Colloid Transport by Interfacial Forces

Anderson, John L.

doi:10.1146/annurev.fl.21.010189.000425

Cited by 1,405 publications

(2,120 citation statements)

References 28 publications

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“…The net velocity of the motor is thus the slip velocity averaged over the motor surface. T his result should be familiar from the phoretic motion of spherical particles in the thin interfacial limit (Anderson 1989), where the reciprocal theorem fo r Stokes flow gives U phoreric = - § uslipdS/(4rr.a 2 ), in agreement with (2 6) for a sphe rical motor. Note that this fluid velocity is evaluated at the contact surface Sc, which is everywhere a distance 8 from the hydrodynamic no-slip surface s,,.…”

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confidence: 59%

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Non-spherical osmotic motor: chemical sailing

2014

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The behaviour of a non-spherical osmotic motor -an axisymmetric catalytic particle self-propelling in a dilute dispersion of reactant particles -is considered. In concrast to a conventional osmotic motor that creates differences in concentration, and hence in osmotic pressure, due to asymmetry in reaction rate along its surface (e.g. a Janus particle with reactive and non-reactive patches), a non-spherical particle is able to move even with uniform chemical activity on its surface. For small departures from a sphere the velocity of self-propulsion is proportional to the square of the non-sphericity or distortion of the particle shape. It is shown that the inclusion of hydrodynamic interactions (HI) may drastically change the self-propulsion. Except for very slow chemical reactions, even the direction of self-propulsion changes with and without HI. Numerical calculations at finite non-sphericity suggest that the maximum velocity of self-propulsion is obtained by a sail-like motor shape, leading to the name 'chemical sailing'. Moreover, no saturation in the speed of propulsion is found; the motor velocity increases as the area of this 'sail' grows and its thickness decreases. The self-propulsion of a non-spherical particle releasing products of a chemical reaction -a constant flux motor -is also considered.

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confidence: 59%

“…This colloidal versus continuum perspective was discussed in detail by Brady (20 I I ) in the context of classical diffusiophoresis (Anderson 1989) and is here extended to reactive particles of arbitrary shape.…”

Section: Introductionmentioning

confidence: 99%

Non-spherical osmotic motor: chemical sailing

2014

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“…The exact mechanism for the propulsion of these micro-swimmers is still a developing area of research and various models have been proposed. [156][157][158][159][160] The autonomous motion of meso-scale objects (a few mm) by bubble propulsion, as observed by Ismagilov, et. al., [160] is not responsible for the motion of nanorods, since no bubbles are observed on the nanorod surface.…”

Section: Janus and Patchy Particles In Chemical Environmentsmentioning

confidence: 88%

“…The gradients of fields such as concentration, temperature, or electric field can be used for colloid transport by interfacial forces. [156] The field gradient couples with the surface properties of the particle to produce slip velocity patterns, which results in a net propulsion of the particle. Such a diffusion-phoretic motion of a particle has been proposed by Golestanian et al [158] They propose that a particle with an asymmetric distribution of a catalyst on the surface propels itself due to an asymmetric distribution of reaction products generated by asymmetric surface catalytic activity.…”

Section: Janus and Patchy Particles In Chemical Environmentsmentioning

confidence: 99%

Fabrication, Assembly, and Application of Patchy Particles

Pawar

Kretzschmar

2010

Macromol. Rapid Commun.

442

411

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The site‐specific engineering of colloidal surfaces has provided a powerful approach to pushing the boundaries of today's materials research. The resulting surface‐anisotropic and patchy particles have become the center of vital research areas, ranging from the need for large‐scale fabrication techniques to exploring new applications of these materials. This Review summarizes patchy particle fabrication techniques, including but not limited to particle and nanosphere lithography and glancing‐angle deposition. The variety of existing patchy particle fabrication techniques is revealed and the need for a scalable approach to high‐volume patchy particle production is identified. Ongoing modeling efforts describing patchy particle interactions and properties are reviewed as potential predictive tools. Research endeavors that deal with the directed assembly of patchy particles in electric and magnetic fields, as well as with supraparticular assembly through chemical interactions, are discussed. The Review is concluded with a note on the future application of patchy particles as phoretic motors.magnified image

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“…The velocity field around a self-propelled particle can be analytically calculated from the Navier-Stokes equation. Here, we solve the Stokes equation, which neglects the effect of inertia due to very small Reynolds number, and consider the incompressible fluid condition [10,35]. Note that although MPC has the equation of state of an ideal gas, the compressibility effects of the associated flow fields have shown to be very small in the case of thermophoretic particles [35].…”

Section: Flow Field Around Phoretic Swimmersmentioning

confidence: 99%

Hydrodynamic simulations of self-phoretic microswimmers

2014

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A mesoscopic hydrodynamic model to simulate synthetic self-propelled Janus particles which is thermophoretically or diffusiophoretically driven is here developed. We first propose a model for a passive colloidal sphere which reproduces the correct rotational dynamics together with strong phoretic effect. This colloid solution model employs a multiparticle collision dynamics description of the solvent, and combines potential interactions with the solvent, with stick boundary conditions. Asymmetric and specific colloidal surface is introduced to produce the properties of self-phoretic Janus particles. A comparative study of Janus and microdimer phoretic swimmers is performed in terms of their swimming velocities and induced flow behavior. Self-phoretic microdimers display long range hydrodynamic interactions and can be characterized as pullers or pushers. In contrast, Janus particles are characterized by short range hydrodynamic interactions and behave as neutral swimmers. Our model nicely mimics those recent experimental realization of the self-phoretic Janus particles.

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Colloid Transport by Interfacial Forces

Cited by 1,405 publications

References 28 publications

Non-spherical osmotic motor: chemical sailing

Non-spherical osmotic motor: chemical sailing

Fabrication, Assembly, and Application of Patchy Particles

Hydrodynamic simulations of self-phoretic microswimmers

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