We the droplets: A constitutional approach to active and self-propelled emulsions

Birrer, Samuel; Cheon, Seong Ik; Zarzar, Lauren D.

doi:10.1016/j.cocis.2022.101623

Cited by 42 publications

(53 citation statements)

References 104 publications

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“…We further report active self-propulsion of IL droplets, arising due to spontaneously generated Marangoni flow, which has not been previously reported in ILs but is commonly observed in alkanes and haloalkanes. 63,65,66,69,70 Further, we report the discovery of a type of spontaneous emulsification resulting in the development of double and triple emulsions in select ILs in which water is highly soluble, facilitated by surfactants possessing SDS-like chemical structure. Strategies to control the spontaneous formation of double emulsions may prove particularly useful for encapsulation applications.…”

Section: Discussionmentioning

confidence: 94%

“…Imidazolium ILs solubilized at an appreciable rate in all surfactants, while phosphonium ILs generally exhibited little or no measurable solubilization in PF127. In some cases, marked with asterisks (*) in Figure 4, droplets were self-propelled, [63][64][65] which is a property of solubilizing droplets wherein they can move spontaneously due to locally generated interfacial tension gradients and Marangoni flows. To our knowledge, self-propulsion of solubilizing ionic liquid droplets has not been reported before.…”

Section: Ilmentioning

confidence: 99%

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Ionic liquid-in-water emulsions stabilized by molecular and polymeric surfactants

Birrer

Quinnan

Zarzar

2023

Preprint

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Ionic liquids have drawn notable attention for their unique solvent properties and use in applications like batteries and chemical separations. While many ionic liquids are water soluble, there are numerous examples of ionic liquids that are sufficiently hydrophobic to remain phase separated from water. However, relatively little is known about the stability and properties of ionic liquid-in-water emulsions. Here, we survey a series of ionic liquid-in-water emulsions stabilized by a range of ionic and nonionic molecular surfactants and polymers. To assess droplet stability and dynamics, we characterize the ionic liquid-surfactant interfacial tension, describe qualitative coarsening rates, and quantify droplet solubilization rate. In some instances, we observe unexpected spontaneous formation of complex double and triple emulsions. Our observations highlight approaches for ionic liquid emulsion formulation and provide insight into how to address challenges surrounding stabilization of ionic liquid-in-water droplets with molecular surfactants.

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Section: Discussionmentioning

confidence: 94%

Section: Ilmentioning

confidence: 99%

Ionic liquid-in-water emulsions stabilized by molecular and polymeric surfactants

Birrer

Quinnan

Zarzar

2023

Preprint

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“…83 Active droplets are a particular class of droplets that can either self-propel in isolation or do so in response to other neighboring droplets in an emulsion. 84,85 The main physical effect that induces these droplets' motion is the Marangoni effect, where a gradient of surface tension drives mass transport towards areas of higher surface tension. In the case of active droplets, the Marangoni effect is (self-)induced by the droplet itself or by surrounding droplets.…”

Section: Active Dropletsmentioning

confidence: 99%

“…Such gradients of surface energy can be produced optically, e.g., by illuminating the droplet surface and harnessing the thermal or photochemical effects of the light absorbed within the droplet. 2,[85][86][87] For example, lipophilic droplets stabilized by photoresponsive surfactants can move in light gradients. Light irradiation induces the dissociation of photoresponsive surfactants combined with a rapid pH change in the surrounding aqueous phase, which results in fast movement of the droplet away from the light source due to a change in surface tension.…”

Section: Active Dropletsmentioning

confidence: 99%

Light, Matter, Action: Shining light on active matter

Rey¹,

Volpe²,

Volpe³

2023

Preprint

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Light carries energy and momentum. It can therefore alter the motion of objects from atomic to astronomical scales. Being widely available, readily controllable and broadly biocompatible, light is also an ideal tool to propel microscopic particles, drive them out of thermodynamic equilibrium and make them active. Thus, light-driven particles have become a recent focus of research in the field of soft active matter. In this perspective, we discuss recent advances in the control of soft active matter with light, which has mainly been achieved using light intensity. We also highlight some first attempts to utilize light's additional degrees of freedom, such as its wavelength, polarization, and momentum. We then argue that fully exploiting light with all of its properties will play a critical role to increase the level of control over the actuation of active matter as well as the flow of light itself through it. This enabling step will advance the design of soft active matter systems, their functionalities and their transfer towards technological applications.

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“…This kind of control is important in the design and study of artificial and biological microswimmers, their theoretical modelling, experimental realisation, and, ultimately, to provide design principles and dynamic control for technological application. Autophoretic particles [2][3][4][5] and, particularly, their experimental realisation by active droplets [6][7][8][9][10][11][12][13][14][15] are popular active matter models driven by purely physicochemical mechanisms. Generally, their dynamics are characterized by a dimensionless Péclet number Pe, quantifying the ratio of advective and diffusive transport of chemical fuel [16].…”

Section: Introductionmentioning

confidence: 99%

Arrested on heating: controlling the motility of active droplets by temperature

Ramesh¹,

Chen²,

Räder³

et al. 2023

Preprint

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One of the challenges in tailoring the dynamics of active, self-propelling agents lies in arresting and releasing these agents at will. Here, we present an experimental system of active droplets with thermally controllable and reversible states of motion, from unsteady over meandering to persistent to arrested motion. These states depend on the Péclet number of the chemical reaction driving the motion, which we can tune by using a temperature sensitive mixture of surfactants as a fuel medium. We quantify the droplet dynamics by analysing flow and chemical fields for the individual states, comparing them to canonical models for autophoretic particles. In the context of these models, we are able to observe in situ the fundamental first transition between the isotropic, immotile base state and self-propelled motility.

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We the droplets: A constitutional approach to active and self-propelled emulsions

Cited by 42 publications

References 104 publications

Ionic liquid-in-water emulsions stabilized by molecular and polymeric surfactants

Ionic liquid-in-water emulsions stabilized by molecular and polymeric surfactants

Light, Matter, Action: Shining light on active matter

Arrested on heating: controlling the motility of active droplets by temperature

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