Autonomously Moving Nanorods at a Viscous Interface

Dhar, Prajnaparamita; Fischer, Thomas M.; Wang, Y.; Mallouk, Thomas E.; Paxton, Walter F.; Sen, Ayusman

doi:10.1021/nl052027s

Cited by 155 publications

(174 citation statements)

References 39 publications

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“…in a general form that applies to both passive (representing in this case the instantaneous flow) and active rotors as u β (r α ) = F a,p (r αβ )r αβ + A a,p (r αβ )ε βẑ ×r αβ (18) The first term is the radial flow, with F a = ( F cos φ )/(16πηr 2 ) and F p = 0. The second term is the azimuthal flow of strength A, with A p = τ e /(8πηr 2 ) and A a = (3 3 F sin φ )/(64πηr 4 ).…”

Section: -9 |mentioning

confidence: 99%

“…Several examples of active rotors are found in the living world, including sperm cells [8][9][10][11][12] , bacteria [13][14][15][16] and algae 17 near a solid surface. Various artificial swimmers, inspired by their living counterparts, have also been engineered over the past decade, and provide realizations of active rotors [18][19][20][21] . Other examples of internally driven or active rotors include the rotating motors found at the basal bodies of cilia and flagella anchored at the cell membrane 22 and ATPase molecular motors embedded in fluid membranes 23 .…”

Section: Introductionmentioning

confidence: 99%

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Cooperative self-propulsion of active and passive rotors

Fily

Baskaran

2012

Soft Matter

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Reynolds number passive and active rotors in a fluid, we characterize the hydrodynamic interactions among rotors and the resulting dynamics of a pair of interacting rotors. This allows us to treat in a common framework passive or externally driven rotors, such as magnetic colloids driven by a rotating magnetic field, and active or internally driven rotors, such as sperm cells confined at boundaries. The hydrodynamic interaction of passive rotors is known to contain an azimuthal component ∼ 1/r 2 to dipolar order that can yield the recently discovered "cooperative self-propulsion" of a pair of rotors of opposite vorticity. While this interaction is identically zero for active rotors as a consequence of torque balance, we show that a ∼ 1/r 4 azimuthal component of the interaction arises in active systems to octupolar order. Cooperative self-propulsion, although weaker, can therefore also occur for pairs of active rotors.

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Section: -9 |mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cooperative self-propulsion of active and passive rotors

Fily

Baskaran

2012

Soft Matter

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“…Efforts in this area range from synthetic modifications on existing biomotors [1][2][3][4][5] to purely synthetic catalytic bimetallic nanomotors [5][6][7][8]. Motion of the synthetic motors has been achieved using a number of propulsion mechanisms including autodiffusiophoresis [9][10][11], autoelectrophoresis [6,7,[12][13][14], and bubble generation [15,16]. There are numerous reviews of motors and we point to Ebbens and Howse [17] for a general review of motors and to Paxton, Sen, and Mallouk [7] or Wang [18] for reviews of self-electrophoretic motors.…”

Section: Introductionmentioning

confidence: 99%

Diffusive behaviors of circle-swimming motors

Marine

Wheat

Ault³

et al. 2013

Phys. Rev. E

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Spherical catalytic micromotors fabricated as described in Wheat et al. [Langmuir 26, 13052 (2010)] show fuel concentration dependent translational and rotational velocity. The motors possess short-time and long-time diffusivities that scale with the translational and rotational velocity with respect to fuel concentration. The short-time diffusivities are two to three orders of magnitude larger than the diffusivity of a Brownian sphere of the same size, increase linearly with concentration, and scale as v 2 /2ω. The measured long-time diffusivities are five times lower than the short-time diffusivities, scale as v 2 /{2D r [1 + (ω/D r ) 2 ]}, and exhibit a maximum as a function of concentration. Maximums of effective diffusivity can be achieved when the rotational velocity has a higher order of dependence on the controlling parameter(s), for example fuel concentration, than the translational velocity. A maximum in diffusivity suggests that motors can be separated or concentrated using gradients in fuel concentration. The decrease of diffusivity with time suggests that motors will have a high collision probability in confined spaces and over short times; but will not disperse over relatively long distances and times. The combination of concentration dependent diffusive time scales and nonmonotonic diffusivity of circle-swimming motors suggests that we can expect complex particle responses in confined geometries and in spatially dependent fuel concentration gradients.

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“…A paradigmatic example is diffusiophoretic motion in chemical gradients [2]. Here, theoretical and experimental advances have lately furnished a good understanding [3][4][5][6][7][8][9]. Miscellaneous phoretic mechanisms are based, e.g., on gradients in temperature or electrical fields.…”

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confidence: 99%

Efficiency of Surface-Driven Motion: Nanoswimmers Beat Microswimmers

Sabass

Seifert

2010

Phys. Rev. Lett.

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Surface interactions provide a class of mechanisms which can be employed for propulsion of microand nanometer sized particles. We investigate the related efficiency of externally and self-propelled swimmers. A general scaling relation is derived showing that only swimmers whose size is comparable to, or smaller than, the interaction range can have appreciable efficiency. An upper bound for efficiency at maximum power is 1/2. Numerical calculations for the case of diffusiophoresis are found to be in good agreement with analytical expressions for the efficiency.

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Autonomously Moving Nanorods at a Viscous Interface

Cited by 155 publications

References 39 publications

Cooperative self-propulsion of active and passive rotors

Cooperative self-propulsion of active and passive rotors

Diffusive behaviors of circle-swimming motors

Efficiency of Surface-Driven Motion: Nanoswimmers Beat Microswimmers

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