Composition-dependent shape changes of self-propelled droplets in a phase-separating system

Ban, Takahiko; Yamada, Tomohiro; Aoyama, Ai; Takagi, Yasunari; Okano, Yasunori

doi:10.1039/c2sm07176b

Cited by 37 publications

(41 citation statements)

References 30 publications

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“…The depicted temporal evolution of γ between 36.5 % w/w PEG solution and different salt solutions depending on C s shows that, γ increased with time for C s > 13 % whereas it remained constant with time for C s = 12 %. From a thermodynamic view, the increase in interfacial tension with time indicates the occurrence of a phase separation of spinodal type and the increase in interfacial energy to generate force (Ban et al 2017). The force originating from such phase separation, which is called Korteweg force, tends to minimize the free energy stored in the interface and can generate convection (Vladimirova, Malagoli & Mauri 1999;Ban et al 2016).…”

Section: Hydrodynamic Properties At Fluid-fluid Interfacementioning

confidence: 99%

Phase separation effects on a partially miscible viscous fingering dynamics

et al. 2020

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Section: Hydrodynamic Properties At Fluid-fluid Interfacementioning

confidence: 99%

Phase separation effects on a partially miscible viscous fingering dynamics

et al. 2020

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“…Emulsion droplets, in contrast, have the potential to be composed of bio-compatible liquids. It was also shown that emulsion droplets can self-propel by Marangoni stresses 10 that are maintained by chemical reactions 11 , micellar solubilization 12,13 , or liquid-liquid phase separations [14][15][16][17][18][19] . However, the realization of self-propelled Janus droplets has been proven difficult [20][21][22][23][24] in spite of the achievements obtained with emulsion droplets.…”

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Spatiotemporal control of cargo delivery performed by programmable self-propelled Janus droplets

Brinkmann

Pagonabarraga

et al. 2018

Commun Phys

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Self-propelled droplets capable of transporting cargo to specific target locations are desired tools for many future applications. Here we propose a class of active droplets with programmable delivery time that are attracted or repelled by certain obstacle geometries. These droplets consist of a water/ethanol mixture and are dispersed in an oil/surfactant solution. Owing to a mass exchange between fluid phases during self-propulsion, the initially homogeneous droplets spontaneously de-mix and evolve into characteristic Janus droplets. Cargo molecules, like DNA, can be separated into the trailing ethanol-rich droplet and are carried to their target location "like in a backpack". The delayed onset of phase separation provides a handle to control the time frame of delivery, while long-ranged hydrodynamic interactions and short-ranged wetting forces are exploited to achieve the desired spatial specificity with respect to obstacle geometry and surface chemistry.

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“…Other studies were concerned with binary liquid mixtures featuring a two-phase region in their phase diagram. In [4,5] the binary system acetone-hexadecane and in [6,7] mixtures of aqueous solutions of poly-(ethylene glycol) (PEG) and sodium sulfate (Na 2 SO 4 ) were studied. However, the droplets driven by phase separation dynamics show only short active periods and their estimated cruising range is typically below 20 times their diameter.…”

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Self-propelled droplets

Seemann

Fleury

Maaß

2016

Eur. Phys. J. Spec. Top.

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Abstract. Self-propelled droplets are a special kind of self-propelled matter that are easily fabricated by standard microfluidic tools and locomote for a certain time without external sources of energy. The typical driving mechanism is a Marangoni flow due to gradients in the interfacial energy on the droplet interface. In this article we review the hydrodynamic prerequisites for self-sustained locomotion and present two examples to realize those conditions for emulsion droplets, i.e. droplets stabilized by a surfactant layer in a surrounding immiscible liquid. One possibility to achieve self-propelled motion relies on chemical reactions affecting the surface active properties of the surfactant molecules. The other relies on micellar solubilization of the droplet phase into the surrounding liquid phase. Remarkable cruising ranges can be achieved in both cases and the relative insensitivity to their own 'exhausts' allows to additionally study collective phenomena.

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Composition-dependent shape changes of self-propelled droplets in a phase-separating system

Cited by 37 publications

References 30 publications

Phase separation effects on a partially miscible viscous fingering dynamics

Phase separation effects on a partially miscible viscous fingering dynamics

Spatiotemporal control of cargo delivery performed by programmable self-propelled Janus droplets

Self-propelled droplets

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