Dario Cortese

University of Exeter

A minimal model of flagellate microswimmers: superhelices, phototaxis and motile gaits

Fluids and Materials Seminar

13th October 2022, 2:00 pm – 3:00 pm
Online, Zoom

Micron-sized unicellular algae are capable of coordinating their flagella to control their swimming behaviour at low Reynolds numbers. In this talk I will discuss a fully-3D singularity model (Re=0) of a biflagellate microswimmer comprising 3 beads, and show how this can be used to link flagellar beat and superhelical motion in the eukaryotic alga Chlamydomonas. Superhelical trajectories require a three-dimensional beat pattern and an asymmetry between the two flagella. The same asymmetry can be exploited to control phototactic response.
The extension of this framework to quadriflagellate microswimmers has been used to investigate the effect of gaits on swimming dynamics, propulsion speed, efficiency, and induced flow patterns. Changing gait alone, distinct motility patterns emerge from the same basic microswimmer design. By comparing the flagella-induced flows, we can further explore the implications of distinct gaits for single-cell dispersal, feeding, and predator-avoidance.
This can be used to suggest that different species of morphologically-similar microorganisms (e.g. with identical number and placement of appendages) evolved distinct flagellar coordination patterns as a consequence of different ecological drivers.

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