Dynamics of Chemotactic Droplets in Salt Concentration Gradients

Čejková, Jitka; Novák, Matěj; Štěpánek, František; Hanczyc, Martin M.

doi:10.1021/la502624f

Cited by 132 publications

(117 citation statements)

References 22 publications

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“…Chemoattractant released at the exit spreads into the maze, with the local concentration depending on the path distance to the exit. By moving up gradients, swimmers will then prefer the shortest path, as shown in chemotactic experimental systems (11,12) and simulations (45).…”

Section: Chemotactic Maze Solvingmentioning

confidence: 93%

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Chemotaxis and autochemotaxis of self-propelling droplet swimmers

Jin

Krüger

Maaß

2017

Proc. Natl. Acad. Sci. U.S.A.

263

257

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Chemotaxis and autochemotaxis play an important role in many essential biological processes. We present a self-propelling artificial swimmer system that exhibits chemotaxis as well as negative autochemotaxis. Oil droplets in an aqueous surfactant solution are driven by interfacial Marangoni flows induced by micellar solubilization of the oil phase. We demonstrate that chemotaxis along micellar surfactant gradients can guide these swimmers through a microfluidic maze. Similarly, a depletion of empty micelles in the wake of a droplet swimmer causes negative autochemotaxis and thereby trail avoidance. We studied autochemotaxis quantitatively in a microfluidic device of bifurcating channels: Branch choices of consecutive swimmers are anticorrelated, an effect decaying over time due to trail dispersion. We modeled this process by a simple one-dimensional diffusion process and stochastic Langevin dynamics. Our results are consistent with a linear surfactant gradient force and diffusion constants appropriate for micellar diffusion and provide a measure of autochemotactic feedback strength vs. stochastic forces. This assay is readily adaptable for quantitative studies of both artificial and biological autochemotactic systems.artificial swimmers | chemotaxis | autochemotaxis | microfluidics L ocomotion of living bacteria or cells can be random or oriented. Oriented motion comprises the various "taxis" strategies by which bacteria or cells react to changes in their environment (1). Among these, chemotaxis is one of the best-studied examples (2, 3): Cells and microorganisms are able to sense certain chemicals (chemoattractants or chemorepellents) and move toward or away from them. This is an essential function in many biological processes, e.g., wound healing, fertilization, pathogenic species invading a host, or colonization dynamics (4, 5). When the chemoattractant or chemorepellent is produced by the microorganisms themselves, the system exhibits positive or negative autochemotaxis. Thus, chemotaxis provides a mechanism of interindividual communication. Modeling such communication strategies is key to understanding the collective behavior of microorganisms (6-8) as well as flocks of animals like fire ants (9, 10).To model the swimming motion of microorganisms, various self-propelling artificial swimmer systems have been developed based on different mechanisms. Generally, there are two classes of swimmers: systems driven by and aligning with external fields (11-14), including chemotactic gradients, and selfpropelled swimmers, which move autonomously in homogeneous environments (15-21). Many autonomous swimmers additionally react to external fields, e.g., phototactic gradients (22).Biological autochemotactic systems exhibit very complex behaviors (23,24), where physical effects are intermingling with effects from various bioprocesses such as cell migration, metabolism, and division. To untangle these effects, there have been some design proposals for artificial systems, such as in ref.25, and simulations on the dynamics o...

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Section: Chemotactic Maze Solvingmentioning

confidence: 93%

“…Generally, there are two classes of swimmers: systems driven by and aligning with external fields (11)(12)(13)(14), including chemotactic gradients, and selfpropelled swimmers, which move autonomously in homogeneous environments (15)(16)(17)(18)(19)(20)(21). Many autonomous swimmers additionally react to external fields, e.g., phototactic gradients (22).…”

mentioning

confidence: 99%

Chemotaxis and autochemotaxis of self-propelling droplet swimmers

Jin

Krüger

Maaß

2017

Proc. Natl. Acad. Sci. U.S.A.

263

257

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“…Since it is visible to human eye, self-propelled motion of the millimeter-sized oil droplets on the surface of aqueous solutions has been reported by many researchers [24,[29][30][31][32][33][34][35]. Recently, their divisions, fusions, and morphological changes have also been described.…”

Section: Conclusion and Future Remarksmentioning

confidence: 98%

Self-Propelled Motion of Micrometer-Sized Oil Droplets in Aqueous Solution of Surfactant

Banno¹,

Toyota²,

Asakura³

2017

Properties and Uses of Microemulsions

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When an immiscible oil is dispersed in an aqueous solution of a surfactant, emulsions consisting of various-sized oil droplets are generated. Micrometer-sized oil droplets exhibit exotic dynamics such as self-propelled motion in the surfactant solution. Transfer of the surfactant from the aqueous solution phase to the oil droplets through their interface leads to the self-propelled motion in a far-from-equilibrium condition. In this chapter, we demonstrate the observation methods of the self-propelled motion of micrometer-sized oil droplets using phase-contrast, polarized, and fluorescence microscopes and discuss their motion mechanism. Since the generated self-assemblies in micrometer-sized droplet systems are difficult to be identified by spectroscopic methods, the mechanisms of their self-propelled motion have not been clarified. When they are fully understood from nano-to microscale, these findings may be useful to develop not only more stable emulsion systems but also droplet-type analysis systems at the micrometer scale that can carry out reaction, analysis, and detection automatically without the need for an external force.

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“…Chemical and electric potential wave propagation along a dendritic tube of a single cell organism is the most commonly employed setup for identifying the shortest path between two food sources in a biological system [1][2][3]. Finally, in chemical systems a chemical potential gradient created at the beginning of the experiment induces a flow of matter which highlights the shortest path in a maze in a number of distinct ways [8][9][10][11][12][13]. A silver ion gradient initiates the propagation of a chemical wave in the Belousov-Zhabotinsky solution along the paths of a maze with the fastest wave corresponding to the shortest path [8,9].…”

Section: Introductionmentioning

confidence: 99%

Marangoni Flow Driven Maze Solving

Suzuno

Ueyama

Branicki

et al. 2016

Emergence, Complexity and Computation

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Algorithmic approaches to maze solving problems and finding shortest paths are generally NP-hard (Non-deterministic Polynomial-time hard) and thus, at best, computationally expensive. Unconventional computational methods, which often utilize non-local information about the geometry at hand, provide an alternative to solving such problems much more efficiently. In the past few decades several chemical, physical and other methods have been proposed to tackle this issue. In this chapter we discuss a novel chemical method for maze solving which relies on the Marangoni flow induced by a surface tension gradient due to a pH gradient imposed between the entrance and exit of the maze. The solutions of the maze problem are revealed by paths of a passive dye which is transported on the surface of the liquid in the direction of the acidic area, which is chosen to be the exit of the maze. The shortest path is visualized first, as the Marangoni flow advecting the dye particles is the most intense along the shortest path. The longer paths, which also solve the maze, emerge subsequently as they are associated with weaker branches of the chemically-induced Marangoni flow which is key to the proposed method.

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Dynamics of Chemotactic Droplets in Salt Concentration Gradients

Cited by 132 publications

References 22 publications

Chemotaxis and autochemotaxis of self-propelling droplet swimmers

Chemotaxis and autochemotaxis of self-propelling droplet swimmers

Self-Propelled Motion of Micrometer-Sized Oil Droplets in Aqueous Solution of Surfactant

Marangoni Flow Driven Maze Solving

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