Ellipsoidal Brownian self-driven particles in a magnetic field

Fan, Wai-Tong Louis; Pak, On Shun; Sandoval, Mario

doi:10.1103/physreve.95.032605

Cited by 15 publications

(6 citation statements)

References 32 publications

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“…An ongoing field of study is the question how the addition of external forces influences the force-free propulsion of active particles. An example are self-propelled particles or particle chains with additional magnetic moments that alter the effective diffusion constant [40] or give rise to new interesting features such as bifurcations and instabilities of linear molecules or rings made of microswimmers [23,41]. A very natural influence to consider is gravity.…”

Section: Introductionmentioning

confidence: 99%

Gravity-induced dynamics of a squirmer microswimmer in wall proximity

et al. 2018

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We perform hydrodynamic simulations using the method of multi-particle collision dynamics and a theoretical analysis to study a single squirmer microswimmer at high Péclet number, which moves in a low Reynolds number fluid and under gravity. The relevant parameters are the ratio α of swimming to bulk sedimentation velocity and the squirmer type β. The combination of self-propulsion, gravitational force, hydrodynamic interactions with the wall, and thermal noise leads to a surprisingly diverse behavior. At a > 1 we observe cruising states, while for a < 1 the squirmer resides close to the bottom wall with the motional state determined by stable fixed points in height and orientation. They strongly depend on the squirmer type β. While neutral squirmers permanently float above the wall with upright orientation, pullers float for α larger than a threshold value a th and are pinned to the wall below a th . In contrast, pushers slide along the wall at lower heights, from which thermal orientational fluctuations drive them into a recurrent floating state with upright orientation, where they remain on the timescale of orientational persistence.

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Section: Introductionmentioning

confidence: 99%

Gravity-induced dynamics of a squirmer microswimmer in wall proximity

et al. 2018

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“…Before analyzing the orientational fluctuations in the ribbon, we have first characterized the thermal motion of a single ellipsoid in absence and in presence of an external field. The dynamics of an individual ellipsoid in water has been treated in different works [25][26][27][28][29], and thus here will be only briefly described. In the absence of a magnetic field, the anisotropic shape of the particle causes a non trivial coupling between its rotational and translational motion.…”

Section: Single Particle Dynamicsmentioning

confidence: 99%

Orientational dynamics of fluctuating dipolar particles assembled in a mesoscopic colloidal ribbon

et al. 2017

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We combine experiments and theory to investigate the dynamics and orientational fluctuations of ferromagnetic microellipsoids that form a ribbonlike structure due to attractive dipolar forces. When assembled in the ribbon, the ellipsoids display orientational thermal fluctuations with an amplitude that can be controlled via application of an in-plane magnetic field. We use video microscopy to investigate the orientational dynamics in real time and space. Theoretical arguments are used to derive an analytical expression that describes how the distribution of the different angular configurations depends on the strength of the applied field. The experimental data are in good agreement with the developed model for all the range of field parameters explored. Understanding the role of fluctuations in chains composed of dipolar particles is important not only from a fundamental point of view, but it may also help understanding the stability of such structures against thermal noise, which is relevant in microfluidics and laboratory-on-a-chip applications.

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“…Active Brownian particle in a Newtonian bath, when subjected to an external magnetic field exhibits exotic transient and steady state properties [57][58][59][60][61][62]. In our previous work, we observed that a harmonically confined active Ornstein-Uhlenbeck particle (AOUP), while selfpropelling in a viscoelastic environment in the presence of a magnetic field features a novel phase transition from diamagnetic to paramagnetic phase [62].…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic response of an active particle under the action of magnetic field

Muhsin¹,

Adersh²,

Sahoo³

2023

Preprint

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We consider the dynamics of a charged inertial active Ornstein-Uhlenbeck particle in a viscoelastic suspension under the action of an uniform magnetic field. With the help of both numerical simulation and analytical framework, we exactly investigate the viscoelastic response of the particle to the magnetic field by means of particle trajectories, mean displacement, and mean square displacement (MSD) calculations. The simulated particle trajectories and MSD calculations reveal that the steady state response of a confined harmonic particle to the magnetic field show interesting features due to the complex interplay of underlying physical processes such as elastic dissipation and active fluctuations in the medium. When the activity time scale of the dynamics is larger than the elastic dissipation timescale (or vice-versa), the steady state MSD shows an enhancement (or suppression) with increase in the field strength. In both the cases, for very strong magnetic field the MSD interestingly approaches the value at the equilibrium limit where the generalized fluctuation dissipation relation is satisfied and the the particle behaves like an inertial passive Brownian particle. Thus, for a finite magnetic field, the system exhibits a re-entrant type transition from active to passive and then to active behaviour with persistence of elastic dissipation in the medium. However, for a free particle, the overall displacement covered always gets suppressed with increase in the strength of the magnetic field and finally approaches zero for a very strong magnetic field.

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Ellipsoidal Brownian self-driven particles in a magnetic field

Cited by 15 publications

References 32 publications

Gravity-induced dynamics of a squirmer microswimmer in wall proximity

Gravity-induced dynamics of a squirmer microswimmer in wall proximity

Orientational dynamics of fluctuating dipolar particles assembled in a mesoscopic colloidal ribbon

Viscoelastic response of an active particle under the action of magnetic field

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