Brownian dynamics of confined suspensions of active microrollers

Usabiaga, Florencio Balboa; Delmotte, Blaise; Donev, Aleksandar

doi:10.1063/1.4979494

Cited by 44 publications

(76 citation statements)

References 62 publications

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“…Here, the goal of repulsive contact forces is to prevent overlaps while having as little influence as possible on the dynamics of the system. We therefore chose to use extremely short-range repulsive forces; in practice, we model contact forces with an exponentially decaying repulsive potential of the form [45]…”

Section: Particles With Finite Radiusmentioning

confidence: 99%

Hydrodynamically bound states of a pair of microrollers: A dynamical system insight

Delmotte

2019

Phys. Rev. Fluids

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Recent work has identified persistent cluster states which were shown to be assembled and held together by hydrodynamic interactions alone [Driscoll et al. (2017) Nature Physics, 13(4), 375]. These states were seen in systems of colloidal microrollers; microrollers are colloidal particles which rotate about an axis parallel to the floor and generate strong, slowly decaying, advective flows. To understand these bound states, we study a simple, yet rich, model system of two microrollers. Here we show that pairs of microrollers can exhibit hydrodynamic bound states whose nature depends on a dimensionless number, denoted B, that compares the relative strength of gravitational forces and external torques. Using a dynamical system framework, we characterize these various states in phase space and analyze the bifurcations of the system as B varies. In particular, we show that there is a critical value, B * , above which active flows can beat gravity and lead to stable motile orbiting, or "leapfrog", trajectories, reminiscent of the self-assembled motile structures, called "critters", observed by Driscoll et al. We identify the conditions for the emergence of these trajectories and study their basin of attraction. This work shows that a wide variety of stable bound states can be obtained with only two particles. Our results aid in understanding the mechanisms that lead to spontaneous self-assembly in hydrodynamic systems, such as microroller suspensions, as well as how to optimize these systems for particle transport. * blaise.delmotte@ladhyx.polytechnique.fr arXiv:1811.05168v4 [physics.flu-dyn]

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Section: Particles With Finite Radiusmentioning

confidence: 99%

Hydrodynamically bound states of a pair of microrollers: A dynamical system insight

Delmotte

2019

Phys. Rev. Fluids

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“…Choosing between the aforementioned methods depends on the shape of the colloids, the geometry of the system considered, and the level of resolution desired. For instance, to simulate the microroller instability, we used the analytic far-field mobility matrix for particles near a no-slip boundary [135], together with an iterative method to compute the Brownian velocities [143] and RFD [148], and with an efficient parallelization on GPU's, allowing us to run twenty thousand time iterations with more than thirty thousands particles in a few hours [162,163]. The design of efficient numerical methods for Brownian Dynamics is an active area of research.…”

Section: Discussionmentioning

confidence: 99%

Leveraging collective effects in externally driven colloidal suspensions: experiments and simulations

Driscoll

Delmotte

2019

Current Opinion in Colloid & Interface Science

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In this review article, we focus on collective motion in externally driven colloidal suspensions, as well as how these collective effects can be harnessed for use in microfluidic applications. We highlight the leading role of hydrodynamic interactions in the self-assembly, emergent behavior, transport, and mixing properties of colloidal suspensions. A special emphasis is given to recent numerical methods to simulate driven colloidal suspensions at large scales. In combination with experiments, they help us to understand emergent dynamics and to identify control parameters for both individual and collective motion in colloidal suspensions.

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“…We include a soft repulsive potential between the blobs and the wall of the form (44) but with d = a and r interpreted as the distance between the blobs and the wall. We use b = 0.1R H and Φ 0 = 4k B T as in [36], as this choice ensures that the steric time scale associated with the potential isn't much smaller than the diffusive time scale, while also maintaining a low probability of blob-wall overlaps. As in [24], we give each blob a buoyant mass of m e = 1.57 × 10 −11 mg and thus apply a gravitation force −m e gẑ on each of the 15 blobs, where g is the Earth's gravitational acceleration.…”

Section: Discussionmentioning

confidence: 99%

Brownian dynamics of fully confined suspensions of rigid particles without Green’s functions

Sprinkle

Donev

Bhalla

et al. 2019

The Journal of Chemical Physics

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We introduce a Rigid-Body Fluctuating Immersed Boundary (RB-FIB) method to perform large-scale Brownian dynamics simulations of suspensions of rigid particles in fully confined domains, without any need to explicitly construct Green's functions or mobility operators.In the RB-FIB approach, discretized fluctuating Stokes equations are solved with prescribed boundary conditions in conjunction with a rigid-body immersed boundary method to discretize arbitrarily-shaped colloidal particles with no-slip or active-slip prescribed on their surface. We design a specialized Split-Euler-Maruyama temporal integrator that uses a combination of random finite differences to capture the stochastic drift appearing in the overdamped Langevin equation. The RB-FIB method presented in this work only solves mobility problems in each time step using a preconditioned iterative solver, and has a computational complexity that scales linearly in the number of particles and fluid grid cells. We demonstrate that the RB-FIB method correctly reproduces the Gibbs-Boltzmann equilibrium distribution, and use the method to examine the time correlation functions for two spheres tightly confined in a cuboid. We model a quasi-two-dimensional colloidal crystal confined in a narrow microchannel and hydrodynamically driven across a commensurate periodic substrate potential mimicking the effect of a corrugated wall. We observe partial and full depinning of the colloidal monolayer from the substrate potential above a certain wall speed, consistent with a transition from static to kinetic friction through propagating kink solitons. Unexpectedly, we find that particles nearest the boundaries of the domain are the first to be displaced, followed by particles in the middle of the domain. * Electronic address: donev@courant.nyu.edu † Electronic address: n-patankar@northwestern.edu arXiv:1901.06427v1 [cond-mat.soft]

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Brownian dynamics of confined suspensions of active microrollers

Cited by 44 publications

References 62 publications

Hydrodynamically bound states of a pair of microrollers: A dynamical system insight

Hydrodynamically bound states of a pair of microrollers: A dynamical system insight

Leveraging collective effects in externally driven colloidal suspensions: experiments and simulations

Brownian dynamics of fully confined suspensions of rigid particles without Green’s functions

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