Forward, reverse, and no motion of Marangoni surfers under confinement

Kang, Saeed Jafari; Sur, Samrat; Masoud, Hassan

doi:10.1103/physrevfluids.5.084004

Cited by 15 publications

(15 citation statements)

References 51 publications

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“…The future work should extend the numerical approach to higher Reynolds numbers in order to verify our scaling results for the swimming relation using, for example, the methods introduced in Ref. [ 37 ]. There are several aspects of the self-propulsion of PEG–alginate capsules, where we presented first experimental results but which deserve a much more detailed investigation in future work: curved trajectories, interactions with container walls, and swimmer-swimmer interaction.…”

Section: Discussionmentioning

confidence: 99%

“…A full quantitative theory of Marangoni boats including hydrodynamics, surfactant advection, direct Marangoni forces and Marangoni flows is still elusive despite previous progress [ 22 , 26 , 36 , 37 ]. Some theoretical approaches ignore the advection [ 35 , 38 , 39 ], several ignore the hydrodynamic flow fields [ 24 , 25 , 32 , 40 – 42 ] or approximate it by uniform flow [ 28 ], which clearly oversimplifies the description of surfactant transport.…”

Section: Introductionmentioning

confidence: 99%

“…Some theoretical approaches ignore the advection [ 35 , 38 , 39 ], several ignore the hydrodynamic flow fields [ 24 , 25 , 32 , 40 – 42 ] or approximate it by uniform flow [ 28 ], which clearly oversimplifies the description of surfactant transport. In particular, on the numerical side, a recent paper of Kang et al [ 37 ] provides progress by including advection fully into the numerical solution for an anisotropic Marangoni boat. A theoretical description is complicated by the fact that most of the Marangoni boats operate at higher Reynolds numbers, and fluid flow generated during Marangoni propulsion is typically featuring vortices [ 29 , 37 ].…”

Section: Introductionmentioning

confidence: 99%

“…In particular, on the numerical side, a recent paper of Kang et al [ 37 ] provides progress by including advection fully into the numerical solution for an anisotropic Marangoni boat. A theoretical description is complicated by the fact that most of the Marangoni boats operate at higher Reynolds numbers, and fluid flow generated during Marangoni propulsion is typically featuring vortices [ 29 , 37 ]. Miniaturization to the microscale leads to low Reynolds numbers.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, a half-spherical shape turns out to be very convenient for theoretical modeling, and has also been employed in Ref. [ 37 ]. For small Reynolds numbers, this geometry allows for a complete theoretical description of Marangoni boat propulsion by analyzing the coupled problems of surfactant diffusion and advection, fluid flow, which includes surfactant-induced fluid Marangoni flow, and surfactant adsorption at the air–water interface; we also include a possible evaporation of surfactant.…”

Section: Introductionmentioning

confidence: 99%

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Surfactant-loaded capsules as Marangoni microswimmers at the air–water interface: Symmetry breaking and spontaneous propulsion by surfactant diffusion and advection

et al. 2021

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We present a realization of a fast interfacial Marangoni microswimmer by a half-spherical alginate capsule at the air–water interface, which diffusively releases water-soluble spreading molecules (weak surfactants such as polyethylene glycol (PEG)), which act as “fuel” by modulating the air–water interfacial tension. For a number of different fuels, we can observe symmetry breaking and spontaneous propulsion although the alginate particle and emission are isotropic. The propulsion mechanism is similar to soap or camphor boats, which are, however, typically asymmetric in shape or emission to select a swimming direction. We develop a theory of Marangoni boat propulsion starting from low Reynolds numbers by analyzing the coupled problems of surfactant diffusion and advection and fluid flow, which includes surfactant-induced fluid Marangoni flow, and surfactant adsorption at the air–water interface; we also include a possible evaporation of surfactant. The swimming velocity is determined by the balance of drag and Marangoni forces. We show that spontaneous symmetry breaking resulting in propulsion is possible above a critical dimensionless surfactant emission rate (Peclet number). We derive the relation between Peclet number and swimming speed and generalize to higher Reynolds numbers utilizing the concept of the Nusselt number. The theory explains the observed swimming speeds for PEG–alginate capsules, and we unravel the differences to other Marangoni boat systems based on camphor, which are mainly caused by surfactant evaporation from the liquid–air interface. The capsule Marangoni microswimmers also exhibit surfactant-mediated repulsive interactions with walls, which can be qualitatively explained by surfactant accumulation at the wall. Graphic Abstract

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Surfactant-loaded capsules as Marangoni microswimmers at the air–water interface: Symmetry breaking and spontaneous propulsion by surfactant diffusion and advection

et al. 2021

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Active colloids on fluid interfaces

Deng

Molaei

Chisholm

et al. 2022

Current Opinion in Colloid & Interface Science

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Dynamics of a surface tension driven colloidal motor based on an active Janus particle encapsulated in a liquid drop

et al. 2023

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A colloidal motor driven by surface tension forces is theoretically designed by encapsulating an active Janus particle in a liquid drop which is immiscible in the suspending medium. The Janus particle produces an asymmetric flux of a solute species which induces surface tension gradients along the liquid–liquid interface between the drop and the surrounding fluid. The resulting Marangoni forces at the interface propel the compound drop/Janus particle system. The propulsion speeds of the motor are evaluated for a range of relative sizes and positions of the drop and the particle and across a range of transport properties of the drop and the suspending medium. It is demonstrated that the proposed design can produce higher propulsion velocities than the traditional Janus-particle-based colloidal motors propelled by neutral diffusiophoresis.

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Forward, reverse, and no motion of Marangoni surfers under confinement

Cited by 15 publications

References 51 publications

Surfactant-loaded capsules as Marangoni microswimmers at the air–water interface: Symmetry breaking and spontaneous propulsion by surfactant diffusion and advection

Surfactant-loaded capsules as Marangoni microswimmers at the air–water interface: Symmetry breaking and spontaneous propulsion by surfactant diffusion and advection

Active colloids on fluid interfaces

Dynamics of a surface tension driven colloidal motor based on an active Janus particle encapsulated in a liquid drop

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