Pairwise hydrodynamic interactions of spherical colloids at a gas-liquid interface

Das, Subhabrata; Koplik, Joel; Somasundaran, P.; Maldarelli, Charles

doi:10.1017/jfm.2021.170

Cited by 7 publications

(5 citation statements)

References 68 publications

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“…This immersion force has been shown to be relevant even for submicron spheres, and in our experiments with particles of 500 nm to 2 μm, it has a role in the close packing of the opals. However, due to its diameter dependence, which is more pronounced than the dependence of the liquid drag force on the diameter, we argue that it was more significant for the 10 μm spheres, changing the overall fluid and self-assembly dynamics. On the other hand, we observed slow contact line velocities of the fluid for the 10 μm particle case (Video S2), which implies that there is a strong upward flux of liquid that resupplies evaporated solvents.…”

Section: Resultsmentioning

confidence: 80%

Rational Fabrication of Nano-to-Microsphere Polycrystalline Opals Using Slope Self-Assembly

et al. 2021

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Self-assembly of artificial opals has garnered significant interest as a facile nanofabrication technique capable of producing highly ordered structures for optical, electrochemical, biomolecular, and thermal applications. In these applications, the optimum opal particle diameter can vary by several orders of magnitude because the properties of the resultant structures depend strongly on the feature size. However, current opal fabrication techniques only produce high-quality structures over a limited range of sphere sizes or require complex processes and equipment. In this work, the rational and simple fabrication of polycrystalline opals with diameters between 500 nm and 10 μm was demonstrated using slope self-assembly of colloids suspended in ethanol–water. The role of the various process parameters was elucidated through a scaling-based model that accurately captures the variations of opal substrate coverage for spheres of size 2 μm or smaller. For spheres of 10 μm and larger, capillary forces were shown to play a key role in the process dynamics. Based on these insights, millimeter-scale monolayered opals were successfully fabricated, while centimeter-scale opals were possible with sparse sphere stacking or small uncovered areas. These insights provide a guide for the simple and fast fabrication of opals that can be used as optical coatings, templates for high power density electrodes, molecule templates, and high-performance thermo-fluidic devices.

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Section: Resultsmentioning

confidence: 80%

Rational Fabrication of Nano-to-Microsphere Polycrystalline Opals Using Slope Self-Assembly

et al. 2021

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“…It has been shown experimentally that the presence of surface roughness leads to pinning of the contact line. 38 The pinned contact line is also used for modeling single 37 and pair 39 particles at the interfaces. Due to pinning of the contact line, an extremely small deformation of the interface is needed to balance the torque acting on the particle, which justifies our approach of a non-rotating particle at a planar interface.…”

Section: Hydrodynamic Equationsmentioning

confidence: 99%

Drag on a spherical particle at the air–liquid interface: Interplay between compressibility, Marangoni flow, and surface viscosities

et al. 2021

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We investigate the flow of viscous interfaces carrying an insoluble surface active material, using numerical methods to shed light on the complex interplay between Marangoni stresses, compressibility, and surface shear and dilatational viscosities. We find quantitative relations between the drag on a particle and interfacial properties as they are required in microrheology, i.e., going beyond the asymptotic limits. To this end, we move a spherical particle probe at constant tangential velocity, symmetrically immersed at either the incompressible or compressible interface, in the presence and absence of surfactants, for a wide range of system parameters. A full three-dimensional finite element calculation is used to reveal the intimate coupling between the bulk and interfacial flows and the subtle effects of the different physical effects on the mixed-type velocity field that affects the drag coefficient, both in the bulk and at the interface. For an inviscid interface, the directed motion of the particle leads to a gradient in the concentration of the surface active species, which in turn drives a Marangoni flow in the opposite direction, giving rise to a force exerted on the particle. We show that the drag coefficient at incompressible interfaces is independent of the origin of the incompressibility (dilatational viscosity, Marangoni effects or a combination of both) and that its higher value can not only be related to the Marangoni effects, as suggested earlier. In confined flows, we show how the interface shear viscosity suppresses the vortex at the interface, generates a uniform flow, and consequently increases the interface compressibility and the Marangoni force on the particle. We mention available experimental data and provide analytical approximations for the drag coefficient that can be used to extract surface viscosities.

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“…2020; Das et al. 2021) and divergence-free interfacial flow (Bławzdziewicz, Cristini & Loewenberg 1999; Fischer, Dhar & Heinig 2006; Desai & Ardekani 2020; Chisholm & Stebe 2021). While such factors dramatically restructure flow around passive colloidal particles at interfaces (Molaei et al.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, interfaces can have complex surface stresses, including surface viscosities and Marangoni stresses owing to surfactant adsorption. These effects are associated with anomalous drag (Fischer 2004;Pozrikidis 2007;Dani et al 2015;Dörr et al 2016;Villa et al 2020;Das et al 2021) and divergence-free interfacial flow (Bławzdziewicz, Cristini & Loewenberg 1999;Fischer, Dhar & Heinig 2006;Desai & Ardekani 2020;. While such factors dramatically restructure flow around passive colloidal particles at interfaces (Molaei et al 2021), their impact on the flow field generated by swimmers is unknown.…”

Section: Introductionmentioning

confidence: 99%

Interfacial flow around a pusher bacterium

Deng,

Molaei,

Chisholm

et al. 2023

J. Fluid Mech.

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Motile bacteria play essential roles in biology that rely on their dynamic behaviours, including their ability to navigate, interact and self-organize. However, bacteria dynamics on fluid interfaces are not well understood. Swimmers adsorbed on fluid interfaces remain highly motile, and fluid interfaces are highly non-ideal domains that alter swimming behaviour. To understand these effects, we study flow fields generated by Pseudomonas aeruginosa PA01 in the pusher mode. Analysis of correlated displacements of tracers and bacteria reveals dipolar flow fields with unexpected asymmetries that differ significantly from their counterparts in bulk fluids. We decompose the flow field into fundamental hydrodynamic modes for swimmers in incompressible fluid interfaces. We find an expected force-doublet mode corresponding to propulsion and drag at the interface plane, and a second dipolar mode, associated with forces exerted by the flagellum on the cell body in the aqueous phase that are countered by Marangoni stresses in the interface. The balance of these modes depends on the bacteria's trapped interfacial configurations. Understanding these flows is broadly important in nature and in the design of biomimetic swimmers.

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Pairwise hydrodynamic interactions of spherical colloids at a gas-liquid interface

Abstract: Abstract

Cited by 7 publications

References 68 publications

Rational Fabrication of Nano-to-Microsphere Polycrystalline Opals Using Slope Self-Assembly

Rational Fabrication of Nano-to-Microsphere Polycrystalline Opals Using Slope Self-Assembly

Drag on a spherical particle at the air–liquid interface: Interplay between compressibility, Marangoni flow, and surface viscosities

Interfacial flow around a pusher bacterium

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