Chiral motion in colloidal electrophoresis

Braverman, L. P.; Mowitz, Aaron; Witten, Thomas A.

doi:10.1103/physreve.101.062608

Cited by 3 publications

(10 citation statements)

References 33 publications

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“…This will only be established when the method uncovers novel behavior of driven colloids that can be demonstrated experimentally. Our paper in preparation [23] gives strong evidence that stokeslet objects are useful for predicting electrophoresis for a wide range of shapes and charge distributions. Thus there is reason for optimism that the reciprocal procedure developed here will prove useful in practice.…”

Section: Discussionmentioning

confidence: 89%

“…Without this boundary condition, the interior is free to flow. In our forthcoming explicit calculations [23], the { f i } generate a circulating flow inside the object surface as well as an exterior flow. Still, the force and torque agree well with known electrophoresis results.…”

Section: A Flow and Dissipationmentioning

confidence: 98%

“…A solid body can be approximated as a stokeslet object by replacing the body with a large number of stokeslets distributed over its surface [22]. By giving the stokeslets electric charge as well as hydrodynamic forcing, this approximation was shown to predict electrophoretic mobility successfully in simple cases [22,23].…”

Section: Introductionmentioning

confidence: 99%

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Adapting the Teubner reciprocal relations for stokeslet objects

Witten¹,

Mowitz²

2019

Preprint

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Self-propelled colloidal swimmers move by pushing the adjacent fluid backwards. The resulting motion of an asymmetric body depends on the profile of pushing velocity over its surface. We describe a method of predicting the motion arising from arbitrary velocity profiles over a given body shape, using a discrete-source "stokeslet" representation. The net velocity and angular velocity is a sum of contributions from each point on the surface. The contributions from a given point depend only on the shape. We give a numerical method to find these contributions in terms of the stokeslet positions defining the shape. Each contribution is determined by linear operations on the Oseen interaction matrix between pairs of stokeslets. We first adapt the Lorentz Reciprocal Theorem to discrete sources. We then use the theorem to implement the method of Teubner[1] to determine electrophoretic mobilities of nonuniformly charged bodies.

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Section: Discussionmentioning

confidence: 89%

Section: A Flow and Dissipationmentioning

confidence: 98%

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Adapting the Teubner reciprocal relations for stokeslet objects

Witten¹,

Mowitz²

2019

Preprint

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“…2014; Goddard, Nold & Kalliadasis 2016; Palanisamy& den Otter 2018). Our theoretical model is in the spirit of the Stokeslet object model which is a recently developed promising method because it enables the simplest form to extract the geometric properties governing the HIs of arbitrarily shaped particles (Goldfriend, Diamant & Witten 2015; Mowitz & Witten 2017; Witten & Mowitz 2019; Braverman, Mowitz, & Witten 2020; Witten & Diamant 2020). In this method, the object consists of a discrete set of points approximated as Stokeslets and separated by rigid distances, and the accuracy largely depends on the design of Stokeslets’ configuration (Goldfriend et al.…”

Section: Introductionmentioning

confidence: 99%

“…2015; Mowitz & Witten 2017; Witten & Mowitz 2019; Braverman et al. 2020; Witten & Diamant 2020). Our findings indicate that the complex groove-like channels with different cross-sections can be simplified by cylindrical tubes and the Stokeslet approximation can well capture the hydrodynamic features of colloidal ellipsoids.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic couplings of colloidal ellipsoids diffusing in channels

Zheng

Wang

et al. 2021

J. Fluid Mech.

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The hydrodynamic interactions (HIs) of two colloidal spheres characterized by the translation–translation (T–T) couplings have been studied under various confinements, but little is known regarding the HIs of anisotropic particles and rotational motions, which are common in nature and industry. Here, we study the T–T, rotation–rotation (R–R) and translation–rotation (T–R) hydrodynamic couplings of two colloidal ellipsoids sediment on the bottoms of channels in experiment, theory and simulation. We find that the degree of confinement and the particle shape anisotropy are critical tuning factors resulting in anomalous hydrodynamic and diffusive behaviours. The negative R–R coupling reflects the tendency of opposite rotations of two neighbouring ellipsoids. The positive T–R coupling reflects that an ellipsoid rotates away from the channel axis as another ellipsoid approaches. As the channel width increases, the positive T–T coupling changes to an abnormal negative coupling, indicating that the single-file diffusion can exist even in wide channels. By contrast, only positive T–T couplings were observed for spheres in channels. The T–T coupling increases with the aspect ratio p. The R–R coupling is the maximum at a moderate p ~ 2.8. The T–R coupling is the maximum at a moderate degree of confinement. The spatial range of HIs is longer than that of spheres and increases with p. We propose a simple model which reproduces some coupling phenomena between two ellipsoids, and it is further confirmed by low-Reynolds-number hydrodynamic simulation. These findings shed new light on anisotropic particle diffusion in porous media, transport through membranes, microfluidics and microrheology.

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A review of shaped colloidal particles in fluids: anisotropy and chirality

Witten

Diamant

2020

Rep. Prog. Phys.

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This review treats asymmetric colloidal particles moving through their host fluid under the action of some form of propulsion. The propulsion can come from an external body force or from external shear flow. It may also come from externally-induced stresses at the surface, arising from imposed chemical, thermal or electrical gradients. The resulting motion arises jointly from the driven particle and the displaced fluid. If the objects are asymmetric, every aspect of their motion and interaction depends on the orientation of the objects. This orientation in turn changes in response to the driving. The objects’ shape can thus lead to a range of emergent anisotropic and chiral motion not possible with isotropic spherical particles. We first consider what aspects of a body’s asymmetry can affect its drift through a fluid, especially chiral motion. We next discuss driving by injecting external force or torque into the particles. Then we consider driving without injecting force or torque. This includes driving by shear flow and driving by surface stresses, such as electrophoresis. We consider how time-dependent driving can induce collective orientational order and coherent motion. We show how a given particle shape can be represented using an assembly of point forces called a Stokeslet object. We next consider the interactions between anisotropic propelled particles, the symmetries governing the interactions, and the possibility of bound pairs of particles. Finally we show how the collective hydrodynamics of a suspension can be qualitatively altered by the particles’ shapes. The asymmetric responses discussed here are broadly relevant also for swimming propulsion of active micron-scale objects such as microorganisms.

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Chiral motion in colloidal electrophoresis

Cited by 3 publications

References 33 publications

Adapting the Teubner reciprocal relations for stokeslet objects

Adapting the Teubner reciprocal relations for stokeslet objects

Hydrodynamic couplings of colloidal ellipsoids diffusing in channels

A review of shaped colloidal particles in fluids: anisotropy and chirality

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