Interfacially-adsorbed particles enhance the self-propulsion of oil droplets in aqueous surfactant

Cheon, Seong Ik; Silva, Leonardo Batista Capaverde; Khair, Aditya S.; Zarzar, Lauren D.

doi:10.1039/d0sm02234a

Cited by 32 publications

(51 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The polarization in the concentration of solubilized oil leads to the vertical "pumping" flow for isolated droplets, and sometimes droplet levitation, even for droplets that are not laterally self-propelled. Such results are consistent with simulations of flow for low Péclet number droplets near a wall [17] and have also been experimentally observed previously [10][11] .…”

Section: Resultssupporting

confidence: 92%

“…Our first observations regarding differences between repulsive and attractive droplet interactions were made when using bromo-n-alkane oil droplets of varying carbon number (bromopentane, bromohexane, and bromooctane) stabilized with nonionic nonylphenylethoxylate surfactant, Tergitol NP-12 (hereafter "NP-12", CMC=0.0085 wt%). Bromoalkane droplets sink in aqueous solution lending to ease of experimentation, and they have been shown previously to exhibit solubilization-driven active behavior [10,12] . To prepare polydisperse microscale droplets (~10 to 200 µm diameter), we emulsified 50 microliters of each bromoalkane in 300 microliters of aqueous NP-12 of varying concentration via vortex mixing.…”

Section: Resultsmentioning

confidence: 99%

“…We found that NP-30 is ineffective at micellar solubilization of most oils (Table S1) and only the more water-soluble oils (bromopentane and bromohexane) exhibited flow in NP-30. Iodohexadecane also solubilizes very slowly compared to shorter chain oils [10] (Table S2) and hence was also more likely to exhibit inactivity due to negligible solubilization rate. Thus, while solubilization apparently does not guarantee generation of Marangoni flow, solubilization is still a pre-requisite.…”

Section: Resultsmentioning

confidence: 99%

“…high Péclet number), leading to a feedback process that sustains an interfacial tension gradient at the drop surface [1e, 2, 6] . Solubilizing, motile droplets of many compositions have been demonstrated, including water-in-oil [2] and oil-in-water [5,7] droplets, multiphase droplets [8] , and droplets stabilized by both ionic [7,9] and nonionic [10] surfactants. The chemical gradients produced by solubilization not only generate droplet self-propulsion, but they can also lead to longer-range chemotactic interactions between droplets such as pairwise repulsion [11] , chasing [12] , and multidrop collective dynamics [12][13] .…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Chemically tuning attractive and repulsive interactions between solubilizing oil droplets

Wentworth

Castonguay

Moerman

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Solubilization is a spontaneous transport process occurring in surfactant-stabilized emulsions that can lead to Marangoni flow and droplet motility. Conventionally, active droplets exhibit self-propulsion and pairwise repulsion due to solubilization processes and/or solubilization products raising the droplet’s interfacial tension. Here, we report emulsions with the opposite behavior, wherein solubilization and/or its products decrease the interfacial tension and cause droplets to attract. We systematically characterize the influence of oil structure, nonionic surfactant structure, and surfactant concentration on the interfacial tensions and Marangoni flows of solubilizing oil-in-water drops. Three regimes corresponding to droplet “attraction”, “repulsion” or “inactivity” are identified and the chemical trends leading to these behaviors are discussed. Notably, droplet inactivity, wherein no convective flow is observed, can still occur even when the droplet is solubilizing at appreciable rates. Droplets that are inactive can be induced to become active through doping of the surfactant continuous phase with another oil type. We believe these studies contribute to a new fundamental understanding of solubilization processes in emulsions and provide guidance as to how chemical parameters can be used to influence the dynamics and chemotactic interactions between active droplets.

show abstract

Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Chemically tuning attractive and repulsive interactions between solubilizing oil droplets

Wentworth

Castonguay

Moerman

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Reactivity gradients can be implemented by design and have been studied for systems with built-in asymmetry, for instance by variation of the coating thickness for Janus particles [15,16], in binary systems of interacting particle pairs [17,18], or in droplets with adsorbed colloidal caps [19].…”

Section: Introductionmentioning

confidence: 99%

Interfacial activity dynamics of confined active droplets

Ramesh¹,

Hokmabad²,

Rahalia³

et al. 2022

Preprint

View full text Add to dashboard Cite

Oil droplets in aqueous surfactant solution show spontaneous self-propulsion and dynamics ranging from straight-line to unsteady motion with increasing Péclet number. Recent studies have shown that products of interfacial activity (oil-filled micelles) can lead to multistable higher-mode flow fields and chemorepulsive phenomena. To investigate such chemodynamic effects, we have studied disk-like flattened droplets that are pinned at the top and bottom of the reservoir and produce only pumping flow. With increasing droplet radius we observe the following: (i) vortical structures generated by the droplet migrating around the interface, (ii) bistability between a dipolar and quadrupolar flow mode, and, eventually, (iii) a transition to multipolar modes. For a deeper analysis, we measured flow fields by particle image velocimetry and compared them to a hydrodynamic model based on a Brinkman squirmer. A simultaneous quantification of the flow fields and oil-filled micelle distribution suggests that a local buildup of chemical products leads to a saturation of the surface, which affects the propulsion mechanism. Hence, we describe the interfacial activity dynamics in time and space.

show abstract

Chemically Tuning Attractive and Repulsive Interactions between Solubilizing Oil Droplets

et al. 2022

Self Cite

View full text Add to dashboard Cite

Micellar solubilization is a transport process occurring in surfactant-stabilized emulsions that can lead to Marangoni flow and droplet motility. Active droplets exhibit self-propulsion and pairwise repulsion due to solubilization processes and/or solubilization products raising the droplet's interfacial tension. Here, we report emulsions with the opposite behavior, wherein solubilization decreases the interfacial tension and causes droplets to attract. We characterize the influence of oil chemical structure, nonionic surfactant structure, and surfactant concentration on the interfacial tensions and Marangoni flows of solubilizing oil-in-water drops. Three regimes corresponding to droplet "attraction", "repulsion" or "inactivity" are identified. We believe these studies contribute to a fundamental understanding of solubilization processes in emulsions and provide guidance as to how chemical parameters can influence the dynamics and chemotactic interactions between active droplets.

show abstract

Interfacially-adsorbed particles enhance the self-propulsion of oil droplets in aqueous surfactant

Abstract: Understanding the chemo-mechanical mechanisms that direct the motion of self-propulsive colloids is important for the development of active materials and exploration of dynamic, collective phenomena. Here, we demonstrate that the...

Cited by 32 publications

References 30 publications

Chemically tuning attractive and repulsive interactions between solubilizing oil droplets

Chemically tuning attractive and repulsive interactions between solubilizing oil droplets

Interfacial activity dynamics of confined active droplets

Chemically Tuning Attractive and Repulsive Interactions between Solubilizing Oil Droplets

Contact Info

Product

Resources

About