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Published April 3, 2018 | Published + Supplemental Material
Journal Article Open

Instability of expanding bacterial droplets

Abstract

Suspensions of motile bacteria or synthetic microswimmers, termed active matter, manifest a remarkable propensity for self-organization, and formation of large-scale coherent structures. Most active matter research deals with almost homogeneous in space systems and little is known about the dynamics of strongly heterogeneous active matter. Here we report on experimental and theoretical studies on the expansion of highly concentrated bacterial droplets into an ambient bacteria-free fluid. The droplet is formed beneath a rapidly rotating solid macroscopic particle inserted in the suspension. We observe vigorous instability of the droplet reminiscent of a violent explosion. The phenomenon is explained in terms of continuum first-principle theory based on the swim pressure concept. Our findings provide insights into the dynamics of active matter with strong density gradients and significantly expand the scope of experimental and analytic tools for control and manipulation of active systems.

Additional Information

© 2018 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received: 14 June 2017; Accepted: 09 March 2018; Published online: 03 April 2018. Data availability: All data generated and/or analyzed during this study are available from the corresponding author on reasonable request. We thank Prof. Daniel Kearns for providing us the fluorescent strains of Bacillus subtilis. A.S. and I.S.A. were supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering. J.F.B. was supported by the National Science Foundation, CBET 1437570. Author Contributions: A.S., I.S.A., and J.F.B. designed research, L.D.R. and I.S.A. conducted computational modeling and analysis, A.S. performed experiment, A.S., J.F.B., and I.S.A. wrote the paper. The authors declare no competing interests.

Attached Files

Published - s41467-018-03758-z.pdf

Supplemental Material - 41467_2018_3758_MOESM1_ESM.pdf

Supplemental Material - 41467_2018_3758_MOESM2_ESM.mp4

Supplemental Material - 41467_2018_3758_MOESM3_ESM.mp4

Supplemental Material - 41467_2018_3758_MOESM4_ESM.mp4

Supplemental Material - 41467_2018_3758_MOESM5_ESM.avi

Supplemental Material - 41467_2018_3758_MOESM6_ESM.avi

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Additional details

Created:
August 19, 2023
Modified:
October 18, 2023