The swimming of a deforming helix.
Eur Phys J E Soft Matter
Springer Science and Business Media LLC
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Koens, L. M., Zhang, H., Moeller, M., Mourran, A., & Lauga, E. (2018). The swimming of a deforming helix.. Eur Phys J E Soft Matter, 41 (10), 119. https://doi.org/10.1140/epje/i2018-11728-2
Many microorganisms and artificial microswimmers use helical appendages in order to generate locomotion. Though often rotated so as to produce thrust, some species of bacteria such Spiroplasma, Rhodobacter sphaeroides and Spirochetes induce movement by deforming a helical-shaped body. Recently, artificial devices have been created which also generate motion by deforming their helical body in a non-reciprocal way (A. Mourran et al. Adv. Mater. 29, 1604825, 2017). Inspired by these systems, we investigate the transport of a deforming helix within a viscous fluid. Specifically, we consider a swimmer that maintains a helical centreline and a single handedness while changing its helix radius, pitch and wavelength uniformly across the body. We first discuss how a deforming helix can create a non-reciprocal translational and rotational swimming stroke and identify its principle direction of motion. We then determine the leading-order physics for helices with small helix radius before considering the general behaviour for different configuration parameters and how these swimmers can be optimised. Finally, we explore how the presence of walls, gravity, and defects in the centreline allow the helical device to break symmetries, increase its speed, and generate transport in directions not available to helices in bulk fluids.
Bacteria, Movement, Swimming, Surface Properties, Torque, Models, Biological, Biomechanical Phenomena
This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement 682754 to EL). We also gratefully acknowledge support from the DFG within the priority program SPP 1726 on Microswimmers from Single Particle Motion to Collective Behaviour (AM).
European Research Council (682754)
External DOI: https://doi.org/10.1140/epje/i2018-11728-2
This record's URL: https://www.repository.cam.ac.uk/handle/1810/285500
Attribution 4.0 International
Licence URL: https://creativecommons.org/licenses/by/4.0/