Self‐Sustained Marangoni Flows Driven by Chemical Reactions**

Nguindjel, Anne‐Déborah C.; Korevaar, Peter A.

doi:10.1002/syst.202100021

Cited by 15 publications

(6 citation statements)

References 54 publications

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“…In this work, we implement photochemical control over the activity of drain droplets to generate a Marangoni flow and therefore attract these myelin connections (Figure b). Light can be used for contactless manipulation of surface tension gradients, typically by utilizing photoswitchable surfactants or phototriggered reactions that lead to surfactant (de)activation. − Here, we design a system that encompasses the photoactive compounds in droplets, allowing them to function as individually targetable nodes in the UV-controlled network organization. Next, we explore the reconfigurability of the myelin connections among the droplets, as well as their capability to selectively deliver fluorescent dyes at UV-targeted droplets, providing a first step toward communication.…”

Section: Introductionmentioning

confidence: 99%

Reconfigurable Droplet–Droplet Communication Mediated by Photochemical Marangoni Flows

Nguindjel,

Franssen,

Korevaar

2024

J. Am. Chem. Soc.

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Droplets are attractive building blocks for dynamic matter that organizes into adaptive structures. Communication among collectively operating droplets opens untapped potential in settings that vary from sensing, optics, protocells, computing, or adaptive matter. Inspired by the transmission of signals among decentralized units in slime mold Physarum polycephalum, we introduce a combination of surfactants, self-assembly, and photochemistry to establish chemical signal transfer among droplets. To connect droplets that float at an air−water interface, surfactant triethylene glycol monododecylether (C 12 E 3 ) is used for its ability to self-assemble into wires called myelins. We show how the trajectory of these myelins can be directed toward selected photoactive droplets upon UV exposure. To this end, we developed a strategy for photocontrolled Marangoni flow, which comprises (1) the liquid crystalline coating formed at the surface of an oleic acid/sodium oleate (OA/NaO) droplet when in contact with water, (2) a photoacid generator that protonates sodium oleate upon UV exposure and therefore disintegrates the coating, and (3) the surface tension gradient that is generated upon depletion of the surfactant from the air−water interface by the uncoated droplet. Therefore, localized UV exposure of selected OA/ NaO droplets results in attraction of the myelins such that they establish reconfigurable connections that self-organize among the C 12 E 3 and OA/NaO droplets. As an example of communication, we demonstrate how the myelins transfer fluorescent dyes, which are selectively delivered in the droplet interior upon photochemical regulation of the liquid crystalline coating.

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Section: Introductionmentioning

confidence: 99%

Reconfigurable Droplet–Droplet Communication Mediated by Photochemical Marangoni Flows

Nguindjel,

Franssen,

Korevaar

2024

J. Am. Chem. Soc.

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“…Starting off with concentration gradients of surface active molecules at air-liquid interfaces, the Marangoni effect leads to interfacial flow. [14,15] When exposed to an external concentration gradient, floating objects move from low toward high surface tension regions, following the Marangoni flow (Figure 1a). [16,17] Thereby, global surface tension gradients result in a localized accumulation in the high surface tension region.…”

Section: Introductionmentioning

confidence: 99%

Positional information-based morphogenesis of surfactant droplet swarms emerging from competition between local and global Marangoni effects.

de Visser,

Neeleman,

Dankloff

et al. 2024

Preprint

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Positional information is proposed as a key element in morphogenesis, where cells differentiate based on their position in an external morphogen gradient. Here, we demonstrate the position-dependent differentiation of floating surfactant droplets as they self-organize in a pH gradient, using the Marangoni effect to translate gradients of surface-active molecules into motion. We start with a field of surfactant microliter-droplets floating on water, that upon the release of surfactant drive local, outbound Marangoni flows and myelin filament growth. Next, we introduce a competing surfactant based on a hydrolysable amide, which is more surface active than the myelin surfactant and thereby inhibits the local Marangoni flows and myelin growth from the droplets. Upon introducing a pH gradient, the amide surfactant hydrolyses in the acidic region, so that the local Marangoni flows and myelin growth are reestablished. The resulting combination of local and global surface tension gradients produces a region of myelin-growing droplets and a region where myelin-growth is suppressed, separated by a wave front of closely packed droplets – featuring an organization that is reminiscent to the ‘French flag’-patterns emerging from concentration gradients in morphogenesis.

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“…Via the Marangoni effect, sustained motion then manifests as (collective) self‐propulsion of droplets or interfacial flow of liquids. [ 32–38 ] Similarly, collective, [ 39 ] self‐propelled [ 40–43 ] and directed [ 44–47 ] motion has been observed when droplets convert empty micelles into filled ones or are brought out of equilibrium by UV‐irradiation or temperature changes. These concepts have been exploited to achieve functions such as chemo‐ and phototaxis, maze solving, multiphase reactors, collectively moving swarms, and reconfigurable structures.…”

Section: Introductionmentioning

confidence: 99%

“…Via the Marangoni effect, sustained motion then manifests as (collective) self-propulsion of droplets or interfacial flow of liquids. [32][33][34][35][36][37][38] Similarly, collective, [39] self-propelled [40][41][42][43] and directed [44][45][46][47] motion has been observed when droplets convert empty micelles into filled ones or are brought out of equilibrium by UV-irradiation or temperature changes. These concepts have been exploited to achieve functions such as chemo-and phototaxis, maze solving, multiphase reactors, collectively moving swarms, and reconfigurable structures.The out-of-equilibrium phenomena that emerge from concentration gradients, dynamic assemblies, and motile droplets [48][49][50] prompted us to explore a combination of these concepts, using dissipative droplets at an air-water interface that are subject to mechanical forces mediated by self-assembled filaments that tether these droplets.…”

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confidence: 97%

Orbiting Self‐Organization of Filament‐Tethered Surface‐Active Droplets

Winkens¹,

Vilcan²,

Visser³

et al. 2023

Small

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Dissipative chemical systems hold the potential to enable life‐like behavior in synthetic matter, such as self‐organization, motility, and dynamic switching between different states. Here, out‐of‐equilibrium self‐organization is demonstrated by interconnected source and drain droplets at an air‐water interface, which display dynamic behavior due to a hydrolysis reaction that generates a concentration gradient around the drain droplets. This concentration gradient interferes with the adhesion of self‐assembled amphiphile filaments that grow from a source droplet. The chemical gradient sustains a unique orbiting of the drain droplet, which is proposed to be driven by the selective adhesion of the filaments to the front of the moving droplet, while filaments approaching from behind are destabilized upon contact with the hydrolysis product in the trail of the droplet. Potential applications are foreseen in the transfer of chemical signals amongst communicating droplets in rearranging networks, and the implementation of chemical reactions to drive complex positioning routines in life‐like systems.

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Self‐Sustained Marangoni Flows Driven by Chemical Reactions**

Cited by 15 publications

References 54 publications

Reconfigurable Droplet–Droplet Communication Mediated by Photochemical Marangoni Flows

Reconfigurable Droplet–Droplet Communication Mediated by Photochemical Marangoni Flows

Positional information-based morphogenesis of surfactant droplet swarms emerging from competition between local and global Marangoni effects.

Orbiting Self‐Organization of Filament‐Tethered Surface‐Active Droplets

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