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Lookup NU author(s): Dr Otti CrozeORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
The experimental characterisation of the swimming statistics of populations of micro-organisms or artificially propelled particles is essential for understanding the physics of active systems and their exploitation. Here, we construct a theoretical framework to extract information on the three- dimensional motion of micro-swimmers from the intermediate scattering function (ISF) obtained from differential dynamic microscopy (DDM). We derive theoretical expressions for the ISF of helical and oscillatory breaststroke swimmers, and test the theoretical framework by applying it to video sequences generated from simulated swimmers with precisely-controlled dynamics. We then discuss how our theory can be applied to the experimental study of helical swimmers, such as active Janus colloids or suspensions of motile microalgae. In particular, we show how fitting DDM data to a simple, non-helical ISF model can be used to derive three-dimensional helical motility parameters, which can therefore be obtained without specialised 3D microscopy equipment. Finally, we discus how our results aid the study of active matter and describe applications of biological and ecological importance.
Author(s): Croze OA, Martinez VA, Jakuszeit T, Dell'Arciprete D, Poon WCK, Bees MA
Publication type: Article
Publication status: Published
Journal: New Journal of Physics
Year: 2019
Volume: 21
Pages: 063012
Print publication date: 11/06/2019
Acceptance date: 23/05/2019
Date deposited: 18/03/2021
ISSN (electronic): 1367-2630
Publisher: Institute of Physics Publishing Ltd.
URL: .https:doi.org/10.1088/1367-2630/ab241f
DOI: 10.1088/1367-2630/ab241f
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