Drift instability in the motion of a fluid droplet with a chemically reactive surface driven by Marangoni flow

Yoshinaga, Natsuhiko; Nagai, Ken; Sumino, Yutaka; Kitahata, Hiroyuki

doi:10.1103/physreve.86.016108

Cited by 88 publications

(119 citation statements)

References 33 publications

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“…An oil droplet containing surfactant is an example of the second type. Such a droplet can move by diffusing surfactant into the surrounding media and its direction of motion is determined by initial fluctuations [3,4].…”

Section: Introductionmentioning

confidence: 99%

Relationship between the size of a camphor-driven rotor and its angular velocity

et al. 2017

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We consider a rotor made of two camphor disks glued below the ends of a plastic stripe. The disks are floating on a water surface and the plastic stripe does not touch the surface. The system can rotate around a vertical axis located at the center of the stripe. The disks dissipate camphor molecules. The driving momentum comes from the nonuniformity of surface tension resulting from inhomogeneous surface concentration of camphor molecules around the disks. We investigate the stationary angular velocity as a function of rotor radius ℓ. For large ℓ the angular velocity decreases for increasing ℓ. At a specific value of ℓ the angular velocity reaches its maximum and, for short ℓ it rapidly decreases. Such behaviour is confirmed by a simple numerical model. The model also predicts that there is a critical rotor size below which it does not rotate. Within the introduced model we analyze the type of this bifurcation.

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Section: Introductionmentioning

confidence: 99%

Relationship between the size of a camphor-driven rotor and its angular velocity

et al. 2017

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“…Self-propelled active droplets have been studied in various experiments, including droplets on interfaces [13,14], droplets coupled to a chemical wave [15], and droplets in a bulk fluid [16][17][18][19]. Theoretical treatments include a model of droplet motion in a chemically reacting fluid [20], studies of the stability of a resting droplet [21][22][23][24][25], and simulations of contractile droplets [26] and of droplets driven by nonlinear chemical kinetics [27].…”

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confidence: 99%

Swimming active droplet: A theoretical analysis

Schmitt¹,

Stark²

2013

EPL

100

145

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-Recently, an active microswimmer was constructed where a micron-sized droplet of bromine water was placed into a surfactant-laden oil phase. Due to a bromination reaction of the surfactant at the interface, the surface tension locally increases and becomes non-uniform. This drives a Marangoni flow which propels the squirming droplet forward. We develop a diffusionadvection-reaction equation for the order parameter of the surfactant mixture at the droplet interface using a mixing free energy. Numerical solutions reveal a stable swimming regime above a critical Marangoni number M but also stopping and oscillating states when M is increased further. The swimming droplet is identified as a pusher whereas in the oscillating state it oscillates between being a puller and a pusher.

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“…In reality, it may be given, for example, by a rigid self-propelling spherical Janus particle. Such Janus beads self-propel without the aid of any mechanically active joints, but via phoretic self-induced surrounding temperature or concentration gradients [28,[53][54][55][56][57][58][59][60][61][62][63]. In the following, we only consider one active bead per swimmer entity.…”

Section: Deformable Model Microswimmersmentioning

confidence: 99%

“…Due to the surface heterogeneity of Janus particles, they can selectively be heated on one side, or only the coverage of one of the two sides can catalyze chemical reactions. In this way, thermal or concentration gradients build up on length scales of the particle diameter, which in total leads to a net self-propulsion [61][62][63].…”

Section: Introductionmentioning

confidence: 99%

Getting drowned in a swirl: Deformable bead-spring model microswimmers in external flow fields

2016

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Deformability is a central feature of many types of microswimmers, e.g. for artificially generated self-propelled droplets. Here, we analyze deformable bead-spring microswimmers in an externally imposed solvent flow field as simple theoretical model systems. We focus on their behavior in a circular swirl flow in two spatial dimensions. Linear (straight) two-bead swimmers are found to circle around the swirl with a slight drift to the outside with increasing activity. In contrast to that, we observe for triangular three-bead or square-like four-bead swimmers a tendency of being drawn into the swirl and finally getting drowned, although a radial inward component is absent in the flow field. During one cycle around the swirl, the self-propulsion direction of an active triangular or square-like swimmer remains almost constant, while their orbits become deformed exhibiting an "egg-like" shape. Over time, the swirl flow induces slight net rotations of these swimmer types, which leads to net rotations of the egg-shaped orbits. Interestingly, in certain cases, the orbital rotation changes sense when the swimmer approaches the flow singularity. Our predictions can be verified in real-space experiments on artificial microswimmers.

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Drift instability in the motion of a fluid droplet with a chemically reactive surface driven by Marangoni flow

Cited by 88 publications

References 33 publications

Relationship between the size of a camphor-driven rotor and its angular velocity

Relationship between the size of a camphor-driven rotor and its angular velocity

Swimming active droplet: A theoretical analysis

Getting drowned in a swirl: Deformable bead-spring model microswimmers in external flow fields

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