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  Chemotactic droplet swimmers in complex geometries

Jin, C., Vajdi Hokmabad, B., Baldwin, K. A., & Maass, C. C. (2018). Chemotactic droplet swimmers in complex geometries. Journal of Physics: Condensed Matter, 30(5): 054003. doi:10.1088/1361-648X/aaa208.

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 Creators:
Jin, Chenyu1, Author           
Vajdi Hokmabad, Babak1, Author           
Baldwin, Kyle A.1, Author           
Maass, Corinna C.1, Author           
Affiliations:
1Group Active soft matter, Department of Dynamics of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, Max Planck Society, ou_2063307              

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Free keywords: active emulsions, microfluidics, complex geometries, chemotaxis
 Abstract: Chemotaxis and auto-chemotaxis are key mechanisms in the dynamics of micro-organisms, e.g. in the acquisition of nutrients and in the communication between individuals, influencing the collective behaviour. However, chemical signalling and the natural environment of biological swimmers are generally complex, making them
 hard to access analytically.
 We present a well-controlled, tunable artificial model to study chemotaxis and autochemotaxis in complex geometries, using microfluidic assays of self-propelling oil droplets in an aqueous surfactant solution. Droplets propel via interfacial Marangoni stresses powered by micellar solubilisation. Moreover, filled micelles act as a chemical repellent by diffusive phoretic gradient forces.
 We have studied these chemotactic effects in a series of microfluidic geometries, as published in Jin et al., PNAS 2017:
 First, droplets are guided along the shortest path through a maze by surfactant diffusing into the maze from the exit. Second, we let auto-chemotactic droplet swimmers pass through bifurcating microfluidic channels and record anticorrelations between the branch choices of consecutive droplets. We present an analytical Langevin model matching the experimental data.
 In a previously unpublished experiment, pillar arrays of variable sizes and shapes provide a convex wall interacting with the swimmer and, in the case of attachment, bending its trajectory and forcing it to revert to its own trail. We observe different behaviours based on the interplay of wall curvature and negative autochemotaxis, i. e., no attachment for highly curved interfaces, stable trapping at large pillars, and a narrow transition region where negative autochemotaxis makes the swimmers detach after a single orbit.

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Language(s): eng - English
 Dates: 2018-01-082018-02-07
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1088/1361-648X/aaa208
 Degree: -

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Title: Journal of Physics: Condensed Matter
Source Genre: Journal
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Publ. Info: -
Pages: 11 Volume / Issue: 30 (5) Sequence Number: 054003 Start / End Page: - Identifier: -