Chaotic advection and mixing by a pair of microrotors in a circular domain

Tallapragada, Phanindra; Sudarsanam, Senbagaraman

doi:10.1103/physreve.100.062207

Cited by 6 publications

(3 citation statements)

References 39 publications

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“…On the one hand, the appearance of Poisson structure in the active Cosserat crystal may be expected, since it can be shown that any odd-dimensional linear system yields a Poisson structure [45]. On the other hand, many previous examples of non-linear symplectic structure arising in the field of active matter share a common feature, namely the identification of orientation variables as conjugate momenta to displacements [26][27][28][29][30][31][32][33][34]. We suspect a similar structure is present in previous works involving two-body problems and that additional Lie symmetries could be found, reducing the dynamical space to a single conjugate pair.…”

Section: Discussionmentioning

confidence: 99%

“…While this form of Hamilton's equations is not symmetric under time reversal, reflecting the presence of irreversible forces and torques, the nonequilibrium potential implied by the Hamiltonian admits a conceptual simplification of the stability criteria derived directly from the linear equations of motion. We conclude with a discussion on how the long-ranged stability of the active Cosserat crystal differs from that of the active Cosserat medium and how this approach may be generally useful in overdamped active particle mechanics [26][27][28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

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Overdamped Lattice Dynamics of Sedimenting Active Cosserat Crystals

Bolitho¹,

Adhikari²

2022

Preprint

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Micropolar active matter requires for its kinematic description both positional and orientational degrees of freedom. Activity generates dynamic coupling between these kinematic variables that are absent in micropolar passive matter, such as the oriented crystals first studied by the Cosserat brothers. Here we study the effect of uniaxial activity on the dynamics of an initially crystalline state of spheroidal colloids sedimenting slowly in a viscous fluid remote from confining boundaries. Despite frictional overdamping by the fluid, the crystalline lattice admits traveling waves of position and orientation. At long wavelengths these obey a vector wave equation with Lamé constants determined by the activity. We find that at least one polarization mode of these waves is always unstable, leading to the melting of the crystal. These results are elucidated by identifying an odddimensional Poisson structure consisting of a Hamiltonian and an associated Casimir invariant, where linear combinations of position and orientation are identified as conjugate variables. Our results suggest that Poisson structures may exist generally for active particles in slow viscous flow and thereby allow equilibrium arguments to be applied in the presence of these dissipative systems.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Overdamped Lattice Dynamics of Sedimenting Active Cosserat Crystals

Bolitho¹,

Adhikari²

2022

Preprint

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“…Viscosity generally prevents turbulence from occurring in microfluidic devices, which prevents efficient mixing. Microrotors can generate strong vortices, which are an important component of efficient mixing, and thus effectively promotes the mixing of substances in the solution, making them effectively microscopic “stir bars” . Furthermore, the interactions among the individual microrotors can lead synergistically to collective phenomena such as active turbulence, making the mixing induced by the ensemble greater than the sum of that of the individual rotors.…”

Section: Applications Of Microrotorsmentioning

confidence: 99%

Active Synthetic Microrotors: Design Strategies and Applications

et al. 2023

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Microrotors are microscopic objects that convert energy stored in the environment into spontaneous rotation, in the form of spinning along an axis, rolling on a surface, or orbiting in circles. Because of its distinct dynamics and the vertical flows around it, a microrotor is potentially useful for applications, including drug delivery, minimally invasive surgery, fluid mixing, and sensing. It is also useful as a model system to probe the collective behaviors among rotating microobjects. In this review article, we comprehensively review the recent experimental progress in designing, synthesizing, and using microrotors. For applications, particular emphasis is placed on microfluidic mixing, biomedicine, and collective behaviors. In the end, we comment on how microrotors can be made more biocompatible and more controllable and rotate in more ways and the challenges therein. A key feature of this review article is to introduce three ways in which to classify a microrotor: the nature of its rotational behavior (spinners, rollers, or orbiters), the cause of its rotation (whether chiral symmetry is broken by shapes, chemical compositions, or the way energy is applied), and its power source (whether powered by chemical reactions, electric or magnetic fields, light, or ultrasound). This review article will help materials scientists and chemists in designing micromachines and microrotors, help engineers in finding appropriate microrotors for a specific application, and help physicists in finding appropriate model systems.

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Tadpole‐Shaped Catalytic Janus Microrotors Enabled by Facile and Controllable Growth of Silver Nanotails

Xiao

Zhou

et al. 2020

Adv Funct Materials

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Microrotors are an indispensable component in micromachines, yet their usefulness has been limited by a lack of simple, inexpensive, and controlled fabrication technique that yields microrotors of controlled shapes in large quantities. To address this challenge, the chemical synthesis, characterization, and activation of tadpole-shaped catalytic microrotors that consist of a spherical, platinum (Pt)-coated head and a silver (Ag) nano-tail of tunable lengths are reported herein. Importantly, this tail spontaneously grows on Pt in an aqueous solution of Ag + and hydrogen peroxide (H 2 O 2), at a speed of ≈100 nm s −1 , preferably along the Ag (111) plane. The growth of Ag nanowires is attributed to an electrochemical reaction occurring on a tapered Pt cap, a mechanism corroborated by control experiments with photo-active titania microspheres, which introduce the additional advantage of light-controlled growth. The presence of a long Ag nano-tail on a tadpole-shaped microrotor breaks its symmetry and induces rotation in H 2 O 2 , and its structure-dependent dynamics is quantitatively studied and supported by numerical simulation. The chemical synthesis of microrotors with Ag nano-tails will introduce new designs of micromachines of controlled dynamics, as well as functional materials and devices where mild, controllable, and facile growth of Ag nanostructures is desired.

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Chaotic advection and mixing by a pair of microrotors in a circular domain

Cited by 6 publications

References 39 publications

Overdamped Lattice Dynamics of Sedimenting Active Cosserat Crystals

Overdamped Lattice Dynamics of Sedimenting Active Cosserat Crystals

Active Synthetic Microrotors: Design Strategies and Applications

Tadpole‐Shaped Catalytic Janus Microrotors Enabled by Facile and Controllable Growth of Silver Nanotails

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