Smart Citations

Composite Search of Active Particles in Three‐dimensional Space Based on Non‐directional Cues

2021

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Survival strategies of artificial active agents

Zanovello

Löffler

Caraglio

et al. 2023

Sci Rep

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Artificial cells can be engineered to display dynamics sharing remarkable features in common with the survival behavior of living organisms. In particular, such active systems can respond to stimuli provided by the environment and undertake specific displacements to remain out of equilibrium, e.g. by moving towards regions with higher fuel concentration. In spite of the intense experimental activity aiming at investigating this fascinating behavior, a rigorous definition and characterization of such “survival strategies” from a statistical physics perspective is still missing. In this work, we take a first step in this direction by adapting and applying to active systems the theoretical framework of Transition Path Theory, which was originally introduced to investigate rare thermally activated transitions in passive systems. We perform experiments on camphor disks navigating Petri dishes and perform simulations in the paradigmatic active Brownian particle model to show how the notions of transition probability density and committor function provide the pivotal concepts to identify survival strategies, improve modeling, and obtain and validate experimentally testable predictions. The definition of survival in these artificial systems paves the way to move beyond simple observation and to formally characterize, design and predict complex life-like behaviors.

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Active chiral molecules in activity gradients

Muzzeddu

Vuijk

Löwen

et al. 2022

The Journal of Chemical Physics

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While the behavior of active colloidal molecules is well studied by now for a constant activity, the effect of activity gradients is much less understood. Here we explore one of the simplest molecules in activity gradients, namely active chiral dimers composed of two particles with opposite active torques of the same magnitude. We show analytically that with increasing torque, the dimer switches its behavior from antichemotactic to chemotactic. The origin of the emergent chemotaxis is the cooperative exploration of activity gradient by the two particles. While one of the particles moves into higher activity regions, the other moves towards lower activity region resulting in a net bias in the direction of higher activity. We do a comparative study of chiral active particles with charged Brownian particles under magnetic field and show that despite the fundamental similarity in terms of their odd-diffusive behavior, their dynamics and chemotactic behavior are generally not equivalent. We demonstrate this explicitly in a dimer composed of oppositely charged active particles, which remains antichemotactic for any magnetic field.

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Chemokinetic Scattering, Trapping, and Avoidance of Active Brownian Particles

Cited by 10 publications

References 40 publications

Composite Search of Active Particles in Three‐dimensional Space Based on Non‐directional Cues

Composite Search of Active Particles in Three‐dimensional Space Based on Non‐directional Cues

Survival strategies of artificial active agents

Active chiral molecules in activity gradients

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