“…Here, remains large even for trace surfactant concentrations well into the surface-gaseous regime (Bławzdziewicz, Cristini & Loewenberg 1999). It also appears that, under typical circumstances, surface diffusivity of the surfactant is insufficient to relax interfacial incompressibility (Chisholm & Stebe 2021). Figure 7.Measured drag coefficient (black circles) of a spherical particle as a function of immersion level at an incompressible interface with at the limit of .…”
Section: Resultsmentioning
confidence: 99%
“…The analytical solutions of the flow field around asymmetric prolate and oblate particles in an unbounded fluid with no-slip boundary conditions on the particles are also known (Brenner 1963). In the case of a sphere moving along the interface between two fluids, however, the problem becomes more complex and cannot be solved analytically (Chisholm & Stebe 2021). This implies that the drag force on an adsorbed particle moving tangentially to an interface cannot be calculated analytically for arbitrary contact angles.…”
“…Here, remains large even for trace surfactant concentrations well into the surface-gaseous regime (Bławzdziewicz, Cristini & Loewenberg 1999). It also appears that, under typical circumstances, surface diffusivity of the surfactant is insufficient to relax interfacial incompressibility (Chisholm & Stebe 2021). Figure 7.Measured drag coefficient (black circles) of a spherical particle as a function of immersion level at an incompressible interface with at the limit of .…”
Section: Resultsmentioning
confidence: 99%
“…The analytical solutions of the flow field around asymmetric prolate and oblate particles in an unbounded fluid with no-slip boundary conditions on the particles are also known (Brenner 1963). In the case of a sphere moving along the interface between two fluids, however, the problem becomes more complex and cannot be solved analytically (Chisholm & Stebe 2021). This implies that the drag force on an adsorbed particle moving tangentially to an interface cannot be calculated analytically for arbitrary contact angles.…”
“…In the present work, we focused our attention on the situation in which the disk is physically adhered to the interface such that its motion is fully restricted. It is well known that at fluid–fluid interfaces with very large surface tension, contact-line pinning typically constrains the motion of embedded objects pronouncedly (Chisholm & Stebe 2021). With the possibility of exploiting this effect, an experimental realisation of our set-up for a rigid disk resting on an interface can be achieved.…”
Breaking spatial symmetry is an essential requirement for phoretic active particles to swim at low Reynolds number. This fundamental prerequisite for swimming at the micro scale is fulfilled either by chemical patterning of the surface of active particles or alternatively by exploiting geometrical asymmetries to induce chemical gradients and achieve self-propulsion. In the present paper, a far-field analytical model is employed to quantify the leading-order contribution to the induced phoretic velocity of a chemically homogeneous isotropic active colloid near a finite-sized disk of circular shape resting on an interface separating two immiscible viscous incompressible Newtonian fluids. To this aim, the solution of the phoretic problem is formulated as a mixed-boundary-value problem that is subsequently transformed into a system of dual integral equations on the inner and outer domains. Depending on the ratio of different involved viscosities and solute solubilities, the sign of phoretic mobility and chemical activity, as well as the ratio of particle–interface distance to the radius of the disk, the isotropic active particle is found to be repelled from the interface, be attracted to it, or reach a stable hovering state and remain immobile near the interface. Our results may prove useful in controlling and guiding the motion of self-propelled phoretic active particles near aqueous interfaces.
“…Less is known of particles straddling an interface between two fluids, where they are strongly trapped due to Pickering effect [25]. The hydrodynamic boundary condition at the contact line between the two fluids and the particle surface, can play a role both in the linear and orientational dynamics of the swimmer [26]. Simulations of self-diffusiophoretic colloids at fluid-fluid interface predicted an emergence of an aligning torque on a particle at an interface between two fluids with equal viscosities [27].…”
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